MULTIPART REAGENTS HAVING INCREASED AVIDITY FOR POLYMERASE BINDING

Info

Publication number: 20210373000
Type: Application
Filed: Aug 10, 2021
Publication Date: Dec 2, 2021
Inventors: Sinan ARSLAN (San Diego, CA), Molly HE (San Diego, CA), Matthew KELLINGER (San Diego, CA), Jake LEVIEUX (San Diego, CA), Michael PREVITE (San Diego, CA), Junhua ZHAO (San Diego, CA), Su ZHANG (San Diego, CA), Tyler LOPEZ (San Diego, CA)
Application Number: 17/398,315

Abstract

Multivalent binding compositions including a particle-nucleotide conjugate having a plurality of copies of a nucleotide attached to the particle are described. The multivalent binding compositions allow one to localize detectable signals to active regions of biochemical interaction, e.g., sites of protein-protein interaction, protein-nucleic acid interaction, nucleic acid hybridization, or enzymatic reaction, and can be used to identify sites of base incorporation in elongating nucleic acid chains during polymerase reactions and to provide improved base discrimination for sequencing and array based applications.

Description

Description

CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No. 17/063,608, filed Oct. 5, 2020, which is a continuation-in-part of PCT/US2020/031161, filed May 1, 2020, which is a continuation-in part of U.S. patent application Ser. No. 16/543,351, filed Aug. 16, 2019, which claims the benefit of U.S. Provisional Application No. 62/841,541, filed May 1, 2019; and of U.S. patent application Ser. No. 16/936,121, filed Jul. 22, 2020, which is a continuation of U.S. patent application Ser. No. 16/579,794, filed on Sep. 23, 2019, now U.S. patent Ser. No. 10/768,173, which claims the benefit of U.S. Provisional Application No. 62/897,172 filed on Sep. 6, 2019, each of which is hereby incorporated by reference in its entirety.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Aug. 6, 2021, is named 52933_733_301_SL.txt and is 4,476 bytes in size.

BACKGROUND

This disclosure herein relates to the field of molecular biology, such as compositions, methods, and systems for nucleic acid hybridization and nucleic acid sequencing. In particular, it relates to compositions and methods for nucleic acid hybridization to nucleic acid molecules coupled to a surface and sequencing of those nucleic acid molecules.

Nucleic acid hybridization protocols constitute an important part of many different nucleic acid amplification and analysis techniques. The limited specificity and reaction rates achieved through the use of existing nucleic acid hybridization protocols can have detrimental effects on the throughput and accuracy of downstream nucleic acid analysis methods. Methods of stringency control often involve conditions causing a significant decrease in the number of hybridized complexes. Therefore, there is a need for an improved method to achieve a high stringency of hybridization during the sequencing analysis.

Nucleic acid sequencing can be used to obtain information in a wide variety of biomedical contexts, including diagnostics, prognostics, biotechnology, and forensic biology. Various sequencing methods have been developed including Maxam-Gilbert sequencing and chain-termination methods, or de novo sequencing methods including shotgun sequencing and bridge PCR, or next-generation methods including polony sequencing, 454 pyrosequencing, Illumina sequencing, SOLiD sequencing, Ion Torrent semiconductor sequencing, HeliScope single molecule sequencing, SMRT® sequencing, and others. Despite advances in DNA sequencing, many challenges to cost effective, high throughput sequencing remain unaddressed. The present disclosure provides novel solutions and approaches to addressing many of the shortcomings of existing technologies.

SUMMARY

Provided herein are methods of determining the identity of a nucleotide in a target nucleic acid comprising: (a) providing a composition comprising: (i) a target nucleic acid comprising two or more repeats of an identical sequence; (ii) two or more primer nucleic acids complementary to one or more regions of said target nucleic acid; and (iii) two or more polymerase molecules; (b) contacting said composition with a multivalent binding composition comprising a polymer-nucleotide conjugate under conditions sufficient to allow a binding complex to be formed between said polymer-nucleotide conjugate and the composition of step (a), wherein the polymer-nucleotide conjugate comprises two or more copies of a nucleotide and optionally one or more detectable labels; and (d) detecting said binding complex, thereby establishing the identity of said nucleotide in the target nucleic acid. In some embodiments, the target nucleic acid is DNA. In some embodiments, the detection of the binding complex is performed in the absence of unbound or solution-borne polymer nucleotide conjugates. In some embodiments, the target nucleic acid has been replicated or amplified or has been produced by replication or amplification. In some embodiments, the detectable label is a fluorescent label. In some embodiments, detecting the complex comprises a fluorescence measurement. In some embodiments, the multivalent binding composition comprises one type of polymer-nucleotide conjugate. In some embodiments, the multivalent binding composition comprises two or more types of polymer-nucleotide conjugates. In some embodiments, each type of the two or more types of polymer-nucleotide conjugates comprises a different type of nucleotide. In some embodiments, the multivalent binding composition consists of three types of polymer-nucleotide conjugates and wherein each type of the three types of polymer-nucleotide conjugates comprises a different type of nucleotide. In some embodiments, the binding complex further comprises a blocked nucleotide. In some embodiments, the blocked nucleotide is a 3′-O-azidomethyl, 3′-O-methyl nucleotide, or 3′-O-alkyl hydroxylamine. In some embodiments, said contacting occurs in the presence of an ion that stabilizes said binding complex, said complex comprising a polymer nucleotide conjugate, two or more polymerase molecules, and two or more binding sites within the target nucleic acid. In some embodiments, the contacting is done in the presence of strontium, magnesium, calcium ions, or any combination thereof. In some embodiments, the polymerase molecule is catalytically inactive. In some embodiments, the binding complex has a persistence time of greater than 2 seconds. In some embodiments, methods further comprise hybridizing the two or more primer nucleic acids to the one or more regions of said target nucleic acid by bringing the two or more primer nucleic acids into contact with a hybridizing composition comprising said target nucleic acid at a concentration of 1 nanomolar or less under conditions sufficient for said target nucleic acid to hybridize to the two or more primer nucleic acids in 30 minutes or less. In some embodiments, the two or more primer nucleic acids are coupled to a hydrophilic polymer surface having a water contact angle of less than 45 degrees. In some embodiments, the hybridization composition further comprises: (a) at least one organic solvent having a dielectric constant of no greater than about 115 as measured at 68 degrees Fahrenheit; and (b) a pH buffer. In some embodiments, the hybridization composition further comprises: (a) at least one organic solvent that is polar and aprotic; and (b) a pH buffer.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference in its entirety. In the event of a conflict between a term herein and a term in an incorporated reference, the term herein controls.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

Some novel features of the methods and compositions disclosed herein are set forth in the present disclosure. A better understanding of the features and advantages of the methods and compositions disclosed herein will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the disclosed compositions and methods are utilized, and the accompanying drawings of which:

FIGS. 1A-1B provide non-limiting examples of image data that demonstrate the improvements in hybridization stringency, speed, and efficacy that may be achieved through the reformulation of the hybridization buffer used for solid-phase nucleic acid amplification, as described herein. FIG. 1A provides examples of image data for two different hybridization buffer formulations and protocols. FIG. 1B provides an example of the corresponding image data obtained using a standard hybridization buffer and protocol.

FIG. 2 illustrates a workflow for nucleic acid sequencing using the disclosed hybridization methods on low binding surfaces and non-limiting examples of the processing times that may be achieved.

FIG. 3 shows the surface template hybridization images (NASA results at 100 pM) of the samples corresponding to the compositions used for hybridization.

FIG. 4 shows a table with hybridization design of experiment spot counts.

FIG. 5 shows the post nucleic acid surface amplification PCR images of the samples.

FIG. 6 shows a work flow according to various embodiments disclosed herein.

FIG. 7 shows a work flow for a sequence reaction according to various embodiments described herein.

FIG. 8 shows a sample nucleic acid hybridization workflow according to various embodiments described herein.

FIG. 9A-9B show how sample nucleic acids hybridized to the nucleic acid molecules coupled to the low-non-specific binding surface is visualized (FIG. 9A) or amplified (FIG. 9B) according to various embodiments described herein.

FIG. 10 schematically depicts an example computer control system.

FIG. 11 shows a workflow of purification and isolation of sample nucleic acids from a biological sample, library preparation, and hybridization according to various embodiments described herein.

FIGS. 12A-12H illustrate the steps for sequencing a target nucleic acid utilizing a non-limiting example of a multivalent binding composition: FIG. 12A illustrates non-limiting example 8 of attaching a target nucleic acid to a surface; FIG. 12B illustrates a non-limiting example of clonally amplifying the target nucleic acid to form clusters of amplified target nucleic acid molecules; FIG. 12C illustrates a non-limiting example of priming the target nucleic acid to produce a primed target nucleic acid; FIG. 12D illustrates a non-limiting example of contacting the primed target nucleic acid with the multivalent binding composition and polymerase to form a binding complex; FIG. 12E illustrates a non-limiting example of the images of the binding complex captured on the surface; FIG. 12F illustrates a non-limiting example of extending a primer strand by one nucleotide; FIG. 12G illustrates a non-limiting example of another cycle of contacting the primed target nucleic acid to the multivalent binding composition and polymerase to form a binding complex; and FIG. 12H illustrates non-limiting examples of images of a binding complex captured on the surface in subsequent sequencing cycles.

FIG. 13 shows a flow chart outlining steps for sequencing a target nucleic acid and extending a primer strand through a single base addition according to various embodiments described herein.

FIG. 14 shows a flow chart outlining steps for sequencing a target nucleic acid and extending a primer strand through incorporating the nucleotide on the particle-nucleotide conjugate according to various embodiments described herein.

FIGS. 15A-15B illustrate a non-limiting example of detecting a target nucleic acid using the polymer-nucleotide conjugates. FIG. 15A shows the step of contacting the polymerase and polymer-nucleotide conjugates to some nucleic acid molecules; FIG. 15B shows the binding complex formed between the polymerase, polymer-nucleotide conjugates, and the target nucleic acid molecules.

FIGS. 16A-16C show schematic representations of non-limiting examples of varying configurations of the polymer-nucleotide conjugates: FIG. 16A shows polymer-nucleotide conjugates having various multi-arm configurations; FIG. 16B shows a polymer-nucleotide conjugate having the polymer branch radiating from the center; and FIG. 16C shows polymer-nucleotide conjugates having the binding moiety biotin.

FIG. 17 shows a generalized graphical depiction of the increase in signal intensity that has been observed during binding, persistence, and washing and removal of multivalent substrates.

FIGS. 18A-18J show fluorescence images of the steps in a sequencing reaction using multivalent PEG-substrate compositions. FIG. 18A. shows red and green fluorescent images post exposure of DNA RCA templates (G and A first base) to 500 nM base labeled nucleotides (A-Cy3 and G-Cy5) in exposure buffer containing 20 nM Klenow polymerase and 2.5 mM Sr+2. Images were collected after washing with imaging buffer with the same composition as the exposure buffer but containing no nucleotides or polymerase. Contrast was scaled to maximize visualization of the dimmest signals, but no signals persisted following washing with imaging buffer (FIG. 18A, inset). FIGS. 18B-18 show fluorescence images showing multivalent PEG-nucleotide (base-labeled) ligands PB1 (FIG. 18B), PB2 (FIG. 18C), PB3 (FIG. 18D), and PB5 (FIG. 18E) having an effective nucleotide concentration of 500 nM after mixing in the exposure buffer and imaging in the imaging buffer as described above. FIG. 18F shows fluorescence image showing multivalent PEG-nucleotide (base-labeled) ligand PB5 at 2.5 μM after mixing in the exposure buffer and imaging in the imaging buffer as above. FIGS. 18G-18I show fluorescence images showing further base discrimination by exposure of the multivalent binding composition to inactive mutants of klenow polymerase (FIG. 18G. D882H; FIG. 18H. D882E; FIG. 18I. D882A) vs. the wild type Klenow (control) enzyme (FIG. 18J).

FIGS. 19A-19B show the efficacy of the multivalent reporter compositions in determining the base sequence of a DNA sequence over 5 sequencing cycles: FIG. 19A shows images and expected sequences for templates taken after each sequencing cycle; and FIG. 19B shows aligned sequencing results utilizing the images taken in FIG. 19A.

FIGS. 20A-20G show fluorescence images of multivalent polyethylene glycol (PEG) polymer-nucleotide (base-labeled) conjugates having an effective nucleotide concentration of 500 nM and varying PEG branch length, after contacting to a support surface comprising DNA templates (comprising G or A as the first base; prepared using rolling circle amplification (RCA)) in an exposure buffer comprising 20 nM Klenow polymerase and 2.5 mM Sr+2. Images were acquired after washing with an imaging buffer having the same composition as the exposure buffer but lacking nucleotides and polymerase. Panels show images obtained using multivalent PEG-nucleotide ligands with arm lengths as follows: FIG. 20A: 1K PEG. FIG. 20B: 2K PEG. FIG. 20C: 3K PEG. FIG. 20D: 5K PEG. FIG. 20E: 10K PEG. FIG. 20F: 20K PEG. FIG. 20G shows images obtained using 10K PEG and an inactive klenow polymerase comprising the mutation D882H.

FIG. 21 shows a quantitative representation of the fluorescence intensities in the images shown in FIGS. 20A-20F, separated by color value, with orange trace corresponding to the red label (Cy3 label; A bases) and blue trace corresponding to the green label (Cy5 label; G bases).

FIG. 22 shows normalized fluorescence from multivalent substrates bound to DNA clusters as described for FIGS. 18A-18J, with the substrate complexes formed in the presence (condition B) and absence (condition A) of Triton-X100 (0.016%).

FIGS. 23A-23B show plots of normalized fluorescence intensity measured for multivalent polymer-nucleotide conjugates and free nucleotides. FIG. 23A shows two replicates of a multivalent polymer-nucleotide conjugate bound to DNA clusters (Conditions A and B) vs. binding complexes formed using labeled free nucleotides (Condition C) after 1 minute. FIG. 23B shows the time course of fluorescence from multivalent substrate complexes over the course of 60 min.

DETAILED DESCRIPTION

Disclosed herein are methods, compositions, systems, and kits for nucleic acid hybridization to nucleic acid molecules coupled to a surface. The methods, compositions, systems, and kits described herein are particularly useful for nucleic acid amplification, nucleic acid sequencing, or a combination thereof. The methods, compositions, systems, and kits described herein enable superior nucleic acid hybridization performance. For example, nucleic acid hybridization according to the methods, compositions, systems, and kits described herein can be performed for a fraction of the cost and/or in a fraction of the time as compared to nucleic acid hybridization methods requiring high temperature (e.g., 90 degrees Celsius) incubations, long incubation times (e.g., 1-2 hours), and large amounts of input nucleic acid (e.g., 10 nanomolar). This is accomplished by utilizing optimized hybridization compositions (e.g., buffers, organic solvents) in combination with low non-specific binding surfaces that are hydrophilic.

Nucleic acid hybridization methods requiring high temperature incubations, long incubation times, and large amounts of input nucleic acid are complex, time consuming, and lack the specificity and efficiency needed for cost-effective high throughput applications. At least one reason such nucleic acid hybridization methods lack specificity and efficiency is that the surfaces used are prone to non-specific binding of proteins or nucleic acids, contributing to increased background signal.

The methods, compositions, systems, and kits described herein provide superior hybridization specificity and efficiency of target nucleic acid molecules to surface-bound nucleic acid molecules, as compared to nucleic acid hybridization methods using surfaces prone to non-specific binding reactions. Described herein, are methods and systems utilizing a low non-specific binding surface, thereby reducing background signal. The low non-specific binding surfaces described herein are engineered so that proteins, nucleic acids, and other biomolecules do not “stick” to the substrate of the surface. The low non-specific binding surfaces described herein are hydrophilic. In some instances, the low non-specific binding surfaces have a water contact angle of less than or equal to about 50 degrees.

The methods described herein comprise hybridizing a target nucleic acid to a nucleic acid molecule coupled to a hydrophilic surface (e.g., a low non-specific binding surface) in the presence of the hybridization compositions described herein. The methods described herein are useful for nucleic acid hybridization, amplification, sequencing, or a combination thereof. In some instances, the methods described herein achieve superior hybridization performance on a low non-specific binding surface. In addition, in some instances, the methods described herein achieve a non-specific cyanine dye-3 (Cy3) dye absorption of less than about 0.25 molecules/μm².

Optimized hybridization compositions described herein, for example, when used with low non-specific binding surfaces, enable isothermal hybridization reactions to be performed at 60 degrees Celsius for as few as 2 minutes, using as little as 50 picomolar concentration of input nucleic acid. Methods described herein provide (i) superior hybridization rates, (ii) superior hybridization specificity, (iii) superior hybridization stringency, (iv) superior hybridization efficiency (or yield), (v) reduced requirements for the amount of starting material necessary, (vi) lowered temperature requirements for isothermal or thermal ramping amplification protocols, (vii) increased annealing rates, and (viii) a yield having a low percentage of the total number target nucleic acid molecules (or amplified clusters of target nucleic acid molecules) being associated with the surface without hybridizing to the surface bound nucleic acid, as compared to hybridization reactions using non-specific binding surfaces. The increased performance and reduced cost and time required to perform a hybridization reaction make the methods, compositions, systems, and kits described herein ideally suited for high throughput nucleic acid hybridization, amplification, and sequencing applications.

Hybridization formulations using, for example, saline sodium citrate buffer achieve poor hybridization specificity or efficiency when used with hybridization protocols using the non-specific binding surfaces described herein. The hybridization reaction or annealing interaction between target nucleic acid molecules in the solution and nucleic acid molecules coupled to the low non-specific binding surfaces can be impacted by several factors, including the availability of hydrogen bonding partners in the solution and the polarity of the solution. In general, nucleic acids preferentially inhabit bulk solution where possible in order to take advantage of the additional entropic stabilization presented by the ability to access dynamic states in three, rather than two, dimensions such as would be available on a solid surface. At equilibrium, in a system comprising a nucleic acid, a solution, and a hydrophilic surface (e.g., low non-specific binding surface), a nucleic acid molecule will be preferentially stabilized in solution, rather than in a surface-bound state when the solvent is aqueous.

Hybridization compositions and methods utilizing protic solvents (e.g., saline sodium citrate buffer) are disadvantageous for nucleic acid hybridization reactions with the low non-specific binding surfaces described herein, because aprotic solvents provide a favorable environment for the target nucleic acid molecules to stay in solution, rather than binding to the low non-specific binding surface. This is due to the ability of the protic solvent to provide sufficient hydrogen bonding partners of sufficient size and distribution such that hydrogen bonding interactions between the exposed hydrogen bond donors and acceptors along the nucleic acid backbone, or, any exposed sidechain moieties, occur.

By contrast, the hybridization compositions described herein drive the target nucleic acid molecule to the low non-specific binding surface while in solution, by utilizing an aprotic organic solvent, such as, for example, formamide. The aprotic solvents described herein reduce the proportion of solvent molecules capable of satisfying the hydrogen bonding requirements of the nucleic acid chain, and make it possible to create an entropic penalty in the bulk solution, which will drive the system toward stabilization by depositing the nucleic acid on the surface (e.g., the entropic penalty caused by ordering the bulk solution to accommodate the unbonded hydrogen bonding elements in the nucleic acid becomes greater than the entropic penalty caused by loss of the third dimension of dynamic freedom when the polymer is adsorbed to the surface). Furthermore, introduction of an aprotic organic solvent into the solution may help drive down the entropy and in turn provides a more favorable environment for the nucleic acid to bind to the hydrophilic surface. For example, addition of aprotic solvent acetonitrile helps to drive the nucleic acid in the solution towards a surface bound state.

The hybridization compositions described herein may further comprise concentrations of protic and aprotic organic solvents, in order to prevent precipitation of the target nucleic acid from solution that can be caused by high concentrations of aprotic solvent in the solution. In this manner, hybridization compositions described herein may cause the nucleic acids to selectively associate with hydrophilic surfaces (e.g., low non-specific binding surfaces), while remaining substantially solvated.

The hybridization compositions described herein, may comprise crowding agents, which are capable of modulating interactions of nucleic acids with the bulk solution. In some instances, the hybridization compositions comprise relaxing agents, divalent cations, or intercalating agents, which are capable of modulating the dynamics of the polymer itself and may also modulate the interactions of nucleic acids with surfaces in the presence of partially aprotic bulk solvents. Providing such agents in combination with buffers containing some fraction of aprotic or non-hydrogen-bonding components can, in some instances, provide superior control over the interaction of nucleic acid molecules with hydrophilic surfaces.

Various aspects of the disclosed nucleic acid hybridization methods may be applied to solution-phase or solid-phase nucleic acid hybridization, and also to any other type of nucleic acid amplification, or, analysis applications (e.g., nucleic acid sequencing), or any combination thereof. It shall be understood that different aspects of the disclosed methods, devices, and systems can be appreciated individually, collectively, or in combination with each other.

The methods, compositions, systems, and kits described herein are useful for a wide range of applications beyond those involving nucleic acid-surface interactions, because the same thermodynamic parameters optimized by the methods and compositions described herein govern a number of interactions between polymers and biomolecules, as well as polymer and surface interactions and biomolecule and surface interactions. Thus, the methods compositions, systems and kits described herein may be applied to tune the polarity, or the hydrogen bonding potential, or a combination thereof, of a solvent in other systems involving these interactions.

Solution-based hybridization is the foundation for many solution-based molecular biology and solution-phase DNA manipulation applications, most notably the polymerase chain reaction (PCR) (L. Garibyan and N. Avashia, J. Invest. Dermatol., 2013, 133, e6; Z. Xiao, D. Shangguan, Z. Cao, X. Fang, and W. Tan, 2008, DNA guided drug delivery, Chemistry 14, 1769-75; and F. Wei, C. Chen, L. Zhai, N. Zhang, and X. S. Zhao, 2005, DNA based biosensors, J. Am. Chem. Soc., 127, 5306-5307; and S. Tyagi and F. R. Kramer, Nat. Biotechnol., 1996, 14, 303-308). The diffusion rates in many of these reactions are sufficient to drive efficient hybridization and the formation of a functional double-stranded form, which can be analyzed kinetically as a second order kinetic reaction, whereby the forward reaction of duplex formation is second order and the reverse reaction comprising the dissociation of the duplex structure to form the two single stranded complements (strands A and B) is first order (Han, C., Improvement of the Speed and Sensitivity of DNA Hybridization Using Isotachophoresis, Stanford Thesis. 2015). These reactions may be written as:

$A + B \overset{k_{on}}{\underset{k_{off}}{⇄}} AB$ $\frac{d [AB]}{dt} = k_{on} [A] [B] - k_{off} [AB]$

Various approaches have been deployed to increase not only the speed of the hybridization reaction but also the reaction specificity in the wake of confounding DNA non-complementary fragments. Such approaches include, but are not limited to, the addition of MgCl₂and higher salt concentrations, and lower temperatures to accelerate the reactions (H. Kuhn, V. V Demidov, J. M. Coull, M. J. Fiandaca, B. D. Gildea, and M. D. Frank-Kamenetskii, J. Am. Chem. Soc., 2002, 124, 1097-1103; N. A. Straus and T. I. Bonner, Biochim. Biophys. Acta, Nucleic Acids Protein Synth., 1972, 277, 87-95). The trade-off for accelerated reaction rates is often reaction specificity (J. M. S. Bartlett and D. Stirling, PCR protocols, Humana Press, 2003; W. Rychlik, W. J. Spencer, and R. E. Rhoads, Nucleic Acids Res., 1990, 18). Additional methods are sometimes employed that yield potential improvements of reaction specificity through the use of volume exclusion, or, molecular crowding techniques, or a combination thereof that utilize inert polymers as hybridization buffer additives (R. Wieder and J. G. Wetmur, Biopolymers, 1981, 20, 1537-1547, J. G. Wetmur, Biopolymers, 1975, 14, 2517-2524). In addition, organic solvents have been employed as additives to accelerate hybridization kinetics and maintain reaction specificity (N. Dave and J. Liu, J. Phys. Chem. B, 2010, 114, 15694-15699).

While hybridization improvements in solution may be translated to surface-based hybridization techniques, surface-based hybridization needs have far ranging implications for many critical bioassays, such as gene expression analysis (D. T. Ross, U. Scherf, M. B. Eisen, C. M. Perou, C. Rees, P. Spellman, V. Iyer, S. S. Jeffrey, M. Van de Rijn, M. Waltham, A. Pergamenschikov, J. C. Lee, D. Lashkari, D. Shalon, T. G. Myers, J. N. Weinstein, D. Botstein, and P. O. Brown, Nat. Genet., 2000, 24, 227-235; A. Adomas, G. Heller, A. Olson, J. Osborne, M. Karlsson, J. Nahalkova, L. Van Zyl, R. Sederoff, J. Stenlid, R. Finlay, and F. O. Asiegbu, Tree Physiol., 2008, 28, 885-897; M. Schena, D. Shalon, R. W. Davis, and P. O. Brown, Science, 1995, 270, 467-470), diagnosis of disease (J. Marx, Science, 2000, 289, 1670-1672), genotyping and SNP detection (J. G. Hacia, J. B. Fan, O. Ryder, L. Jin, K. Edgemon, G. Ghandour, R. A. Mayer, B. Sun, L. Hsie, C. M. Robbins, L. C. Brody, D. Wang, E. S. Lander, R. Lipshutz, S. P. Fodor, and F. S. Collins, Nat. Genet., 1999, 22, 164-167), rapid nucleic acid based pathogen screening, next generation sequencing (NGS) and a host of other genomics based applications (M. J. Heller, Annu. Rev. Biomed. Eng., 2002, 4, 129-53). The common necessity of all of these reactions is high reaction specificity in a highly multiplexed solution of target sequences that may range from thousands to billions of different sequences, such that the targets are quickly tethered on a solid surface for subsequent probing, or, amplification, or a combination thereof to enable DNA (or other nucleic acid) interrogation for applications such as sequencing or array-based analysis. The efficiencies of surface-based hybridization reactions were found to be much less than that of in solution reactions, e.g., about an order of magnitude less efficient. A great deal of work has been done in past attempts to create a hybridization method for solid surface that provides high specificity and accelerated hybridization reaction rates (D. Y. Zhang, S. X. Chen, and P. Yin, Nat. Chem., 2012, 4, 208-14).

Disclosed herein are innovative combinations of approaches gleaned from studies of surface- and solution-based hybridization as outlined above, as well as from other fields of study that include DNA hydration and quadruplex studies, which lead to substantial improvements in hybridization kinetics and specificity. The disclosed hybridization compositions provide for highly specific (e.g., >2 orders of magnitude improvement over traditional approaches) and accelerated hybridization (e.g., >1-2 orders of magnitude improvement over traditional approaches) when used with low non-specific binding surfaces for applications such as next generation sequencing (NGS) and other bioassays that require highly specific nucleic acid hybridization in a multiplexed pool comprised of a large number of target sequences.

Hybridization Methods

Provided herein are methods for nucleic acid hybridization between a sample nucleic acid molecule and a capture nucleic acid molecule. Referring to FIG. 11, the sample nucleic acid molecule is isolated and purified from a biological sample obtained from a subject 1110. A library of isolated and purified sample nucleic acid molecules is prepared 1111. The library of sample nucleic acid molecules is hybridized to nucleic acid molecules coupled to a low non-specific binding surface described herein in the presence of a hybridization composition 1112.

Biological Sample. The biological samples disclosed herein may comprise nucleic acid molecules, amino acids, polypeptides, proteins, carbohydrates, fats, or viruses. In an example, a biological sample is a nucleic acid sample including one or more nucleic acid molecules. Exemplary biological samples may include polynucleotides, nucleic acids, oligonucleotides, cell-free nucleic acid (e.g., cell-free DNA (cfDNA)), circulating cell-free nucleic acid, circulating tumor nucleic acid (e.g., circulating tumor DNA (ctDNA)), circulating tumor cell (CTC) nucleic acids, nucleic acid fragments, nucleotides, DNA, RNA, peptide polynucleotides, complementary DNA (cDNA), double stranded DNA (dsDNA), single stranded DNA (ssDNA), plasmid DNA, cosmid DNA, chromosomal DNA, genomic DNA (gDNA), viral DNA, bacterial DNA, mtDNA (mitochondrial DNA), ribosomal RNA, cell-free DNA, cell free fetal DNA (cffDNA), mRNA, rRNA, tRNA, nRNA, siRNA, snRNA, snoRNA, scaRNA, microRNA, dsRNA, viral RNA, and the like.

Any substance that comprises nucleic acid may be the source of the biological sample. The substance may be a fluid, e.g., a biological fluid. A fluidic substance may include, but is not limited to, blood, cord blood, saliva, urine, sweat, serum, semen, vaginal fluid, gastric and digestive fluid, spinal fluid, placental fluid, cavity fluid, ocular fluid, serum, breast milk, lymphatic fluid, or combinations thereof. The substance may be solid, for example, a biological tissue. The substance may comprise normal healthy tissues, diseased tissues, or a mix of healthy and diseased tissues.

Biological samples described herein are obtained from various subjects. A subject may be a living subject or a dead subject. Examples of subjects may include, but are not limited to, humans, mammals, non-human mammals, rodents, amphibians, reptiles, canines, felines, bovines, equines, goats, ovines, hens, avines, mice, rabbits, insects, slugs, microbes, bacteria, parasites, or fish. The subject, in some cases, is a patient who is having, suspected of having, or at a risk of developing a disease or disorder. In some instances, the subject may be a pregnant woman. In some instances, the subject may be a normal healthy pregnant woman. In some instances, the subject may be a pregnant woman who is at a risking of carrying a baby with certain birth defect.

A sample may be obtained from a subject by various approaches. For example, a sample may be obtained from a subject through accessing the circulatory system (e.g., intravenously or intra-arterially via a syringe or other apparatus), collecting a secreted biological sample (e.g., saliva, sputum urine, feces), surgically (e.g., biopsy) acquiring a biological sample (e.g., intra-operative samples, post-surgical samples), swabbing (e.g., buccal swab, oropharyngeal swab), or pipetting.

Biological Sample Processing. The biological sample described herein, in some instances, is processed. Processing comprises filtering a sample, binding a component of the sample that contains an analyte, binding the analyte, stabilizing the analyte, purifying the analyte, or a combination thereof. Non-limiting examples of sample components are cells, viral particles, bacterial particles, exosomes, and nucleosomes. In some instances, blood plasma or serum is isolated from a whole blood sample. In some instances, the whole blood is obtained from venous blood or capillary blood of a subject described herein.

Library Preparation of Sample Nucleic Acids. The sample nucleic acids described herein, in some cases, are converted to a library by labeling the sample nucleic acids with a label, barcode or tag. The library of sample nucleic acids are amplified in some instances, for example, by isothermal amplification. Non-limiting examples of amplification methods include, but are not limited to, loop mediated isothermal amplification (LAMP), nucleic acid sequence based amplification (NASBA), strand displacement amplification (SDA), multiple displacement amplification (MDA), rolling circle amplification (RCA), ligase chain reaction (LCR), helicase dependent amplification (HDA), nicking enzyme amplification reaction (NEAR), recombinase polymerase amplification (RPA), and ramification amplification method (RAM).

In some instances, isothermal amplification is used. In some instances, amplification is isothermal with the exception of an initial heating step before isothermal amplification begins. A number of isothermal amplification methods, each having different considerations and providing different advantages, are known in the art and have been discussed in the literature, e.g., by Zanoli and Spoto, 2013, “Isothermal Amplification Methods for the Detection of Nucleic Acids in Microfluidic Devices,” Biosensors 3: 18-43, and Fakruddin, et al., 2013, “Alternative Methods of Polymerase Chain Reaction (PCR),” Journal of Pharmacy and Bioallied Sciences 5(4): 245-252, each incorporated herein by reference in its entirety.

In some instances, the amplification method is Rolling Circle Amplification (RCA). RCA is an isothermal nucleic acid amplification method which allows amplification of the probe DNA sequences by more than 10⁹-fold at a single temperature, typically about 30° C. Numerous rounds of isothermal enzymatic synthesis are carried out by Ø29 DNA polymerase, which extends a circle-hybridized primer by continuously progressing around the circular DNA probe. In some instances, the amplification reaction is carried out using RCA, at about 28° C. to about 32° C. Suitable methods of RCA are described in U.S. Pat. No. 6,558,928.

In some instances, amplifying comprises targeted amplification. In some instances, amplifying a nucleic acid comprises contacting a nucleic acid with at least one primer having a sequence corresponding to a target chromosome sequence. Amplification may be multiplexed, involving contacting the nucleic acid with multiple sets of primers, wherein each of a first pair in a first set and each of a pair in a second set are all different.

Hybridization. Methods described herein comprise bringing a sample nucleic acid molecule into contact with a capture nucleic acid molecule that is optionally coupled to a low non-specific binding surface in the presence of a hybridization composition described herein. In some cases, the capture nucleic acid molecule is coupled to the low non-specific binding surface and hybridization occurs on the surface. In some cases, the capture nucleic acid molecules are not coupled to the low non-specific binding surface and hybridization occurs in solution. Methods provided herein further comprising hybridizing the sample nucleic acid molecule with the capture nucleic acid molecule.

Methods described herein comprise hybridizing at least a portion of the sample nucleic acid molecule comprising a nucleic acid sequence that is sufficiently complementary to a portion of the capture nucleic acid molecule. The portion of the capture nucleic acid molecule and the sample nucleic acid molecule can be at least or equal to about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nucleotides. The portion of the capture nucleic acid molecule and the sample nucleic acid molecule can be between 4 and 50, 5 and 49, 6 and 48, 7 and 47, 8 and 46, 9 and 45, 10 and 44, 11 and 43, 12 and 42, 13 and 41, 14 and 40, 15 and 39, 16 and 38, 17 and 37, 18 and 36, 19 and 35, 20 and 34, 21 and 33, 22 and 32, 23 and 31, 24 and 30, 25 and 29, 26 and 28 nucleotides. The portion of the capture nucleic acid molecule and the sample nucleic acid molecule can be between 8 and 20 nucleotides. In some instances, at least 90% of the nucleic acids in the portion of the sample nucleic acid molecule and the portion of the capture nucleic acid molecule hybridize completely. In some instances, at least 95% of the nucleic acids in the portion of the sample nucleic acid molecule and the portion of the capture nucleic acid molecule hybridize completely. In some instances, between 95-100% of the nucleic acids in the portion of the sample nucleic acid molecule and the portion of the capture nucleic acid molecule hybridize completely.

A non-limiting example provided in FIG. 8 shows one or more sample nucleic acid molecules 801 to be circularized 802 using ligation (e.g., splint ligation) 802, and introduced to one or more nucleic acid molecules 808 coupled to a hydrophilic substrate 807 of a low non-specific binding surface 806 in the presence of a hybridization composition 805. In this example, the low-non-specific binding surface is submerged in the hybridization composition. In another example, the one or more sample nucleic acid molecules is introduced to the hybridization composition before introduction to the one or more nucleic acid molecules 808 coupled to the hydrophilic substrate 807 of the low non-specific binding surface 806. Hybridization occurs between the sample nucleic acid molecule and the surface-coupled nucleic acid molecule 809.

Sample Nucleic Acids. The one or more sample nucleic acid molecules described herein is derived from a biological sample described herein. The sample nucleic acid molecules may be a deoxyribonucleic acid (DNA) molecule or a ribonucleic acid (RNA) molecule. In some instances, the DNA is selected from cell-free DNA (cfDNA)), circulating cell-free nucleic acid, circulating tumor nucleic acid (e.g., circulating tumor DNA (ctDNA)), circulating tumor cell (CTC) nucleic acids, nucleic acid fragments, nucleotides, DNA, complementary DNA (cDNA), double stranded DNA (dsDNA), single stranded DNA (ssDNA), plasmid DNA, cosmid DNA, chromosomal DNA, genomic DNA (gDNA), viral DNA, bacterial DNA, and mtDNA (mitochondrial DNA). In some instances, the RNA is selected from ribosomal RNA, cell-free DNA, cell free fetal DNA (cffDNA), mRNA, rRNA, tRNA, nRNA, siRNA, snRNA, snoRNA, scaRNA, microRNA, dsRNA, viral RNA, and the like.

Coupling the Capture Nucleic Acids to the Surface. The nucleic acid molecules coupled to the surface (e.g., capture molecules) may be coupled to the surface by a number of suitable options. In some instances, the nucleic acid molecules are coupled to the surface through covalent bonds. In some instances, the nucleic acid molecules are coupled to the surface through noncovalent bonds. In some instances, the nucleic acid molecules are attached to the surface through a bio-interaction. Non-limiting examples of bio-interaction surface chemistry include biotin-streptavidin interactions (or variations thereof), polyhistidine (his) tag—Ni/NTA conjugation chemistries, methoxy ether conjugation chemistries, carboxylate conjugation chemistries, amine conjugation chemistries, NHS esters, maleimides, thiol, epoxy, azide, hydrazide, alkyne, isocyanate, and silane.

Compositions

Provided herein are hybridization compositions. The hybridization compositions of the present disclosure comprise at least one organic solvent, which in some cases is polar and aprotic (e.g., having a dielectric constant of less than or equal to about 115 as measured at 68 degrees F.). The hybridization compositions comprise a pH buffer. Optionally, the hybridization compositions comprise one or more molecular crowding/volume exclusion agents, one or more additives that impact DNA melting temperatures, one or more additives that impact DNA hydration, or any combination thereof. The hybridization compositions described herein can be used with the low non-specific binding surfaces described herein, such as, for example, silicon dioxide coated with low binding polymers (e.g., polyethylene glycol (PEG)), for genotyping or sequencing related technologies. Genotyping and sequencing may be achieved using any or a combination of the following hybridization composition components.

Organic Solvent: An organic solvent is a solvent or solvent system comprising carbon-based or carbon-containing substance capable of dissolving or dispersing other substances. An organic solvent may be miscible or immiscible with water.

Polar Solvent: A polar solvent, as included in the hybridization composition described herein, is a solvent or solvent system comprising one or more molecules characterized by the presence of a permanent dipole moment, e.g., a molecule having a spatially unequal distribution of charge density. A polar solvent may be characterized by a dielectric constant of 20, 25, 30, 35, 40, 45, 50, 55, 60 or higher, or by a value or a range of values incorporating any of the aforementioned values. For example, a polar solvent may have a dielectric constant of higher than 100, higher than 110, higher than 111, or higher than 115. In some cases, the dielectric constant is measured at a temperature of greater than or equal to about 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 150, 200, 250, 300, 350, 400, 450, or 500 degrees Fahrenheit (F). In some cases, the dielectric constant is measured at a temperature of less than or equal to about −20, −25, −30, −35, −40, −45, −50, −55, −60, −65, −70, −75, −80, −85, −90, −95, −100, −150, −200, −250, −300, −350, −400, −450, or −459 degrees F. In some cases, the dielectric constant is measured at a temperature of at 68 degrees F. In some cases, the dielectric constant is measured at a temperature of at 20 degrees F.

A polar solvent as described herein may comprise a polar aprotic solvent. A polar aprotic solvent as described herein may further contain no ionizable hydrogen in the molecule. In addition, polar solvents or polar aprotic solvents may be preferably substituted in the context of the presently disclosed compositions with a strong polarizing functional groups such as nitrile, carbonyl, thiol, lactone, sulfone, sulfite, and carbonate groups so that the underlying solvent molecules have a dipole moment. Polar solvents and polar aprotic solvents can be present in both aliphatic and aromatic or cyclic form. In some embodiments, the polar solvent is acetonitrile.

The organic solvent described herein can have a dielectric constant that is the same as or close to acetonitrile. The dielectric constant of the organic solvent can be in the range of about 20-60, about 25-55, about 25-50, about 25-45, about 25-40, about 30-50, about 30-45, or about 30-40. The dielectric constant of the organic solvent can be greater than or equal to about 20, 25, 30, 35, or 40. The dielectric constant of the organic solvent can be lower than 30, 40, 45, 50, 55, or 60. The dielectric constant of the organic solvent can be about 35, 36, 37, 38, or 39.

Dielectric constant may be measured using a test capacitor. Representative polar aprotic solvents having a dielectric constant between 30 and 120 may be used. Such solvents may particularly include, but are not limited to, acetonitrile, diethylene glycol, N,N-dimethylacetamide, dimethyl formamide, dimethyl sulfoxide, ethylene glycol, formamide, hexamethylphosphoramide, glycerin, methanol, N-methyl-2-pyrrolidinone, nitrobenzene, or nitromethane.

The organic solvent described herein can have a polarity index that is the same as or close to acetonitrile. The polarity index of the organic solvent can be in the range of about 2-9, 2-8, 2-7, 2-6, 3-9, 3-8, 3-7, 3-6, 4-9, 4-8, 4-7, or 4-6. The polarity index of the organic solvent can be greater than, or equal to, about 2, 3, 4, 4.5, 5, 5.5, or 6. The polarity index of the organic solvent can be lower than about 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, or 10. The polarity index of the organic solvent can be about 5.5, 5.6, 5.7, or 5.8.

The Snyder Polarity Index may be calculated according to the methods disclosed in Snyder, L. R., Journal of Chromatography A, 92(2):223-30 (1974), which is incorporated by reference herein in its entirety. Representative polar aprotic solvents having a Snyder polarity index between 6.2 and 7.3 may be used. Such solvents may particularly include, but are not limited to, acetonitrile, dimethyl acetamide, dimethyl formamide, N-methyl pyrrolidone, N,N-dimethyl sulfoxide, methanol, or formamide.

Relative polarity may be determined according to the methods given in Reichardt, C., Solvents and Solvent Effects in Organic Chemistry, 3rd ed., 2003, which is incorporated herein by reference in its entirety, and especially with respect to its disclosure of polarities and methods of determining or assessing the same for solvents and solvent molecules. Polar aprotic solvents having a relative polarity between 0.44 and 0.82 may be used. Such solvents may particularly include, but are not limited to, dimethylsulfoxide, acetonitrile, 3-pentanol, 2-pentanol, 2-butanol, Cyclohexanol, 1-octanol, 2-propanol, 1-heptanol, i-butanol, 1-hexanol, 1-pentanol, acetyl acetone, ethyl acetoacetate, 1-butanol, benzyl alcohol, 1-propanol, 2-aminoethanol, Ethanol, diethylene glycol, methanol, ethylene glycol, glycerin, or formamide.

The Solvent Polarity (ET(30)) may be calculated according to the methods disclosed in Reichardt, C., Molecular Interactions, Volume 3, Ratajczak, H. and Orville, W. J., Eds (1982), which is incorporated by reference herein in its entirety.

Some examples of organic solvents include, but are not limited to, acetonitrile, dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetanilide, N-acetyl pyrrolidone, 4-amino pyridine, benzamide, benzimidazole, 1,2,3-benzotriazole, butadienedioxide, 2,3-butylene carbonate, γ-butyrolactone, caprolactone (epsilon), chloro maleic anhydride, 2-chlorocyclohexanone, chloroethylene carbonate, chloronitromethane, citraconic anhydride, crotonlactone, 5-cyano-2-thiouracil, cyclopropylnitrile, dimethyl sulfate, dimethyl sulfone, 1,3-dimethyl-5-tetrazole, 1,5-dimethyl tetrazole, 1,2-dinitrobenzene, 2,4-dinitrotoluene, dipheynyl sulfone, 1,2-dinitrobenzene, 2,4-dinitrotoluene, dipheynyl sulfone, epsilon-caprolactam, ethanesulfonylchloride, ethyl ethyl phosphinate, N-ethyl tetrazole, ethylene carbonate, ethylene trithiocarbonate, ethylene glycol sulfate, ethylene glycol sulfite, furfural, 2-furonitrile, 2-imidazole, isatin, isoxazole, malononitrile, 4-methoxy benzonitrile, 1-methoxy-2-nitrobenzene, methyl alpha bromo tetronate, 1-methyl imidazole, N-methyl imidazole, 3-methyl isoxazole, N-methyl morpholine-N-oxide, methyl phenyl sulfone, N-methyl pyrrolidinone, methyl sulfolane, methyl-4-toluenesulfonate, 3-nitroaniline, nitrobenzimidazole, 2-nitrofuran, 1-nitroso-2-pyrolidinone, 2-nitrothiophene, 2-oxazolidinone, 9,10-phenanthrenequinone, N-phenyl sydnone, phthalic anhydride, picolinonitrile (2-cyanopyridine), 1,3-propane sultone, β-propiolactone, propylene carbonate, 4H-pyran-4-thione, 4H-pyran-4-one (γ-pyrone), pyridazine, 2-pyrrolidone, saccharin, succinonitrile, sulfanilamide, sulfolane, 2,2,6,6-tetrachlorocyclohexanone, tetrahydrothiapyran oxide, tetramethylene sulfone (sulfolane), thiazole, 2-thiouracil, 3,3,3-trichloro propene, 1,1,2-trichloro propene, 1,2,3-trichloro propene, trimethylene sulfide-dioxide, or trimethylene sulfite.

Polar aprotic solvents having a solvent polarity between 44 and 60 may be used. Such solvents may particularly include, but are not limited to, dimethyl sulfoxide, 2-methoxycarbonylphenol, triethyl phosphite, 3-pentanol, acetonitrile, nitromethane, cyclohexanol, 2-pentanol, 4-methyl-1,3, dioxolan-2-one, propylene carbonate, acrylonitrile, 1-phenylethanol, 1-dodecanol, 2-butanol, 2-methylcyclohexanol, 2,6,dimethylphenol, 2,6-xylenol, 1-decanol, cyclopentanol, dimethyl sulfone, 1-octanoldiethylene glycol mono n-butyl ether, butyl digol, 1-heptanol, 3-phenyl-1-propanol, 1,3-dioxolane-2-one, ethylene carbonate, 1-hexanol, 4-chlorobutyronitrile, 5-methyl-2-isopropylphenol, thymol, 3,5,5-trimethyl-1-hexanol, 3-methyl-1-butanol, isoamyl alcohol, 2-methyl-1-propanol, isobutyl alcohol, 2-(tert-butyl)phenol, 1-pentanol, 2-phenylethanol, 2-methylpentane-2,4-diol, dipropylene glycol, 2-isopropylphenol, 2-n-butoxyethanol, ethylene glycol mono-n-butyl ether, 1-butanol, 2-hydroxymethyl-tetrahydrofuran, tetrahydrofurfuryl alcohol, 2-hydroxymethylfuran, furfuryl alcohol, 1-propanol, 2,4-dimethylphenol, 2,4-xylenol, benzyl alcohol, 2-ethoxyphenol, 2-ethoxyethanol, 1,5-pentanediol, 1-bromo-2-propanol, 2-methyl-5-isopropylphenol, carvacrol, 2-aminoethanol, ethanol, n-methyl acetamide, 3-chloropropionitrile, 2-propen-1-ol, allyl alcohol, 2-methoxy ethanol, 2-methylphenol, o-cresol, 1,3-butanediol, 2-propyn-1-ol, propargyl alcohol, 3-methylphenol, m-cresol, triethylene glycol, diethylene glycol, n-methylformamide, 1,2-propanediol, 1,3-propanediol, 2-chlorophenol, methanol, 1,2-ethanediol, glycol, formamide, 2,2,2-trichloroethanol, 1,2,3-propanetriol, glycerol, 2,2,3,3-tetrafluoro-1-propanol, 2,2,2-trifluoroethanol, 4-n-butylphenol, 4-methylphenol, or p-cresol.

Polar aprotic solvents having a dielectric constant in the range of about 30-115 may be used. Such solvents may particularly include, but are not limited to, dimethyl sulfoxide, 2-methoxycarbonylphenol, triethyl phosphite, 3-pentanol, acetonitrile, nitromethane, cyclohexanol, 2-pentanol, 4-methyl-1,3, dioxolan-2-one, propylene carbonate, acrylonitrile, 1-phenylethanol, 1-dodecanol, 2-butanol, 2-methylcyclohexanol, 2,6,dimethylphenol, 2,6-xylenol, 1-decanol, cyclopentanol, dimethyl sulfone, 1-octanoldiethylene glycol mono n-butyl ether, butyl digol, 1-heptanol, 3-phenyl-1-propanol, 1,3-dioxolane-2-one, ethylene carbonate, 1-hexanol, 4-chlorobutyronitrile, 5-methyl-2-isopropylphenol, thymol, 3,5,5-trimethyl-1-hexanol, 3-methyl-1-butanol, isoamyl alcohol, 2-methyl-1-propanol, isobutyl alcohol, 2-(tert-butyl)phenol, 1-pentanol, 2-phenylethanol, 2-methylpentane-2,4-diol, dipropylene glycol, 2-isopropylphenol, 2-n-butoxyethanol, ethylene glycol mono-n-butyl ether, 1-butanol, 2-hydroxymethyl-tetrahydrofuran, tetrahydrofurfuryl alcohol, 2-hydroxymethylfuran, furfuryl alcohol, 1-propanol, 2,4-dimethylphenol, 2,4-xylenol, benzyl alcohol, 2-ethoxyphenol, 2-ethoxyethanol, 1,5-pentanediol, 1-bromo-2-propanol, 2-methyl-5-isopropylphenol, carvacrol, 2-aminoethanol, ethanol, n-methylacetamide, 3-chloropropionitrile, 2-propen-1-ol, allyl alcohol, 2-methoxyethanol, 2-methylphenol, o-cresol, 1,3-butanediol, 2-propyn-1-ol, propargyl alcohol, 3-methylphenol, m-cresol, triethylene glycol, diethylene glycol, n-methylformamide, 1,2-propanediol, 1,3-propanediol, 2-chlorophenol, methanol, 1,2-ethanediol, glycol, formamide, 2,2,2-trichloroethanol, 1,2,3-propanetriol, glycerol, 2,2,3,3-tetrafluoro-1-propanol, 2,2,2-trifluoroethanol, 4-n-butylphenol, 4-methylphenol, or p-cresol.

Organic solvent addition: In some instances, the disclosed hybridization buffer formulations include the addition of an organic solvent. Examples of suitable solvents include, but are not limited to, acetonitrile, ethanol, DMF, and methanol, or any combination thereof at varying percentages (for example >5%). In some instances, the percentage of organic solvent (by volume) included in the hybridization buffer may range from about 1% to about 20%. In some instances, the percentage by volume of organic solvent may be at least 1%, at least 2%, at least 3%, at least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, at least 10%, at least 15%, or at least 20%. In some instances, the percentage by volume of organic solvent may be at most 20%, at most 15%, at most 10%, at most 9%, at most 8%, at most 7%, at most 6%, at most 5%, at most 4%, at most 3%, at most 2%, or at most 1%. Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure, for example, the percentage by volume of organic solvent may range from about 4% to about 15%. The percentage by volume of organic solvent may have any value within this range, e.g., about 7.5%.

When the organic solvent comprises a polar aprotic solvent, the amount of the polar aprotic solvent is present in an amount effective to denature a double stranded nucleic acid. In some instances, the amount of the polar aprotic solvent is greater than, or equal to, about 10% by volume based on the total volume of the formulation. In some instances, the amount of the polar aprotic solvent is about, or more than about, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, 90%, or higher, by volume based on the total volume of the formulation. In some instances, the amount of the polar aprotic solvent is lower than about 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, 90%, or higher, by volume based on the total volume of the formulation. In some embodiments, the amount of the polar aprotic solvent is in the range of about 10% to 90% by volume based on the total volume of the formulation. In some instances, the amount of the polar aprotic solvent is in the range of about 25% to 75% by volume based on the total volume of the formulation. In some instances, the amount of the polar aprotic solvent is in the range of about 10% to 95%, 10% to 85%, 20% to 90%, 20% to 80%, 20% to 75%, or 30% to 60% by volume based on the total volume of the formulation. In some instances, the polar aprotic solvent is formamide.

When the organic solvent comprises a polar aprotic solvent, the amount of the aprotic solvent is present in an amount effective to denature a double stranded nucleic acid. In some instances, the amount of the aprotic solvent is greater than, or equal to, about 10% by volume based on the total volume of the formulation. In some instances, the amount of the aprotic solvent is about, or more than about, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, 90%, or higher, by volume based on the total volume of the formulation. In some instances, the amount of the aprotic solvent is lower than about 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, 90%, or higher, by volume based on the total volume of the formulation. In some instances, the amount of the aprotic solvent is in the range of about 10% to 90% by volume based on the total volume of the formulation. In some instances, the amount of the aprotic solvent is in the range of about 25% to 75% by volume based on the total volume of the formulation. In some instances, the amount of the aprotic solvent is in the range of about 10% to 95%, 10% to 85%, 20% to 90%, 20% to 80%, 20% to 75%, or 30% to 60% by volume based on the total volume of the formulation.

Addition of molecular crowding/volume exclusion agents: The composition described herein can include one or more crowding agents that enhances molecular crowding. In some instances, the crowding agent is selected from the group consisting of polyethylene glycol (PEG), dextran, hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC), hydroxybutyl methyl cellulose, hydroxypropyl cellulose, methylcellulose, and hydroxyl methyl cellulose, and combinations thereof. An example crowding agent may comprise one or more of polyethylene glycol (PEG), dextran, proteins, for example, ovalbumin or hemoglobin, or Ficoll.

A suitable amount of a crowding agent in the composition allows for, enhances, or facilitates molecular crowding. In some instances, the amount of the crowding agent is about, or more than about, 1%, 2%, 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, or higher, by volume based on the total volume of the formulation. In some instances, the amount of the molecular crowding agent is greater than or equal to about 5% by volume based on the total volume of the formulation. In some instances, the amount of the crowding agent is lower than about 3%, 5%, 10%, 12.5%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, 90%, or higher, by volume based on the total volume of the formulation. In some instances, the amount of the molecular crowding agent is less than or equal to about 30% by volume based on the total volume of the formulation. In some instances, the amount of the organic solvent is in the range of about 25% to 75% by volume based on the total volume of the formulation. In some instances, the amount of the organic solvent is in the range of about 1% to 40%, 1% to 35%, 2% to 50%, 2% to 40%, 2% to 35%, 2% to 30%, 2% to 25%, 2% to 20%, 2% to 10%, 5% to 50%, 5% to 40%, 5% to 35%, 5% to 30%, 5% to 25%, or 5% to 20% by volume based on the total volume of the formulation. In some instances, the amount of the molecular crowding agent is in the range of about 5% to about 20% by volume based on the total volume of the formulation. In some instances, the amount of the crowding agent is in the range of about 1% to 30% by volume based on the total volume of the formulation.

One example of the crowding agent in the composition is polyethylene glycol (PEG). In some instances, the PEG used can have a molecular weight sufficient to enhance or facilitate molecular crowding. In some instances, the PEG used in the composition has a molecular weight in the range of about 5 k-50 k Da. In some instances, the PEG used in the composition has a molecular weight in the range of about 10 k-40 k Da. In some instances, the PEG used in the composition has a molecular weight in the range of about 10 k-30 k Da. In some instances, the PEG used in the composition has a molecular weight in the range of about 20 k Da.

In some instances, the disclosed hybridization buffer formulations may include the addition of a molecular crowding or volume exclusion agent. Molecular crowding or volume exclusion agents are, for example, macromolecules (e.g., proteins) which, when added to a solution in high concentrations, may alter the properties of other molecules in solution by reducing the volume of solvent available to the other molecules. In some instances, the percentage by volume of the molecular crowding or volume exclusion agent included in the hybridization buffer formulation may range from about 1% to about 50%. In some instances, the percentage by volume of the molecular crowding or volume exclusion agent may be at least 1%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, or at least 50%. In some instances, the percentage by volume of the molecular crowding or volume exclusion agent may be at most 50%, at most 45%, at most 40%, at most 35%, at most 30%, at most 25%, at most 20%, at most 15%, at most 10%, at most 5%, or at most 1%. Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure, for example, the percentage by volume of molecular crowding or volume exclusion agent may range from about 5% to about 35%. The percentage by volume of molecular crowding or volume exclusion agent may have any value within this range, e.g., about 12.5%.

PH buffer system: The compositions described herein include a pH buffer system that maintains the pH of the compositions in a range suitable for hybridization process. The pH buffer system can include one or more buffering agents selected from the group consisting of Tris, HEPES, TAPS, Tricine, Bicine, Bis-Tris, NaOH, KOH, TES, EPPS, MES, and MOPS. The pH buffer system can further include a solvent. An example pH buffer system includes MOPS, IVIES, TAPS, phosphate buffer combined with methanol, acetonitrile, ethanol, isopropanol, butanol, t-butyl alcohol, DMF, DMSO, or any combination therein.

The amount of the pH buffer system is effective to maintain the pH of the formulation in a range suitable for hybridization. In some instances, the pH may be at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, or at least 10. In some instances, the pH may be at most 10, at most 9, at most 8, at most 7, at most 6, at most 5, at most 4, or at most 3. Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure, for example, the pH of the hybridization buffer may range from about 4 to about 8. The pH of the hybridization buffer may have any value within this range, e.g., about pH 7.8. In some cases, the pH range is about 3 to about 10. In some instances, the disclosed hybridization buffer formulations may include adjustment of pH over the range of about pH 3 to pH 10, with a narrower buffer range of 5-9.

Additives that impact DNA melting temperatures: The compositions described herein can include one or more additives to allow for better control of the melting temperature of the nucleic acid and enhance the stringency control of the hybridization reaction. Hybridization reactions are usually carried out under stringent conditions in order to achieve hybridization specificity. In some cases, the additive for controlling melting temperature of nucleic acid is formamide.

The amount of the additive for controlling melting temperature of nucleic acid can vary depending on other agents used in the compositions. In some instances, the amount of the additive for controlling melting temperature of the nucleic acid is about, or more than about, 1%, 2%, 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, or higher by volume based on the total volume of the formulation. In some instances, the amount of the additive for controlling the melting temperature of the nucleic acid is greater than or equal to about 2% by volume based on the total volume of the formulation. In some instances, the amount of the additive for controlling the melting temperature of the nucleic acid is greater than or equal to about 5% by volume based on the total volume of the formulation. In some instances, the amount of the additive for controlling the melting temperature of the nucleic acid is lower than about 3%, 5%, 10%, 12.5%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, 90%, or higher, by volume based on the total volume of the formulation. In some instances, the amount of the additive for controlling the melting temperature of the nucleic acid is in the range of about 1% to 40%, 1% to 35%, 2% to 50%, 2% to 40%, 2% to 35%, 2% to 30%, 2% to 25%, 2% to 20%, 2% to 10%, 5% to 50%, 5% to 40%, 5% to 35%, 5% to 30%, 5% to 25%, or 5% to 20% by volume based on the total volume of the formulation. In some instances, the amount of the additive for controlling melting temperature of the nucleic acid is in the range of about 2% to 20% by volume based on the total volume of the formulation. In some instances, the amount of the additive for controlling melting temperature of the nucleic acid is in the range of about 5% to 10% by volume based on the total volume of the formulation.

In some instances, the disclosed hybridization buffer formulations may include the addition of an additive that alters nucleic acid duplex melting temperature. Examples of suitable additives that may be used to alter nucleic acid melting temperature include, but are not limited to, formamide. In some instances, the percentage by volume of a melting temperature additive included in the hybridization buffer formulation may range from about 1% to about 50%. In some instances, the percentage by volume of a melting temperature additive may be at least 1%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, or at least 50%. In some instances, the percentage by volume of a melting temperature additive may be at most 50%, at most 45%, at most 40%, at most 35%, at most 30%, at most 25%, at most 20%, at most 15%, at most 10%, at most 5%, or at most 1%. Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure, for example, the percentage by volume of a melting temperature additive may range from about 10% to about 25%. The percentage by volume of a melting temperature additive may have any value within this range, e.g., about 22.5%.

Additives that impact DNA hydration: In some instances, the disclosed hybridization buffer formulations include the addition of an additive that impacts nucleic acid hydration. Examples include, but are not limited to, betaine, urea, glycine betaine, or any combination thereof. In some instances, the percentage by volume of a hydration additive included in the hybridization buffer formulation ranges from about 1% to about 50%. In some instances, the percentage by volume of a hydration additive is at least 1%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, or at least 50%. In some instances, the percentage by volume of a hydration additive is at most 50%, at most 45%, at most 40%, at most 35%, at most 30%, at most 25%, at most 20%, at most 15%, at most 10%, at most 5%, or at most 1%. Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure. For example, the percentage by volume of a hydration additive may range from about 1% to about 30%. The percentage by volume of a melting temperature additive may have any value within this range, e.g., about 6.5%.

Systems

Provided herein are systems comprising the hybridization compositions described herein and a low non-specific binding surface. The systems described herein, in some instances, comprise a flow cell device. The systems described herein further comprise, in some instances, an imaging system (e.g., a camera and an inverted fluorescent microscope). Systems may further comprise one or more computer control systems to perform computer-implemented methods of nucleic acid analysis.

Low non-specific binding surface: Disclosed herein is a low non-specific binding surface that enables improved nucleic acid hybridization and amplification performance. The disclosed surface may comprise one or more layers of covalently or non-covalently attached low-binding chemical modification layers, e.g., silane layers or polymer films, and one or more covalently or non-covalently attached primer sequences that may be used for tethering single-stranded template oligonucleotides to the surface. In some instances, the formulation of the surface, e.g., the chemical composition of the one or more layers, the coupling chemistry used to cross-link the one or more layers to the surface, or, to each other or a combination thereof, and the total number of layers, may be varied such that non-specific binding of proteins, nucleic acid molecules, and other hybridization and amplification reaction components to the surface is minimized or reduced relative to a comparable monolayer. The formulation of the surface may be varied such that non-specific hybridization on the surface is minimized or reduced relative to a comparable monolayer. The formulation of the surface may be varied such that non-specific amplification on the surface is minimized or reduced relative to a comparable monolayer. The formulation of the surface may be varied such that specific amplification rates, or, yields, or a combination thereof on the surface are maximized. Amplification levels suitable for detection are achieved in no more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, or 30 amplification cycles in some cases disclosed herein.

Non-limiting examples of low non-specific binding surfaces are provided in co-pending U.S. patent application Ser. No. 16/739,007, which is hereby incorporated by reference in its entirety. The terms, “low non-specific binding surface” and “low binding surface” are used interchangeably to refer to hydrophilic surfaces that exhibit a low amount of non-specific binding to proteins or nucleic acids, as compared with a surface that is not hydrophilic. In some instances, the low non-specific binding surface is passivated, meaning it is coated with a substrate that is hydrophilic.

Examples of materials from which the substrate or support structure may be fabricated include, but are not limited to, glass, fused-silica, silicon, a polymer (e.g., polystyrene (PS), macroporous polystyrene (MPPS), polymethylmethacrylate (PMMA), polycarbonate (PC), polypropylene (PP), polyethylene (PE), high density polyethylene (HDPE), cyclic olefin polymers (COP), cyclic olefin copolymers (COC), polyethylene terephthalate (PET)), or any combination thereof. Various compositions of both glass and plastic substrates are contemplated.

The substrate or support structure may be rendered in any of a variety of geometries and dimensions, and may comprise any of a variety of materials. For example, in some instances, the substrate or support structure is locally planar (e.g., comprising a microscope slide or the surface of a microscope slide). Globally, the substrate or support structure may be cylindrical (e.g., comprising a capillary or the interior surface of a capillary), spherical (e.g., comprising the outer surface of a non-porous bead), or irregular (e.g., comprising the outer surface of an irregularly-shaped, non-porous bead or particle). In some instances, the surface of the substrate or support structure used for nucleic acid hybridization and amplification may be a solid, non-porous surface. In some instances, the surface of the substrate or support structure used for nucleic acid hybridization and amplification may be porous, such that the coatings described herein penetrate the porous surface, and nucleic acid hybridization and amplification reactions performed thereon may occur within the pores.

The substrate or support structure that comprises the one or more chemically-modified layers, e.g., layers of a low non-specific binding polymer, may be independent or integrated into another structure or assembly. For example, in some instances, the substrate or support structure comprises one or more surfaces within an integrated or assembled microfluidic flow cell. The substrate or support structure may comprise one or more surfaces within a microplate format, e.g., the bottom surface of the wells in a microplate. As noted above, in some instances, the substrate or support structure comprises the interior surface (such as the lumen surface) of a capillary. In another example, the substrate or support structure comprises the interior surface (such as the lumen surface) of a capillary etched into a planar chip.

The chemical modification layers may be applied uniformly across the surface of the substrate or support structure. In another example, the surface of the substrate or support structure may be non-uniformly distributed or patterned, such that the chemical modification layers are confined to one or more discrete regions of the substrate. For example, the substrate surface may be patterned using photolithographic techniques to create an ordered array or random pattern of chemically-modified regions on the surface. The substrate surface may be patterned using contact printing, or, ink-jet printing techniques, or a combination thereof. In some instances, an ordered array or random patter of chemically-modified discrete regions may comprise at least 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, or 10,000 or more discrete regions, or any intermediate number spanned by the range herein.

In order to achieve low non-specific binding surfaces (also referred to herein as “low binding” or “passivated” surfaces), hydrophilic polymers may be non-specifically adsorbed or covalently grafted to the substrate or support surface. For example, passivation can be performed utilizing poly(ethylene glycol) (PEG, also known as polyethylene oxide (PEO) or polyoxyethylene), poly(vinyl alcohol) (PVA), poly(vinyl pyridine), poly(vinyl pyrrolidone) (PVP), poly(acrylic acid) (PAA), polyacrylamide, poly(N-isopropylacrylamide) (PNIPAM), poly(methyl methacrylate) (PMA), poly(2-hydroxylethyl methacrylate) (PHEMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), polyglutamic acid (PGA), poly-lysine, poly-glucoside, streptavidin, dextran, or other hydrophilic polymers with different molecular weights and end groups that are linked to a surface using, for example, silane chemistry. The end groups distal from the surface can include, but are not limited to, biotin, methoxy ether, carboxylate, amine, NHS ester, maleimide, and bis-silane. In some instances, two or more layers of a hydrophilic polymer, e.g., a linear polymer, branched polymer, or multi-branched polymer, may be deposited on the surface. In some instances, two or more layers may be covalently coupled to each other or internally cross-linked to improve the stability of the resulting surface. In some instances, oligonucleotide primers with different base sequences and base modifications (or other biomolecules, e.g., enzymes or antibodies) may be tethered to the resulting surface layer at various surface densities. In some instances, for example, both surface functional group density and oligonucleotide concentration may be varied to target a certain primer density range. Additionally, primer density can be controlled by diluting the oligonucleotides with other molecules that carry the same functional group. For example, amine-labeled oligonucleotides can be diluted with amine-labeled polyethylene glycol in a reaction with an NETS-ester coated surface to reduce the final primer density. Primers with different lengths of linker between the hybridization region and the surface attachment functional group can also be applied to control surface density. Examples of suitable linkers include poly-T and poly-A strands at the 5′ end of the primer (e.g., 0 to 20 bases), PEG linkers (e.g., 3 to 20 monomer units), and carbon-chains (e.g., C6, C12, C18, etc.). To measure the primer density, fluorescently-labeled primers may be tethered to the surface and a fluorescence reading corresponding to the fluorescently-labeled primers may then be compared with that for a dye solution of known concentration.

As a result of the surface passivation techniques disclosed herein, proteins, nucleic acids, and other biomolecules do not “stick” to substrates, that is, they exhibit low non-specific binding (non-specific binding). Examples are shown below using standard monolayer surface preparations with varying glass preparation conditions. Hydrophilic surfaces that have been passivated to achieve ultra-low non-specific binding for proteins and nucleic acids require novel reaction conditions to improve primer deposition reaction efficiencies and hybridization performance, and to induce effective amplification. All of these processes require oligonucleotide attachment and subsequent protein binding and delivery to a low binding surface. As described below, the combination of a new primer surface conjugation formulation (Cy3 oligonucleotide graft titration) and resulting ultra-low non-specific background (non-specific binding functional tests performed using red and green fluorescent dyes) yielded results that demonstrate the viability of the disclosed approaches. Some surfaces disclosed herein exhibit a ratio of specific (e.g., hybridization to a tethered primer or probe) to non-specific binding (e.g., B_inter) of a fluorophore such as Cy3 of at least 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 25:1, 30:1, 35:1, 40:1, 50:1, 75:1, 100:1, or greater than 100:1, or any intermediate value spanned by the range herein. Some surfaces disclosed herein exhibit a ratio of specific to non-specific fluorescence signal (e.g., for specifically-hybridized to non-specifically bound labeled oligonucleotides, or for specifically-amplified to non-specifically-bound (B_inter) or non-specifically amplified (B_intra) labeled oligonucleotides or a combination thereof (B_inter+B_intra)) for a fluorophore such as Cy3 of at least 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 25:1, 30:1, 35:1, 40:1, 50:1, 75:1, 100:1, or greater than 100:1, or any intermediate value spanned by the range herein.

In order to scale primer surface density and add additional dimensionality to hydrophilic or amphoteric surfaces, substrates comprising multi-layer coatings of PEG and other hydrophilic polymers have been developed. By using hydrophilic and amphoteric surface layering approaches that include, but are not limited to, the polymer/co-polymer materials described below, it is possible to increase primer loading density on the surface significantly. Traditional PEG coating approaches use monolayer primer deposition, which has been generally reported as successful for single molecule applications, but does not yield high copy numbers for nucleic acid amplification applications. As described herein, “layering” can be accomplished using traditional crosslinking approaches with any compatible polymer or monomer subunits, such that a surface comprising two or more highly crosslinked layers can be built sequentially. Examples of suitable polymers include, but are not limited to, streptavidin, poly acrylamide, polyester, dextran, poly-lysine, and copolymers of poly-lysine and PEG. In some instances, the different layers may be attached to each other through any of a variety of conjugation reactions including, but not limited to, biotin-streptavidin binding, azide-alkyne click reaction, amine-NETS ester reaction, thiol-maleimide reaction, and ionic interactions between positively charged polymers and negatively charged polymers. In some instances, high primer density materials may be constructed in solution and subsequently layered onto the surface in multiple operations.

The attachment chemistry used to graft a first chemically-modified layer to a support surface will generally be dependent on both the material from which the support is fabricated and the chemical nature of the layer. In some instances, the first layer may be covalently attached to the support surface. In some instances, the first layer may be non-covalently attached, e.g., adsorbed to the surface through non-covalent interactions such as electrostatic interactions, hydrogen bonding, or van der Waals interactions between the surface and the molecular components of the first layer. In either case, the substrate surface may be treated prior to attachment or deposition of the first layer. Any of a variety of surface preparation techniques may be used to clean or treat the support surface. For example, glass or silicon surfaces may be acid-washed using a Piranha solution (a mixture of sulfuric acid (H₂SO₄) and hydrogen peroxide (H₂O₂)), or, cleaned using an oxygen plasma treatment method, or a combination thereof.

Silane chemistries constitute one non-limiting approach for covalently modifying the silanol groups on glass or silicon surfaces to attach more reactive functional groups (e.g., amines or carboxyl groups), which may then be used in coupling linker molecules (e.g., linear hydrocarbon molecules of various lengths, such as C6, C12, C18 hydrocarbons, or linear polyethylene glycol (PEG) molecules) or layer molecules (e.g., branched PEG molecules or other polymers) to the surface. Examples of suitable silanes that may be used in creating any of the disclosed low binding support surfaces include, but are not limited to, (3-Aminopropyl) trimethoxysilane (APTMS), (3-Aminopropyl) triethoxysilane (APTES), any of a variety of PEG-silanes (e.g., comprising molecular weights of 1K, 2K, 5K, 10K, 20K, etc.), amino-PEG silane (e.g., comprising a free amino functional group), maleimide-PEG silane, biotin-PEG silane, and the like.

Any of a variety of molecules including, but not limited to, amino acids, peptides, nucleotides, oligonucleotides, other monomers or polymers, or combinations thereof may be used in creating the one or more chemically-modified layers on the support surface, where the choice of components used may be varied to alter one or more properties of the support surface, e.g., the surface density of functional groups, or, tethered oligonucleotide primers, or a combination thereof; the hydrophilicity/hydrophobicity of the support surface, or the three three-dimensional nature (e.g., “thickness”) of the support surface. Examples of polymers that may be used to create one or more layers of low non-specific binding material in any of the disclosed support surfaces include, but are not limited to, polyethylene glycol (PEG) of various molecular weights and branching structures, streptavidin, polyacrylamide, polyester, dextran, poly-lysine, and poly-lysine copolymers, or any combination thereof. Examples of conjugation chemistries that may be used to graft one or more layers of material (e.g., polymer layers) to the support surface, or, to cross-link the layers to each other, or a combination thereof include, but are not limited to, biotin-streptavidin interactions (or variations thereof), his tag—Ni/NTA conjugation chemistries, methoxy ether conjugation chemistries, carboxylate conjugation chemistries, amine conjugation chemistries, NHS esters, maleimides, thiol, epoxy, azide, hydrazide, alkyne, isocyanate, and silane.

One or more layers of a multi-layered surface may comprise a branched polymer or may be linear. Examples of suitable branched polymers include, but are not limited to, branched PEG, branched poly(vinyl alcohol) (branched PVA), branched poly(vinyl pyridine), branched poly(vinyl pyrrolidone) (branched PVP), branched), poly(acrylic acid) (branched PAA), branched polyacrylamide, branched poly(N-isopropylacrylamide) (branched PNIPAM), branched poly(methyl methacrylate) (branched PMA), branched poly(2-hydroxylethyl methacrylate) (branched PHEMA), branched poly(oligo(ethylene glycol) methyl ether methacrylate) (branched POEGMA), branched polyglutamic acid (branched PGA), branched poly-lysine, branched poly-glucoside, and dextran.

In some instances, the branched polymers used to create one or more layers of any of the multi-layered surfaces disclosed herein may comprise at least 4 branches, at least 5 branches, at least 6 branches, at least 7 branches, at least 8 branches, at least 9 branches, at least 10 branches, at least 12 branches, at least 14 branches, at least 16 branches, at least 18 branches, at least 20 branches, at least 22 branches, at least 24 branches, at least 26 branches, at least 28 branches, at least 30 branches, at least 32 branches, at least 34 branches, at least 36 branches, at least 38 branches, or at least 40 branches. Molecules often exhibit a ‘power of 2’ number of branches, such as 2, 4, 8, 16, 32, 64, or 128 branches.

PEG multilayers comprising PEG (8,16,8) on PEG-amine-APTES exposed to two layers of 7 uM primer pre-loading exhibited a concentration of 2,000,000 to 10,000,000 on the surface. Similar concentrations were observed for 3-layer multi-arm PEG (8,16,8) and (8,64,8) on PEG-amine-APTES exposed to 8 uM primer, and 3-layer multi-arm PEG (8,8,8) using star-shaped PEG-amine to replace dumbbell-shaped 16mer and 64mer. PEG multilayers having comparable first, second and third PEG levels are also contemplated.

Linear, branched, or multi-branched polymers used to create one or more layers of any of the multi-layered surfaces disclosed herein may have a molecular weight of at least 500, at least 1,000, at least 2,000, at least 3,000, at least 4,000, at least 5,000, at least 10,000, at least 15,000, at least 20,000, at least 25,000, at least 30,000, at least 35,000, at least 40,000, at least 45,000, or at least 50,000 daltons.

In some instances, e.g., wherein at least one layer of a multi-layered surface comprises a branched polymer, the number of covalent bonds between a branched polymer molecule of the layer being deposited and molecules of the underlying layer may range from about one covalent linkage per molecule to about 32 covalent linkages per molecule. In some instances, the number of covalent bonds between a branched polymer molecule of the new layer and molecules of the underlying layer may be at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 12, at least 14, at least 16, at least 18, at least 20, at least 22, at least 24, at least 26, at least 28, at least 30, or at least 32 or more than 32 covalent linkages per molecule.

Any reactive functional groups that remain following the coupling of a material layer to the support surface may optionally be blocked by coupling a small, inert molecule using a high yield coupling chemistry. For example, in the case that amine coupling chemistry is used to attach a new material layer to the underlying one, any residual amine groups may subsequently be acetylated or deactivated by coupling with a small amino acid such as glycine.

The number of layers of low non-specific binding material, e.g., a hydrophilic polymer material, deposited on the surface of the disclosed low binding supports may range from 1 to about 10. In some instances, the number of layers is at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, or at least 10. In some instances, the number of layers may be at most 10, at most 9, at most 8, at most 7, at most 6, at most 5, at most 4, at most 3, at most 2, or at most 1. Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure, for example, in some instances the number of layers may range from about 2 to about 4. In some instances, all of the layers may comprise the same material. In some instances, each layer may comprise a different material. In some instances, the plurality of layers may comprise a plurality of materials. In some instances, at least one layer may comprise a branched polymer. In some instances, all of the layers may comprise a branched polymer.

One or more layers of low non-specific binding material may, in some cases, be deposited on, or, conjugated to the substrate surface, or a combination thereof, using a polar protic solvent, a polar aprotic solvent, a nonpolar solvent, or any combination thereof. In some instances, the solvent used for layer deposition, or, coupling, or a combination thereof may comprise an alcohol (e.g., methanol, ethanol, propanol, etc.), another organic solvent (e.g., acetonitrile, dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), etc.), water, an aqueous buffer solution (e.g., phosphate buffer, phosphate buffered saline, 3-(N-morpholino)propanesulfonic acid (MOPS), etc.), or any combination thereof. In some instances, an organic component of the solvent mixture used may comprise at least 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or 99% of the total, or any percentage spanned or adjacent to the range herein, with the balance made up of water or an aqueous buffer solution. In some instances, an aqueous component of the solvent mixture used may comprise at least 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or 99% of the total, or any percentage spanned or adjacent to the range herein, with the balance made up of an organic solvent. The pH of the solvent mixture used may be less than or equal to about 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or any value spanned or adjacent to the range described herein. The pH of the solvent mixture may be greater than or equal to about 10.

In some instances, one or more layers of low non-specific binding material may be deposited on, or, conjugated to the substrate surface, or a combination thereof, using a mixture of organic solvents, wherein the dielectric constant of at least once component is less than 40 and constitutes at least 50% of the total mixture by volume. In some instances, the dielectric constant of the at least one component may be less than 10, less than 20, less than 30, or less than 40. In some instances, the at least one component constitutes at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, or at least 80% of the total mixture by volume.

As noted, the low non-specific binding supports of the present disclosure exhibit reduced non-specific binding of proteins, nucleic acids, and other components of the hybridization, or, amplification formulation, or a combination thereof, used for solid-phase nucleic acid amplification. The degree of non-specific binding exhibited by a given support surface may be assessed either qualitatively or quantitatively. For example, in some instances, exposure of the surface to fluorescent dyes (e.g., Cy3, Cy5, etc.), fluorescently-labeled nucleotides, fluorescently-labeled oligonucleotides, or, fluorescently-labeled proteins (e.g., polymerases), or a combination thereof, under a standardized set of conditions, followed by a specified rinse protocol and fluorescence imaging may be used as a qualitative tool for comparison of non-specific binding on supports comprising different surface formulations. In some instances, exposure of the surface to fluorescent dyes, fluorescently-labeled nucleotides, fluorescently-labeled oligonucleotides, or, fluorescently-labeled proteins (e.g., polymerases), or a combination thereof, under a standardized set of conditions, followed by a specified rinse protocol and fluorescence imaging may be used as a quantitative tool for comparison of non-specific binding on supports comprising different surface formulations—provided that care has been taken to ensure that the fluorescence imaging is performed under conditions where fluorescence signal is linearly related (or related in a predictable manner) to the number of fluorophores on the support surface (e.g., under conditions where signal saturation, or, self-quenching of the fluorophore, or a combination thereof, is not an issue) and suitable calibration standards are used. In some instances, other techniques, for example, radioisotope labeling and counting methods may be used for quantitative assessment of the degree to which non-specific binding is exhibited by the different support surface formulations of the present disclosure.

Some surfaces disclosed herein exhibit a ratio of specific to non-specific binding of a fluorophore such as Cy3 of at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 50, 75, 100, or greater than 100, or any intermediate value spanned by the range herein. Some surfaces disclosed herein exhibit a ratio of specific to non-specific fluorescence of a fluorophore such as Cy3 of at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 50, 75, 100, or greater than 100, or any intermediate value spanned by the range herein.

As noted, in some instances, the degree of non-specific binding exhibited by the disclosed low-binding supports may be assessed using a standardized protocol for contacting the surface with a labeled protein (e.g., bovine serum albumin (BSA), streptavidin, a DNA polymerase, a reverse transcriptase, a helicase, a single-stranded binding protein (SSB), etc., or any combination thereof), a labeled nucleotide, a labeled oligonucleotide, etc., under a standardized set of incubation and rinse conditions, followed by detection of the amount of label remaining on the surface and comparison of the signal resulting therefrom to an appropriate calibration standard. In some instances, the label may comprise a fluorescent label. In some instances, the label may comprise a radioisotope. In some instances, the label may comprise any other detectable label. In some instances, the degree of non-specific binding exhibited by a given support surface formulation may thus be assessed in terms of the number of non-specifically bound protein molecules (or other molecules) per unit area. In some instances, the low-binding supports of the present disclosure may exhibit non-specific protein binding (or non-specific binding of other specified molecules, e.g., Cy3 dye) of less than or equal to about 0.001 molecule per μm², less than or equal to about 0.01 molecule per μm², less than or equal to about 0.1 molecule per μm², less than or equal to about 0.25 molecule per μm², less than or equal to about 0.5 molecule per μm², less than or equal to about 1 molecule per μm², less than or equal to about 10 molecules per μm², less than or equal to about 100 molecules per μm², or less than or equal to about 1,000 molecules per μm². A given support surface of the present disclosure may exhibit non-specific binding falling anywhere within this range, for example, of less than 86 molecules per μm².

In some instances, the surfaces disclosed herein exhibit a ratio of specific to non-specific binding of a fluorophore such as Cy3 of at least or equal to about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 50, 75, 100, or any intermediate value spanned by the range herein. In some instances, the surfaces disclosed herein exhibit a ratio of specific to non-specific binding of fluorophore such as Cy3 of greater than or equal to about 100. In some instances, the surfaces disclosed herein exhibit a ratio of specific to non-specific fluorescence signals for a fluorophore such as Cy3 of at least or equal to about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 50, 75, 100, or any intermediate value spanned by the range herein. In some instances, the surfaces disclosed herein exhibit a ratio of specific to non-specific fluorescence signals for a fluorophore such as Cy3 of greater than or equal to about 100.

The low-background surfaces consistent with the disclosure herein may exhibit specific dye attachment (e.g., Cy3 attachment) to non-specific dye adsorption (e.g., Cy3 dye adsorption) ratios of at least 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 30:1, 40:1, 50:1, or more than 50 specific dye molecules attached per molecule non-specifically adsorbed. Similarly, when subjected to an excitation energy, low-background surfaces consistent with the disclosure herein to which fluorophores, e.g., Cy3, have been attached may exhibit ratios of specific fluorescence signal (e.g., arising from Cy3-labeled oligonucleotides attached to the surface) to non-specific adsorbed dye fluorescence signals of at least 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 30:1, 40:1, 50:1, or more than 50:1.

In some instances, the degree of hydrophilicity (or “wettability” with aqueous solutions) of the disclosed support surfaces may be assessed, for example, through the measurement of water contact angles in which a small droplet of water is placed on the surface and its angle of contact with the surface is measured using, e.g., an optical tensiometer. In some instances, a static contact angle may be determined. In some instances, an advancing or receding contact angle may be determined. In some instances, the water contact angle for the hydrophilic, low-binding support surfaced disclosed herein may range from about 0 degrees to about 30 degrees. In some instances, the water contact angle for the hydrophilic, low-binding support surfaced disclosed herein may be no more than 50 degrees, 45 degrees, 40 degrees, 30 degrees, 25 degrees, 20 degrees, 18 degrees, 16 degrees, 14 degrees, 12 degrees, 10 degrees, 8 degrees, 6 degrees, 4 degrees, 2 degrees, or 1 degree. In many cases the contact angle is no more than 40 degrees. A given hydrophilic, low-binding support surface of the present disclosure may exhibit a water contact angle having a value of anywhere within this range.

In some instances, the hydrophilic surfaces disclosed herein facilitate reduced wash times for bioassays, often due to reduced non-specific binding of biomolecules to the low-binding surfaces. In some instances, adequate washes may be performed in less than or equal to about 60, 50, 40, 30, 20, 15, 10, or less than 10 seconds. For example, in some instances adequate washes may be performed in less than 30 seconds.

Some low-binding surfaces of the present disclosure exhibit significant improvement in stability or durability to prolonged exposure to solvents and elevated temperatures, or to repeated cycles of solvent exposure or changes in temperature. For example, in some instances, the stability of the disclosed surfaces may be tested by fluorescently labeling a functional group on the surface, or a tethered biomolecule (e.g., an oligonucleotide primer) on the surface, and monitoring fluorescence signal before, during, and after prolonged exposure to solvents and elevated temperatures, or to repeated cycles of solvent exposure or changes in temperature. In some instances, the degree of change in the fluorescence used to assess the quality of the surface may be less than or equal to about 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, or 25% over a time period of 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 50 hours, or 100 hours of exposure to solvents, or, elevated temperatures, or a combination thereof (or any combination of these percentages as measured over these time periods). In some instances, the degree of change in the fluorescence used to assess the quality of the surface may be less than or equal to about 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, or 25% over 5 cycles, 10 cycles, 20 cycles, 30 cycles, 40 cycles, 50 cycles, 60 cycles, 70 cycles, 80 cycles, 90 cycles, 100 cycles, 200 cycles, 300 cycles, 400 cycles, 500 cycles, 600 cycles, 700 cycles, 800 cycles, 900 cycles, or 1,000 cycles of repeated exposure to solvent changes, or changes in temperature, or a combination thereof (or any combination of these percentages as measured over this range of cycles).

In some instances, the surfaces disclosed herein may exhibit a high ratio of specific signal to non-specific signal or other background. For example, when used for nucleic acid amplification, some surfaces may exhibit an amplification signal that is at least 4-, 5-, 6-, 7-, 8-, 9-, 10-, 15-, 20-, 30-, 40-, 50-, 75-, 100-, or greater than 100-fold greater than a signal of an adjacent unpopulated region of the surface. In some instances, the surfaces exhibit an amplification signal that is at least 4-, 5-, 6-, 7-, 8-, 9-, 10-, 15-, 20-, 30-, 40-, 50-, 75-, 100-, or greater than 100-fold greater than a signal of an adjacent amplified nucleic acid population region of the surface.

Fluorescence excitation energies vary among particular fluorophores and protocols, and may range in excitation wavelength, consistent with fluorophore selection or other parameters of use of a surface disclosed herein. In some instances, the wavelength is less than or equal to about 400 nanometers (nm). In some instances, the wavelength is more than or equal to about 800 nm. In some instances, the wavelength is between 400 nm and 800 nm.

Accordingly, low background surfaces as disclosed herein exhibit low background fluorescence signals or high contrast to noise (CNR) ratios. For example, in some instances, the background fluorescence of the surface at a location that is spatially distinct or removed from a labeled feature on the surface (e.g., a labeled spot, cluster, discrete region, sub-section, or subset of the surface) comprising a hybridized cluster of nucleic acid molecules, or a clonally-amplified cluster of nucleic acid molecules produced by 20 cycles of nucleic acid amplification via thermocycling, may be no more than 20×, 10×, 5×, 2×, 1×, 0.5×, 0.1×, or less than 0.1× greater than the background fluorescence measured at that same location prior to performing said hybridization or said 20 cycles of nucleic acid amplification.

In some instances, fluorescence images of the disclosed low background surfaces when used in nucleic acid hybridization or amplification applications to create clusters of hybridized or clonally-amplified nucleic acid molecules (e.g., that have been directly or indirectly labeled with a fluorophore) exhibit contrast-to-noise ratios (CNRs) of at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 20, 210, 220, 230, 240, 250, or greater than 250.

The surface that comprises the one or more chemically-modified layers, e.g., layers of a low non-specific binding polymer, may be independent or integrated into another structure or assembly. The chemical modification layers may be applied uniformly across the surface. Alternately, the surface may be patterned, such that the chemical modification layers are confined to one or more discrete regions of the substrate. For example, the surface may be patterned using photolithographic techniques to create an ordered array or random pattern of chemically-modified regions on the surface. The substrate surface may be patterned using, e.g., contact printing, or, ink-jet printing techniques, or a combination thereof. In some instances, an ordered array or random patter of chemically-modified regions may comprise at least 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, or 10,000 or more discrete regions.

In order to achieve low non-specific binding surfaces (also referred to herein as “low binding” or “passivated” surfaces), hydrophilic polymers may be non-specifically adsorbed or covalently grafted to the surface. For example, passivation can be performed utilizing poly(ethylene glycol) (PEG, also known as polyethylene oxide (PEO) or polyoxyethylene) or other hydrophilic polymers with different molecular weights and end groups that are linked to a surface using, for example, silane chemistry. The end groups distal from the surface can include, but are not limited to, biotin, methoxy ether, carboxylate, amine, NHS ester, maleimide, and bis-silane. In some instances, two or more layers of a hydrophilic polymer, e.g., a linear polymer, branched polymer, or multi-branched polymer, may be deposited on the surface. In some instances, two or more layers may be covalently coupled to each other or internally cross-linked to improve the stability of the resulting surface. In some instances, oligonucleotide primers with different base sequences and base modifications (or other biomolecules, e.g., enzymes or antibodies) may be tethered to the resulting surface layer at various surface densities. In some instances, for example, both surface functional group density and oligonucleotide concentration may be varied to target a certain primer density range. Additionally, primer density can be controlled by diluting oligonucleotides with other molecules that carry the same functional group. For example, amine-labeled oligonucleotides can be diluted with amine-labeled polyethylene glycol in a reaction with an NETS-ester coated surface to reduce the final primer density. Primers with different lengths of linker between the hybridization region and the surface attachment functional group can also be applied to control surface density. Examples of suitable linkers include poly-T and poly-A strands at the 5′ end of the primer (e.g., 0 to 20 bases), PEG linkers (e.g., 3 to 20 monomer units), and carbon-chain (e.g., C6, C12, C18, etc.). To measure the primer density, fluorescently-labeled primers may be tethered to the surface and a fluorescence reading corresponding to the primers may then be compared with that for a dye solution of known concentration.

As noted, the low non-specific binding surfaces described herein exhibit reduced non-specific binding of nucleic acids, and other components of the hybridization, or, amplification formulation, or a combination thereof used for solid-phase nucleic acid amplification. The degree of non-specific binding exhibited by a given surface may be assessed either qualitatively or quantitatively. For example, in some instances, exposure of the surface to fluorescent dyes (e.g., Cy3, Cy5, etc.), fluorescently-labeled nucleotides, fluorescently-labeled oligonucleotides, or, fluorescently-labeled proteins (e.g., polymerases), or a combination thereof under a standardized set of conditions, followed by a specified rinse protocol and fluorescence imaging may be used as a qualitative tool for comparison of non-specific binding surfaces comprising different surface formulations. In some instances, exposure of the surface to fluorescent dyes, fluorescently-labeled nucleotides, fluorescently-labeled oligonucleotides, or, fluorescently-labeled proteins (e.g., polymerases), or combination thereof under a standardized set of conditions, followed by a specified rinse protocol and fluorescence imaging may be used as a quantitative tool for comparison of non-specific binding on surfaces comprising different surface formulations—provided that care has been taken to ensure that the fluorescence imaging is performed under conditions where fluorescence signal is linearly related (or related in a predictable manner) to the number of fluorophores on the surface (e.g., under conditions where signal saturation, or, self-quenching of the fluorophore, or a combination thereof is not an issue) and suitable calibration standards are used. In some instances, other techniques, for example, radioisotope labeling and counting methods may be used for quantitative assessment of the degree to which non-specific binding is exhibited by the different surface formulations of the present disclosure.

As noted, in some instances, the degree of non-specific binding exhibited by the disclosed low-binding surfaces may be assessed using a standardized protocol for contacting the surface with a labeled protein (e.g., bovine serum albumin (BSA), streptavidin, a DNA polymerase, a reverse transcriptase, a helicase, a single-stranded binding protein (SSB), etc., or any combination thereof), a labeled nucleotide, a labeled oligonucleotide, etc., under a standardized set of incubation and rinse conditions, followed by detection of the amount of label remaining on the surface and comparison of the signal resulting therefrom to an appropriate calibration standard. In some instances, the label may comprise a fluorescent label. In some instances, the label may comprise a radioisotope. In some instances, the label may comprise any other detectable label. In some instances, the degree of non-specific binding exhibited by a given surface formulation may thus be assessed in terms of the number of non-specifically bound protein molecules (or other molecules) per unit area. In some instances, the low-binding surfaces of the present disclosure may exhibit non-specific protein binding (or non-specific binding of other specified molecules, e.g., Cy3 dye) of less than or equal to about 0.001 molecule per μm², less than or equal to about 0.01 molecule per μm², less than or equal to about 0.1 molecule per μm², less than or equal to about 0.25 molecule per μm², less than or equal to about 0.5 molecule per μm², less than or equal to about 1 molecule per μm², less than or equal to about 10 molecules per μm², less than or equal to about 100 molecules per μm², or less than or equal to about 1,000 molecules per μm². A given surface of the present disclosure may exhibit non-specific binding falling anywhere within this range, for example, of less than or equal to about 86 molecules per μm². For example, some modified surfaces disclosed herein exhibit non-specific protein binding of less than or equal to about 0.5 molecule/μm²following contact with a 1 μM solution of bovine serum albumin (BSA) in phosphate buffered saline (PBS) buffer for 30 minutes, followed by a 10 minute PBS rinse. In another example, some modified surfaces disclosed herein exhibit non-specific protein binding of less than or equal to about 0.5 molecule/μm²following contact with a 1 μM solution of Cyanine 3 dye-labeled streptavidin (GE Amersham) in phosphate buffered saline (PBS) buffer for 15 minutes, followed by 3 rinses with deionized water. Some modified surfaces disclosed herein exhibit non-specific binding of Cy3 dye molecules of less than or equal to about 0.25 molecules per μm².

The low-background surfaces consistent with the disclosure herein may exhibit specific dye attachment (e.g., Cy3 attachment) to non-specific dye adsorption (e.g., Cy3 dye adsorption) ratios of at least 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 30:1, 40:1, 50:1, or more than 50 specific dye molecules attached per molecule non-specifically adsorbed. Similarly, when subjected to an excitation energy, low-background surfaces consistent with the disclosure herein to which fluorophores, e.g., Cy3, have been attached may exhibit ratios of specific fluorescence signal (e.g., arising from Cy3-labeled oligonucleotides attached to the surface) to non-specific adsorbed dye fluorescence signals of at least 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 30:1, 40:1, 50:1, or more than 50:1.

In some instances, the degree of hydrophilicity (or “wettability” with aqueous solutions) of the disclosed surfaces may be assessed, for example, through the measurement of water contact angles in which a small droplet of water is placed on the surface and its angle of contact with the surface is measured using, e.g., an optical tensiometer. In some instances, a static contact angle may be determined. In some instances, an advancing or receding contact angle may be determined. In some instances, the water contact angle for the hydrophilic, low-binding surfaces disclosed herein may range from about 0 degrees to about 30 degrees. In some instances, the water contact angle for the hydrophilic, low-binding surfaced disclosed herein may be no more than 50 degrees, 40 degrees, 30 degrees, 25 degrees, 20 degrees, 18 degrees, 16 degrees, 14 degrees, 12 degrees, 10 degrees, 8 degrees, 6 degrees, 4 degrees, 2 degrees, or 1 degree. In many cases the contact angle is no more than 40 degrees. A given hydrophilic, low-binding surface of the present disclosure may exhibit a water contact angle having a value of anywhere within this range.

In some instances, the low-binding surfaces of the present disclosure may exhibit significant improvement in stability or durability to prolonged exposure to solvents and elevated temperatures, or to repeated cycles of solvent exposure or changes in temperature. For example, in some instances, the stability of the disclosed surfaces may be tested by fluorescently labeling a functional group on the surface, or a tethered biomolecule (e.g., an oligonucleotide primer) on the surface, and monitoring fluorescence signal before, during, and after prolonged exposure to solvents and elevated temperatures, or to repeated cycles of solvent exposure or changes in temperature. In some instances, the degree of change in the fluorescence used to assess the quality of the surface may be less than or equal to about 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, or 25% over a time period of 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 50 hours, or 100 hours of exposure to solvents, or, elevated temperatures, or a combination thereof (or any combination of these percentages as measured over these time periods). In some instances, the degree of change in the fluorescence used to assess the quality of the surface may be less than or equal to about 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, or 25% over 5 cycles, 10 cycles, 20 cycles, 30 cycles, 40 cycles, 50 cycles, 60 cycles, 70 cycles, 80 cycles, 90 cycles, 100 cycles, 200 cycles, 300 cycles, 400 cycles, 500 cycles, 600 cycles, 700 cycles, 800 cycles, 900 cycles, or 1,000 cycles of repeated exposure to solvent changes, or, changes in temperature, or a combination thereof (or any combination of these percentages as measured over this range of cycles).

In some instances, the surfaces disclosed herein may exhibit a high ratio of specific signal to non-specific signal or other background. For example, when used for nucleic acid amplification, some surfaces may exhibit an amplification signal that is at least 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 75, 100, or greater than 100 fold greater than a signal of an adjacent unpopulated region of the surface. Similarly, some surfaces exhibit an amplification signal that is at least 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 75, 100, or greater than 100 fold greater than a signal of an adjacent amplified nucleic acid population region of the surface.

Accordingly, low background surfaces as disclosed herein exhibit low background fluorescence signals or high contrast to noise (CNR) ratios.

Flow Cell Devices: The low non-specific binding surfaces described herein, in some examples, are surfaces of a flow device described herein. Flow devices described herein can include a first reservoir housing a first solution and having an inlet end and an outlet end, wherein the first agent flows from the inlet end to the outlet end in the first reservoir; a second reservoir housing a second solution and having an inlet end and an outlet end, wherein the second agent flows from the inlet end to the outlet end in the second reservoir; a central region having an inlet end fluidically coupled to the outlet end of the first reservoir and the outlet end of the second reservoir through at least one valve. In the flow cell device, the volume of the first solution flowing from the outlet of the first reservoir to the inlet of the central region is less than the volume of the second solution flowing from the outlet of the second reservoir to the inlet of the central region.

The reservoirs described in the device can be used to house different reagents. In some examples, the first solution housed in the first reservoir is different from the second solution that is housed in the second reservoir. The second solution comprises at least one reagent common to a plurality of reactions occurring in the central region. In some examples, the second solution comprises at least one reagent selected from the list consisting of a solvent, a polymerase, and a dNTP. In some examples, the second solution comprise low cost reagents. In some examples, the first reservoir is fluidically coupled to the central region through a first valve and the second reservoir is fluidically coupled to the central region through a second valve. The valve can be a diaphragm valve or other suitable valves.

The central region can include a capillary tube or microfluidic chip having one or more microfluidic channels. In some examples, the capillary tube is an off-shelf product. The capillary tube or the microfluidic chip can also be removable from the device. In some examples, the capillary tube or microfluidic channel comprises an oligonucleotide population directed to sequence a eukaryotic genome. In some examples, the capillary tube or microfluidic channel in the central region is removable.

Disclosed herein are single capillary flow cell devices that comprise a single capillary and one or two fluidic adapters affixed to one or both ends of the capillary, where the capillary provides a fluid flow channel of specified cross-sectional area and length, and where the fluidic adapters are configured to mate with standard tubing to provide for convenient, interchangeable fluid connections with an external fluid flow control system. In general, the capillary used in the disclosed flow cell devices (and flow cell cartridges to be described below) will have at least one internal, axially-aligned fluid flow channel (or “lumen”) that runs the full length of the capillary. In some examples, the capillary may have two, three, four, five, or more than five internal, axially-aligned fluid flow channels (or “lumens”).

A number specified cross-sectional geometries for a single capillary (or a lumen thereof) are consistent with the disclosure herein, including, but not limited to, circular, elliptical, square, rectangular, triangular, rounded square, rounded rectangular, or rounded triangular cross-sectional geometries. In some examples, the single capillary (or lumen thereof) may have any specified cross-sectional dimension or set of dimensions. For example, in some examples, the largest cross-sectional dimension of the capillary lumen (e.g., the diameter, if the lumen is circular in shape, or the diagonal, if the lumen is square or rectangular in shape) may range from about 10 μm to about 10 mm. The length of the one or more capillaries used to fabricate the disclosed single capillary flow cell devices or flow cell cartridges may range from about 5 mm to about 5 cm or greater. Capillaries, in some examples, have a gap height of about or exactly 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 350, 400, or 500 um, or any value falling within the range defined thereby.

Disclosed herein also are flow cell devices that comprise one or more microfluidic chips and one or two fluidic adapters affixed to one or both ends of the microfluidic chips, where the microfluidic chip provides one or more fluid flow channels of specified cross-sectional area and length, and where the fluidic adapters are configured to mate with the microfluidic chip to provide for convenient, interchangeable fluid connections with an external fluid flow control system.

The microfluidic chip described herein includes one or more microfluidic channels etched on the surface of the chip. The microfluidic channels are defined as fluid conduits with at least one minimum dimension from <1 nm to 1000 μm. The microfluidic channel system, fabricated on either a glass or silicon substrate, has channel heights and widths on the order of <1 nm to 1000 μm. The channel length can be in the micrometer range.

The capillaries or microfluidic chip used for constructing the disclosed flow cell devices may be fabricated from any of a variety of materials known to those of skill in the art including, but not limited to, glass (e.g., borosilicate glass, soda lime glass, etc.), fused silica (quartz), polymer (e.g., polystyrene (PS), macroporous polystyrene (MPPS), polymethylmethacrylate (PMMA), polycarbonate (PC), polypropylene (PP), polyethylene (PE), high density polyethylene (HDPE), cyclic olefin polymers (COP), cyclic olefin copolymers (COC), polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), etc.), polyetherimide (PEI) and perfluoroelastomer (FFKM) as more chemically inert examples. PEI is somewhere between polycarbonate and PEEK in terms of both cost and compatibility. FFKM is also known as Kalrez.

In some examples, a flow cell device described herein (e.g., a microfluidic chip or capillary flow cell) is operatively coupled to an imaging system described herein to capture or detect signals of DNA bases for applications such as nucleic acid sequencing, analyte capture and detection, and the like.

Oligonucleotide primers and adapter sequences: In general, at least one layer of the one or more layers of low non-specific binding material may comprise functional groups for covalently or non-covalently attaching oligonucleotide adapter or primer sequences, or the at least one layer may already comprise covalently or non-covalently attached oligonucleotide adapter or primer sequences at the time that it is deposited on the support surface. In some instances, the oligonucleotides tethered to the polymer molecules of at least one third layer may be distributed at a plurality of depths throughout the layer.

One or more types of oligonucleotide primer may be attached or tethered to the support surface. In some instances, the one or more types of oligonucleotide adapters or primers may comprise spacer sequences, adapter sequences for hybridization to adapter-ligated template library nucleic acid sequences, forward amplification primers, reverse amplification primers, sequencing primers, or, molecular barcoding sequences, or any combination thereof. In some instances, 1 primer or adapter sequence may be tethered to at least one layer of the surface. In some instances, at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 10 different primer or adapter sequences may be tethered to at least one layer of the surface.

In some instances, the tethered oligonucleotide adapter, or, primer sequences, or a combination thereof may range in length from about 10 nucleotides to about 100 nucleotides. In some instances, the tethered oligonucleotide adapter, or, primer sequences, or a combination thereof may be at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90, or at least 100 nucleotides in length. In some instances, the tethered oligonucleotide adapter, or, primer sequences, or a combination thereof may be at most 100, at most 90, at most 80, at most 70, at most 60, at most 50, at most 40, at most 30, at most 20, or at most 10 nucleotides in length. Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure, for example, in some instances the length of the tethered oligonucleotide adapter, or, primer sequences, or combination thereof may range from about 20 nucleotides to about 80 nucleotides. The length of the tethered oligonucleotide adapter, or, primer sequences, or combination thereof may have any value within this range, e.g., about 24 nucleotides.

In some instances, the tethered primer sequences may comprise modifications designed to facilitate the specificity and efficiency of nucleic acid amplification as performed on the low-binding supports. For example, in some instances the primer may comprise polymerase stop points such that the stretch of primer sequence between the surface conjugation point and the modification site is always in single-stranded form and functions as a loading site for 5′ to 3′ helicases in some helicase-dependent isothermal amplification methods. Other examples of primer modifications that may be used to create polymerase stop points include, but are not limited to, an insertion of a PEG chain into the backbone of the primer between two nucleotides towards the 5′ end, insertion of an abasic nucleotide (e.g., a nucleotide that has neither a purine nor a pyrimidine base), or a lesion site which can be bypassed by the helicase.

As will be discussed further in the examples below, the surface density of tethered primers on the support surface, or, the spacing of the tethered primers away from the support surface (e.g., by varying the length of a linker molecule used to tether the primers to the surface), or a combination thereof, may be varied in order to “tune” the support for optimal performance when using a given amplification method. As noted below, adjusting the surface density of tethered primers may impact the level of specific, or, non-specific amplification, or a combination thereof, observed on the support in a manner that varies according to the amplification method selected. In some instances, the surface density of tethered oligonucleotide primers may be varied by adjusting the ratio of molecular components used to create the support surface. For example, in an example where an oligonucleotide primer—PEG conjugate is used to create the final layer of a low-binding support, the ratio of the oligonucleotide primer—PEG conjugate to a non-conjugated PEG molecule may be varied. The resulting surface density of tethered primer molecules may then be estimated or measured using any of a variety of techniques. Examples include, but are not limited to, the use of radioisotope labeling and counting methods, covalent coupling of a cleavable molecule that comprises an optically-detectable tag (e.g., a fluorescent tag) that may be cleaved from a support surface of defined area, collected in a fixed volume of an appropriate solvent, and then quantified by comparison of fluorescence signals to that for a calibration solution of known optical tag concentration, or using fluorescence imaging techniques provided that care has been taken with the labeling reaction conditions and image acquisition settings to ensure that the fluorescence signals are linearly related to the number of fluorophores on the surface (e.g., that there is no significant self-quenching of the fluorophores on the surface).

In some instances, the resultant surface density of oligonucleotide primers on the low binding support surfaces of the present disclosure may range from about 1,000 primer molecules per μm²to about 1,000,000 primer molecules per μm². In some instances, the surface density of oligonucleotide primers may be at least 1,000, at least 10,000, at least 100,000, or at least 1,000,000 molecules per μm². In some instances, the surface density of oligonucleotide primers may be at most 1,000,000, at most 100,000, at most 10,000, or at most 1,000 molecules per μm². Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure, for example, in some instances the surface density of primers may range from about 10,000 molecules per μm²to about 100,000 molecules per μm². The surface density of primer molecules may have any value within this range, e.g., about 455,000 molecules per μm². In some instances, the surface density of template library nucleic acid sequences initially hybridized to adapter or primer sequences on the support surface may be less than or equal to that indicated for the surface density of tethered oligonucleotide primers. In some instances, the surface density of clonally-amplified template library nucleic acid sequences hybridized to adapter or primer sequences on the support surface may span the same range as that indicated for the surface density of tethered oligonucleotide primers.

Local densities as listed above do not preclude variation in density across a surface, such that a surface may comprise a region having an oligo density of, for example, 500,000 per μm², while also comprising at least a second region having a substantially different local density.

Imaging Systems. Imaging systems described herein are utilized to detect hybridization between one or more sample nucleic acid molecules and capture nucleic acid molecules coupled to a low non-specific binding surface. In some examples, the imaging systems comprise a camera. In some examples, the imaging systems comprise a microscope, such as a fluorescence microscope. An inverted fluorescence microscope in combination with a camera may be used to capture an image of the low non-specific binding surface and visualize hybridization between one or more sample nucleic acid molecules and capture nucleic acid molecules. A non-limiting example of an imaging system described herein is an Olympus IX83 microscope (Olympus Corp., Center Valley, Pa.) with a total internal reflectance fluorescence (TIRF) objective (100×, 1.5 NA, Olympus), a CCD camera (e.g., an Olympus EM-CCD monochrome camera, Olympus XM-10 monochrome camera, or an Olympus DP80 color and monochrome camera), an illumination source (e.g., an Olympus 100 W Hg lamp, an Olympus 75 W Xe lamp, or an Olympus U-HGLGPS fluorescence light source), and excitation wavelengths of 532 nm or 635 nm. Dichroic mirrors were purchased from Semrock (IDEX Health & Science, LLC, Rochester, N.Y.), e.g., 405, 488, 532, or 633 nm dichroic reflectors/beamsplitters, and band pass filters were chosen as 532 LP or 645 LP concordant with the appropriate excitation wavelength.

Computer Control Systems. The present disclosure provides computer systems that are programmed or otherwise configured to implement methods provided herein, such as, for example, methods for nucleic sequencing, storing reference nucleic acid sequences, conducting sequence analysis and/or comparing sample and reference nucleic acid sequences as described herein. An example of such a computer system is shown in FIG. 10. As shown in FIG. 10, the computer system 1001 includes a central processing unit (CPU, also “processor” and “computer processor” herein) 1005, which can be a single core or multi core processor, or a plurality of processors for parallel processing. The computer system 1001 also includes memory or memory location 1010 (e.g., random-access memory, read-only memory, flash memory), an electronic storage unit 1015 (e.g., hard disk), a communication interface 1020 (e.g., network adapter) for communicating with one or more other systems, and peripheral devices 1025, such as cache, other memory, data storage and/or electronic display adapters. The memory 1010, storage unit 1015, interface 1020 and peripheral devices 1025 are in communication with the CPU 1005 through a communication bus (solid lines), such as a motherboard. The storage unit 1015 can be a data storage unit (or data repository) for storing data. The computer system 1001 can be operatively coupled to a computer network (“network”) 1030 with the aid of the communication interface 1020. The network 1030 can be the Internet, an internet and/or extranet, or an intranet and/or extranet that is in communication with the Internet. The network 1030 in some cases is a telecommunication and/or data network. The network 1030 can include one or more computer servers, which can enable distributed computing, such as cloud computing. The network 1030, in some instances, with the aid of the computer system 1001, can implement a peer-to-peer network, which may enable devices coupled to the computer system 1001 to behave as a client or a server.

The CPU 1005 can execute a sequence of machine-readable instructions, which can be embodied in a program or software. The instructions may be stored in a memory location, such as the memory 1010. Examples of operations performed by the CPU 1005 can include fetch, decode, execute, and writeback.

The storage unit 1015 can store files, such as drivers, libraries and saved programs. The storage unit 1015 can store user data, e.g., user preferences and user programs. The computer system 1001 in some instances can include one or more additional data storage units that are external to the computer system 1001, such as located on a remote server that is in communication with the computer system 1001 through an intranet or the Internet.

The computer system 1001 can communicate with one or more remote computer systems through the network 1030. For instance, the computer system 1001 can communicate with a remote computer system of a user (e.g., operator). Examples of remote computer systems include personal computers (e.g., portable PC), slate or tablet PC's (e.g., Apple® iPad, Samsung® Galaxy Tab), telephones, Smart phones (e.g., Apple® iPhone, Android-enabled device, Blackberry®), or personal digital assistants. The user can access the computer system 1001 via the network 1030.

Methods as described herein can be implemented by way of machine (e.g., computer processor) executable code stored on an electronic storage location of the computer system 1001, such as, for example, on the memory 1010 or electronic storage unit 1015. The machine executable or machine readable code can be provided in the form of software. During use, the code can be executed by the processor 1005. In some cases, the code can be retrieved from the storage unit 1015 and stored on the memory 1010 for ready access by the processor 1005. In some situations, the electronic storage unit 1015 can be precluded, and machine-executable instructions are stored on memory 1010.

The code can be pre-compiled and configured for use with a machine comprising a processer adapted to execute the code or can be compiled during runtime. The code can be supplied in a programming language that can be selected to enable the code to execute in a pre-compiled or as-compiled fashion.

Aspects of the systems and methods provided herein, such as the computer system 1001, can be embodied in programming. Various aspects of the technology may be thought of as “products” or “articles of manufacture” typically in the form of machine (or processor) executable code and/or associated data that is carried on or embodied in a type of machine readable medium. Machine-executable code can be stored on an electronic storage unit, such memory (e.g., read-only memory, random-access memory, flash memory) or a hard disk. “Storage” type media can include any or all of the tangible memory of the computers, processors or the like, or associated modules thereof, such as various semiconductor memories, tape drives, disk drives and the like, which may provide non-transitory storage at any time for the software programming. All, or portions, of the software may at times be communicated through the Internet or various other telecommunication networks. Such communications, for example, may enable loading of the software from one computer or processor into another, for example, from a management server or host computer into the computer platform of an application server. Thus, another type of media that may bear the software elements includes optical, electrical and electromagnetic waves, such as those used across physical interfaces between local devices, through wired and optical landline networks and over various air-links. The physical elements that carry such waves, such as wired or wireless links, optical links or the like, also may be considered as media bearing the software. As used herein, unless restricted to non-transitory, tangible “storage” media, terms such as computer or machine “readable medium” refer to any medium that participates in providing instructions to a processor for execution.

Hence, a machine readable medium, such as computer-executable code, may take many forms, including but not limited to, a tangible storage medium, a carrier wave medium or physical transmission medium. Non-volatile storage media include, for example, optical or magnetic disks, such as any of the storage devices in any computer(s) or the like, such as may be used to implement the databases, etc. shown in the drawings. Volatile storage media include, for example, dynamic memory, such as main memory of such a computer platform. Tangible transmission media include, for example, coaxial cables; copper wire and fiber optics, including the wires that comprise a bus within a computer system. Carrier-wave transmission media may take the form of electric or electromagnetic signals, or acoustic or light waves such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media therefore include, for example: a floppy disk, a flexible disk, a hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD or DVD-ROM, any other optical medium, punch cards paper tape, any other physical storage medium with patterns of holes, a RAM, a ROM, a PROM and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave transporting data or instructions, cables or links transporting such a carrier wave, or any other medium from which a computer may read programming code and/or data. Many of these forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to a processor for execution.

The computer system 1001 can include, or be in communication with, an electronic display 1035 that comprises a user interface (UI) for providing, for example, an output or readout of a nucleic acid sequencing instrument coupled to the computer system 1001. Such readout can include a nucleic acid sequencing readout, such as a sequence of nucleic acid bases that comprise a given nucleic acid sample. The UI may also be used to display the results of an analysis making use of such readout. Examples of UI's include, without limitation, a graphical user interface (GUI) and web-based user interface. The electronic display 1035 can be a computer monitor, or a capacitive or resistive touchscreen.

Performance of Compositions and Systems

Improvements in hybridization rate: In some instances, the use of the buffer formulations disclosed herein (optionally, used in combination with a low non-specific binding surface) yield relative hybridization rates that range from about 2× to about 20× faster than that for a standard hybridization protocol. In some instances, the relative hybridization rate may be at least 2×, at least 3×, at least 4×, at least 5×, at least 6×, at least 7×, at least 8×, at least 9×, at least 10×, at least 12×, at least 14×, at least 16×, at least 18×, or at least 20× that for a standard hybridization protocol.

The method and compositions described herein can help shorten the time required for completing hybridization. In some embodiments, the hybridization time can be in the range of about 1 seconds (s) to 2 hours (h), about 5 s to 1.5 h, about 15 s to 1 h, or about 15 s to 0.5 h. In some embodiments, the hybridization time can be in the range of about 15 s to 1 h. In some embodiments, the hybridization time can be shorter than 15 s, 30 s, 1 minutes (min), 1.5 min, 2 min, 2.5 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 15 min, 20 min, 25 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, or 120 min. In some embodiments, the hybridization time can be longer than 1 s, 5 s, 10 s, 15 s, 30 s, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 4 min, or 5 min.

The annealing methods described herein can significantly shorten the annealing time. In some instances, at least 90% of the target nucleic acid anneals to the surface bound nucleic acid in less than or equal to about 15 s, 30 s, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 15 min, 20 min, 25 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, or 120 min. In some instances, at least 80% of the target nucleic acid anneals to the surface bound nucleic acid in less than or equal to about 15 s, 30 s, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 15 min, 20 min, 25 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, or 120 min. In some instances, at least 90% of the target nucleic acid anneals to the surface bound nucleic acid in greater than or equal to about 1 s, 5 s, 10 s, 15 s, 30 s, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 4 min, or 5 min. In some instances, at least 90% of the target nucleic acid anneals to the surface bound nucleic acid in the range of about 10 s to about 1 hour, about 30 s to about 50 min, about 1 min to about 50 min, or about 1 min to about 30 min. In some instances, at least 90% of the target nucleic acid anneals to the surface bound nucleic acid in between 2-25, 3-24, 4-23, 5-23, 6-22, 7-21, 8-20, 9-19, 10-18, 11-17, 12-16, or 13-15 min.

Improvements in hybridization efficiency: As used herein, hybridization efficiency (or yield) is a measure of the percentage of total available tethered adapter sequences on a solid surface, primer sequences, or oligonucleotide sequences in general that are hybridized to complementary sequences. In some instances, the use of optimized buffer formulations disclosed herein (optionally, used in combination with a low non-specific binding surface) yield improved hybridization efficiency compared to that for a standard hybridization protocol. In some instances, the hybridization efficiency that may be achieved is better than 80%, 85%, 90%, 95%, 98%, or 99% in any of the hybridization reaction times specified above.

The methods and compositions described herein can be used in an isothermal annealing conditions. In some embodiments, the methods described herein can eliminate the cooling required for most hybridizations. In some embodiments, the annealing methods described herein can be performed at a temperature in the range of about 10° C. to 95° C., about 20° C. to 80° C., or about 30° C. to 70° C. In some embodiments, the temperature can be lower than about 40° C., 50° C., 60° C., 70° C., 80° C., or 90° C.

Improvements in hybridization specificity: Methods, systems, compositions, and kits described herein provide for improved hybridization specificity, as compared to, for example, a hybridization reaction performed on a low-non-specific binding surface described herein at 90 degrees Celsius for 5 minutes followed by cooling for 120 minutes to reach a final temperature of 37 degrees Celsius in a buffer comprising saline-sodium citrate. In some instances, the hybridization specificity that may be achieved is better than 1 base mismatch in 10 hybridization events, 1 base mismatch in 100 hybridization events, 1 base mismatch in 1,000 hybridization events, or 1 base mismatch in 10,000 hybridization events. Hybridization specificity may be measured using techniques described herein

In some examples, at least or about 70%, 80%, or 90% of the sample nucleic acid molecules correctly hybridize to the capture nucleic acid molecules (e.g., adapter sequences, primer sequences, or oligonucleotide sequences) with a complementary sequence. In some examples, more than 90% of the sample nucleic acid molecules correctly hybridize to the capture nucleic acid molecules. In some examples, between 90%-99% of the sample nucleic acid molecules correctly hybridize to the capture nucleic acid molecules. In some examples, 100% of the sample nucleic acid molecules correctly hybridize to the capture nucleic acid molecules.

Hybridization specificity can be measured, by hybridizing labeled (e.g., Cy3) complementary oligos to surface bound nucleic acid molecules immobilized to the surface, dehybridizing and collecting the hybridized oligos, measuring a fluorescent signal from the collected oligos using a fluorescence plate reader at the appropriate excitation and emission wavelengths (e.g., 532, peak 570/30). The results can be used to develop standard curves for accurately measuring concentration. This assay can be repeated with oligos that show varying degrees of complementarity and the respective specificities.

Hybridization specificity as measured on the surface, may be measured by dividing the nonspecific background counts (e.g., calculated using methods provided in example 3) by the nonspecific probe hybridization-nonspecific background counts (also may be calculated using methods in example 3). Calibration curves can be built using the hybridization specificity measurements. Experiments with oligos having varying degrees of complementarity can be used to calculate respective specificities more accurately.

The specificity of a given nucleic acid probe, p, can be quantified by the relative sensitivity when a p spot is exposed to a perfectly matched target, t, or to a mismatch, m,

$\frac{{}^{t}S_{e}}{{}^{m}S_{e}} = \frac{{}^{m}c_{50}^{0}}{{}^{t}c_{50}^{0}} = \frac{K_{t}}{K_{m}} .$

The specificity of the assay can be quantified by considering the fraction of incorrectly hybridized probes,

$P_{m} . P_{m} = \frac{y}{x + y} = \frac{c_{m} K_{m}}{c_{m} K_{m} + c_{t} K_{t}} .$

In this case, y=x(c_m/c_t)(K_m/K_t).

Improvements in hybridization sensitivity. “Hybridization sensitivity” refers to a concentration range of sample (or target) nucleic molecules in which hybridization occurs with a target hybridization specificity. In some instances, the target hybridization specificity is 90%, or more. In some instances, the methods, systems, compositions, and kits described herein utilize less than a 10 nanomolar concentration of sample nucleic acid molecules to hybridize the sample nucleic acid molecules to capture nucleic acid molecules with high specificity. In some instances, between a 10 nanomolar and 50 picomolar concentration of sample nucleic acid molecules is used. In some instances, between a 9 nanomolar and 100 picomolar concentration of sample nucleic acid molecules is used. In some instances, between a 9 nanomolar and 150 picomolar concentration of sample nucleic acid molecules is used. In some instances, between a 7 nanomolar and 200 picomolar concentration of sample nucleic acid molecules is used. In some instances, between a 6 nanomolar and 250 picomolar concentration of sample nucleic acid molecules is used. In some instances, between a 5 nanomolar and 250 picomolar concentration of sample nucleic acid molecules is used. In some instances, between a 4 nanomolar and 300 picomolar concentration of sample nucleic acid molecules is used. In some instances, between a 3 nanomolar and 350 picomolar concentration of sample nucleic acid molecules is used. In some instances, between a 2 nanomolar and 400 picomolar concentration of sample nucleic acid molecules is used. In some instances, between a 1 nanomolar and 500 picomolar concentration of sample nucleic acid molecules is used. In some instances, less than or equal to about a 1 nanomolar concentration of sample nucleic acid molecules is used. In some instances, less than or equal to about a 250 picomolar concentration of sample nucleic acid molecules is used. In some instances, less than or equal to about a 200 picomolar concentration of a sample nucleic acid molecules is used. In some instances, less than or equal to about a 150 picomolar concentration of sample nucleic acid molecules is used. In some instances, less than or equal to about a 100 picomolar concentration of sample nucleic acid molecules is used. In some instances, less than or equal to about a 50 picomolar concentration of sample nucleic acid molecules is used.

In some instances, the hybridization sensitivity is calculated using the International Union of Pure and Applied Chemistry (IUPAC) analytical techniques, which identify the sensitivity, S_e, with the slope of the calibration curve. The calibration curve describes the measured response, R, to a target concentration, c_t, R(c_t), and S_e=dR/dc_t.

The quantitative resolution of the assay, Act, is then specified by Δc_t=∈_r(c_t)/S_e(c_t), where ∈_ris the measurement error as given by its standard deviation. The detection limit, the lowest detectable c_t, is determined by Δc_t(c_t=0), because when the concentration c_tis lower than Δc_t(c_t=0), the error is larger than the signal; and assuming that R(ct) is proportional to the equilibrium hybridization fraction at the surface, x; i.e., R(ct)=κx+const where κ is a constant. This assumption is justified when the following conditions are fulfilled: (1) nonspecific adsorption is negligible and R is due only to hybridization at the surface; (2) the duration of the experiment is sufficiently long to allow the hybridization to reach equilibrium; and (3), the measured signal depends linearly on the amount of oligonucleotides at the surface.

Nucleic Acid Sequencing Applications

Nucleic acid sequencing is among the many applications for which the methods, compositions, systems, and kits described herein may be useful. Referring to FIG. 2, the methods disclosed herein, in some embodiments, comprise preparing a library of sample nucleic acid molecules for sequencing, hybridizing the library of sample nucleic acids to nucleic acid molecules coupled to a low non-specific binding surface in the presence of the hybridizing compositions described herein, amplifying the library of sample nucleic acids in situ, optionally linearizing the amplified sample nucleic acids in situ, de-hybridizing the linearized and amplified sample nucleic acids from the nucleic acid molecules coupled to the low non-specific binding surface, hybridizing a primer sequence to the sample nucleic acids, and sequencing the sample nucleic acids.

FIG. 6 provides an example of a workflow of the methods described herein, wherein a library of sample nucleic acid molecules is prepared 601, for example by a split ligation protocol, the library of sample nucleic acid molecules is hybridized to nucleic acid molecules coupled to a low non-specific binding surface in the presence of a hybridization composition described herein 602, hybridization of the sample nucleic acid molecules to the nucleic acid molecules coupled to the low non-specific binding surface occurs 603, sequencing primers are hybridized to complementary primer binding sequences on sample nucleic acids 604, and sequencing of the sample nucleic acids is performed 605.

FIG. 7 provides an example sequencing workflow of the methods described herein, wherein a labeled deoxyribonucleotide triphosphate (dNTP) binds to the sample nucleic acid molecule to determine the identity of the complementary nucleotide in the nucleic acid sequence of the sample nucleic acid molecule 701. In some instances, the dNTP is labeled with a fluorophore (e.g., Cy3), either directly or by interaction with a labeled detection reagent. The surface is optionally washed, to remove the unbound labeled dNTP. The surface is imaged to detect the presence of the labeled dNTP 702. The labeled dNTP is unbound from the sample nucleic acid molecule, and a blocked unlabeled dNTP is incorporated into the sample nucleic acid molecule 703. The blocked unlabeled nucleotide is cleaved 704. Steps 701-704 are repeated for the next nucleotide in the sample nucleic acid molecule 705.

The methods, compositions, systems, and kits described herein provide at least the following advantages, particularly in a nucleic acid sequencing process: (i) decreased fluidic wash times (due to reduced non-specific binding, and thus faster sequencing cycle times), (ii) decreased imaging times (and thus faster turnaround times for assay readout and sequencing cycles), (iii) decreased overall work flow time requirements (due to decreased cycle times), (iv) decreased detection instrumentation costs (due to the improvements in contrast-to-noise ratio), (v) improved readout (base-calling) accuracy (due to improvements in contrast-to-noise ratio), (vi) improved reagent stability and decreased reagent usage requirements (and thus reduced reagents costs), and (vii) fewer run-time failures due to nucleic acid amplification failures.

Methods of Analyzing a Target Nucleic Acid Utilizing Multivalent Binding or Incorporation Compositions. Disclosed herein are multivalent binding or incorporation compositions and uses of said compositions in analyzing nucleic acid molecules, including in sequencing or other bioassay applications. An increase in binding or incorporation of a nucleotide to an enzyme (e.g., polymerase) or an enzyme complex can be affected by increasing the effective concentration of the nucleotide. The increase can be achieved by increasing the concentration of the nucleotide in free solution, or by increasing the amount of the nucleotide in proximity to the relevant binding or incorporation site. The increase can also be achieved by physically restricting a number of nucleotides to a limited volume, thus resulting in a local increase in concentration, and, resultingly, in the nucleotides binding or incorporating to a binding or incorporation site with a higher apparent avidity than would be observed with unconjugated, untethered, or otherwise unrestricted individual nucleotides. One non-limiting mechanism of effecting such a restriction is a multivalent binding or incorporation composition in which multiple nucleotides are bound to a particle such as a polymer, a branched polymer, a dendrimer, a micelle, a liposome, a microparticle, a nanoparticle, a quantum dot, or other suitable particle known in the art.

The multivalent binding or incorporation composition disclosed herein can include at least one particle-nucleotide conjugate, wherein the particle-nucleotide conjugate comprises a plurality of copies of the same nucleotide attached to a particle. When the nucleotide is complementary to the target nucleic acid, the particle-nucleotide conjugate forms a binding or incorporation complex with the polymerase and the target nucleic acid, and the binding or incorporation complex exhibits increased stability and longer persistence time than the binding or incorporation complex formed using a single unconjugated or untethered nucleotide. Each of the nucleotide moieties of the multivalent binding composition may bind to a complementary N+1 nucleotide of a primed target nucleic acid molecule, thereby forming a multivalent binding complex comprising two or more target nucleic acid molecules, two or more polymerase (or other enzyme) molecules, and the multivalent binding composition (e.g., the polymer-nucleotide conjugate). Each of the nucleotide moieties of the multivalent binding composition may bind to a complementary N nucleotide of a primed target nucleic acid molecule, thereby forming a multivalent binding complex comprising two or more target nucleic acid molecules, two or more polymerase (or other enzyme) molecules, and the multivalent binding composition (e.g., the polymer-nucleotide conjugate). From this bound complex the nucleotide can interrogate the complementary base prior to incorporation of a modified reversibly blocked nucleotide that elongates the replicating strand by 1 base. In addition, it is possible to imagine interrogation of the N nucleotide with a bound complex, stepping forward with a reversibly terminated nucleotide, and subsequently probing the N+1 base to pre- and post-deblocking. In this way you could perform error checking and improve the overall accuracy of base-calling by reading the interrogated base twice. The important discriminating factor from traditional methods is the binding is used to interrogate the matched base, while the stepping or incorporation step is used only to move forward on the elongating strand.

The multivalent binding or incorporation composition described herein can be used to localize detectable signals to active regions of biochemical interactions, such as sites of protein-nucleic acid interactions, nucleic acid hybridization reactions, or enzymatic reactions, such as polymerase reactions. For instance, the multivalent binding or incorporation composition described herein can be utilized to identify sites of base incorporation in elongating nucleic acid chains during polymerase reactions and to provide base discrimination for sequencing and array-based applications. The increased binding or incorporation between the target nucleic acid and the nucleotide in the multivalent binding or incorporation composition, when the nucleotide is complementary to the target nucleic acid, provides enhanced signal that greatly improve base call accuracy and shortens imaging time.

In addition, the use of multivalent binding composition described herein allows sequencing signals from a given sequence to originate within cluster regions containing multiple copies of the target sequence. Sequencing methods incorporating multiple copies of a target sequence are advantageous in that signals can be amplified due to the presence of multiple simultaneous sequencing reactions within the defined region, each providing its own signal. The presence of multiple signals within a defined area also reduces the impact of any single skipped cycle, due to the fact that the signal from a large number of correct base calls can overwhelm the signal from a smaller number of skipped or incorrect base calls, therefore providing methods for reducing phasing errors and/or improving read length in sequencing reactions.

The multivalent binding compositions and their uses disclosed herein lead to one or more of: (i) a stronger signal for better base-calling accuracy compared to nucleic acid amplification and sequencing methodologies using, for example, protic solvents; ii) greater discrimination of sequence-specific signal from background signals; (iii) reduced requirements for the amount of starting material necessary, (iv) increased sequencing rate and shortened sequencing time; (v) reducing phasing errors, and (vi) improving read length in sequencing reactions.

In some examples, the target nucleic acid refers to a target nucleic acid sample having one or more nucleic acid molecules. In some examples, the target nucleic acid includes a plurality of nucleic acid molecules. In some examples, the target nucleic acid includes two or more nucleic acid molecules. In some examples, the target nucleic acid includes two or more nucleic acid molecules having the same sequences.

Sequencing Target Nucleic Acid

FIG. 12A-12H illustrate a non-limiting example of a method in which the multivalent binding composition is used for sequencing a target nuclei acid. As shown in FIG. 12A, the target nucleic acid 1202 can be tethered to a solid support surface 1201. The target nucleic acid can be attached to the surface either directly or indirectly. Although not shown in FIG. 12A, the target nucleic acid 1202 can be hybridized to an adapter, which is attached to the surface through a covalent or noncovalent bond. When one or more adapters are used to attach the target nucleic acid to the surface, the target surface can comprise a fragment that is complementary to the adapter and thus hybridize to the adaptor. In some instances, one adapter sequence may be tethered to the surface. In some instances, a plurality of adapter sequences may be tethered to the surface. In some instances, the target nucleic acid 1202 can also be attached directly to the solid-support surface without the use of an adapter. The solid support can be a low non-specific binding surface.

In FIG. 12B, after the initial step of attaching the target nucleic acid to the surface of a solid support surface (e.g., through hybridization to adapters), the target nucleic acid is then clonally-amplified to form clusters of amplified nucleic acids. When the target nucleic acid is attached to the surface through an adapter, the surface density of clonally-amplified nucleic acid sequences hybridized to adapter on the support surface may span the same range as the surface density of tethered adapters (or primers). The clonal amplification may be performed using a polymerase chain reaction (PCR), multiple displacement amplification (MDA), transcription-mediated amplification (TMA), nucleic acid sequence-based amplification (NASBA), strand displacement amplification (SDA), real-time SDA, bridge amplification, isothermal bridge amplification, rolling circle amplification, circle-to-circle amplification, helicase-dependent amplification, recombinase-dependent amplification, single-stranded binding (SSB) protein-dependent amplification, or any combination thereof.

FIG. 12C illustrates a non-limiting step of annealing a primer 1203 to the target nucleic acid 1202 to form a primed target nucleic acid 1204. FIG. 12B only shows one primer being used in the annealing step, but more than one primer can be used depending on the types of target nucleic acid. In some instances, the adapter that is used to attach the target nucleic acid to the surface has the same sequence as the primer used to prepare the primed target nucleic acid. The primer may comprise forward amplification primers, reverse amplification primers, sequencing primers, and/or molecular barcoding sequences, or any combination thereof. In some instances, one primer sequence may be used in the hybridization step. In some instances, a plurality of different primer sequences may be used in the hybridization step.

As shown in FIG. 12D, the primed target nucleic acid 1204 is combined with a multivalent binding or incorporation composition and a polymerase 1206 to form a binding or incorporation complex. The non-limiting example of a multivalent binding or incorporation composition in FIG. 12D comprises four particle-nucleotide conjugates 1205a, 1205b, 1205c, and 1205d. Each particle-nucleotide conjugate has multiple copies of a nucleotide attached to the particle, and the four particle-nucleotide conjugates cover four types of nucleotide respectively. The particle-nucleotide conjugate having a nucleotide that is complementary to the next base on the primed target nucleic acid will form a binding or incorporation complex with the polymerase and the target nucleic acid. In some instances, the multivalent binding or incorporation composition may include one, two or three particle-nucleotide conjugates. In some instances, each different type of particle-nucleotide conjugate can be labeled with a separate label. In some instances, three of four types of nucleotide conjugates can be labeled, with a fourth either unlabeled or conjugated to an undetectable label. In some instances, 1, 2, 3, or 4 particle-nucleotide conjugates can be labeled, either with the same label, or each with a label corresponding to the identity of its conjugated nucleotide, with, respectively, 3, 2, 1, or no particle-nucleotide conjugates that may be either left unlabeled or conjugated to an undetectable label. In some examples, detection of a polymerase complex incorporating a particle-nucleotide conjugate may be carried out using four-color detection, such that conjugates corresponding to all four nucleotides are present in a sample, each conjugate having a separate label corresponding to the nucleotide conjugated thereto. In some examples, the four particle-nucleotide conjugates may be exposed to or contacted with the target nucleic acid at the same time; in some other examples, the four particle-nucleotide conjugates may be exposed to or contacted with the target nucleic acid sequentially, either individually, or in groups of two or three. In some examples, detection of a polymerase complex incorporating a particle-nucleotide conjugate may be carried out using three-color detection, such that conjugates corresponding to three of the four nucleotides are present in a sample, with three conjugates having a separate label corresponding to the nucleotide conjugated thereto and one conjugate having no label or being conjugated to an undetectable label. In some examples, only three types of conjugates are provided, such that conjugates corresponding to three of the four nucleotides are present in a sample, with three conjugates having a separate label corresponding to the nucleotide conjugated thereto and one conjugate being absent. In some examples, the identity of nucleotides corresponding to an unlabeled or absent nucleotide conjugate can be determined with respect to the location and/or identity of “dark” spots or locations of known target nucleic acids showing no fluorescence signal. In some methods provided in the present disclosure, the detection of the binding or incorporation complex is performed in the absence of unbound or solution-borne polymer nucleotide conjugates.

In some examples, where three of the four particle-nucleotide conjugates are labeled, or where only three of the four particle-nucleotide conjugates are present, the identity of the nucleotide corresponding to the unlabeled or absent conjugate may be established by the absence of a signal or by monitoring of the presence of unlabeled complexes such as by the identification of “dark” spots or unlabeled regions in a sequencing reaction. In some examples, detection of a polymerase complex incorporating a particle-nucleotide conjugate may be carried out using two-color detection, such that conjugates corresponding to two of the four nucleotides are present in a sample, with two conjugates having a separate label corresponding to the nucleotide conjugated thereto and two conjugates having no label or being conjugated to an undetectable label. In some examples, only two of the four particle-nucleotide conjugates are labeled. In some examples, where two of the four particle-nucleotide conjugates are labeled, the identity of the nucleotide corresponding to the unlabeled conjugate or conjugates may be established by the absence of a signal or by monitoring of the presence of unlabeled complexes such as by the identification of “dark” spots or unlabeled regions in a sequencing reaction. In some examples, where two of the four particle-nucleotide conjugates are labeled, the four particle-nucleotide conjugates may be exposed to, or contacted with, the target nucleic acid sequentially, either individually, or in groups of two or three. In some examples, two of the four particle-nucleotide conjugates may share a common label, and the four particle-nucleotide conjugates may be exposed to or contacted with the target nucleic acid sequentially, either individually, or in groups of two or three, wherein each contacting step shows the distinction between two or more different bases, such that after two, three, four, or more such contacting steps the identities of all unknown bases have been determined.

FIG. 12E illustrates the images captured on the surface after the binding or incorporation complex is formed between the polymerase, the target nucleic acid, and the particle-nucleotide conjugate having a nucleotide commentary to the next base of the primed target nucleic acid. The captured image includes four binding or incorporation complexes 1207a, 1207b, 1207c, and 1207d formed on the surface, and each binding or incorporation complex has a different nucleotide which can be distinguished based on the label (e.g., fluorescence emission color) on the particle-nucleotide conjugate. Because use of the particle-nucleotide conjugate allows binding or incorporation signals from a given sequence to originate within cluster regions containing multiple copies of the target sequence, the sequencing signals are greatly enhanced. Although FIG. 12E involves four particle-nucleotide conjugates, each having a different type of nucleotide, some methods can use one, two, or three particle-nucleotide conjugates, each having a different type of nucleotide and label. In some examples, each different type of particle-nucleotide conjugate can be labeled either with the same label, or each with a label corresponding to the identity of its conjugated nucleotide. In some examples, three of four types of nucleotide conjugates can be labeled, with a fourth either unlabeled or conjugated to an undetectable label. In some examples, 1, 2, 3, or 4 particle-nucleotide conjugates can be labeled with a separate label, with, respectively, 3, 2, 1, or no particle-nucleotide conjugates either unlabeled or conjugated to an undetectable label. In some examples, a detection step can comprise simultaneous and/or serial excitation of up to 4 different excitation wavelengths, such as wherein the fluorescence imaging is carried out by detecting single and/or multiple fluorescence emission bands that uniquely classify each of the possible base pairings (A, G, C, or T). In some examples, four different nucleic acid binding or incorporation compositions, each comprising a different nucleotide or nucleotide analog, may be used to determine the identity of the terminal nucleotide, wherein one of the four different nucleic acid binding or incorporation compositions is labeled with a first fluorophore, one is labeled with a second fluorophore, one is labeled with both the first and second fluorophore, and one is not labeled, and wherein the detecting step comprises simultaneous excitation at a first excitation wavelength and a second excitation wavelength and images are acquired at a first fluorescence emission wavelength and a second fluorescence emission wavelength.

When the multivalent binding or incorporation composition is used in replacement of single unconjugated or untethered nucleotides to form a binding or incorporation complex with the polymerase and the primed target nucleic acid, the local concentration of the nucleotide is increased many-fold, which in turn enhances the signal intensity. The formed binding or incorporation complex also has a longer persistence time which in turn helps shorten the imaging step. The high signal intensity results from the high binding or incorporation avidity of the polymer nucleotide conjugate (which may also comprise multiple fluorophores or other labels) which thus forms a complex which remains stable for the entire binding or incorporation and imaging step. The strong binding or incorporation between the polymerase, the primed target strand, and the polymer-nucleotide or nucleotide analog conjugate also means that the multivalent binding or incorporation complex thus formed will remain stable during washing steps, and the signal intensity will remain high when other reaction mixture components and unmatched nucleotide analogs are washed away. After the imaging step, the binding or incorporation complex can be destabilized (e.g., by changing the buffer composition) and the primed target nucleic acid can then be extended for one base.

The sequencing method may further comprise incorporating the N+1 or terminal nucleotide into the primed strand as shown in FIG. 12F. In FIG. 12F, the primer strand of the primed target nucleic acid 1208 can be extended for one base to form an extended nucleic acid 1209. The extension step can occur after or concurrently with the destabilization of the multivalent binding or incorporation complex. The primed target nucleic acid 1208 can be extended using a complementary nucleotide that is attached to the particle in the particle-nucleotide conjugate or using an unconjugated or untethered free nucleotide that is provided after the multivalent binding or incorporation composition has been removed.

After the extension step, the contacting step as shown in FIG. 12G can be performed again to form binding or incorporation complexes and imitate the next sequencing cycle. The contacting, detecting, and extension steps can be repeated for one or more cycles, thereby determining the sequence of the target nucleic acid molecule. For example, FIG. 12H illustrates the surface images obtained after performing multiple sequencing cycles, and the images can then be processed to determine the sequences of the target nucleic acid molecules.

The extension of the primed target nucleic acid may be prevented or inhibited due to a blocked nucleotide on the strand or the use of polymerase that is catalytically inactive. When the nucleotide in the polymer-nucleotide conjugate has a blocking group that prevents the extension of the nucleic acid, incorporation of a nucleotide may be achieved by the removal of a blocking group from said nucleotide (such as by detachment of said nucleotide from its polymer, branched polymer, dendrimer, particle, or the like). When the extension of the primed target nucleic acid is inhibited due to the use of polymerase that is catalytically inactive, incorporation of a nucleotide may be achieved by the provision of a cofactor or activator such as a metal ion.

Also disclosed herein are systems configured for performing any of the disclosed nucleic acid sequencing or nucleic acid analysis methods. The system may comprise a fluid flow controller and/or fluid dispensing system configured to sequentially and iteratively contact the primed target nucleic acid molecules attached to a solid support with the disclosed polymerase and multivalent binding or incorporation compositions and/or reagents. The contacting may be performed within one or more flow cells. In some instances, said flow cells may be fixed components of the system. In some instances, said flow cells may be removable and/or disposable components of the system.

The sequencing system may include an imaging module, i.e., one or more light sources, one or more optical components, and one or more image sensors for imaging and detection of binding or incorporation of the disclosed nucleic acid binding or incorporation compositions to target nucleic acid molecules tethered to a solid support or the interior of a flow cell. The disclosed compositions, reagents, and methods may be used for any of a variety of nucleic acid sequencing and analysis applications. Examples include, but are not limited to, DNA sequencing, RNA sequencing, whole genome sequencing, targeted sequencing, exome sequencing, genotyping, and the like.

The sequencing system may also include computer control systems that are programmed to implement methods of the disclosure. The computer system is programmed or otherwise configured to implement methods of the disclosure including, for example, nucleic acid sequencing methods, interpretation of nucleic acid sequencing data and analysis of cellular nucleic acids, such as RNA (e.g., mRNA), or characterization of cells from sequencing data. The computer system can be an electronic device of a user or a computer system that is remotely located with respect to the electronic device. The electronic device can be a mobile electronic device.

FIG. 13 is a flowchart outlining a non-limiting example of the steps in sequencing a target nucleic acid. 1301 describes a step of attaching target library sequences to a solid support surface by hybridizing the target nucleic acid molecules to complementary adapters on a substrate surface. The target nucleic acid molecules can be single stranded or partially double stranded. Prior to 1301, the nucleic acid molecules in the target library may have been prepared to contain fragments complementary to the adaptor sequences through ligation or other methods. 1302 describes the step of clonal amplification to generate clusters of target nucleic acid molecules on the surface. 1303 describes hybridizing sequencing primers to complementary primer binding or incorporation sequences on the target nucleic acid to form the primed target nucleic acid. 1304 describes combining the polymerase, the multivalent binding or incorporation composition, which contains labeled (e.g., fluorescently-labeled) particle-nucleotide conjugates, and the primed target nucleic acid. 1304 may also include a step of washing or removing the unbound reagents including polymerase and particle-nucleotide conjugate.

Again referring to FIG. 13, when the nucleotide on the particle-nucleotide conjugate is complementary to the next base of the primed target nucleic acid (1305), the particle-nucleotide conjugate, polymerase, and primed target nucleic acid form a ternary binding or incorporation complex, which can be detected by detection methods (e.g., florescence imaging) compatible with the label on the particle-nucleotide conjugate. 1305 can also include measuring the persistence time of the ternary binding or incorporation complex. In 1306, the binding or incorporation complex is destabilized to remove the binding or incorporation of the particle-nucleotide conjugate and polymerase. The dissociation can be achieved by placing the binding or incorporation complex in a condition (e.g., adding Strontium ions) that will change the conformation of the polymerase and destabilize the binding or incorporation. 1306 may also include a step of washing or removing the dissociated particle-nucleotide conjugate and/or polymerase. 1307 describes the step of extending the primed strand of the primed target nucleic acid by a single base addition reaction. After the single base extension, steps 1304, 1305, 1306, and 1307 can be repeated in multiple cycles to determine the sequences of the target nucleic acid.

FIG. 14 is another flowchart outlining a non-limiting example of the steps in sequencing a target nucleic acid, which includes cleaving a nucleotide from the particle-nucleotide conjugate and incorporating the cleaved nucleotide. 1401 describes a step of attaching target library sequences to a solid support surface by hybridizing the target nucleic acid molecules to complementary adapters on substrate surface. The target nucleic acid molecules can be single stranded or partially double stranded. Prior to 1401, the nucleic acid molecules in the target library may have been prepared to contain fragments complementary to the adaptor sequences through ligation or other methods. 1402 describes the step of clonal amplification to generate clusters of target nucleic acid molecules on the surface. 1403 describes hybridizing sequencing primers to complementary primer binding or incorporation sequences on the target nucleic acid to form the primed target nucleic acid. 1404 describes combining the polymerase, the multivalent binding or incorporation composition, which contains labeled (e.g., fluorescently-labeled) particle-nucleotide conjugates, and the primed target nucleic acid. In the particle-nucleotide conjugates, the nucleotides are attached to the particle through chemical bonds or interactions that can be later severed. 1404 may also include a step of washing or removing the unbound reagents including polymerase and particle-nucleotide conjugate.

Again referring to FIG. 14, when the nucleotide on the particle-nucleotide conjugate is complementary to the next base of the primed target nucleic acid (1405), the particle-nucleotide conjugate, polymerase, and primed target nucleic acid form a ternary binding or incorporation complex, which can be detected by detection methods (e.g., florescence imaging) compatible with the label on the particle-nucleotide conjugate. 1405 can also include measuring the persistence time of the ternary binding or incorporation complex. In 1406, the polymerase is placed in a condition that would make it catalytically active to incorporate a nucleotide. The condition can include exposing the polymerase to Mg or Mn ions in the reaction solution. The nucleotide that is bound to the polymerase and the primed target nucleic acid is then cleaved from the particle and then incorporated into the primed strand of the primed target nucleic acid. The binding or incorporation complex is destabilized. 1406 may also include a step of washing or removing the dissociated particle-nucleotide conjugate and/or polymerase. After the extension, steps 1404, 1405, and 1406 can be repeated in multiple cycles to determine the sequences of the target nucleic acid.

Detecting Target Nucleic Acid Molecules. FIGS. 15A-15B illustrate one exemplified method in which the multivalent binding or incorporation composition is used for detecting a target nucleic acid. As shown in FIG. 15A, the polymer-nucleotide conjugate 1501 is placed in contact with polymerase 1506, a first nucleic acid molecule 1504, and a second nucleic acid molecule 1505. The polymer-nucleotide conjugate 1501 has multiple polymer branches radiating from the core, and some branches are attached to a nucleotide or oligonucleotide 1502, and some branches are attached to a label 1503. When the nucleotide or oligonucleotide 1502 on the polymer-nucleotide conjugate 1501 is complementary to at least a fraction of the first nucleic acid 1504, a multivalent binding or incorporation complex is formed as shown in FIG. 15B, and the strong binding or incorporation signal can help detect target nucleic acid with sequences complementary or partially complementary to the nucleotide or oligonucleotide on the polymer-nucleotide conjugate. In some instances, at least one of the polymerase, nucleic acid molecules, and polymer-nucleotide conjugates is attached to a solid support.

The multivalent binding or incorporation composition described herein can be used in a method of detecting a target nucleic acid in a sample. Also disclosed herein are systems configured for performing any of the disclosed nucleic acid analysis methods. The systems may comprise a fluid flow controller and/or fluid dispensing system configured to sequentially and iteratively contact the nucleic acid molecules with the disclosed polymerase and multivalent binding or incorporation compositions and/or reagents. The contacting may be performed within one or more flow cells. In some instances, said flow cells may be fixed components of the system. In some instances, said flow cells may be removable and/or disposable components of the system. The system may also include a cartridge comprising a sample collection unit and an assay assembly, wherein the sample collection unit is configured to collect a sample, and wherein the assay assembly comprises at least one reaction site containing a multivalent binding or incorporation composition adapted to interact with said analyte, allowing the predetermined portion of sample to react with assay reagents contained within the assay assembly to yield a signal indicative of the presence of the analyte in the sample, and detecting the signal generated from the analyte.

Multivalent Binding or incorporation Composition. The present disclosure relates to multivalent binding or incorporation compositions having a plurality of nucleotides conjugated to a particle (e.g., a polymer, branched polymer, dendrimer, or equivalent structure). Contacting the multivalent binding or incorporation composition with a polymerase and multiple copies of a primed target nucleic acid may result in the formation of a ternary complex which may be detected and in turn achieve a more accurate determination of the bases of the target nucleic acid.

When the multivalent binding or incorporation composition is used in replacement of a single unconjugated or untethered nucleotide to form a complex with the polymerase and one or more copies of the target nucleic acid, the local concentration of the nucleotide as well as the binding avidity of the complex (in the case that a complex comprising two or more target nucleic acid molecules is formed) is increased many fold, which in turn enhances the signal intensity, particularly the correct signal versus mismatch. The multivalent binding or incorporation composition described herein can include at least one particle-nucleotide conjugate (each particle-nucleotide conjugate comprising multiple copies of a single nucleotide moiety) for interacting with the target nucleic acid. The multivalent composition can also include two, three, or four different particle-nucleotide conjugates, each having a different nucleotide conjugated to the particle.

The multivalent binding or incorporation composition can comprise 1, 2, 3, 4, or more types of particle-nucleotide conjugates, wherein each particle-nucleotide conjugate comprises a different type of nucleotide. A first type of the particle-nucleotide conjugate can comprise a nucleotide selected from the group consisting of ATP, ADP, AMP, dATP, dADP, and dAMP. A second type of the particle-nucleotide conjugate can comprise a nucleotide selected from the group consisting of TTP, TDP, TMP, dTTP, dTDP, dTMP, UTP, UDP, UMP, dUTP, dUDP, and dUMP. A third type of the particle-nucleotide conjugate can comprise a nucleotide selected from the group consisting of CTP, CDP, CMP, dCTP, dCDP, and dCMP. A fourth type of the particle-nucleotide conjugate can comprise a nucleotide selected from the group consisting of GTP, GDP, GMP, dGTP, dGDP, and dGMP. In some instances, each particle-nucleotide conjugate comprises a single type of nucleotide respectively corresponding to one or more nucleotides selected from the group consisting of ATP, ADP, AMP, dATP, dADP, dAMP TTP, TDP, TMP, dTTP, dTDP, dTMP, UTP, UDP, UMP, dUTP, dUDP, dUMP, CTP, CDP, dCTP, dCDP, dCMP, GTP, GDP, GMP, dGTP, dGDP, and dGMP. Each multivalent binding or incorporation composition may further comprise one or more labels corresponding to the particular nucleotide conjugated to each respective conjugate. Non-limiting examples of labels include fluorescent labels, colorimetric labels, electrochemical labels (such as, for example, glucose or other reducing sugars, or thiols or other redox active moieties), luminescent labels, chemiluminescent labels, spin labels, radioactive labels, steric labels, affinity tags, or the like.

Particle-Nucleotide Conjugate. In a particle-nucleotide conjugate, multiple copies of the same nucleotide may be covalently bound to or noncovalently bound to the particle. Examples of the particle can include a branched polymer; a dendrimer; a cross linked polymer particle such as an agarose, polyacrylamide, acrylate, methacrylate, cyanoacrylate, methyl methacrylate particle; a glass particle; a ceramic particle; a metal particle; a quantum dot; a liposome; an emulsion particle, or any other particle (e.g, nanoparticles, microparticles, or the like) known in the art. In one example, the particle is a branched polymer.

In some instances, the particle-nucleotide conjugate (e.g., a polymer-nucleotide conjugate) may comprise 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 10 copies of a nucleotide, nucleotide analog, nucleoside, or nucleoside analog tethered to the particle.

The nucleotide can be linked to the particle through a linker, and the nucleotide can be attached to one end or location of the polymer. The nucleotide can be conjugated to the particle through the 5′ end of the nucleotide. In some particle-nucleotide conjugates, one nucleotide is attached to one end or location of a polymer. In some particle-nucleotide conjugate, multiple nucleotides are attached to one end or location of a polymer. The conjugated nucleotide is sterically accessible to one or more proteins, one or more enzymes, and nucleotide binding or incorporation moieties. In some examples, a nucleotide may be provided separately from a nucleotide binding or incorporation moiety such as a polymerase. In some examples, the linker does not comprise a photo emitting or photo absorbing group.

The particle can also have a binding or incorporation moiety. In some examples, particles may self-associate without the use of a separate interaction moiety. In some examples, particles may self-associate due to buffer conditions or salt conditions, e.g., as in the case of calcium-mediated interactions of hydroxyapatite particles, lipid or polymer mediated interactions of micelles or liposomes, or salt-mediated aggregation of metallic (such as iron or gold) nanoparticles.

The particle-nucleotide conjugate can have one or more labels. Examples of the labels include, but are not limited to, fluorophores, spin labels, metals or metal ions, colorimetric labels, nanoparticles, PET labels, radioactive labels, or other such labels as may render said composition detectable by such methods as are known in the art of the detection of macromolecules or molecular interactions. The label may be attached to the nucleotide (e.g., by attachment to the 5′ phosphate moiety of a nucleotide), to the particle itself (e.g., to the PEG subunits), to an end of the polymer, to a central moiety, or to any other location within said polymer-nucleotide conjugate which would be recognized by one of skill in the art to be sufficient to render said composition, such as a particle, detectable by such methods as are known in the art or described elsewhere herein. In some examples, one or more labels are provided so as to correspond to or differentiate a particular particle-nucleotide conjugate.

In some examples, the label is a fluorophore. Non-limiting examples of fluorescent moieties include, but are not limited to, fluorescein and fluorescein derivatives such as carboxyfluorescein, tetrachlorofluorescein, hexachlorofluorescein, carboxynapthofluorescein, fluorescein isothiocyanate, NHS-fluorescein, iodoacetamidofluorescein, fluorescein maleimide, SAMSA-fluorescein, fluorescein thiosemicarbazide, carbohydrazinomethylthioacetyl-amino fluorescein, rhodamine and rhodamine derivatives such as TRITC, TMR, lissamine rhodamine, Texas Red, rhodamine B, rhodamine 6G, rhodamine 10, NHS-rhodamine, TMR-iodoacetamide, lissamine rhodamine B sulfonyl chloride, lissamine rhodamine B sulfonyl hydrazine, Texas Red sulfonyl chloride, Texas Red hydrazide, coumarin and coumarin derivatives such as AMCA, AMCA-NHS, AMCA-sulfo-NHS, AMCA-HPDP, DCIA, AMCE-hydrazide, BODIPY and derivatives such as BODIPY FL C3-SE, BODIPY 530/550 C3, BODIPY 530/550 C3-SE, BODIPY 530/550 C3 hydrazide, BODIPY 493/503 C3 hydrazide, BODIPY FL C3 hydrazide, BODIPY FL IA, BODIPY 530/551 IA, Br-BODIPY 493/503, Cascade Blue and derivatives such as Cascade Blue acetyl azide, Cascade Blue cadaverine, Cascade Blue ethylenediamine, Cascade Blue hydrazide, Lucifer Yellow and derivatives such as Lucifer Yellow iodoacetamide, Lucifer Yellow CH, cyanine and derivatives such as indolium based cyanine dyes, benzo-indolium based cyanine dyes, pyridium based cyanine dyes, thiozolium based cyanine dyes, quinolinium based cyanine dyes, imidazolium based cyanine dyes, Cy 3, Cy5, lanthanide chelates and derivatives such as BCPDA, TBP, TMT, BHHCT, BCOT, Europium chelates, Terbium chelates, Alexa Fluor dyes, DyLight dyes, Atto dyes, LightCycler Red dyes, CAL Flour dyes, JOE and derivatives thereof, Oregon Green dyes, WellRED dyes, IRD dyes, phycoerythrin and phycobilin dyes, Malachite green, stilbene, DEG dyes, NR dyes, near-infrared dyes and others known in the art such as those described in Haugland, Molecular Probes Handbook, (Eugene, Oreg.) 6th Edition; Lakowicz, Principles of Fluorescence Spectroscopy, 2nd Ed., Plenum Press New York (1999), or Hermanson, Bioconjugate Techniques, 2nd Edition, or derivatives thereof, or any combination thereof. Cyanine dyes may exist in either sulfonated or non-sulfonated forms, and consist of two indolenin, benzo-indolium, pyridium, thiozolium, and/or quinolinium groups separated by a polymethine bridge between two nitrogen atoms. Commercially available cyanine fluorophores include, for example, Cy3, (which may comprise 1-[6-(2,5-dioxopyrrolidin-1-yloxy)-6-oxohexyl]-2-(3-{1-[6-(2,5-dioxopyrrolidin-1-yloxy)-6-oxohexyl]-3,3-dimethyl-1,3-dihydro-2H-indol-2-ylidene}prop-1-en-1-yl)-3,3-dimethyl-3H-indolium or 1-[6-(2,5-dioxopyrrolidin-1-yloxy)-6-oxohexyl]-2-(3-{1-[6-(2,5-dioxopyrrolidin-1-yloxy)-6-oxohexyl]-3,3-dimethyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene}prop-1-en-1-yl)-3,3-dimethyl-3H-indolium-5-sulfonate), Cy5 (which may comprise 1-(6-((2,5-dioxopyrrolidin-1-yl)oxy)-6-oxohexyl)-2-((1E,3E)-5-((E)-1-(6-((2,5-dioxopyrrolidin-1-yl)oxy)-6-oxohexyl)-3,3-dimethyl-5-indolin-2-ylidene)penta-1,3-dien-1-yl)-3,3-dimethyl-3H-indol-1-ium or 1-(6-((2,5-dioxopyrrolidin-1-yl)oxy)-6-oxohexyl)-2-((1E,3E)-5-((E)-1-(6-((2,5-dioxopyrrolidin-1-yl)oxy)-6-oxohexyl)-3,3-dimethyl-5-sulfo indolin-2-ylidene)penta-1,3-dien-1-yl)-3,3-dimethyl-3H-indol-1-ium-5-sulfonate), and Cy7 (which may comprise 1-(5-carboxypentyl)-2-[(1E,3E,5E,7Z)-7-(1-ethyl-1,3-dihydro-2H-indol-2-ylidene)hepta-1,3,5-trien-1-yl]-3H-indolium or 1-(5-carboxypentyl)-2-[(1E,3E,5E,7Z)-7-(1-ethyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene)hepta-1,3,5-trien-1-yl]-3H-indolium-5-sulfonate), where “Cy” stands for ‘cyanine’, and the first digit identifies the number of carbon atoms between two indolenine groups. Cy2, which is an oxazole derivative rather than indolenin, and the benzo-derivatized Cy3.5, Cy5.5 and Cy7.5 are exceptions to this rule.

In some embodiments, the detection label can be a FRET pair, such that multiple classifications can be performed under a single excitation and imaging step. As used herein, FRET may comprise excitation exchange (Forster) transfers, or electron-exchange (Dexter) transfers.

Polymer Nucleotide Conjugate. One example of the particle-nucleotide conjugate is a polymer-nucleotide conjugate. Some non-limiting examples of the polymer-nucleotide conjugates are shown in FIGS. 16A-16C. For example, FIG. 16A shows polymer-nucleotide conjugates having various configurations, e.g., a “starburst” configuration comprising a fluorescently-labeled streptavidin core and four nucleotides bound to the core via biotinylated, linear PEG linkers of molecular weight ranging from 1K Dalton to 10K Daltons; FIG. 16B shows a polymer-nucleotide conjugate having a dendrimer core of, for example, 12, 24, 48, or 96 arms, and linear PEG linkers of molecular weight ranging from 1K Dalton to 10K Daltons radiating from the center; and FIG. 16C shows an example of polymer-nucleotide conjugates comprising a network of, e.g., streptavidin cores, linked together by branched PEG linkers comprising a binding or incorporation moiety such as a biotin.

Examples of suitable linear or branched polymers include linear or branched polyethylene glycol (PEG), linear or branched polypropylene glycol, linear or branched polyvinyl alcohol, linear or branched polylactic acid, linear or branched polyglycolic acid, linear or branched polyglycine, linear or branched polyvinyl acetate, a dextran, or other such polymers, or copolymers incorporating any two or more of the foregoing or incorporating other polymers as are known in the art. In one example, the polymer is a PEG. In another embodiment, the polymer can have PEG branches.

Suitable polymers may be characterized by a repeating unit incorporating a functional group suitable for derivatization such as an amine, a hydroxyl, a carbonyl, or an allyl group. The polymer can also have one or more pre-derivatized substituents such that one or more particular subunits will incorporate a site of derivatization or a branch site, whether or not other subunits incorporate the same site, substituent, or moiety. A pre-derivatized substituent may comprise or may further comprise, for example, a nucleotide, a nucleoside, a nucleotide analog, a label such as a fluorescent label, radioactive label, or spin label, an interaction moiety, an additional polymer moiety, or the like, or any combination of the foregoing.

In the polymer-nucleotide conjugate, the polymer can have a plurality of branches. The branched polymer can have various configurations, including, but not limited to, stellate (“starburst”) forms, aggregated stellate (“helter skelter”) forms, bottle brush, or dendrimer. The branched polymer can radiate from a central attachment point or central moiety, or may incorporate multiple branch points, such as, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more branch points. In some instances, each subunit of a polymer may optionally constitute a separate branch point.

The length and size of the branch can differ based on the type of polymer. In some branched polymers, the branch may have a length of between 1 and 1,000 nm, between 1 and 100 nm, between 1 and 200 nm, between 1 and 300 nm, between 1 and 400 nm, between 1 and 500 nm, between 1 and 600 nm, between 1 and 700 nm, between 1 and 800 nm, or between 1 and 900 nm, or more, or may have a length falling within or between any of the values disclosed herein.

In some polymer-nucleotide conjugates, the polymer core may have a size corresponding to an apparent molecular weight of 1K Da, 2K Da, 3K Da, 4K Da, 5K Da, 10K Da, 15K Da, 20K Da, 30K Da, 50K Da, 80K Da, 100K Da, or any value within a range defined by any two of the foregoing. The apparent molecular weight of a polymer may be calculated from the known molecular weight of a representative number of subunits, as determined by size exclusion chromatography, as determined by mass spectrometry, or as determined by any other method as is known in the art.

In some branched polymers, the branch may have a size corresponding to an apparent molecular weight of 1K Da, 2K Da, 3K Da, 4K Da, 5K Da, 10K Da, 15K Da, 20K Da, 30K Da, 50K Da, 80K Da, 100K Da, or any value within a range defined by any two of the foregoing. The apparent molecular weight of a polymer may be calculated from the known molecular weight of a representative number of subunits, as determined by size exclusion chromatography, as determined by mass spectrometry, or as determined by any other method as is known in the art. The polymer can have multiple branches. The number of branches in the polymer can be 2, 3, 4, 5, 6, 7, 8, 12, 16, 24, 32, 64, 128 or more, or a number falling within a range defined by any two of these values.

For polymer-nucleotide conjugates comprising a branched polymer of, for example, a branched PEG comprising 4, 8, 16, 32, or 64 branches, the polymer nucleotide conjugate can have nucleotides attached to the ends of the PEG branches, such that each end has attached thereto 0, 1, 2, 3, 4, 5, 6 or more nucleotides. In one non-limiting example, a branched PEG polymer of between 3 and 128 PEG arms may have attached to the ends of the polymer branches one or more nucleotides, such that each end has attached thereto 0, 1, 2, 3, 4, 5, 6 or more nucleotides or nucleotide analogs. In some embodiments, a branched polymer or dendrimer has an even number of arms. In some embodiments, a branched polymer or dendrimer has an odd number of arms.

In some instances, the length of the linker (e.g., a PEG linker) may range from about 1 nm to about 1,000 nm. In some instances, the length of the linker may be at least 1 nm, at least 10 nm, at least 25 nm, at least 50 nm, at least 75 nm, at least 100 nm, at least 200 nm, at least 300 nm, at least 400 nm, at least 500 nm, at least 600 nm, at least 700 nm, at least 800 nm, at least 900 nm, or at least 1,000 nm. In some instances, the length of the linker may range between any two of the values in this paragraph. For example, in some instances, the length of the linker may range from about 75 nm to about 400 nm. Those of skill in the art will recognize that in some instances, the length of the linker may have any value within the range of values in this paragraph, e.g., 834 nm.

In some instances, the length of the linker is different for different nucleotides (including deoxyribonucleotides and ribonucleotides), nucleotide analogs (including deoxyribonucleotide analogs and ribonucleotide analogs), nucleosides (including deoxyribonucleosides or ribonucleosides), or nucleoside analogs (including deoxyribonucleoside analogs or ribonucleoside analogs). In some instances, one of the nucleotides, nucleotide analogs, nucleosides, or nucleoside analogs comprises, for example, deoxyadenosine, and the length of the linker is between 1 nm and 1,000 nm. In some instances, one of the nucleotides, nucleotide analogs, nucleosides, or nucleoside analogs comprises, for example, deoxyguanosine, and the length of the linker is between 1 nm and 1,000 nm. In some instances, one of the nucleotides, nucleotide analogs, nucleosides, or nucleoside analogs comprises, for example, thymidine, and the length of the linker is between 1 nm and 1,000 nm. In some instances, one of the nucleotides, nucleotide analogs, nucleosides, or nucleoside analogs comprises, for example, comprises deoxyuridine, and the length of the linker is between 1 nm and 1,000 nm. In some instances, one of the nucleotides, nucleotide analogs, nucleosides, or nucleoside analogs comprises, for example, deoxycytidine, and the length of the linker is between 1 nm and 1,000 nm. In some instances, one of the nucleotides, nucleotide analogs, nucleosides, or nucleoside analogs comprises, for example, adenosine, and the length of the linker is between 1 nm and 1,000 nm. In some instances, one of the nucleotides, nucleotide analogs, nucleosides, or nucleoside analogs comprises, for example, guanosine, and the length of the linker is between 1 and 1,000 nm. In some instances, one of the nucleotides, nucleotide analogs, nucleosides, or nucleoside analogs comprises, for example, 5-methyl-uridine, and the length of the linker is between 1 nm and 1,000 nm. In some instances, one of the nucleotides, nucleotide analogs, nucleosides, or nucleoside analogs comprises, for example, uridine, and the length of the linker is between 1 nm and 1,000 nm. In some instances, one of the nucleotides, nucleotide analogs, nucleosides, or nucleoside analogs comprises, for example, cytidine, and the length of the linker is between 1 nm and 1,000 nm.

In the polymer-nucleotide conjugate, each branch or a subset of branches of the polymer may have attached thereto a moiety comprising a nucleotide (e.g., an adenine, a thymine, a uracil, a cytosine, or a guanine residue or a derivative or mimetic thereof), and the moiety is capable of binding or incorporation to a polymerase, reverse transcriptase, or other nucleotide binding or incorporation domain. Optionally, the moiety may be capable of being incorporated into an elongating nucleic acid chain during a polymerase reaction. In some instances, said moiety may be blocked such that it is not capable of being incorporated into an elongating nucleic acid chain during a polymerase reaction. In some other instances, said moiety may be reversibly blocked such that it is not capable of being incorporated into an elongating nucleic acid chain during a polymerase reaction until such block is removed, after which said moiety is then capable of being incorporated into an elongating nucleic acid chain during a polymerase reaction.

The nucleotide can be conjugated to the polymer branch through the 5′ end of the nucleotide. In some instances, the nucleotide may be modified so as to inhibit or prevent incorporation of the nucleotide into an elongating nucleic acid chain during a polymerase reaction. By way of example, the nucleotide may include a 3′ deoxyribonucleotide, a 3′ azidonucleotide, a 3′-methyl azido nucleotide, or another such nucleotide as is or may be known in the art, so as to not be capable of being incorporated into an elongating nucleic acid chain during a polymerase reaction. In some instances, the nucleotide can include a 3′-O-azido group, a 3′-O-azidomethyl group, a 3′-phosphorothioate group, a 3′-O-malonyl group, a 3′-O-alkyl hydroxylamino group, or a 3′-O-benzyl group. In some instances, the nucleotide lacks a 3′ hydroxyl group.

The polymer can further have a binding or incorporation moiety in each branch or a subset of branches. Some examples of the binding or incorporation moiety include but are not limited to biotin, avidin, strepavidin or the like, polyhistidine domains, complementary paired nucleic acid domains, G-quartet forming nucleic acid domains, calmodulin, maltose-binding protein, cellulase, maltose, sucrose, glutathione-S-transferase, glutathione, O-6-methylguanine-DNA methyltransferase, benzylguanine and derivatives thereof, benzylcysteine and derivatives thereof, an antibody, an epitope, a protein A, a protein G. The binding or incorporation moiety can be any interactive molecules or fragment thereof known in the art to bind to or facilitate interactions between proteins, between proteins and ligands, between proteins and nucleic acids, between nucleic acids, or between small molecule interaction domains or moieties.

In some embodiments, a composition as provided herein may comprise one or more elements of a complementary interaction moiety. Non-limiting examples of complementary interaction moieties include, for example, biotin and avidin; SNAP-benzylguanosine; antibody or FAB and epitope; IgG FC and Protein A, Protein G, ProteinA/G, or Protein L; maltose binding protein and maltose; lectin and cognate polysaccharide; ion chelation moieties, complementary nucleic acids, nucleic acids capable of forming triplex or triple helical interactions; nucleic acids capable of forming G-quartets, and the like. One of skill in the art will readily recognize that many pairs of moieties exist and are commonly used for their property of interacting strongly and specifically with one another; and thus any such complementary pair or set is considered to be suitable for this purpose in constructing or envisioning the compositions of the present disclosure. In some examples, a composition as disclosed herein may comprise compositions in which one element of a complementary interaction moiety is attached to one molecule or multivalent ligand, and the other element of the complementary interaction moiety is attached to a separate molecule or multivalent ligand. In some examples, a composition as disclosed herein may comprise compositions in which both or all elements of a complementary interaction moiety are attached to a single molecule or multivalent ligand. In some examples, a composition as disclosed herein may comprise compositions in which both or all elements of a complementary interaction moiety are attached to separate arms of, or locations on, a single molecule or multivalent ligand. In some examples, a composition as disclosed herein may comprise compositions in which both or all elements of a complementary interaction moiety are attached to the same arm of, or locations on, a single molecule or multivalent ligand. In some examples, compositions comprising one element of a complementary interaction moiety and compositions comprising another element of a complementary interaction moiety may be simultaneously or sequentially mixed. In some examples, interactions between molecules or particles as disclosed herein allow for the association or aggregation of multiple molecules or particles such that, for example, detectable signals are increased. In some examples, fluorescent, colorimetric, or radioactive signals are enhanced. In other examples, other interaction moieties as disclosed herein, or as are known in the art, are contemplated. In some examples, a composition as provided herein may be provided such that one or more molecules comprising a first interaction moiety such as, for example, one or more imidazole or pyridine moieties, and one or more additional molecules comprising a second interaction moiety such as, for example, histidine residues, are simultaneously or sequentially mixed. In some examples, said composition comprises 1, 2, 3, 4, 5, 6, or more imidazole or pyridine moieties. In some examples, said composition comprises 1, 2, 3, 4, 5, 6, or more histidine residues. In such examples, interaction between the molecules or particles as provided may be facilitated by the presence of a divalent cation such as nickel, manganese, magnesium, calcium, strontium, or the like. For example, a (His)3 group may interact with a (His)3 group on another molecule or particle via coordination of a nickel or manganese ion.

The multivalent binding or incorporation composition may comprise one or more buffers, salts, ions, or additives. Representative additives may include, but are not limited to, betaine, spermidine, detergents such as Triton X-100, Tween 20, SDS, or NP-40, ethylene glycol, polyethylene glycol, dextran, polyvinyl alcohol, vinyl alcohol, methylcellulose, heparin, heparan sulfate, glycerol, sucrose, 1,2-propanediol, DMSO, N,N,N-trimethylglycine, ethanol, ethoxyethanol, propylene glycol, polypropylene glycol, block copolymers such as the Pluronic® series polymers, arginine, histidine, imidazole, or any combination thereof, or any substance known in the art as a DNA “relaxer” (i.e., a compound, with the effect of altering the persistence length of DNA, altering the number of within-polymer junctions or crossings, or altering the conformational dynamics of a DNA molecule such that the accessibility of sites within the strand to DNA binding or incorporation moieties is increased).

The multivalent binding or incorporation composition may include zwitterionic compounds as additives. Further representative additives may be found in Lorenz, T. C. J. Vis. Exp. (63), e3998, doi:10.3791/3998 (2012), which is hereby incorporated by reference with respect to its disclosure of additives for the facilitation of nucleic acid binding or dynamics, or the facilitation of processes involving the manipulation, use, or storage of nucleic acids. In some instances, representative cations include, but are not limited to, sodium, magnesium, strontium, potassium, manganese, calcium, lithium, nickel, cobalt, or other such cations as are known in the art to facilitate nucleic acid interactions, such as self-association, secondary or tertiary structure formation, base pairing, surface association, peptide association, protein binding, or the like.

Binding Between Target Nucleic Acid and Multivalent Binding or Incorporation Composition. When the multivalent binding or incorporation composition is used in replacement of a single unconjugated or untethered nucleotide to form a complex with the polymerase and one or more copies of the target nucleic acid, the local concentration of the nucleotide as well as the binding avidity of the complex (in cases where a complex comprising two or more target nucleic acid molecules is formed) is increased many-fold, which in turn enhances the signal intensity, particularly the correct signal versus mismatch. The present disclosure contemplates contacting the multivalent binding or incorporation composition with a polymerase and a primed target nucleic acid to determine the formation of a ternary binding or incorporation complex.

FIG. 17 illustrates the use of the disclosed polymer-nucleotide conjugates for achieving increased signal intensity during binding, persistence, and washing/removal steps. Because of the increased local concentration of the nucleotide on the polymer-nucleotide conjugate and/or the formation of non-covalent bonds with two or more primed target nucleic acid molecules, the binding between the polymerase, the primed target strand, and the polymer-conjugated nucleotide, when the nucleotide is complementary to the next base of the target nucleic acid, becomes more favorable. The formed binding complex has a longer persistence time, which in turn helps increase signal and shorten the imaging step. The high signal intensity resulting from the use of the disclosed polymer nucleotide conjugates remains stable for the entire binding and imaging steps. The strong binding between the polymerase, the primed target strand, and the polymer-conjugated nucleotide or nucleotide analog also means that the binding complex thus formed will remain stable during wash steps as other reaction mixture components and unmatched nucleotide analogs are washed away. After the imaging step, the binding complex can be destabilized (e.g., by changing the buffer composition) and the primed target nucleic acid can then be extended for one base. After the extension, the binding and imaging steps can be repeated with the use of the disclosed polymer nucleotide conjugates to determine the identity of the next base.

As an example, a graphical depiction of the increase in signal intensity during binding, persistence, and washing/removal of a multivalent substrate as described herein is provided in FIG. 17, which is representative of the changes in signal intensity that have been observed experimentally. Therefore, the compositions and methods of the present disclosure provide a robust and controllable means of establishing and maintaining a ternary enzyme complex, as well as providing vastly improved means by which the presence of said complex may be identified and/or measured, and a means by which the persistence of said complex may be controlled. This provides important solutions to problems such as that of determining the identity of the N+1 base in nucleic acid sequencing applications.

Without intending to be bound by any particular theory, it has been observed that multivalent binding compositions disclosed herein associate with polymerase nucleotide complexes in order to form a ternary binding complexes with a rate that is time-dependent, though substantially slower than the rate of association known to be obtainable by nucleotides in free solution. Thus, the on-rate (Kon) is substantially and surprisingly slower than the on rate for single nucleotides or nucleotides not attached to multivalent ligand complexes. Importantly, however, the off rate (Koff) of the multivalent ligand complex is substantially slower than that observed for nucleotides in free solution. Therefore, the multivalent ligand complexes of the present disclosure provide a surprising and beneficial improvement of the persistence of ternary polymerase-polynucleotide-nucleotide complexes (especially over such complexes that are formed with free nucleotides) allowing, for example, significant improvements in imaging quality for nucleic acid sequencing applications over currently available methods and reagents. Importantly, this property of the multivalent binding compositions disclosed herein renders the formation of visible ternary complexes controllable, such that subsequent visualization, modification, or processing steps may be undertaken essentially without regard to the dissociation of the complex—that is, the complex can be formed, imaged, modified, or used in other ways as necessary, and will remain stable until a user carries out an affirmative dissociation step, such as exposing the complexes to a dissociation buffer.

In some instances, the persistence times for the multivalent binding complexes formed using the disclosed particle-nucleotide or polymer-nucleotide conjugates may range from about 0.1 second to about 600 second under non-destabilizing conditions. In some instances, the persistence time may be at least 0.1 second, at least 1 second, at least 2 seconds, at least 3 second, at least 4 second, at least 5 seconds, at least 6 seconds, at least 7 seconds, at least 8 seconds, at least 9 seconds, at least 10 seconds, at least 20 seconds, at least 30 second, at least 40 second, at least 50 seconds, at least 60 seconds, at least 120 seconds, at least 180 seconds, at least 240 seconds, at least 300 seconds, at least 360 seconds, at least 420 seconds, at least 480 seconds, at least 540 seconds, or at least 600 seconds. In some instances, the persistence time may range between any two of the values specified in this paragraph. For example, in some instances, the persistence time may range from about 10 seconds to about 360 seconds. Those of skill in the art will recognize that in some instances, the persistence time may have any value within the range of values specified in this paragraph, e.g., 78 seconds.

In various examples, polymerases suitable for the binding or incorporation interaction describe herein include may include any polymerase as is or may be known in the art. It is, for example, known that every organism encodes within its genome one or more DNA polymerases. Examples of suitable polymerases may include but are not limited to: Klenow DNA polymerase, Thermus aquaticus DNA polymerase I (Taq polymerase), KlenTaq polymerase, and bacteriophage T7 DNA polymerase; human alpha, delta and epsilon DNA polymerases; bacteriophage polymerases such as T4, RB69 and phi29 bacteriophage DNA polymerases, Pyrococcus furiosus DNA polymerase (Pfu polymerase); Bacillus subtilis DNA polymerase III, and E. coli DNA polymerase III alpha and epsilon; 9 degree N polymerase, reverse transcriptases such as HIV type M or O reverse transcriptases, avian myeloblastosis virus reverse transcriptase, or Moloney Murine Leukemia Virus (MMLV) reverse transcriptase, or telomerase. Further non-limiting examples of DNA polymerases can include those from various Archaea genera, such as, Aeropyrum, Archaeglobus, Desulfurococcus, Pyrobaculum, Pyrococcus, Pyrolobus, Pyrodictium, Staphylothermus, Stetteria, Sulfolobus, Thermococcus, and Vulcanisaeta and the like or variants thereof, including such polymerases as are known in the art such as Vent™, Deep Vent™, Pfu, KOD, Pfx, Therminator™, and Tgo polymerases. In some examples, the polymerase is a klenow polymerase.

The ternary complex has longer persistence time when the nucleotide on the polymer-nucleotide conjugate is complementary to the target nucleic acid than when it is non-complementary to the target nucleic acid. The ternary complex also has longer persistence time when the nucleotide on the polymer-nucleotide conjugate is complementary to the target nucleic acid than a complementary nucleotide that is not conjugated or tethered. For example, in some embodiments, said ternary complexes may have a persistence time of less than 1 s, greater than 1 s, greater than 2 s, greater than 3 s, greater than 5 s, greater than 10 s, greater than 15 s, greater than 20 s, greater than 30 s, greater than 60 s, greater than 120 s, greater than 360 s, greater than 3600 s, or more, or for a time lying within a range defined by any two or more of these values.

The persistence time can be measured, for example, by observing the onset and/or duration of a binding complex, such as by observing a signal from a labeled component of the binding complex. For example, a labeled nucleotide or a labeled reagent comprising one or more nucleotides may be present in a binding complex, thus allowing the signal from the label to be detected during the persistence time of the binding complex.

It has been observed that different ranges of persistence times are achievable with different salts or ions, showing, for example, that complexes formed in the presence of, for example, magnesium ions (Mg2+) form more quickly than complexes formed with other ions. It has also been observed that complexes formed in the presence of, for example, strontium ions (Sr2+), form readily and dissociate completely or with substantial completeness upon withdrawal of the ion or upon washing with buffer lacking one or more components of the present compositions, such as, e.g., a polymer and/or one or more nucleotides, and/or one or more interaction moieties, or a buffer containing, for example, a chelating agent which may cause or accelerate the removal of a divalent cation from the multivalent reagent containing complex. Thus, in some examples, a composition of the present disclosure comprises Mg2+. In some examples, a composition of the present disclosure comprises Ca2+. In some examples, a composition of the present disclosure comprises Sr2+. In some examples, a composition of the present disclosure comprises cobalt ions (Co2+). In some examples, a composition of the present disclosure comprises MgCl2. In some examples, a composition of the present disclosure comprises CaCl2. In some examples, a composition of the present disclosure comprises SrCl2. In some examples, a composition of the present disclosure comprises CoCl2. In some examples, the composition comprises no, or substantially no magnesium. In some examples, the composition comprises no, or substantially no calcium. In some examples, the methods of the present disclosure provide for the contacting of one or more nucleic acids with one or more of the compositions disclosed herein, wherein said composition lacks either one of calcium or magnesium or lacks both calcium or magnesium.

The dissociation of ternary complexes can be controlled by changing the buffer conditions. After the imaging step, a buffer with increased salt content is used to cause dissociation of the ternary complexes such that labeled polymer-nucleotide conjugates can be washed out, providing a means by which signals can be attenuated or terminated, such as in the transition between one sequencing cycle and the next. This dissociation may be affected, in some embodiments, by washing the complexes with a buffer lacking a necessary metal or cofactor. In some instances, a wash buffer may comprise one or more compositions for the purpose of maintaining pH control. In some instances, a wash buffer may comprise one or more monovalent cations, such as sodium. In some instances, a wash buffer lacks or substantially lacks a divalent cation, for example, having no or substantially no strontium, calcium, magnesium, or manganese. In some instances, a wash buffer further comprises a chelating agent, such as, for example, EDTA, EGTA, nitrilotriacetic acid, polyhistidine, imidazole, or the like. In some instances, a wash buffer may maintain the pH of the environment at the same level as for the bound complex. In some instances, a wash buffer may raise or lower the pH of the environment relative to the level seen for the bound complex. In some instances, the pH may be within a range from 2-4, 2-7, 5-8, 7-9, 7-10, or lower than 2, or higher than 10, or a range defined by any two of the values provided herein.

Addition of a particular ion may affect the binding of the polymerase to a primed target nucleic acid, the formation of a ternary complex, the dissociation of a ternary complex, or the incorporation of one or more nucleotides into an elongating nucleic acid such as during a polymerase reaction. In some instances, relevant anions may comprise chloride, acetate, gluconate, sulfate, phosphate, or the like. In some instances, an ion may be incorporated into the compositions of the present disclosure by the addition of one or more acids, bases, or salts, such as NiCl2, CoCl2, MgCl2, MnCl2, SrCl2, CaCl2, CaSO4, SrCO3, BaCl2 or the like. Representative salts, ions, solutions and conditions may be found in Remington: The Science and Practice of Pharmacy, 20th. Edition, Gennaro, A. R., Ed. (2000), which is hereby incorporated by reference in its entirety, and especially with respect to Chapter 17 and related disclosure of salts, ions, salt solutions, and ionic solutions.

The present disclosure contemplates contacting the multivalent binding or incorporation composition comprising at least one particle-nucleotide conjugate with one or more polymerases. The contacting can be optionally done in the presence of one or more target nucleic acids. In some examples, said target nucleic acids are single stranded nucleic acids. In some examples, said target nucleic acids are primed single stranded nucleic acids. In some examples, said target nucleic acids are double stranded nucleic acids. In some examples, said contacting comprises contacting the multivalent binding or incorporation composition with one polymerase. In some examples, said contacting comprises the contacting of said composition comprising one or more nucleotides with multiple polymerases. The polymerase can be bound to a single nucleic acid molecule.

The binding between target nucleic acid and multivalent binding composition may be provided in the presence of a polymerase that has been rendered catalytically inactive. In one example, the polymerase may have been rendered catalytically inactive by mutation. In one example, the polymerase may have been rendered catalytically inactive by chemical modification. In some examples, the polymerase may have been rendered catalytically inactive by the absence of a necessary substrate, ion, or cofactor. In some examples, the polymerase enzyme may have been rendered catalytically inactive by the absence of magnesium ions.

The binding between a target nucleic acid and multivalent binding composition described herein may occur in the presence of a polymerase wherein the binding solution, reaction solution, or buffer lacks magnesium or manganese. In another example, the binding between the target nucleic acid and multivalent binding composition occurs in the presence of a polymerase wherein the binding solution, reaction solution, or buffer comprises calcium or strontium.

In some instances, when catalytically inactive polymerases are used to help a nucleic acid interact with a multivalent binding composition, the interaction between said composition and said polymerase stabilizes a ternary complex so as to render the complex detectable by fluorescence or by other methods as disclosed herein or otherwise known in the art. Unbound polymer-nucleotide conjugates may optionally be washed away prior to detection of the ternary binding complex.

Contacting of one or more nucleic acids with the polymer-nucleotide conjugates disclosed herein may occur in a solution containing either one of calcium or magnesium or containing both calcium and magnesium. In another example, the contacting of one or more nucleic acids with the polymer-nucleotide conjugates disclosed herein occurs in a solution lacking either one of calcium or magnesium, or lacking both calcium or magnesium, and in a separate step, without regard to the order of the steps, one of calcium or magnesium, or both calcium and magnesium, may be added to the solution. In some embodiments, the contacting of one or more nucleic acids with the polymer-nucleotide conjugates disclosed herein occurs in a solution lacking strontium, and comprises in a separate step, without regard to the order of the steps, adding to the solution strontium.

Illustrative Embodiment 1

The disclosed methods of determining the sequence of a target nucleic acid comprise: a) contacting a double-stranded or partially double-stranded target nucleic acid molecule comprising the template strand to be sequenced and a primer strand to be elongated with one or more of the disclosed nucleic acid binding compositions; and b) detecting the binding of a nucleic acid binding composition to the nucleic acid molecule, thereby determining the presence of one of said one or more nucleic acid binding compositions on said nucleic acid molecule and the identity of the next nucleotide (i.e., the N+1 or terminal nucleotide) to be incorporated into the complementary strand.

The sequencing method may further comprise incorporating the N+1 or terminal nucleotide into the primer strand, and then repeating the contacting, detecting, and incorporating steps for one or more additional iterations, thereby determining the sequence of the template strand of the nucleic acid molecule. After the step of detecting the ternary binding complex, the primed strand of the primed target nucleic acid is extended for one base before another round of analysis is performed. The primed target nucleic acid can be extended using the conjugated nucleotide that is attached to the polymer in the multivalent binding composition or using an unconjugated or untethered free nucleotide that is provided after the multivalent binding composition has been removed.

The extension of the primed target nucleic acid may be prevented or inhibited due to a blocked nucleotide on the strand or the use of polymerase that is catalytically inactive. When the nucleotide in the polymer-nucleotide conjugate has a blocking group that prevents the extension of the nucleic acid, incorporation of a nucleotide may be achieved by the removal of a blocking group from said nucleotide (such as by detachment of said nucleotide from its polymer, branched polymer, dendrimer, particle, or the like). When the extension of the primed target nucleic acid is inhibited due to the use of polymerase that is catalytically inactive, incorporation of a nucleotide may be achieved by the provision of a cofactor or activator such as a metal ion.

Detection of the ternary complex is achieved prior to, concurrently with, or following the incorporation of the nucleotide residue. In some instances, a primed target nucleic acid may comprise a target nucleic acid with multiple primed locations for the attachment of polymerases and/or nucleic acid binding moieties. In some instances, multiple polymerases may be attached to a single target nucleic acid molecule, such as at multiple sites within a target nucleic acid molecule. In some instances, multiple polymerases may be bound to a multivalent binding composition disclosed herein comprising multiple nucleotides. In some instances, a target nucleic acid molecule may be a product of a strand displacement synthesis, a rolling circle amplification, a concatenation or fusion of multiple copies of a query sequence, or other such methods as are known in the art or as are disclosed elsewhere herein to produce nucleic acid molecules comprising multiple copies of an identical sequence. Therefore, in some instances, multiple polymerases may be attached at multiple identical or substantially identical locations within a target nucleic acid, which comprises multiple identical or substantially identical copies of a query sequence. In some instances, said multiple polymerases may then be involved in interactions with one or more multivalent binding complexes; however, in some examples, the number of binding sites within a target nucleic acid is at least two, and the number of nucleotides or substrate moieties present on a particle-nucleotide conjugate such as a polymer-nucleotide conjugate is also greater than or equal to two.

In some examples, the multivalent binding compositions are provided in combination with other elements such as to provide optimized signals, for example to provide identification of a nucleotide at a particular position in a nucleic acid sequence. In some instances, the compositions disclosed herein are provided in combination with a surface providing low background binding or low levels of protein binding, such as, for example, a hydrophilic or polymer coated surface. Representative surfaces may be found, for example, in U.S. patent application Ser. No. 16/363,842, the contents of which are hereby incorporated by reference in their entirety.

In some instances, the nucleic acid molecule is tethered to the surface of a solid support, e.g., through hybridization of the template strand to an adapter nucleic acid sequence or primer nucleic acid sequence that is tethered to the solid support. In some instances, the solid support comprises a glass, fused-silica, silicon, or polymer substrate. In some instances, the solid support comprises a low non-specific binding coating comprising one or more hydrophilic polymer layers (e.g., PEG layers) where at least one of the hydrophilic polymer layers comprises a branched polymer molecule (e.g., a branched PEG molecule comprising 4, 8, 16, or 32 branches).

The solid support comprises oligonucleotide adapters or primers tethered to at least one hydrophilic polymer layer at a surface density ranging from about 1,000 primer molecules per μm²to about 1,000,000 primer molecules per μm². In some instances, the surface density of oligonucleotide primers may be at least 1,000, at least 10,000, at least 100,000, or at least 1,000,000 molecules per μm². In some instances, the surface density of oligonucleotide primers may be at most 1,000,000, at most 100,000, at most 10,000, or at most 1,000 molecules per μm². Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure, for example, in some instances the surface density of primers may range from about 10,000 molecules per μm²to about 100,000 molecules per μm². Those of skill in the art will recognize that the surface density of primer molecules may have any value within this range, e.g., about 455,000 molecules per μm².

One of ordinary skill would recognize that in a series of iterative sequencing reactions, occasionally one or more sites will fail to incorporate a nucleotide during a given cycle, thus leading one or more sites to be unsynchronized with the bulk of the elongating nucleic acid chains. Under conditions in which sequencing signals are derived from reactions occurring on single copies of a target nucleic acid, these failures to incorporate will yield discrete errors in the output sequence. It is an object of the present disclosure to describe methods for reducing this type of error in sequencing reactions. For example, the use of multivalent substrates that are capable of incorporation into the elongating strand, by providing increased probabilities of rebinding upon premature dissociation of a ternary polymerase complex, can reduce the frequency of “skipped” cycles in which a base is not incorporated. Thus, in some examples, the present disclosure contemplates the use of multivalent substrates as disclosed herein in which the nucleoside moiety is comprised within a nucleotide having a free, or reversibly modified, 5′ phosphate, diphosphate, or triphosphate moiety, and wherein the nucleotide is connected to the particle or polymer as disclosed herein, through a labile or cleavable linkage. In some examples, the present disclosure contemplates a reduction in the intrinsic error rate due to skipped incorporations as a result of the use of the multivalent substrates disclosed herein.

The present disclosure also contemplates sequencing reactions in which sequencing signals from or relating to a given sequence are derived from or originate within definable regions containing multiple copies of the target sequence. Sequencing methods incorporating multiple copies of a target sequence are advantageous in that signals can be amplified due to the presence of multiple simultaneous sequencing reactions within the defined region, each providing its own signal. The presence of multiple signals within a defined area also reduces the impact of any single skipped cycle, due to the fact that the signal from a large number of correct base calls can overwhelm the signal from a smaller number of skipped or incorrect base calls. The present disclosure further contemplates the inclusion of free, unlabeled nucleotides during elongation reactions, or during a separate part of the elongation cycle, in order to provide incorporation at sites that may have been skipped in previous cycles. For example, during or following an incorporation cycle, unlabeled blocked nucleotides may be added such that they may be incorporated at skipped sites. The unlabeled blocked nucleotides may be of the same type or types as the nucleotide attached to the multivalent binding substrate or substrates that are or were present during a particular cycle, or a mixture of 1, 2, 3, 4 or more types of unlabeled blocked nucleotides may be included.

When each sequencing cycle proceeds perfectly, each reaction within the defined region will provide an identical signal. However, as noted elsewhere herein, in a series of iterative sequencing reactions, occasionally one or more sites will fail to incorporate a nucleotide during a given cycle, thus leading one or more sites to be unsynchronized with the bulk of the elongating nucleic acid chains. This issue, referred to as “phasing,” leads to degradation of the sequencing signal as the signal is contaminated with spurious signals from sites having skipped one or more cycles. This, in turn, creates the potential for errors in base identification. The progressive accumulation of skipped cycles through multiple cycles also reduces the effective read length, due to progressive degradation of the sequencing signal with each cycle. It is a further object of this disclosure to provide methods for reducing phasing errors and/or to improve read length in sequencing reactions.

The sequencing method can include contacting a target nucleic acid or multiple target nucleic acids, comprising multiple linked or unlinked copies of a target sequence, with the multivalent binding compositions described herein. Contacting said target nucleic acid, or multiple target nucleic acids comprising multiple linked or unlinked copies of a target sequence, with one or more particle-nucleotide conjugates may provide a substantially increased local concentration of the correct nucleotide being interrogated in a given sequencing cycle, thus suppressing signals from improper incorporations or phased nucleic acid chains (i.e., those elongating nucleic acid chains which have had one or more skipped cycles).

Methods of obtaining nucleic acid sequence information can include contacting a target nucleic acid, or multiple target nucleic acids, wherein said target nucleic acid or multiple target nucleic acids comprise multiple linked or unlinked copies of a target sequence, with one or more particle-nucleotide conjugates. This method results in a reduction in the error rate of sequencing as indicated by reduction in the misidentification of bases, the reporting of nonexistent bases, or the failure to report correct bases. In some embodiments, said reduction in the error rate of sequencing may comprise a reduction of 5%, 10%, 15%, 20% 25%, 50%, 75%, 100%, 150%, 200%, or more compared to the error rate observed using monovalent ligands, including free nucleotides, labeled free nucleotides, protein or peptide bound nucleotides, or labeled protein or peptide bound nucleotides.

The method of obtaining nucleic acid sequence information can include contacting a target nucleic acid, or multiple target nucleic acids, wherein said templet nucleic acid or multiple target nucleic acids comprise multiple linked or unlinked copies of a target sequence, with one or more particle-nucleotide conjugates. This method results in an increase in average read length of 5%, 10%, 15%, 20%, 25%, 50%, 75%, 100%, 150%, 200%, 300%, or more compared to the average read length observed using monovalent ligands, including free nucleotides, labeled free nucleotides, protein or peptide bound nucleotides, or labeled protein or peptide bound nucleotides.

Disclosed herein are methods of obtaining nucleic acid sequence information, said methods comprising contacting a target nucleic acid, or multiple target nucleic acids, wherein said target nucleic acid or multiple target nucleic acids comprise multiple linked or unlinked copies of a target sequence, with one or more particle-nucleotide conjugates. Such methods may result in an increase in average read length of 10 nucleotides (NT), 20 NT, 25 NT, 30 NT, 50 NT, 75 NT, 100 NT, 125 NT, 150 NT, 200 NT, 250 NT, 300 NT, 350 NT, 400 NT, 500 NT, or more compared to the average read length observed using monovalent ligands, including free nucleotides, labeled free nucleotides, protein or peptide bound nucleotides, or labeled protein or peptide bound nucleotides.

In some instances, the disclosed compositions and methods may result in average read lengths for sequencing applications that range from 100 nucleotides to 1,000 nucleotides. In some instances, the average read length may be at least 100 nucleotides, at least 200 nucleotides, at least 225 nucleotides, at least 250 nucleotides, at least 275 nucleotides, at least 300 nucleotides, at least 325 nucleotides, at least 350 nucleotides, at least 375 nucleotides, at least 400 nucleotides, at least 425 nucleotides, at least 450 nucleotides, at least 475 nucleotides, at least 500 nucleotides, at least 525 nucleotides, at least 550 nucleotides, at least 575 nucleotides, at least 600 nucleotides, at least 625 nucleotides, at least 650 nucleotides, at least 675 nucleotides, at least 700 nucleotides, at least 725 nucleotides, at least 750 nucleotides, at least 775 nucleotides, at least 800 nucleotides, at least 825 nucleotides, at least 850 nucleotides, at least 875 nucleotides, at least 900 nucleotides, at least 925 nucleotides, at least 950 nucleotides, at least 975 nucleotides, or at least 1,000 nucleotides. In some instances, the average read length may be a range bounded by any two of the values within this range, e.g., an average read length ranging from 375 nucleotides to 825 nucleotides. Those of skill in the art will recognize that in some instances, the average read length may have any value within the range specified in this paragraph, e.g., 523 nucleotides.

In some instances, the use of multivalent binding compositions described herein for sequencing effectively shortens the sequencing time. The sequencing reaction cycle comprising the contacting, detecting, and incorporating steps is performed in a total time ranging from about 5 minutes to about 60 minutes. In some instances, the sequencing reaction cycle is performed in at least 5 minutes, at least 10 minutes, at least 20 minutes, at least 30 minutes, at least 40 minutes, at least 50 minutes, or at least 60 minutes. In some instances, the sequencing reaction cycle is performed in at most 60 minutes, at most 50 minutes, at most 40 minutes, at most 30 minutes, at most 20 minutes, at most 10 minutes, or at most 5 minutes. Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure, for example, in some instances the sequencing reaction cycle may be performed in a total time ranging from about 10 minutes to about 30 minutes. Those of skill in the art will recognize that the sequencing cycle time may have any value within this range, e.g., about 16 minutes.

In some instances, the disclosed compositions and methods for nucleic acid sequencing will provide an average base-calling accuracy of at least 80%, at least 85%, at least 90%, at least 92%, at least 94%, at least 96%, at least 98%, at least 99%, at least 99.5%, at least 99.8%, or at least 99.9% correct over the course of a sequencing run. In some instances, the disclosed compositions and methods for nucleic acid sequencing will provide an average base-calling accuracy of at least 80%, at least 85%, at least 90%, at least 92%, at least 94%, at least 96%, at least 98%, at least 99%, at least 99.5%, at least 99.8%, or at least 99.9% correct per every 1,000 bases, 10,0000 bases, 25,000 bases, 50,000 bases, 75,000 bases, or 100,000 bases called.

In some instances, the use of multivalent binding compositions disclosed herein for sequencing provides more accurate base readout. In some instances, the disclosed compositions and methods for nucleic acid sequencing will provide an average Q-score for base-calling accuracy over a sequencing run that ranges from about 20 to about 50. In some instances, the average Q-score is at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, or at least 50. Those of skill in the art will recognize that the average Q-score may have any value within this range, e.g., about 32.

In some instances, the disclosed compositions and methods for nucleic acid sequencing will provide a Q-score of greater than 30 for at least 50%, at least 60%, at least 70%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% of the terminal (or N+1) nucleotides identified. In some instances, the disclosed compositions and methods for nucleic acid sequencing will provide a Q-score of greater than 35 for at least 50%, at least 60%, at least 70%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% of the terminal (or N+1) nucleotides identified. In some instances, the disclosed compositions and methods for nucleic acid sequencing will provide a Q-score of greater than 40 for at least 50%, at least 60%, at least 70%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% of the terminal (or N+1) nucleotides identified. In some instances, the disclosed compositions and methods for nucleic acid sequencing will provide a Q-score of greater than 45 for at least 50%, at least 60%, at least 70%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% of the terminal (or N+1) nucleotides identified. In some instances, the disclosed compositions and methods for nucleic acid sequencing will provide a Q-score of greater than 50 for at least 50%, at least 60%, at least 70%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% of the terminal (or N+1) nucleotides identified.

The disclosed low non-specific binding supports and associated nucleic acid hybridization and amplification methods may be used for the analysis of nucleic acid molecules derived from any of a variety of different cell, tissue, or sample types known to those of skill in the art. For example, nucleic acids may be extracted from cells, or tissue samples comprising one or more types of cells, derived from eukaryotes (such as animals, plants, fungi, or protista), archaebacteria, or eubacteria. In some instances, nucleic acids may be extracted from prokaryotic or eukaryotic cells, such as adherent or non-adherent eukaryotic cells. Nucleic acids are variously extracted from, for example, primary or immortalized rodent, porcine, feline, canine, bovine, equine, primate, or human cell lines. Nucleic acids may be extracted from any of a variety of different cell, organ, or tissue types (e.g., white blood cells, red blood cells, platelets, epithelial cells, endothelial cells, neurons, glial cells, astrocytes, fibroblasts, skeletal muscle cells, smooth muscle cells, gametes, or cells from the heart, lungs, brain, liver, kidney, spleen, pancreas, thymus, bladder, stomach, colon, or small intestine). Nucleic acids may be extracted from normal or healthy cells. In another example, or in combination, nucleic acids are extracted from diseased cells, such as cancerous cells, or from pathogenic cells that are infecting a host. Some nucleic acids may be extracted from a distinct subset of cell types, e.g., immune cells (such as T cells, cytotoxic (killer) T cells, helper T cells, alpha beta T cells, gamma delta T cells, T cell progenitors, B cells, B-cell progenitors, lymphoid stem cells, myeloid progenitor cells, lymphocytes, granulocytes, Natural Killer cells, plasma cells, memory cells, neutrophils, eosinophils, basophils, mast cells, monocytes, dendritic cells, and/or macrophages, or any combination thereof), undifferentiated human stem cells, human stem cells that have been induced to differentiate, rare cells (e.g., circulating tumor cells (CTCs), circulating epithelial cells, circulating endothelial cells, circulating endometrial cells, bone marrow cells, progenitor cells, foam cells, mesenchymal cells, or trophoblasts). Nucleic acids may further comprise nucleic acids derived from viral samples and from subviral pathogens, such as viroids and infectious RNAs. Nucleic acids may be derived from clinical or other samples, such as sputum, saliva, ocular fluid, synovial fluid, blood, feces, urine, tissue exudate, sweat, pus, drainage fluid or the like. Nucleic acids may further be derived from plant or fungal samples, such as leaf, cambium, root, meristem, pollen, ovum, seed, spore, inflorescence, mycelium, or the like. Nucleic acids may also be derived from environmental or industrial samples, such as water, air, dust, food, or the like. Other cells, tissues, and samples are contemplated and consistent with the disclosure herein.

Nucleic acid extraction from cells or other biological samples may be performed using any of a number of techniques known to those of skill in the art. For example, a DNA extraction procedure may comprise (i) collection of the cell sample or tissue sample from which DNA is to be extracted, (ii) disruption of cell membranes (i.e., cell lysis) to release DNA and other cytoplasmic components, (iii) treatment of the lysed sample with a concentrated salt solution to precipitate proteins, lipids, and RNA, followed by centrifugation to separate out the precipitated proteins, lipids, and RNA, and (iv) purification of DNA from the supernatant to remove detergents, proteins, salts, or other reagents used during the cell membrane lysis step.

A variety of suitable commercial nucleic acid extraction and purification kits are consistent with the disclosure herein. Examples include, but are not limited to, the QIAamp kits (for isolation of genomic DNA from human samples) and DNAeasy kits (for isolation of genomic DNA from animal or plant samples) from Qiagen (Germantown, Md.), or the Maxwell® and ReliaPrep™ series of kits from Promega (Madison, Wis.).

Illustrative Embodiment 2

Provided herein are methods for attaching a target nucleic acid molecule to a surface, the methods comprising: bringing a mixture comprising said target nucleic acid molecule at a concentration of 1 nanomolar or less in contact with a hydrophilic surface comprising a capture probe coupled thereto under conditions sufficient for said target nucleic acid molecule to be captured by said capture probe in a time period of less than 30 minutes.

In some instances, said mixture comprises a polar aprotic solvent. In some instances, the polar aprotic solvent comprises formamide. In some instances, said capture probe is a nucleic acid molecule. In some instances, said concentration is 0.50 nanomolar or less. In some instances, said concentration is 250 picomolar or less. In some instances, said concentration is 100 picomolar or less. In some instances, said time period is less than or equal to 20 minutes. In some instances, said time period is less than or equal to 15 minutes. In some instances, said time period is less than or equal to 10 minutes. In some instances, said time period is less than or equal to 5 minutes.

In some instances, said hydrophilic surface is maintained at a temperature of about 30 degrees Celsius to about 70 degrees Celsius. In some instances, said hydrophilic surface is maintained at a substantially constant temperature. In some instances, methods further comprise hybridizing the target nucleic acid molecule to the capture probe at a hybridization efficiency that is increased as compared to a comparable hybridization reaction performed for 120 minutes at 90 degrees Celsius for 5 minutes followed by cooling for 120 minutes to reach a final temperature of 37 degrees Celsius in a buffer composition comprising saline-sodium citrate. In some instances, methods further comprise hybridizing the target nucleic acid molecule to the capture probe with a hybridization stringency of at least 80%.

In some instances, the hydrophilic surface exhibits a level of non-specific Cyanine 3 dye absorption of less than about 0.25 molecules per square micrometer. In some instances, the mixture further comprises a pH buffer comprising 2-(N-morpholino)ethanesulfonic acid, acetonitrile, 3-(N-morpholino)propanesulfonic acid, methanol, or a combination thereof. In some instances, the mixture further comprises a crowding agent selected from the group consisting of polyethylene glycol, dextran, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxybutyl methyl cellulose, hydroxypropyl cellulose, methyl cellulose, and hydroxyl methyl cellulose, and any combination thereof. In some instances, the hydrophilic surface comprises one or more hydrophilic polymer layers. In some instances, the one or more hydrophilic polymer layers comprises a molecule selected from the group consisting of polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), poly(vinyl pyridine), poly(vinyl pyrrolidone) (PVP), poly(acrylic acid) (PAA), polyacrylamide, poly(N-isopropylacrylamide) (PNIPAM), poly(methyl methacrylate) (PMA), poly(2-hydroxylethyl methacrylate) (PHEMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), polyglutamic acid (PGA), poly-lysine, poly-glucoside, streptavidin, and dextran. In some instances, the one or more hydrophilic polymer layers comprises at least one dendrimer.

Provided herein are methods for hybridizing a target nucleic acid molecule to a nucleic acid molecule coupled to a hydrophilic polymer surface, the method comprising: (a) providing at least one nucleic acid molecule that is coupled to a hydrophilic polymer surface; and (b) bringing the at least one nucleic acid molecule coupled to the polymer surface into contact with a hybridizing composition comprising a target nucleic acid molecule at a concentration of 1 nanomolar or less under conditions sufficient for said target nucleic acid molecule to hybridize to the at least one nucleic acid molecule coupled to the polymer surface in 30 minutes or less. In some instances, said conditions are maintained at a substantially constant temperature.

In some instances, the hydrophilic polymer surface has a water contact angle of less than 45 degrees. In some instances, the target nucleic acid molecule is present in the hybridizing composition at a concentration of 0.50 nanomolar or less. In some instances, the target nucleic acid molecule is present in the hybridizing composition at a concentration of 250 picomolar or less. In some instances, the target nucleic acid molecule is present in the hybridizing composition at a concentration of 100 picomolar or less. In some instances, bringing the at least one nucleic acid molecule coupled to the polymer surface into contact with the hybridization composition is performed for a time period of less than 30 minutes. In some instances, the time period is less than 20 minutes. In some instances, the time period is less than 15 minutes. In some instances, the time period is less than 10 minutes. In some instances, the time period is less than 5 minutes.

In some instances, methods further comprise hybridizing the target nucleic acid molecule to the at least one nucleic molecule coupled to the polymer surface at a hybridization efficiency that is increased as compared to a comparable hybridization reaction performed for 120 minutes at 90 degrees Celsius for 5 minutes followed by cooling for 120 minutes to reach a final temperature of 37 degrees Celsius in a buffer comprising saline-sodium citrate. In some instances, the temperature is from about 30 degrees Celsius to 70 degrees Celsius. In some instances, the temperature is about 50 degrees Celsius. In some instances, methods further comprise hybridizing the target nucleic acid molecule to the at least one nucleic acid molecule with a hybridization stringency of at least 80%. In some instances, the hydrophilic polymer surface exhibits a level of non-specific Cyanine 3 dye absorption of less than about 0.25 molecules per square micrometer.

In some instances, the hybridization composition further comprises: (a) at least one organic solvent having a dielectric constant of no greater than about 115 as measured at 68 degrees Fahrenheit; and (b) a pH buffer. In some instances, the hybridization composition further comprises: (a) at least one organic solvent that is polar and aprotic; and (b) a pH buffer. In some instances, the at least one organic solvent comprises at least one functional group selected from hydroxy, nitrile, lactone, sulfone, sulfite, and carbonate. In some instances, the at least one organic solvent comprises formamide. In some instances, the at least one organic solvent is miscible with water. In some instances, the at least one organic solvent is at least about 5% by volume based on the total volume of the hybridizing composition. In some instances, the at least one organic solvent is at most about 95% by volume based on the total volume of the hybridizing composition.

In some instances, the pH buffer is at most about 90% by volume of the total volume of the hybridizing composition. In some instances, the pH buffer comprises 2-(N-morpholino)ethanesulfonic acid, acetonitrile, 3-(N-morpholino)propanesulfonic acid, methanol, or a combination thereof. In some instances, the pH buffer further comprises a second organic solvent. In some instances, the pH buffer is present in the hybridizing composition in an amount that is effective to maintain the pH of the hybridizing composition in a range of about 3 to about 10.

In some instances, the hybridizing composition further comprises a molecular crowding agent. In some instances, the molecular crowding agent is selected from the group consisting of polyethylene glycol, dextran, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxybutyl methyl cellulose, hydroxypropyl cellulose, methyl cellulose, and hydroxyl methyl cellulose, and any combination thereof. In some instances, the molecular crowding agent is polyethylene glycol. In some instances, the molecular crowding agent has a molecular weight in the range of about 5,000 to 40,000 Daltons. In some instances, an amount of the molecular crowding agent is at least about 5% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the molecular crowding agent is at most about 50% by volume based on the total volume of the hybridizing composition. In some instances, the at least one nucleic acid molecule coupled to the polymer surface is coupled to the polymer surface through covalent bonding.

In some instances, the hydrophilic polymer surface comprises one or more hydrophilic polymer layers, and the at least one nucleic acid molecule is coupled to the one or more hydrophilic polymer layers. In some instances, the one or more hydrophilic polymer layers comprises a molecule selected from the group consisting of polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), poly(vinyl pyridine), poly(vinyl pyrrolidone) (PVP), poly(acrylic acid) (PAA), polyacrylamide, poly(N-isopropylacrylamide) (PNIPAM), poly(methyl methacrylate) (PMA), poly(2-hydroxylethyl methacrylate) (PHEMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), polyglutamic acid (PGA), poly-lysine, poly-glucoside, streptavidin, and dextran. In some instances, the one or more hydrophilic polymer layers comprises at least one dendrimer.

Provided herein are methods of attaching a target nucleic acid to a surface, comprising: (a) providing at least one surface bound nucleic acid that is attached to a polymer surface having a water contact angle of less than 45 degrees; and (b) bringing the surface bound nucleic acid into contact with a hybridizing composition under isothermal conditions, wherein the hybridizing composition comprises: (i) the target nucleic acid; (ii) at least one organic solvent having a dielectric constant of no greater than about 115 when measured at 68 degrees Fahrenheit; and (iii) a pH buffer.

In some instances, the organic solvent is a polar aprotic solvent. In some instances, the organic solvent is an organic solvent having a dielectric constant of no greater than 40 when measured at 68 degrees Fahrenheit. In some instances, the organic solvent is acetonitrile, alcohol, or formamide. In some instances, the organic solvent comprises at least one functionality selected from hydroxy, nitrile, lactone, sulfone, sulfite, and carbonate. In some instances, the organic solvent is miscible with water. In some instances, the organic solvent is present in an amount effective to denature a double stranded nucleic acid. In some instances, an amount of the organic solvent is at least about 5% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the organic solvent is in the range of about 5% to 95% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the pH buffer is no greater than 90% by volume based on the total volume of the hybridizing composition. In some instances, the hybridizing composition further comprises a molecular crowding agent. In some instances, the molecular crowding agent is selected from the group consisting of polyethylene glycol (PEG), dextran, hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC), hydroxybutyl methyl cellulose, hydroxypropyl cellulose, methylcellulose, and hydroxyl methyl cellulose, and any combination thereof. In some instances, the molecular crowding agent is polyethylene glycol (PEG). In some instances, the molecular crowding agent has a molecular weight in the range of about 5,000 to 40,000 Daltons. In some instances, an amount of the molecular crowding agent is at least about 5% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the molecular crowding agent is less than 50% by volume based on the total volume of the hybridizing composition. In some instances, methods further comprise an additive for controlling a melting temperature of the target nucleic acid. In some instances, an amount of the additive for controlling melting temperature of the target nucleic acid is at least about 2% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the additive for controlling melting temperature of the nucleic acid is in the range of about 2% to 50% by volume based on the total volume of the hybridizing composition. In some instances, the pH buffer comprises at least one buffering agent selected from the group consisting of Tris, HEPES (e.g., 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid), TAPS (e.g., [tris(hydroxymethyl)methylamino]propanesulfonic acid), Tricine, Bicine, Bis-Tris, sodium hydroxide (NaOH), potassium hydroxide (KOH), TES (e.g., 2-[[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]amino]ethanesulfonic acid), EPPS (e.g., 4-(2-Hydroxyethyl)-1-piperazinepropanesulfonic acid, 4-(2-Hydroxyethyl)piperazine-1-propanesulfonic acid, N-(2-Hydroxyethyl)piperazine-N′-(3-propanesulfonic acid)), and MOPS (e.g., 3-(N-morpholino)propanesulfonic acid). In some instances, the pH buffer further comprises a second organic solvent. In some instances, the pH buffer comprises MOPS and methanol. In some instances, an amount of the pH buffer is effective to maintain the pH of the hybridizing composition to be in the range of about 3 to about 10.

In some instances, the surface bound nucleic acid is coupled to the surface through covalent or noncovalent bonding. In some instances, the polymer surface comprises one or more hydrophilic polymer layers, and the surface bound nucleic acid is coupled to the one or more hydrophilic polymer layers. In some instances, no more than 10% of the target nucleic acid is associated with the surface without hybridizing to the polymer surface bound nucleic acid. In some instances, the polymer surface exhibits a level of non-specific cyanine 3 (Cy3) dye absorption of less than about 0.25 molecules per micrometer squared (μm²). In some instances, the one or more hydrophilic polymer layers comprises a molecule selected from the group consisting of polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), poly(vinyl pyridine), poly(vinyl pyrrolidone) (PVP), poly(acrylic acid) (PAA), polyacrylamide, poly(N-isopropylacrylamide) (PNIPAM), poly(methyl methacrylate) (PMA), poly(2-hydroxylethyl methacrylate) (PHEMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), polyglutamic acid (PGA), poly-lysine, poly-glucoside, streptavidin, and dextran. In some instances, the one or more hydrophilic polymer layers comprise at least one dendrimer.

In some instances, bringing the surface bound nucleic acid into contact with the hybridizing composition is performed for a period of no more than 25 minutes. In some instances, bringing the surface bound nucleic acid into contact with the hybridizing composition is performed for a period of no more than 15 minutes. In some instances, bringing the surface bound nucleic acid into contact with the hybridizing composition is performed for a period between 2-25 minutes. In some instances, the isothermal conditions are at a temperature in the range of about 30 to 70 degrees Celsius. In some instances, attaching the target nucleic acid molecule to the surface comprises hybridizing the target nucleic acid to the surface bound nucleic acid with a hybridization stringency of at least 80%. In some instances, attaching the target nucleic acid molecule to the surface comprises hybridizing the target nucleic acid to the surface bound nucleic with an increased hybridization efficiency, as compared to a comparable hybridization reaction wherein the organic buffer is a saline-sodium citrate and hybridizing is performed for 120 minutes at 90 degrees Celsius for 5 minutes followed by cooling for 120 minutes to reach a final temperature of 37 degrees Celsius. In some instances, the target nucleic acid is present in the hybridizing composition at a 1 nanomolar concentration or less. In some instances, the target nucleic acid is present in the hybridizing composition at a 250 picomolar concentration or less. In some instances, the target nucleic acid is present in the hybridizing composition at a 100 picomolar concentration or less. In some instances, the target nucleic acid is present in the hybridizing composition at a 50 picomolar concentration or less. In some instances, methods further comprise hybridizing at least a portion of the surface bound nucleic acid to at least a portion of the target nucleic acid in the hybridizing composition, wherein hybridizing does not consist of cooling.

Provided herein are methods of hybridization, the methods comprising: (a) providing at least one surface bound nucleic acid molecule coupled to a surface; and (b) bringing the at least one surface bound nucleic acid molecule into contact with a hybridizing composition comprising a target nucleic acid molecule, wherein the hybridizing composition comprises: (i) at least one organic solvent; and (ii) a pH buffer. In some instances, the surface exhibits a level of non-specific Cy3 dye absorption corresponding to less than about 0.25 molecules/μm²when measured by a fluorescence imaging system under non-signal saturating conditions. In some instances, no more than 5% of a total number of the target nucleic acid molecule is associated with the surface without hybridizing to the surface bound nucleic acid molecule.

In some instances, the surface bound nucleic acid molecule is coupled to the surface by being tethered to the surface. In some instances, the surface is a hydrophilic polymer surface. In some instances, the surface has a water contact angle of less than 45 degrees. In some instances, the at least one organic solvent has a dielectric constant of no greater than about 115 when measured at 68 degrees Fahrenheit. In some instances, the organic solvent is a polar aprotic solvent. In some instances, the organic solvent is an organic solvent having a dielectric constant of no greater than 40 when measured at 68 degrees Fahrenheit. In some instances, the organic solvent is acetonitrile, alcohol, or formamide. In some instances, the organic solvent comprises at least one functionality selected from hydroxy, nitrile, lactone, sulfone, sulfite, and carbonate. In some instances, the organic solvent is miscible with water. In some instances, the organic solvent is present in an amount effective to denature a double stranded nucleic acid. In some instances, an amount of the organic solvent is at least about 5% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the organic solvent is in the range of about 5% to 95% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the pH buffer is no greater than 90% by volume based on the total volume of the hybridizing composition. In some instances, the hybridizing composition further comprises a molecular crowding agent. In some instances, the molecular crowding agent is selected from the group consisting of polyethylene glycol (PEG), dextran, hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC), hydroxybutyl methyl cellulose, hydroxypropyl cellulose, methylcellulose, and hydroxyl methyl cellulose, and any combination thereof. In some instances, the molecular crowding agent is polyethylene glycol (PEG). In some instances, the molecular crowding agent has a molecular weight in the range of about 5,000 to 40,000 Daltons. In some instances, an amount of the molecular crowding agent is at least about 5% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the molecular crowding agent is less than 50% by volume based on the total volume of the hybridizing composition. In some instances, methods described herein further comprise an additive for controlling a melting temperature of the target nucleic acid. In some instances, an amount of the additive for controlling melting temperature of the target nucleic acid is at least about 2% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the additive for controlling melting temperature of the nucleic acid is in the range of about 2% to 50% by volume based on the total volume of the hybridizing composition. In some instances, the pH buffer comprises at least one buffering agent selected from the group consisting of Tris, HEPES, TAPS, Tricine, Bicine, Bis-Tris, sodium hydroxide (NaOH), potassium hydroxide (KOH), TES, EPPS, and MOPS. In some instances, the pH buffer further comprises a second organic solvent. In some instances, the pH buffer comprises MOPS and methanol. In some instances, an amount of the pH buffer is effective to maintain the pH of the hybridizing composition to be in the range of about 3 to about 10. In some instances, the surface bound nucleic acid is coupled to the surface through covalent or noncovalent bonding. In some instances, the polymer surface comprises one or more hydrophilic polymer layers, and the surface bound nucleic acid is coupled to the one or more hydrophilic polymer layers. In some instances, no more than 10% of the target nucleic acid is associated with the surface without hybridizing to the polymer surface bound nucleic acid. In some instances, the one or more hydrophilic polymer layers comprises a molecule selected from the group consisting of polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), poly(vinyl pyridine), poly(vinyl pyrrolidone) (PVP), poly(acrylic acid) (PAA), polyacrylamide, poly(N-isopropylacrylamide) (PNIPAM), poly(methyl methacrylate) (PMA), poly(2-hydroxylethyl methacrylate) (PHEMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), polyglutamic acid (PGA), poly-lysine, poly-glucoside, streptavidin, and dextran. In some instances, the one or more hydrophilic polymer layers comprises at least one dendrimer.

In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed for a period of no more than 25 minutes. In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed for a period of no more than 15 minutes. In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed for a period of between 2-25 minutes. In some instances, the isothermal conditions are at a temperature in the range of about 30 to 70 degrees Celsius. In some instances, attaching the target nucleic acid molecule to the surface comprises hybridizing the target nucleic acid molecule to the surface bound nucleic acid molecule with a hybridization stringency of at least 80%. In some instances, attaching the target nucleic acid molecule to the surface comprises hybridizing the target nucleic acid molecule to the surface bound nucleic acid molecule with an increased hybridization efficiency, as compared to a comparable hybridization reaction wherein the organic buffer is a saline-sodium citrate and hybridizing is performed for 120 minutes at 90 degrees Celsius for 5 minutes followed by cooling for 120 minutes to reach a final temperature of 37 degrees Celsius. In some instances, the target nucleic acid molecule is present in the hybridizing composition at a 1 nanomolar concentration or less. In some instances, the target nucleic acid is present in the hybridizing composition at a 250 picomolar concentration or less. In some instances, the target nucleic acid molecule is present in the hybridizing composition at a 100 picomolar concentration or less. In some instances, the target nucleic acid molecule is present in the hybridizing composition at a 50 picomolar concentration or less. In some instances, methods further comprise hybridizing at least a portion of the surface bound nucleic acid molecule to at least a portion of the target nucleic acid molecule in the hybridizing composition, wherein hybridizing does not consist of cooling. In some instances, bringing the surface bound nucleic acid into contact with the hybridizing composition comprising the target nucleic acid is performed under conditions of stringency that prevent the target nucleic acid molecule from hybridizing to a non-complementary nucleic acid molecule. In some instances, the stringency is at least or about 70%, 80%, or 90%. In some instances, the stringency is at least 80%. Provided herein are methods of attaching a target nucleic acid molecule to a surface, the method comprising: (a) providing at least one surface bound nucleic acid molecule, wherein the at least one surface bound nucleic acid molecule is coupled to a surface; and (b) bringing a hybridizing composition comprising a target nucleic acid molecule into contact with the at least one surface bound nucleic acid molecule, wherein the hybridizing composition comprises: (i) at least one organic solvent; and (ii) a pH buffer. In some instances, the surface exhibits a level of non-specific Cy3 dye absorption of less than about 0.25 molecules/μm². In some instances, no more than 5% of a total number of the target nucleic acid molecule is associated with the surface without hybridizing to the surface bound nucleic acid molecule. In some instances, bringing the hybridizing composition into contact with the at least one surface bound nucleic acid molecule is performed under isothermal conditions. In some instances, the surface bound nucleic acid molecule is coupled to the surface by being tethered to the surface. In some instances, the surface is a hydrophilic polymer surface. In some instances, the surface has a water contact angle of less than 45 degrees.

In some instances, the at least one organic solvent has a dielectric constant of no greater than about 115 when measured at 68 degrees Fahrenheit. In some instances, the organic solvent is a polar aprotic solvent. In some instances, the organic solvent is an organic solvent having a dielectric constant of no greater than 40 when measured at 70 degrees Fahrenheit. In some instances, the organic solvent is acetonitrile, alcohol, or formamide. In some instances, the organic solvent comprises at least one functionality selected from hydroxy, nitrile, lactone, sulfone, sulfite, and carbonate. In some instances, the organic solvent is miscible with water. In some instances, the organic solvent is present in an amount effective to denature a double stranded nucleic acid. In some instances, an amount of the organic solvent is at least about 5% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the organic solvent is in the range of about 5% to 95% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the pH buffer is no greater than 90% by volume based on the total volume of the hybridizing composition. In some instances, the hybridizing composition further comprises a molecular crowding agent. In some instances, the molecular crowding agent is selected from the group consisting of polyethylene glycol (PEG), dextran, hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC), hydroxybutyl methyl cellulose, hydroxypropyl cellulose, methylcellulose, and hydroxyl methyl cellulose, and any combination thereof. In some instances, the molecular crowding agent is polyethylene glycol (PEG). In some instances, the molecular crowding agent has a molecular weight in the range of about 5,000 to 40,000 Daltons. In some instances, an amount of the molecular crowding agent is at least about 5% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the molecular crowding agent is less than 50% by volume based on the total volume of the hybridizing composition. In some instances, methods further comprise an additive for controlling a melting temperature of the target nucleic acid. In some instances, an amount of the additive for controlling the melting temperature of the target nucleic acid molecule is at least about 2% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the additive for controlling the melting temperature of the nucleic acid is in the range of about 2% to 50% by volume based on the total volume of the hybridizing composition. In some instances, the pH buffer comprises at least one buffering agent selected from the group consisting of Tris, HEPES, TAPS, Tricine, Bicine, Bis-Tris, sodium hydroxide (NaOH), potassium hydroxide (KOH), TES, EPPS, and MOPS. In some instances, the pH buffer further comprises a second organic solvent. In some instances, the pH buffer comprises MOPS and methanol. In some instances, an amount of the pH buffer is effective to maintain the pH of the hybridizing composition to be in the range of about 3 to about 10.

In some instances, the surface bound nucleic acid molecule is coupled to the surface through covalent or noncovalent bonding. In some instances, the polymer surface comprises one or more hydrophilic polymer layers, wherein the surface bound nucleic acid is coupled to the one or more hydrophilic polymer layers. In some instances, no more than 10% of the total number of the target nucleic acid molecule is associated with the surface without hybridizing to the polymer surface bound nucleic acid molecule. In some instances, the one or more hydrophilic polymer layers comprises a molecule selected from the group consisting of polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), poly(vinyl pyridine), poly(vinyl pyrrolidone) (PVP), poly(acrylic acid) (PAA), polyacrylamide, poly(N-isopropylacrylamide) (PNIPAM), poly(methyl methacrylate) (PMA), poly(2-hydroxylethyl methacrylate) (PHEMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), polyglutamic acid (PGA), poly-lysine, poly-glucoside, streptavidin, and dextran. In some instances, the one or more hydrophilic polymer layers comprises at least one dendrimer. In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed for a period of no more than 25 minutes. In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed for a period of no more than 15 minutes. In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed for a period between 2-25 minutes. In some instances, the isothermal conditions are at a temperature in the range of about 30 to 70 degrees Celsius. In some instances, attaching the target nucleic acid molecule to the surface comprises hybridizing the target nucleic acid molecule to the surface bound nucleic molecule with a hybridization stringency of at least 80%. In some instances, attaching the target nucleic acid molecule to the surface comprises hybridizing the target nucleic acid molecule to the surface bound nucleic acid molecule with an increased hybridization efficiency, as compared to a comparable hybridization reaction wherein the organic buffer is a saline-sodium citrate and hybridizing is performed for 120 minutes at 90 degrees Celsius for 5 minutes followed by cooling for 120 minutes to reach a final temperature of 37 degrees Celsius. In some instances, the target nucleic acid molecule is present in the hybridizing composition at a 1 nanomolar concentration or less. In some instances, the target nucleic acid molecule is present in the hybridizing composition at a 250 picomolar concentration or less. In some instances, the target nucleic acid molecule is present in the hybridizing composition at a 100 picomolar concentration or less. In some instances, the target nucleic acid molecule is present in the hybridizing composition at a 50 picomolar concentration or less. In some instances, methods further comprise hybridizing at least a portion of the surface bound nucleic acid molecule to at least a portion of the target nucleic acid molecule in the hybridizing composition, wherein hybridizing does not consist of cooling.

Provided herein are methods of sequencing a target nucleic acid molecule, the methods comprising: (a) bringing a surface bound nucleic acid molecule coupled to a surface into contact with a hybridizing composition comprising a target nucleic acid molecule, wherein the hybridizing composition comprises: (i) at least one organic solvent; and (ii) a pH buffer; (b) amplifying the target nucleic acid molecule to form a plurality of clonally-amplified clusters of the target nucleic acid; and (c) determining the identity of the target nucleic acid molecule, wherein a fluorescence image of the surface comprising the plurality of clonally-amplified clusters of the target nucleic acid molecule exhibits a contrast-to-noise ratio (CNR) of at least 20 when the fluorescence image is captured using a fluorescence imaging system under non-signal saturating conditions. In some instances, methods described herein further comprise hybridizing the target nucleic acid molecule to the at least one surface bound nucleic acid coupled to the surface. In some instances, the CNR is at least 50. In some instances, the organic solvent is a polar aprotic solvent. In some instances, the organic solvent is an organic solvent having a dielectric constant of no greater than 40 as measured at 70 degrees Fahrenheit. In some instances, the organic solvent is acetonitrile, alcohol, or formamide. In some instances, the organic solvent comprises at least one functionality selected from hydroxy, nitrile, lactone, sulfone, sulfite, and carbonate. In some instances, the organic solvent is miscible with water. In some instances, the organic solvent is present in an amount effective to denature a double stranded nucleic acid. In some instances, an amount of the organic solvent is at least about 5% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the organic solvent is in the range of about 5% to 95% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the pH buffer is no greater than 90% by volume based on the total volume of the hybridizing composition. In some instances, the hybridizing composition further comprises a molecular crowding agent. In some instances, the molecular crowding agent is selected from the group consisting of polyethylene glycol (PEG), dextran, hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC), hydroxybutyl methyl cellulose, hydroxypropyl cellulose, methylcellulose, and hydroxyl methyl cellulose, and any combination thereof. In some instances, the molecular crowding agent is polyethylene glycol (PEG). In some instances, the molecular crowding agent has a molecular weight in the range of about 5,000 to 40,000 Daltons. In some instances, an amount of the molecular crowding agent is at least about 5% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the molecular crowding agent is less than 50% by volume based on the total volume of the hybridizing composition. In some instances, methods described herein further comprise an additive for controlling a melting temperature of the target nucleic acid molecule. In some instances, an amount of the additive for controlling melting temperature of the target nucleic acid is at least about 2% by volume based on the total volume of the hybridizing composition. In some instances, an amount of the additive for controlling melting temperature of the nucleic acid molecule is in the range of about 2% to 50% by volume based on the total volume of the hybridizing composition. In some instances, the pH buffer comprises at least one buffering agent selected from the group consisting of Tris, HEPES, TAPS, Tricine, Bicine, Bis-Tris, sodium hydroxide (NaOH), potassium hydroxide (KOH), TES, EPPS, and MOPS. In some instances, the pH buffer further comprises a second organic solvent. In some instances, the pH buffer comprises MOPS and methanol. In some instances, an amount of the pH buffer is effective to maintain the pH of the hybridizing composition to be in the range of about 3 to about 10.

In some instances, the surface bound nucleic acid molecule is coupled to the surface through covalent or noncovalent bonding. In some instances, the polymer surface comprises one or more hydrophilic polymer layers, wherein the surface bound nucleic acid molecule is coupled to the one or more hydrophilic polymer layers. In some instances, the polymer surface exhibits a level of non-specific Cyanine3 (Cy3) dye absorption of less than about 0.25 molecules per micrometer squared (μm²). In some instances, no more than 5% of a total number of the target nucleic acid molecule is associated with the surface without hybridizing to the surface bound nucleic acid molecule. In some instances, no more than 10% of the total number of the target nucleic acid molecule is associated with the surface without hybridizing to the surface bound nucleic acid molecule. In some instances, the one or more hydrophilic polymer layers comprises a molecule selected from the group consisting of polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), poly(vinyl pyridine), poly(vinyl pyrrolidone) (PVP), poly(acrylic acid) (PAA), polyacrylamide, poly(N-isopropylacrylamide) (PNIPAM), poly(methyl methacrylate) (PMA), poly(2-hydroxylethyl methacrylate) (PHEMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), polyglutamic acid (PGA), poly-lysine, poly-glucoside, streptavidin, and dextran. In some instances, the one or more hydrophilic polymer layers comprise at least one dendrimer. In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed under isothermal conditions. In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed at a temperature in the range of about 30 to 70 degrees Celsius. In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed for a period of no more than 25 minutes. In some instances, methods described herein further comprise removing the hybridizing composition from the surface after the period of no more than 25 minutes. In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed for a period between 2-25 minutes. In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed for a period between 2-4 minutes. In some instances, bringing the surface bound nucleic acid molecule into contact with the hybridizing composition is performed for a period of 2 minutes. In some instances, the at least one surface bound nucleic acid molecule is circular. In some instances, methods further comprise hybridizing at least a portion of the surface bound nucleic acid molecule to at least a portion of the target nucleic acid in the hybridizing composition, which hybridizing does not consist of cooling. In some instances, bringing the surface bound nucleic acid into contact with the hybridizing composition comprising the target nucleic acid is performed under conditions of stringency that prevent the target nucleic acid from hybridizing to a non-complementary nucleic acid. In some instances, the stringency is at least or about 70%, 80%, or 90%. In some instances, the stringency is at least 80%.

Provided herein are compositions for hybridizing a target nucleic acid molecule to a surface bound nucleic acid molecule, the compositions comprising: (a) a target nucleic acid molecule; (b) at least one organic solvent; and (c) a pH buffer. In some instances, no more than 10% of a total number of the target nucleic acid molecule is associated with the surface without hybridizing to the surface bound nucleic acid molecule. In some instances, no more than 5% of the total number of the target nucleic acid molecule is bound to the surface without hybridizing to the surface bound nucleic acid molecule.

In some instances, the organic solvent is a polar aprotic solvent. In some instances, the organic solvent is an organic solvent having a dielectric constant of no greater than 40 when measured at 70 degrees Fahrenheit. In some instances, the organic solvent is acetonitrile, alcohol, or formamide. In some instances, the organic solvent comprises at least one functionality selected from hydroxy, nitrile, lactone, sulfone, sulfite, and carbonate. In some instances, the organic solvent is miscible with water. In some instances, the organic solvent is present in an amount effective to denature a double stranded nucleic acid. In some instances, an amount of the organic solvent is at least about 5% by volume based on the total volume of the composition. In some instances, an amount of the organic solvent is in the range of about 5% to 95% by volume based on the total volume of the composition. In some instances, the pH buffer system comprises a pH buffer. In some instances, an amount of the pH buffer is no greater than 90% by volume based on the total volume of the composition. In some instances, the composition further comprises a molecular crowding agent. In some instances, the molecular crowding agent is selected from the group consisting of polyethylene glycol (PEG), dextran, hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC), hydroxybutyl methyl cellulose, hydroxypropyl cellulose, methylcellulose, and hydroxyl methyl cellulose, and any combination thereof. In some instances, the molecular crowding agent is polyethylene glycol (PEG). In some instances, the molecular crowding agent has a molecular weight in the range of about 5,000 to 40,000 Daltons. In some instances, an amount of the molecular crowding agent is at least about 5% by volume based on the total volume of the composition. In some instances, an amount of the molecular crowding agent is less than 50% by volume based on the total volume of the composition. In some instances, the compositions for hybridizing a target nucleic acid molecule to a surface bound nucleic acid molecule further comprise an additive for controlling a melting temperature of the target nucleic acid molecule. In some instances, an amount of the additive for controlling the melting temperature of the target nucleic acid molecule is at least about 2% by volume based on the total volume of the composition. In some instances, an amount of the additive for controlling the melting temperature of the nucleic acid molecule is in the range of about 2% to 50% by volume based on the total volume of the composition. In some instances, the pH buffer comprises at least one buffering agent selected from the group consisting of Tris, HEPES, TAPS, Tricine, Bicine, Bis-Tris, sodium hydroxide (NaOH), potassium hydroxide (KOH), TES, EPPS, and MOPS. In some instances, the pH buffer further comprises a second organic solvent. In some instances, the pH buffer comprises MOPS and methanol. In some instances, an amount of the pH buffer is effective to maintain the pH of the composition to be in the range of about 3 to about 10.

In some instances, the surface bound nucleic acid molecule is coupled to a surface through covalent or noncovalent bonding. In some instances, the surface is a hydrophilic polymer surface. In some instances, the polymer surface comprises one or more hydrophilic polymer layers, wherein the surface bound nucleic acid molecule is coupled to the one or more hydrophilic polymer layers. In some instances, the one or more hydrophilic polymer layers comprises a molecule selected from the group consisting of polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), poly(vinyl pyridine), poly(vinyl pyrrolidone) (PVP), poly(acrylic acid) (PAA), polyacrylamide, poly(N-isopropylacrylamide) (PNIPAM), poly(methyl methacrylate) (PMA), poly(2-hydroxylethyl methacrylate) (PHEMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), polyglutamic acid (PGA), poly-lysine, poly-glucoside, streptavidin, and dextran. In some instances, the one or more hydrophilic polymer layers comprises at least one dendrimer. In some instances, the target nucleic acid molecule is present in the composition at a 1 nanomolar concentration or less. In some instances, the target nucleic acid molecule is present in the composition at a 250 picomolar concentration or less. In some instances, the target nucleic acid molecule is present in the composition at a 100 picomolar concentration or less. In some instances, the target nucleic acid molecule is present in the composition at a 50 picomolar concentration or less.

Provided herein, in some instances, are microfluidic systems, comprising the compositions described herein. In some instances, the microfluidic systems comprise a flow cell device. In some instances, the flow cell device is a microfluidic chip flow cell. In some instances, the flow cell device is a capillary flow cell device. In some instances, at least one surface of the flow cell device comprises one or more hydrophilic polymer layers comprising a molecule selected from the group consisting of polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), poly(vinyl pyridine), poly(vinyl pyrrolidone) (PVP), poly(acrylic acid) (PAA), polyacrylamide, poly(N-isopropylacrylamide) (PNIPAM), poly(methyl methacrylate) (PMA), poly(2-hydroxylethyl methacrylate) (PHEMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), polyglutamic acid (PGA), poly-lysine, poly-glucoside, streptavidin, and dextran. In some instances, the flow cell device comprises a composition described herein formulated as a fluid. In some instances, the flow cell device comprises one or more surface bound nucleic acid molecules coupled to the at least one surface of the flow cell. In some instances, a target nucleic acid molecule in the composition is hybridized to the one or more surface bound nucleic acid molecules coupled to the at least one surface of the flow cell. In some instances, the flow cell device is operatively coupled to an imaging system configured to capture an image of the at least one surface of the flow cell comprising the hybridized target nucleic acid molecule and the one or more surface bound nucleic acid molecules. Methods described herein comprise determining an identity of the target nucleic acid molecule using the microfluidic systems described herein.

Provided herein are kits comprising: (a) a surface; and (b) a composition comprising: (i) at least one organic solvent; and (ii) a pH buffer. In some instances, the surface comprises one or more surface bound nucleic acid molecules coupled to the surface. In some instances, the surface is a hydrophilic polymer surface. In some instances, the surface has a water contact angle of less than 45 degrees. In some instances, the hydrophilic polymer surface comprises one or more hydrophilic polymer layers, and wherein the surface bound nucleic acid is coupled to the one or more hydrophilic polymer layers. In some instances, the one or more hydrophilic polymer layers comprises a molecule selected from the group consisting of polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), poly(vinyl pyridine), poly(vinyl pyrrolidone) (PVP), poly(acrylic acid) (PAA), polyacrylamide, poly(N-isopropylacrylamide) (PNIPAM), poly(methyl methacrylate) (PMA), poly(2-hydroxylethyl methacrylate) (PHEMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), polyglutamic acid (PGA), poly-lysine, poly-glucoside, streptavidin, and dextran. In some instances, the kit further comprises instructions for hybridizing the one or more surface bound nucleic acid molecules to one or more target nucleic acid molecules. In some instances, the kit further comprises instructions for determining the identity of the one or more target nucleic acid molecules.

In some instances, the organic solvent is a polar aprotic solvent. In some instances, the organic solvent is an organic solvent having a dielectric constant of no greater than 40 when measured at 70 degrees Fahrenheit. In some instances, the organic solvent is acetonitrile, alcohol, or formamide. In some instances, the organic solvent comprises at least one functionality selected from hydroxy, nitrile, lactone, sulfone, sulfite, and carbonate. In some instances, the organic solvent is miscible with water. In some instances, the organic solvent is present in an amount effective to denature a double stranded nucleic acid. In some instances, an amount of the organic solvent is at least about 5% by volume based on the total volume of the composition. In some instances, an amount of the organic solvent is in the range of about 5% to 95% by volume based on the total volume of the composition. In some instances, the pH buffer system comprises a pH buffer. In some instances, an amount of the pH buffer is no greater than 90% by volume based on the total volume of the composition. In some instances, the composition further comprises a molecular crowding agent. In some instances, the molecular crowding agent is selected from the group consisting of polyethylene glycol (PEG), dextran, hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC), hydroxybutyl methyl cellulose, hydroxypropyl cellulose, methylcellulose, and hydroxyl methyl cellulose, and any combination thereof. In some instances, the molecular crowding agent is polyethylene glycol (PEG). In some instances, the molecular crowding agent has a molecular weight in the range of about 5,000 to 40,000 Daltons. In some instances, an amount of the molecular crowding agent is at least about 5% by volume based on the total volume of the composition. In some instances, an amount of the molecular crowding agent is less than 50% by volume based on the total volume of the composition. In some instances, the compositions for hybridizing a target nucleic acid molecule to a surface bound nucleic acid molecule further comprise an additive for controlling a melting temperature of the one or more target nucleic acid molecules. In some instances, an amount of the additive for controlling melting temperature of the one or more target nucleic molecules acid is at least about 2% by volume based on the total volume of the composition. In some instances, an amount of the additive for controlling melting temperature of the nucleic acid is in the range of about 2% to 50% by volume based on the total volume of the composition. In some instances, the pH buffer comprises at least one buffering agent selected from the group consisting of Tris, HEPES, TAPS, Tricine, Bicine, Bis-Tris, sodium hydroxide (NaOH), potassium hydroxide (KOH), TES, EPPS, and MOPS. In some instances, the pH buffer further comprises a second organic solvent. In some instances, the pH buffer comprises MOPS and methanol. In some instances, an amount of the pH buffer is effective to maintain the pH of the composition to be in the range of about 3 to about 10.

Provided herein are methods of using the kits described herein. In some instances, the surface bound nucleic acid molecules is coupled to the surface by a covalent or a noncovalent bond. In some instances, the methods comprise: (a) combining the one or more target nucleic acid molecules and the composition of the kit to form a master mix; and (b) bringing the master mix into contact with the one or more surface bound nucleic acid molecules coupled to the surface provided in the kit. In some instances, the methods further comprise (c) hybridizing the one or more target nucleic acid molecules with the one or more surface bound nucleic acid molecules coupled to the surface. In some instances, the surface exhibits a level of non-specific Cy3 dye absorption of less than about 0.25 molecules/μm². In some instances, no more than 10% of a total number of the one or more target nucleic acid molecules is associated with the surface without hybridizing to the surface bound nucleic acid molecule. In some instances, no more than 5% of the total number of the one or more target nucleic acid molecules is associated with the surface without hybridizing to the one or more surface bound nucleic acid molecules. In some instances, hybridizing the one or more target nucleic acid molecules with the one or more surface bound nucleic acid molecules coupled to the surface is performed under isothermal conditions. In some instances, the isothermal conditions are performed at a temperature in a range of 30 to 70 degrees Celsius. In some instances, the methods further comprise (d) amplifying the target nucleic acid hybridized to the surface bound nucleic acid to form a plurality of clonally-amplified clusters of the one or more target nucleic acid molecules coupled to the surface; and (c) determining the identity of the one or more target nucleic acid molecules. In some instances, a fluorescence image of the surface comprising the plurality of clonally-amplified clusters of the one or more target nucleic acid molecules exhibits a contrast-to-noise ratio (CNR) of at least 20 when the fluorescence image is captured using a fluorescence imaging system under non-signal saturating conditions. In some instances, the CNR is at least 50.

In some instances, hybridizing the surface bound nucleic acid and the target nucleic acid is performed for a period of no more than 25 minutes. In some instances, methods of using the kits described herein further comprise removing the composition from the surface after the period of no more than 25 minutes. In some instances, hybridizing the surface bound nucleic acid and the target nucleic acid is performed for a period between 2-25 minutes. In some instances, hybridizing the one or more surface bound nucleic acid molecules and the one or more target nucleic acid molecules is performed for a period of between 2-4 minutes. In some instances, hybridizing the one or more surface bound nucleic acid molecules and the one or more target nucleic acid molecules is performed for a period of 2 minutes. In some instances, the at least one surface bound nucleic acid is circular. In some instances, hybridizing does not consist of cooling. In some instances, bringing the master mix into contact with the one or more surface bound nucleic acid molecules is performed under conditions of stringency that prevent the one or more target nucleic acid molecules from hybridizing to a non-complementary nucleic acid. In some instances, the stringency is at least or about 70%, 80%, or 90%. In some instances, the stringency is at least 80%.

Provided herein are systems comprising: (a) a surface comprising one or more surface bound nucleic acids molecules coupled to the surface; (b) one or more target nucleic acid molecules; and (c) a composition comprising: (i) at least one organic solvent; and (ii) a pH buffer. In some instances, the systems further comprise a fluorescence imaging device. In some instances, the surface is a hydrophilic polymer surface. In some instances, the surface has a water contact angle of less than 45 degrees. In some instances, the hydrophilic polymer surface comprises one or more hydrophilic polymer layers, wherein the one or more surface bound nucleic acid molecules is coupled to the one or more hydrophilic polymer layers. In some instances, the one or more hydrophilic polymer layers comprises a molecule selected from the group consisting of polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), poly(vinyl pyridine), poly(vinyl pyrrolidone) (PVP), poly(acrylic acid) (PAA), polyacrylamide, poly(N-isopropylacrylamide) (PNIPAM), poly(methyl methacrylate) (PMA), poly(2-hydroxylethyl methacrylate) (PHEMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), polyglutamic acid (PGA), poly-lysine, poly-glucoside, streptavidin, and dextran.

In some instances, the organic solvent is an organic solvent having a dielectric constant of no greater than 40 when measured at 70 degrees Fahrenheit. In some instances, the organic solvent is acetonitrile, alcohol, or formamide. In some instances, the organic solvent comprises at least one functionality selected from hydroxy, nitrile, lactone, sulfone, sulfite, and carbonate. In some instances, the organic solvent is miscible with water. In some instances, the organic solvent is present in an amount effective to denature a double stranded nucleic acid. In some instances, an amount of the organic solvent is at least about 5% by volume based on the total volume of the composition. In some instances, an amount of the organic solvent is in the range of about 5% to 95% by volume based on the total volume of the composition. In some instances, the pH buffer system comprises a pH buffer. In some instances, an amount of the pH buffer is no greater than 90% by volume based on the total volume of the composition. In some instances, the composition further comprises a molecular crowding agent. In some instances, the molecular crowding agent is selected from the group consisting of polyethylene glycol (PEG), dextran, hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC), hydroxybutyl methyl cellulose, hydroxypropyl cellulose, methyl cellulose, and hydroxyl methyl cellulose, and any combination thereof. In some instances, the molecular crowding agent is polyethylene glycol (PEG). In some instances, the molecular crowding agent has a molecular weight in the range of about 5,000 to 40,000 Daltons. In some instances, an amount of the molecular crowding agent is at least about 5% by volume based on the total volume of the composition. In some instances, an amount of the molecular crowding agent is less than 50% by volume based on the total volume of the composition. In some instances, the systems described herein further comprise an additive for controlling a melting temperature of the target nucleic acid. In some instances, an amount of the additive for controlling melting temperature of the one or more target nucleic acid molecules is at least about 2% by volume based on the total volume of the composition. In some instances, an amount of the additive for controlling melting temperature of the one or more nucleic acid molecules is in the range of about 2% to 50% by volume based on the total volume of the composition. In some instances, the pH buffer comprises at least one buffering agent selected from the group consisting of Tris, HEPES, TAPS, Tricine, Bicine, Bis-Tris, sodium hydroxide (NaOH), potassium hydroxide (KOH), TES, EPPS, and MOPS. In some instances, the pH buffer further comprises a second organic solvent. In some instances, the pH buffer comprises MOPS and methanol. In some instances, an amount of the pH buffer is effective to maintain the pH of the composition to be in the range of about 3 to about 10.

Provided herein are methods of using the systems described herein. In some instances, the one or more surface bound nucleic acid molecules is coupled to the surface by a covalent or a noncovalent bond. In some instances, the methods comprise: (a) combining the one or more target nucleic acid molecules and the composition of the system to form a master mix; (b) bringing the master mix into contact with the one or more surface bound nucleic acid molecules coupled to the surface provided in the system; (c) hybridizing the one or more target nucleic acid molecules with the one or more surface bound nucleic acid molecules coupled to the surface; (d) amplifying the one or more target nucleic acid molecules hybridized to the one or more surface bound nucleic acid molecules to form a plurality of clonally-amplified clusters of the one or more target nucleic acid molecules coupled to the surface; and (e) determining the identity of the one or more target nucleic acid molecules by capturing an image of the surface with the fluorescence imaging device. In some instances, the surface exhibits a level of non-specific Cy3 dye absorption of less than about 0.25 molecules/μm². In some instances, hybridizing the one or more target nucleic acid molecules with the one or more surface bound nucleic acid molecules coupled to the surface is performed under isothermal conditions. In some instances, the isothermal conditions are performed at a temperature in a range of 30 to 70 degrees Celsius. In some instances, no more than 10% of a total number of the one or more target nucleic acid molecules is associated with the surface without hybridizing to the one or more surface bound nucleic acid molecules. In some instances, no more than 5% of the total number of the one or more target nucleic acid molecules is associated with the surface without hybridizing to the one or more surface bound nucleic acid molecules. In some instances, a fluorescence image of the surface comprising the amplified one or more target nucleic acid molecules exhibits a contrast-to-noise ratio (CNR) of at least 20 when the fluorescence image is captured using the fluorescence imaging device under non-signal saturating conditions. In some instances, the CNR is at least 50.

In some instances, hybridizing the one or more surface bound nucleic acid molecules and the one or more target nucleic acid molecules is performed for a period of no more than 25 minutes. In some instances, the methods disclosed herein further comprise removing the composition from the surface after the period of no more than 25 minutes. In some instances, hybridizing the one or more surface bound nucleic acid molecules and the one or more target nucleic acid molecules is performed for a period between 2-25 minutes. In some instances, hybridizing the one or more surface bound nucleic acid molecules and the one or more target nucleic acid molecules is performed for a period between 2-4 minutes. In some instances, hybridizing the one or more surface bound nucleic acid molecules and the one or more target nucleic acid molecules is performed for a period of 2 minutes. In some instances, the at least one surface bound nucleic acid is circular. In some instances, hybridizing does not consist of cooling. In some instances, bringing the one or more surface bound nucleic acid molecules into contact with the hybridizing composition comprising the one or more target nucleic acid molecules is performed under conditions of stringency that prevent the one or more target nucleic acid molecules from hybridizing to a non-complementary nucleic acid molecule. In some instances, the stringency is at least or about 70%, 80%, or 90%. In some instances, the stringency is at least 80%.

Illustrative Embodiment 3

Disclosed herein are methods of determining an identity of a nucleotide in a target nucleic acid sequence comprising: (a) providing a composition comprising: (i) two or more copies of said target nucleic acid sequence; (ii) two or more primer nucleic acid molecules that are complementary to one or more regions of said target nucleic acid sequence; and (iii) two or more polymerase molecules; (b) contacting said composition with a polymer nucleotide conjugate under conditions sufficient to allow a multivalent binding complex to be formed between said polymer-nucleotide conjugate and said two or more copies of said target nucleic acid sequence in said composition of (a), wherein the polymer-nucleotide conjugate comprises two or more copies of a nucleotide moiety and optionally one or more detectable labels; and (c) detecting said multivalent binding complex, thereby determining the identity of said nucleotide in the target nucleic acid sequence. In some instances, the target nucleic acid sequence is DNA. In some instances, the detection of the multivalent binding complex is performed in the absence of unbound or solution-borne polymer nucleotide conjugates. In some instances, the target nucleic acid sequence has been replicated or amplified or has been produced by replication or amplification. In some instances, the one or more detectable labels are fluorescent labels. In some instances, detecting the multivalent complex comprises a fluorescence measurement. In some instances, the contacting comprises use of one type of polymer-nucleotide conjugate. In some instances, the contacting comprises use of two or more types of polymer-nucleotide conjugates. In some instances, each type of the two or more types of polymer-nucleotide conjugate comprises a different type of nucleotide moiety. In some instances, the contacting comprises use of three types of polymer-nucleotide conjugates, wherein each type of the three types of polymer-nucleotide conjugates comprises a different type of nucleotide moiety. In some instances, the polymer-nucleotide conjugate comprises a blocked nucleotide moiety. In some instances, the blocked nucleotide is a 3′-O-azidomethyl nucleotide, a 3′-O-methyl nucleotide, or a 3′-O-alkyl hydroxylamine nucleotide. In some instances, said contacting occurs in the presence of an ion that stabilizes said multivalent binding complex. In some instances, the contacting is done in the presence of strontium ions, magnesium ions, calcium ions, or any combination thereof. In some instances, the polymerase molecules are catalytically inactive. In some instances, the polymerase molecules have been rendered catalytically inactive by mutation or chemical modification. In some instances, the polymerase molecules have been rendered catalytically inactive by the absence of a necessary ion or cofactor. In some instances, the polymerase molecules are catalytically active. In some instances, the polymer-nucleotide conjugate does not comprise a blocked nucleotide moiety. In some instances, the multivalent binding complex has a persistence time of greater than 2 seconds. In some instances, the method can be carried out at a temperature within a range of 25° C. to 62° C. In some instances, the polymer-nucleotide conjugate further comprises one or more fluorescent labels and the two or more copies of the target nucleic acid sequence are deposited on, attached to, or hybridized to a surface, wherein a fluorescence image of the multivalent binding complex on the surface has a contrast to noise ratio in the detecting step of greater than 20. In some instances, the composition of (a) is deposited on a surface using a buffer that incorporates a polar aprotic solvent. In some instances, the contacting is performed under a condition that stabilizes said multivalent binding complex when said nucleotide moiety is complementary to a next base of said target nucleic acid sequence and destabilizes said multivalent binding complex when said nucleotide moiety is not complementary to said next base of said target nucleic acid sequence. In some instances, said polymer-nucleotide conjugate comprises a polymer having a plurality of branches and said two or more nucleotide moieties are attached to said branches. In some instances, said polymer has a star, comb, cross-linked, bottle brush, or dendrimer configuration. In some instances, said polymer-nucleotide conjugate comprises one or more binding groups selected from the group consisting of an avidin, a biotin, an affinity tag, and combinations thereof. In some instances, the method further comprises a dissociation step that destabilizes said multivalent binding complex formed between the composition of (a) and the polymer-nucleotide conjugate, said dissociation step enabling removal of said polymer-nucleotide conjugate. In some instances, the method further comprises an extension step to incorporate a nucleotide that is complementary to a next base of the target nucleic acid sequence into said two or more primer nucleic acid molecules. In some instances, the extension step occurs concurrently with or after said dissociation step.

Disclosed herein are methods of determining an identity of a nucleotide in a target nucleic acid sequence comprising: (a) providing a composition comprising: (i) two or more copies of said target nucleic acid sequence; (ii) two or more primer nucleic acid molecules that are complementary to one or more regions of said target nucleic acid sequence; and (ii). two or more polymerase molecules; (b) contacting said composition with a polymer nucleotide conjugate under conditions sufficient to allow a multivalent complex to be formed between said polymer-nucleotide conjugate and said two or more copies of said target nucleic acid sequence in said composition of (a), wherein the polymer-nucleotide conjugate comprises two or more copies of a reversibly terminated nucleotide moiety and optionally one or more cleavable detectable labels; and (c) detecting said multivalent complex, thereby determining the identity of said nucleotide in the target nucleic acid sequence. In some instances, the target nucleic acid sequence is DNA. In some instances, the method further comprises contacting the composition of (a) with reversibly terminated nucleotides or polymer-nucleotide conjugates comprising two or more copies of a reversibly terminated nucleotide following the detection of said multivalent binding complex. In some instances, the target nucleic acid sequence has been replicated or amplified or has been produced by replication or amplification. In some instances, the one or more detectable labels are fluorescent labels. In some instances, detecting the multivalent complex comprises a fluorescence measurement. In some instances, the contacting comprises use of one type of polymer-nucleotide conjugate. In some instances, the contacting comprises use of two or more types of polymer-nucleotide conjugates. In some instances, each type of the two or more types of polymer-nucleotide conjugate comprises a different type of nucleotide moiety. In some instances, the contacting comprises use of three types of polymer-nucleotide conjugate, wherein each type of the three types of polymer-nucleotide conjugate comprises a different type of nucleotide moiety. In some instances, the polymer-nucleotide conjugate comprises a blocked nucleotide moiety. In some instances, the blocked nucleotide is a 3′-O-azidomethyl, 3′-O-methyl, or 3′-O-alkyl hydroxylamine. In some instances, said contacting occurs in the presence of an ion that stabilizes said multivalent binding complex. In some instances, the polymerase molecules are catalytically inactive. In some instances, the polymerase molecules have been rendered catalytically inactive by mutation or chemical modification. In some instances, the polymerase molecules are catalytically active. In some instances, the polymer-nucleotide conjugate does not comprise a blocked nucleotide moiety. In some instances, the method can be carried out at a temperature within a range of 25° C. to 80° C. In some instances, the polymer-nucleotide conjugate further comprises one or more fluorescent labels and the two or more copies of the target nucleic acid sequence are deposited on, attached to, or hybridized to a surface, wherein a fluorescence image of the multivalent binding complex on the surface has a contrast to noise ratio in the detecting step of greater than 20.

Also disclosed herein are systems comprising: (a) one or more computer processors individually or collectively programmed to implement a method comprising: (i) contacting a substrate comprising multiple copies of a target nucleic acid sequence tethered to a surface of the substrate with a reagent comprising a polymerase and one or more primer nucleic acid sequences that are complementary to one or more regions of said target nucleic acid sequence to form a primed target nucleic acid sequence; (ii) contacting the substrate surface with a reagent comprising a polymer nucleotide conjugate under conditions sufficient to allow a multivalent binding complex to be formed between said polymer-nucleotide conjugate and two or more copies of said primed target nucleic acid sequence, wherein the polymer-nucleotide conjugate comprises two or more copies of a known nucleotide moiety and a detectable label; (iii) acquiring and processing an image of the substrate surface to detect said multivalent binding complex, thereby determining the identity of a nucleotide in the target nucleic acid sequence. In some instances, the system further comprises a fluidics module configured to deliver a series of reagents to the substrate surface in a specified sequence and for specified time intervals. In some instances, the system further comprises an imaging module configured to acquire images of the substrate surface. In some instances, (ii) and (iii) are repeated two or more times thereby determining the identity of a series of two or more nucleotides in the target nucleic acid sequence. In some instances, the series of steps further comprise a dissociation step that destabilizes said multivalent binding complex, said dissociation step enabling removal of said polymer-nucleotide conjugate. In some instances, the series of steps further comprises an extension step to incorporate a nucleotide that is complementary to a next base of the target nucleic acid sequence into said two or more primer nucleic acid molecules. In some instances, the extension step occurs concurrently with or after said dissociation step. In some instances, the detectable label comprises a fluorophore and the images comprise fluorescence images. In some instances, the fluorescence images of the multivalent binding complex on the substrate surface has a contrast-to-noise ratio of greater than 20 when the fluorophore is cyanine dye 3 (Cy3) and the image is acquired using an inverted fluorescence microscope equipped with a 20× objective, NA=0.75, dichroic mirror optimized for 532 nm light, a bandpass filter optimized for Cyanine dye-3 emission, and a camera, under non-signal saturating conditions while the surface is immersed in 25 mM ACES, pH 7.4 buffer. In some instances, the series of steps is completed in less than 60 minutes. In some instances, the series of steps is completed in less than 30 minutes. In some instances, the series of steps is completed in less than 10 minutes. In some instances, an accuracy of base-calling is characterized by a Q-score of greater than 25 for at least 80% of the nucleotide identities determined. In some instances, an accuracy of base-calling is characterized by a Q-score of greater than 30 for at least 80% of the nucleotide identities determined. In some instances, an accuracy of base-calling is characterized by a Q-score of greater than 40 for at least 80% of the nucleotide identities determined.

Disclosed herein are compositions comprising: a) a polymer core; and b) two or more nucleotide, nucleotide analog, nucleoside, or nucleoside analog moieties attached to the polymer core; wherein the length of the linker is dependent on the nucleotide, nucleotide analog, nucleoside, or nucleoside analog moiety that is attached to the polymer core. Also disclosed herein are compositions comprising: a) a mixture of polymer-nucleotide conjugates, wherein each polymer-nucleotide conjugate comprises: i) a polymer core; and ii) two or more nucleotide, nucleotide analog, nucleoside, or nucleoside analog moieties attached to the polymer core, wherein the length of the linker is dependent on the nucleotide, nucleotide analog, nucleoside, or nucleoside analog moiety that is attached to the polymer core; and wherein the mixture comprises polymer-nucleotide conjugates having at least two different types of attached nucleotides, nucleotide analogs, nucleosides, or nucleoside analog moieties. In some instances, the polymer core comprises a polymer having a plurality of branches and the two or more nucleotide, nucleotide analog, nucleoside, or nucleoside analog moieties are attached to said branches. In some instances, polymer has a star, comb, cross-linked, bottle brush, or dendrimer configuration. In some instances, the polymer-nucleotide conjugate comprises one or more binding groups selected from the group consisting of an avidin, a biotin, an affinity tag, and combinations thereof. In some instances, the polymer core comprises a branched polyethylene glycol (PEG) molecule. In some instances, the polymer-nucleotide conjugate comprises a blocked nucleotide moiety. In some instances, the blocked nucleotide is a 3′-O-azidomethyl nucleotide, a 3′-O-methyl nucleotide, or a 3′-O-alkyl hydroxylamine nucleotide. In some instances, the polymer-nucleotide conjugate further comprises one or more fluorescent labels.

In some instances, the present disclosure provides methods of determining the identity of a nucleotide in a target nucleic acid comprising the steps, without regard to any particular order of operations, 1) providing a composition comprising: a target nucleic acid comprising two or more repeats of an identical sequence; two or more primer nucleic acids complementary to one or more regions of said target nucleic acid; and two or more polymerase molecules; 2) contacting said composition with a multivalent binding or incorporation composition comprising a polymer-nucleotide conjugate under conditions sufficient to allow a binding or incorporated complex to be formed between said polymer-nucleotide conjugate and the composition of step (a), wherein the polymer-nucleotide conjugate comprises two or more copies of a nucleotide and optionally one or more detectable labels; and 3) detecting said binding or incorporated complex, thereby establishing the identity of said nucleotide in the target nucleic acid polymer. In some further instances, the present disclosure provides said method, wherein the target nucleic acid is DNA, and/or wherein the target nucleic acid has been replicated, such as by any commonly practiced method of DNA replication or amplification, such as rolling circle amplification, bridge amplification, helicase dependent amplification, isothermal bridge amplification, rolling circle multiple displacement amplification (RCA/MDA), and/or recombinase based methods of replication or amplification. In some further instances, the present disclosure provides said method, wherein the detectable label is a fluorescent label and/or wherein detecting the complex comprises a fluorescence measurement. In some further instances, the present disclosure provides said method wherein the multivalent binding composition comprises one type of polymer-nucleotide conjugate, wherein the multivalent binding composition comprises two or more types of polymer-nucleotide conjugates, and/or wherein each type of the two or more types of polymer-nucleotide conjugates comprises a different type of nucleotide. In some instances, the present disclosure provides said method wherein the binding complex or incorporated complex further comprises a blocked nucleotide, especially wherein the blocked nucleotide is a 3′-O-azidomethyl nucleotide, a 3′-O-alkyl hydroxylamino nucleotide, or a 3′-O-methyl nucleotide. In some further instances, the present disclosure provides said method wherein the contacting is done in the presence of strontium ions, barium, magnesium ions, and/or calcium ions. In some instances, the present disclosure provides said method wherein the polymerase molecule is catalytically inactive, such as where the polymerase molecule been rendered catalytically inactive by mutation, by chemical modification, or by the absence of a necessary ion or cofactor. In some instances, the present disclosure also provides said method wherein the polymerase molecule is catalytically active, and/or wherein the binding complex does not comprise a blocked nucleotide. In some instances, the present disclosure provides said method wherein the binding complex has a persistence time of greater than 2 seconds and/or wherein the method is or may be carried out at a temperature of at or above 15° C., at or above 20° C., at or above 25° C., at or above 35° C., at or above 37° C., at or above 42° C., at or above 55° C., at or above 60° C., or at or above 72° C., or within a range defined by any of the foregoing. In some instances, the present disclosure provides said method wherein the binding complex is deposited on, attached to, or hybridized to, a surface showing a contrast to noise ratio in the detecting step of greater than 20. In some instances, the present disclosure provides said method wherein the composition is deposited under buffer conditions incorporating a polar aprotic solvent. In some instances, the present disclosure provides said method wherein the contacting is performed under a condition that stabilizes said binding complex when said nucleotide is complementary to a next base of said target nucleic acid and destabilizes said binding complex when said nucleotide is not complementary to said next base of said target nucleic acid. In some instances, the present disclosure provides said method wherein said polymer-nucleotide conjugate comprises a polymer having a plurality of branches and said plurality of copies of said first nucleotide are attached to said branches, especially wherein said first polymer has a star, comb, cross-linked, bottle brush, or dendrimer configuration. In some instances, the present disclosure provides said method wherein said polymer-nucleotide conjugate comprises one or more binding groups selected from the group consisting of avidin, biotin, affinity tag, and combinations thereof. In some instances, the present disclosure provides said method further comprising a dissociation step that destabilizes said binding complex formed between the composition of (a) and the polymer-nucleotide conjugate to remove said polymer-nucleotide conjugate. In some instances, the present disclosure provides said method further comprising an extension step to incorporate into said primer nucleic acid a nucleotide that is complementary to said next base of the target nucleic acid, and optionally wherein the extension step occurs currently as or after said dissociation step.

In some instances, the present disclosure provides a composition comprising a branched polymer having two or more branches and two or more copies of a nucleotide, wherein said nucleotide is attached to a first plurality of said branches or arms, and optionally, wherein one or more interaction moieties are attached to a second plurality of said branches or arms. In some instances, said composition may further comprise one or more labels on the polymer. In some instances, the present disclosure provides said composition wherein the nucleoside has a surface density of at least 4 nucleotides per polymer. In some instances, the present disclosure provides said composition comprising or incorporating a nucleotide or nucleotide analog that is modified so as to prevent its incorporation into an extending nucleic acid chain during a polymerase reaction. In some instances, said composition may comprise or incorporate a nucleotide or nucleotide analog that is reversibly modified so as to prevent its incorporation into an extending nucleic acid chain during a polymerase reaction. In some instances, the present disclosure provides said composition wherein one or more labels comprise a fluorescent label, a FRET donor, and/or a FRET acceptor. In some instances, said composition may comprise 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or more branches or arms, or 2, 4, 8, 16, 32, 64, or more, branches or arms. In some instances, the branches or arms may radiate from a central moiety. In some instances, said composition may comprise one or more interaction moieties, which interaction moieties may comprise avidin or streptavidin; a biotin moiety; an affinity tag; an enzyme, antibody, minibody, receptor, or other protein; a non-protein tag; a metal affinity tag, or any combination thereof. In some instances, the present disclosure provides said composition wherein the polymer comprises polyethylene glycol, polypropylene glycol, polyvinyl acetate, polylactic acid, or polyglycolic acid. In some instances, the present disclosure provides said composition wherein the nucleotide or nucleotide analog is attached to the branch or arm through a linker; and especially wherein the linker comprises PEG, and wherein the PEG linker moiety has an average molecular weight of about 1K Da, about 2K Da, about 3K Da, about 4K Da, about 5K Da, about 10K Da, about 15K Da, about 20K Da, about 50K Da, about 100K Da, about 150K Da, or about 200K Da, or greater than about 200K Da. In some instances, the present disclosure provides said composition wherein the linker comprises PEG, and wherein the PEG linker moiety has an average molecular weight of between about 5K Da and about 20K Da. In some instances, the present disclosure provides said composition wherein at least one nucleotide or nucleotide analog comprises a deoxyribonucleotide, a ribonucleotide, a deoxyribonucleoside, or a ribonucleoside; and/or wherein the nucleotide or nucleotide analog is conjugated to the linker through the 5′ end of the nucleotide or nucleotide analog. In some instances, the present disclosure provides said composition wherein one of the nucleotides or nucleotide analogs comprises deoxyadenosine, deoxyguanosine, thymidine, deoxyuridine, deoxycytidine, adenosine, guanosine, 5-methyl-uridine, and/or cytidine; and wherein the length of the linker is between 1 nm and 1,000 nm. In some instances, the present disclosure provides said composition wherein at least one nucleotide or nucleotide analog is a nucleotide that has been modified to inhibit elongation during a polymerase reaction or a sequencing reaction, such as wherein the at least one nucleotide or nucleotide analog is a nucleotide that lacks a 3′ hydroxyl group; a nucleotide that has been modified to contain a blocking group at the 3′ position; and/or a nucleotide that has been modified with a 3′-O-azido group, a 3′-O-azidomethyl group, a 3′-O-alkyl hydroxylamino group, a 3′-phosphorothioate group, a 3′-O-malonyl group, or a 3′-O-benzyl group. In some instances, the present disclosure provides said composition wherein at least one nucleotide or nucleotide analog is a nucleotide that has not been modified at the 3′ position.

In some instances, the present disclosure provides a method of determining the sequence of a nucleic acid molecule comprising the steps, without regard to any particular order, of 1) providing a nucleic acid molecule comprising a template strand and a complementary strand that is at least partially complementary to the template strand; 2) contacting the nucleic acid molecule with the one or more nucleic acid binding composition according to any of the examples disclosed herein; 3) detecting binding of the nucleic acid binding composition to the nucleic acid molecule, and 4) determining an identity of a terminal nucleotide to be incorporated into said complementary strand of said nucleic acid molecule. In some instances, the present disclosure provides a method of determining the sequence of a nucleic acid molecule comprising the steps, without regard to any particular order, of 1) providing a nucleic acid molecule comprising a template strand and a complementary strand that is at least partially complementary to the template strand; 2) contacting the nucleic acid molecule with the one or more nucleic acid binding compositions according to any of the examples disclosed herein; 3) detecting partial or complete incorporation of the nucleic acid binding composition to the nucleic acid molecule, and 4) determining an identity of a terminal nucleotide to be incorporated into said complementary strand of said nucleic acid molecule from the partial or complete incorporation of the examples described herein. In some instances, the present disclosure provides said method further comprising incorporating said terminal nucleotide into said complementary strand, and repeating said contacting, detecting, and incorporating steps for one or more additional iterations, thereby determining the sequence of said template strand of said nucleic acid molecule. In some instances, the present disclosure provides said method, wherein said nucleic acid molecule is tethered to a solid support; and, in some examples, wherein the solid support comprises a glass or polymer substrate, at least one hydrophilic polymer coating layer, and a plurality of oligonucleotide molecules attached to at least one hydrophilic polymer coating layer. In some instances, the present disclosure provides said method, further comprising examples wherein at least one hydrophilic polymer coating layer comprises PEG; and/or wherein at least one hydrophilic polymer layer comprises a branched hydrophilic polymer having at least 8 branches. In some instances, the present disclosure provides said method, wherein the plurality of oligonucleotide molecules is present at a surface density of at least 500 molecules/mm², at least 1,000 molecules/mm², at least 5,000 molecules/mm², at least 10,000 molecules/mm², at least 20,000 molecules/mm², at least 50,000 molecules/mm², at least 100,000 molecules/mm², or at least 500,000 molecules/mm². In some instances, the present disclosure provides said method, wherein said nucleic acid molecule has been clonally-amplified on a solid support. In some instances, the present disclosure provides said method, wherein the clonal amplification comprises the use of a polymerase chain reaction (PCR), multiple displacement amplification (MDA), transcription-mediated amplification (TMA), nucleic acid sequence-based amplification (NASBA), strand displacement amplification (SDA), real-time SDA, bridge amplification, isothermal bridge amplification, rolling circle amplification (RCA), circle-to-circle amplification, helicase-dependent amplification, recombinase-dependent amplification, single-stranded binding (SSB) protein-dependent amplification, or any combination thereof. In some instances, the present disclosure provides said method, wherein the one or more nucleic acid binding compositions are labeled with fluorophores and the detecting step comprises use of fluorescence imaging; and especially wherein the fluorescence imaging comprises dual wavelength excitation/four wavelength emission fluorescence imaging. In some instances, the present disclosure provides said method, wherein four different nucleic acid binding compositions, each comprising a different nucleotide or nucleotide analog, are used to determine the identity of the terminal nucleotide, wherein the four different nucleic acid binding compositions are labeled with separate respective fluorophores, and wherein the detecting step comprises simultaneous excitation at a wavelength sufficient to excite all four fluorophores and imaging of fluorescence emission at wavelengths sufficient to detect each respective fluorophore. In some instances, the present disclosure provides said method, wherein four different nucleic acid binding compositions, each comprising a different nucleotide or nucleotide analog, are used to determine the identity of the terminal nucleotide, wherein the four different nucleic acid binding compositions are labeled with cyanine dye 3 (Cy3), cyanine dye 3.5 (Cy3.5), cyanine dye 5 (Cy5), and cyanine dye 5.5. (Cy5.5) respectively, and wherein the detecting step comprises simultaneous excitation at any two of 532 nm, 568 nm and 633 nm, and imaging of fluorescence emission at about 570 nm, 592 nm, 670 nm, and 702 nm respectively; and/or wherein the fluorescence imaging comprises dual wavelength excitation/dual wavelength emission fluorescence imaging. In some instances, the present disclosure provides said method, wherein four different nucleic acid binding compositions, each comprising a different nucleotide or nucleotide analog, are used to determine the identity of the terminal nucleotide, wherein one, two, three, or four different nucleic acid binding compositions are respectively labeled, each with a with distinct fluorophore or set of fluorophores, and wherein the detecting step comprises simultaneous excitation at a wavelength sufficient to excite one, two, three, or four fluorophores or sets of fluorophores, and imaging of fluorescence emission at wavelengths sufficient to detect each respective fluorophore. In some instances, the present disclosure provides said method, wherein three different nucleic acid binding or incorporation compositions, each comprising a different nucleotide or nucleotide analog, are used to determine the identity of the terminal nucleotide, wherein one, two, or three different nucleic acid binding or incorporation compositions are respectively labeled, each with a with distinct fluorophore or set of fluorophores, and wherein the detecting step comprises simultaneous excitation at a wavelength sufficient to excite one, two, or three, fluorophores or sets of fluorophores, and imaging of fluorescence emission at wavelengths sufficient to detect each respective fluorophore, and wherein detection of the fourth nucleotide is determined or determinable with reference to the location of “dark” or unlabeled spots or target nucleotides. In some instances, the present disclosure provides said method, wherein the multivalent binding or incorporation composition may comprise three types of polymer-nucleotide conjugates and wherein each type of the three types of polymer-nucleotide conjugates comprises a different type of nucleotide. In some instances, the present disclosure provides said method, wherein the detection of the binding or incorporation complex is performed in the absence of unbound or solution-borne polymer nucleotide conjugates.

In some instances, the present disclosure provides said method, wherein four different nucleic acid binding compositions, or three different nucleic acid binding or incorporation compositions, each comprising a different nucleotide or nucleotide analog, are used to determine the identity of the terminal nucleotide, wherein one of the four or three different nucleic acid binding or incorporation compositions is labeled with a first fluorophore, one is labeled with a second fluorophore, one is labeled with both the first and second fluorophore, and one is not labeled or is absent, and wherein the detecting step comprises simultaneous excitation at a first excitation wavelength and a second excitation wavelength and images are acquired at a first fluorescence emission wavelength and a second fluorescence emission wavelength. In some instances, the present disclosure provides said method, wherein the first fluorophore is Cy3, the second fluorophore is Cy5, the first excitation wavelength is 532 nm or 568 nm, the second excitation wavelength is 633 nm, the first fluorescence emission wavelength is about 570 nm, and the second fluorescence emission wavelength is about 670 nm. In some instances, the present disclosure provides said method, wherein the detection label can comprise one or more portions of a fluorescence resonance energy transfer (FRET) pair, such that multiple classifications can be performed under a single excitation and imaging step. In some instances, the present disclosure provides said method, wherein a sequencing reaction cycle comprising the contacting, detecting, and incorporating/extending steps is performed in less than 30 minutes in less than 20 minutes, or in less than 10 minutes. In some instances, the present disclosure provides said method, wherein an average Q-score for base calling accuracy over a sequencing run is greater than or equal to 30, and/or greater than or equal to 40. In some instances, the present disclosure provides said method, wherein at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the terminal nucleotides identified have a Q-score of greater than 30 and/or greater than or equal to 40. In some instances, the present disclosure provides said method, herein at least 95% of the terminal nucleotides identified have a Q-score of greater than 30.

In some instances, the present disclosure provides a reagent comprising one or more nucleic acid binding compositions as disclosed herein and a buffer. For example, in some instances, the present disclosure provides a reagent, wherein said reagent comprises 1, 2, 3, 4, or more nucleic acid binding or incorporation compositions, wherein each nucleic acid binding or incorporation composition comprises a single type of nucleotide. In some instances, a reagent of the present disclosure comprises 1, 2, 3, 4, or more nucleic acid binding or incorporation compositions, wherein each nucleic acid binding or incorporation composition comprises a single type of nucleotide or nucleotide analog, and wherein said nucleotide or nucleotide analog may respectively correspond to one or more from the group consisting of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), deoxyadenosine triphosphate (dATP), deoxyadenosine diphosphate (dADP), and deoxyadenosine monophosphate (dAMP); one or more from the group consisting of thymidine triphosphate (TTP), thymidine diphosphate (TDP), thymidine monophosphate (TMP), deoxythymidine triphosphate (dTTP), deoxythymidine diphosphate (dTDP), deoxythymidine monophosphate (dTMP), uridine triphosphate (UTP), uridine diphosphate (UDP), uridine monophosphate (UMP), deoxyuridine triphosphate (dUTP), deoxyuridine diphosphate (dUDP), and deoxyuridine monophosphate (dUMP); one or more from the group consisting of cytidine triphosphate (CTP), cytidine diphosphate (CDP), cytidine monophosphate (CMP), deoxycytidine triphosphate (dCTP), deoxycytidine diphosphate (dCDP), and deoxycytidine monophosphate (dCMP); and one or more from the group consisting of guanosine triphosphate (GTP), guanosine diphosphate (GDP), guanosine monophosphate (GMP), deoxyguanosine triphosphate (dGTP), deoxyguanosine diphosphate (dGDP), and deoxyguanosine monophosphate (dGMP). In some other examples or some further examples, the present disclosure provides a reagent comprising or further comprising 1, 2, 3, 4, or more nucleic acid binding or incorporation compositions, wherein each nucleic acid binding or incorporation composition comprises a single type of nucleotide or nucleotide analog, and wherein said nucleotide or nucleotide analog may respectively correspond to one or more from the group consisting of ATP, ADP, AMP, dATP, dADP, dAMP, TTP, TDP, TMP, dTTP, dTDP, dTMP, UTP, UDP, UMP, dUTP, dUDP, dUMP, CTP, CDP, CMP, dCTP, dCDP, dCMP, GTP, GDP, GMP, dGTP, dGDP, and dGMP.

Disclosed herein are kits comprising any of the nucleic acid binding or incorporation compositions disclosed herein and/or any of the reagents disclosed herein, and/or one or more buffers; and instructions for the use thereof.

Disclosed herein are systems for performing any of the methods disclosed herein, comprising any of the nucleic acid binding or incorporation compositions disclosed herein, and/or any of the reagents disclosed herein. In some instances, a system is configured to iteratively perform the sequential contacting of tethered, primed nucleic acid molecules with said nucleic acid binding or incorporation compositions and/or said reagents; and for the detection of binding or incorporation of the disclosed nucleic acid binding or incorporation compositions to the one or more primed nucleic acid molecules.

In some instances, the present disclosure provides a composition comprising a particle (e.g., a nanoparticle or polymer core), said particle comprising a plurality of enzyme or protein binding or incorporation substrates, wherein the enzyme or protein binding or incorporation substrates bind with one or more enzymes or proteins to form one or more binding or incorporation complexes (e.g., a multivalent binding or incorporation complex), and wherein said binding or incorporation may be monitored or identified by observation of the location, presence, or persistence of the one or more binding or incorporation complexes. In some instances, said particle may comprise a polymer, branched polymer, dendrimer, liposome, micelle, nanoparticle, or quantum dot. In some instances, said substrate may comprise a nucleotide, a nucleoside, a nucleotide analog, or a nucleoside analog. In some instances, the enzyme or protein binding or incorporation substrate may comprise an agent that can bind with a polymerase. In some instances, the enzyme or protein may comprise a polymerase. In some instances, said observation of the location, presence, or persistence of one or more binding or incorporation complexes may comprise fluorescence detection. In some instances, the present disclosure provides a composition comprising multiple distinct particles as disclosed herein, wherein each particle comprises a single type of nucleoside or nucleoside analog, and wherein each nucleoside or nucleoside analog is associated with a fluorescent label of a detectably different emission or excitation wavelength. In some instances, the present disclosure provides said composition further comprising one or more labels, e.g., fluorescence labels, on the particle. In some instances, the present disclosure provides said composition wherein the composition comprises at least 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, or more than 20 tethered nucleotides, nucleotide analogs, nucleosides, or nucleoside analogs tethered to the particle. In some instances, the present disclosure provides said composition wherein the nucleoside or nucleoside analog is present at a surface density of between 0.001 and 1,000,000 per μm², between 0.01 and 1,000,000 per μm², between 0.1 and 1,000,000 per μm², between 1 and 1,000,000 per μm², between 10 and 1,000,000 per μm², between 100 and 1,000,000 per μm², between 1,000 and 1,000,000 per μm², between 1,000 and 100,000 per μm², between 10,000 and 100,000 per μm², or between 50,000 and 100,000 per μm², or within a range defined by any two of the foregoing values. In some instances, the present disclosure provides said composition wherein the nucleoside or nucleoside analog is present within a nucleotide or nucleotide analog. In some instances, the present disclosure provides said composition wherein the composition comprises or incorporates a nucleotide or nucleotide analog that is modified so as to prevent its incorporation into an extending nucleic acid chain during a polymerase reaction. In some instances, the present disclosure provides said composition wherein the composition comprises or incorporates a nucleotide or nucleotide analog that is reversibly modified so as to prevent its incorporation into an extending nucleic acid chain during a polymerase reaction. In some instances, the present disclosure provides said composition wherein one or more labels comprise a fluorescent label, a FRET donor, and/or a FRET acceptor. In some instances, the present disclosure provides said composition wherein the substrate (e.g., nucleotide, nucleotide analog, nucleoside, or nucleoside analog) is attached to the particle through a linker. In some instances, the present disclosure provides said composition wherein at least one nucleotide or nucleotide analog is a nucleotide that has been modified to inhibit elongation during a polymerase reaction or a sequencing reaction, such as, for example, a nucleotide that lacks a 3′ hydroxyl group; a nucleotide that has been modified to contain a blocking group at the 3′ position; a nucleotide that has been modified with a 3′-O-azido group, a 3′-O-azidomethyl group, a 3′-O-alkyl hydroxylamino group, a 3′-phosphorothioate group, a 3′-O-malonyl group, or a 3′-O-benzyl group; and/or a nucleotide that has not been modified at the 3′ position.

In some instances, the present disclosure provides a method of determining the sequence of a nucleic acid molecule comprising the steps, without regard to order, of 1) providing a nucleic acid molecule comprising a template strand and a complementary strand that is at least partially complementary to the template strand; 2) contacting the nucleic acid molecule with the one or more nucleic acid binding or incorporation composition according to any of the instances disclosed herein; 3) detecting binding or incorporation of the nucleic acid binding or incorporation composition to the nucleic acid molecule, and 4) determining an identity of a terminal nucleotide to be incorporated into said complementary strand of said nucleic acid molecule. In some instances, said method may further comprise incorporating said terminal nucleotide into said complementary strand, and repeating said contacting, detecting, and incorporating steps for one or more additional iterations, thereby determining the sequence of said template strand of said nucleic acid molecule. In some instances, the present disclosure provides said method wherein said nucleic acid molecule has been clonally-amplified on a solid support. In some instances, the present disclosure provides said method wherein the clonal amplification comprises the use of a polymerase chain reaction (PCR), multiple displacement amplification (MDA), transcription-mediated amplification (TMA), nucleic acid sequence-based amplification (NASBA), strand displacement amplification (SDA), real-time SDA, bridge amplification, isothermal bridge amplification, rolling circle amplification, circle-to-circle amplification, helicase-dependent amplification, recombinase-dependent amplification, single-stranded binding (SSB) protein-dependent amplification, or any combination thereof. In some instances, the present disclosure provides said method wherein a sequencing reaction cycle comprising the contacting, detecting, and incorporating steps is performed in less than 30 minutes, less than 20 minutes, or in less than 10 minutes. In some instances, the present disclosure provides said method wherein an average Q-score for base calling accuracy over a sequencing run is greater than or equal to 30, or greater than or equal to 40. In some instances, the present disclosure provides said method wherein at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the terminal nucleotides identified have a Q-score of greater than 30; or greater than 40. In some instances, the present disclosure provides said method wherein at least 95% of the terminal nucleotides identified have a Q-score of greater than 30.

In some instances, the present disclosure provides a reagent comprising one or more nucleic acid binding or incorporation compositions as disclosed herein, and a buffer. In some instances, the present disclosure provides said reagent, wherein said reagent comprises 1, 2, 3, 4, or more nucleic acid binding or incorporation compositions, wherein each nucleic acid binding or incorporation composition comprises a single type of nucleotide or nucleotide analog, and wherein said nucleotide or nucleotide analog comprises a nucleotide, nucleotide analog, nucleoside, or nucleoside analog. In some instances, the present disclosure provides said method wherein said reagent comprises 1, 2, 3, 4, or more nucleic acid binding or incorporation compositions, wherein each nucleic acid binding or incorporation composition comprises a single type of nucleotide or nucleotide analog, and wherein said nucleotide or nucleotide analog may respectively correspond to one or more from the group consisting of ATP, ADP, AMP, dATP, dADP, and dAMP; one or more from the group consisting of TTP, TDP, TMP, dTTP, dTDP, dTMP, UTP, UDP, UMP, dUTP, dUDP, and dUMP; one or more from the group consisting of CTP, CDP, CMP, dCTP, dCDP, and dCMP; and one or more from the group consisting of GTP, GDP, GMP, dGTP, dGDP, and dGMP. In some instances, the present disclosure provides said method wherein said reagent comprises 1, 2, 3, 4, or more nucleic acid binding or incorporation compositions, wherein each nucleic acid binding or incorporation composition comprises a single type of nucleotide or nucleotide analog, and wherein said nucleotide or nucleotide analog may respectively correspond to one or more from the group consisting of ATP, ADP, AMP, dATP, dADP, dAMP TTP, TDP, TMP, dTTP, dTDP, dTMP, UTP, UDP, UMP, dUTP, dUDP, dUMP, CTP, CDP, CMP, dCTP, dCDP, dCMP, GTP, GDP, GMP, dGTP, dGDP, and dGMP.

In some instances, the present disclosure provides a kit comprising any of the compositions disclosed herein; and/or any of the reagents disclosed herein; one or more buffers; and instructions for the use thereof.

In some instances, the present disclosure provides a system for performing any of the methods disclosed herein; wherein said methods may comprise use of any of the compositions as disclosed herein; and/or any of the reagents as disclosed herein; one or more buffers, and one or more nucleic acid molecules optionally tethered or attached to a solid support, wherein said system is configured to iteratively perform for the sequential contacting of said nucleic acid molecules with said composition and/or said reagent; and for the detection of binding or incorporation of the nucleic acid binding or incorporation compositions to the one or more nucleic acid molecules.

In some instances, the present disclosure provides a composition as disclosed herein for use in increasing the contrast to noise ratio (CNR) of a labeled nucleic acid complex bound to or associated with a surface.

In some instances, the present disclosure provides a composition as disclosed herein for use in establishing or maintaining control over the persistence time of a signal from a labeled nucleic acid complex bound to or associated with a surface.

In some instances, the present disclosure provides a composition as disclosed herein for use in establishing or maintaining control over the persistence time of a fluorescence, luminescence, electrical, electrochemical, colorimetric, radioactive, magnetic, or electromagnetic signal from a labeled nucleic acid complex bound to or associated with a surface.

In some instances, the present disclosure provides a composition as disclosed herein for use in increasing the specificity, accuracy, or read length of a nucleic acid sequencing and/or genotyping application.

In some instances, the present disclosure provides a composition as disclosed herein for use in increasing the specificity, accuracy, or read length in a sequencing by binding or incorporation, sequencing by synthesis, single molecule sequencing, or ensemble sequencing method.

In some instances, the present disclosure provides a reagent as disclosed herein for use in increasing the contrast to noise ratio (CNR) of a labeled nucleic acid complex bound to or associated with a surface.

In some instances, the present disclosure provides a reagent as disclosed herein for use in establishing or maintaining control over the persistence time of a signal from a labeled nucleic acid complex bound to or associated with a surface.

In some instances, the present disclosure provides a reagent as disclosed herein for use in establishing or maintaining control over the persistence time of a fluorescence, luminescence, electrical, electrochemical, colorimetric, radioactive, magnetic, or electromagnetic signal from a labeled nucleic acid complex bound to or associated with a surface.

In some instances, the present disclosure provides a reagent as disclosed herein for use in increasing the specificity, accuracy, or read length of a nucleic acid sequencing and/or genotyping application.

In some instances, the present disclosure provides a reagent as disclosed herein for use in increasing the specificity, accuracy, or read length in a sequencing by binding or incorporation, sequencing by synthesis, single molecule sequencing, or ensemble sequencing method.

Definitions

Unless otherwise defined, all of the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art in the field to which this disclosure belongs.

As used in this specification and the appended enumerated embodiments, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Any reference to “or” herein is intended to encompass “and/or” unless otherwise stated.

As used herein, the term “about” a number refers to that number plus or minus 10% of that number. The term “about” when used in the context of a range refers to that range minus 10% of its lowest value and plus 10% of its greatest value.

As used herein, the terms “DNA hybridization” and “nucleic acid hybridization” are used interchangeably and are intended to cover any type of nucleic acid hybridization, e.g., DNA hybridization or RNA hybridization, unless otherwise specified.

As used herein, the term “isothermal” refers to a condition in which the temperature remains substantially constant. A temperature that is “substantially constant” may deviate (e.g., increase or decrease) over a period of time by no more than 0.25 degrees, 0.50 degrees, 0.75 degrees, or 1.0 degrees.

The terms “anneal” or “hybridize,” are used herein interchangeably to refer to the ability of two nucleic acid molecules to combine together. In some cases, the “combining” refers to Watson-Crick base pairing between the bases in each of the two nucleic acid molecules.

As used herein, “hybridization specificity” refers to a measure of the ability of nucleic acid molecules (e.g., adapter sequences, primer sequences, or oligonucleotide sequences) to correctly hybridize to a region of a target nucleic acid molecule with a nucleic acid sequence that is completely complementary to the nucleic acid molecule.

As used herein, “hybridization sensitivity” refers to a concentration range of sample (or target) nucleic molecules in which hybridization occurs with high specificity. In some cases, as little as 50 picomolar concentration of sample nucleic acid molecules in which hybridization with high specify is achieved with the methods, compositions, systems and kits described herein. In some instances, the range is between about 1 nanomolar to about 50 picomolar concentrations of sample nucleic acid molecules.

As used herein, “hybridization efficiency” refers to a measure of the percentage of total available nucleic acid molecules (e.g., adapter sequences, primer sequences, or oligonucleotide sequences) that are hybridized to the region of the target nucleic acid molecule with the nucleic acid sequence that is completely complementary to the nucleic acid molecule.

As used herein, the term “hybridization stringency” refer to a percentage of nucleotide bases within at least a portion of a nucleic acid sequence undergoing a hybridization (e.g., a hybridization region) reaction that is complementary through standard Watson-Crick base pairing. In a non-limiting example, a hybridization stringency of 80% means that a stable duplex can be formed in which 80% of the hybridization region undergoes Watson-Crick base pairing. A higher hybridization stringency means a higher degree of Watson-Crick base pairing is required in a given hybridization reaction in order to form a stable duplex.

As used herein, the terms, “isolate” and “purify,” are used interchangeably herein unless specified otherwise.

As used herein, “nucleic acid” (also referred to as a “polynucleotide”, “oligonucleotide”, ribonucleic acid (RNA), or deoxyribonucleic acid (DNA)) is a linear polymer of two or more nucleotides joined by covalent internucleosidic linkages, or variants or functional fragments thereof. In naturally occurring examples of nucleic acids, the internucleoside linkage is a phosphodiester bond. However, other examples optionally comprise other internucleoside linkages, such as phosphorothiolate linkages and may or may not comprise a phosphate group. Nucleic acids include double- and single-stranded DNA, as well as double- and single-stranded RNA, DNA/RNA hybrids, peptide-nucleic acids (PNAs), hybrids between PNAs and DNA or RNA, and may also include other types of nucleic acid modifications.

As used herein, a “nucleotide” refers to a nucleotide, nucleoside, or analog thereof. The nucleotide refers to both naturally occurring and chemically modified nucleotides and can include but are not limited to a nucleoside, a ribonucleotide, a deoxyribonucleotide, a protein-nucleic acid residue, or derivatives. Examples of the nucleotide includes an adenine, a thymine, a uracil, a cytosine, a guanine, or residue thereof; a deoxyadenine, a deoxythymine, a deoxyuracil, a deoxycytosine, a deoxyguanine, or residue thereof; a adenine PNA, a thymine PNA, a uracil PNA, a cytosine PNA, a guanine PNA, or residue or equivalents thereof, an N- or C-glycoside of a purine or pyrimidine base (e.g., a deoxyribonucleoside containing 2-deoxy-D-ribose or ribonucleoside containing D-ribose).

“Complementary,” as used herein, refers to the topological compatibility or matching together of interacting surfaces of a ligand molecule and its receptor. Thus, the receptor and its ligand can be described as complementary, and furthermore, the contact surface characteristics are complementary to each other.

“Branched polymer”, as used herein, refers to a polymer having a plurality of functional groups that help conjugate a biologically active molecule such as a nucleotide, and the functional group can be either on the side chain of the polymer or directly attached to a central core or central backbone of the polymer. The branched polymer can have a linear backbone with one or more functional groups coming off the backbone for conjugation. The branched polymer can also be a polymer having one or more sidechains, wherein the one or more side chains has a site suitable for conjugation. Examples of the functional group include but are limited to hydroxyl, ester, amine, carbonate, acetal, aldehyde, aldehyde hydrate, alkenyl, acrylate, methacrylate, acrylamide, active sulfone, hydrazide, thiol, alkanoic acid, acid halide, isocyanate, isothiocyanate, maleimide, vinylsulfone, dithiopyridine, vinylpyridine, iodoacetamide, epoxide, glyoxal, dione, mesylate, tosylate, and tresylate.

“Polymerase,” as used herein, refers to an enzyme that contains a nucleotide binding moiety and helps formation of a binding complex between a target nucleic acid and a complementary nucleotide. The polymerase can have one or more activities including, but not limited to, base analog detection activities, DNA polymerization activity, reverse transcriptase activity, DNA binding or incorporation, strand displacement activity, and nucleotide binding or incorporation and recognition. The polymerase can include catalytically inactive polymerase, catalytically active polymerase, reverse transcriptase, and other enzymes containing a nucleotide binding or incorporation moiety.

“Persistence time,” as used herein, refers to the length of time that a binding complex, which is formed between the target nucleic acid, a polymerase, and a conjugated or unconjugated nucleotide, remains stable without any binding component dissociating from the binding complex. The persistence time is indicative of the stability of the binding complex and strength of the binding interactions. Persistence time can be measured by observing the onset and/or duration of a binding complex, such as by observing a signal from a labeled component of the binding complex. For example, a labeled nucleotide or a labeled reagent comprising one or more nucleotides may be present in a binding complex, thus allowing the signal from the label to be detected during the persistence time of the binding complex. One non-limiting example of label is a fluorescent label.

Abbreviations

Dimethyl sulfoxide (DMSO),

Dimethylformamide (DMF),

3-(N-morpholino)propanesulfonic acid (MOPS),

Acetonitrile (ACN)

2-(N-morpholino)ethanesulfonic acid (MES)

saline-sodium citrate (SSC)

Formamide (Form.)

Tris(hydroxymethyl)aminomethane (Tris)

Examples

These examples are provided for illustrative purposes only and not to limit the scope of the examples and enumerated embodiments provided herein.

Example 1—DNA Hybridization on Low Non-Specific Binding Surface

FIGS. 1A-B provide examples of the optimized hybridization achieved on low binding surface using the disclosed hybridization method (FIG. 1A) with reduced concentrations of hybridization reporter probe and shortened hybridization times, as compared to the results achieved using a traditional hybridization protocol on the same low binding surface (FIG. 1B).

FIG. 1A shows hybridization reactions on the low binding surface according to the embodiments described herein. The rows provide two test hybridization conditions, hybridization condition 1 (“Hyb 1”) and hybridization condition 2 (“Hyb 2”). Hyb 1 refers to the hybridization buffer composition C10 from Table 1. Hyb 2 refers to the hybridization buffer composition D18 from Table 1. A hybridization reporter probe (complementary oligonucleotide sequences labeled with a Cy™3 fluorophore at the 5′ end) at concentrations reported in FIG. 1A (10 nM, 1 nM, 250 pM, 100 pM, and 50 pM) were hybridized in the buffer compositions at 60 degrees Celsius for 2 minutes.

FIG. 1B shows hybridization reactions on the low binding surface according to a standard hybridization protocol with standard hybridization conditions (“Standard Hyb Conditions”). A standard hybridization buffer of 2×-5× saline-sodium citrate (SSC) was used with same hybridization reporter probe above at the same concentrations above, as shown in FIG. 1A. The standard hybridization reaction was performed at 90 degrees Celsius with a slow cool process (2 hours) to reach 37 degrees Celsius.

For each hybridization reaction provided in FIG. 1A and FIG. 1B, the top row for each hybridization reaction is test (“T”), which is the complementary oligos (e.g., CY3™-5′-ACCCTGAAAGTACGTGCATTACATG-3′), and the bottom row for each hybridization reach is a control (“C”), which is a noncomplementary oligos (e.g., CY3™-5′-ATGTCTATTACGTCACACTATTATG-3′).

The surfaces used for all testing conditions were ultra-low non-specific binding surfaces having a level of non-specific Cy3 dye absorption corresponding to less than or equal to about 0.25 molecules/μm². In this example, the low non-specific binding surfaces used were a glass substrates that were functionalized with Silane-PEG-5K-COOH (Nanocs Inc.).

Following completion of the hybridization reactions, wells were washed with 50 mM Tris pH 8.0; 50 mM NaCl.

Images were obtained using an inverted microscope (Olympus IX83) equipped with 100×TIRF objective, NA=1.4 (Olympus), dichroic mirror optimized for 532 nm light (Semrock, Di03-R532-t1-25×36), a bandpass filter optimized for Cy3 emission, (Semrock, FF01-562/40-25), and a camera (sCMOS, Andor Zyla) under non-signal saturating conditions for 1 s, (Laser Quantum, Gem 532, <1 W/cm²at the sample) while the sample was immersed in a buffer (25 mM ACES, pH 7.4 buffer). Images were collected as described above, and the results are shown in FIG. 1A (optimized) and FIG. 1B (standard).

A significant signal was observed from the reaction with 250 picomolar (pM) in both Hyb 1 and Hyb 2 hybridization reactions (FIG. 1A), as compared with the negative control. In contrast, no signal was observed from the reaction with 250 pM in the Standard Hyb conditions, as compared with the negative control. The same result was observed for lower input concentrations (e.g., 100 pM, 50 pM) of the hybridization reporter probe. FIG. 1A shows more than 200-fold decrease in input DNA (labeled oligo) required for specific DNA capture on low non-specific binding surfaces tested, a 50× decrease in hybridization times, and a reduction in the hybridization temperatures by half, as compared with standard hybridization methods and reagents on the same low non-specific binding substrates (FIG. 1B). The buffer compositions and methods described herein boast improved hybridization specificity, decreased workflow times and increased hybridization sensitivity.

Example 2

Buffer compositions according to various embodiments described herein were optimized to facilitate hybridization of monotemplate oligonucleotide fragments to the low non-specific binding surface described herein.

Preparing the low non-specific binding surfaces. Glass substrates (175 um 22×60 mm², Corning Glass) were cleaned with KOH and ethanol. Low binding glass surfaces were prepared by incubating Silane-PEG5K-NHS (Nanocs) in ethanol at 65 degrees for 30 minutes. Oligonucleotides with 5′ modified NH₂were grafted to these surfaces in a mixture of 1 micromolar (uM), 5.1 μM, and 46 uM oligonucleotides in methanol/phosphate buffer for 20 minutes, to form immobilized oligonucleotides coupled to the glass substrates.

Circularizing monotemplate oligonucleotide fragments into library. Monotemplate oligonucleotide fragments (approximately 100 base pairs in length) were circularized using splint ligation protocol that contained complementary fragments to surface grafted primers.

Hybridizing the circularized library to immobilized oligonucleotides. Following circularization of the library, circular library fragments were added at a concentration of 100 picomolar (pM) in various test hybridization test mixtures indicated by rows B-F. Individual buffer/library hybridization mixtures were added to 384 well plate with the functionalized surface affixed at 50 degrees Celsius for 4 minutes.

Visualizing hybridization using test buffer compositions. Intercalating DNA stain was added to the buffer/library hybridization mixtures following the hybridization reaction to visualize the hybridization of the circularized libraries. The 384 well plate was imaged using a fluorescence microscope and 488 nanometer (nm) excitation with a 60× water immersion objective (1.2 NA, Olympus) (See FIG. 3). A number of buffer compositions were tested for the hybridization of target nucleic acid (e.g., circularized library) with surface bound nucleic acid (e.g., immobilized oligonucleotides). Table 1 provides the buffer compositions and immobilized oligonucleotide concentrations for each reaction seen in FIG. 3, with columns 10-21 in Table 1 corresponding with columns 10-21 of FIG. 3, and rows B-F corresponding to row B-F of FIG. 3. F10 and F11 are negative controls using standard hybridization conditions, where no background signal was detected signifying both the validity of the negative control and the low non-specific binding nature of surfaces tested.

TABLE 1 Buffer compositions tested for hybridizing target nucleic acid with surface bound nucleic acid Graft concentration 1 uM 5.1 uM 46 uM 9 10 11 12 13 14 15 16 17 18 19 20 21 B Cracked 75% 75% 2x 25% Std 30% Std 50% Std Std Std Std ACN + ACN + SSC ACN + buf. + PEG ACN + MES Phos 2xSSC + 5% PEG + 50% 10% 30% Std PEG Form. buf. C 1 uM 50% 50% 4x 25% Std 20% Std + Std + Tris + Tris + Std Std 31- ACN + ACN + SSC ACN + buf. + PEG + 2 2 1xSSC 1xSSC buff + buff + NH2- Mes Tris MES + 10% 2x 5% 5% Cy3 20% PEG + SSC PEG + PEG + PEG + 5 % 30% 30% 10% Form. Form. Form. Form. D 1 uM 25% 25% 10x 50% Std 10% Std + Std + 25% 25% Std Std 31- ACN + ACN + SSC EtOH + buf. + PEG + 4 4 ACN + ACN + buff + buff + NH2- MES + Tris + 2x 10% 2x MES + MES + 10% 10% Cy3 2xSSC 2xSSC SSC PEG + SSC + 20% 20% PEG + PEG + 10% 5% PEG + PEG + 5% 5% Form. Form. 10% 10% Form. Form. Form. Form. E 1 uM MES + Tris + 20x 50% Std 5% Std + Std + Std Std 10% 10% 31- 1xSSC 1xSSC SSC EtOH + buf. + Form. + 6 6 buf. + buf. + PEG + PEG + NH2- 2x 20% 2xSSC 20% 20% 2x 2x Cy3 SSC + PEG + PEG + PEG + SSC + SSC + 10% 10% 10% 10% 5% 5% PEG Form. Form. Form. Form. Form. F 10 nM 10 nM 10nM 10x Std Std 10% Std + Std + Std Std 10% 10% 31- 31- 31- SSC + buf. + Form. + 8 8 buf. + buf. + Form. + Form. + NH2- NH2- NH2- 10% 10% 2xSSC 10% 10% 2xSSC 2xSSC Cy3 Cy3 Cy3 Form. Form. Form. Form.

“Graft” concentration refers to the concentration of surface bound oligos. Spot counts for each of the hybridization conditions were tabulated, whereby higher counts indicated more effective hybridization buffer formulations as shown in FIG. 4. Table 1 provides the buffer compositions and immobilized oligonucleotide concentrations for each reaction seen in FIG. 4, with columns 10-21 in Table 1 corresponding with columns 10-21 of FIG. 4, and rows B-F corresponding to row B-F of FIG. 4.

Amplifying the hybridized target nucleic acid with surface bound nucleic acid. Following hybridization, the target nucleic acids were amplified to quantify hybridization effectiveness. Rolling circle amplification (RCA) was performed using amplification mixes with Bst according to manufacturer's instructions (New England Biolabs®). The amplified colonies of target nucleic acids were further amplified using a RCA/PCR amplification strategy, whereby PCR cycles were performed on the RCA multimer nanoball to improve the detection sensitivity of the assay and more stringently quantify hybridized library.

The resulting surface amplified products were again stained with intercalating DNA stains and imaged to verify hybridization specificity and effectiveness (See FIG. 5). Table 1 provides the buffer compositions and immobilized oligonucleotide concentrations for each reaction seen in FIG. 5, with columns 10-21 in Table 1 corresponding with columns 10-21 of FIG. 5, and rows B-F corresponding to row B-F of FIG. 5.

Analysis of Hybridization Buffers and conditions. Hybridization conditions were evaluated based on the correlation of maximum spot counts from FIG. 3, FIG. 4, and FIG. 5. Hybridization buffer C10, D18, and E21 showed the highest spot count, as compared to the negative controls provided in F10 and F11 in which water, instead of hybridization buffer, was used. in FIG. 4. This result was validated in FIG. 5 after amplification.

Example 3

In this example, the non-specific binding of cyanine 3 dye (Cy3)-labeled molecules was measured on the low non-specific binding surfaces disclosed herein. In independent non-specific binding assays, 1 uM labeled Cy3 dCTP (GE Amersham), 1 uM Cy5 dGTP dye (Jena Biosciences), 10 uM Aminoallyl-dUTP—ATTO-647N (Jena Biosciences), 10 uM Aminoallyl-dUTP—ATTO-Rho11 (Jena Biosciences), 10 μM Aminoallyl-dUTP—ATTO-Rho11 (Jena Biosciences), 10 μM cCTP—Cy3.5 (GE Amersham), and 10 μM 7-Propargylamino-7-deaza-dGTP—Cy3 (Jena Biosciences) were incubated individually on the low non-specific binding surfaces described in Example 2 (Glass substrates treated with Silane-PEG5K, Nanocs) at 37° C. for 15 minutes in a 384 well plate format. Each well was rinsed 2-3× with 50 μl deionized RNase/DNase Free water and 2-3× with 25 mM ACES buffer pH 7.4. The 384 well plates were imaged at single molecule resolution on an Olympus IX83 microscope (Olympus Corp., Center Valley, Pa.) with TIRF objective (100×, 1.4 NA, Olympus), a sCMOS camera (Zyla 4.2, Andor), an illumination source with excitation wavelengths of 532 nm or 635 nm. Dichroic mirrors were purchased from Semrock (IDEX Health & Science, LLC, Rochester, N.Y.), e.g., 405, 488, 532, or 633 nm dichroic reflectors/beamsplitters, and band pass filters were chosen as 532 LP or 645 LP concordant with the appropriate excitation wavelength. 5.

The imaging set-up enabled the visualization of single dye molecules bound to the substrates. Individual fluorescent spots were counted and the total spot numbers were divided by the respective area of the ROI. For example, with a 100× objective and Andor sCMOS camera, which has a pixel size of 6.5 microns, it is possible to calculate the area of a region of interest (ROI).

A low non-specific binding of the dye molecules above of less than or equal to about 0.50 molecules per μm²was observed. Some non-specific binding of the dye molecules of less than or equal to 0.25 molecules per μm²was observed.

Example 4

A nucleic acid sequencing reaction is performed using the workflow provided in FIG. 2 using the disclosed hybridization compositions and methods from Example 1 and Example 2 on the surfaces used in Examples 1-3. In this non-limiting example, the processing times that are achieved are also provided in FIG. 2.

Example 5: Preparation of Multivalent Binding Composition

One type of multi-armed substrate, as shown in FIG. 16A was made by reacting propargylamine dNTPs with Biotin-PEG-NHS. This aqueous reaction was driven to completion and purified; resulting in a pure Biotin-PEG-dNTP species. In separate reactions, several different PEG lengths were used, corresponding to average molecular weights varying from 1K Da to 20K Da. The Biotin-PEG-dNTP species were mixed with either freshly prepared or commercially-sourced dye-labeled streptavidin (SA) using a Dye:SA ratio of 3-5:1. Mixing of Biotin-PEG-dNTP with dye-labeled streptavidin was done in the presence of excess biotin-PEG-dNTP to ensure saturation of the biotin binding sites on each streptavidin tetramer. Complete complexes were purified away from excess biotin-PEG-dNTP by size exclusion chromatography. Each nucleotide type was conjugated and purified separately, then mixed together to create a four-base mix for sequencing.

Another type of multi-armed substrate as shown in FIG. 16A was made in a single pot by reacting multi-arm PEG NHS with excess Dye-NH2 and propargylamine dNTPs. Various multi-arm PEG NHS variants were used ranging from 4-16 arms and ranging in molecular weight from 5K Da to 40K Da. After reacting, excess small molecule dye and dNTP were removed by size exclusion chromatography. Each nucleotide type was conjugated and purified independently then mixed together to create a four-base mix for sequencing.

Class II substrates as shown in FIG. 16B were made using one pot reactions to simultaneously conjugate dye and dNTP. Alkyne-PEG-NHS was reacted with excess propargylamine dNTP. This product (Alkyne-PEG-dNTP) was then purified to homogeneity by chromatography. Multiple PEG lengths were used, with average molecular weights varying between 1K Da and 20K Da. Dendrimer cores containing a variable, discrete number (12, 24, 48, 96) of azide conjugation sites were used. Conjugation of Alkyne-Dye and Alkyne-PEG-dNTP to the dendrimer core occurred in a one pot reaction containing excess dye and dNTP species via copper-mediated click chemistry. After reacting, excess small molecule dye and dNTP were removed by size exclusion chromatography. Each nucleotide type was conjugated and purified independently then mixed together to create a four-base mix for sequencing. We note that this scheme allows the ready substitution of alternative cores, such as dextrans, other polymers, proteins, etc.

Class III polymer-nucleotide conjugates as shown in FIG. 16C were constructed by reacting 4- or 8-arm PEG NHS with a saturating mixture of biotin and propargylamine dNTP. This reaction was then purified by size exclusion chromatography. The result of this reaction was a multi-arm PEG containing a discrete distribution of biotin and nucleotides. This heterogeneous population was then reacted with dye-labeled streptavidin and purified by size exclusion chromatography. Each nucleotide type was conjugated and purified independently then mixed together to create a four-base mix for sequencing. We note that the distribution of biotin and nucleotide is tunable by the input ratio of Biotin-NH2 to propargylamine dNTP.

Example 6: Detection of Ternary Complex

Binding reactions using the multivalent binding composition having PEG polymer-nucleotide conjugates were analyzed to detect possible formation of ternary binding complex, and the fluorescence images of the various steps are illustrated in FIGS. 18A-18J. In FIG. 18A, red and green fluorescent images post exposure of DNA rolling circle application (RCA) templates (G and A first base) to 500 nM base labeled nucleotides (A-Cy3 and G-Cy5) in exposure buffer containing 20 nM Klenow polymerase and 2.5 mM Sr+2. Multivalent PEG-substrate compositions were prepared using varying ratios of 4-armed PEG-amine (4ArmPEG-NH), biotin-PEG-amine (Biotin-PEG-NH), and nucleotide (Nuc) as follows: Samples PB1 and PB5, 4ArmPEG-NH: Biotin-PEG-NH:Nuc=0.25:1:0.5; Sample PB2, 4ArmPEG-NH: Biotin-PEG-NH:Nuc=0.125:0.5:0.25; Sample PB3, 4ArmPEG-NH: Biotin-PEG-NH:Nuc=0.25:1:0.5. Images were collected after washing with imaging buffer with the same composition as the exposure buffer but containing no nucleotides or polymerase.

Contrast was scaled to maximize visualization of the dimmest signals, but no signals persisted following washing with imaging buffer (FIG. 18A, inset). In FIGS. 18B-18E, the fluorescence images showing multivalent PEG-nucleotide (base-labeled) ligands at 500 nM after mixing in the exposure buffer and imaging in the imaging buffer as above (FIG. 18B: PB1; FIG. 18C: PB2; FIG. 18D: PB3; FIG. 18E: PB5). FIG. 18F: fluorescence image showing multivalent PEG-nucleotide (base-labeled) ligand PB5 at 2.5 uM after mixing in the exposure buffer and imaging in the imaging buffer as above. In FIGS. 18G-18I, the fluorescence images showing further base discrimination by exposure of multivalent ligands to inactive mutants of Klenow polymerase (FIG. 18G: D882H; FIG. 18H: D882E; FIG. 18I: D882A, and the wild type Klenow (control) enzyme is shown in FIG. 18J).

Using multivalent ligands formulations, the base discrimination can be enabled by providing polymerase-ligand interactions having increased avidity. In addition, it is shown that increased concentration of multivalent ligands can generate higher signals, as well as various Klenow mutations that knock out catalytic activity, and can be used for avidity-based sequencing.

Example 7: Sequencing of Target Nucleic Acid Molecules Using Ternary Complexes

In order to demonstrate sequencing based on multivalent ligand reporters, 4 known templates were amplified using RCA methods on a low binding substrate. Successive cycles were exposed to exposure buffer containing 20 nM Klenow polymerase and 2.5 mM Sr+2 and washed with imaging buffer and imaged. After imaging, the substrates were washed with wash buffer (EDTA and high salt) and blocked nucleotides were added to proceed to the next base. The cycle was repeated for 5 cycles. Spots were detected using standard imaging processing and spot detection and the sequences were called using a two-color green and red scheme (G-Cy3 and A-Cy5) to identify the templates being cycled. As shown in FIG. 19A and FIG. 19B, multivalent ligands are able to provide base discrimination through all 5 sequencing cycles.

Example 8: Control of Nucleotide Dissociation from Ternary Complex

Ternary complexes are prepared and imaged as in Example 6. The complexes are imaged over varying lengths of time to demonstrate the persistence of the ternary complex, e.g., as long as 60 seconds. After a length of time, the complexes are washed with a buffer identical to the buffer used for the formation of the complexes, only lacking any divalent cation, e.g., 10 mM Tris pH 8.0, 0.5 mM EDTA, 50 mM NaCl, 0.016% Triton X100 (without SrOAc), or, in another example, the complexes are washed with a buffer identical to the buffer used for the formation of the complexes, which contains a chelating agent but otherwise lacks any divalent cation, e.g., 10 mM Tris pH 8.0, 0.5 mM EDTA, 50 mM NaCl, 0.016% Triton X100 (without SrOAc), with 100 nm-100 mM EDTA. The fluorescence from the complexes is observed over time allowing observation and quantitation of the dissociation of the ternary complexes. A representative time course of this dissolution is shown in FIG. 17.

Example 9: Extension of Target Nucleic Acid Complementary Sequence

After preparing, imaging, and dissociating ternary complexes as in Example 8, a deblocking solution is flowed into the chamber containing the bound DNA molecules, sufficient to remove the blocking moiety, such as an O-azidomethyl group, an O-alkyl hydroxylamino group, or an O-amino group, from the 3′ end of the elongating DNA strand. Either following or concurrently with this, an extension solution is flowed into the chamber containing the bound DNA molecules. The extension solution contains a buffer, a divalent cation sufficient to support polymerase activity, an active polymerase, and an appropriate amount of all four nucleotides, where the nucleotides are blocked such that they are incapable of supporting further elongation after the addition of a single nucleotide to the elongating DNA strand, such as by incorporation of a 3′-O-azidomethyl group, a 3′-O-alkyl hydroxylamino group, or a 3′-O-amino group. The elongating strand is thus extended by one and only one base, and the binding of catalytically inactive polymerase and multivalent binding substrate can be used to call the next base in the cycle.

In another example, the nucleotides attached to the multivalent substrate may be attached through a labile bond, such that a buffer may be flowed into the chamber containing the bound DNA molecules containing a divalent cation or other cofactor sufficient to render the polymerase catalytically active. Prior to, after, or concurrently with this, conditions may be provided that are sufficient to cleave the base from the multivalent substrate such that it may be incorporated into the elongating strand. This cleavage and incorporation results in the dissociation of the label and the polymer backbone of the multivalent substrate while extending the elongating DNA strand by exactly one base. Washing to remove used polymer backbone is carried out, and new multivalent substrate is flowed into the chamber containing the bound DNA molecules, allowing the new base to be called as in Example 5.

Example 10. Use of Polymer-Nucleotide Conjugates with Various Lengths of PEG Branch

The polymer-nucleotide conjugates having varying PEG arm lengths described in Example 7 were subjected to a single sequencing cycle and imaged as described in Example 5. As shown in FIGS. 20A-20G, increasing the length of the PEG branches led to increased signal up to a length corresponding to an apparent average PEG MW of 5K Da (FIGS. 20A-20D). The use of longer PEG arms than this led to decreases in the fluorescence signal for both Cy3-A and Cy5-G (FIG. 20E-20G). Quantitative measurements of signal intensity are shown graphically in FIG. 21.

Example 11: Enhancement of Multivalent Substrate Binding by Addition of Detergent

Multivalent substrates were prepared and assembled into binding complexes in the presence and absence of detergent: one set using 10 mM Tris pH 8.0, 0.5 mM EDTA, 50 mM NaCl, 5 mM SroAc, 0% TritonX100 (Condition A), and one set using 10 mM Tris pH 8.0, 0.5 mM EDTA, 50 mM NaCl, 5 mM SroAc, 0.016% Triton X100. FIG. 22 shows normalized fluorescence from these multivalent substrates bound to DNA clusters, with the substrate complexes formed in the presence (condition B) of Triton-X100 (0.016%) showing clearly enhanced fluorescence intensity.

Example 12. Evaluation of Multivalent Substrate Binding Time Courses

Multivalent substrates were prepared and assembled into binding complexes as in Example 6. Complexes were also formed under identical buffer conditions using free labeled nucleotides. Complexes were imaged over the course of 60 min. to characterize the persistence time of the complexes. FIGS. 23A-23B shows representative results. Multivalent binding complexes are stable over timescales of >60 minutes (FIG. 23B) while labeled free nucleotides dissociate in less than one minute (FIG. 23A).

While preferred embodiments of the compositions and methods disclosed herein have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the present disclosure. It should be understood that various alternatives to the embodiments of the methods and compositions described herein may be employed in any combination in practicing the methods and compositions of the present disclosure.

Claims

1. A method of determining the identity of a nucleotide in a target nucleic acid comprising:

a. providing a composition comprising: i. a target nucleic acid comprising two or more repeats of an identical sequence; ii. two or more primer nucleic acids complementary to one or more regions of said target nucleic acid; and iii. two or more polymerase molecules;

b. contacting said composition with binding composition comprising a nucleotide moiety under conditions sufficient to allow a binding complex to be formed between said nucleotide moiety and the composition of step (a); and

c. detecting said binding complex, thereby establishing the identity of said nucleotide in the target nucleic acid.

2. The method of claim 1, wherein the target nucleic acid is DNA.

3. The method of claim 1 wherein the detection of the binding complex is performed in the absence of unbound or solution-borne nucleotide moieties.

4. The method of claim 1 wherein the target nucleic acid has been replicated or amplified or has been produced by replication or amplification.

5. The method of claim 1 wherein the detectable label is a fluorescent label.

6. The method of claim 1 wherein detecting the complex comprises a fluorescence measurement.

7. The method of claim 1 wherein the binding composition comprises one type of nucleotide moieties.

8. The method of claim 1 wherein the binding composition comprises two or more types of nucleotide moieties.

9. The method of claim 8, wherein each type of the two or more types of nucleotide moieties comprises a different type of nucleotide.

10. The method of claim 9 wherein the binding composition consists of three types of nucleotide moieties and wherein each type of the three types of nucleotide moiety comprises a different type of nucleotide.

11. The method of claim 1 wherein the binding complex further comprises a blocked nucleotide.

12. The method of claim 11 wherein the blocked nucleotide is a 3′-O-azidomethyl, 3′-O-methyl nucleotide, or 3′-O-alkyl hydroxylamine.

13. The method of claim 1 wherein said contacting occurs in the presence of an ion that stabilizes said binding complex, said complex comprising a nucleotide moiety, two or more polymerase molecules, and two or more binding sites within the target nucleic acid.

14. The method of claim 1 wherein the contacting is done in the presence of strontium, magnesium, calcium ions, or any combination thereof.

15. The method of claim 1 wherein the polymerase molecule is catalytically inactive.

16. The method of claim 1 wherein the binding complex has a persistence time of greater than 2 seconds.

17. The method of claim 1, further comprising hybridizing the two or more primer nucleic acids to the one or more regions of said target nucleic acid by bringing the two or more primer nucleic acids into contact with a hybridizing composition comprising said target nucleic acid at a concentration of 1 nanomolar or less under conditions sufficient for said target nucleic acid to hybridize to the two or more primer nucleic acids in 30 minutes or less.

18. The method of claim 17, wherein the two or more primer nucleic acids are coupled to a hydrophilic polymer surface having a water contact angle of less than 45 degrees.

19. The method of claim 17, wherein the hybridization composition further comprises:

(a) at least one organic solvent having a dielectric constant of no greater than about 115 as measured at 68 degrees Fahrenheit; and

(b) a pH buffer.

20. The method of claim 17, wherein the hybridization composition further comprises:

(c) at least one organic solvent that is polar and aprotic; and

(d) a pH buffer.