APTAMER SENSORS WITH CONTINUOUS SOLUTE PASSIVATION
A continuous sensing device for measuring at least one analyte included in a sample fluid is provided. The device 1000a includes a plurality of aptamers located in a sensor fluid 18, at least one electrode 1050, and at least one element configured to passivate the at least one electrode by continuous solute passivation. The device may further include at least one cleaning element 1092 to clean the at least one electrode.
This application claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/082,834, filed on Sep. 24, 2020; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/082,999, filed on Sep. 24, 2020; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/083,029, filed on Sep. 24, 2020; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/085,484, filed on Sep. 30, 2020; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/122,071, filed on Dec. 7, 2020; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/122,076, filed on Dec. 7, 2020; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/136,262, filed on Jan. 12, 2021; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/150,667, filed on Feb. 18, 2021; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/150,677, filed on Feb. 18, 2021; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/150,712, filed on Feb. 18, 2021; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/150,856, filed on Feb. 18, 2021; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/150,865, filed on Feb. 18, 2021; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/150,894, filed on Feb. 18, 2021; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/150,944, filed on Feb. 18, 2021; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/150,953, filed on Feb. 18, 2021; claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/150,986, filed on Feb. 18, 2021; and claims the benefit of the filing date of U.S. Patent Application Ser. No. 63/197,674, filed on Jun. 7, 2021, the disclosures of each of which are incorporated by reference herein in their entireties.
BACKGROUND OF THE INVENTIONThis section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Electrochemical aptamer sensors can identify the presence and/or concentration of an analyte of interest via the use of an aptamer sequence that specifically binds to the analyte of interest. These sensors include aptamers attached to an electrode, wherein each of the aptamers has a redox active molecule (redox couple) attached thereto. The redox couple can transfer electrical charge to or from the electrode. When an analyte binds to the aptamer, the aptamer changes shape, bringing the redox couple closer to or further from, on average, the electrode. This results in a measurable change in electrical current that can be translated to a measure of concentration of the analyte.
Major unresolved challenges for electrochemical aptamer sensors include the relatively short lifetime of the sensors and drift of the sensors (i.e., a general decrease in the accuracy of the sensors over time). These issues are especially pronounced for applications where continuous operation is required (“continuous operation” referring to multiple measurements taken over time by the same device). One of the challenges presented is the presence of species in a sample fluid other than those attributable to the target analyte that would otherwise generate the same sensor signal generated by detection of target analyte. This creates a background signal that inhibits the ability to detect small concentration analytes, and can also create inaccurate readings.
To attempt to resolve these issues, many electrochemical aptamer sensor devices include a blocking layer to reduce background electrochemical current at the working electrode. However, to date, these blocking layers have not been effective enough in reducing the background current that confounds detection of low concentrations of analyte and creates background electrochemical current which can damage the electrode or aptamers or blocking layers over time. Background current for aptamer sensors tested in whole blood, serum, interstitial fluid, or other protein and solute rich fluids is less than background current in buffer solution or dilute biofluids, because they contain species such as albumin which can non-specifically bond to the blocking layer or electrode surface and thereby help further passivate the electrode. However, these same biofluids contain proteases, enzymes, and other solutes that can also degrade the aptamer sensor over time. Fouling of sensor electrodes used in analyte detection is a significant problem such that the lifetime of sensor electrodes is significantly shortened. Devices and methods that overcome the issues of sensor degradation, inaccuracy, fouling, and short lifetime are needed.
SUMMARY OF THE INVENTIONCertain exemplary aspects of the invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be explicitly set forth below.
Many of the drawbacks and limitations stated above can be resolved by creating novel and advanced interplays of chemicals, materials, sensors, electronics, microfluidics, algorithms, computing, software, systems, and other features or designs, in a manner that affordably, effectively, conveniently, intelligently, or reliably brings sensing technology into proximity with sample fluids containing at least one analyte of interest to be measured.
Various aspects of the disclosed invention are directed to aptamer sensors (including those capable of continuous operation) that leverage the benefit of solute passivation while preventing the negative effects of direct exposure to biofluids or sample fluids.
A continuous sensing device for measuring at least one analyte included in a sample fluid is provided. The device includes a plurality of aptamers located in a sensor fluid, at least one electrode, and at least one element configured to passivate the at least one electrode by continuous solute passivation.
A continuous sensing device for measuring at least one analyte included in a sample fluid is provided. The device includes a plurality of aptamers located in a sensor fluid. The device further includes at least one electrode. The device further includes a redox tag coupled to the aptamer, the redox tag configured to change an electron transfer to between the electrode and the aptamer in response to the analyte coupling to the aptamer. The device further includes at least one cleaning element configured to clean a surface of the electrode.
A method of sensing at least one analyte included in a sample fluid is also provided. The method includes bringing an analyte included in the sample fluid into contact with an aptamer included in a sensor fluid, the contact of the aptamer with the analyte resulting in a change in the electron transfer between a redox tag and an electrode. The method further includes measuring the change in electron transfer between the redox tag and the electrode. The method further includes passivating the electrode by continuous solute passivation with at least one element.
The objects and advantages of the disclosed invention will be further appreciated in light of the following detailed descriptions and drawings in which:
As used herein, “continuous sensing” with a “continuous sensor” means a sensor that changes in response to changing concentration of at least one solute in a solution such as an analyte. Similarly, as used herein, “continuous monitoring” means the capability of a device to provide multiple measurements of an analyte over time.
As used herein, the term “about,” when referring to a value or to an amount of mass, weight, time, volume, pH, size, concentration or percentage is meant to encompass variations of ±20% in some embodiments, ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, ±0.5% in some embodiments, and ±0.1% in some embodiments from the specified amount, as such variations are appropriate to perform the disclosed method.
As used herein, the term “electrode” means any material that is electrically conductive such as gold, platinum, nickel, silicon, conductive liquid infused materials such as ionic liquids, PEDOT:PSS, conductive oxides, carbon, boron-doped diamond, nanotubes or nanowire meshes, or other suitable electrically conducting materials.
As used herein, the term “blocking layer” or “passivating layer” means a homogeneous or heterogeneous layer of molecules on an electrode which alter the electrochemical behavior of the electrode. Examples include a monolayer of mercaptohexanol on a gold electrode or as another example natural small-molecule solutes in blood that form a layer on a carbon electrode. A passivating layer as taught herein may also be referred to as a fouling layer if the solutes are endogenous and may also be referred to as a “layer of endogenous solutes.”
As used herein, the term “solute passivation” means passivation of an electrode based on aptamers based on exogenous or endogenous molecules in a sample fluid or a sensor fluid. Exogenous molecules, for example, may include mercaptohexanol on a gold or platinum electrode, while endogenous molecules may include for example peptides, hormones, amino-acids, or other solutes found in a sample fluid such as blood.
As used herein, the term “continuous solute passivation” means solute passivation of an electrode where the endogenous or exogenous molecules may degrade over time or move back into solution and leave the electrode, which opens up the electrode for additional solutes to passivate such that a passivating layer is maintained continuously on the electrode.
As used herein, the term “aptamer” means a molecule that undergoes a conformation or binding change as an analyte binds to the molecule, and which satisfies the general operating principles of the sensing method as described herein. Such molecules are, e.g., natural or modified DNA, RNA, or XNA oligonucleotide sequences, spiegelmers, peptide aptamers, and affimers. Modifications may include substituting unnatural nucleic acid bases for natural bases within the aptamer sequence, replacing natural sequences with unnatural sequences, or other suitable modifications that improve sensor function but which behave analogous to traditional aptamers. Two or more aptamers bound together can also be referred to as an aptamer (i.e. not separated in solution). Aptamers can have molecular weights of at least 1 kDa, 10 kDa, or 100 kDa.
As used herein, the term “redox tag” or “redox molecule” means any species such as small or large molecules with a redox active portion that when brought adjacent to an electrode can reversibly transfer at least one electron with the electrode. Redox tag or molecule examples include methylene blue, ferrocene, quinones, or other suitable species that satisfy the definition of a redox tag or molecule. In some cases a redox tag or molecule is referred to as a redox mediator. Redox tags or molecules may also exchange electrons with other redox tags or molecules.
As used herein, the term “optical tag” or “fluorescent tag” means any species that fluoresces in response to an optical source such as LED and whose fluorescence is detectable by a photodetector such as a photodiode. Example fluorescent tags include fluorescein and may be used in combination with other fluorescent tags or optical quenchers such a black-hole quencher dyes to change the fluorescence of the optical tag.
As used herein, the term “signaling aptamer” means an aptamer that is tagged with a redox active molecule or tag and/or contains a redox active portion itself and which provides a change in electrochemical signal when it is released from an anchor aptamer.
As used herein, the term “anchor aptamer” means an aptamer that that can bind to a signaling aptamer, and when bound to the signaling aptamer changes at least one property of the bound vs. unbound signaling aptamer such as molecular weight, diffusion coefficient, charge state, being floating in solution vs. being immobilized, or some other property which achieves the stated effect for the signaling aptamer.
As used herein, the term “folded aptamer” means an aptamer that along its length associates with itself in one or more locations creating a three-dimensional structure for the aptamer that is distinct from an “unfolded aptamer” that is a freely floating and oscillating strand of aptamer. Aptamers can also be partially folded or partially unfolded in structure or in time spent in the folded vs. unfolded states. Multiple folding configurations are also possible.
As used herein, the term “analyte” means any solute in a solution or fluid which can be measured using a sensor. Analytes can be small molecules, proteins, peptides, electrolytes, acids, bases, antibodies, molecules with small molecules bound to them, DNA, RNA, drugs, chemicals, pollutants, or other solutes in a solution or fluid.
As used herein, the term “membrane” means a polymer film, plug of hydrogel, liquid-infused film, tiny pore, or other suitable material which is permiselective to transport of a solute through the membrane by solute parameters such as size, charge state, hydrophobicity, physical structure, or other solute parameters than can enable permiselectivity. For example, a dialysis membrane is permselective by passing small solutes but not large solutes such as proteins. Membranes as understood herein need not be multiporous, for example a nanotube or nanopore can act as a permiselective filter and is therefore considered part of a membrane as understood for the present invention.
As used herein, the term “sample fluid” means any solution or fluid that contains at least one analyte to be measured.
As used herein, the term “sensor fluid” means a solution or fluid that differs from a sample solution by at least one property, and through which the sensor solution and the sample solution are therefore separated but are in fluidic connection through at least one pathway such as a membrane. The sensor solution comprises at least one aptamer as a solute.
As used herein, the term “reservoir fluid” means a solution or fluid that differs from a sample solution by at least one property, and through which the sensor solution and the reservoir solution are in fluidic connection through at least one pathway such as a membrane or a pin-hole connection. A reservoir fluid may have multiple function in a device, for example, by introducing a solute continuously or as needed by diffusion equilibrium into the sensor fluid, or for example removing unwanted solutes from a sensor fluid and acting as a “waste removal element”.
As used herein, a “device” comprises at least one sensor based on at least one aptamer, at least one sensor solution, and at least one sample solution. Devices can sense multiple samples and be in multiple configurations such as a device to measure a pin-prick of blood, or a microneedle or in-dwelling sensor needle to measure interstitial fluid, or a device to measure saliva, tears, sweat, or urine sensor, or a device to measure water pollutants or food processing solutes, or other devices which measure at least one analyte found in a sample solution.
DETAILED DESCRIPTION OF THE INVENTIONOne or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
Certain embodiments of the disclosed invention show sensors as simple individual elements. It is understood that many sensors require two or more electrodes, reference electrodes, or additional supporting technology or features which are not captured in the description herein. Sensors are preferably electrical in nature, but may also include optical such as a LED or laser excitation source and a photodetector, chemical, mechanical, or other known biosensing mechanisms. Sensors can be in duplicate, triplicate, or more, to provide improved data and readings. Sensors may provide continuous or discrete data and/or readings. Certain embodiments of the disclosed invention show sub-components of what would be sensing devices with more sub-components needed for use of the device in various applications, which are known (e.g., a battery, antenna, adhesive), and for purposes of brevity and focus on inventive aspects, such components may not be explicitly shown in the diagrams or described in the embodiments of the disclosed invention. All ranges of parameters disclosed herein include the endpoints of the ranges.
The present invention cures many of the problems of the prior art discussed above. For example, as previously described, fouling of sensor electrodes used in analyte detection is a significant problem such that the lifetime of sensor electrodes is significantly shortened. Aspects of the present invention, however, provide a device including a cleaning element, which cleans the sensor electrode. As a result, the working lifetime of the sensor electrode is significantly increased because the cleaning element is able to remove waste or fouling species from the surface of the electrode. In some device embodiments of the present invention, at least one cleaning element is included such that the cleaning element is configured to clean a surface of the electrode of waste or fouling species.
With reference to
As can be seen in
Another embodiment of a device 100 is shown in
Alternative arrangements and materials to those discussed above with respect to
Turning now to
Thus, and with reference now to
Further, although solutes (endogenous molecules 16) allow for endogenous passivation, they can also cause the passivation layer 348 to continue to grow in thickness over time, which at some point will decrease electron transfer from the redox tags 340. This not only can reduce signal strength from the sensor, but give errors in reading of the concentration of analytes. Solutions to these challenges will be presented after discussion of
An example of the analysis of the use of a membrane to pass small solutes (small target analyte) while retaining aptamers within device is shown with reference to
Several additional embodiments will be discussed below. In these additional embodiments, an increase in availability of the redox tag to the electrode can occur as a result of aptamer binding analyte, or, alternatively, without aptamer binding to an analyte. And even though each of the embodiments discussed below (and their respective figures) may show one specific example, the other the embodiments of the invention are not so limited (e.g., the various aptamer/redox tag types can be used across the various embodiments of devices disclosed herein, and vice versa.
Turning now to
Further, while the embodiment shown in
Turning now to
As described above, with respect to
It will be recognized that when the device shown in
With further reference to
With reference to
The aptamers/redox tags component of the embodiment of
Still referring to
It will be recognized that the device of the embodiment of
With reference to
And so, still referring to
With reference to
As a nonlimiting example of that shown in
As a geometrical example, consider a membrane 936 with 0.2 cm2 area and 10% porosity to the analyte, and a diffusion restrictive feature 935 that is a pinhole in materials 910 and 950 0.001 cm2 in area and 0.001 cm in length. The mass transport for a small analyte through the membrane will be equivalent to 0.02 cm2 area and the mass transport through the feature 935 0.001 cm2, which is 20× different, satisfying the above stated criteria for design as shown in
The various embodiments disclosed herein can be enabled to be user-calibrated, factory-calibrated, or calibration-free. User-calibration could for example require a pin-prick blood draw and running of a conventional assay to measure analyte concentration, and that concentration data entered into the software that runs the sensing device.
Factory-calibrated implies that the device requires calibration, but that the calibration is shelf-stable and stable for at least a portion of the use period of the device. Embodiments, such as those shown in
Calibration-free operation is possible if one could eliminate the factors that could cause a sensor signal to drift or change. Considering the embodiments of
As described above, certain aspects of the present invention are directed to devices that include a feature of continuous solute passivation. As an example, in an electrochemical aptamer sensor, background current can increase by 3× or more in just 2 hours in a buffer solution. However, when an embodiment of the present invention with continuous solute passivation is used in serum, background current may only increase by 1.3× or not at all. Solutes in various sample fluids (e.g., interstitial fluid, blood, or others), such as peptides, amino-acids, and albumin, (i.e., endogenous passivation) can continuously passivate an electrode of an electrochemical aptamer device for a period of time that is greater than the duration of passivation provided by an exogenous passivating layer alone such as mercaptohexanol. This may serve to extend the lifetime of such a device.
However, as described previously, serum or biofluids may also contain proteases, enzymes, and other solutes that can degrade a sensing device over time by attacking the aptamers, or by creating passivating or fouling layers that are too thick to allow operation of the device (e.g., due to too much protein passivation or fouling of the electrode). As illustrated in
In embodiments not including such a membrane (or in embodiments including membrane—but ones which may still result in the passage of solutes that can ultimately foul the device over time), any passivation layer may continue to grow in thickness over time, which at some point will decrease electron transfer from the redox tags. As described above, this not only can reduce signal strength from the sensor, but can also result in errors in reading of the concentration of analytes. At some point, surface fouling of one or more of the electrodes could become a bottleneck. Further, techniques used to prevent such issues enzymatic sensors simply may not apply to solution-phase aptamer sensors, because an enzyme can be ‘buried’ in a protective material such as a hydrogel and still retain its enzymatic activity, whereas an aptamer cannot be fully buried in a material because its signal transduction depends on its freedom of movement in solution. And so, an aspect of the present invention provides the ability to clean one or more electrodes in-situ of naturally passivating electrode foulants, (i.e., during use of the device). In various embodiments directed to this aspect of the present invention, working, counter, reference, or other electrodes (not all shown in the figures) may be electrically or electrochemically cleaned in-situ with connection to an electronic source (not shown). Voltages can be applied such as 1V, 2V, or other suitable voltages to briefly cause electrolysis, for example with durations of microseconds to seconds, in order to clean the electrode surface while not damaging the device 500. For example, a device with an electrode having a surface area 10× smaller than a surface area of the membrane. Alternatively, the device may include a membrane with a membrane area of 10 mm2 and a smaller electrode area of 100 μm2 could clean the tiny electrode without affecting much of the sample fluid across the rest of the device (e.g., pH effects, gas bubbles, etc.). As further example, a diamond electrode could be cleaned with dozens of current pulses, for example current pulses of 10 mA/cm2, for 100 ms with a duty cycle of 80-95% for the pulses. Typically, corrosion-resistant (noble) metals are used in biosensing such as carbon-based, diamond, gold, or platinum with a volts vs. saturated calomel electrode that are >0 V.
In an alternative embodiment, titanium, nickel, steel, copper, silicon bronze, or other metals or alloys with <0 V volts vs. saturated calomel electrode can be used such that their natural corrosion at blood pH levels will gradually remove (clean) an electrode fouling layer over time with or without electrochemical cleaning methods. These corrosion processes can be electrochemically increased or decreased by use of low pulsed or DC voltages, e.g., via anodization vs. etching. In yet another alternate example embodiment, an electrode can be used such as gold or platinum on which electrochemically and oxide layer is formed and then removed. Such a process could involve, for example, a positive potential to form a monolayer or more of oxide, an anodic potential and then a cathodic potential, which can be performed once or a plurality of times in series. Assume that each time the electrode is cleaned 0.3 to 3 nm of metal needs to be removed, then the thickness of the electrode may place a limit on how many times the electrode can be cleaned by repeat oxidative cleaning. If an electrode were 0.3 to 30 μm thick then it could be cleaned 100 to 100,000 times. The electrode cleaning could be required at every data point measurement (e.g., every 2 minutes), at least once every 24 hours, (which may be only once every 24 hours) depending on the application, which means the electrode itself could have an operational life that is at least 200 minutes (more than one hour) or even greater than 1 week or greater than 6 months.
Turning now to
Turning now to
In some embodiments, mechanical cleaning is only used as needed (daily, weekly, monthly, etc.). In another embodiment, such as, e.g., for an indwelling needle sensor (partially implanted, like Abbott's Freestyle Libra wearable), at least one electrode, such as a wire electrode, has a rubber or brush sheath, and the wire electrode mechanically extends or retracts through the sheath to clean the electrode as needed. In this embodiment, the mechanical transduction may be provided by an external solenoid located in the wearable device.
In certain embodiments of the present invention, an electrode may be inoperable for measurement of analyte while it is being cleaned. And so, in some embodiments, the present invention may include a plurality working electrodes (not shown in
With respect to embodiments of the present invention, knowing when to clean an electrode is also of value. In some embodiments of the present invention, electrical impedance of the electrode may be continuously measured to determine when a fouling layer is too thick. In other embodiments, electrical impedance may also be used to correct for sensor drift as fouling layer thickness increases. As a non-limiting example, an additional redox couple with a different redox potential than the redox couple for the aptamer (such as aptamer and redox couple 370, 372 of
With respect to embodiments of the present invention, the membranes that isolate the sample fluid from the sensor fluid can also be subject to fouling. This can, in turn, increase device lag time or even skew analyte concentrations if cells form on the membrane. Therefore, the methods taught for cleaning the electrodes in the present invention could also be applied to cleaning the surface of any membrane present in the device (such as any embodiments of devices and membranes taught herein). For example, the membrane could be a material similar to a dialysis membrane with a molecular weight cutoff of 300 Da. Onto this membrane a nano-colloidal ink such as silver or another metal can be printed and sintered at low temperatures or near room temperature (as is enabled by nano-colloidal inks), but not fully sintered such that resulting metal film remains nanoporous. This creates an electrode on the membrane that can be cleaned using one of the methods as taught previously. The electrode itself could be the membrane as well with properly tuned porosity. Other electrode coated membranes such at Pt coated Nafion membranes are possible as well. Therefore, generally the present invention may include in-situ cleaning of one electrode that is also a membrane, or which is coated onto a membrane. In an embodiment, the cleaning element includes a membrane housing the electrode, or, alternatively or in addition, the cleaning element is coated onto a membrane housing the electrode.
EXAMPLES Example 1With reference to
The experiment of Example 1 was repeated but instead of using mercaptohexanol passivation of the gold electrodes 650, 652, endogenous small molecule solutes found in blood or interstitial fluid were allowed to passivate the gold electrode 650, 652. It was found that without passivation background current was very high, but that both mercaptohexanol and endogeneous solutes were able to adequately reduce background current and enable sensor operation.
Although not described in detail herein, other steps which are readily interpreted from or incorporated along with the disclosed embodiments shall be included as part of the invention. The embodiments that have been described herein provide specific examples to portray inventive elements, but will not necessarily cover all possible embodiments commonly known to those skilled in the art.
Claims
1. A device for detecting the presence of, or measuring the concentration of, at least one analyte in a sample fluid, the device comprising:
- at least one electrode;
- a sensor fluid in communication with the at least one electrode, the sensor fluid including a plurality of aptamers freely diffusing in the sensor fluid; and
- at least one element configured to passivate the at least one electrode by continuous solute passivation.
2. The device of claim 1, wherein the element includes a membrane that is impermeable to at least one passivating solute adjacent to the at least one electrode.
3. The device of claim 1, wherein the element includes a membrane that is permeable to at least one passivating solute adjacent to the at least one electrode.
4. The device of claim 1, wherein the element includes one or more solutes of a plurality of solutes endogenous to a sample fluid.
5. The device of claim 4, wherein the sample fluid is one of blood or interstitial fluid.
6. The device of claim 2, wherein the membrane has a molecular weight cutoff that is less than the at least one element.
7. The device of claim 3, wherein the membrane has a molecular weight cutoff that is greater than the at least one element.
8. The device of claim 1, further comprising at least one reservoir fluid.
9. The device of claim 8, wherein the reservoir fluid contains the at least one element.
10. The device of claim 1, wherein one or more aptamers of the plurality of aptamers each include a redox tag; and wherein the device further includes at least one membrane in communication with the sensor fluid and adapted to be in communication with a sample fluid, wherein the membrane is permeable to analyte in a sample fluid, and is impermeable to each aptamer of the plurality of aptamers.
11. The device of claim 1, wherein the plurality of aptamers comprise a plurality of signaling aptamers and a plurality of anchor aptamers.
12. The device of claim 11, further comprising a plurality of redox tags, wherein each redox tag of the plurality of redox tags is bound to a signaling aptamer of the plurality of signaling aptamers.
13. The device of claim 10, wherein the membrane has a molecular weight cutoff of <1000 Da.
14. The device claim 1, further comprising a housing having one or more interior chambers containing the at least one electrode, sensor fluid, and element configured to passivate the at least one electrode; and
- wherein the housing is adapted to be placed outside of the body and the stratum-corneum of the skin of a subject.
15. The device of claim 1, further comprising a housing having one or more interior chambers containing the at least one electrode, sensor fluid, and element configured to passivate the at least one electrode; and
- wherein the housing is at least a portion of an in-dwelling device.
16. The device of claim 15, further comprising one or more microneedles in fluid communication with the one or more interior chambers.
17. The device of claim 1 further comprising a housing having one or more interior chambers containing the at least one electrode, sensor fluid, and element configured to passivate the at least one electrode; and
- wherein the housing is adapted to be implanted into a subject.
18. The device of claim 1, wherein the at least one element configured to passivate the electrode is located in a passivating layer adjacent to the electrode.
19. The device of claim 1, wherein the at least one element comprises an exogenous molecule.
20. The device of claim 1, wherein the at least one element comprises an endogenous solute from the sample fluid.
21. The device of claim 20, wherein the endogenous solute is configured to leave the electrode and be replaced by another molecule.
22. The device of claim 10, wherein the membrane has a molecular weight cutoff of chosen from at least one of less than 300 Da, less than 1000 Da, less than 3 kDa, less than 10 kDa, less than 30 kDa, less than 100 kDa, and less than 300 kDa.
23. The device of claim 10, wherein the membrane is configured to allow only solutes from the sample fluid to permeate therethrough, and wherein the solutes from the sample fluid include the analyte.
24. The device of claim 10, wherein the membrane is permeable to the analyte and wherein the membrane is positioned to retain the at least one element within at least 500 μm of the electrode.
25. The device of claim 1, further comprising a reservoir fluid in fluid communication with the sensor fluid.
26. The device of claim 25, wherein the reservoir fluid includes albumin, peptides, or non-natural chemical solutes with single or multiple thiol binding sites, and is configured to continuously introduce the albumin, peptides, or non-natural chemical solutes to the electrode.
27. The device of claim 26, wherein the reservoir fluid is configured to supply the at least one element to the sensor fluid, and wherein the membrane has a molecular weight cutoff less than the at least one element.
28. The device of claim 26, wherein the reservoir fluid is configured to accept waste from the sensor fluid.
29. The device of claim 1, wherein the plurality of aptamers further comprising one or more anchor aptamers immobilized via a linkage to a hydrogel.
30. The device of claim 10, wherein the membrane has a selective permeability based on size, charge, or at least one other property of the at least one element.
31. A device for detecting the presence of, or measuring the concentration of, at least one analyte in a sample fluid, the device comprising:
- a plurality of aptamers disposed in a sensor fluid;
- a plurality of redox tags, wherein each redox tag of the plurality of redox tags is individually coupled to an aptamer of the plurality of aptamers, each redox tag configured to change an electron transfer to between the electrode and the aptamer in response to the analyte coupling to the aptamer;
- at least one electrode in communication with the sensor fluid; and
- at least one cleaning element configured to clean a surface of the electrode.
32. The device of claim 31, wherein the at least one electrode further comprises a working electrode, a counter electrode, or a reference electrode.
33. The device of claim 31, further comprising a membrane at least partially housing the electrode, the electrode having a surface area 10× smaller than a surface area of the membrane.
34. The device of claim 31, wherein the electrode comprises titanium, nickel, or steel, copper, silicon bronze, or other metal or alloy with <0 V volts vs. saturated calomel, and wherein the electrode is configured to remove an electrode fouling layer from the electrode.
35. The device of claim 31, wherein the electrode is 0.3 to 30 μm thick.
36. The device of claim 31, wherein the cleaning element is configured to clean the electrode at least one of at least once every 24 hours.
37. The device of claim 31, wherein the electrode is configured to have an operational life that is at least 200 minutes, greater than 1 week, or greater than 6 months.
38. The device of claim 31, wherein the cleaning element is a polymer brush configured to mechanically clean the surface of the electrode.
39. The device of claim 38, wherein the polymer brush comprises microbeads or nanobeads configured to mechanically clean the surface of the electrode.
40. The device of claim 39, wherein the microbeads or nanobeads are configured to move in response to a stimulus from a motor, thermally responsive polymer, or external stimuli.
41. The device of claim 31, wherein the cleaning element has a density that is at least greater than 10%, greater than 100%, or greater than 1000% different than the density of water.
42. The device of claim 31, further comprising a stimulating element configured to mechanically vibrate or sonically vibrate the cleaning element.
43. The device of claim 31, wherein the cleaning element is configured to clean the electrode in response to a natural body motion or position change of a user of the device.
44. The device of claim 31, wherein the cleaning element is magnetic or electromagnetic and is configured to be moved in response to a magnetic field from an external electromagnetic transducer.
45. The device of claim 31, wherein the at least one electrode comprises a plurality of electrodes, each electrode of the plurality of electrodes configured to be cleaned at independent times and configured to be used for sensor measurement at independent times.
46. The device of claim 45, wherein at least one of the plurality of electrodes is configured to be used as a sensor after at least 1 hour of physi-absorption of the sensor fluid onto the surface of the electrode following cleaning of the electrode.
47. The device of claim 46, wherein the electrode is configured to be used as a sensing electrode for at least 1 day prior to a subsequent cleaning.
48. The device of claim 31, wherein the device is configured to continuously measure an electrical impedance of the electrode.
49. The device of claim 48, further comprising a second plurality of aptamers, each aptamer of the second plurality of aptamers configured to not respond to changes in analyte concentration in the sample fluid, and each aptamer of the second plurality of aptamers comprising a second redox tag having a redox potential different from the redox tag coupled to the aptamers of the plurality of aptamers, the second plurality of aptamers configured to measure a fouling layer thickness on the surface of the electrode.
50. The device of claim 31, wherein the cleaning element is located in the sensor fluid, in-situ.
51. The device of claim 31, wherein the cleaning element comprises a membrane housing the electrode or is coated onto a membrane housing the electrode.
52. A method of sensing an analyte in a sample fluid, the method comprising:
- bringing an analyte in the sample fluid into contact with a plurality of aptamers disposed in a sensor fluid, the contact of the plurality of aptamers with any analyte resulting in a change in electron transfer between a redox tag attached to an aptamer bound to analyte and an electrode; and
- measuring the change in electron transfer between the redox tag and the electrode;
- wherein the electrode is passivated by continuous solute passivation.
53. The method of claim 52, wherein the measuring of the change in electron transfer occurs by voltammetry, scanning wave voltammetry, amperometry, chronoamperometry, coulometry, chronocoulometry, or combinations thereof.
54. The method of claim 53, further comprising cleaning a working electrode, a counter electrode, or a reference electrode in-situ.
55. The method of claim 54, wherein the cleaning is performed electrically or electrochemically in connection to an electronic source.
56. The method of claim 54, wherein the cleaning includes removing 0.3 to 3 nm from the electrode.
57. The method of claim 54, wherein the cleaning includes pulsing a current.
Type: Application
Filed: Sep 24, 2021
Publication Date: Oct 19, 2023
Inventor: Jason Charles Heikenfeld (Cincinnati, OH)
Application Number: 18/027,395