Entrapment of nanomaterial within mesoporous fiber welded biopolymer

Abstract

A method of entrapping a material with at least one nanoscale dimension within a mesoporous fiber welded biopolymer, comprising the steps of preparing a colloidal suspension (wherein the colloidal suspension contains one or more materials with nanoscale dimensions in a compatible solvent), exposing a mesoporous fiber welded biopolymer to the colloidal suspension, entrapping within the mesoporous fiber welded biopolymer one or more materials with nanoscale dimensions, and removing solvent from the resulting composite. A mesoporous natural fiber welded biopolymer material with entrapped materials of nanoscale dimensions which exhibits properties and/or functions that are the combination of those from the mesoporous fiber welded biopolymer and the entrapped material(s) with nanoscale dimensions.

Description

REFERENCE TO RELATED APPLICATION

This application is a non-provisional of, and claims priority to and the benefits of, U.S. Provisional Patent Application No. 63/537,605 filed on Sep. 11, 2023, the entirety of which is herein incorporated by reference.

BACKGROUND

This disclosure concerns methods for incorporating nanomaterials into mesoporous natural fiber welded (NFW) biopolymer materials.

A novel product is described herein concerning mesoporous NFW biopolymer materials incorporating nanomaterials.

Cellulose is a ubiquitous and renewable biopolymer which is highly regarded for its impressive thermal and mechanical properties. The mechanical strength of cellulosic materials is primarily attributed to the native crystalline cellulose I form, which comprises an extensive hydrogen bonding network between parallel strands of β (1→4) d-linked glycosidic bonds. Conventional processing of cellulosic materials (e.g., cotton thread) involves derivatization or allomorph transitions, such as mercerization (to cellulose II), ammonia treatment (to cellulose III), or thermal treatment (to cellulose IV). Alternatively, an emergent technology known as NFW employs ionic liquids (ILs), typically 1-ethyl-3-methylimidazolium acetate (EMImAc), or other solvents (ionic or molecular) to achieve partial dissolution and modification of cellulosic materials while retaining much of the native cellulose I.

In NFW, cellulosic material thread is submerged in IL under specific conditions (time, temperature) to achieve partial dissolution of the outer layers of cellulose. Dissolution is quenched by introducing a polar cellulose non-solvent (e.g., water) to remove the IL, producing a low-surface area composite with an unmodified cellulose I interior and a more disordered cellulose shell. Welding of two adjacent biopolymer materials creates an entangled and continuous amorphous hydrogen bonding network at the interface. Our past research has used this matrix as a platform to make new functional biocomposites for catalysis, anti-microbial and ion exchange applications, energy storage, and to improve textile thermal stability.

Recently, Aiello, et al. demonstrated that specific post-NFW treatment of cotton composites will deliver xerogels with surface areas that are 3-4 orders of magnitude greater than native or fiber welded cotton. These mesoporous composites act as high surface area scaffolds for designing novel advanced functional materials (e.g., via physical entrapment of nanomaterials, covalent attachment of new chemical moieties, or nucleation/growth of nanoparticles) and the NFW welding conditions can be tuned to enhance the mechanical properties of the cellulose I interior.

With our invention described herein, we present a novel method for incorporating nanomaterials into a fiber welded mesoporous biopolymer matrix by physical entrapment of small nanomaterials within the size range of the mesopores (ca 2-50 nm diameter) from liquid suspensions.

We demonstrate the versatility of the approach with small (5 nm diameter) titanium dioxide nanoparticles (TiO₂NPs), metal organic frameworks (MOFs), and enzymes (horseradish peroxidase). So long as the nanomaterials are less than or equal to the size of the pores presented within the mesoporous matrix and can be suspended in the solvent, these methods can be universally applied across a wide range of nanomaterials, solvents, and any support matrices that can be fiber welded to become mesoporous.

In each case, our research demonstrates how the nanomaterial entrapment methods are consistent and repeatable, and offer a clear advantage over applying similar approaches within a conventionally fiber welded matrix.

With our invention, once the nanoparticles have been embedded into the pores of the mesoporous biopolymer, pathways remain open for accessing their targeted function (i.e., UV protection, nerve agent degradation, biochemical activity) and the nanomaterials do not easily leach from the support even while under extremely aggressive disturbance. Thus, we have solved long-standing problems.

SUMMARY OF DISCLOSURE

Description

This disclosure concerns entrapment of nanomaterial into fiber welded mesoporous biopolymer.

A novel product is described herein concerning NFW mesoporous biopolymer materials incorporating nanomaterials.

DESCRIPTION OF THE DRAWINGS

The following description and drawings set forth certain illustrative implementations of the disclosure in detail, which are indicative of several exemplary ways in which the various principles of the disclosure may be carried out. The illustrated examples, however, are not exhaustive of the many possible embodiments of the disclosure. Other objects, advantages and novel features of the disclosure will be set forth in the following detailed description when considered in conjunction with the drawings.

FIG. 1 illustrates a scanning electron microscopy (SEM) image (top) and energy-dispersive X-ray spectroscopy (EDS) map (bottom) of a mesoporous biopolymer textile after treatment with 10 mg mL⁻¹ TiO₂NP suspension and subsequent rinsing confirming the presence of titanium in the sample matrix. The EDS map corresponds to the area shown on the SEM image. FIG. 1 also illustrates a UV-Vis spectral overlay of mesoporous and non-mesoporous, unwelded biopolymer samples after their exposure to 100 mg mL⁻¹ TiO₂NPs in ultra-pure water. UPF values associated with these spectra have been included in their respective colors. Spectra were collected by a JASCO V-670 spectrometer with 60 mm integrating sphere at the following settings: % T, slow response, 0.5 nm UV/Vis bandwidth, 200 nm min⁻¹ scan speed, 400-290 nm spectral range, 0.5 nm data interval, 20.0 nm NIR bandwidth, continuous scan mode.

FIG. 2 presents SEM images showing (i) a high resolution image of MOF UiO-67 that was integrated within the mesoporous NFW fabric, (ii) lower resolution image of MOF UiO-67 integrated within the welded fiber cross section, (iii) image of cross sectional area mapped using EDS and (iv) map and spectra of region featured in (iii), highlighting the zirconium metal (from MOF UiO-67) distribution of MOF UiO-67 throughout the matrix. The mesoporous biopolymer textile was treated with 1 mg mL⁻¹ UiO-67 MOF suspension. FIG. 2 also illustrates UV-Vis data monitoring the degradation of methyl paraoxon (DMNP) nerve agent mimic over time showing the catalytic ability of samples prepared from mesoporous biopolymers. Absorbance values were measured at 400 nm, corresponding to the production of deprotonated 4-nitrophenol product. Concentrations at time intervals were baseline subtracted at 750 nm, and the change in concentration due to the base-catalyzed hydrolysis of DMNP was subtracted from each time point.

FIG. 3 illustrates UV-Vis spectroscopy of fiber welded mesoporous cellulose-horseradish peroxidase (HRP) composites demonstrating the conversion of 4-aminoantipyrine by entrapped HRP in mesoporous cellulose after initial coating (left), a single 5 min water rinse (middle), and following prolonged storage in water for multiple weeks (right). FIG. 3 illustrates UV-Vis comparing the activity of mesoporous-HRP composites and non-welded-HRP controls following a series of 3 rinses in water. FIG. 3 illustrates optical images showing the physical resilience of mesoporous-HRP composites (left) substrates compared to nonwelded-HRP controls (right) which unravel into loose threads after prolonged exposure to water.

DETAILED DESCRIPTION OF THE INVENTION

This disclosure concerns entrapment of nanomaterial into mesoporous fiber welded biopolymer.

A novel product is described herein concerning mesoporous NFW biopolymer materials incorporating nanomaterials.

With our invention described herein, we present a novel method for incorporating nanomaterials into a fiber welded mesoporous biopolymer matrix by physical entrapment of small nanomaterials within the size range of the mesopores (ca 2-50 nm diameter) from liquid suspensions.

We demonstrate the versatility of the approach with small (5 nm diameter) TiO₂NPs, MOFs, and enzymes (HRP). So long as the nanomaterials are less than or equal to size of the pores presented within the mesoporous matrix, or have a dimension that is indeed nanoscale and can be incorporated and fully entrapped, and can be suspended in the solvent, these methods can be universally applied across a wide range of nanomaterials, solvents, and any biopolymer support matrices that can be fiber welded to become mesoporous.

In each case, our research demonstrates how our nanomaterial entrapment methods are consistent and repeatable, and offer a clear advantage over applying similar approaches within a conventionally fiber welded matrix.

With our invention, once the nanoparticles have been embedded into the pores of the mesoporous biopolymer, pathways remain open for accessing their targeted function (e.g., UV protection, nerve agent degradation, biochemical activity) and the nanomaterials do not easily leach from the support even while under extremely aggressive disturbance. Thus, we have solved long-standing problems.

Physical Entrapment of Nanomaterials, Frameworks, and Macromolecules into Pores of NFW Mesoporous Biopolymer Material

Nanomaterials (TiO₂ Nanoparticles)

Example 1

The ability to readily collapse the mesoporous cellulose through solvent exposure and drying presents an opportunity to entrap functional nanomaterials into a biopolymer matrix. As matrix collapse occurs, colloidally suspended nanomaterials in solution around the biopolymer material can be drawn into its expanded surface structure via capillary action. In theory, for this function to impart optimal loadings of nanomaterials, the material of interest must be on the same size scale as the pores on the mesoporous surface (2-50 nm). Secondly, they must be stable and properly dispersed as a colloidal suspension, preventing aggregation of particles in solution that would increase the effective size of the nanomaterial and prevent entry into a mesopore.

The first nanomaterial selected for a demonstration of this process are 5 nm TiO₂NPs. Colloidal suspensions of TiO₂NPs are prepared by adding nanoparticle powder to 18 MΩ cm⁻¹ water at concentrations of 1 mg mL⁻¹, 10 mg mL⁻¹, and 100 mg mL⁻¹. All suspensions were prepared the hour before fabrication of the composite materials and were not reused for further testing to mitigate aggregation effects. Each of these TiO₂NP suspensions demonstrated high stability in water for over two months at room temperature, with no settling or aggregation observed over this time period. Next, a fiber welded, mesoporous biopolymer material (size ca. 4 in²) is exposed to the TiO₂NP solutions by submersion in ˜60 mL of the desired TiO₂NP suspension (60 seconds, room temperature) and gently swirled before being drip-dried to remove excess fluid adhering to the surface. Then, the samples were pressed between Teflon sheets under a 5 lbs. weight for pre-drying in an oven (60° C., 24 h) then transferred into a vacuum oven (60° C., 24 h) with the weight removed to complete the collapse of the mesoporous scaffolding around the TiO₂NPs. The samples were then rinsed in 60 mL water for three days on a shaker table at 75 rpm to attempt to remove all NPs not fully integrated into the sample matrix, with the water emptied and refreshed after the first rinsing day. Following this rinsing procedure, the samples were subjected to the same drying process as before (60° C., 24 hours in drying oven and then vacuum oven) prior to being sealed in plastic bags under N₂ in an atmosphere dry box.

Scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) mapping of the mesoporous textile following TiO₂NP entrapment and rinsing confirmed the presence of a high level of titanium remaining in the sample matrix (FIG. 1A). The mesoporous textile containing TiO₂NPs also offered superior UV-protection compared to unmodified biopolymer material prepared under the same conditions. UPF values were calculated using the JSCO VWUP-712 UPF Measurement Program for V-600 series spectrometers, in accordance with ASTM Standard D6603.

Samples of mesoporous biopolymer exposed to the highest concentration of TiO₂NPs had a UPF value of 201±16, vastly outperforming the samples of native aida cloth (12.1±0.3) (FIG. 1). These results demonstrate the fabrication of a textile far surpassing the FDA requirement for an “excellent” ultraviolet protectant textile (UPF 50+) that is retained after a prolonged rinse in water, with a control sample failing to meet the FDA standard for a textile to be considered ultraviolet protectant (UPF 15).

Metal Organic Frameworks (MOFs)

Example 2

The second nanoscale material selected for a demonstration of this process is the zirconium-based metal organic framework (MOF), UiO-67. It was selected as a viable candidate because of its nanoscale size, suspendability in water, and ability to catalyze the degradation of chemical warfare agents. Colloidal aqueous suspensions of UiO-67 were prepared at a concentration of 1 mg mL⁻¹ and subsequently rinsed in the same manner as described above for the TiO₂NP samples. Once the final rinse of the mesoporous biopolymer-MOF composite was completed, the samples were stored in water to keep the textile matrix swelled for catalytic testing, as previous catalytic studies suggest drying of cellulose-nanoparticle composites can lead to an unwanted decrease in catalytic performance following sample drying.

SEM and EDS show the presence of zirconium in the mesoporous matrix after the 3-day rinsing procedure and storage in water for over 40-days, suggesting the samples still retained a significant quantity of MOF (FIG. 2). UV-vis spectroscopy (Thermo-Fisher NanoDrop™) was used to assess the catalytic effectiveness the mesoporous biopolymer composite containing entrapped UiO-67 MOF by monitoring the hydrolysis of DMNP, an analog of sarin gas, into 4-nitrophenolate (4-NP) and dimethyl phosphate.

Samples containing MOF were compared to a control of DMNP injected into a pure buffer solution with no added textile, as well as controls prepared from non-welded, non-mesoporous biopolymer materials treated with MOF. Testing demonstrated that the samples fabricated from mesoporous biopolymer remained catalytically active, even after their rinse and prolonged storage (FIG. 2).

Next, a running sum of the net conversion percentage due to the presence of MOF was taken and divided by the mass of sample present in each trial to standardize the percent enhancement to the grams of biopolymer composite material used. Our results of this assessment clearly depict the benefits of fabricating functional biocomposites from M-NFW over untreated cotton cloth.

Enzymes/Proteins (Horseradish Peroxidase)

Example 3

The third nano-sized material selected for a demonstration of this process is the enzyme HRP, representing the field of biological materials. HRP was selected due to its compatible size (hydrodynamic diameter of ca. 8 nm) with the resident pores of fiber welded mesoporous biopolymer.

Aqueous suspensions of HRP were prepared at a concentration of 1 mg mL⁻¹ and samples were prepared by dip-coating, similar to the methods described for incorporating TiO₂NPs and MOF. Mesoporous NEW substrates functionalized with HRP were dried at ambient pressures at 60° C., and compared to non-welded control samples treated in a similar manner.

HRP-functionalized substrates were tested for activity by means of a common colorimetric assay in which a colored dye is produced through the conjugation of phenol and 4-aminoantipyrine in the presence of peroxidase enzyme and hydrogen peroxide. HRP loading was assessed by comparing the rates of conversion of 4-aminoantipyrine and phenol, as measured by a time-dependent increase in absorbance at 510 nm, after initial coating and iterative rinse cycles using UV-vis spectroscopy (Jasco V-550 Spectrophotometer) (FIG. 3).

Following an initial loss in activity due to the removal surface-bound enzyme, the rate of 4-aminoantipyrine conversion was consistent for mesoporous NFW substrates containing entrapped HRP, suggesting a nonchanging quantity of active enzyme confined in the mesopores. This activity was consistent even after samples were stored in water for several weeks. Unlike their welded mesoporous counterpart, non-welded samples treated with HRP solution exhibited consistent decreases in activity signifying continual loss of HRP with each rinse (FIG. 3). In addition to superior retention of HRP, the welding procedure also bolstered the structural integrity of the composite, which maintained its structure throughout prolonged solvent exposure and many experiments. In contrast, the non-welded HRP samples unraveled into loose fibers after prolonged exposure to water (FIG. 3).

Our approach is not limited by the type of nano-sized material. We have demonstrated that a variety of small nanomaterials (with diameters less than the maximum diameter of mesopores) can be incorporated and entrapped within a fiber welded mesoporous biopolymer matrix. So long as the nanoparticle diameter is within the same range as the size distribution of pores in the mesoporous biopolymer material, this approach will work.

Our approach is not limited by the type of biopolymer that can be used as the mesoporous biopolymer support matrix. Our research demonstrates that a wide-variety of natural biopolymer materials can be transformed from low-surface area materials to high surface area mesoporous supports through NFW and subsequent non-polar gradient solvent exchange. We have demonstrated this approach is effective at preparing the following but not limited to mesoporous cellulose (cotton), lignocellulose (linen), silk and chitin.

Advantages and New Features

• • (1) This disclosure demonstrates the ability to entrap nanomaterials, metal-organic frameworks, or macromolecules into a mesoporous NFW biopolymer material.
  • (2) Our disclosure reveals that once nanomaterials are entrapped into the mesoporous NFW biopolymer material, the structure of the supporting matrix will prevent nanomaterial from leaching out of the matrix.
  • (3) Our disclosure enables mesoporous natural biopolymer materials to be transformed into functional biopolymer composite materials by entrapping nanomaterials, metal-organic frameworks, or macromolecules with size (diameter) similar to the diameter of the mesopores.
  • (4) This disclosure applies to any nanomaterial with at least one nanoscale (<100 nm) dimension.
  • (5) This disclosure applies to any biopolymer that can be fiber welded with any fiber welding solvent into a mesoporous biopolymer matrix from its native state.

The above examples are merely illustrative of several possible embodiments of various aspects of the present disclosure, wherein equivalent alterations and/or modifications will occur to others skilled in the art upon reading and understanding this specification and the annexed drawings. In addition, although a particular feature of the disclosure may have been illustrated and/or described with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Also, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in the detailed description and/or in the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”.

Claims

1. A method of entrapping one or more materials with nanoscale dimensions within a mesoporous fiber welded biopolymer comprising the steps of:

preparing a colloidal suspension; wherein the colloidal suspension comprises one or more materials with nanoscale dimensions dispersed within a solvent;

exposing a mesoporous fiber welded biopolymer comprising a mesoporous network to the colloidal suspension; and

uptaking within the mesoporous fiber welded biopolymer one or more materials with nanoscale dimensions from the colloidal suspension.

2. The method of entrapping one or more materials with nanoscale dimensions within a mesoporous fiber welded biopolymer of claim 1 further comprising the steps of:

removing the solvent from the mesoporous fiber welded biopolymer;

causing the collapse of the mesoporous network; and

entrapping the one or more materials with nanoscale dimensions within the fiber welded biopolymer.

3. The method of entrapping one or more materials with nanoscale dimensions within a mesoporous fiber welded biopolymer of claim 1 further comprising the steps of:

rinsing the mesoporous fiber welded biopolymer containing the entrapped material with nanoscale dimensions with solvent; and

removing any transient materials with nanoscale dimensions which were not partially or totally entrapped within the mesoporous fiber welded biopolymer.

4. The method of entrapping one or more materials with nanoscale dimensions within a mesoporous fiber welded biopolymer of claim 2 further comprising the steps of:

rinsing the mesoporous fiber welded biopolymer containing the entrapped materials with nanoscale dimensions with solvent; and

removing any transient materials with nanoscale dimensions which were not totally entrapped within the mesoporous fiber welded biopolymer.

5. The method of entrapping one or more materials with nanoscale dimensions within a mesoporous fiber welded biopolymer of claim 3 further comprising the step of:

removing the solvent from the mesoporous fiber welded biopolymer containing the entrapped material with nanoscale dimensions.

6. The method of entrapping one or more materials with nanoscale dimensions within a mesoporous fiber welded biopolymer of claim 4 further comprising the step of:

removing the solvent from the mesoporous fiber welded biopolymer containing the entrapped materials with nanoscale dimensions.

7. A mesoporous natural fiber welded (NFW) biopolymer material with entrapped materials of nanoscale dimensions made from the steps of:

preparing a colloidal suspension; wherein the colloidal suspension comprises one or more materials with nanoscale dimensions in a solvent;

exposing a mesoporous fiber welded biopolymer to the colloidal suspension;

entrapping within the mesoporous fiber welded biopolymer the one or more materials with nanoscale dimensions; and

removing the solvent from the mesoporous fiber welded biopolymer containing the entrapped materials with nanoscale dimensions.

8. The mesoporous NFW biopolymer material incorporating one or more materials with nanoscale dimensions of claim 7 wherein

the composite exhibits a property and/or function imparted by the biopolymer; and

the composite exhibits a property and/or function imparted by the embedded material(s) with nanoscale dimensions.

9. A mesoporous NFW biopolymer material incorporating one or more materials with nanoscale dimensions comprising:

a mesoporous natural fiber welded biopolymer; and

one or more materials with nanoscale dimensions incorporated into the mesoporous natural fiber welded biopolymer

wherein the mesoporous natural fiber welded biopolymer comprises one or more of cellulose, chitin, chitosan, silk, keratin, or any other biopolymer or biopolymer material that is made mesoporous using natural fiber welding, wherein natural fiber welding is a process by which native, recycled, or combined biopolymer(s) is treated with ionic liquid to partially solvate the biopolymer and evolve a mesoporous material, and

wherein the one or more materials with nanoscale dimensions comprise nanoparticles, metal-organic frameworks, macromolecules, clays, or other materials with at least one dimension being measured at less than 100 nanometers.