A method for preparing regenerated silk fibroin conductive elastomer

Abstract

A method for preparing a regenerated silk fibroin conductive elastomer relates to an elastic hydrogel. The preparation method comprises the following steps: 1) preparing a regenerated silk fibroin solution; 2) adding a MXene dispersion to the regenerated silk fibroin solution and mixing evenly; 3) adding a crosslinking agent to the precursor solution mixed evenly in step 2); 4) pouring the mixed evenly solution into a mold to form a regenerated silk fibroin conductive elastomer hydrogel at room temperature. The silk fibroin elastomer is obtained by enzymatic crosslinking, and the reaction conditions for the preparation are mild. Thanks to the high conductivity, hydrophilicity and multifunctional groups of MXene, the obtained silk fibroin elastomer has excellent mechanical flexibility and elasticity, and can be used in flexible resistive pressure sensors; the compressibility is more advantageous than that of pure silk fibroin hydrogel.

Description

Technical Field

[0001] The present invention relates to elastic hydrogel, and in particular to a method for preparing a regenerated silk fibroin conductive elastomer with better mechanical flexibility and mechanical elasticity by mixing MXene with a regenerated silk fibroin solution. Background Art

[0002] Silk is an ancient biomaterial, and its origin can be traced back to around 3500 BC. Silk fibroin comes from silk, and has a special hydrophilic-hydrophobic segment. Silk fibroin has good biocompatibility, abundant sources, good biocompatibility, and degradability. It has a good prospect in medical health, flexible sensing, etc.

[0003] Pure silk fibroin hydrogel is relatively brittle and fragile. It breaks easily when pressed, and the mechanical strength is difficult to meet the demand. At present, inorganic substances are mostly added or carbon nanotubes or graphene are added to enhance the mechanical properties. However, the introduction of inorganic substances has changed the original biocompatibility and degradability of silk fibroin to a certain extent. The mixing of carbon nanotubes is not very closely connected to the silk fibroin. For example, Chinese patent CN113292744A discloses a silk fibroin / carbon material conductive hydrogel, in which functionalized carbon materials are introduced into the silk fibroin hydrogel, so that the functionalized carbon materials are connected to the silk fibroin molecules through chemical bonds. The chemical bonds are derived from cross-linking agents of epoxy groups, such as 1,4-butanediol diglycerol ether, which have certain toxicity and change the original biocompatibility and good skin affinity of silk fibroin.

[0004] The literature (Adv Sci. 2020 11; 7(13): 1903802) uses carbon nanotubes to reinforce silk fibroin hydrogels to construct flexible sensors that can detect multiple mechanical signals, such as pressure, strain, and bending. However, carbon nanotubes themselves are hydrophobic and fail to connect and enhance silk fibroin well.

[0005] Therefore, there are still key issues to be solved in using pure silk fibroin as a precursor material to prepare silk fibroin elastomers with high sensitivity, high biocompatibility and excellent mechanical flexibility. Summary of the invention

[0006] The purpose of the present invention is to address the above-mentioned problems and provide a regenerated silk fibroin conductive elastomer with better mechanical flexibility and mechanical elasticity, which retains the advantages of silk fibroin biocompatibility and skin-friendliness while enhancing its mechanical properties to prepare a silk fibroin elastomer tactile pressure sensor capable of detecting high performance.

[0007] The second object of the present invention is to provide a method for preparing the regenerated silk fibroin conductive elastomer, wherein MXene is mixed with a regenerated silk fibroin solution to prepare a conductive elastomer hydrogel with better mechanical flexibility and mechanical elasticity.

[0008] The third purpose of the present invention is to provide the application of the regenerated silk fibroin conductive elastomer in a resistive sensor, which can solve the problem that the prior art cannot simultaneously meet the excellent biological and mechanical properties of the regenerated silk fibroin material, thereby realizing its application in skin-attached / implantable sensor devices.

[0009] A method for preparing a regenerated silk fibroin conductive elastomer comprises the following steps:

[0010] 1) preparing a regenerated silk fibroin solution by a solution method;

[0011] 2) Add MXene nanosheet dispersion to the regenerated silk fibroin solution and mix well;

[0012] 3) adding a chemical crosslinking agent to the uniformly dispersed precursor solution;

[0013] 4) Pour the uniformly mixed solution into a mold and place it at room temperature to form a regenerated silk fibroin conductive elastomer.

[0014] In step 1), the specific steps of preparing the regenerated silk fibroin solution by the solution method can be as follows: (1) 15 g of silkworm cocoon shells are added with 12 g of Na 2 CO 3 (1) Boil the silk in 2L deionized water for 30 min and rinse with deionized water, repeating twice; (2) Dry the washed silk in an oven for 6 h; (3) Dissolve the silk in 9.5 mol / L lithium bromide solution; (5) Dialyze the completely dissolved silk; (6) Centrifuge the dialyzed silk solution to remove impurities, thereby obtaining a regenerated silk fibroin solution; In the preparation process of the regenerated silk fibroin solution, Na 2 CO 3 , to remove the sericin in the solution. The prepared regenerated silk fibroin solution needs to be subjected to reverse osmosis; the concentration of the regenerated silk fibroin solution can be 4% to 20%.

[0015] In step 2), the concentration of the MXene dispersion can be 1-10 mg / ml; the volume ratio of the regenerated silk fibroin solution to the MXene dispersion is 1:1-10:1; the MXene nanosheets not only play a conductive role, but also act as nucleation sites for silk fibroin crystallization. The size of the MXene nanosheets needs to be controlled within the range of: a sheet diameter of 5-50 um and a thickness of 10 nm-1 μm.

[0016] In step 3), the chemical cross-linking agent may be horseradish peroxidase and hydrogen peroxide, and the ratio of the horseradish peroxidase to hydrogen peroxide may be (10-15): (1-10).

[0017] In step 4), the molding time at room temperature may be 6 hours.

[0018] The regenerated silk fibroin conductive elastomer can be used in a flexible resistive pressure sensor. The specific method of the application can be: after the prepared regenerated silk fibroin conductive elastomer is pressed with a cutting mold to obtain a corresponding shape, a layer of silver paste is applied on the upper and lower surfaces thereof, two copper sheets of the same size are respectively adhered to the upper and lower surfaces of the elastomer as electrodes, two copper wires are drawn out from under the copper sheets as conductors, and the regenerated silk fibroin conductive elastomer flexible resistive pressure sensor is assembled.

[0019] The beneficial effects of the present invention are:

[0020] 1. MXene is a newly developed two-dimensional material with high conductivity, large specific surface area and excellent mechanical properties. MXene has a variety of groups on its surface, which gives MXene excellent hydrophilicity. MXene's hydrophilicity and rich surface functional groups can be well combined with silk fibroin to enhance the mechanical properties of silk fibroin hydrogel; at the same time, MXene improves electrical properties.

[0021] 2. Horseradish oxidase is used as a cross-linking agent to ensure the biocompatibility and skin-friendliness of the regenerated silk fibroin conductive elastomer.

[0022] 3. The compressibility of regenerated silk fibroin conductive elastomer is more advantageous than that of pure silk fibroin hydrogel. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a physical picture of the regenerated silk fibroin conductive elastomer.

[0024] Figure 2 is the tensile stress-strain diagram of regenerated silk fibroin conductive elastomer.

[0025] Figure 3 These are compression diagrams of regenerated silk fibroin conductive elastomer at different scales.

[0026] Figure 4 It is the electrical property of regenerated silk fibroin conductive elastomer.

[0027] Figure 5 It is the application of resistive pressure sensor based on regenerated silk fibroin conductive elastomer.

[0028] Figure 6 This is a comparison chart of the compressibility of regenerated silk fibroin conductive elastomer and pure regenerated silk fibroin elastomer. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the following embodiments will further illustrate the present invention in conjunction with the accompanying drawings.

[0030] Example 1

[0031] (1) Preparation of regenerated silk fibroin conductive elastomer

[0032] Take 1 ml of 1 mg / ml MXene dispersion and add it to 1 ml of 4% regenerated silk fibroin solution, and ultrasonicate the precursor solution for 10 minutes; add 600 μl of horseradish peroxidase solution and 300 μl of hydrogen peroxide to the mixed precursor solution and shake it evenly; pour the mixed solution into the mold and leave it at room temperature for 6 hours to form it.

[0033] (2) Preparation of flexible resistive sensors

[0034] After the regenerated silk fibroin conductive elastomer is pressed with a cutting mold to obtain the corresponding shape, a layer of silver paste is applied on its upper and lower surfaces respectively. Two copper sheets of the same size are respectively adhered to the upper and lower surfaces of the elastomer as electrodes. Two copper wires are led out from under the copper sheets as conductors to assemble a regenerated silk fibroin conductive elastomer flexible resistive pressure sensor.

[0035] Example 2

[0036] (1) Preparation of regenerated silk fibroin conductive elastomer

[0037] Take 1 ml of 10 mg / ml MXene dispersion and add it to 4 ml of 10% regenerated silk fibroin solution, and ultrasonicate the precursor solution for 10 minutes; add 400 μl of horseradish peroxidase solution and 400 μl of hydrogen peroxide to the mixed precursor solution and shake it evenly; pour the mixed solution into a mold and place it at room temperature for 6 hours to form it.

[0038] (2) The preparation of the flexible resistive pressure sensor is the same as that in Example 1.

[0039] Example 3

[0040] (1) Preparation of regenerated silk fibroin conductive elastomer

[0041] Take 1 ml of 8 mg / ml MXene dispersion and add it to 4 ml of 10% regenerated silk fibroin solution, and ultrasonicate the precursor solution for 10 minutes; add 400 μl of horseradish peroxidase solution and 40 μl of hydrogen peroxide to the mixed precursor solution and shake it evenly; pour the mixed solution into the mold and leave it at room temperature for 6 hours to form it.

[0042] (2) The preparation of the flexible resistive pressure sensor is the same as that in Example 1.

[0043] Example 4

[0044] (1) Preparation of regenerated silk fibroin conductive elastomer

[0045] Take 2 ml of 8 mg / ml MXene dispersion and add it to 4 ml of 10% regenerated silk fibroin solution, and ultrasonicate the precursor solution for 10 minutes; add 400 μl of horseradish peroxidase solution and 40 μl of hydrogen peroxide to the mixed precursor solution and shake it evenly; pour the mixed solution into the mold and place it at room temperature for 6 hours to form it.

[0046] (2) The preparation of the flexible resistive pressure sensor is the same as that in Example 1.

[0047] Example 5

[0048] (1) Preparation of regenerated silk fibroin conductive elastomer

[0049] Take 1 ml of 8 mg / ml MXene dispersion and add it to 6 ml of 10% regenerated silk fibroin solution, and ultrasonicate the precursor solution for 10 minutes; add 400 μl of horseradish peroxidase solution and 40 μl of hydrogen peroxide to the mixed precursor solution and shake it evenly; pour the mixed solution into the mold and place it at room temperature for 6 hours to form it.

[0050] (2) The preparation of the flexible resistive pressure sensor is the same as that in Example 1.

[0051] Example 6

[0052] (1) Preparation of regenerated silk fibroin conductive elastomer

[0053] Take 1 ml of 8 mg / ml MXene dispersion and add it to 8 ml of 0% regenerated silk fibroin solution, and ultrasonicate the precursor solution for 10 minutes; add 400 μl of horseradish peroxidase solution and 40 μl of hydrogen peroxide to the mixed precursor solution and shake it evenly; pour the mixed solution into the mold and leave it at room temperature for 6 hours to form it.

[0054] (2) The preparation of the flexible resistive pressure sensor is the same as that in Example 1.

[0055] Example 7

[0056] (1) Preparation of regenerated silk fibroin conductive elastomer

[0057] Take 1 ml of 10 mg / ml MXene dispersion, add it to 10 ml of 20% regenerated silk fibroin solution, and ultrasonicate the precursor solution for 10 minutes; add 600 μl of horseradish peroxidase solution and 400 μl of hydrogen peroxide to the evenly mixed precursor solution, and shake it evenly; pour the evenly mixed solution into the mold and leave it at room temperature for 6 hours to form it.

[0058] (2) The preparation of the flexible resistive pressure sensor is the same as that in Example 1.

[0059] Comparative Example 1

[0060] (1) Preparation of regenerated silk fibroin conductive elastomer

[0061] Take 1 ml of 5 mg / ml MXene dispersion and add it to 4 ml of 4% regenerated silk fibroin solution, and ultrasonicate the precursor solution for 10 minutes; add 400 μl of horseradish peroxidase solution and 100 μl of hydrogen peroxide to the mixed precursor solution and shake it evenly; pour the mixed solution into the mold and leave it at room temperature for 6 hours to form it.

[0062] (2) Preparation of pure regenerated silk fibroin elastomer

[0063] Take 4 ml of 4% regenerated silk fibroin solution, add 400 μl of horseradish peroxidase solution and 100 μl of hydrogen peroxide, and shake evenly; pour the mixed solution into a mold and place it at room temperature for 6 hours to obtain a pure silk fibroin elastomer.

[0064] like Figure 1 This is a physical picture of the silk fibroin elastomer formed in the mold in Example 1. The silk fibroin elastomer can be made into various shapes and maintain the shape. The color is black and the distribution is uniform.

[0065] like Figure 2 The stretchability of the silk fibroin elastomer in Example 2 exceeds 110%.

[0066] like Figure 3 The regenerated silk fibroin conductive elastomer formed in Example 3 can maintain good consistency when compressed 5 times at 5%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 55% and 60%, and the regenerated silk fibroin conductive elastomer has good resilience.

[0067] like Figure 4 The electrical performance diagram of the regenerated silk fibroin conductive elastomer prepared in Example 3, Example 4, Example 5, and Example 6 is shown in FIG. Figure 4It can be seen that the electrical properties of the elastomer are best when the ratio of regenerated silk fibroin solution to MXene is 4:1. In the range of 2:1 to 8:1, as the ratio of regenerated silk fibroin solution to MXene increases, the electrical properties of the regenerated silk fibroin conductive elastomer show a trend of first increasing and then decreasing.

[0068] like Figure 5 The flexible resistive pressure sensor prepared in Example 7 responds to different strain sensing curves of 5%, 10%, 15%, and 20%, indicating that it can have a good response when used as a flexible resistive pressure sensor.

[0069] Figure 6 The compression curves of the regenerated silk fibroin conductive elastomer and the pure regenerated silk fibroin conductive elastomer in Comparative Example 1 are shown in Figure 1. The pure regenerated silk fibroin conductive elastomer breaks when compressed to about 70%, but the prepared regenerated silk fibroin conductive elastomer can be compressed to 80%. It can be seen from the figure that the compressibility of the regenerated silk fibroin conductive elastomer is more advantageous than that of the pure silk fibroin conductive elastomer.

[0070] The present invention retains the advantages of biocompatibility and skin affinity of silk fibroin, and can enhance its mechanical properties to prepare a silk fibroin elastomer tactile pressure sensor capable of detecting high performance. Pure silk fibroin is fragile and has poor mechanical properties, making it difficult to become a tactile sensor. Some people use horseradish peroxidase to prepare silk fibroin elastomers, which greatly improves its mechanical elasticity, but it is easy to break. MXene is a newly developed two-dimensional material with high conductivity, large specific surface area and excellent mechanical properties, and the MXene surface has a variety of groups, which give MXene excellent hydrophilic properties. The present invention uses MXene and a regenerated silk fibroin solution to mix and prepare a conductive elastomer hydrogel with better mechanical flexibility and mechanical elasticity.

[0071] Matters not covered in the present invention are known technologies. The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a regenerated silk fibroin conductive elastomer, characterized in that The following steps are involved: 1) preparing a regenerated silk fibroin solution by a solution method; using Na2CO3 to remove sericin in the solution during the preparation of the regenerated silk fibroin solution; and performing reverse osmosis on the prepared regenerated silk fibroin solution; 2) adding MXene nanosheet dispersion to the regenerated silk fibroin solution and mixing evenly; the concentration of the MXene nanosheet dispersion is 1 to 10 mg / ml; 3) adding a chemical crosslinking agent to the uniformly dispersed precursor solution; the chemical crosslinking agent is horseradish peroxidase and hydrogen peroxide, and the ratio of the horseradish peroxidase to the hydrogen peroxide is (10-15): (1-10); 4) Pour the evenly mixed solution into a mold and place it at room temperature to form a regenerated silk fibroin conductive elastomer.

2. The method for preparing a regenerated silk fibroin conductive elastomer according to claim 1, characterized in that In step 1), the concentration of the regenerated silk fibroin solution is 4% to 20%.

3. The method for preparing a regenerated silk fibroin conductive elastomer according to claim 1, characterized in that In step 2), the volume ratio of the regenerated silk fibroin solution to the MXene nanosheet dispersion is 1:1 to 10:

1.

4. The method for preparing a regenerated silk fibroin conductive elastomer according to claim 1, characterized in that In step 2), the MXene nanosheets are used for conductivity and as nucleation sites for silk fibroin crystallization. The size of the MXene nanosheets is: a sheet diameter of 5 to 50 μm and a thickness of 10 nm to 1 μm.

5. The method for preparing a regenerated silk fibroin conductive elastomer according to claim 1, characterized in that In step 4), the molding time at room temperature is 6 hours. 6 . The regenerated silk fibroin conductive elastomer prepared by the method for preparing a regenerated silk fibroin conductive elastomer according to any one of claims 1 to 5 .

7. Application of the regenerated silk fibroin conductive elastomer in a flexible resistive pressure sensor as described in claim 6; the specific application method can be: pressing the prepared regenerated silk fibroin conductive elastomer with a cutting mold to obtain a corresponding shape, applying a layer of silver paste on the upper and lower surfaces thereof, respectively, gluing two copper sheets of the same size to the upper and lower surfaces of the elastomer as electrodes, leading out two copper wires from under the copper sheets as conductors, and assembling a regenerated silk fibroin conductive elastomer flexible resistive pressure sensor.

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