High-strength high-toughness silk fibroin-based material and preparation method and application thereof

Abstract

This invention belongs to the field of biofunctional polymer materials technology, and relates to a high-strength, high-toughness silk fibroin-based material, its preparation method, and its applications. This material possesses a composite cross-linked network; the composite cross-linked network consists of a chemical cross-linked network formed between silk fibroin molecules and a physical cross-linked network formed by the entanglement of silk fibroin and nanofibers. The silk fibroin has a regular and uniform structure. β The material exhibits a folded crystalline structure with partially oriented nanofibers. It is prepared by adding a nanofiber dispersion to a silk fibroin precursor solution of specific composition and ratio, followed by uniform dispersion and then chemical cross-linking under visible light at 25–37°C to obtain a silk fibroin-nanofiber composite hydrogel. This hydrogel is then subjected to gradient ethanol treatment and vacuum drying. This material can be applied to biomedical materials such as biodegradable bone screws and plates. This invention achieves a balance between high strength and high toughness in silk fibroin-based materials.

Description

Technical Field

[0001] This invention belongs to the field of biofunctional polymer materials technology, and relates to a high-strength and high-toughness silk fibroin-based material, its preparation method and application. Background Technology

[0002] Silk fibroin (SF), as a natural biomass material, has attracted much attention in the field of biomedical materials due to its excellent biocompatibility, tunable biodegradability, ease of processing, and wide availability of raw materials, especially showing great potential in the repair of hard tissues such as orthopedic implants. Silk fibroin can be obtained from natural silkworm cocoons through degumming. Through different processing techniques, various forms of silk fibroin-based materials, such as films, hydrogels, and porous scaffolds, can be prepared. Its degradation products are non-toxic and harmless amino acids and peptides, avoiding the stress shielding and secondary surgical removal problems associated with traditional metal orthopedic materials.

[0003] However, the mechanical properties of silk fibroin-based materials prepared by existing technologies still have significant bottlenecks: the excellent mechanical properties of natural silk fibers depend on their specific intermolecular interactions and secondary structures. However, the molecular structure of silk fibroin is destroyed and the molecular weight is reduced during the regeneration process. Furthermore, conventional preparation processes cannot controllably reproduce the regular crystalline structure and amorphous structure distribution of natural fibers, making it difficult for existing silk fibroin-based materials to simultaneously possess both high strength and high toughness.

[0004] For example, the literature (Journal of the Mechanical Behavior of Biomedical Materials, 2023, 147: 106133), (ACS Applied Materials & Interfaces, 2017, 9(20): 17489-17498) and patent application CN119842098A all describe silk fibroin-based materials prepared by recrystallization of chemically cross-linked hydrogels induced by alcohol treatment. Their compressive modulus is usually only 1~330MPa and their toughness is insufficient.

[0005] The literature (Nature Materials, 2020, 19(1): 102-108; Advanced Materials, 2024, 36(23): 2308748) prepared high-strength silk fibroin-based materials by a high-temperature and ultra-high-pressure molding strategy. Although the compressive modulus can reach 3.8~7.8GPa, the bending fracture strain (one of the important indicators reflecting the toughness of materials. Under the same material type and test conditions, the higher the value, the greater the deformation that the material can withstand before fracture and the better the toughness; the lower the value, the stronger the brittleness and the worse the toughness) is only 1.4~2.5%. At the same time, this high-strength silk fibroin-based material requires harsh processing conditions such as high temperature (145℃) and ultra-high pressure (632MPa), resulting in high production costs and complex processes, which is not conducive to large-scale production.

[0006] To address the aforementioned issues, a new method is urgently needed to prepare silk fibroin-based materials that possess both high strength and high toughness. Summary of the Invention

[0007] The purpose of this invention is to solve the problems existing in the prior art and to provide a high-strength and high-toughness silk fibroin-based material, its preparation method and application.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a high-strength and high-toughness silk fibroin-based material involves adding a nanofiber dispersion to a silk fibroin precursor solution and dispersing it uniformly, then performing visible light-induced chemical cross-linking at 25-37°C to obtain a silk fibroin-nanofiber composite hydrogel. The silk fibroin-nanofiber composite hydrogel is then subjected to gradient ethanol treatment and vacuum drying to obtain the high-strength and high-toughness silk fibroin-based material.

[0010] The silk fibroin precursor solution was obtained by mixing a silk fibroin solution, a tris(2,2'-bipyridine)ruthenium(II) chloride hexahydrate solution (hereinafter referred to as Ru solution), and a sodium persulfate (SPS) solution. In the silk fibroin precursor solution, the mass fraction of silk fibroin was 13-17%, the mass fraction of tris(2,2'-bipyridine)ruthenium(II) chloride hexahydrate (hereinafter referred to as Ru) was 0.075-0.15%, and the mass fraction of sodium persulfate was 0.2-0.4%.

[0011] Alternatively, the silk fibroin precursor solution is obtained by mixing silk fibroin solution, riboflavin and sodium persulfate solution; in the silk fibroin precursor solution, the mass fraction of silk fibroin is 13~17%, the mass fraction of riboflavin is 0.056~0.086%, and the mass fraction of sodium persulfate is 0.2~0.4%.

[0012] In the above process, visible light initiates chemical cross-linking (either Ru / SPS or riboflavin / SPS system), which causes the silk fibroin molecules to form a chemical cross-linking network. At the same time, the silk fibroin cross-linking network and nanofibers form an intertwined structure through tight physical entanglement. Subsequently, after gradient ethanol treatment and vacuum drying, the silk fibroin is induced to form a β-sheet crystalline structure, i.e., a physical cross-linking network.

[0013] The key to this invention lies in controlling the chemically cross-linked silk fibroin-nanofiber composite hydrogel to be a hydrogel with a moderate cross-linking density (moderate cross-linking density). Cross-linking density refers to the number of cross-linking points per unit volume of hydrogel, a concept within the atomic scale. Existing characterization techniques cannot provide absolute quantitative characterization, but the relative chemical cross-linking point content of different hydrogels can be indirectly reflected by the peak values ​​of corresponding characteristic peaks in the fluorescence spectrum. The hydrogel formed by using any of the above-mentioned silk fibroin precursor solution formulations is a hydrogel with a moderate cross-linking density. Hydrogels formed with initiators (Ru and SPS, or riboflavin and SPS) mass fractions below a certain limit in any of the above-mentioned systems exhibit characteristic peak values ​​in their fluorescence spectra that are lower than those of the moderate cross-linking density group; these are classified as "low cross-linking density hydrogels." Hydrogels formed with mass fractions above the certain limit exhibit characteristic peak values ​​in their fluorescence spectra that are higher than those of the moderate cross-linking density group; these are classified as "high cross-linking density hydrogels."

[0014] If the gradient ethanol treatment and vacuum drying are performed on a hydrogel with "low crosslinking density" or "high crosslinking density" instead of a hydrogel with "medium crosslinking density," the structure described in this invention cannot be formed, nor can the high strength and high toughness effect be achieved. Specifically, "low crosslinking density" hydrogels have poor initial forming ability, which is not conducive to the initial material (silk fibroin hydrogel) forming support, i.e., it cannot form a silk fibroin chemical crosslinking network with sufficient supporting capacity; it is also not conducive to the regular and uniform arrangement of the β-sheet structure formed in the subsequent gradient ethanol treatment and vacuum drying process. "High crosslinking density" hydrogels have shorter hydrophobic segments, which is not conducive to the formation of the β-sheet crystalline structure and the regular and uniform arrangement of the β-sheet crystalline structure in the subsequent gradient ethanol treatment and vacuum drying process.

[0015] As a preferred technical solution:

[0016] The preparation method of the high-strength and high-toughness silk fibroin-based material described above has a visible light intensity of 20~50mW / cm. 2 The visible light irradiation time is 15~60min.

[0017] The preparation method of the high-strength and high-toughness silk fibroin-based material described above involves a nanofiber dispersion with a solid content of 1%, and a nanofiber mass fraction of 0.3-1.5% of the total solids in the mixture of silk fibroin precursor solution and nanofiber dispersion.

[0018] The preparation method of the high-strength and high-toughness silk fibroin-based material described above involves a gradient ethanol treatment process divided into five stages. The volume concentration of the ethanol aqueous solution used in each stage increases sequentially within the range of 10% to 100%. The treatment time for each stage is 1 to 2 hours, and the treatment temperature is 25 to 37°C.

[0019] The preparation method of the high-strength and high-toughness silk fibroin-based material described above involves a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol aqueous solution of 1:10~50.

[0020] The preparation method of the high-strength and high-toughness silk fibroin-based material described above involves a vacuum drying process at a temperature of 25°C, a pressure of ≤1 kPa, and a time of 8~24 h.

[0021] The present invention also provides a high-strength and high-toughness silk fibroin-based material, which is prepared by the preparation method of a high-strength and high-toughness silk fibroin-based material as described in any of the preceding claims;

[0022] The high-strength and high-toughness silk fibroin-based material has a composite cross-linked network. The composite cross-linked network consists of a chemical cross-linked network formed between silk fibroin molecules and a physical cross-linked network formed by the entanglement of silk fibroin and nanofibers. The silk fibroin has a regular and uniform β-sheet crystalline structure, and the nanofibers have a partially oriented structure.

[0023] As a preferred technical solution:

[0024] The high-strength and high-toughness silk fibroin-based material described above uses nanofibers that are oxidized bacterial cellulose nanofibers, silk fibroin nanofibers, or collagen nanofibers; the aspect ratio of the nanofibers is 70~110:1.

[0025] The high-strength and high-toughness silk fibroin-based material described above has a compressive modulus ≥0.8GPa and a bending fracture strain ≥80%.

[0026] This invention also provides an application of a high-strength, high-toughness silk fibroin-based material as described in any of the preceding claims, applicable to the field of biomedical materials. It shows promising application prospects in orthopedics and other biomedical materials fields, including the construction of internal fixation plate and screw systems for fractures, such as bone plates and screws for hard tissue implants. It is foreseeable that, through the combination of 3D printing, CNC machining, and other personalized customization methods, it can be further developed into a multifunctional high-strength, high-toughness medical material, for example, as a bioactive scaffold material such as a drug-eluting scaffold.

[0027] Invention principle:

[0028] This invention innovatively synthesizes a silk fibroin-based functional material with both high strength and high toughness by further optimizing the reinforcement and toughening effect through the interaction and functional synergy between homogenization crystallization and nanofibers, based on the synthesis of SF chemically cross-linked hydrogels with moderate cross-linking density, uniform cross-linking network, and no bubble generation. The moderate cross-linking density and uniform chemical cross-linking network facilitate the movement of hydrophobic SF segments to form a uniformly distributed β-sheet structure. Simultaneously, a technical strategy combining gradient ethanol treatment and vacuum drying post-treatment maximizes the formation of homogenized crystals in the SF hydrogel.

[0029] The core principles of this invention are as follows:

[0030] First, an SF chemically cross-linked hydrogel with appropriate cross-linking density was prepared using a cross-linking reaction system that does not generate bubbles. The generation of bubbles in the cross-linking reaction system (such as in the conventional horseradish peroxidase system) is detrimental to the subsequent formation of homogenized structures and the improvement of mechanical properties. Regarding the uniformity of the hydrogel's cross-linking network, a higher uniformity is more conducive to improving the regularity of the subsequent β-sheet crystalline structure distribution, avoiding stress concentration and other problems that reduce the material's mechanical properties. However, regarding cross-linking density, it is not the conventional understanding that a higher cross-linking density necessarily leads to stronger mechanical properties. This is because an excessively high chemical cross-linking density of the hydrogel is detrimental to the formation of β-sheet crystalline structures and the regular arrangement of crystalline structures during subsequent processing, while an excessively low cross-linking density is detrimental to the initial molding support of the material and the homogenization shrinkage during subsequent processing. Both of these factors combined result in poor improvement in the material's mechanical strength. The combination of gradient ethanol treatment and vacuum drying post-treatment aims to maximize the combined protection of internal homogenization recrystallization and macroscopic structural homogenization shrinkage of the material, with significantly better results than single high-concentration ethanol treatment and natural air drying.

[0031] Building upon this foundation, nanofibers, such as oxidized bacterial cellulose nanofibers (OBC), silk fibroin nanofibers, and collagen nanofibers, are further uniformly incorporated into the SF hydrogel system. The appropriate addition of nanofibers facilitates interaction and functional synergy with the homogenization crystallization during the post-treatment of the SF hydrogel at a suitable cross-linking density, thereby significantly enhancing the material's strength and toughness. Specifically, the formation of homogeneous crystalline structures in moderately cross-linked silk fibroin hydrogels further strengthens the physical entanglement and hydrogen bonding between the silk fibroin cross-linking network and the nanofibers, while also promoting the formation of some nanofiber orientation structures. Ultimately, this leads to the formation of a highly efficient reinforcing and toughening network structure between silk fibroin and nanofibers.

[0032] More specifically, a silk fibroin-nanofiber composite hydrogel with a moderately appropriate cross-linking density is first formed based on chemical cross-linking. Further gradient ethanol treatment and vacuum drying post-treatment "mildly" induce the transformation of SF molecular chains from random coils to β-sheets, thereby forming a composite cross-linking network. This simultaneously enhances the interaction between the silk fibroin cross-linking network and the nanofibers, and improves the partial orientation of the nanofibers. The gradient ethanol treatment combined with vacuum drying post-treatment facilitates the formation of a "slow" homogenized crystalline structure and the homogenization shrinkage of the material, thus avoiding the heterogeneous crystallization and material shrinkage caused by the initial formation of a dense crystalline structure on the material surface. The formation of the related homogenized crystalline structure further strengthens the physical entanglement and hydrogen bonding between the silk fibroin cross-linking network and the nanofibers, while also promoting the formation of partially oriented nanofiber structures. The interaction regulation and functional synergy between the related homogenized crystalline structure and the nanofibers effectively enhance the strength and toughness of the material, thus preparing a silk fibroin-based functional material with both high strength and high toughness. The overall process is gentler than single-concentration high-concentration ethanol treatment, high-temperature drying, freeze drying, or other treatments. The resulting β-sheet crystalline regions are more regular and uniform, the interaction between the silk fibroin cross-linking network and the nanofibers is stronger, and the orientation of the nanofibers is better, thus exhibiting better shape retention and high strength and toughness.

[0033] Compared with existing technologies, such as patent CN106479195B, which can only form "intertwined entanglement between nanofibers and silk fibroin molecular chains", the present invention forms a composite structure consisting of a chemical cross-linking network between silk fibroin molecules, a physical cross-linking network in which the silk fibroin cross-linking network and nanofibers are intertwined, a partially oriented structure of nanofibers, and a relatively regular β-sheet crystalline structure of silk fibroin. Patent CN106479195B does not involve the chemical and physical cross-linking networks (crystallization) of silk fibroin and the interaction structure between the related networks and nanofibers. Furthermore, in prior art concerning silk fibroin-based materials, those with higher strength than this invention have significantly lower toughness, and those with higher toughness have significantly lower strength. For example, existing methods for preparing physically cross-linked hydrogels of silk fibroin by dehydration with anhydrous ethanol have a compressive modulus of only 147 kPa (Journal of Colloid and Interface Science 2023, 631, 46-55). Existing methods for treating chemically cross-linked hydrogels of silk fibroin with 75% ethanol aqueous solution have a compressive modulus of only 1.1 MPa (Journal of the Mechanical Behavior of Biomedical Materials, 2023, 147: 106133). Existing methods for treating chemically cross-linked hydrogels of silk fibroin with pure ethanol (100% volume concentration) have a compressive modulus of only 2.33 MPa (Bioactive Materials 2024, 40, 541-556).

[0034] Beneficial effects:

[0035] (1) By regulating the crosslinking density of the silk fibroin-nanofiber composite hydrogel and combining gradient ethanol treatment and vacuum drying post-treatment technology, the present invention achieves the regular and uniform arrangement of the β-sheet crystal structure of silk fibroin and the partial orientation structure of nanofibers, thereby significantly improving the strength and toughness of the material and solving the problem that silk fibroin-based materials in the prior art are difficult to have both high strength and high toughness at the same time.

[0036] (2) The preparation method of the present invention is simple and does not require harsh conditions such as high temperature and high pressure, which is conducive to large-scale production and has broad application prospects in the field of biomedical materials such as orthopedics. Attached Figure Description

[0037] Figure 1 The fluorescence spectra of silk fibroin hydrogels at Ru-1.6, Ru-1.2, Ru-0.8, and Ru-0.4 are shown. Figure 2 The fluorescence intensity histograms of silk fibroin hydrogels Ru-1.6, Ru-1.2, Ru-0.8, and Ru-0.4 (corresponding wavelengths of 410 nm) are shown.

[0038] Figure 3 In the figures, a and b are physical images of the final products of the experimental group and the control group in Example 3, respectively. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0040] To ensure that the performance of the substances used in each embodiment and comparative example is fully disclosed, the manufacturer information of the substances is specified in this invention; in addition, products from other manufacturers that conform to the limitations of this invention are also applicable.

[0041] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0042] Compression modulus: Static compression test was performed on the sample using an INSTRON / 5969 electronic universal testing machine. The specific test method was as follows: the upper and lower clamps were adjusted so that the clamps were just in contact with the sample, and then the sample was compressed at a compression rate of 2 mm / min until the sample ruptured. The stress-strain data of the sample at different time points were obtained. The linear region with strain of 0~5% in the stress-strain curve was selected for fitting, and the compression modulus of the sample was calculated.

[0043] Bending fracture strain: The sample was subjected to static bending test using an INSTRON / 5969 electronic universal testing machine. The specific test method was as follows: the upper and lower clamps were adjusted so that the clamps were just in contact with the test material, and then the sample was bent at a test rate of 2 mm / min until it broke. The stress-strain data of the sample at different time points were obtained. The strain rate value of the strain point corresponding to the material rupture in the stress-strain curve was selected as the bending fracture strain.

[0044] In the following embodiments, the preparation process of the oxidizing bacterial cellulose nanofiber dispersion is as follows: TEMPO (2,2,6,6-tetramethylpiperidine-1-oxy radical) and NaBr are dissolved in deionized water using a water bath ultrasonic method to obtain mixed solution A. Mixed solution A is added to bacterial cellulose (BC) dispersion (manufacturer: Nanjing Tianlu Nanotechnology Co., Ltd., model TL-008, solid content: 0.8%) and stirred evenly. Subsequently, the pH value of the system is adjusted to 10 using NaOH aqueous solution (mass fraction: 2%), and then NaCl is added to the system. Add HCl aqueous solution (3.6% by mass) dropwise to adjust the pH of the system to 10.5, and then continue to add HCl aqueous solution dropwise to adjust the pH of the system to 7 to terminate the reaction, obtaining mixed solution B. Finally, perform multiple centrifugation-washing operations on mixed solution B to obtain an oxidized bacterial cellulose nanofiber (OBC) dispersion with a solid content of 1%; wherein, the mass ratio of TEMPO to bacterial cellulose is 1:3000, the mass ratio of NaBr to bacterial cellulose is 1:500, and the mass ratio of NaClO to bacterial cellulose is 1:13.

[0045] Example 1

[0046] A method for preparing a high-strength, high-toughness silk fibroin-based material, the specific steps of which are as follows:

[0047] (1) Preparation of main materials;

[0048] Raw silk: produced in Ankang City, Shaanxi Province;

[0049] Sodium carbonate solution: solvent is deionized water, mass fraction is 0.5%;

[0050] Deionized water;

[0051] Lithium bromide solution: The solvent is deionized water, with a mass fraction of 44.7%;

[0052] Ru solution: The solvent is deionized water;

[0053] Sodium persulfate solution: solvent is deionized water;

[0054] Oxidizing bacterial cellulose nanofiber dispersion;

[0055] (2) Preparation of silk fibroin solution;

[0056] Raw silk was boiled in a sodium carbonate solution for 40 minutes and then removed to obtain degummed silk. The degummed silk was repeatedly rinsed with deionized water until neutral and drained. Then, it was added to a lithium bromide solution and stirred at 60°C for 60 minutes to completely dissolve the degummed silk to obtain solution A. Solution A was then filtered to obtain solution B. Solution B was then transferred to a dialysis bag with a molecular weight cutoff of 14,000. The dialysis bag was placed in deionized water at a mass ratio of 100:1 to solution B and dialyzed for 96 hours (with the deionized water being changed every 12 hours) to obtain a silk fibroin solution.

[0057] (3) Prepare silk fibroin precursor solution;

[0058] The silk fibroin solution, Ru solution and sodium persulfate solution were mixed evenly to obtain the silk fibroin precursor solution;

[0059] In the silk fibroin precursor solution, the mass fraction of silk fibroin was 13%, the mass fraction of Ru was 0.075%, and the mass fraction of sodium persulfate was 0.2%.

[0060] (4) Preparation of high-strength and high-toughness silk fibroin-based materials;

[0061] After adding and uniformly dispersing an oxidizing bacterial cellulose nanofiber dispersion to a silk fibroin precursor solution, the mixture was subjected to light intensity of 20 mW / cm at 25°C. 2 After irradiating with visible light for 15 minutes, a silk fibroin-nanofiber composite hydrogel was obtained. The silk fibroin-nanofiber composite hydrogel was then subjected to gradient ethanol treatment and vacuum drying to obtain a high-strength and high-toughness silk fibroin-based material.

[0062] In the mixed system of silk fibroin precursor solution and oxidizing bacterial cellulose nanofiber dispersion, the oxidizing bacterial cellulose nanofiber accounts for 0.3% of the total solid mass.

[0063] The gradient ethanol treatment consisted of five stages. In the first stage, the volume concentration of the ethanol-water solution was 10%, the treatment time was 1 hour, and the treatment temperature was 25°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:10. In the second stage, the volume concentration of the ethanol-water solution was 30%, the treatment time was 1 hour, and the treatment temperature was 25°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:10. In the third stage, the volume concentration of the ethanol-water solution was 50%, the treatment time was 1 hour, and the treatment temperature was 25°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:10. In the fourth stage, the volume concentration of the ethanol-water solution was 70%, the treatment time was 1 hour, and the treatment temperature was 25°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:10. In the fifth stage, ethanol was used directly for 1 hour at 25°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:10.

[0064] The vacuum drying post-treatment temperature was 25℃, the air pressure was 1kPa, and the time was 8h.

[0065] The final high-strength and high-toughness silk fibroin-based material has a compressive modulus of 0.92 GPa and a bending fracture strain of 82%.

[0066] Example 2

[0067] A method for preparing a high-strength, high-toughness silk fibroin-based material, the specific steps of which are as follows:

[0068] (1) Preparation of main materials;

[0069] Raw silk: produced in Ankang City, Shaanxi Province;

[0070] Sodium carbonate solution: solvent is deionized water, mass fraction is 0.5%;

[0071] Deionized water;

[0072] Lithium bromide solution: The solvent is deionized water, with a mass fraction of 44.7%;

[0073] Ru solution: The solvent is deionized water;

[0074] Sodium persulfate solution: solvent is deionized water;

[0075] Oxidizing bacterial cellulose nanofiber dispersion;

[0076] (2) Preparation of silk fibroin solution;

[0077] Raw silk was boiled in a sodium carbonate solution for 40 minutes and then removed to obtain degummed silk. The degummed silk was repeatedly rinsed with deionized water until neutral and drained. Then, it was added to a lithium bromide solution and stirred at 60°C for 60 minutes to completely dissolve the degummed silk to obtain solution A. Solution A was then filtered to obtain solution B. Solution B was then transferred to a dialysis bag with a molecular weight cutoff of 14,000. The dialysis bag was placed in deionized water at a mass ratio of 100:1 to solution B and dialyzed for 96 hours (with the deionized water being changed every 12 hours) to obtain a silk fibroin solution.

[0078] (3) Prepare silk fibroin precursor solution;

[0079] The silk fibroin solution, Ru solution and sodium persulfate solution were mixed evenly to obtain the silk fibroin precursor solution;

[0080] In the silk fibroin precursor solution, the mass fraction of silk fibroin was 17%, the mass fraction of Ru was 0.15%, and the mass fraction of sodium persulfate was 0.4%.

[0081] (4) Preparation of high-strength and high-toughness silk fibroin-based materials;

[0082] After adding and uniformly dispersing an oxidizing bacterial cellulose nanofiber dispersion to a silk fibroin precursor solution, the mixture was subjected to light intensity of 50 mW / cm at 37°C. 2 After irradiating with visible light for 60 minutes, a silk fibroin-nanofiber composite hydrogel was obtained. The silk fibroin-nanofiber composite hydrogel was then subjected to gradient ethanol treatment and vacuum drying to obtain a high-strength and high-toughness silk fibroin-based material.

[0083] In the mixed system of silk fibroin precursor solution and oxidizing bacterial cellulose nanofiber dispersion, the oxidizing bacterial cellulose nanofiber accounts for 1.5% of the total solid mass.

[0084] The gradient ethanol treatment consisted of five stages. In the first stage, the volume concentration of the ethanol-water solution was 30%, the treatment time was 2 hours, and the temperature was 37°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:50. In the second stage, the volume concentration of the ethanol-water solution was 50%, the treatment time was 2 hours, and the temperature was 37°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:50. In the third stage, the volume concentration of the ethanol-water solution was 70%, the treatment time was 2 hours, and the temperature was 37°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:50. In the fourth stage, the volume concentration of the ethanol-water solution was 90%, the treatment time was 2 hours, and the temperature was 37°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:50. In the fifth stage, ethanol was used directly for 2 hours at 37°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:50.

[0085] The vacuum drying post-treatment temperature was 25℃, the air pressure was 1kPa, and the time was 24h.

[0086] The final high-strength and high-toughness silk fibroin-based material has a compressive modulus of 1.05 GPa and a bending fracture strain of 85%.

[0087] Example 3

[0088] A method for preparing a high-strength, high-toughness silk fibroin-based material, the specific steps of which are as follows:

[0089] (1) Preparation of main materials;

[0090] Raw silk: produced in Ankang City, Shaanxi Province;

[0091] Sodium carbonate solution: solvent is deionized water, mass fraction is 0.5%;

[0092] Deionized water;

[0093] Lithium bromide solution: The solvent is deionized water, with a mass fraction of 44.7%;

[0094] Ru solution: The solvent is deionized water;

[0095] Sodium persulfate solution: solvent is deionized water;

[0096] Oxidizing bacterial cellulose nanofiber dispersion;

[0097] (2) Preparation of silk fibroin solution;

[0098] Raw silk was boiled in a sodium carbonate solution for 40 minutes and then removed to obtain degummed silk. The degummed silk was repeatedly rinsed with deionized water until neutral and drained. Then, it was added to a lithium bromide solution and stirred at 60°C for 60 minutes to completely dissolve the degummed silk to obtain solution A. Solution A was then filtered to obtain solution B. Solution B was then transferred to a dialysis bag with a molecular weight cutoff of 14,000. The dialysis bag was placed in deionized water at a mass ratio of 100:1 to solution B and dialyzed for 96 hours (with the deionized water being changed every 12 hours) to obtain a silk fibroin solution.

[0099] (3) Prepare silk fibroin precursor solution;

[0100] The silk fibroin solution, Ru solution and sodium persulfate solution were mixed evenly to obtain the silk fibroin precursor solution;

[0101] In the silk fibroin precursor solution, the mass fraction of silk fibroin was 15%, the mass fraction of Ru was 0.113%, and the mass fraction of sodium persulfate was 0.3%.

[0102] (4) Preparation of high-strength and high-toughness silk fibroin-based materials;

[0103] After adding and uniformly dispersing an oxidizing bacterial cellulose nanofiber dispersion to a silk fibroin precursor solution, the mixture was subjected to light intensity of 35 mW / cm at 31°C. 2 After irradiating with visible light for 30 minutes, a silk fibroin-nanofiber composite hydrogel was obtained. The silk fibroin-nanofiber composite hydrogel was then subjected to gradient ethanol treatment and vacuum drying to obtain a high-strength and high-toughness silk fibroin-based material.

[0104] In the mixed system of silk fibroin precursor solution and oxidizing bacterial cellulose nanofiber dispersion, the oxidizing bacterial cellulose nanofiber accounts for 1% of the total solid mass fraction.

[0105] The gradient ethanol treatment consisted of five stages. In the first stage, the volume concentration of the ethanol-water solution was 20%, the treatment time was 1.5 h, and the treatment temperature was 31 °C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:30. In the second stage, the volume concentration of the ethanol-water solution was 40%, the treatment time was 1.5 h, and the treatment temperature was 31 °C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:30. In the third stage, the volume concentration of the ethanol-water solution was 60%, the treatment time was 1.5 h, and the treatment temperature was 31 °C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:30. In the fourth stage, the volume concentration of the ethanol-water solution was 80%, the treatment time was 1.5 h, and the treatment temperature was 31 °C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:30. In the fifth stage, ethanol was used directly, the treatment time was 1.5 h, the treatment temperature was 31 °C, and the volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:30.

[0106] The vacuum drying post-treatment temperature was 25℃, the air pressure was 1kPa, and the time was 16h.

[0107] The final high-strength and high-toughness silk fibroin-based material has a compressive modulus of 1.25 GPa and a bending fracture strain of 93%.

[0108] To demonstrate that gradient ethanol treatment and vacuum drying after forming a hydrogel with moderate cross-linking density can improve the regularity of the structure, the following experiments were also conducted in this embodiment:

[0109] Experimental group: Basically the same as this example, except that: no oxidizing bacterial cellulose nanofiber dispersion was added, and the prepared product was not silk fibroin-nanofiber composite hydrogel, but silk fibroin hydrogel;

[0110] Control group: Basically the same as the experimental group, the only difference is that the gradient ethanol treatment was changed to single ethanol treatment (i.e., non-gradient concentration, ethanol was used directly throughout the process), and the vacuum drying post-treatment was changed to natural air drying post-treatment.

[0111] The final products of the experimental group and the control group are as follows Figure 3 As shown, from Figure 3 As can be seen from image a, the final product of the experimental group has high transparency, and the letter "SF" can be clearly seen below; from Figure 3As shown in Figure b, the final product of the control group had low transparency, and the text below was blurry. This indicates that the gradient ethanol treatment combined with vacuum drying effectively improves the transparency of the material. This is because this treatment induces silk fibroin to form a regular and uniform β-sheet crystalline structure, which improves the transparency of the material. In contrast, the control group only used a single high-concentration alcohol treatment combined with natural air drying, which is not conducive to the formation of a regular and uniform β-sheet crystalline structure, resulting in poor transparency. Furthermore, the tests showed that the compressive modulus of the final product in the experimental group was 0.3 GPa, while the compressive modulus of the final product in the control group was 0.03 GPa, further confirming the significant effect of gradient ethanol treatment and vacuum drying on improving the regularity of the β-sheet structure.

[0112] Example 4

[0113] A method for preparing a high-strength, high-toughness silk fibroin-based material, the specific steps of which are as follows:

[0114] (1) Preparation of main materials;

[0115] Raw silk: produced in Ankang City, Shaanxi Province;

[0116] Sodium carbonate solution: solvent is deionized water, mass fraction is 0.5%;

[0117] Deionized water;

[0118] Lithium bromide solution: The solvent is deionized water, with a mass fraction of 44.7%;

[0119] Riboflavin;

[0120] Sodium persulfate solution: solvent is deionized water;

[0121] Oxidizing bacterial cellulose nanofiber dispersion;

[0122] (2) Preparation of silk fibroin solution;

[0123] Raw silk was boiled in a sodium carbonate solution for 40 minutes and then removed to obtain degummed silk. The degummed silk was repeatedly rinsed with deionized water until neutral and drained. Then, it was added to a lithium bromide solution and stirred at 60°C for 60 minutes to completely dissolve the degummed silk to obtain solution A. Solution A was then filtered to obtain solution B. Solution B was then transferred to a dialysis bag with a molecular weight cutoff of 14,000. The dialysis bag was placed in deionized water at a mass ratio of 100:1 to solution B and dialyzed for 96 hours (with the deionized water being changed every 12 hours) to obtain a silk fibroin solution.

[0124] (3) Prepare silk fibroin precursor solution;

[0125] The silk fibroin solution, riboflavin and sodium persulfate solution were mixed evenly to obtain the silk fibroin precursor solution.

[0126] In the silk fibroin precursor solution, the mass fraction of silk fibroin was 13%, the mass fraction of riboflavin was 0.056%, and the mass fraction of sodium persulfate was 0.2%.

[0127] (4) Preparation of high-strength and high-toughness silk fibroin-based materials;

[0128] After adding and uniformly dispersing an oxidizing bacterial cellulose nanofiber dispersion to a silk fibroin precursor solution, the mixture was subjected to light intensity of 20 mW / cm at 25°C. 2 After irradiating with visible light for 15 minutes, a silk fibroin-nanofiber composite hydrogel was obtained. The silk fibroin-nanofiber composite hydrogel was then subjected to gradient ethanol treatment and vacuum drying to obtain a high-strength and high-toughness silk fibroin-based material.

[0129] In the mixed system of silk fibroin precursor solution and oxidizing bacterial cellulose nanofiber dispersion, the oxidizing bacterial cellulose nanofiber accounts for 0.3% of the total solid mass.

[0130] The gradient ethanol treatment consisted of five stages. In the first stage, the volume concentration of the ethanol-water solution was 10%, the treatment time was 1 hour, and the treatment temperature was 25°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:10. In the second stage, the volume concentration of the ethanol-water solution was 30%, the treatment time was 1 hour, and the treatment temperature was 25°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:10. In the third stage, the volume concentration of the ethanol-water solution was 50%, the treatment time was 1 hour, and the treatment temperature was 25°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:10. In the fourth stage, the volume concentration of the ethanol-water solution was 70%, the treatment time was 1 hour, and the treatment temperature was 25°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:10. In the fifth stage, ethanol was used directly for 1 hour at 25°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:10.

[0131] The vacuum drying post-treatment temperature was 25℃, the air pressure was 1kPa, and the time was 8h.

[0132] The final high-strength and high-toughness silk fibroin-based material has a compressive modulus of 0.82 GPa and a bending fracture strain of 81%.

[0133] Example 5

[0134] A method for preparing a high-strength, high-toughness silk fibroin-based material, the specific steps of which are as follows:

[0135] (1) Preparation of main materials;

[0136] Raw silk: produced in Ankang City, Shaanxi Province;

[0137] Sodium carbonate solution: solvent is deionized water, mass fraction is 0.5%;

[0138] Deionized water;

[0139] Lithium bromide solution: The solvent is deionized water, with a mass fraction of 44.7%;

[0140] Riboflavin;

[0141] Sodium persulfate solution: solvent is deionized water;

[0142] Oxidizing bacterial cellulose nanofiber dispersion;

[0143] (2) Preparation of silk fibroin solution;

[0144] Raw silk was boiled in a sodium carbonate solution for 40 minutes and then removed to obtain degummed silk. The degummed silk was repeatedly rinsed with deionized water until neutral and drained. Then, it was added to a lithium bromide solution and stirred at 60°C for 60 minutes to completely dissolve the degummed silk to obtain solution A. Solution A was then filtered to obtain solution B. Solution B was then transferred to a dialysis bag with a molecular weight cutoff of 14,000. The dialysis bag was placed in deionized water at a mass ratio of 100:1 to solution B and dialyzed for 96 hours (with the deionized water being changed every 12 hours) to obtain a silk fibroin solution.

[0145] (3) Prepare silk fibroin precursor solution;

[0146] The silk fibroin solution, riboflavin and sodium persulfate solution were mixed evenly to obtain the silk fibroin precursor solution.

[0147] In the silk fibroin precursor solution, the mass fraction of silk fibroin was 17%, the mass fraction of riboflavin was 0.086%, and the mass fraction of sodium persulfate was 0.4%.

[0148] (4) Preparation of high-strength and high-toughness silk fibroin-based materials;

[0149] After adding and uniformly dispersing an oxidizing bacterial cellulose nanofiber dispersion to a silk fibroin precursor solution, the mixture was subjected to light intensity of 50 mW / cm at 37°C. 2 After irradiating with visible light for 60 minutes, a silk fibroin-nanofiber composite hydrogel was obtained. The silk fibroin-nanofiber composite hydrogel was then subjected to gradient ethanol treatment and vacuum drying to obtain a high-strength and high-toughness silk fibroin-based material.

[0150] In the mixed system of silk fibroin precursor solution and oxidizing bacterial cellulose nanofiber dispersion, the oxidizing bacterial cellulose nanofiber accounts for 1.5% of the total solid mass.

[0151] The gradient ethanol treatment consisted of five stages. In the first stage, the volume concentration of the ethanol-water solution was 30%, the treatment time was 2 hours, and the temperature was 37°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:50. In the second stage, the volume concentration of the ethanol-water solution was 50%, the treatment time was 2 hours, and the temperature was 37°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:50. In the third stage, the volume concentration of the ethanol-water solution was 70%, the treatment time was 2 hours, and the temperature was 37°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:50. In the fourth stage, the volume concentration of the ethanol-water solution was 90%, the treatment time was 2 hours, and the temperature was 37°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:50. In the fifth stage, ethanol was used directly for 2 hours at 37°C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:50.

[0152] The vacuum drying post-treatment temperature was 25℃, the air pressure was 1kPa, and the time was 24h.

[0153] The final high-strength and high-toughness silk fibroin-based material has a compressive modulus of 0.93 GPa and a bending fracture strain of 85%.

[0154] Example 6

[0155] A method for preparing a high-strength, high-toughness silk fibroin-based material, the specific steps of which are as follows:

[0156] (1) Preparation of main materials;

[0157] Raw silk: produced in Ankang City, Shaanxi Province;

[0158] Sodium carbonate solution: solvent is deionized water, mass fraction is 0.5%;

[0159] Deionized water;

[0160] Lithium bromide solution: The solvent is deionized water, with a mass fraction of 44.7%;

[0161] Riboflavin;

[0162] Sodium persulfate solution: solvent is deionized water;

[0163] Oxidizing bacterial cellulose nanofiber dispersion;

[0164] (2) Preparation of silk fibroin solution;

[0165] Raw silk was boiled in a sodium carbonate solution for 40 minutes and then removed to obtain degummed silk. The degummed silk was repeatedly rinsed with deionized water until neutral and drained. Then, it was added to a lithium bromide solution and stirred at 60°C for 60 minutes to completely dissolve the degummed silk to obtain solution A. Solution A was then filtered to obtain solution B. Solution B was then transferred to a dialysis bag with a molecular weight cutoff of 14,000. The dialysis bag was placed in deionized water at a mass ratio of 100:1 to solution B and dialyzed for 96 hours (with the deionized water being changed every 12 hours) to obtain a silk fibroin solution.

[0166] (3) Prepare silk fibroin precursor solution;

[0167] The silk fibroin solution, riboflavin and sodium persulfate solution were mixed evenly to obtain the silk fibroin precursor solution.

[0168] In the silk fibroin precursor solution, the mass fraction of silk fibroin was 15%, the mass fraction of riboflavin was 0.071%, and the mass fraction of sodium persulfate was 0.3%.

[0169] (4) Preparation of high-strength and high-toughness silk fibroin-based materials;

[0170] After adding and uniformly dispersing an oxidizing bacterial cellulose nanofiber dispersion to a silk fibroin precursor solution, the mixture was subjected to light intensity of 35 mW / cm at 31°C. 2 After irradiating with visible light for 30 minutes, a silk fibroin-nanofiber composite hydrogel was obtained. The silk fibroin-nanofiber composite hydrogel was then subjected to gradient ethanol treatment and vacuum drying to obtain a high-strength and high-toughness silk fibroin-based material.

[0171] In the mixed system of silk fibroin precursor solution and oxidizing bacterial cellulose nanofiber dispersion, the oxidizing bacterial cellulose nanofiber accounts for 1% of the total solid mass fraction.

[0172] The gradient ethanol treatment consisted of five stages. In the first stage, the volume concentration of the ethanol-water solution was 20%, the treatment time was 1.5 h, and the treatment temperature was 31 °C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:30. In the second stage, the volume concentration of the ethanol-water solution was 40%, the treatment time was 1.5 h, and the treatment temperature was 31 °C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:30. In the third stage, the volume concentration of the ethanol-water solution was 60%, the treatment time was 1.5 h, and the treatment temperature was 31 °C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:30. In the fourth stage, the volume concentration of the ethanol-water solution was 80%, the treatment time was 1.5 h, and the treatment temperature was 31 °C, with a volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:30. In the fifth stage, ethanol was used directly, the treatment time was 1.5 h, the treatment temperature was 31 °C, and the volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol-water solution of 1:30.

[0173] The vacuum drying post-treatment temperature was 25℃, the air pressure was 1kPa, and the time was 16h.

[0174] The final high-strength and high-toughness silk fibroin-based material has a compressive modulus of 1.02 GPa and a bending fracture strain of 90%.

[0175] The high-strength and high-toughness silk fibroin-based materials prepared in Examples 1-6 of this invention have excellent biocompatibility and biodegradability, and their strength and toughness are significantly improved, showing broad application prospects in the field of biomedical materials.

[0176] This invention also investigated the effects of different concentrations of Ru and sodium persulfate on the crosslinking density of silk fibroin hydrogels through experiments. The specific experimental procedure is as follows:

[0177] (1) Preparation of materials;

[0178] Raw silk: produced in Ankang City, Shaanxi Province;

[0179] Sodium carbonate solution: solvent is deionized water, mass fraction is 0.5%;

[0180] Deionized water;

[0181] Lithium bromide solution: The solvent is deionized water, with a mass fraction of 44.7%;

[0182] Ru solution: The solvent is deionized water;

[0183] Sodium persulfate solution: solvent is deionized water;

[0184] (2) Preparation of silk fibroin solution;

[0185] Raw silk was boiled in a sodium carbonate solution for 40 minutes and then removed to obtain degummed silk. The degummed silk was repeatedly rinsed with deionized water until neutral and drained. Then, it was added to a lithium bromide solution and stirred at 60°C for 60 minutes to completely dissolve the degummed silk to obtain solution A. Solution A was then filtered to obtain solution B. Solution B was then transferred to a dialysis bag with a molecular weight cutoff of 14,000. The dialysis bag was placed in deionized water at a mass ratio of 100:1 to solution B and dialyzed for 96 hours (with the deionized water being changed every 12 hours) to obtain a silk fibroin solution.

[0186] (3) Prepare 1-4 silk fibroin precursor solutions;

[0187] The silk fibroin solution, Ru solution and sodium persulfate solution were mixed evenly to obtain silk fibroin precursor solution 1-4.

[0188] In silk fibroin precursor solutions 1-4, the mass fraction of silk fibroin was 15%.

[0189] In silk fibroin precursor solution 1, the mass fraction of sodium persulfate was 0.4%, and the mass fraction of Ru was 0.150%.

[0190] In silk fibroin precursor solution 2, the mass fraction of sodium persulfate was 0.3%, and the mass fraction of Ru was 0.112%.

[0191] In silk fibroin precursor solution 3, the mass fraction of sodium persulfate was 0.2%, and the mass fraction of Ru was 0.075%.

[0192] In silk fibroin precursor solution 4, the mass fraction of sodium persulfate was 0.1%, and the mass fraction of Ru was 0.037%.

[0193] (4) Preparation of silk fibroin hydrogels in Ru-1.6, Ru-1.2, Ru-0.8, and Ru-0.4;

[0194] At 31℃, silk fibroin precursor solutions 1-4 were subjected to light intensity of 35mW / cm. 2 After irradiating with visible light for 45 minutes, silk fibroin hydrogels 1-4 were obtained;

[0195] Ru-1.6 corresponds to silk fibroin precursor solution 1, Ru-1.2 corresponds to silk fibroin precursor solution 2, Ru-0.8 corresponds to silk fibroin precursor solution 3, and Ru-0.4 corresponds to silk fibroin precursor solution 4.

[0196] (5) Testing;

[0197] Fluorescence spectra of Ru-1.6, Ru-1.2, Ru-0.8, and Ru-0.4 were measured using a fluorescence spectrometer, and the fluorescence intensity was recorded. The test results are as follows: Figure 1 As shown, from Figure 1 As can be seen, with the increase of the mass fraction of Ru and sodium persulfate in the silk fibroin precursor solution, the peak values ​​of the corresponding characteristic peaks in the fluorescence spectrum gradually increase, and the peak value of the characteristic peak at 410 nm is directly proportional to the relative chemical crosslinking point content of the silk fibroin hydrogel; from Figure 2 As can be seen from the fluorescence spectrum, the relative fluorescence intensity at 410 nm also shows a gradually increasing trend. Figure 2 The spectral data show that the crosslinking point content of different hydrogels, from high to low, is Ru-1.6, Ru-1.2, Ru-0.8, and Ru-0.4. This indicates that as the mass fraction of Ru and sodium persulfate increases, the chemical crosslinking point content and crosslinking density in the silk fibroin hydrogel gradually increase, suggesting that the crosslinking density of silk fibroin can be controlled by the mass fraction of Ru and sodium persulfate.

[0198] Comparative Example 1

[0199] A method for preparing a silk fibroin-based material differs from Example 1 only in that the amounts of Ru solution and sodium persulfate solution added are adjusted when preparing the silk fibroin precursor solution; the mass fraction of Ru in the silk fibroin precursor solution is 0.037%, and the mass fraction of sodium persulfate is 0.1%.

[0200] The final silk fibroin-based material had a compressive modulus of 0.45 GPa and a bending fracture strain of 58%.

[0201] Compared with Comparative Example 1 and Example 1, the compressive modulus and flexural fracture strain of the silk fibroin-based material were significantly reduced. This is because the mass fractions of Ru and sodium persulfate in the silk fibroin precursor solution were too low, which was not conducive to the initial material (silk fibroin hydrogel) molding support, i.e., it could not form a silk fibroin chemical cross-linking network with sufficient support capacity; at the same time, it was not conducive to the regular and uniform arrangement of the β-sheet structure formed in the subsequent gradient ethanol treatment and vacuum drying post-treatment process.

[0202] Comparative Example 2

[0203] The method for preparing a silk fibroin-based material differs from Example 2 only in that the amount of Ru solution and sodium persulfate solution added is adjusted when preparing the silk fibroin precursor solution; the mass fraction of Ru in the silk fibroin precursor solution is 0.2%, and the mass fraction of sodium persulfate is 0.5%.

[0204] The final silk fibroin-based material had a compressive modulus of 0.65 GPa and a bending fracture strain of 65%.

[0205] Compared with Comparative Example 2 and Example 2, the compressive modulus and flexural fracture strain of the silk fibroin-based material were significantly reduced. This is because the mass fractions of Ru and sodium persulfate in the silk fibroin precursor solution were too high, which restricted the movement of the hydrophobic segments in the formed "high cross-linking density" hydrogel. This was not conducive to the formation of β-sheet crystalline structures and the regular and uniform arrangement of β-sheet crystalline structures in the subsequent gradient ethanol treatment and vacuum drying process.

[0206] Comparative Example 3

[0207] The method for preparing a silk fibroin-based material differs from Example 4 only in that the amount of riboflavin and sodium persulfate solution added is adjusted when preparing the silk fibroin precursor solution; the mass fraction of riboflavin in the silk fibroin precursor solution is 0.041%, and the mass fraction of sodium persulfate is 0.1%.

[0208] The final silk fibroin-based material had a compressive modulus of 0.42 GPa and a bending fracture strain of 55%.

[0209] Compared with Comparative Example 3 and Example 4, the compressive modulus and flexural fracture strain of the silk fibroin-based material were significantly reduced. This is because the mass fractions of riboflavin and sodium persulfate in the silk fibroin precursor solution were too low, which was not conducive to the initial material (silk fibroin hydrogel) molding support, i.e., it could not form a silk fibroin chemical cross-linking network with sufficient support capacity; at the same time, it was not conducive to the regular and uniform arrangement of the β-sheet structure formed in the subsequent gradient ethanol treatment and vacuum drying post-treatment process.

[0210] Comparative Example 4

[0211] The method for preparing a silk fibroin-based material differs from Example 5 only in that the amount of riboflavin and sodium persulfate solution added is adjusted when preparing the silk fibroin precursor solution; the mass fraction of riboflavin in the silk fibroin precursor solution is 0.101%, and the mass fraction of sodium persulfate is 0.5%.

[0212] The final silk fibroin-based material had a compressive modulus of 0.60 GPa and a bending fracture strain of 60%.

[0213] Compared with Comparative Example 4 and Example 5, the compressive modulus and flexural fracture strain of the silk fibroin-based material were significantly reduced. This is because the mass fraction of riboflavin and sodium persulfate in the silk fibroin precursor solution was too high, which restricted the movement of hydrophobic segments in the formed "high cross-linking density" hydrogel. This was not conducive to the formation of β-sheet crystalline structures and the regular and uniform arrangement of β-sheet crystalline structures in the subsequent gradient ethanol treatment and vacuum drying process.

Claims

1. A method for preparing a high-strength, high-toughness silk fibroin-based material, characterized in that: After adding nanofiber dispersion to the silk fibroin precursor solution and dispersing it evenly, the silk fibroin-nanofiber composite hydrogel was obtained by visible light-induced chemical cross-linking at 25~37℃. The silk fibroin-nanofiber composite hydrogel was then subjected to gradient ethanol treatment and vacuum drying to obtain a high-strength and high-toughness silk fibroin-based material. The silk fibroin precursor solution was obtained by mixing a silk fibroin solution, a tris(2,2'-bipyridine)ruthenium(II) trichlorohydrate solution, and a sodium persulfate solution. In the silk fibroin precursor solution, the mass fraction of silk fibroin was 13-17%, the mass fraction of tris(2,2'-bipyridine)ruthenium(II) trichlorohydrate was 0.075-0.15%, and the mass fraction of sodium persulfate was 0.2-0.4%. Alternatively, the silk fibroin precursor solution is obtained by mixing silk fibroin solution, riboflavin and sodium persulfate solution; In the silk fibroin precursor solution, the mass fraction of silk fibroin is 13-17%, the mass fraction of riboflavin is 0.056-0.086%, and the mass fraction of sodium persulfate is 0.2-0.4%. Nanofibers are oxidizing bacterial cellulose nanofibers, silk fibroin nanofibers, or collagen nanofibers.

2. The method for preparing a high-strength, high-toughness silk fibroin-based material according to claim 1, characterized in that, Visible light intensity is 20~50mW / cm 2 The visible light irradiation time is 15~60min.

3. The method for preparing a high-strength, high-toughness silk fibroin-based material according to claim 1, characterized in that, The solid content of the nanofiber dispersion is 1%. In the mixed system of silk fibroin precursor solution and nanofiber dispersion, the mass fraction of nanofibers in the total solids is 0.3~1.5%.

4. The method for preparing a high-strength, high-toughness silk fibroin-based material according to claim 1, characterized in that, The gradient ethanol treatment consists of five stages, with the volume concentration of the ethanol aqueous solution used in each stage increasing sequentially within the range of 10% to 100%. The treatment time for each stage is 1 to 2 hours, and the treatment temperature is 25 to 37°C.

5. The method for preparing a high-strength, high-toughness silk fibroin-based material according to claim 4, characterized in that, The volume ratio of silk fibroin-nanofiber composite hydrogel to ethanol aqueous solution is 1:10~50.

6. The method for preparing a high-strength, high-toughness silk fibroin-based material according to claim 1, characterized in that, The vacuum drying post-treatment temperature is 25℃, the air pressure is ≤1kPa, and the time is 8~24h.

7. A high-strength, high-toughness silk fibroin-based material, characterized in that: It is prepared by the method of any one of claims 1 to 6 for the preparation of a high-strength and high-toughness silk fibroin-based material; High-strength and high-toughness silk fibroin-based materials have a composite cross-linked network; The composite cross-linked network consists of a chemical cross-linked network formed between silk fibroin molecules and a physical cross-linked network formed by the entanglement of silk fibroin and nanofibers. Silk fibroin has a regular and uniform β-sheet crystalline structure, and nanofibers have a partially oriented structure.

8. The high-strength, high-toughness silk fibroin-based material according to claim 7, characterized in that, The aspect ratio of the nanofibers is 70~110:

1.

9. A high-strength, high-toughness silk fibroin-based material according to claim 8, characterized in that, The high-strength and high-toughness silk fibroin-based material has a compressive modulus ≥0.8GPa and a bending fracture strain ≥80%.

10. The application of a high-strength, high-toughness silk fibroin-based material as described in any one of claims 7 to 9, characterized in that: It is applied in the field of biomedical materials.

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