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

Abstract

The invention belongs to the technical field of biological functional polymer materials, and relates to a high-strength and high-toughness silk fibroin-based material as well as a preparation method and application thereof. The material has a composite cross-linked network; the composite cross-linked network is composed of a chemical cross-linked network formed among silk fibroin molecules and a physical cross-linked network formed by mutual entanglement of silk fibroin and nanofibers, the silk fibroin has a regular and uniform beta-folded crystal structure, and the nanofibers have a partial orientation structure. The preparation method comprises the following steps: adding a nanofiber dispersion liquid into a silk fibroin precursor solution with specific composition and proportion, uniformly dispersing, and carrying out visible light-induced chemical crosslinking at 25-37 DEG C to obtain silk fibroin-nanofiber composite hydrogel; and carrying out gradient ethanol treatment and vacuum drying post-treatment on the silk fibroin-nanofiber composite hydrogel to obtain the silk fibroin-nanofiber composite hydrogel. The material can be applied to the field of biomedical materials such as degradable bone nails and bone lamellas. According to the invention, the high strength and high toughness of the silk fibroin-based material are both realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of biofunctional polymer materials, and relates to a high-strength and high-toughness silk fibroin-based material and a preparation method and application thereof. Background Art

[0002] Silk fibroin (SF), a natural biomass material, has attracted significant attention in the field of biomedical materials due to its excellent biocompatibility, tunable biodegradability, ease of processing, and wide availability. It particularly demonstrates great potential in hard tissue repair applications, such as orthopedic implants. Silk fibroin, obtained by degumming natural silkworm cocoons, can be fabricated through various processing techniques into various forms of silk fibroin-based materials, including films, hydrogels, and porous scaffolds. Its degradation products are non-toxic amino acids and peptides, eliminating the stress shielding and secondary surgical removal issues 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 fibroin fibers depend on their specific intermolecular interactions and secondary structures, while the molecular structure of silk fibroin is destroyed and the molecular weight is reduced during the regeneration process, and conventional preparation processes are difficult to controllably reproduce the regular crystalline structure and amorphous structure distribution of natural fibers, resulting in the existing silk fibroin-based materials being difficult to simultaneously have 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 prepare silk fibroin-based materials by inducing chemical cross-linked hydrogel recrystallization through alcohol treatment, and their compression modulus is usually only 1~330MPa, and the toughness is insufficient.

[0005] The documents (Nature Materials, 2020, 19(1): 102-108; Advanced Materials, 2024, 36(23): 2308748) prepare high-strength silk fibroin-based materials by a molding forming strategy combining high temperature with ultrahigh pressure, although the compression modulus can reach 3.8-7.8 GPa, the bending fracture strain (one of the important indicators reflecting the toughness of the material, under the same material type and test conditions, the higher the value, generally indicating that the material can withstand greater deformation before breaking, the better the toughness; the lower the value, the stronger the brittleness of the material, the worse the toughness) is only 1.4-2.5%. At the same time, the high-strength silk fibroin-based material needs to rely on harsh processing conditions such as high temperature (145℃) and ultrahigh pressure (632MPa), resulting in high production cost and complex process, which is not conducive to large-scale production.

[0006] In view of the above problems, there is an urgent need for a new method to realize the preparation of high-strength and high-toughness silk fibroin-based materials. SUMMARY

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

[0008] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] A preparation method of a high-strength and high-toughness silk fibroin-based material, wherein a nanofiber dispersion solution is added to a silk fibroin precursor solution and uniformly dispersed, and then a silk fibroin-nanofiber composite hydrogel is obtained by chemical cross-linking under visible light at 25-37℃, and the high-strength and high-toughness silk fibroin-based material is prepared by gradient ethanol treatment and vacuum drying after processing the silk fibroin-nanofiber composite hydrogel;

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

[0011] Alternatively, the silk fibroin precursor solution is obtained by mixing a silk fibroin solution, a riboflavin and a 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, chemical cross-linking is initiated by visible light (either Ru / SPS or riboflavin / SPS system) to form a chemical cross-linking network between silk fibroin molecules, and the silk fibroin cross-linking network and nanofibers form an intertangled structure through close physical entanglement; then, after gradient ethanol treatment and vacuum drying post-processing, the silk fibroin forms a beta-sheet crystalline structure, i.e., a physical cross-linking network.

[0013] The key of the present application is to control the chemical cross-linking of the silk fibroin-nanofiber composite hydrogel to a medium cross-linking density hydrogel (moderate cross-linking density), which refers to the number of cross-linking points in a unit volume of hydrogel, which is a concept within the atomic scale range. It cannot be absolutely quantified by existing characterization techniques, but the relative chemical cross-linking point content of different hydrogels can be indirectly reflected by the peak value of the corresponding characteristic peak in the fluorescence spectrum of the hydrogel. The hydrogel formed by using the silk fibroin precursor solution formula of any of the above systems is a medium cross-linking density hydrogel. The peak value of the characteristic peak in the fluorescence spectrum of the hydrogel formed by using the initiator (Ru and SPS, or riboflavin and SPS) in any of the above systems below the limit is lower than that of the medium cross-linking density group, i.e., the formed hydrogel is a "low cross-linking density hydrogel". The peak value of the characteristic peak in the fluorescence spectrum of the hydrogel formed by using the initiator above the limit is higher than that of the medium cross-linking density group, i.e., the formed hydrogel is a "high cross-linking density hydrogel".

[0014] If the gradient ethanol treatment and vacuum drying post-processing are not based on the formation of "medium cross-linking density" hydrogel, but based on "low cross-linking density" or "high cross-linking density" hydrogel, the structure referred to in the present application cannot be formed, and the high strength and high toughness effect cannot be achieved. Specifically, the "low cross-linking density" hydrogel has poor initial forming ability, which is not conducive to the initial material (silk fibroin hydrogel) forming support, i.e., the silk fibroin chemical cross-linking network cannot form a sufficient support capacity. At the same time, it is not conducive to the regular and uniform arrangement of the beta-sheet structure formed in the subsequent gradient ethanol treatment and vacuum drying post-processing process. The "high cross-linking density" hydrogel has a short hydrophobic segment, which is not conducive to the formation of beta-sheet crystalline structure and the regular and uniform arrangement of beta-sheet crystalline structure in the subsequent gradient ethanol treatment and vacuum drying post-processing process.

[0015] As a preferred technical solution:

[0016] The above-mentioned method for preparing a high-strength and high-toughness silk fibroin-based material has a visible light intensity of 20-50 mW / cm 2 , and a visible light irradiation time of 15-60 min.

[0017] The preparation method of the high-strength and high-toughness silk fibroin-based material as described above, the solid content of the nanofiber dispersion liquid is 1%, and the mass fraction of the nanofiber in the mixed system of the silk fibroin precursor solution and the nanofiber dispersion liquid is 0.3-1.5% of the total solid.

[0018] The preparation method of the high-strength and high-toughness silk fibroin-based material as described above, the gradient ethanol treatment is divided into five stages, the volume concentration of the ethanol aqueous solution used in each stage is increased in the range of 10-100% in turn, the treatment time of each stage is 1-2h, and the treatment temperature is 25-37℃.

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

[0020] The preparation method of the high-strength and high-toughness silk fibroin-based material as described above, the temperature of the vacuum drying post-treatment is 25℃, the air pressure is ≤1kPa, and the time is 8-24h.

[0021] The application further provides a high-strength and high-toughness silk fibroin-based material prepared by using the preparation method of the high-strength and high-toughness silk fibroin-based material as described above.

[0022] The high-strength and high-toughness silk fibroin-based material has a composite crosslinking network, the composite crosslinking network is composed of a chemical crosslinking network formed between silk fibroin molecules and a physical crosslinking network formed by mutual entanglement of silk fibroin and nanofibers, the silk fibroin has a regular and uniform beta-sheet crystal structure, and the nanofibers have a partial orientation structure.

[0023] As a preferred technical scheme:

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

[0025] The high-strength and high-toughness silk fibroin-based material as described above, the compression modulus of the high-strength and high-toughness silk fibroin-based material is ≥0.8GPa, and the bending fracture strain is ≥80%.

[0026] The application further provides an application of the high-strength and high-toughness silk fibroin-based material as described above, which is applied to the field of biomedical materials and has a good application prospect in the field of biomedical materials such as orthopedics, including the construction of bone fracture internal fixation nail plate system materials, for example, can be used as bone plates, bone nails and other hard tissue implants. It can be predicted that the multifunctional medical high-strength and high-toughness material can be further developed by combining 3D printing, numerical control machining and other personalized customization, for example, can be used as drug-loaded scaffolds and other bioactive scaffold materials.

[0027] Invention principles:

[0028] The present application innovatively synthesizes a silk fibroin-based functional material with high strength and toughness by further regulating and synergizing the interaction of homogenized crystallization and nanofiber based on the synthesis of SF chemical crosslinking hydrogel with moderate crosslinking density, uniform crosslinking network and no bubble generation. The moderate crosslinking density and uniform chemical crosslinking network are beneficial to the movement of SF hydrophobic segments to form uniformly distributed β-sheet structure, and the combination of gradient ethanol treatment and vacuum drying post-processing technology strategy maximizes the formation of SF hydrogel homogenized crystallization.

[0029] The relevant core principles of the present application are as follows:

[0030] First, a crosslinking reaction system without bubble generation is selected to prepare SF chemical crosslinking hydrogel with appropriate crosslinking density. The generation of bubbles in the crosslinking reaction system (such as the conventional horseradish peroxidase system) will be not conducive to the formation of subsequent homogenized structure and the improvement of mechanical properties. For the uniformity of the crosslinking network of hydrogel, the higher the uniformity of the crosslinking network of hydrogel, the more conducive to improving the regularity of the distribution of subsequent β-sheet crystalline structure, avoiding stress concentration and other problems to reduce the mechanical properties of the material; for the crosslinking density, it is not the higher the crosslinking density, the better the functional material with better mechanical properties. The reason is that too high crosslinking density of hydrogel will not be conducive to the formation of β-sheet crystalline structure and the regular arrangement of crystalline structure in the subsequent processing process, and too low crosslinking density will not be conducive to the initial material forming support and the homogenization shrinkage in the subsequent processing process. These two factors will comprehensively lead to poor improvement of the mechanical strength of the material. The combination of gradient ethanol treatment and vacuum drying post-processing is to maximize the joint protection of the homogenization recrystallization of the material and the homogenization shrinkage of the macrostructure of the material, and the related effect is obviously better than that of single high-concentration ethanol treatment and natural air drying treatment.

[0031] On this basis, nanofibers such as oxidized bacterial cellulose nanofiber (OBC), silk fibroin nanofiber and collagen nanofiber are further uniformly compounded into the SF hydrogel system. The addition of appropriate nanofibers is conducive to the interaction regulation and functional synergy of the homogenized crystallization in the post-processing of the aforementioned SF hydrogel with appropriate crosslinking density, which further significantly improves the strength and toughness of the material. The specific action includes: the formation of related homogenized crystalline structure in the SF hydrogel with moderate crosslinking density further strengthens the physical entanglement and hydrogen bonding between the silk fibroin crosslinking network and the nanofiber, and promotes the formation of part of the oriented structure of the nanofiber, and finally promotes the formation of efficient reinforcing and toughening network structure of silk fibroin and nanofiber.

[0032] More specifically, a silk fibroin-nanofiber composite hydrogel with a moderately appropriate crosslinking density was first formed based on chemical crosslinking. Further gradient ethanol treatment and vacuum drying post-treatment "gently" induced the SF molecular chains to transition from random coils to β-pleated sheets, thereby forming a composite crosslinked network. This also enhanced the interaction between the silk fibroin crosslinked network and the nanofibers, as well as the partial orientation of the nanofibers. The gradient ethanol treatment combined with vacuum drying post-treatment facilitated the "slow" formation of a homogenized crystalline structure and homogenized shrinkage of the material, thereby avoiding the heterogeneous crystallization and shrinkage that would result from the initial formation of a dense crystalline structure on the surface. The formation of this homogenous crystalline structure also further strengthened the close connection between the silk fibroin crosslinked network and the nanofibers, through physical entanglement and hydrogen bonding, while promoting the formation of partially oriented nanofiber structures. The interaction and functional synergy between this homogenized crystalline structure and the nanofibers effectively enhanced the material's strength and toughness, resulting in the preparation of a silk fibroin-based functional material with both high strength and toughness. The overall process is milder than single-concentration high-concentration ethanol treatment, high-temperature drying or freeze-drying or other treatments. The formed β-pleated 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 properties.

[0033] Compared with the prior art, for example, patent CN106479195B can only form "mutual entanglement between nanofibers and silk fibroin molecular chains", while the present invention forms a composite structure of a chemical cross-linking network between silk fibroin molecules, a physical cross-linking network of entangled silk fibroin cross-linking network and nanofibers, a partially oriented structure of nanofibers, and a relatively regular β-folded crystal structure of silk fibroin. Patent CN106479195B does not involve the chemical cross-linking and physical cross-linking network (crystallization) of silk fibroin and the interaction structure between the related network and nanofibers. Moreover, in the prior art related to silk fibroin-based materials, the toughness that is higher than the strength of the present invention is far lower than that of the present invention, and the strength that is higher than the toughness of the present invention is far lower than that of the present invention. For example, the existing physical cross-linked silk fibroin hydrogel prepared by dehydration with anhydrous ethanol has a compression modulus of only 147KPa (Journal of Colloid and Interface Science 2023, 631, 46-55.); the existing chemical cross-linked silk fibroin hydrogel treated with a 75% volume fraction ethanol aqueous solution has a compression modulus of only 1.1MPa (Journal of the Mechanical Behavior of Biomedical Materials, 2023, 147: 106133.); the existing chemical cross-linked silk fibroin hydrogel treated with pure ethanol (volume concentration 100%) has a compression modulus of only 2.33MPa (Bioactive Materials 2024, 40, 541-556.).

[0034] Beneficial effects:

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

[0036] (2) The preparation method of the present invention is simple in process 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The fluorescence spectra of silk fibroin hydrogels Ru-1.6, Ru-1.2, Ru-0.8, and Ru-0.4 are shown in Figure 2. Figure 2 The fluorescence intensity histogram of silk fibroin hydrogels Ru-1.6, Ru-1.2, Ru-0.8, and Ru-0.4 (corresponding to a wavelength of 410 nm);

[0038] Figure 3 Figure 3 shows the real image of the final product of the experimental group and the control group of Example 3, wherein a and b represent the experimental group and the control group, respectively. DETAILED DESCRIPTION

[0039] The application will be further described with reference to the following examples. It should be understood that these examples are intended to illustrate the application and are not intended to limit the scope of the application. Furthermore, it should be understood that various modifications and changes can be made to the application by those skilled in the art upon reading the contents of this disclosure, which are intended to fall within the scope of the appended claims.

[0040] In order to fully disclose the properties of the substances used in the examples and comparative examples, the manufacturers of the substances are indicated in the application. In addition, the products of other manufacturers that meet the requirements of the application can also be suitable.

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

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

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

[0044] In the following examples, the preparation process of the oxidized bacterial cellulose nanofiber dispersion is as follows: TEMPO (2,2,6,6-tetramethylpiperidin-1-oxide free radical) and NaBr are dissolved in deionized water using a water bath ultrasonic method to obtain a mixed solution A, the mixed solution A is added to a bacterial cellulose (BC) dispersion (manufacturer: Nanjing Tianlu Nanotechnology Co., Ltd., model TL-008, solid content: 0.8%) and stirred uniformly, and then the pH value of the system is adjusted to 10 using a NaOH aqueous solution (mass fraction: 2%), and then NaC is added to the system. lO, an aqueous HCl solution (3.6% by mass) was added dropwise to adjust the pH of the system to 10.5, and then an aqueous HCl solution was continued to be added dropwise to adjust the pH of the system to 7 to terminate the reaction, thereby obtaining a mixed solution B. Finally, the mixed solution B was subjected to multiple centrifugation and washing operations to obtain an oxidized bacterial cellulose nanofiber (OBC) dispersion with a solid content of 1%; wherein the mass ratio of TEMPO to bacterial cellulose was 1:3000, the mass ratio of NaBr to bacterial cellulose was 1:500, and the mass ratio of NaClO to bacterial cellulose was 1:13.

[0045] Example 1

[0046] A method for preparing a high-strength and high-toughness silk fibroin-based material, comprising the following specific steps:

[0047] (1) Preparation of main materials;

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

[0049] Sodium carbonate solution: the solvent is deionized water, with a mass fraction of 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: the solvent is deionized water;

[0054] Oxidized bacterial cellulose nanofiber dispersion;

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

[0056] The raw silk was placed in a boiling sodium carbonate solution and boiled for 40 minutes, then taken out to obtain degummed silk. The degummed silk was repeatedly rinsed with deionized water until neutral and then drained. The degummed silk was then 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 deionized water to solution B of 100:1 and dialyzed for 96 hours (the deionized water was replaced every 12 hours) to obtain a silk fibroin solution.

[0057] (3) Preparation of silk fibroin precursor solution;

[0058] The silk fibroin solution, the Ru solution and the sodium persulfate solution are mixed uniformly to obtain a silk fibroin precursor solution;

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

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

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

[0062] Among them, in the mixed system of silk fibroin precursor solution and oxidized bacterial cellulose nanofiber dispersion, the mass fraction of oxidized bacterial cellulose nanofiber in the total solids is 0.3%;

[0063] The gradient ethanol treatment is divided into five stages; the volume concentration of the ethanol-water solution used in the first stage is 10%, the treatment time is 1 hour, the treatment temperature is 25°C, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol-water solution is 1:10; the volume concentration of the ethanol-water solution used in the second stage is 30%, the treatment time is 1 hour, the treatment temperature is 25°C, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol-water solution is 1:10; the volume concentration of the ethanol-water solution used in the third stage is 50%, the treatment time is 1 hour, the treatment temperature is 25°C, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol-water solution is 1:10; the volume concentration of the ethanol-water solution used in the fourth stage is 70%, the treatment time is 1 hour, the treatment temperature is 25°C, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol-water solution is 1:10; the fifth stage directly uses ethanol, the treatment time is 1 hour, the treatment temperature is 25°C, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol-water solution is 1:10;

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

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

[0066] Example 2

[0067] A method for preparing a high-strength and high-toughness silk fibroin-based material, comprising the following specific steps:

[0068] (1) Preparation of main materials;

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

[0070] Sodium carbonate solution: the solvent is deionized water, with a mass fraction of 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: the solvent is deionized water;

[0075] Oxidized bacterial cellulose nanofiber dispersion;

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

[0077] The raw silk was placed in a boiling sodium carbonate solution and boiled for 40 minutes, then taken out to obtain degummed silk. The degummed silk was repeatedly rinsed with deionized water until neutral and then drained. The degummed silk was then 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 deionized water to solution B of 100:1 and dialyzed for 96 hours (the deionized water was replaced every 12 hours) to obtain a silk fibroin solution.

[0078] (3) Preparation of silk fibroin precursor solution;

[0079] The silk fibroin solution, the Ru solution and the sodium persulfate solution are mixed uniformly to obtain a silk fibroin precursor solution;

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

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

[0082] After adding oxidized bacterial cellulose nanofiber dispersion to the silk fibroin precursor solution and uniformly dispersing it, the solution was placed under a light intensity of 50 mW / cm at 37 °C. 2 The silk fibroin-nanofiber composite hydrogel was irradiated with visible light for 60 minutes to obtain a silk fibroin-nanofiber composite hydrogel, which was then treated with gradient ethanol and vacuum dried to obtain a high-strength and high-toughness silk fibroin-based material.

[0083] Among them, in the mixed system of silk fibroin precursor solution and oxidized bacterial cellulose nanofiber dispersion, the mass fraction of oxidized bacterial cellulose nanofiber in the total solids is 1.5%;

[0084] The gradient ethanol treatment is divided into five stages; the first stage adopts an ethanol aqueous solution with a volume concentration of 30%, the treatment time is 2h, the treatment temperature is 37℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:50; the second stage adopts an ethanol aqueous solution with a volume concentration of 50%, the treatment time is 2h, the treatment temperature is 37℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:50; the third stage adopts an ethanol aqueous solution with a volume concentration of 70%, the treatment time is 2h, the treatment temperature is 37℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:50; the fourth stage adopts an ethanol aqueous solution with a volume concentration of 90%, the treatment time is 2h, the treatment temperature is 37℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:50; and the fifth stage directly adopts ethanol, the treatment time is 2h, the treatment temperature is 37℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:50.

[0085] The temperature of the vacuum drying after treatment is 25℃, the air pressure is 1kPa, and the time is 24h.

[0086] The compression modulus of the finally prepared high-strength and high-toughness silk fibroin-based material is 1.05GPa, and the bending fracture strain is 85%.

[0087] Example 3

[0088] A preparation method of a high-strength and high-toughness silk fibroin-based material, and the specific steps 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: solvent is deionized water, mass fraction is 44.7%;

[0094] Ru solution: solvent is deionized water;

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

[0096] Oxidized bacterial cellulose nanofiber dispersion;

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

[0098] The raw silk is taken out after being boiled in boiling sodium carbonate solution for 40 min to obtain degummed silk, and the degummed silk is repeatedly washed with deionized water until neutral, then drained, and then added into lithium bromide solution, stirred at 60℃ for 60 min to completely dissolve the degummed silk to obtain solution A, then solution A is filtered to obtain solution B, and then solution B is transferred into a dialysis bag with a molecular weight cut-off of 14000, and the dialysis bag is placed in deionized water for dialysis for 96h (the deionized water is replaced every 12h), to obtain a silk fibroin solution;

[0099] (3) preparing a silk fibroin precursor solution;

[0100] The silk fibroin solution, Ru solution and sodium persulfate solution are uniformly mixed to obtain a silk fibroin precursor solution;

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

[0102] (4) preparing a high-strength and high-toughness silk fibroin-based material;

[0103] After adding the oxidized bacterial cellulose nanofiber dispersion liquid into the silk fibroin precursor solution and uniformly dispersing, the mixture is irradiated with visible light with an intensity of 35mW / cm 2 at 31℃ for 30min to obtain a silk fibroin-nanofiber composite hydrogel, and the silk fibroin-nanofiber composite hydrogel is treated by gradient ethanol and vacuum drying to obtain a high-strength and high-toughness silk fibroin-based material;

[0104] In the mixed system of the silk fibroin precursor solution and the oxidized bacterial cellulose nanofiber dispersion liquid, the mass fraction of oxidized bacterial cellulose nanofiber in the total solid is 1%;

[0105] The gradient ethanol treatment is divided into five stages; the first stage adopts an ethanol aqueous solution with a volume concentration of 20%, the treatment time is 1.5 h, the treatment temperature is 31℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:30; the second stage adopts an ethanol aqueous solution with a volume concentration of 40%, the treatment time is 1.5 h, the treatment temperature is 31℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:30; the third stage adopts an ethanol aqueous solution with a volume concentration of 60%, the treatment time is 1.5 h, the treatment temperature is 31℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:30; the fourth stage adopts an ethanol aqueous solution with a volume concentration of 80%, the treatment time is 1.5 h, the treatment temperature is 31℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:30; and the fifth stage directly adopts ethanol, the treatment time is 1.5 h, the treatment temperature is 31℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:30.

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

[0107] The compression modulus of the finally prepared high-strength and high-toughness silk fibroin-based material is 1.25 GPa, and the bending fracture strain is 93%.

[0108] In order to prove that the gradient ethanol treatment and the vacuum drying post-treatment based on the formation of a medium crosslinking density hydrogel can improve the regularity of the structure, the following experiments are also carried out to verify this:

[0109] The experimental group is basically the same as this embodiment, and the only difference is that the oxidized bacterial cellulose nanofiber dispersion liquid is not added, and the prepared product is not a silk fibroin-nanofiber composite hydrogel, but a silk fibroin hydrogel;

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

[0111] The final products of the experimental group and the control group are as shown in Figure 3 As can be seen from Figure 3 , the final product of the experimental group has high transparency, and the "SF" characters below can be clearly seen; as can be seen from Figure 3As can be seen from FIG. 8, the final product of the control group has low transparency and the words below are blurred; it is shown that the gradient ethanol treatment combined with vacuum drying post-treatment can effectively improve the transparency of the material, because this treatment can induce the formation of regular and uniform β-sheet crystal structure of silk fibroin, and the regular and uniform β-sheet crystal structure can improve the transparency of the material, in contrast, the control group only uses a single high concentration of alcohol treatment combined with natural air drying post-treatment, which is not conducive to the formation of regular and uniform β-sheet crystal structure, resulting in poor material transparency. In addition, tests show that the compressive modulus of the final product of the experimental group is 0.3 GPa, and the compressive modulus of the final product of the control group is 0.03 GPa, further demonstrating the significant effect of gradient ethanol treatment and vacuum drying post-treatment on improving the regularity of β-sheet structure.

[0112] Example 4

[0113] A preparation method of a high-strength and high-toughness silk fibroin-based material, the specific steps 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: solvent is deionized water, mass fraction is 44.7%;

[0119] Riboflavin;

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

[0121] Oxidized bacterial cellulose nanofiber dispersion;

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

[0123] The raw silk is placed in the boiling sodium carbonate solution for 40 min and then taken out to obtain degummed silk, which is repeatedly washed with deionized water until neutral, then drained, and then added into lithium bromide solution, stirred at 60°C for 60 min to completely dissolve the degummed silk to obtain solution A, then solution A is filtered to obtain solution B, and then solution B is transferred into a dialysis bag with a molecular weight cut-off of 14000, and the dialysis bag is placed in deionized water with a mass ratio of deionized water to solution B of 100:1 for dialysis for 96 h (the deionized water is replaced every 12 h), to obtain a silk fibroin solution;

[0124] (3) Preparation of silk fibroin precursor solution;

[0125] The silk fibroin solution, riboflavin and sodium persulfate solution are uniformly mixed to obtain a silk fibroin precursor solution;

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

[0127] (4) preparing a high-strength and high-toughness silk fibroin-based material;

[0128] After adding and uniformly dispersing the oxidized bacterial cellulose nanofiber dispersion liquid in the silk fibroin precursor solution, the mixture is irradiated with visible light with an intensity of 20 mW / cm 2 for 15 min at 25℃ to obtain a silk fibroin-nanofiber composite hydrogel. The silk fibroin-nanofiber composite hydrogel is subjected to gradient ethanol treatment and vacuum drying after treatment to obtain a high-strength and high-toughness silk fibroin-based material.

[0129] In the mixture of the silk fibroin precursor solution and the oxidized bacterial cellulose nanofiber dispersion liquid, the mass fraction of oxidized bacterial cellulose nanofiber in the total solid is 0.3%.

[0130] The gradient ethanol treatment is divided into five stages. In the first stage, an ethanol aqueous solution with a volume concentration of 10% is used, the treatment time is 1 h, the treatment temperature is 25℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:10. In the second stage, an ethanol aqueous solution with a volume concentration of 30% is used, the treatment time is 1 h, the treatment temperature is 25℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:10. In the third stage, an ethanol aqueous solution with a volume concentration of 50% is used, the treatment time is 1 h, the treatment temperature is 25℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:10. In the fourth stage, an ethanol aqueous solution with a volume concentration of 70% is used, the treatment time is 1 h, the treatment temperature is 25℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:10. In the fifth stage, ethanol is directly used, the treatment time is 1 h, the treatment temperature is 25℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:10.

[0131] The temperature of the vacuum drying after treatment is 25℃, the gas pressure is 1 kPa, and the time is 8 h.

[0132] The compression modulus of the finally prepared high-strength and high-toughness silk fibroin-based material is 0.82 GPa, and the bending fracture strain is 81%.

[0133] Example 5

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

[0135] (1) Preparation of main materials;

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

[0137] Sodium carbonate solution: the solvent is deionized water, with a mass fraction of 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: the solvent is deionized water;

[0142] Oxidized bacterial cellulose nanofiber dispersion;

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

[0144] The raw silk was placed in a boiling sodium carbonate solution and boiled for 40 minutes, then taken out to obtain degummed silk. The degummed silk was repeatedly rinsed with deionized water until neutral and then drained. The degummed silk was then 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 deionized water to solution B of 100:1 and dialyzed for 96 hours (the deionized water was replaced every 12 hours) to obtain a silk fibroin solution.

[0145] (3) Preparation of silk fibroin precursor solution;

[0146] The silk fibroin solution, riboflavin and sodium persulfate solution are mixed uniformly to obtain a silk fibroin precursor solution;

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

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

[0149] After adding oxidized bacterial cellulose nanofiber dispersion to the silk fibroin precursor solution and uniformly dispersing it, the solution was placed under a light intensity of 50 mW / cm at 37 °C. 2 The silk fibroin-nanofiber composite hydrogel was irradiated with visible light for 60 minutes to obtain a silk fibroin-nanofiber composite hydrogel, which was then treated with gradient ethanol and vacuum dried to obtain a high-strength and high-toughness silk fibroin-based material.

[0150] In the mixed system of the silk fibroin precursor solution and the oxidized bacterial cellulose nanofiber dispersion, the mass fraction of the oxidized bacterial cellulose nanofiber in the total solid is 1.5%;

[0151] The gradient ethanol treatment is divided into five stages; in the first stage, the volume concentration of the ethanol aqueous solution is 30%, the treatment time is 2h, the treatment temperature is 37℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:50; in the second stage, the volume concentration of the ethanol aqueous solution is 50%, the treatment time is 2h, the treatment temperature is 37℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:50; in the third stage, the volume concentration of the ethanol aqueous solution is 70%, the treatment time is 2h, the treatment temperature is 37℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:50; in the fourth stage, the volume concentration of the ethanol aqueous solution is 90%, the treatment time is 2h, the treatment temperature is 37℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:50; in the fifth stage, ethanol is directly used, the treatment time is 2h, the treatment temperature is 37℃, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:50;

[0152] The temperature of the vacuum drying after treatment is 25℃, the air pressure is 1kPa, and the time is 24h.

[0153] The compression modulus of the finally prepared high-strength and high-toughness silk fibroin-based material is 0.93GPa, and the bending fracture strain is 85%.

[0154] Example 6

[0155] A preparation method of a high-strength and high-toughness silk fibroin-based material, and the specific steps 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: solvent is deionized water, mass fraction is 44.7%;

[0161] Riboflavin;

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

[0163] Oxidized bacterial cellulose nanofiber dispersion;

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

[0165] The raw silk is taken out after being boiled in the boiling sodium carbonate solution for 40 min, to obtain degummed silk, and the degummed silk is repeatedly washed with deionized water until neutral, and then drained, and then added into a lithium bromide solution, and stirred at 60℃ for 60 min to completely dissolve the degummed silk to obtain solution A, and then solution A is filtered to obtain solution B, and then solution B is transferred into a dialysis bag with a molecular weight cut-off of 14000, and the dialysis bag is placed in deionized water for dialysis for 96h (the deionized water is replaced every 12h), to obtain a silk fibroin solution;

[0166] (3) preparing a silk fibroin precursor solution;

[0167] The silk fibroin solution, riboflavin and sodium persulfate solution are uniformly mixed to obtain a silk fibroin precursor solution;

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

[0169] (4) preparing a high-strength and high-toughness silk fibroin-based material;

[0170] After the oxidized bacterial cellulose nanofiber dispersion liquid is added into the silk fibroin precursor solution and uniformly dispersed, the mixture is irradiated with visible light with an intensity of 35mW / cm 2 at 31℃ for 30min to obtain a silk fibroin-nanofiber composite hydrogel, and the silk fibroin-nanofiber composite hydrogel is subjected to gradient ethanol treatment and vacuum drying aftertreatment to obtain a high-strength and high-toughness silk fibroin-based material;

[0171] In the mixed system of the silk fibroin precursor solution and the oxidized bacterial cellulose nanofiber dispersion liquid, the mass fraction of oxidized bacterial cellulose nanofiber in the total solid is 1%;

[0172] The gradient ethanol treatment is divided into five stages; the volume concentration of the ethanol aqueous solution used in the first stage is 20%, the treatment time is 1.5 h, the treatment temperature is 31 DEG C, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:30; the volume concentration of the ethanol aqueous solution used in the second stage is 40%, the treatment time is 1.5 h, the treatment temperature is 31 DEG C, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:30; the volume concentration of the ethanol aqueous solution used in the third stage is 60%, the treatment time is 1.5 h, the treatment temperature is 31 DEG C, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:30; the volume concentration of the ethanol aqueous solution used in the fourth stage is 80%, the treatment time is 1.5 h, the treatment temperature is 31 DEG C, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:30; and the fifth stage directly uses ethanol, the treatment time is 1.5 h, the treatment temperature is 31 DEG C, and the volume ratio of the silk fibroin-nanofiber composite hydrogel to the ethanol aqueous solution is 1:30.

[0173] The temperature of the vacuum drying after treatment is 25 DEG C, the air pressure is 1 kPa, and the time is 16 h.

[0174] The compression modulus of the finally prepared high-strength and high-toughness silk fibroin-based material is 1.02 GPa, and the bending fracture strain is 90%.

[0175] The high-strength and high-toughness silk fibroin-based material prepared in the embodiments 1 to 6 has excellent biocompatibility and degradability, and the strength and toughness are significantly improved, and has a wide application prospect in the field of biomedical materials.

[0176] The application also explores the influence of different concentrations of Ru and sodium persulfate on the crosslinking density of the silk fibroin hydrogel through experiments, and the specific experimental process is as follows:

[0177] (1) Preparation of materials;

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

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

[0180] Deionized water;

[0181] Lithium bromide solution: deionized water as solvent, mass fraction is 44.7%;

[0182] Ru solution: deionized water as solvent;

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

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

[0185] The raw silk was placed in a boiling sodium carbonate solution and boiled for 40 minutes, then taken out to obtain degummed silk. The degummed silk was repeatedly rinsed with deionized water until neutral and then drained. The degummed silk was then 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 deionized water to solution B of 100:1 and dialyzed for 96 hours (the deionized water was replaced every 12 hours) to obtain a silk fibroin solution.

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

[0187] The silk fibroin solution, the Ru solution and the sodium persulfate solution are mixed evenly to obtain silk fibroin precursor solutions 1 to 4;

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

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

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

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

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

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

[0194] At 31°C, the silk fibroin precursor solutions 1 to 4 were respectively subjected to a light intensity of 35 mW / cm 2 After irradiation with visible light for 45 min, silk fibroin hydrogels 1 to 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] The fluorescence spectra of Ru-1.6, Ru-1.2, Ru-0.8 and Ru-0.4 were tested using a fluorescence spectrometer and the fluorescence intensity was recorded. The test results are as follows:Figure 1 As shown, from Figure 1 It can be seen that with the increase of the mass fraction of Ru and sodium persulfate in the silk fibroin precursor solution, the peak value of the corresponding characteristic peak in the fluorescence spectrum gradually increases, among which the peak value of the characteristic peak at 410nm is proportional to the relative chemical cross-linking point content of the silk fibroin hydrogel; Figure 2 It can be seen from the fluorescence spectrum that the relative fluorescence intensity at 410nm also shows a trend of gradual increase. Figure 2 The spectral data show that the cross-linking point content of different hydrogels is Ru-1.6, Ru-1.2, Ru-0.8, and Ru-0.4 from high to low; this indicates that with the increase of the mass fraction of Ru and sodium persulfate, the content of chemical cross-linking points in the silk fibroin hydrogel gradually increases, and the cross-linking density gradually increases, indicating that the cross-linking density of silk fibroin can be regulated by the mass fraction of Ru and sodium persulfate.

[0198] Comparative Example 1

[0199] A method for preparing a silk fibroin-based material, which differs from Example 1 only in that: when preparing the silk fibroin precursor solution, the addition amounts of Ru solution and sodium persulfate solution are adjusted; 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 has a compression modulus of 0.45 GPa and a bending fracture strain of 58%.

[0201] Compared with Example 1, the compression modulus and bending fracture strain of the silk fibroin-based material in Comparative Example 1 are significantly reduced. This is because the mass fraction of Ru and sodium persulfate in the silk fibroin precursor solution is too low, which is not conducive to the initial material (silk fibroin hydrogel) molding support, that is, it is not conducive to the formation of a silk fibroin chemical cross-linking network with sufficient supporting capacity; at the same time, it is not conducive to the regular and uniform arrangement of the β-pleated structure formed in the subsequent gradient ethanol treatment and vacuum drying post-treatment process.

[0202] Comparative Example 2

[0203] A method for preparing a silk fibroin-based material, which differs from Example 2 only in that: when preparing the silk fibroin precursor solution, the addition amounts of Ru solution and sodium persulfate solution are adjusted; 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 has a compression modulus of 0.65 GPa and a bending fracture strain of 65%.

[0205] Compared with Example 2, the compression modulus and bending fracture strain of the silk fibroin-based material of Comparative Example 2 are obviously reduced, because the mass fraction of Ru and sodium persulfate in the silk fibroin precursor solution is too high, the movement of the hydrophobic segment of the "high crosslinking density" hydrogel is limited, and the formation of the beta-sheet crystalline structure and the regular and uniform arrangement of the beta-sheet crystalline structure in the subsequent gradient ethanol treatment and vacuum drying post-processing process are not conducive.

[0206] Comparative Example 3

[0207] A method for preparing a silk fibroin-based material, and the difference between Example 4 is that when preparing the silk fibroin precursor solution, the amount of riboflavin and sodium persulfate solution added is adjusted; 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 compression modulus of the finally prepared silk fibroin-based material is 0.42 GPa, and the bending fracture strain is 55%.

[0209] Compared with Example 4, the compression modulus and bending fracture strain of the silk fibroin-based material of Comparative Example 3 are obviously reduced, because the mass fraction of riboflavin and sodium persulfate in the silk fibroin precursor solution is too low, which is not conducive to the formation of the initial material (silk fibroin hydrogel) forming support, that is, the silk fibroin chemical crosslinking network with sufficient support ability cannot be formed; and it is not conducive to the regular and uniform arrangement of the beta-sheet structure formed in the subsequent gradient ethanol treatment and vacuum drying post-processing process.

[0210] Comparative Example 4

[0211] A method for preparing a silk fibroin-based material, and the difference between Example 5 is that when preparing the silk fibroin precursor solution, the amount of riboflavin and sodium persulfate solution added is adjusted; 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 compression modulus of the finally prepared silk fibroin-based material is 0.60 GPa, and the bending fracture strain is 60%.

[0213] Compared with Example 5, the compression modulus and bending fracture strain of the silk fibroin-based material of Comparative Example 4 are obviously reduced, because the mass fraction of riboflavin and sodium persulfate in the silk fibroin precursor solution is too high, the movement of the hydrophobic segment of the "high crosslinking density" hydrogel is limited, and the formation of the beta-sheet crystalline structure and the regular and uniform arrangement of the beta-sheet crystalline structure in the subsequent gradient ethanol treatment and vacuum drying post-processing process are not conducive.

Claims

1. A method for preparing a high-strength and high-toughness silk fibroin-based material, characterized by: After adding nanofiber dispersion to the silk fibroin precursor solution and uniformly dispersing it, the silk fibroin-nanofiber composite hydrogel was obtained by chemical cross-linking induced by visible light at 25-37°C. The silk fibroin-nanofiber composite hydrogel was then treated with gradient ethanol and vacuum dried to obtain a high-strength and high-toughness silk fibroin-based material. The silk fibroin precursor solution is prepared by mixing a silk fibroin solution, a tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate solution, and a sodium persulfate solution. In the silk fibroin precursor solution, the mass fraction of silk fibroin is 13-17%, the mass fraction of tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate is 0.075-0.15%, and the mass fraction of sodium persulfate is 0.2-0.4%. Alternatively, the silk fibroin precursor solution is obtained by mixing a silk fibroin solution, riboflavin, and a 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%.

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

4. The method for preparing a high-strength and high-toughness silk fibroin-based material according to claim 1, characterized in that: The gradient ethanol treatment is divided into five stages. The volume concentration of the ethanol aqueous solution used in each stage increases in the range of 10~100%. The treatment time of each stage is 1~2h, and the treatment temperature is 25~37℃.

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

7. A high-strength and high-toughness silk fibroin-based material, characterized by: Prepared by the preparation method of a high-strength and high-toughness silk fibroin-based material according to any one of claims 1 to 6; High-strength and high-tenacity 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-pleated crystal structure, and the nanofibers have a partially oriented structure.

8. The high-strength and high-toughness silk fibroin-based material according to claim 7, characterized in that: The nanofibers are oxidized bacterial cellulose nanofibers, silk fibroin nanofibers or collagen nanofibers; the aspect ratio of the nanofibers is 70-110:

1.

9. The high-strength and high-toughness silk fibroin-based material according to claim 8, characterized in that: The compression modulus of the high-strength and high-toughness silk fibroin-based material is ≥0.8GPa, and the bending fracture strain is ≥80%.

10. Use of a high-strength and high-toughness silk fibroin-based material according to any one of claims 7 to 9, characterized in that: Used in the field of biomedical materials.

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