Controllable molecular weight silk fibroin profile and preparation method and application thereof

Abstract

The invention belongs to the field of implantable medical devices, and relates to a controllable molecular weight silk fibroin profile and a preparation method and application thereof, and the method comprises the following steps: adding cellulose derivatives into silk fibroin salt solutions with different molecular weights for swelling; in the silk fibroin salt solutions with different molecular weights, the narrow-distribution controllable high-molecular-weight silk fibroin salt solution has the index average molecular weight of 10 kDa to 80 kDa, 80 kDa to 100 kDa, 100 kDa to 120 kDa, 120 kDa to 160 kDa, 160 kDa to 200 kDa and more than 200 kDa. Filling the swelled silk fibroin salt solution into a dialysis bag with a specific shape and size, desalting in deionized water, and forming gel; finally, the obtained gel is taken out and slowly dried and shaped in a constant-temperature and constant-humidity environment, and the silk fibroin hard profile is obtained. The prepared silk fibroin profile has the advantages of being good in strength, green, non-toxic, easy to amplify and the like and can be further applied to the field of implantable medical devices, and the preparation method is high in efficiency, rapid in forming and more suitable for batch production and industrial production.

Description

Technical Field

[0001] The present invention relates to the field of implantable medical devices, and particularly to a controllable molecular weight fibroin profile and its preparation method and uses. Background Art

[0002] Currently, the number of patients with bone defect repair and internal fixation of fractures has increased rapidly, and patients have put forward higher requirements for safe and effective implants and implantable medical devices. Bone repair screws are commonly used internal fixation devices and play an irreplaceable role in bone defect repair and functional reconstruction.

[0003] Fibroin is an extract of natural silk cocoons. After modification, it has excellent mechanical properties and physical and chemical properties; at the same time, it has good biocompatibility and biodegradability in the human body. The degradation products are amino acids and polypeptides, which have no toxic effect on the human body. Also, due to its rich source and easy preparation, it has been widely used in the field of biomedical materials. Biological research shows that fibroin has good osteoinductive activity and can promote biological functions such as the growth, proliferation, and differentiation of osteoblasts, and has gradually become an excellent candidate material for the preparation of bone repair screws. Currently, the research on using fibroin to manufacture bone implant materials mainly focuses on optimizing and improving the mechanical properties and biocompatibility of the materials, as well as optimizing the osteoinductive and osseointegrative properties of the materials. The main directions are new preparation methods and coating modification of the surface of metal materials.

[0004] Fibroin materials are mainly prepared from silk cocoons through degumming, dissolution, dialysis, and modification operations. Soft materials such as sutures and dressing gels made of degummed silk have been widely studied and applied clinically, but there are still many difficulties in the process of fibroin hard materials. On the one hand, the preparation of fibroin hard materials needs to solve key technical problems such as bubbles, large-size preparation, and brittle mechanical properties in traditional processes. On the other hand, in the production process of traditional fibroin hard materials, there are some toxic gas components such as hexafluoroisopropanol, and the hard materials prepared by solution drying are small in size and cannot be industrially promoted. Therefore, improving the production process of fibroin hard materials and realizing the preparation of fibroin materials with better performance, green and non-toxic will have broad market prospects. Summary of the Invention

[0005] Aiming at the problems of poor strength, slow forming, and inability to achieve large-size manufacturing existing in the existing fibroin hard materials, the purpose of the present invention is to provide a preparation method of a controllable molecular weight fibroin profile.

[0006] To achieve the above purpose, a controllable molecular weight fibroin profile and its preparation method according to the present invention include:

[0007] S1: Preparation of silk fibroin salt solution, which includes silk fibroin and cellulose derivatives; S2: Formation of gel; S3: Drying and shaping;

[0008] The preparation method does not include any physical crosslinking agent and chemical crosslinking agent. Preferably, no crosslinking method is used for crosslinking. More preferably, it does not include any other additives. Most preferably, the profile is composed of silk fibroin and cellulose derivatives.

[0009] The above method includes the following steps:

[0010] S1: Cellulose derivatives are added to silk fibroin salt solutions with different molecular weights (preferably with a silk fibroin concentration of 30 mg / ml - 200 mg / ml) for swelling to obtain a solution with swelling completed; the salt solution of the narrow-distribution controllable high-molecular-weight silk fibroin refers to the number-average molecular weight (preferably measured by rheological method) of 10 kDa - 80 kDa, 80 kDa - 100 kDa, 100 kDa - 120 kDa, 120 kDa - 160 kDa, 160 kDa - 200 kDa, > 200 kDa; preferably, the silk fibroin concentration in the silk fibroin salt solution is 30 mg / ml - 200 mg / ml; the salt solution preferably also includes lithium bromide;

[0011] S2: The solution after swelling is filled into a dialysis bag with a specific shape and size and placed in deionized water for desalting and forming a gel;

[0012] S3: The formed gel is slowly left standing for drying and shaping in a constant temperature and humidity environment to obtain a silk fibroin profile, and the profile is preferably a hard profile.

[0013] Furthermore, in step S1, by mass ratio, silk fibroin:cellulose derivative = 6 - 12:0.2 - 1.5, the swelling environment is 2 - 8 °C, and the swelling time is 24 - 72 h. The silk fibroin salt solution is a silk fibroin solution that has not been desalted and purified, and one or more of cellulose derivatives I, and specific examples are as follows:

[0014] I: Cellulose derivatives, preferably selected from one or more of carboxyl cellulose, alkyl cellulose or hydroxy cellulose, more preferably one or more of sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose.

[0015] Furthermore, in step S2, after complete swelling, the dialysis bag is placed in deionized water for desalting for 48 - 96 h, and the deionized water is replaced every 1 hour until the solution in the dialysis bag is dialyzed into a gel state. The shape of the dialysis bag can be one or more of spherical, cylindrical, and elliptical.

[0016] Further, in step S3, the drying and shaping is carried out in an environment with a constant temperature and humidity. The constant temperature value in the constant temperature and humidity chamber is 20-60 °C, and the humidity is 20%RH-40%RH.

[0017] A controllable molecular weight silk fibroin profile is prepared by the above method.

[0018] Further, the silk fibroin profile can resist the internal stress generated during the gelation and drying processes. Its Young's modulus is 800-1200 MPa, and its density is 0.9-1.1 g / cm 3 , which is close to the density of human bone, and the Young's modulus is 1000-1200 MPa.

[0019] Preferably, the silk fibroin profile does not include any physical cross-linking agent or chemical cross-linking agent, and no cross-linking method is used. It also does not include any other additives.

[0020] Further preferably, the silk fibroin profile is composed of silk fibroin and a cellulose derivative.

[0021] The cellulose derivative is selected from one or more of carboxymethyl cellulose, alkyl cellulose or hydroxy cellulose, and more preferably one or more of sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose;

[0022] Further, the Young's modulus of the profile is 800-1200 MPa, preferably 1000-1200 MPa, and its density is 0.9-1.1 g / cm 3 .

[0023] The application of the above silk fibroin profile is characterized in that the application includes: preparing materials in the biomedical field, and the prepared materials in the biomedical field are used for bone repair materials, surgical sutures, tissue engineering scaffolds and biodegradable packaging materials.

[0024] Preferably, in step S1, the molecular weight of the silk fibroin salt solution used is (10 kDa-80 kDa, 80 kDa-100 kDa, 100 kDa-120 kDa, 120 kDa-160 kDa, 160 kDa-200 kDa, >200 kDa). The test method refers to Appendix B of the industry standard "Silk Fibroin for Tissue Engineering Medical Devices" (YY / T 1950-2024). The measured rheological data and viscosity data are imported into the Favorsun SmartMolFit "Complex Directional Intelligent Calculation" commercial software for calculating the number average molecular weight and weight average molecular weight.

[0025] Preferably, in step S1, by mass ratio, silk fibroin:cellulose derivative = 6 - 12:0.2 - 1.5. The swelling environment is 2 - 8°C, and the swelling time is 24 - 72 h. More preferably, silk fibroin:cellulose derivative = 8 - 12:0.8 - 1.2. The swelling environment is 2 - 8°C, and the swelling time is 48 - 72 h.

[0026] Preferably, in step S1, in the swelling solution, the cellulose derivative substances include but are not limited to sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose and other cellulose derivatives.

[0027] Preferably, in step S2, after complete swelling, place the dialysis bag in deionized water for desalting for 48 - 96 h (replace the deionized water every 1 hour until the solution in the dialysis bag is dialyzed to a gel state). More preferably, the dialysis bag is placed in deionized water for desalting for 72 - 96 h (replace the deionized water every 1 hour until the solution in the dialysis bag is dialyzed to a gel state).

[0028] Preferably, in step S2, the shape of the dialysis bag can be spherical, cylindrical or oval. More preferably, it is cylindrical.

[0029] Preferably, in step S3, place the formed gel in a constant temperature and humidity environment and slowly stand still for drying and shaping to obtain a silk fibroin rigid profile.

[0030] This rigid profile has high rigidity and mechanical properties close to those of natural cancellous bone (the cancellous bone Young's modulus range is 1000 MPa - 2000 MPa).

[0031] The shaping environment is that the constant temperature value in the constant temperature and humidity box is 20 - 60°C, and the humidity is 20%RH - 40%RH. More preferably, the temperature is 35 - 45°C, and the humidity is 25%RH - 35%RH.

[0032] In the present invention, the cellulose derivative may play the following roles:

[0033] (1) Enhance material properties: The cellulose derivative can help the silk protein form a uniform gel network and crystalline regions to enhance the mechanical properties of the silk fibroin profile, such as improving strength, toughness or elastic modulus, etc. This enhancement effect stems from the interaction between the cellulose derivative and the silk fibroin, such as chemical bonding, physical entanglement or hydrogen bond binding, etc.

[0034] (2) Regulate the degradation rate: The cellulose derivative optimizes its application in the biomedical field by affecting the degradation rate of the silk fibroin. By adjusting the type, content or structure of the cellulose derivative, precise control of the silk fibroin degradation rate can be achieved to meet the needs of different tissue repair and regeneration.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] (1) The fibroin profile can be prepared only with fibroin and cellulose derivatives. The steps are simple, and it can be processed into a specified shape through subsequent processing. Existing profiles are usually processed from metal products. Compared with metal processed products, the fibroin profile has less rejection reaction when implanted into the body from natural extraction and better affinity.

[0037] (2) It is possible to synthesize fibroin profiles with specific molecular weights according to specific requirements. For example, in the field of biomedicine, if it is necessary for fibroin profiles to interact with specific cell receptors, the molecular weight can be customized according to cell characteristics to make it have better biocompatibility to adapt to different medical application scenarios, such as the preparation of scaffold materials in tissue engineering, etc.

[0038] (3) Cellulose derivatives can help silk proteins form a uniform gel network and crystalline regions to enhance the mechanical properties of fibroin profiles, such as improving strength, toughness, or elastic modulus, etc.

[0039] (4) The fibroin profile is degradable, and the degradation rate of all fibroin profiles can reach 50% or more at 24 weeks in a simulated actual blood environment. Description of the Drawings

[0040] Figure 1 : SEM image of the fibroin profile after gelation in Example 1

[0041] Figure 2 : Picture of the fibroin profile after dehydration and forming in Example 1

[0042] Figure 3 : Picture of the fibroin profile after processing in Example 1

[0043] Figure 4 : Data graph of the density and Young's modulus of the fibroin profiles in Examples 1 - 4 and Comparative Example 1

[0044] Figure 5 : Summary graph of the fibroin profiles and mass residue ratio in Examples 1 - 4 and Comparative Example 1 Detailed Embodiments

[0045] The technical solution of the present invention will be further described and illustrated below through specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are only used to assist in understanding the present invention and are not used for specific limitations of the present invention. And the accompanying drawings used in this article are only for better illustrating the content disclosed by the present invention and do not have a limiting effect on the protection scope. Unless otherwise specified, the raw materials used in the embodiments of the present invention are common raw materials in the art, and the methods used in the embodiments are conventional methods in the art.

[0046] Example 1:

[0047] (1) Silk fibroin swelling: Take a certain amount of hydroxypropyl methylcellulose (HPMC) powder and place it in a silk fibroin solution salt solution (where the molecular weight of silk fibroin is 160 kDa to 200 kDa and the concentration is 50 mg / ml). The mass ratio of silk fibroin to HPMC is 9:1. Swell in a refrigerator at 2 - 8 °C for 48 h and then set aside.

[0048] (2) Silk fibroin gel preparation: After complete swelling, place the silk fibroin solution in a dialysis bag and place the dialysis bag in deionized water. Replace the deionized water every 1 hour. After dialysis for 48 hours, the solution in the dialysis bag becomes a gel state. The SEM of the gel state product is as Figure 1 shown.

[0049] (3) Profile dehydration and forming: The gel obtained by dialysis is placed in a constant temperature and humidity chamber for uniform dehydration. Set the temperature and humidity to be constant at 35 °C and 25% RH respectively. After 72 h, a rod-shaped profile finished product is obtained. The picture of the rod-shaped profile is as Figure 2 shown, and its product after simple processing is as Figure 3 shown.

[0050] The density of the profile prepared is 0.98 g / cm 3 , and the Young's modulus is 1200 MPa (as Figure 4 ).

[0051] Example 2:

[0052] (1) Silk fibroin swelling: Take a certain amount of hydroxypropyl methylcellulose (HPMC) powder and place it in a silk fibroin solution salt solution (where the molecular weight of silk fibroin is 160 kDa to 200 kDa and the concentration is 50 mg / ml). The mass ratio of silk fibroin to HPMC is 12:1. Swell in a refrigerator at 2 - 8 °C for 48 h and then set aside.

[0053] (2) Silk fibroin gel preparation: After complete swelling, place the silk fibroin solution in a dialysis bag and place the dialysis bag in deionized water. Replace the deionized water every 1 hour. After dialysis for 48 hours, the solution in the dialysis bag becomes a gel state.

[0054] (3) Profile dehydration and forming: The gel obtained by dialysis is placed in a constant temperature and humidity chamber for uniform dehydration. The temperature and humidity are set to be constant at 35 °C and 25% RH respectively. After 72 hours, the finished rod-shaped profile is obtained.

[0055] (4) The density of the profile prepared is 0.99 g / cm 3 , and the Young's modulus is 1159 MPa (as Figure 4 ).

[0056] Example 3:

[0057] (1) Silk fibroin swelling: A certain amount of carboxymethyl cellulose (CMC) powder is placed in a silk fibroin solution salt solution (where the molecular weight of silk fibroin is 160 kDa - 200 kDa and the concentration is 50 mg / ml). The mass ratio of silk fibroin to CMC is 9:1. It is left to swell in a refrigerator at 2 - 8 °C for 48 hours and then set aside.

[0058] (2) Silk fibroin gel preparation: After complete swelling, the silk fibroin solution is placed in a dialysis bag, and the dialysis bag is placed in deionized water. The deionized water is replaced every 1 hour. After 48 hours of dialysis, the solution in the dialysis bag becomes gel-like.

[0059] (3) Profile dehydration and forming: The gel obtained by dialysis is placed in a constant temperature and humidity chamber for uniform dehydration. The temperature and humidity are set to be constant at 35 °C and 25% RH respectively. After 72 hours, the finished rod-shaped profile is obtained.

[0060] (4) The density of the profile prepared is 1.07 g / cm 3 , and the Young's modulus is 1174 MPa (as Figure 4 ).

[0061] Example 4:

[0062] (1) Silk fibroin swelling: A certain amount of hydroxyethyl cellulose powder is placed in a silk fibroin solution salt solution (where the molecular weight of silk fibroin is 160 kDa - 200 kDa and the concentration is 50 mg / ml). The mass ratio of silk fibroin to hydroxyethyl cellulose is 9:1. It is left to swell in a refrigerator at 2 - 8 °C for 48 hours and then set aside.

[0063] (2) Silk fibroin gel preparation: After complete swelling, the silk fibroin solution is placed in a dialysis bag, and the dialysis bag is placed in deionized water. The deionized water is replaced every 1 hour. After 48 hours of dialysis, the solution in the dialysis bag becomes gel-like.

[0064] (3) Profile dehydration and forming: The gel obtained by dialysis is placed in a constant temperature and humidity chamber for uniform dehydration. The temperature and humidity are set to be constant at 35 °C and 25% RH respectively. After 72 hours, the finished rod-shaped profile is obtained.

[0065] (4) The density of the profile prepared therefrom is 1.02 g / cm 3 , and the Young's modulus is 1065 MPa (as Figure 4 ).

[0066] Comparative Example 1: Adjust the dosage ratio of silk fibroin and cellulose

[0067] (1) Swelling of silk fibroin: Take a certain amount of hydroxypropyl methylcellulose (HPMC) powder and place it in a silk fibroin solution salt solution (where the molecular weight of silk fibroin is 160 kDa - 200 kDa and the concentration is 50 mg / ml). The mass ratio of silk fibroin to HPMC is 13:0.2. Swell it in a refrigerator at 2 - 8 °C for 48 h and then set aside for use.

[0068] (2) Preparation of silk fibroin gel: After complete swelling, place the silk fibroin solution in a dialysis bag and place the dialysis bag in deionized water. Replace the deionized water every 1 hour. After dialysis for 48 hours, the solution in the dialysis bag becomes gel state.

[0069] (3) Dehydration and molding of the profile: Place the gel obtained by dialysis in a constant temperature and humidity chamber for uniform dehydration. Set the temperature and humidity to be constant at 35 °C and 25% RH respectively. After 72 h, obtain the finished rod-shaped profile.

[0070] (4) The density of the profile prepared therefrom is 0.79 g / cm 3 , and the Young's modulus is 840 MPa (as Figure 4 )

[0071] Comparative Example 2: Do not add cellulose or cellulose derivatives

[0072] (1) Swelling of silk fibroin: Take a silk fibroin solution salt solution (where the molecular weight of silk fibroin is 160 kDa - 200 kDa and the concentration is 50 mg / ml). Swell it in a refrigerator at 2 - 8 °C for 48 h and then set aside for use.

[0073] (2) Preparation of silk fibroin gel: After complete swelling, place the silk fibroin solution in a dialysis bag and place the dialysis bag in deionized water. Replace the deionized water every 1 hour. It has never been able to reach the gel state.

[0074] Comparative Example 3: Adjust the swelling time

[0075] (1) Swelling of silk fibroin: Take a certain amount of hydroxypropyl methylcellulose (HPMC) powder and place it in a silk fibroin solution salt solution (where the molecular weight of silk fibroin is 160 kDa - 200 kDa and the concentration is 50 mg / ml). The mass ratio of silk fibroin to HPMC is 9:1. Swell it in a refrigerator at 2 - 8 °C for 10 h and then set aside for use.

[0076] (2) Preparation of silk fibroin gel: After complete swelling, the silk fibroin solution was placed in a dialysis bag, and the dialysis bag was placed in deionized water. The deionized water was replaced every 1 hour. A uniform gel state could not be formed, with part of it being gel and part being in solution state.

[0077] In this invention, the samples obtained from Example 1, Example 2, Example 3, Example 4 and Comparative Example 1 were placed in a 200 mL PBS solution with pH = 7.4 containing 1% sodium dodecyl sulfate (SDS) to simulate the actual blood environment for product degradation. The weight of the profile at 0 point was recorded, and it was weighed at 2 weeks, 4 weeks, 8 weeks, 16 weeks and 24 weeks respectively, and its mass loss rate was calculated (see Figure 5 ). The data is shown in the table as follows:

[0078] Table 1: Summary of weight data of silk fibroin profiles at different times

[0079] Initial weight (g) Mass at 2 weeks (g) Mass at 8 weeks (g) Mass at 16 weeks (g) Mass at 24 weeks (g) Example 1 10.23 9.97 8.01 6.87 4.23 Example 2 10.45 10.22 8.12 5.56 3.33 Example 3 10.97 10.01 7.65 5.42 3.21 Example 4 9.98 9.54 8.34 4.04 3.25 Comparative Example 1 11.02 9.87 5.43 3.21 1.01

[0080] It can be seen from the examples of the comparative example and the examples that when cellulose derivatives are added and the swelling is complete, the Young's modulus (Example 1, Example 2, Example 3 and Example 4) can reach 1000 MPa - 1200 MPa. Among them, the content of cellulose determines the Young's modulus data of the silk fibroin profile. When the cellulose is the same kind of cellulose, the higher the cellulose content (Example 1 and Example 2), the higher its Young's modulus. In the case of similar cellulose content, the degradation rate of HPMC is slower (Example 1, Example 2 and Example 3), and it can be used for a longer time.

[0081] Among them, the cellulose content and type directly affect the Young's modulus of the profile, and the swelling time affects the uniformity of the profile. If the complete swelling time of cellulose is not reached, a uniform gel cannot be formed, and subsequent dehydration and molding to form a rigid profile cannot be carried out.

[0082] The higher the cellulose content, the generally greater the Young's modulus of the profile, because cellulose provides structural support and rigidity. Too low content will lead to insufficient strength of the profile. Different types of cellulose (such as microcrystalline cellulose, nanocellulose, etc.) have different effects on the Young's modulus due to their different degrees of polymerization, crystallinity and molecular arrangement. Cellulose with high crystallinity can usually provide higher rigidity.

[0083] Swelling is the process of cellulose absorbing water and swelling in a solvent, which relaxes the molecular chain and facilitates subsequent molding. If the swelling time is insufficient, the cellulose cannot swell sufficiently, resulting in non-uniform gel and affecting the physical properties of the profile. Although too long swelling time can ensure sufficient swelling, it may cause cellulose degradation or other side effects, and a balance needs to be found between sufficient swelling and avoiding degradation. It can be known from the comparison between Example 1 and Comparative Example 3 that the swelling time of Comparative Example 3 is too short to form a uniform gel, and a uniform gel cannot be formed, and a rigid profile cannot be formed subsequently.

[0084] The uniform gel is the basis for subsequent dehydration and forming, ensuring consistent density and strength throughout the profile. If the gel is non-uniform, problems such as stress concentration, deformation, or cracking may occur in the profile after dehydration and forming.

[0085] The dehydration process removes excess moisture, causing the cellulose molecules to bind tightly and form a rigid structure. After dehydration, the cellulose molecules are closely arranged to form a rigid profile with high density and strength.

[0086] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a silk fibroin profile with controllable molecular weight, characterized in that, Including the following steps: S1: Preparation of silk fibroin salt solution, which includes swelling of silk fibroin and cellulose derivative; S2: Formation of gel; S3: Drying and shaping.

2. The preparation method according to claim 1, characterized in that: S1: Cellulose derivative is added to silk fibroin salt solutions with different molecular weights (preferably with silk fibroin concentration of 30mg / ml - 200mg / ml) for swelling to obtain a solution with swelling completed; the salt solution of narrowly distributed controllable high molecular weight silk fibroin refers to the number average molecular weight (preferably measured by rheological method) of 10kDa - 80kDa, 80kDa - 100kDa, 100kDa - 120kDa, 120kDa - 160kDa, 160kDa - 200kDa, >200kDa; preferably the silk fibroin concentration in the silk fibroin salt solution is 30mg / ml - 200mg / ml; the salt solution preferably also includes lithium bromide; S2: The solution after swelling is filled into a dialysis bag with a specific shape and size, and is placed in deionized water for desalination and formation of gel; S3: The formed gel is placed in a constant temperature and humidity environment and slowly left standing for drying and shaping to obtain a silk fibroin profile, and the profile is preferably a hard profile.

3. The preparation method according to claim 1, characterized in that, In step S1, by mass ratio, silk fibroin:cellulose derivative = 6 - 12: 0.2 - 1.5, the swelling environment is 2 - 8°C, the swelling time is 24 - 72h, where the silk fibroin salt solution is a silk fibroin solution without desalination and purification, one or more of cellulose derivatives Ⅰ, and specific examples are as follows: Ⅰ: Cellulose derivative, preferably selected from one or more of carboxyl cellulose, alkyl cellulose or hydroxy cellulose, more preferably one or more of sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose.

4. The preparation method according to claim 1, characterized in that, In step S2, after complete swelling, the dialysis bag is placed in deionized water for desalination for 48 - 96h, where the deionized water is replaced every 1 hour until the solution in the dialysis bag is dialyzed to a gel state, and the shape of the dialysis bag can be one or more of spherical, cylindrical, elliptical.

5. The preparation method according to claim 1, characterized in that, In step S3, the environment for drying and shaping is that the constant temperature value in a constant temperature and humidity box is 20 - 60°C, and the humidity is 20%RH - 40%RH.

6. A silk fibroin profile with controllable molecular weight, characterized in that: Prepared by the preparation method according to any one of claims 1 - 5.

7. The profile according to claim 6, characterized in that: Its Young's modulus is 800 - 1200 MPa, preferably 1000 - 1200 MPa, and its density is 0.9 - 1.1 g / cm 3 .

8. The profile according to one of claims 6-7, characterized in that: It does not include any physical crosslinking agent and chemical crosslinking agent, preferably does not adopt any crosslinking method for crosslinking, more preferably does not include any other auxiliary agent, and most preferably consists of silk fibroin and cellulose derivative.

9. A silk fibroin profile with controllable molecular weight, characterized in that, It includes silk fibroin and cellulose derivative, preferably does not include any physical crosslinking agent and chemical crosslinking agent, further preferably does not adopt any crosslinking method for crosslinking, more preferably does not include any other auxiliary agent, and most preferably consists of silk fibroin and cellulose derivative, and the cellulose derivative is selected from one or more of carboxyl cellulose, alkyl cellulose or hydroxy cellulose, more preferably one or more of sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose; Furthermore, the Young's modulus of the profile is 800 - 1200 MPa, preferably 1000 - 1200 MPa, and its density is 0.9 - 1.1 g / cm 3 .

10. Use of a silk fibroin profile with controllable molecular weight prepared by the preparation method according to any one of claims 1-5 or a silk fibroin profile with controllable molecular weight according to any one of claims 6-9, characterized in that, The uses include: preparing materials in the field of biomedicine, preferably the prepared materials in the field of biomedicine are used for bone repair materials, surgical sutures, tissue engineering scaffolds and degradable packaging materials.

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