Mechanical property controllable silk fibroin hard material, preparation method and application thereof

Abstract

This invention provides a rigid silk fibroin material with controllable mechanical properties, its preparation method, and its applications, belonging to the field of medical material preparation. The preparation method includes the following steps: a silk fibroin solution is subjected to low-temperature freezing and annealing to form a Silk I-type insoluble substance; after drying, it is pulverized and granulated to obtain regenerated silk fibroin powders of different particle sizes; subsequently, hot pressing is performed to obtain rigid silk fibroin materials with different mechanical properties. This invention uses hot pressing of Silk I-structured silk fibroin to replace the traditional hot pressing process of amorphous silk fibroin, avoiding the high energy consumption and time-consuming freeze-drying process; furthermore, this invention controls the particle size of the regenerated silk fibroin powder through granulation, achieving regulation of the mechanical properties of the rigid silk fibroin material to adapt to the mechanical properties required for repair materials in different application scenarios, and can be applied in orthopedics, tissue engineering, and other fields.

Description

Technical Field

[0001] This invention relates to the field of medical materials and medical devices, and in particular to a rigid silk fibroin material with controllable mechanical properties for orthopedic implantation and tissue repair, as well as its preparation method and application. Background Technology

[0002] Silk fibroin, a high-molecular-weight natural fibrous protein secreted by silkworms, possesses superior mechanical properties, controllable biodegradation rates, and high biocompatibility. Regenerated silk fibroin rigid materials, prepared through hot pressing using silk fibroin as a raw material, show great promise in fields such as tissue repair scaffolds, functional substance sustained-release carriers, and biodegradable bioplastics due to their excellent mechanical properties, biocompatibility, and controllable biodegradation rates.

[0003] In existing technologies, the hot pressing process for rigid regenerated silk fibroin materials requires first preparing the regenerated silk fibroin into an amorphous powder through freeze-drying. This powder is flocculent with random particle size, resulting in rigid silk fibroin materials with limited mechanical properties. The mechanical properties can only be altered by sacrificing the hot pressing temperature, which significantly reduces the molding efficiency. The key challenge limiting its industrialization is how to efficiently and cost-effectively dehydrate the regenerated silk fibroin solution to obtain regenerated silk fibroin powder and achieve controllable mechanical properties for rigid regenerated silk fibroin materials.

[0004] Patent CN117164885A discloses a method for controlling the moisture content of silk fibroin powder by regulating humidity, and then preparing a rigid silk fibroin material with controllable strength and toughness through a hot-pressing process. However, the silk fibroin powder in this technical solution is prepared by freeze-drying, which is energy-intensive, costly, and time-consuming. Furthermore, controlling the moisture content of amorphous freeze-dried silk fibroin powder is problematic because the powder absorbs moisture and denatures when dissolved in water, and controlling the moisture content after freeze-drying makes the preparation process more complicated. In addition, existing clinically used orthopedic implant materials (such as titanium alloy bone nails) have problems such as requiring secondary surgery for removal, mismatch with human bone mechanics, and the potential for inflammation from long-term placement; biodegradable materials (such as polylactic acid bone nails) have defects such as asynchronous degradation rate with bone healing and insufficient mechanical strength.

[0005] In view of this, it is necessary to design a simple process for preparing rigid silk fibroin materials that does not require secondary adjustment of powder moisture content and can achieve controllable mechanical properties according to actual application requirements, so as to solve the above problems. Summary of the Invention

[0006] To address the shortcomings of the existing technology, the present invention aims to provide a rigid silk fibroin material with controllable mechanical properties, its preparation method, and its applications. The present invention proposes a new principle and pathway for hot pressing processing of Silk I type silk fibroin.

[0007] This invention obtains insoluble silk fibroin with a Silk I structure through crystal form regulation, and then directly dehydrates and granulates it by room temperature drying or heated drying, avoiding the use of energy-intensive and time-consuming drying processes such as freeze drying and supercritical carbon dioxide. Subsequently, granulation is performed to obtain regenerated silk fibroin powder with the target particle size.

[0008] Unlike traditional methods of hot-pressing amorphous silk fibroin powder, this invention directly obtains a Silk I / Silk II hybrid rigid silk fibroin material by hot-pressing silk fibroin powder with a target particle size and Silk I structure. The resulting rigid silk fibroin material achieves a mechanical strength of 134.4 MPa and a toughness of 1.41 MJ / m. 3 It possesses excellent mechanical properties.

[0009] Furthermore, this invention can control the mechanical properties of rigid silk fibroin materials by adjusting the particle size of the regenerated silk fibroin powder, making it applicable to various mechanical performance requirements.

[0010] To achieve the above objectives, the present invention provides a method for preparing a mechanically controllable rigid silk fibroin material, comprising the following steps:

[0011] S1. The regenerated silk fibroin solution is frozen at a temperature below -10°C to obtain a regenerated silk fibroin coagulated block;

[0012] S2. Anneal the regenerated silk fibroin coagulated block to transform the silk fibroin structure into the Silk I structure, thus obtaining the Silk I type insoluble substance;

[0013] S3. The Silk I type insoluble material is pulverized to obtain regenerated silk fibroin powder; subsequently, the moisture content of the regenerated silk fibroin powder is adjusted to ≤30% by humidification or drying.

[0014] S4. The regenerated silk fibroin powder obtained in step S3 is granulated and sieved to obtain regenerated silk fibroin powder with the target particle size.

[0015] S5. Fill the mold with regenerated silk fibroin powder of the target particle size, perform hot pressing, then cool and demold to obtain a rigid silk fibroin material with controllable mechanical properties.

[0016] Furthermore, in step S4, the target particle size is 50-200 μm.

[0017] Further, in step S3, the moisture content of the regenerated silk fibroin powder is adjusted to 5-15%.

[0018] Furthermore, in step S1, the freezing temperature for the freezing treatment is -80℃ to -20℃, and the freezing time is 2-6 hours.

[0019] Furthermore, in step S2, the annealing temperature is above -10℃ and below 0℃; the annealing time is 12-96 h.

[0020] Furthermore, in step S4, the granulation method is ball milling or mechanical crushing.

[0021] When ball milling is used, the ball milling speed is 300 rpm to 500 rpm and the ball milling time is 5 min to 60 min.

[0022] Further, in step S5, inorganic substances are added and mixed with the regenerated silk fibroin powder, followed by hot pressing; the inorganic substances include at least one of hydroxyapatite, β-calcium phosphate, barium sulfate, and tricalcium phosphate.

[0023] The present invention also provides a rigid silk fibroin material with controllable mechanical properties, which is prepared by the preparation method described in any of the foregoing technical solutions; the rigid silk fibroin material has both Silk I and Silk II protein structures.

[0024] The rigid silk fibroin material prepared by the above technical solution can be applied to the fields of biomedical materials such as tissue repair scaffolds, functional substance sustained-release carriers, and orthopedic implants.

[0025] The beneficial effects of this invention are:

[0026] (1) In this invention, the silk fibroin solution is subjected to low-temperature freezing and annealing to form Silk I type insoluble matter, which is then dried and pulverized to produce regenerated silk fibroin powder. The powder is then granulated and sieved to obtain regenerated silk fibroin powder with the target particle size. Finally, the powder is hot-pressed to obtain silk fibroin hard material with the target mechanical properties.

[0027] This invention replaces the traditional hot pressing process of amorphous silk fibroin with hot pressing of Silk I structure silk fibroin, avoiding high-energy-consuming and time-consuming drying processes such as freeze drying and supercritical carbon dioxide. Furthermore, this invention achieves control over the particle size of silk fibroin powder through ball milling. It does not sacrifice other material properties and does not damage the original structure of the material, thus achieving mechanical control of rigid silk fibroin materials, which can be applied to different mechanical performance requirements.

[0028] (2) The preparation method provided by the present invention has a simple process flow and strong universality. Compared with the existing preparation technology, the freeze annealing process can achieve cost reduction and large-scale production. The obtained silk fibroin hard material has the characteristics of strong mechanical properties, controllable mechanical strength and toughness, excellent biocompatibility and degradability, and can be applied to actual clinical fields such as orthopedics and tissue engineering.

[0029] (3) The present invention can control the moisture content of silk fibroin powder by controlling the drying time, thereby achieving performance regulation of silk fibroin hard materials without the need for secondary moisture content regulation, which significantly reduces the energy and time costs in the preparation process of regenerated silk fibroin hard materials.

[0030] (4) This invention successfully prepared a rigid silk fibroin material with a mixed structure of silk I and silk II through a freeze-annealing process. This invention can also endow the material with clinical functions such as bone induction by adding medical-grade inorganic substances, adapting to the needs of medical devices in multiple scenarios such as orthopedics and tissue engineering. The process is simple and has strong universality. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0032] Figure 2 This is a photograph of the regenerated silk fibroin powder prepared in Example 1.

[0033] Figure 3 This is a particle size distribution diagram of the regenerated silk fibroin powder after ball milling in Example 1.

[0034] Figure 4 This is a scanning electron microscope (SEM) image of the regenerated silk fibroin powder after ball milling in Example 1.

[0035] Figure 5 The images show the XRD patterns of the silk I regenerated silk fibroin powder and the silk fibroin rigid material prepared in Example 1.

[0036] Figure 6 The image shows a physical picture of the regenerated silk fibroin rigid material prepared in Example 1, with a scale bar of 1 cm.

[0037] Figure 7 The image shows a scanning electron microscope (SEM) image of the cross-section of the regenerated silk fibroin rigid material prepared in Example 1, with a scale bar of 5 μm.

[0038] Figure 8 This is a schematic diagram of the process flow for Comparative Example 1.

[0039] Figure 9The images show the XRD patterns of the amorphous regenerated silk fibroin powder and the rigid silk fibroin material obtained after hot pressing in Comparative Example 1.

[0040] Figure 10 This is a particle size distribution diagram of the regenerated silk fibroin powder after ball milling in Example 2.

[0041] Figure 11 This is a scanning electron microscope (SEM) image of the regenerated silk fibroin powder after ball milling in Example 2.

[0042] Figure 12 This is a particle size distribution diagram of the regenerated silk fibroin powder after ball milling in Example 3.

[0043] Figure 13 This is a scanning electron microscope (SEM) image of the regenerated silk fibroin powder after ball milling in Example 3.

[0044] Figure 14 The image shows a physical picture of the regenerated silk fibroin rigid material prepared in Example 5, with a scale bar of 1 cm.

[0045] Figure 15 The image shows a physical picture of the regenerated silk fibroin rigid material prepared in Example 6, with a scale bar of 1 cm.

[0046] Figure 16 This is a photograph of the regenerated silk fibroin rigid material prepared in Comparative Example 2.

[0047] Figure 17 The image shows a physical picture of the regenerated silk fibroin rigid material prepared in Comparative Example 3, with a scale bar of 1 cm.

[0048] Figure 18 This is a photograph of the regenerated silk fibroin powder prepared in Comparative Example 4.

[0049] Figure 19 The image shows a physical picture of the regenerated silk fibroin rigid material prepared in Comparative Example 4. The scale bar is 1 cm.

[0050] Figure 20 The image shows a physical picture of the regenerated silk fibroin rigid material prepared in Example 7, with a scale bar of 1 cm. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0053] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0054] In existing technologies, silk fibroin coagulated blocks are mostly processed by freeze-drying and then ground to obtain silk fibroin powder. However, freeze-drying requires a long time and high energy consumption, and the low-temperature vacuum environment places high demands on the equipment, resulting in high process costs and low preparation efficiency. This bottleneck problem has led to practical issues of cost-effectiveness and large-scale production, resulting in a lack of market competitiveness.

[0055] This invention provides a method for preparing a rigid silk fibroin material with controllable mechanical properties, comprising the following steps:

[0056] S1. The regenerated silk fibroin solution is frozen at a temperature below -10°C to obtain a regenerated silk fibroin coagulated block;

[0057] Preferably, the freezing temperature for the freezing treatment is -80℃ to -20℃, and the freezing time is 2-6 hours.

[0058] S2. Anneal the regenerated silk fibroin coagulated block to transform the silk fibroin structure into a silk I structure, obtaining a silk I type insoluble substance; wherein, the annealing temperature is higher than the freezing temperature of step S1 but lower than 0°C.

[0059] Preferably, the annealing temperature is above -10°C and below 0°C; the annealing time is 12-96 h.

[0060] S3. Pulverize the insoluble silk type I material to obtain regenerated silk fibroin powder;

[0061] The moisture content of the regenerated silk fibroin powder is controlled by humidification or drying. In this invention, the moisture content of the regenerated silk fibroin powder is controlled to ≤30%, preferably 5-15%.

[0062] When adjusting the drying process, the drying temperature is 40-70℃ and the drying time is 10-40 min.

[0063] S4. Granulate and sieve the regenerated silk fibroin powder to obtain regenerated silk fibroin powder with the target particle size.

[0064] The granulation method is ball milling or mechanical crushing.

[0065] When using ball milling, the ball milling speed is 300-500 rpm and the ball milling time is 5-60 min.

[0066] The target particle size is 50-200 μm.

[0067] S5. Fill the mold with regenerated silk fibroin powder of the target particle size, perform hot pressing, then cool and demold to obtain a rigid silk fibroin material with controllable mechanical properties.

[0068] During hot pressing, the hot pressing temperature is 100-180℃ and the hot pressing pressure is greater than 100 MPa.

[0069] In step S5, inorganic substances may be added and mixed with regenerated silk fibroin powder, followed by hot pressing; wherein, the inorganic substances include at least one of hydroxyapatite, β-calcium phosphate, barium sulfate, and tricalcium phosphate.

[0070] The resulting rigid silk fibroin material possesses both Silk I and Silk II protein structures and exhibits excellent mechanical properties.

[0071] This mechanically controllable rigid silk fibroin material can be used as a medical device in orthopedic implants (bone nails, bone plates), tissue repair scaffolds (bone defect repair, skin regeneration scaffolds), and other fields such as orthopedics and tissue engineering.

[0072] The present invention will now be described in detail through specific embodiments.

[0073] Example 1

[0074] Please see Figure 1 As shown in the figure, this embodiment provides a method for preparing a rigid silk fibroin material with controllable mechanical properties, including the following steps:

[0075] S1. Place 100 g of raw silkworm silk into 5 L of sodium carbonate aqueous solutions with concentrations of 0.1 wt% and 0.05 wt%, respectively, and degumme them sequentially. Specifically, boil the silk twice in the 0.1 wt% sodium carbonate aqueous solution and once in the 0.05 wt% sodium carbonate aqueous solution, each boiling for 30 min. Afterward, thoroughly wash the degummed silk with deionized water, loosen it, and place it in an oven at 60 ± 5℃ for thorough drying.

[0076] The degummed silk was placed in a 9.3 mol / L lithium bromide solution at a bath ratio of 1:3 (g / ml) at 60℃ for 60 min. The solution was then placed in a dialysis bag and dialyzed in deionized water for 3 days. After dialysis, the solution was filtered through a gauze filter and centrifuged at 10,000 rpm for 10 min to obtain a regenerated silk fibroin solution with a mass fraction of 8 wt%. The solution was then frozen at -80℃ for 24 h to obtain a regenerated silk fibroin coagulated block.

[0077] S2. The regenerated silk fibroin coagulated block obtained in step S1 is placed in an environment with a temperature of -5℃ for annealing treatment to obtain regenerated silk fibroin insoluble matter.

[0078] S3. The obtained regenerated silk fibroin insoluble matter was added to a pulverizer and processed for 15 minutes at a pulverizer speed of 150 r / min. The moisture content was then controlled by monitoring its mass change during the drying process to obtain regenerated silk fibroin powder with a moisture content of 5%. A photograph of the powder is shown below. Figure 2 As shown.

[0079] S4. The regenerated silk fibroin powder was ball-milled to obtain regenerated silk fibroin powder with a particle size mainly of 50 μm. The particle size distribution is shown in the figure below. Figure 3 As shown, the electron microscope image is as follows: Figure 4 As shown. The ball milling speed was 400 rpm, and the ball milling time was 60 min.

[0080] S5. Add regenerated silk fibroin powder with a particle size of 50 μm to the mold, hot press for 30 min under a pressure of 240 MPa and a temperature of 150℃, then cool and demold to obtain a rigid silk fibroin material.

[0081] Depend on Figure 3 , Figure 4 It can be seen that the particle size of regenerated silk fibroin powder is mainly concentrated between 40 and 60 μm. Small particle size helps to improve interfacial fusion and fusion effect; and the sheet-like powder is easy to stack and fill the pores during hot pressing, which is more conducive to forming a tight interfacial bonding effect.

[0082] Figure 5 The image shows the XRD pattern of the regenerated silk fibroin powder and the hard silk fibroin material prepared in Example 1.

[0083] As can be seen, the silk fibroin powder exhibits diffraction peaks at 11.8°, 20.0°, and 28.2°, belonging to the Silk I conformation. The rigid silk fibroin material obtained after hot pressing exhibits diffraction peaks at 12.6° and 27.9°, belonging to the Silk I conformation; and diffraction peaks at 20.6° and 24.9°, belonging to the Silk II conformation. This indicates that the obtained rigid silk fibroin material is a mixed structure of Silk I and Silk II, with the Silk I structure being more prominent.

[0084] Figure 6 The image shows a physical picture of the regenerated silk fibroin rigid material prepared in Example 1. As can be seen from the image, the regenerated silk fibroin rigid material prepared under this process has a uniform appearance.

[0085] Figure 7 This is a scanning electron microscope image of the cross-section of the regenerated silk fibroin rigid material prepared in Example 1. It can be seen that the silk type I powder has fused together, and it is not simply powder densification, demonstrating that thermoplastic processing of silk fibroin powder can be achieved without the need for traditional hot pressing of amorphous powder structures.

[0086] Comparative Example 1

[0087] Please see Figure 8 As shown, Comparative Example 1 provides a traditional method for preparing a rigid silk fibroin material, comprising the following steps:

[0088] S1. Place 100 g of raw silkworm silk into 5 L of sodium carbonate aqueous solutions with concentrations of 0.1 wt% and 0.05 wt%, respectively, and degumme them sequentially. Specifically, boil the silk twice in the 0.1 wt% sodium carbonate aqueous solution and once in the 0.05 wt% sodium carbonate aqueous solution, each boiling for 30 min. Afterward, thoroughly wash the degummed silk with deionized water, loosen it, and place it in an oven at 60 ± 5℃ for thorough drying.

[0089] The degummed silk was placed in a 9.3 mol / L lithium bromide solution at a bath ratio of 1:3 (g / ml) at 60℃ for 60 min. The solution was then placed in a dialysis bag and dialyzed in deionized water for 3 days. After dialysis, the solution was filtered through a gauze filter and centrifuged at 10,000 rpm for 10 min to obtain an 8 wt% regenerated silk fibroin solution. This solution was diluted to obtain a 1 wt% regenerated silk fibroin solution, which was then frozen at -80℃ for 24 h to obtain a coagulated regenerated silk fibroin block.

[0090] S2. Place the regenerated silk fibroin coagulated block obtained in step S1 into a freeze dryer with a cold trap temperature of -80℃ for freeze drying to obtain a regenerated silk fibroin block with a water content of 0.

[0091] S3. The obtained regenerated silk fibroin block with a moisture content of 0 is added to a pulverizer and processed for 15 minutes at a pulverizer speed of 150 r / min. Then, the moisture content is adjusted twice to obtain regenerated silk fibroin powder with a moisture content of 5%.

[0092] S4. Add the regenerated silk fibroin powder into the mold, hot press it for 30 minutes under a pressure of 240 MPa and a temperature of 150℃, then cool it down and demold it to obtain the hard silk fibroin material.

[0093] Figure 9 The image shows the XRD patterns of the regenerated silk fibroin powder and the hard silk fibroin material prepared in Comparative Example 1.

[0094] As can be seen, the regenerated silk fibroin powder prepared by freeze-drying process does not show any significant characteristic peaks and belongs to an amorphous structure. However, the rigid silk fibroin material obtained after hot pressing shows diffraction peaks at 9.9°, 21.1°, and 24.8°, which belongs to the Silk II conformation, indicating that the prepared rigid silk fibroin material has a Silk II structure.

[0095] That is, in Comparative Example 1, the molecular chains are activated by hot pressing and arranged in an orderly manner, thereby achieving a conformational transformation and transforming them into a stable structure (Silk II structure).

[0096] Experimental results show that in Example 1, step S2, using annealing, consumes only 109.84 kW·h of electricity in the key process step of the preparation chain, with a processing time of 152 h. In contrast, in Comparative Example 1, using freeze-drying, the electricity consumption in the key process step of the preparation chain reaches as high as 14198.4 kW·h, with a processing time of 2088 h. This demonstrates a significant difference in energy consumption costs between the two processes. The annealing method used in this invention is significantly superior to existing freeze-drying processes in terms of both energy consumption and processing cycle, effectively reducing energy consumption and improving production efficiency.

[0097] Example 2

[0098] Compared with Example 1, the difference is that in step S4, the regenerated silk fibroin powder is ball-milled to obtain regenerated silk fibroin powder with a particle size distribution mostly in the range of 30-60 μm, as shown in the particle size distribution diagram below. Figure 10 As shown, the electron microscope image is as follows: Figure 11 As shown. Other aspects are largely the same as in Example 1, and will not be repeated here.

[0099] Example 3

[0100] Compared with Example 1, the difference is that in step S4, the regenerated silk fibroin powder is ball-milled to obtain regenerated silk fibroin powder with a particle size mainly of 80 μm, and its particle size distribution is shown in the figure. Figure 12 As shown, the electron microscope image is as follows: Figure 13 As shown. Other aspects are largely the same as in Example 1, and will not be repeated here.

[0101] Example 4

[0102] Compared with Example 1, the difference is that the ball milling process in step S4 was not performed, and the particle size of the resulting regenerated silk fibroin powder is mostly distributed in the range of 150-200 μm. Other aspects are largely the same as in Example 1 and will not be repeated here.

[0103] Three-point bending tests were conducted on the regenerated silk fibroin rigid materials prepared in Examples 1-4 and Comparative Example 1. The results are shown in Table 1.

[0104] Table 1

[0105] project Powder particle size (µm) Fracture strength (MPa) Toughness (MJ / m 3 ) Example 1 50 134.41 1.42 Example 2 30-60 117.57 1.13 Example 3 80 95.12 0.89 Comparative Example 1 200 81.32 0.58 Example 4 150-200 82.63 0.59

[0106] Comparing Example 4 with Comparative Example 1, it can be seen that under hot-pressing conditions at 150°C, the process employed in this invention, compared to the freeze-drying process in Comparative Example 1, can significantly reduce process costs while obtaining regenerated silk fibroin rigid materials with similar mechanical properties. This indicates that the process of this invention has significant practical implications for promoting the industrialization of regenerated silk fibroin rigid materials.

[0107] In this invention, ball milling is used to reduce the particle size of regenerated silk fibroin powder from predominantly 200 μm to predominantly 50 μm. This results in an increase in the tensile strength of the resulting hard silk fibroin material from 82.63 MPa to 134.41 MPa, and an increase in toughness from 0.59 MJ / m. 3 Increased to 1.42 MJ / m 3 It has excellent mechanical properties.

[0108] The rigid silk fibroin material prepared using the technical solution of this invention has good biocompatibility and excellent mechanical properties.

[0109] In practical applications, depending on actual needs, regenerated silk fibroin powders of different particle sizes can be obtained through ball milling to obtain hard silk fibroin materials with different mechanical properties, so as to meet the mechanical performance requirements of repair materials in different application scenarios.

[0110] Example 5

[0111] The difference from Example 1 is that in step S3, the moisture content of the regenerated silk fibroin powder is controlled to be 8%.

[0112] Experiments show that the regenerated silk fibroin rigid material prepared under this process has a uniform appearance and morphology, such as... Figure 14 As shown.

[0113] Example 6

[0114] The difference from Example 1 is that in step S3, the moisture content of the regenerated silk fibroin powder is controlled to be 30%.

[0115] Experiments show that the regenerated silk fibroin rigid material prepared under this process has a uniform appearance and morphology, such as... Figure 15 As shown.

[0116] Comparative Example 2

[0117] The difference compared to Example 1 is that in step S3, the moisture content of the regenerated silk fibroin powder is controlled to be 35%.

[0118] Experiments show that materials with excessively high moisture content cannot be hot-pressed, such as... Figure 16 As shown.

[0119] Comparative Example 3

[0120] The difference from Example 1 is that in step S3, the moisture content of the regenerated silk fibroin powder is controlled to be 0%.

[0121] Experiments show that at this moisture content, the material cannot be hot-pressed; it will break directly and exhibit very poor mechanical strength. Figure 17 As shown.

[0122] In the technical solution of the present invention, the moisture content of silk fibroin powder can be controlled by controlling the drying time in step S3, thereby achieving performance regulation of silk fibroin rigid material without the need for secondary moisture content regulation, which significantly reduces the energy and time costs in the preparation process of regenerated silk fibroin rigid material.

[0123] Experiments show that, in the technical solution of this invention, the moisture content should be less than or equal to 30% to obtain a uniform regenerated silk fibroin rigid material. The preferred moisture content is 5-15%. The mechanical properties of the material are optimal when the moisture content is 10%.

[0124] Comparative Example 4

[0125] A method for preparing a rigid silk fibroin material differs from Example 1 in that: the regenerated silk fibroin solution is directly dried at 90°C to obtain a regenerated silk fibroin film; then, the regenerated silk fibroin film is pulverized and ground into fine powder, as shown in the figure below. Figure 18 As shown; subsequently, the obtained powder is filled into a mold and hot-pressed to obtain a rigid silk fibroin material, as shown in the figure. Figure 19 As shown.

[0126] Experiments show that when regenerated silk fibroin membrane is ground into fine powder, the powder particle size is too large and the powder texture is rough and hard. Therefore, the hot pressing molding effect of the hard silk fibroin material is poor, and it is impossible to form a uniform hard silk fibroin material.

[0127] Example 7

[0128] A method for preparing a regenerated silk fibroin rigid material differs from Example 1 in that: in step S4, inorganic barium sulfate is added and mixed with the regenerated silk fibroin powder, wherein the amount of barium sulfate added is 10% of the total mass of the silk fibroin powder. The other steps are roughly the same as in Example 1 and will not be repeated here.

[0129] Figure 20 This is a photograph of the regenerated silk fibroin rigid material prepared in Example 7.

[0130] As can be seen, in this invention, the regenerated silk fibroin rigid material can be uniformly loaded with barium sulfate.

[0131] It should be noted that the inorganic material can also be any combination of one or more of hydroxyapatite, β-calcium phosphate, and tricalcium phosphate. Experiments have shown that when the amount of inorganic material added is 5-50% of the mass of silk fibroin powder, it can impart additional functionality to the prepared composite material while retaining excellent mechanical properties.

[0132] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a rigid silk fibroin material with controllable mechanical properties, characterized in that, Includes the following steps: S1. The regenerated silk fibroin solution is frozen at a temperature below -10°C to obtain a regenerated silk fibroin coagulated block; S2. Anneal the regenerated silk fibroin coagulated block to transform the silk fibroin structure into the Silk I structure, thus obtaining the Silk I type insoluble substance; S3. The Silk I type insoluble material is pulverized to obtain regenerated silk fibroin powder; subsequently, the moisture content of the regenerated silk fibroin powder is adjusted to ≤30% by humidification or drying. S4. The regenerated silk fibroin powder obtained in step S3 is granulated and sieved to obtain regenerated silk fibroin powder with the target particle size. S5. Fill the mold with regenerated silk fibroin powder of the target particle size, perform hot pressing, then cool and demold to obtain rigid silk fibroin material.

2. The method for preparing the mechanically controllable rigid silk fibroin material according to claim 1, characterized in that, In step S4, the target particle size is 50-200 μm.

3. The method for preparing the mechanically controllable rigid silk fibroin material according to claim 1, characterized in that, In step S3, the moisture content of the regenerated silk fibroin powder is adjusted to 5-15%.

4. The method for preparing the mechanically controllable rigid silk fibroin material according to claim 1, characterized in that, In step S1, the freezing temperature for the freezing treatment is -80℃ to -20℃, and the freezing time is 2-6 hours.

5. The method for preparing the mechanically controllable rigid silk fibroin material according to claim 1, characterized in that, In step S2, the annealing temperature is above -10℃ and below 0℃; the annealing time is 12-96 h.

6. The method for preparing the mechanically controllable rigid silk fibroin material according to claim 1, characterized in that, In step S4, the granulation method is ball milling; the ball milling speed is 300 rpm to 500 rpm, and the ball milling time is 5 min to 60 min.

7. The method for preparing the mechanically controllable rigid silk fibroin material according to claim 1, characterized in that, In step S5, inorganic substances are added and mixed with the regenerated silk fibroin powder, followed by hot pressing. The inorganic substances include at least one of hydroxyapatite, β-calcium phosphate, barium sulfate, and tricalcium phosphate.

8. A rigid silk fibroin material with controllable mechanical properties, characterized in that, The silk fibroin rigid material is prepared according to any one of claims 1-7, and possesses both Silk I and Silk II protein structures.

9. The application of the mechanically controllable rigid silk fibroin material as described in claim 8, characterized in that, The mechanically controllable silk fibroin rigid material is used to prepare orthopedic implants and tissue repair scaffolds.

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