Elastic strain induction fibroin scaffold and preparation method thereof

Abstract

The invention discloses a preparation method of an elastic strain induction fibroin scaffold, and belongs to the technical field of materials of surgical supplies. The preparation method comprises the following steps: S1, preparing a spinning solution of silk fibroin and ethylene glycol diglycidyl ether, and carrying out electrostatic spinning to prepare an SF-EGDE-based fiber membrane; the mass ratio of the silk fibroin to the ethylene glycol diglycidyl ether is (8-20): 1; s2, the SF-EGDE based fiber membrane is subjected to dopamine hydrochloride modification, and an SE-PDA sample is obtained; s3, silver nitrate is attached to the SE-PDA sample, and the elastic strain induction fibroin scaffold SE-PDA-Ag is obtained. The elastic strain sensing fibroin scaffold has excellent wet elasticity, outstanding conductivity, excellent strain sensing performance and good antibacterial performance.

Description

Technical Field

[0001] The present invention relates to an elastic strain-sensing silk fibroin scaffold and a preparation method thereof, belonging to the technical field of materials for surgical supplies. Background Art

[0002] Currently, wound management faces severe challenges. Poor healing of skin wounds may be caused by factors such as excessive area or depth, complex tissue damage, and metabolic diseases, leading to infection, aggravating the injury, and even causing death. As an emerging method for skin reconstruction, tissue engineering promotes cell attachment, migration, proliferation, and differentiation by electrospun scaffolds simulating the microenvironment of the extracellular matrix, providing strong support for the formation of new tissues. However, during the wound healing process, if severe deformation cannot be detected in a timely manner, it may cause secondary injuries. Traditional strain sensors are mostly installed on one side of the wound, which may cause damage to fragile tissues or collect inaccurate signals. Therefore, developing a strain-sensing tissue engineering scaffold with both tissue repair function and motion tracking ability is a key requirement for in-situ skin reconstruction.

[0003] The development of intelligent wound dressings aims to achieve in-situ sensing of skin wounds, usually by combining conductive hydrogels, thin films, sponges, or ultrafine fibers, and collaborating with biomarkers such as pH value, temperature, uric acid, and glucose to collect wound state data or accelerate healing. However, most existing flexible electronic devices are only used as dressings and have low sensitivity. Tissue engineering scaffolds have attracted much attention because they can mimic the physical structure and chemical composition of the extracellular matrix. In particular, protein-based ultrafine fiber scaffolds are widely favored due to their biocompatibility, biodegradability, bioactivity, and high permeability. However, their development still faces many challenges. First, the scaffold needs to have high wet elasticity within a wide stretching range. Second, the scaffold needs to have both flexibility and permeability to ensure good contact with tissues and material transport, avoiding the use of rigid inorganic circuits. Third, the signal conduction path of the scaffold needs to have high electrical conductivity and maintain low resistance for a sufficient time to match the tissue regeneration rate. Meeting these requirements simultaneously is a major problem currently faced. Summary of the Invention

[0004] The present invention provides an elastic strain-sensing silk fibroin scaffold and a preparation method thereof, which can effectively solve the above problems.

[0005] A preparation method of an elastic strain-sensing silk fibroin scaffold includes the following steps: S1, preparing a spinning solution of silk fibroin and ethylene glycol diglycidyl ether, and performing electrospinning to prepare an SF-EGDE-based fiber membrane; the mass ratio of the silk fibroin to the ethylene glycol diglycidyl ether is 8-20:1; S2. Immerse the SF-EGDE-based fibrous membrane in the hydrochloric acid dopamine solution and modify it at 28 - 35 °C for 12 - 24 h to form a PDA layer, obtaining the SE-PDA sample; S3. Attach silver nitrate to the SE-PDA sample to obtain the elastic strain-sensing silk fibroin scaffold SE-PDA-Ag.

[0006] In some embodiments, in step S1, the solvent for preparing the spinning solution of silk fibroin and ethylene glycol diglycidyl ether is formic acid.

[0007] In some embodiments, in step S1, the conditions for preparing the spinning solution of silk fibroin and ethylene glycol diglycidyl ether are: stir at 900 - 1100 r / min for 10 - 14 h at room temperature.

[0008] In some embodiments, in step S1, the parameters of the electrospinning are: the liquid flow rate is 2.5 - 6 μL / min, the voltage is 10 - 20 kV, and the humidity is 70 - 80%.

[0009] In some embodiments, the concentration of the hydrochloric acid dopamine solution is 0.01 - 0.1 g / mL, and the pH is 8.0 - 9.0.

[0010] In some embodiments, in step S3, the specific steps for attaching silver nitrate to the SE-PDA sample are: soak the SE-PDA sample in the AgNO3 / PVP solution for 0.4 - 0.6 h, then add the reducing agent L-ascorbic acid to reduce Ag, and after reacting at room temperature for 50 - 70 min, the elastic strain-sensing silk fibroin scaffold SE-PDA-Ag is obtained.

[0011] In some embodiments, the concentration of Ag ions in the AgNO3 / PVP solution is 0.2 - 0.4 mol / L, and the concentration of PVP is 0.45 - 0.55 wt%.

[0012] In some embodiments, in step S3, it further includes soaking the SE-PDA-Ag in PBS for 2 - 4 days.

[0013] In some embodiments, the concentration of L-ascorbic acid used is 0.1 - 0.2 mol / L.

[0014] An elastic strain-sensing silk fibroin scaffold prepared by the above method.

[0015] The beneficial effects of the present invention are: In the present invention, ethylene glycol diglycidyl ether is introduced into silk fibroin, and first, an electrospinning process is used to prepare a fiber substrate. Subsequently, the prepared fiber substrate is subjected to hydrochloric acid dopamine modification treatment to enhance its surface activity. Then, the modified fiber is immersed in a mixed solution of silver nitrate and polyvinylpyrrolidone to ensure the uniform distribution of silver ions. Then, L-ascorbic acid is used as a reducing agent to reduce Ag + in the solution to silver nanoparticles. During this process, a nucleophilic reaction occurs between the amino group in silk fibroin and the epoxy group on ethylene glycol diglycidyl ether, resulting in the fiber substrate becoming brittle to a certain extent. However, when this fiber substrate is placed in a phosphate buffer solution (PBS), its tensile properties in the wet state exhibit significantly excellent characteristics. Thanks to the excellent adhesion performance of hydrochloric acid dopamine, the silver nanoparticles obtained by reducing with L-ascorbic acid can firmly adhere to the fiber surface, forming a uniform silver nano-coating. This method finally successfully prepares a silk fibroin scaffold with high elastic strain, which not only has good electrical conductivity and antibacterial properties, but also verifies its effective monitoring ability in a dynamic environment by detecting the change of resistance under different modes of movement. This innovative method provides a new type of scaffold material with multiple functions for the biomedical field and has broad application prospects. Brief Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a flowchart for preparing an elastic strain-sensitive silk scaffold according to an embodiment of the present invention.

[0018] Figure 2 It is a scanning electron microscope image and diameter distribution analysis diagram of fiber membranes of different ratios of SF / EGDE electrospun at different rotation speeds.

[0019] Figure 3 It is a stress-strain curve of fiber membranes of different ratios of SF / EGDE electrospun at different rotation speeds: (a) 300 r / min; (b) 1000 r / min.

[0020] Figure 4 It is a scanning electron microscope image of fiber membranes of SE-67 and scaffolds deposited with Ag modified by DA for 0 h, 4 h, 8 h, 12 h, 16 h, and 24 h.

[0021] Figure 5Stress-strain diagrams of the SE-PDA-Ag scaffolds modified with DA at different times.

[0022] Figure 6 X-ray diffraction pattern of the SE-PDA-Ag scaffold modified with DA for 12 h.

[0023] Figure 7 Silver content (a), resistivity (b), and conductivity (c) of the elastic strain-sensing silk scaffolds modified with DA for different durations.

[0024] Figure 8 Effect of DA treatment time on the elastic strain-sensing silk scaffolds. (a) Effect of DA treatment time on the relative resistance change and applied strain; (b) Effect of DA treatment time on the strain sensitivity.

[0025] Figure 9 Relative resistance change diagrams of the elastic strain-sensing silk scaffolds for inward or outward bending and 8 cycles of cyclic bending on each side. (a) Relative resistance change of the scaffold for inward or outward bending; (b) Relative resistance change for 8 cycles of cyclic bending on each side (chord length change: 25 mm). Inset: Schematic diagrams of the bending mode and chord length.

[0026] Figure 10 Digital images of the strain-sensing tests for different modes of movement cycles. (a) Fingers bent at different angles; (b) Wrist bent at 45°; (c) Elbow bent at 90°.

[0027] Figure 11 Antibacterial property diagrams of the elastic strain-sensing silk scaffolds. (a) Antibacterial experiment diagrams of the scaffolds with different concentrations against Escherichia coli and Staphylococcus aureus; (b) Inhibition zone; (c) Statistical chart of the inhibition rate. Detailed implementation manners

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention.

[0029] An embodiment of the present invention provides a method for preparing an elastic strain-sensing silk fibroin scaffold, which method includes the following detailed steps: First, in step S1, a mixed spinning solution of silk fibroin and ethylene glycol diglycidyl ether is prepared. Specifically, the mass ratio of silk fibroin to ethylene glycol diglycidyl ether is controlled within the range of 8 to 20:1. Then, using electrospinning technology, the prepared spinning solution is subjected to electrospinning treatment to finally prepare an SF-EGDE-based fiber membrane. Next, in step S2, the SF-EGDE-based fiber membrane is immersed in a hydrochloric acid dopamine solution and modified at 28 to 35 °C for 12 to 24 h to form a PDA layer. Through this step, the prepared SF-EGDE-based fiber membrane is chemically modified with hydrochloric acid dopamine to obtain an SE-PDA sample. Finally, in step S3, the SE-PDA sample is further processed to attach silver nitrate to its surface, thereby obtaining the elastic strain-sensing silk fibroin scaffold SE-PDA-Ag.

[0030] In the specific operation process, first, ethylene glycol diglycidyl ether is introduced into silk fibroin, and a fiber substrate is prepared through an electrospinning process. Subsequently, the fiber substrate is modified with hydrochloric acid dopamine to improve its surface activity. Then, the modified fiber is immersed in a mixed solution of silver nitrate and polyvinylpyrrolidone, and a reduction reaction is carried out using L-ascorbic acid. In this process, a nucleophilic reaction occurs between the amino group in silk fibroin and the epoxy group on ethylene glycol diglycidyl ether. Although this reaction makes the fiber relatively fragile, when the fiber substrate is placed in a phosphate buffer solution (PBS), its wet tensile properties are excellent. In addition, due to the excellent adhesion of hydrochloric acid dopamine, the silver nanoparticles obtained by reducing Ag + can be very effectively attached to the fiber surface.

[0031] Through the above method, a silk fibroin scaffold with both good elastic strain characteristics, excellent electrical conductivity and antibacterial properties has been successfully prepared. Further, by detecting the resistance change of the scaffold under different modes of movement, its effective monitoring ability in a dynamic environment has been verified.

[0032] It is worth mentioning that silk fibroin itself has good biocompatibility, programmable degradation performance, excellent mechanical properties and good processability, and can promote tissue repair and regeneration. The electrospinning process has the advantages of simple device, convenient operation and high production efficiency. The fiber substrate prepared by this technology has a large specific surface area, which is extremely beneficial for the attachment of silver nanoparticles. Based on this fiber substrate, with polydopamine as the adhesion layer and silver as the conductive layer, the finally prepared silk fibroin-based conductive scaffold not only has excellent performance, but is also very suitable as an ideal material for wound monitoring and has broad application prospects.

[0033] In some specific embodiments, during the operation of step S1, the solvent used to prepare the spinning solution by mixing silk fibroin and ethylene glycol diglycidyl ether is selected as formic acid. This solvent selection is based on its good solubility in silk fibroin and ethylene glycol diglycidyl ether, which can ensure the uniformity and stability of the spinning solution.

[0034] Similarly, in some specific embodiments, during the operation of step S1, the specific conditions for preparing the spinning solution by mixing silk fibroin and ethylene glycol diglycidyl ether are set as follows: under room temperature environment, stirring is carried out at a rotation speed of 900 - 1100 r / min for a duration of 10 - 14 h. Within this specific rotation speed range, the spinning solution can not only exhibit smooth and uniform morphological characteristics, but also possess optimal wet ductility. This excellent performance is mainly attributed to the action of a high shear force field, which can effectively promote the orientation arrangement of molecular chains and effectively inhibit possible structural defects. Based on these remarkable advantages, this spinning solution is selected as the base material for the subsequent preparation of the conductive scaffold to ensure the structural stability and functionality of the final product.

[0035] In some specific embodiments, the electrospinning process parameters involved in step S1 are specifically set as follows: the flow rate range of the liquid is precisely controlled between 2.5 - 6 μL / min to ensure the stability of the electrospinning process and the uniformity of the fibers; the applied voltage is maintained within the range of 10 - 20 kV to provide sufficient electric field strength to drive the ejection of the liquid and the formation of the fibers; in addition, the environmental humidity is also strictly controlled within the range of 70% - 80% to optimize the fiber deposition and drying process, thereby obtaining high-quality electrospinning products.

[0036] In some specific implementation cases, the operation process of modifying the SF-EGDE-based fiber membrane with dopamine hydrochloride is described in detail as follows: First, the SF-EGDE-based fiber membrane is completely immersed in the pre-prepared dopamine hydrochloride solution, and then the whole system is placed in an environment with a temperature controlled at 28-35 °C for a modification treatment lasting for 12-24 h. This process aims to form a uniform polydopamine (PDA) layer on the surface of the fiber membrane. When the modification time reaches the critical point of 12 h, silver nanoparticles can achieve uniform monodisperse distribution on the fiber surface, and then form a dense and continuous metallized coating. However, if the polymerization time of dopamine hydrochloride is further extended beyond 12 h, due to the continuous increase in the internal crosslinking degree of the PDA layer, a gradient change in the pore structure inside the fiber membrane will be triggered. This gradient change will drive the silver nanoparticle coating to penetrate deep into the fiber and cause secondary aggregation during this process, ultimately forming a silver-polydopamine composite system with a three-dimensional gradient structure. This experimental result clearly shows that the polymerization time of dopamine hydrochloride can directly and significantly affect the nucleation mechanism during silver deposition and the spatial distribution behavior of silver particles by regulating the chemical adhesion characteristics of the PDA layer. As the immersion time of the fiber membrane in the dopamine hydrochloride solution continues to extend, the mass of silver attached to the surface of the fiber membrane will gradually increase, thereby causing a significant improvement in the electrical conductivity of the fiber membrane.

[0037] In some specific embodiments, the concentration of the mentioned dopamine hydrochloride solution is set to 0.01-0.1 g / mL, and this concentration is formulated to ensure its effectiveness and stability in applications. At the same time, the pH value of the solution is strictly controlled within the range of 8.0-9.0. This pH range not only helps to maintain the chemical stability of the solution but also ensures its compatibility and safety in the body, thus achieving the best effect in various experiments and applications.

[0038] In some specific embodiments, the specific operation steps of attaching silver nitrate to the SE-PDA sample involved in step S3 are as follows: First, the SE-PDA sample is completely immersed in the pre-prepared AgNO3 / PVP solution for 0.4-0.6 h to ensure that the sample fully absorbs the effective components in the solution. Subsequently, the reducing agent L-ascorbic acid is added dropwise to this solution to initiate the reduction reaction of Ag ions. At room temperature, let this reaction continue for 50-70 min to ensure the sufficiency and stability of the reduction reaction. After the above steps of treatment, the required elastic strain-sensing silk fibroin scaffold SE-PDA-Ag can be obtained.

[0039] In some embodiments, the specific ratio of the AgNO3 / PVP solution used is as follows: the concentration of Ag ions is maintained between 0.2 and 0.4 mol / L, while the concentration of PVP is controlled within the range of 0.45 to 0.55 wt%. This precise concentration ratio not only ensures the high-purity deposition of metallic silver but also significantly improves the comprehensive properties of the material. The high-purity metallic silver structure not only endows the material with excellent antibacterial properties, effectively inhibiting the growth and reproduction of bacteria, but also successfully avoids the cytotoxicity risk that may be caused by by-products such as silver oxide, thus providing key quality assurance for the wide application of this material in the biomedical field and ensuring its safety and reliability in practical applications.

[0040] In some specific embodiments, the concentration of L-ascorbic acid used is set within a specific range, that is, between 0.1 mol / L and 0.2 mol / L. This concentration selection is based on a detailed analysis and optimization of experimental results to ensure that L-ascorbic acid can exert its best efficacy during the reaction while avoiding adverse effects caused by too high or too low concentrations.

[0041] The embodiments provided by the present invention describe in detail a unique preparation method by which an elastic strain-sensing silk fibroin scaffold with excellent properties can be successfully prepared. This scaffold not only exhibits high structural stability and elasticity but also can effectively sense and respond to externally applied strain forces in practical applications, thus demonstrating its broad application prospects in the fields of biomedicine, materials science, etc. The specific steps and parameter settings of this method are elaborated in detail in the embodiments to ensure that readers can accurately understand and replicate this technology.

[0042] Example 1 As Figure 1 shown, the preparation method of the elastic strain-sensing silk fibroin scaffold is as follows: (1) Preparation of a silk fibroin fiber substrate by electrospinning: Using formic acid as a solvent, a 10 wt% silk fibroin / ethylene glycol diglycidyl ether (SE) spinning solution is prepared and stirred at a speed of 300 r / min for 12 hours at room temperature to ensure complete dissolution of the silk fibroin powder. Then, at room temperature, electrospinning is carried out at a voltage of 15 kV and a flow rate of 5 μL / min. By adjusting the rotation speed of different receiving rollers, the humidity is controlled at 70 - 80%. Among them, the amounts of SF and EGDE and the sample names of the fiber substrates are shown in Table 1. For example, SE-67 represents the fiber membrane formed from the spinning solution prepared with 1.125 g of SF and 67 μL of EGDE (mass ratio 8.6:1) at a roller rotation speed of 1000 r / min.

[0043] (2) Preparation of elastic strain-sensing silk scaffolds: Immerse the SF-EGDE-based fiber membranes in a 0.02 g / mL hydrochloric acid dopamine (DA) treatment solution (pH 8.5) and perform modification treatments for different times (0 h, 4 h, 8 h, 12 h, 16 h, 24 h) at 30 °C to form a polydopamine (PDA) layer (the samples modified with DA are denoted as SE-PDA). Subsequently, immerse the DA-treated materials in an AgNO3 / PVP solution (Ag + 0.3 mol / L, PVP 0.5 wt%, calculated based on the weight of the Ag precursor solution) for 0.5 h, and then add a reducing agent, L-ascorbic acid (0.18 mol / L), for Ag reduction. After reacting at room temperature for 1 h, thoroughly rinse the obtained Ag-coated conductive scaffolds and immerse them in a phosphate buffer solution (PBS) for 3 days to finally obtain the scaffolds SE-PDA-Ag.

[0044] Table 1

[0045] Morphological characterization of composite fiber membranes with different ratios (SF / EGDE) and rotational speeds was carried out using a scanning electron microscope. Meanwhile, fiber membrane strips (30 mm × 5 mm) soaked in PBS were stretched at a tensile rate of 10 mm / s. By analyzing the effects of the SF / EGDE ratio and spinning speed on the morphology, diameter distribution ( Figure 2 ), and wet mechanical properties ( Figure 3 ) of the composite fiber membranes, the optimal substrate for the conductive scaffolds was screened.

[0046] As Figure 2 shows, in a low rotational speed (300 r / min) system, as the EGDE concentration increased from 45 μL to 270 μL, the macroscopic morphology gradually evolved from a uniform film layer (371.6 ± 42.3 nm) to a fiber adhesion defect structure. Microscopic observations showed that the fiber diameter decreased significantly by 38.8% with increasing concentration, and the full width at half maximum of the diameter distribution expanded by 85.5%, which was attributed to phase separation caused by excessive crosslinking when the concentration exceeded 180 μL. As Figure 3 shows, the wet mechanical test results indicated that the elongation at break of the low rotational speed fiber membranes showed a trend of first increasing and then decreasing with the EGDE concentration (SE-45-300: 51.77%, SE-90-300: 81.27%, SE-180-300: 2.994%), among which SE-90-300 had the best comprehensive performance, but SE-270 could not be tested due to structural embrittlement.

[0047] As Figure 2 and Figure 3It can be seen that in the high-speed rotation (1000 r / min) system, the fibers all form continuous and smooth film layers (without adhesion defects). The micro-homogeneity of SE-90-1000 is the best (diameter 450.9±51.6 nm, full width at half maximum 69.3 nm), but its mechanical properties decrease with the increase of EGDE concentration (SE-67-1000: 104.3%, SE-90-1000: 85.28%, SE-112-1000: 48.14%). Comparing samples with the same concentration (such as SE-90) at different rotation speeds, the fiber diameter at high speed increases by 51.1%, the elongation at break slightly increases, and reducing the EGDE concentration can further increase the elongation by 28%.

[0048] Considering both the morphology and mechanical properties, the high-speed and low-concentration sample SE-67-1000 has both a smooth and uniform morphology (diameter 685.9±113.4 nm) and the best wet ductility (104.3%). Its structural stability is attributed to the high shear force field promoting molecular chain orientation and suppressing defects, so it is selected as the substrate for the subsequent preparation of the conductive scaffold.

[0049] In Figure 4 the scanning electron microscope images of the fiber substrates and scaffolds modified with DA for different times and the deposited Ag are shown. From Figure 4 it can be seen that only a small amount of dispersed silver particles are adsorbed on the surface of the silk fibroin fiber scaffold without DA polymerization modification. After 4 hours of DA modification, the silver deposition rate is significantly increased, but due to the discontinuous coverage of the PDA layer, heterogeneous nucleation and growth competition of silver ions occur at limited active sites, resulting in polydispersity of silver particles and accompanied by local abnormal aggregation. When the DA polymerization time is extended to 8 hours, the PDA layer forms a uniform functionalized interface, and its rich catechol groups efficiently capture silver ions through electrostatic interaction and stabilize the reduction products, promoting the increase of the silver nanoparticle coverage and the uniform distribution of particle sizes. As the modification time reaches 12 hours, the silver nanoparticles achieve monodisperse distribution on the fiber surface, forming a dense and continuous metallized coating. However, further extending the DA polymerization time (more than 12 hours) will cause an internal pore gradient due to the increased crosslinking degree of the PDA layer, driving the deep penetration of the silver nanoparticle coating and secondary aggregation, and finally forming a silver-polydopamine composite system with a three-dimensional gradient structure. This result shows that the DA polymerization time directly affects the nucleation and particle spatial distribution behavior of silver deposition by regulating the chemical adhesion properties of the PDA layer.

[0050] Tensile tests were carried out on the scaffolds modified with DA for different times at a tensile rate of 10 mm / s, and the stress-strain diagrams are as Figure 5 shown. From Figure 5It can be seen that, compared with the 104% elongation at break of the SE fiber substrate, the elongation at break of the scaffold is basically maintained at about 84%. Specifically, the elongation at break of SE-PDA-Ag-12h and SE-PDA-Ag-16h is not much different, being 96.3% and 93.2% respectively. However, the elongation at break of the scaffolds in each modification time period is lower than that of the pure SE fiber substrate, indicating that the reaction between PDA and silk fibroin is equivalent to increasing the crosslinking degree of the scaffold substrate, resulting in a decrease in the elongation at break of the scaffold.

[0051] The characterization results based on X-ray diffraction are as Figure 6 shown. As Figure 6 can be seen, the silver nanoparticles exhibit typical face-centered cubic crystal structure characteristics on the surface of the scaffold. Its Bragg diffraction peaks (2θ = 38.0°, 44.2°, 64.4°, 77.4°, 81.6°) correspond to the (111), (200), (220), (311), (222) crystal plane families of the space group Fm-3m silver crystal in turn. The diffraction peak positions are in strict agreement with the standard data of the silver crystal phase, confirming that silver exists stably in the elemental metal state. No parasitic peaks with intensities exceeding 5% of the main peak were detected in the spectrum. This high-purity silver metal structure not only endows the material with excellent antibacterial properties but also avoids the cytotoxicity risk that may be caused by by-products such as silver oxide, providing a key quality guarantee for biomedical applications.

[0052] The amount of silver deposited on the scaffold per unit area was calculated by measuring the percentage increase in the fiber mass before and after silver attachment, as Figure 7 shown in (a). After the scaffold was soaked in the DA solution for different times (0h, 4h, 8h, 12h, 16h, and 24h), the mass change of silver was measured. The four-probe method was used to measure the resistance per unit distance of the fiber substrate after silver deposition, and the corresponding resistivity and conductivity are shown in (b) and (c) of Figure 7 respectively. The mass of silver on the scaffold without DA modification is the lowest, being 0.74 mg / cm 2 , forming a high resistance of 3.45 kΩ·cm, which is mainly due to the small and uneven distribution of silver particles on SE-PDA-Ag-0h, resulting in a poor conduction path. After 4h of modification, the silver mass of the scaffold increased significantly to 1.49 mg / cm 2 , and the resistivity was 2.68 kΩ·cm, although the resistivity still showed high non-uniformity. As the soaking time was further extended, the mass of attached silver gradually increased. When modified for 12h, the silver mass of the scaffold reached 2.23 mg / cm 2, the resistivity drops to 38 Ω·cm, with the highest conductivity of 0.12 s / cm. Continuing to extend the soaking time, silver particles mainly adhere large silver particles on the already formed uniform silver layer, and the mass increases significantly. However, due to the weak adhesion of large silver particles, the silver mass of the scaffolds modified for 16 h and 24 h has little difference, and the resistivity and conductivity basically remain at the same level.

[0053] To meet the monitoring requirements for excessive deformation caused by mechanical loads (such as impact, wear, tear, and tension) during tissue reconstruction, the conductive scaffolds SE-PDA-Ag modified with DA for different times (12 h, 16 h, and 24 h) were pre-wetted in PBS for 30 min and then clamped on a tensile scaffold controller equipped with a digital multimeter. During the test, the samples were continuously immersed in a PBS bath, the strain-relative resistance change of the scaffolds was recorded, the strain sensing characteristics of the conductive silver-coated scaffolds (SE-PDA-Ag) in PBS were analyzed, the sensitivity of the conductive scaffolds was calculated, and their resistance response mechanism was revealed. The test results are as Figure 8 shown, where (a) shows the effect of DA treatment time on the relative resistance change and applied strain; (b) shows the effect of DA treatment time on the strain sensitivity. As Figure 8 can be seen, under uniaxial tensile conditions, the relative resistance change (ΔR / R0) shows exponential growth, which is attributed to the synergistic effect of fiber orientation rearrangement and silver layer crack propagation: the initial low-sensitivity region (L region, strain < 20%) is dominated by the transformation of the fiber random state to an ordered arrangement, and the reconfiguration of the conduction path makes ΔR / R0 rise slowly; in the medium-sensitivity region (M region), the acceleration of crack propagation due to the high orientation of the fibers leads to an increase in resistance change; in the high-sensitivity region (H region), the resistance increases sharply due to the complete rupture of the cracks. By evaluating the effect of DA modification time through the sensitivity factor (GF = (ΔR / R0) / ε), it is found that the SE-PDA-Ag-12h scaffold, due to its uniform silver layer structure, exhibits a narrow L region (GF = 2.04) and a wide H region, and its sensitivity is significantly better than that of other treatment durations (such as long-term DA modification resulting in a wide L / M region and a decrease in sensitivity). Considering the strain thresholds of biological tissues (such as fingertip skin < 20%, tendon 10%), in low-strain monitoring scenarios, it is recommended to use scaffolds treated with 12 h DA, whose high-sensitivity region covers the key physiological strain range (10 - 40%), enabling real-time resistance signal warning and providing a technical basis for accurately identifying tissue excessive deformation.

[0054] The TH2822 source meter was used to record the relative resistance change (chord length change: 25 mm) of the conductive scaffold modified with DA for 12 h (abbreviated as SE-PDA-Ag-12) when bending inward or outward and unidirectional cyclic bending for 8 cycles, and the results are as Figure 9As shown, where (a) is the relative resistance change of the stent bending inward or outward; (b) is the relative resistance change of 8 cycles of cyclic bending on each side (chord length change: 25 mm); Insert: Schematic diagram of the bending mode and chord length. From Figure 9 It can be seen that the bending sensing performance of the conductive stent shows significant regularity. When the chord length gradually decreases from 30 mm to 5 mm, the resistance value of the stent significantly decreases in the inward bending state; while in the outward bending, the resistance significantly increases. The reason is that inward bending causes an in-plane compression effect on the sensing layer, resulting in a reduction in fiber spacing and enhanced conductivity, and the resistance decreases accordingly; on the contrary, outward bending causes the stent to experience in-plane stretching, reducing the conductive area and increasing the resistance. By alternately performing inward and outward bending tests, the generation of bidirectional differential repetitive signals can be observed, which further verifies the ability of the stent to monitor complex movements.

[0055] Since the highly elastic stent has been proven to maintain sensitivity within a wide range of stretching, its ability to track movements in vitro was studied in more depth. As Figure 10 shown, are the strain sensing test results of different mode movement cycles, where (a) is different finger bending angles; (b) is a 45° wrist bend; (c) is a 90° elbow bend. From Figure 10 It can be seen that when performing periodic flexion and extension tests from 30° to 90° at physiologically relevant frequencies, the stent shows a high angular resolution for the dynamic angular changes of the finger, wrist, and elbow, and its normalized resistance change exhibits excellent signal stability and repeatability.

[0056] As Figure 11 shown, are the test results of the antibacterial performance of the stent in vitro, where (a) and (b) respectively show the antibacterial effects of the plate counting method and the inhibition zone method, and the antibacterial rate statistics are shown in (c). From Figure 11 the analysis of (a) and (c) in it, it can be seen that the inhibition rates of the stent at 10 mg / mL, 20 mg / mL, and 30 mg / mL against Escherichia coli are 60.4%, 67.4%, and 100% respectively; the inhibition rates against Staphylococcus aureus are 40.8%, 60.2%, and 92.4% respectively. Obviously, the inhibition effect of the stent on Escherichia coli is better than that on Staphylococcus aureus. In particular, the 30 mg / mL stent can completely inhibit the growth of Escherichia coli, and the inhibition rate against Staphylococcus aureus is also as high as 92%. From Figure 11An obvious antibacterial zone can be observed in (c). After measurement, the widths of the antibacterial zones of the scaffold against Escherichia coli and Staphylococcus aureus on the agar plate are 2.725 mm and 2.857 mm respectively, and the antibacterial degrees of the two are not very different. Generally speaking, the scaffold exhibits good antibacterial properties, and the results obtained by the two testing methods are basically the same. The antibacterial laws of the scaffold against Escherichia coli and Staphylococcus aureus are also basically consistent.

[0057] The present invention integrates many advantages: the preparation process is simple, the cost is low, it has excellent wet elasticity, excellent electrical conductivity, excellent strain sensing performance and good antibacterial properties. The conductive scaffold developed by the present invention has successfully realized the real-time monitoring of the dynamic strain response of the skin. We firmly believe that the silk fibroin scaffold prepared in this invention will provide a strong reference for the progress of intelligent diagnosis and treatment technologies.

[0058] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of an elastic strain-sensing silk fibroin scaffold, characterized in that, It includes the following steps: S1. Prepare a spinning solution of silk fibroin and ethylene glycol diglycidyl ether, and perform electrospinning to prepare an SF-EGDE-based fiber membrane; the mass ratio of silk fibroin to ethylene glycol diglycidyl ether is 8-20:

1. S2. Immerse the SF-EGDE-based fiber membrane in a hydrochloric acid dopamine solution and modify it at 28-35 °C for 12-24 h to form a PDA layer, obtaining an SE-PDA sample. S3. Attach silver nitrate to the SE-PDA sample to obtain the elastic strain-sensing silk scaffold SE-PDA-Ag.

2. The preparation method of the elastic strain-sensing silk fibroin scaffold according to claim 1, wherein In step S1, the solvent for preparing the spinning solution of silk fibroin and ethylene glycol diglycidyl ether is formic acid.

3. The preparation method of the elastic strain-sensing silk fibroin scaffold according to claim 1, characterized in that, In step S1, the conditions for preparing the spinning solution of silk fibroin and ethylene glycol diglycidyl ether are: stirring at 900-1100 r / min for 10-14 h at room temperature.

4. The preparation method of the elastic strain-sensing silk fibroin scaffold according to claim 1, wherein In step S1, the parameters of the electrospinning are: the liquid flow rate is 2.5-6 μL / min, the voltage is 10-20 kV, and the humidity is 70-80%.

5. The preparation method of the elastic strain-sensing silk fibroin scaffold according to claim 1, wherein, The concentration of the hydrochloric acid dopamine solution is 0.01-0.1 g / mL, and the pH is 8.0-9.

0.

6. The preparation method of the elastic strain-sensing silk fibroin scaffold according to claim 1, characterized in that, In step S3, the specific steps for attaching silver nitrate to the SE-PDA sample are: immerse the SE-PDA sample in an AgNO3 / PVP solution for 0.4-0.6 h, then add a reducing agent L-ascorbic acid to perform Ag reduction, and after reacting at room temperature for 50-70 min, the elastic strain-sensing silk scaffold SE-PDA-Ag is obtained.

7. The preparation method of the elastic strain-sensing silk fibroin scaffold according to claim 6, wherein, The Ag ion concentration in the AgNO3 / PVP solution is 0.2-0.4 mol / L, and the concentration of PVP is 0.45-0.55 wt%.

8. The preparation method of the elastic strain-sensing silk fibroin scaffold according to claim 6, characterized in that, In step S3, it also includes immersing SE-PDA-Ag in PBS for 2-4 days.

9. The preparation method of the elastic strain-sensing silk fibroin scaffold according to claim 6, wherein, The usage concentration of the L-ascorbic acid is 0.1-0.2 mol / L.

10. An elastic strain-sensing silk scaffold prepared by the method according to any one of claims 1 to 9.

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