Elastic strain sensing silk fibroin scaffold and preparation method thereof

Abstract

The present invention discloses a method for preparing an elastic strain-sensing silk fibroin scaffold, belonging to the technical field of materials for surgical products. The preparation method comprises 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 ethylene glycol diglycidyl ether is 8-20:1; S2, modifying the SF-EGDE-based fiber membrane with dopamine hydrochloride to obtain an SE-PDA sample; S3, attaching silver nitrate to the SE-PDA sample to obtain the elastic strain-sensing silk fibroin scaffold SE-PDA-Ag. The elastic strain-sensing silk fibroin scaffold has excellent wet elasticity, outstanding electrical conductivity, excellent strain sensing performance, and good antibacterial properties.

Description

Technical Field

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

[0002] At present, wound management faces severe challenges. Poor skin wound healing may be caused by factors such as excessive area or depth, complex tissue damage, metabolic diseases, etc., which may lead to infection, aggravate the injury, and even cause death. Tissue engineering, as an emerging skin reconstruction method, simulates the microenvironment of the extracellular matrix through electrospun scaffolds, promotes cell attachment, migration, proliferation and differentiation, and provides strong support for the formation of new tissue. However, during the wound healing process, if severe deformation cannot be detected in time, secondary damage may occur. Traditional strain sensors are mostly installed on one side of the wound, which may cause damage to fragile tissues or collect inaccurate signals. Therefore, the development of strain-sensing tissue engineering scaffolds that have both tissue repair functions and motion tracking capabilities is a key requirement for achieving in situ skin reconstruction.

[0003] The development of smart wound dressings aims to enable on-site sensing of skin wounds. These typically incorporate conductive hydrogels, films, sponges, or microfibers, and collaborate with biomarkers such as pH, temperature, uric acid, and glucose to collect data on wound status or accelerate healing. However, existing flexible electronic devices are mostly used solely as dressings and have low sensitivity. Tissue engineering scaffolds have attracted considerable attention due to their ability to mimic the physical structure and chemical composition of the extracellular matrix. Protein-based microfiber scaffolds, in particular, are highly favored for their biocompatibility, degradability, bioactivity, and high permeability. However, their development still faces numerous challenges. First, scaffolds must exhibit high wet elasticity over a wide stretch range. Second, they must be both flexible and permeable to ensure good contact with tissue and material transfer, avoiding the use of rigid inorganic circuits. Third, the signal conduction pathways within the scaffolds must exhibit high electrical conductivity and maintain low resistance for a sufficient period of time to match the rate of tissue regeneration. Meeting these requirements simultaneously presents a significant challenge. 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 method for preparing an elastic strain-sensing silk fibroin scaffold comprises the following steps:

[0006] S1, preparing a spinning solution of silk fibroin and ethylene glycol diglycidyl ether, and performing electrospinning to prepare a SF-EGDE-based fiber membrane; the mass ratio of the silk fibroin to ethylene glycol diglycidyl ether is 8-20:1;

[0007] S2, immersing the SF-EGDE-based fiber membrane in a dopamine hydrochloride solution and modifying it at 28-35°C for 12-24 h to form a PDA layer to obtain a SE-PDA sample;

[0008] S3, attaching silver nitrate to the SE-PDA sample to obtain the elastic strain sensing silk scaffold SE-PDA-Ag.

[0009] In some embodiments, in step S1 , the solvent for preparing the spinning solution of silk fibroin and ethylene glycol diglycidyl ether is formic acid.

[0010] In some embodiments, in step S1 , the spinning solution of silk fibroin and ethylene glycol diglycidyl ether is prepared under the following conditions: stirring at 900-1100 rpm for 10-14 hours at room temperature.

[0011] In some embodiments, in step S1, the electrospinning parameters are: liquid flow rate of 2.5-6 μL / min, voltage of 10-20 kV, and humidity of 70-80%.

[0012] In some embodiments, the concentration of the dopamine hydrochloride solution is 0.01-0.1 g / mL and the pH is 8.0-9.0.

[0013] In some embodiments, in step S3, the specific steps of attaching silver nitrate to the SE-PDA sample are: soaking the SE-PDA sample in AgNO3 / PVP solution for 0.4~0.6h, then adding the reducing agent L-ascorbic acid to reduce Ag, and reacting at room temperature for 50~70min to obtain the elastic strain sensing silk scaffold SE-PDA-Ag.

[0014] In some embodiments, the Ag ion concentration in the AgNO 3 / PVP solution is 0.2-0.4 mol / L, and the PVP concentration is 0.45-0.55 wt %.

[0015] In some embodiments, step S3 further includes soaking the SE-PDA-Ag in PBS for 2 to 4 days.

[0016] In some embodiments, the L-ascorbic acid is used at a concentration of 0.1-0.2 mol / L.

[0017] An elastic strain sensing silk fibroin scaffold prepared by the method.

[0018] The beneficial effects of the present invention are:

[0019] The present invention introduces ethylene glycol diglycidyl ether into silk fibroin and first uses an electrospinning process to prepare a fiber substrate. Subsequently, the prepared fiber substrate is modified with dopamine hydrochloride to enhance its surface activity. Next, the modified fiber is immersed in a mixed solution of silver nitrate and polyvinyl pyrrolidone to ensure uniform distribution of silver ions. Then, L-ascorbic acid is used as a reducing agent to reduce the Ag in the solution. + Reduced to silver nanoparticles. During this process, the amino groups in the silk fibroin undergo a nucleophilic reaction with the epoxy groups on ethylene glycol diglycidyl ether, causing the fiber substrate to become 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 show significantly excellent characteristics. Thanks to the excellent adhesion properties of dopamine hydrochloride, the silver nanoparticles obtained by L-ascorbic acid reduction can be firmly attached to the fiber surface to form a uniform silver nanocoating. This method ultimately successfully prepared a silk fibroin scaffold with high elastic strain. This scaffold not only has good electrical conductivity and antibacterial properties, but also verifies its effective monitoring ability in dynamic environments by detecting the changes in resistance under different modes of movement. This innovative method provides a new scaffold material with multiple functions in the biomedical field and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is a flow chart for preparing the elastic strain-sensitive silk fibroin scaffold according to an embodiment of the present invention.

[0022] Figure 2 Scanning electron microscope images and diameter distribution analysis diagrams of fiber membranes with different ratios of SF / EGDE electrospun at different rotation speeds.

[0023] Figure 3 Stress-strain curves of fiber membranes with different ratios of SF / EGDE electrospun at different rotation speeds: (a) 300 r / min; (b) 1000 r / min.

[0024] Figure 4 Scanning electron microscopy images of SE-67 fiber membranes and Ag-deposited scaffolds modified with DA for 0h, 4h, 8h, 12h, 16h and 24h.

[0025] Figure 5The stress-strain diagrams of the SE-PDA-Ag scaffold modified with DA for different times.

[0026] Figure 6 Figure 2 is the X-ray diffraction pattern of the SE-PDA-Ag scaffold modified with DA for 12 h.

[0027] Figure 7 Silver content (a), resistivity (b), and conductivity (c) on DA-modified elastic strain-sensing silk scaffolds at different durations.

[0028] Figure 8 Figure 3. Effects of DA treatment time on elastic strain-sensing silk scaffolds. (a) Effect of DA treatment time on relative resistance change versus applied strain; (b) Effect of DA treatment time on strain sensitivity.

[0029] Figure 9 Figure 3. Relative resistance changes of an elastic strain-sensing silk scaffold during inward or outward bending and after eight cycles of cyclic bending. (a) Relative resistance change of the scaffold during inward or outward bending; (b) Relative resistance change after eight cycles of cyclic bending (chord length variation: 25 mm). Inset: Schematic diagram of bending mode and chord length.

[0030] Figure 10 Digital images of strain sensing tests during different motion cycles: (a) fingers bent at different angles; (b) wrist bent at 45°; (c) elbow bent at 90°.

[0031] Figure 11 Figure 2 shows the antibacterial performance of the elastic strain-sensing silk scaffold. (a) Antibacterial test of different concentrations of the scaffold against Escherichia coli and Staphylococcus aureus; (b) Inhibition zones; (c) Inhibition rate statistics. DETAILED DESCRIPTION

[0032] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection 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 invention claimed for protection, but merely represents selected embodiments of the present invention.

[0033] An embodiment of the present invention provides a method for preparing an elastic strain sensing silk fibroin scaffold, which includes the following detailed steps: first, in step S1, a mixed spinning solution of silk fibroin and ethylene glycol diglycidyl ether in a certain proportion is prepared, specifically, the mass ratio of silk fibroin to ethylene glycol diglycidyl ether is controlled within the range of 8 to 20:1, and then the prepared spinning solution is spun using electrospinning technology to finally prepare an SF-EGDE-based fiber membrane; then, in step S2, the SF-EGDE-based fiber membrane is immersed in a dopamine hydrochloride solution and modified at 28 to 35°C for 12 to 24 hours to form a PDA layer. Through this step, the prepared SF-EGDE-based fiber membrane is chemically modified with dopamine hydrochloride to obtain an SE-PDA sample; finally, in step S3, the SE-PDA sample is further treated so that silver nitrate adheres to its surface, thereby obtaining the elastic strain sensing silk fibroin scaffold SE-PDA-Ag.

[0034] During the specific operation, ethylene glycol diglycidyl ether is first introduced into silk fibroin, and a fiber base is prepared by an electrospinning process. The fiber base is then modified with dopamine hydrochloride to increase its surface activity. Afterwards, the modified fiber is immersed in a mixed solution of silver nitrate and polyvinyl pyrrolidone, and then reduced using L-ascorbic acid. In this process, the amino groups in the silk fibroin react with the epoxy groups on ethylene glycol diglycidyl ether to form a nucleophilic reaction. Although this reaction makes the fiber relatively fragile, when the fiber base is placed in a phosphate buffer solution (PBS), its wet tensile properties are excellent. In addition, due to the excellent adhesion of dopamine hydrochloride, the reduction of Ag by L-ascorbic acid + The resulting silver nanoparticles are able to attach to the fiber surface very effectively.

[0035] Using this method, a silk fibroin scaffold with excellent elastic strain characteristics, electrical conductivity, and antibacterial properties was successfully fabricated. Furthermore, by measuring the changes in the scaffold's resistance under different motion patterns, the scaffold's effective monitoring capabilities in dynamic environments were verified.

[0036] It is worth mentioning that silk fibroin itself has good biocompatibility, programmable degradation properties, excellent mechanical properties and good processability, and can promote tissue repair and regeneration. The electrospinning process has the advantages of simple equipment, convenient operation and high production efficiency. The fiber substrate prepared using this technology has a large specific surface area, which is extremely beneficial for the attachment of silver nanoparticles. Based on this fiber substrate, polydopamine is used as the adhesion layer and silver is used as the conductive layer. The silk fibroin-based conductive scaffold is finally prepared. It not only has excellent performance, but is also very suitable as an ideal material for wound monitoring and has broad application prospects.

[0037] In some specific embodiments, during the operation of step S1, formic acid is selected as the solvent used to prepare the spinning solution formed by mixing silk fibroin and ethylene glycol diglycidyl ether. This solvent is selected based on its good solubility for silk fibroin and ethylene glycol diglycidyl ether, which can ensure the uniformity and stability of the spinning solution.

[0038] Also in some specific embodiments, during the operation of step S1, the specific conditions for preparing the spinning solution formed by mixing silk fibroin and ethylene glycol diglycidyl ether are set to: stirring at a speed of 900~1100r / min at room temperature for 10~14h. Within this specific speed range, the spinning solution can not only present smooth and uniform morphological characteristics, but also have optimal wet ductility. This excellent performance is mainly attributed to the effect of the high shear force field, which can effectively promote the orientation of the molecular chains and effectively suppress possible structural defects. It is based on these significant advantages that the 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.

[0039] In some specific embodiments, the electrospinning process parameters involved in step S1 are set in detail as follows: the flow rate range of the liquid is precisely controlled between 2.5 and 6 μL / min to ensure the stability of the spinning process and the uniformity of the fiber; the applied voltage is maintained in the range of 10 to 20 kV to provide sufficient electric field strength to drive the liquid jetting and fiber formation; in addition, the humidity of the environment is also strictly controlled in the range of 70% to 80% to optimize the fiber deposition and drying process, thereby obtaining high-quality electrospun products.

[0040] In some specific implementations, the process for modifying the SF-EGDE-based fiber membrane with dopamine hydrochloride, as described in step S2, is described in detail as follows: First, the SF-EGDE-based fiber membrane is completely immersed in a pre-prepared dopamine hydrochloride solution. The entire system is then placed in an environment controlled at a temperature of 28-35°C for a duration of 12-24 hours. This modification process aims to form a uniform polydopamine (PDA) layer on the fiber membrane surface. When the modification time reaches the critical point of 12 hours, the silver nanoparticles achieve a uniform, monodispersed distribution on the fiber surface, forming a dense and continuous metallized coating. However, if the dopamine hydrochloride polymerization time is extended beyond 12 hours, the increasing cross-linking degree within the PDA layer will trigger a gradient change in the pore structure of the fiber membrane. This gradient change drives the silver nanoparticle coating to penetrate deeper into the fiber layers, where secondary aggregation occurs, ultimately forming a silver-polydopamine composite system with a three-dimensional gradient structure. This experimental result clearly demonstrates that the polymerization time of dopamine hydrochloride, by regulating the chemical adhesion properties of the PDA layer, can directly and significantly influence the nucleation mechanism and spatial distribution of silver particles during silver deposition. As the fiber membrane is immersed in the dopamine hydrochloride solution for a longer time, the mass of silver attached to the fiber membrane surface gradually increases, significantly improving the conductive properties of the fiber membrane.

[0041] In some specific embodiments, the concentration of the dopamine hydrochloride solution is set at 0.01-0.1 g / mL, a concentration that is formulated to ensure its effectiveness and stability in applications. Furthermore, the pH value of the solution is strictly controlled within the range of 8.0-9.0. This pH range not only helps maintain the solution's chemical stability but also ensures its compatibility and safety in vivo, thereby achieving optimal results in various experiments and applications.

[0042] In some specific embodiments, the specific steps involved in attaching silver nitrate to the SE-PDA sample in step S3 are as follows: First, the SE-PDA sample is completely immersed in a pre-prepared AgNO3 / PVP solution for a period of 0.4 to 0.6 hours to ensure that the sample fully absorbs the active ingredients in the solution. Subsequently, the reducing agent L-ascorbic acid is added dropwise to the solution to initiate the reduction reaction of the Ag ions. This reaction is allowed to proceed at room temperature for 50 to 70 minutes to ensure the sufficiency and stability of the reduction reaction. After completing the above steps, the desired elastic strain-sensing silk fibroin scaffold SE-PDA-Ag is obtained.

[0043] In some embodiments, the specific ratio of the AgNO3 / PVP solution used is: the concentration of Ag ions is maintained between 0.2 and 0.4 mol / L, while the concentration of PVP is controlled in 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 overall performance of the material. The high-purity metallic silver structure not only gives the material excellent antibacterial properties, effectively inhibiting the growth and reproduction of bacteria, but also successfully avoids the risk of cytotoxicity that may be caused by by-products such as silver oxide, thereby providing key quality assurance for the wide application of this material in the biomedical field, ensuring its safety and reliability in practical applications.

[0044] In some specific embodiments, the L-ascorbic acid concentration is set within a specific range, i.e., from 0.1 mol / L to 0.2 mol / L. This concentration is selected based on careful analysis and optimization of experimental results to ensure that L-ascorbic acid can achieve optimal performance during the reaction while avoiding the adverse effects of excessively high or low concentrations.

[0045] The examples provided herein describe in detail a unique preparation method that successfully fabricates an elastic, strain-sensing silk fibroin scaffold with excellent performance. This scaffold not only exhibits high structural stability and elasticity but also effectively senses and responds to externally applied strain, demonstrating broad application prospects in fields such as biomedicine and materials science. The specific steps and parameter settings of this method are fully explained in the examples to ensure that readers can accurately understand and replicate the technology.

[0046] Example 1

[0047] like Figure 1 As shown, the preparation method of the elastic strain sensing silk fibroin scaffold is as follows:

[0048] (1) Preparation of silk fiber substrate by electrospinning: A 10 wt% silk fibroin / ethylene glycol diglycidyl ether (SE) spinning solution was prepared using formic acid as solvent and stirred at 300 r / min at room temperature for 12 hours to ensure that the silk fibroin powder was completely dissolved. Then, electrospinning was performed at room temperature using a voltage of 15 kV and a flow rate of 5 μL / min. The humidity was controlled at 70-80% by adjusting the speed of different receiving rollers. The amount of SF and EGDE used and the sample name of the fiber substrate are shown in Table 1. For example, SE-67 represents a fiber membrane formed by using a spinning solution prepared with 1.125 g SF and 67 μL EGDE (mass ratio of 8.6:1) at a roller speed of 1000 r / min.

[0049] (2) Preparation of elastic strain-sensing silk scaffolds: The SF-EGDE-based fiber membrane was immersed in a 0.02 g / mL dopamine hydrochloride (DA) treatment solution (pH 8.5) and subjected to modification treatment at 30°C for different times (0 h, 4 h, 8 h, 12 h, 16 h, 24 h) to form a polydopamine (PDA) layer (the sample modified with DA is represented by SE-PDA). Subsequently, the DA-treated material was immersed in a AgNO3 / PVP solution (Ag + The Ag precursor solution was incubated in a 5% ethanol solution (0.3 mol / L, 0.5 wt% PVP, calculated based on the weight of the Ag precursor solution) for 0.5 hour. Then, the reducing agent L-ascorbic acid (0.18 mol / L) was added dropwise for Ag reduction. After reacting for 1 hour at room temperature, the resulting Ag-coated conductive scaffold was thoroughly rinsed and immersed in phosphate buffered saline (PBS) for 3 days to obtain the SE-PDA-Ag scaffold.

[0050] Table 1

[0051]

[0052] The morphology of the composite fiber membranes with different ratios (SF / EGDE) and spinning speeds was characterized by scanning electron microscopy. At the same time, the fiber membrane specimens (30mm×5mm) soaked in PBS were stretched at a stretching rate of 10mm / s. The effects of SF / EGDE ratio and spinning speed on the morphology and diameter distribution of the composite fiber membranes were analyzed. Figure 2 ) and wet mechanical properties ( Figure 3 ) to screen out the optimal substrate for the conductive support.

[0053] Depend on Figure 2 It can be seen that in the low-speed (300r / min) system, as the EGDE concentration increased from 45μL to 270μL, the macroscopic morphology gradually evolved from a uniform film layer (371.6±42.3nm) to a fiber adhesion defect structure. Microscopic observation showed that the fiber diameter decreased significantly by 38.8% with increasing concentration, and the half-peak width of the diameter distribution expanded by 85.5%, which was attributed to phase separation caused by excessive cross-linking when the concentration exceeded 180μL. Figure 3 As shown in the figure, the wet mechanical test results show that the elongation at break of the low-speed fiber membrane first increases and then decreases with the EGDE concentration (SE-45-300: 51.77%, SE-90-300: 81.27%, SE-180-300: 2.994%), among which SE-90-300 has the best comprehensive performance, but SE-270 cannot be tested due to its brittle structure.

[0054] Depend on Figure 2 and Figure 3As can be seen, at a high rotation speed (1000 r / min), the fibers formed a continuous, smooth film layer (without adhesion defects). SE-90-1000 exhibited the best microscopic uniformity (diameter 450.9±51.6 nm, full width at half maximum 69.3 nm), but mechanical properties decreased with increasing EGDE concentration (SE-67-1000: 104.3%, SE-90-1000: 85.28%, SE-112-1000: 48.14%). Compared to samples with the same concentration (e.g., SE-90) but different rotation speeds, the high-speed fibers showed a 51.1% increase in diameter and a slight improvement in elongation at break. Lowering the EGDE concentration further increased the elongation by 28%.

[0055] Considering both morphology and mechanical properties, the high-speed, low-concentration sample SE-67-1000 exhibited 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 field promoting molecular chain orientation and suppressing defects, making it the preferred substrate for subsequent conductive scaffold fabrication.

[0056] exist Figure 4 The figure shows the SEM images of fiber substrates and scaffolds modified with DA for different times and the deposited Ag. Figure 4 Unmodified silk fibroin fiber scaffolds were found to harbor only a small amount of dispersed silver particles. However, after 4 hours of DA modification, the silver deposition rate significantly increased. However, due to discontinuous PDA coverage, heterogeneous nucleation and growth competition occurred between silver ions on limited active sites, resulting in polydispersity and localized agglomeration of silver particles. Extending the DA polymerization time to 8 hours formed a uniform functionalized interface, where the abundant catechol groups efficiently captured silver ions and stabilized the reduction products through electrostatic interactions, leading to increased silver nanoparticle coverage and a more uniform particle size distribution. With a modification time of 12 hours, silver nanoparticles achieved a monodisperse distribution on the fiber surface, forming a dense and continuous metallized coating. However, further extension of the DA polymerization time (exceeding 12 hours) resulted in an internal pore gradient due to increased crosslinking in the PDA layer, driving deep penetration of the silver nanoparticle coating and secondary aggregation, ultimately forming a silver-polydopamine composite with a three-dimensional gradient structure. These results indicate that DA polymerization time directly influences the nucleation and spatial distribution of silver nanoparticles by regulating the chemical adhesion properties of the PDA layer.

[0057] The scaffolds modified with DA for different times were subjected to tensile tests at a tensile rate of 10 mm / s. The stress-strain diagrams are shown in Figure 2. Figure 5 As shown. Figure 5As can be seen in the figure, the elongation at break of the scaffold remains roughly around 84%, compared to 104% for the SE fiber substrate. Specifically, the elongations at break of SE-PDA-Ag-12h and SE-PDA-Ag-16h are similar, at 96.3% and 93.2%, respectively. However, the elongation at break of the scaffolds at each modification time period is lower than that of the pure SE fiber substrate, indicating that the reaction between PDA and silk fibroin increases the cross-linking degree of the scaffold substrate, resulting in a decrease in the scaffold's elongation at break.

[0058] The characterization results based on X-ray diffraction are as follows Figure 6 As shown. Figure 6 It can be seen that the silver nanoparticles on the surface of the stent exhibit typical face-centered cubic crystal structure characteristics. Its Bragg diffraction peaks (2θ=38.0°, 44.2°, 64.4°, 77.4°, 81.6°) correspond to the (111), (200), (220), (311), and (222) crystal planes of the space group Fm-3m silver crystal, respectively. The diffraction peak positions strictly match the standard data of the silver crystal phase, confirming that the silver element exists stably in a single metallic state. No parasitic peaks with an intensity exceeding 5% of the main peak were detected in the spectrum. This high-purity metallic silver structure not only gives the material excellent antibacterial properties, but also avoids the risk of cytotoxicity caused by byproducts such as silver oxide, providing a key quality assurance for biomedical applications.

[0059] The amount of silver deposited on the scaffold per unit area was calculated by measuring the percentage increase in fiber mass before and after silver attachment, e.g. Figure 7 As shown in (a), the weight change of silver after the scaffold was immersed in DA solution for different times (0h, 4h, 8h, 12h, 16h and 24h). The resistance per unit distance after silver deposition on the fiber substrate was measured using the four-probe method. The corresponding resistivity and conductivity are shown as follows: Figure 7 As shown in (b) and (c), the silver mass on the scaffold without DA modification is the lowest, which is 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 conductive path. After 4h modification, the silver mass of the scaffold increased significantly to 1.49 mg / cm 2 The resistivity was 2.68 kΩ·cm, although the resistivity still showed high inhomogeneity. As the immersion time continued to increase, the quality of the attached silver gradually improved. After 12 hours of modification, the silver mass of the scaffold reached 2.23 mg / cm 2, the resistivity dropped to 38 Ω·cm, and the conductivity reached its highest point, 0.12 s / cm. With further extended immersion time, the silver particles primarily adhered to the already formed uniform silver layer, resulting in a significant mass increase. However, due to the weaker adhesion of large silver particles, the silver mass of the stents modified for 16 and 24 hours remained similar, and the resistivity and conductivity remained roughly the same.

[0060] In response to the need to monitor excessive deformation caused by mechanical loads (such as impact, wear, tear, and stretching) during tissue reconstruction, the conductive stent SE-PDA-Ag modified with DA for different times (12h, 16h, and 24h) was pre-soaked in PBS for 30 minutes and then clamped on a tensile stent controller equipped with a digital multimeter. During the test, the sample was immersed in the PBS bath, and the strain-relative resistance change of the stent was recorded. The strain sensing characteristics of the conductive silver-coated stent (SE-PDA-Ag) in PBS were analyzed, the sensitivity of the conductive stent was calculated, and its resistance response mechanism was revealed. The test results are as follows: Figure 8 As shown in the figure, (a) is the effect of DA treatment time on relative resistance change and applied strain; (b) is the effect of DA treatment time on strain sensitivity. Figure 8 Under uniaxial tension, the relative resistance change (ΔR / R0) increases exponentially, a phenomenon attributed to the synergistic effect of fiber orientation rearrangement and crack propagation in the silver layer. The initial low-sensitivity zone (L zone, strain <20%) is dominated by a transition from random fibers to ordered alignment, resulting in a slow increase in ΔR / R0 due to the reorganization of conductive pathways. In the medium-sensitive zone (M zone), crack propagation accelerates due to high fiber orientation, leading to a more pronounced resistance change. Finally, in the high-sensitivity zone (H zone), resistance increases dramatically due to complete crack rupture. The sensitivity factor (GF = (ΔR / R0) / ε) was used to evaluate the effect of DA modification time. The SE-PDA-Ag-12h scaffold exhibited a narrow L zone (GF = 2.04) and a wide H zone due to its uniform silver layer structure, demonstrating significantly better sensitivity than other treatment times (e.g., long DA modification times result in a wide L / M zone and decreased sensitivity). Combined with the strain threshold of biological tissue (such as fingertip skin <20%, tendon 10%), in low-strain monitoring scenarios, it is recommended to use a 12hDA-treated stent. Its high-sensitivity area covers the critical physiological strain range (10-40%), which can realize real-time resistance signal warning and provide a technical basis for accurately identifying excessive tissue deformation.

[0061] The relative resistance change (chord length change: 25 mm) of the conductive stent modified with DA for 12 hours (abbreviated as SE-PDA-Ag-12) during inward or outward bending and unilateral cyclic bending for 8 cycles was recorded using a Tonghui 1991 source meter. The results are shown in the figure. Figure 9As shown, (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: 25mm); Inset: Schematic diagram of bending mode and chord length. Figure 9 It can be seen that the bending sensing performance of the conductive stent shows significant regularity. When the chord length is gradually reduced from 30mm to 5mm, the resistance value of the stent in the inward bending state decreases significantly; while when it is bent outward, the resistance increases significantly. The reason is that inward bending causes the sensing layer to produce an in-plane compression effect, resulting in a decrease in fiber spacing, enhanced conductivity, and a corresponding decrease in resistance; conversely, outward bending causes the stent to undergo in-plane stretching, reducing the conductive area and increasing resistance. By alternating inward and outward bending tests, the generation of bidirectional differentiated repetitive signals can be observed, which further verifies the stent's ability to monitor complex movements.

[0062] Since the highly elastic scaffold has been shown to maintain sensitivity over a wide range of stretch, its motion tracking capability in vitro has been further investigated. Figure 10 The following are the strain sensing test results of different motion cycles, where (a) is the finger bending at different angles; (b) is the wrist bending at 45°; and (c) is the elbow bending at 90°. Figure 10 It can be seen that when performing periodic flexion and extension tests from 30° to 90° at physiologically relevant frequencies, the bracket exhibits high angular resolution for dynamic angle changes of the fingers, wrist and elbow, and its normalized resistance change shows excellent signal stability and repeatability.

[0063] like Figure 11 The following are the results of the in vitro antibacterial performance test of the stent, where (a) and (b) respectively show the bacterial inhibition effects of the plate count method and the inhibition zone method, and the inhibition rate statistics are shown in (c). Figure 11 From the analysis of (a) and (c), we can see that the inhibition rates of 10mg / mL, 20mg / mL, and 30mg / mL scaffolds against E. coli are 60.4%, 67.4%, and 100%, respectively; and the inhibition rates against Staphylococcus aureus are 40.8%, 60.2%, and 92.4%, respectively. Obviously, the scaffolds have a better inhibitory effect on E. coli than on Staphylococcus aureus. In particular, the 30mg / mL scaffold can completely inhibit the growth of E. coli, while the inhibition rate against Staphylococcus aureus is as high as 92%. Figure 11In (c), a clear zone of inhibition is observed. The widths of the zones of inhibition against Escherichia coli and Staphylococcus aureus on the agar plate were measured to be 2.725 mm and 2.857 mm, respectively, with similar inhibition levels. Overall, the scaffold exhibits excellent antibacterial properties, with the results from both test methods being largely consistent, and the antibacterial patterns of the scaffold against E. coli and Staphylococcus aureus also largely matching each other.

[0064] This invention combines numerous advantages: a simple preparation process, low cost, exceptional wet elasticity, excellent electrical conductivity, outstanding strain sensing performance, and favorable antibacterial properties. The conductive scaffold developed in this invention successfully enables real-time monitoring of the skin's dynamic strain response. We firmly believe that the silk fibroin fiber scaffold prepared in this invention will provide a powerful reference for the advancement of intelligent diagnostic and treatment technologies.

[0065] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing an elastic strain-sensing silk fibroin scaffold, characterized in that: The following steps are involved: 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 and ethylene glycol diglycidyl ether is 8-20:1; 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 hours at room temperature; in step S1, the parameters of the electrospinning are: liquid flow rate of 2.5-6 μL / min, voltage of 10-20 kV, and humidity of 70-80%; S2, immersing the SF-EGDE-based fiber membrane in a dopamine hydrochloride solution and modifying it at 28-35°C for 12-24 hours to form a PDA layer, thereby obtaining a SE-PDA sample; the dopamine hydrochloride solution has a concentration of 0.01-0.1 g / mL and a pH of 8.0-9.0; S3, attaching silver nitrate to the SE-PDA sample and reducing it, thereby obtaining the elastic strain sensing silk scaffold SE-PDA-Ag; The specific steps of step S3 are as follows: immersing the SE-PDA sample in an AgNO3 / PVP solution for 0.4-0.6 h, then adding a reducing agent L-ascorbic acid to reduce Ag, and reacting at room temperature for 50-70 min to obtain the elastic strain sensing silk scaffold SE-PDA-Ag; the Ag ion concentration in the AgNO3 / PVP solution is 0.2-0.4 mol / L, and the PVP concentration is 0.45-0.55 wt%; The step S3 further includes soaking the SE-PDA-Ag in PBS for 2 to 4 days.

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

3. The method for preparing the elastic strain-sensing silk fibroin scaffold according to claim 1, wherein: The L-ascorbic acid is used at a concentration of 0.1-0.2 mol / L.

4. An elastic strain-sensing silk fibroin scaffold prepared by the method according to any one of claims 1 to 3.

Images