A modified degradable fiber and a preparation method thereof

Abstract

The application discloses a modified degradable fiber and a preparation method thereof, and relates to the technical field of materials. The modified degradable fiber is prepared from the following components: a base material, a functional component, a pH-sensitive unit and a reinforcing agent. The preparation method comprises the following steps: modifying nanocellulose to obtain the base material; synthesizing the functional component; mixing the pH-sensitive unit and the base material to obtain a mixture A; mixing the reinforcing agent and the functional component to obtain a mixture B; mixing the mixture A and the mixture B to prepare a spinning solution; and preparing the modified degradable fiber by using a spinning process. The modified fiber provided by the application can dynamically adjust the degradation rate in different tissue microenvironments, meets the diversified clinical requirements of fast-healing tissues and deep tissues, and all the components are biodegradable materials, the degradation products are non-toxic, and the modified fiber is suitable for various surgical suture scenes.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials technology, and in particular to a modified biodegradable fiber and its preparation method. Background Technology

[0002] Biodegradable sutures are widely used in surgical procedures. They gradually degrade and are absorbed within the body, avoiding the need for secondary surgery for removal. These are sutures used to suture wounds caused by external injuries or injuries sustained during surgery. Absorbable sutures slowly integrate with the tissue after suturing, a process that does not affect normal wound healing. They degrade into soluble products within the body's tissues.

[0003] Existing biodegradable suture materials mainly include polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), and their copolymers. These materials degrade through hydrolysis or enzymatic degradation, but their degradation rates are usually fixed and difficult to adaptively adjust according to the dynamic needs of tissue healing. For example, rapidly healing skin tissue requires a shorter degradation cycle, while deeper tissues (such as tendons) require a longer degradation time.

[0004] In existing technologies, the degradation rate of a single material is insufficient to meet diverse clinical needs, and it also suffers from high brittleness and tensile strength that cannot meet the requirements of practical applications. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a modified biodegradable fiber and its preparation method, the specific technical solution of which is as follows:

[0006] A modified biodegradable fiber, by weight, comprises the following components: 30-60 parts of matrix material, 20-50 parts of functional component, 5-20 parts of pH-sensitive unit, and 5-20 parts of reinforcing agent;

[0007] The matrix material is selected from nanocellulose modified derivatives, the functional components are selected from polymers containing dynamic chemical bonds, the pH-sensitive unit is selected from chitosan or its modified derivatives, and the reinforcing agent is selected from biodegradable polyester.

[0008] Preferably:

[0009] The modified nanocellulose derivative is carboxylated nanocellulose;

[0010] The polymer containing dynamic chemical bonds is a self-healing polyurethane containing disulfide bonds;

[0011] The pH-sensitive unit is chitosan;

[0012] The biodegradable polyester is polylactic acid.

[0013] Preferably:

[0014] The modified nanocellulose derivative is carboxylated nanocellulose;

[0015] The polymer containing dynamic chemical bonds is a self-healing polyurethane containing disulfide bonds;

[0016] The pH-sensitive unit is graphene oxide grafted with chitosan;

[0017] The biodegradable polyester is polydioxanone.

[0018] Preferably, it also includes 1 to 10 parts of a synergist;

[0019] The modified nanocellulose derivative is carboxylated nanocellulose;

[0020] The polymer containing dynamic chemical bonds is a self-healing polyurethane containing disulfide bonds;

[0021] The pH-sensitive unit is chitosan modified with polyphosphocholine groups;

[0022] The biodegradable polyester is polydioxanone;

[0023] The synergist is graphene oxide.

[0024] The present invention also provides a preparation method for preparing modified biodegradable fibers as described in any one of the above claims, comprising the following steps:

[0025] a) Chemically modify nanocellulose to obtain a matrix material;

[0026] b) Synthesize polymers containing dynamic chemical bonds as functional components;

[0027] c) The pH-sensitive unit is mixed with the matrix material to obtain mixture A;

[0028] d) The reinforcing agent and functional components are mixed to obtain mixture B;

[0029] e) Mix mixture A with mixture B to prepare a spinning solution, and use a spinning process to prepare modified biodegradable fibers.

[0030] Preferably:

[0031] The specific steps of mixing the pH-sensitive unit with the matrix material in step c include: adding the pH-sensitive unit and the matrix material to a solvent, and stirring the composite solution by microwave heating for 1 to 3 hours, wherein the solvent is a mixture of DMF and water with a volume ratio of 7:3 to 8:2.

[0032] The mixing of the reinforcing agent and functional components in step d specifically includes: adding the reinforcing agent and functional components to DMF and stirring the composite solution at 60-70°C using a microwave heating and stirring method for 2-3 hours;

[0033] In step e, the mass ratio of mixture A to mixture B is (1~2):1, the solid content of the spinning solution is 10~20 wt%, and the spinning process is wet spinning, electrospinning or microfluidic spinning, with a flow rate of 0.1~0.5 mL / min.

[0034] Preferably, step a specifically includes the following sub-steps:

[0035] a1: Take nanocellulose, disperse it in deionized water, prepare a 5-10 wt% suspension, obtain a mixed solution, and place the mixed solution in a closed environment for microwave heating at 400-800W for 30-50s pretreatment.

[0036] a2: Add TEMPO and NaBr, adjust the pH to 10-11 to obtain a mixed solution, wherein the amount of TEMPO is 40%-60% of the mass of nanocellulose, and the amount of NaBr is 20%-30% of the mass of TEMPO; sonicate the mixed solution for 10-15 minutes.

[0037] a3: Oxidize at 20~30℃ under 100-200W microwave conditions for 2~4 hours, then centrifuge, wash, and freeze dry to obtain the product.

[0038] Preferably, step b specifically includes the following sub-steps:

[0039] b1: Using polytetrahydrofuran as the soft segment, isophorone diisocyanate as the hard segment, and dithiodiamine as the chain extender, the soft segment, hard segment, and chain extender are mixed in a molar ratio of 1:2:(0.01~0.02) under nitrogen protection and reacted at 60~70℃ for 4~6 hours.

[0040] b2: The reaction product is dissolved in DMF and prepared into a 10~20 wt% solution.

[0041] Preferably, the pH-sensitive unit is graphene oxide-grafted chitosan, and its preparation process includes the following steps:

[0042] Take chitosan and disperse it in a 1-2 wt% acetic acid solution to prepare a 1-3 wt% solution;

[0043] Add graphene oxide and stir until homogeneous, wherein the mass ratio of graphene oxide to chitosan is 1:(2~5);

[0044] Under EDC / NHS catalysis, the reaction was carried out at 60~70℃ for 8~12 hours;

[0045] After centrifugation, washing, and freeze-drying, graphene oxide-grafted chitosan was obtained.

[0046] Preferably, step e further includes the synergist graphene oxide, and the pH-sensitive unit is chitosan modified with polyphosphocholine groups. Its preparation process includes the following steps:

[0047] Take chitosan and disperse it in a 1-2 wt% acetic acid solution to prepare a 1-3 wt% solution;

[0048] Add 2-methacryloxyethyl phosphocholine and stir until homogeneous, wherein the mass ratio of 2-methacryloxyethyl phosphocholine to chitosan is 1:(3~5);

[0049] A photoinitiator is added, and the reaction is carried out under UV light for 6 to 10 hours, wherein the amount of the photoinitiator is 1% to 2% of the mass of 2-methacryloyloxyethyl phosphocholine;

[0050] After centrifugation, washing, and freeze-drying, chitosan modified with polyphosphocholine groups was obtained.

[0051] The modified biodegradable fiber provided by this invention has the following beneficial effects:

[0052] 1. This application utilizes polymers containing dynamic chemical bonds and pH-sensitive units, enabling fibers to dynamically regulate their degradation rate in different tissue microenvironments (e.g., changes in pH or redox environment). This overcomes the limitations of existing technologies such as polylactic acid and polyglycolic acid, which have fixed degradation rates, thus meeting the diverse clinical needs of rapidly healing tissues and deep tissues. The pH-sensitive units endow the fibers with environmental responsiveness, while the dynamic chemical bonds of the functional components provide self-repair capabilities, enhancing the stability and functionality of the fibers in complex tissue environments and broadening their application scope. All components are biodegradable materials, and the degradation products are non-toxic, compliant with standards, and suitable for various surgical suturing scenarios.

[0053] 2. This application utilizes multiple microwave thermal shocks and microwave composite stirring methods to accelerate the movement of molecules, which is beneficial for full reaction at each stage. At the same time, compared with the traditional microwave method which is mostly used for the thermal decomposition of precursor materials, this application innovatively integrates it throughout the staged reaction process. On the one hand, it improves the thermal motion of molecules in the reaction process, and on the other hand, it effectively reduces problems such as agglomeration. In addition, this application innovatively adopts stepwise mixing, which optimizes the interfacial compatibility and distribution uniformity between components, ensures the stability of the internal structure of the fiber and the consistency of performance, and enhances the synergistic effect of adaptive degradation and mechanical properties.

[0054] 3. This application achieves a tensile strength of 218.7 MPa, a pH 5.5 degradation rate of 59.3%, and a GSH degradation rate of 49.6% through the design of synergistic effects of components, distribution mixing, microwave thermal shock, and microwave composite stirring process; the degradation response is fast, making it suitable for high infection risk and deep tissue repair. Attached Figure Description

[0055] Figure 1 An optical photograph of the degradable fiber prepared in Example 1 of this application;

[0056] Figure 2 Optical photograph 2 of the degradable fiber prepared in Example 1 of this application. Detailed Implementation

[0057] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0058] This embodiment provides a modified biodegradable fiber, which, by weight, comprises the following components: 30-60 parts of matrix material, 20-50 parts of functional component, 5-20 parts of pH-sensitive unit, and 5-20 parts of reinforcing agent.

[0059] The matrix material is selected from nanocellulose modified derivatives, the functional components are selected from polymers containing dynamic chemical bonds, the pH-sensitive unit is selected from chitosan or its modified derivatives, and the reinforcing agent is selected from biodegradable polyester.

[0060] Furthermore, in Embodiment 1 provided in this implementation:

[0061] The modified nanocellulose derivative is carboxylated nanocellulose.

[0062] Polymers containing dynamic chemical bonds are self-healing polyurethanes containing disulfide bonds.

[0063] The pH-sensitive unit is chitosan.

[0064] Biodegradable polyester is converted into polylactic acid.

[0065] Among them, PU-SS containing disulfide bonds breaks down and degrades more rapidly in a highly reducing environment (such as during the inflammatory period, containing glutathione), while chitosan dissolves more quickly in an acidic environment. The degradation rate can reach 60% in 30 days, while the degradation rate is only 20% in a neutral environment. This overcomes the limitation of fixed degradation rate in existing technologies and meets the needs of different tissue healing cycles.

[0066] CNC-COOH provides high strength, PLA enhances initial rigidity, and has an elongation at break of up to 15%, ensuring the mechanical stability of the fiber in surgical sutures.

[0067] CNC-COOH, CS, and PLA are all biodegradable materials with non-toxic degradation products, making them suitable for applications such as skin suturing.

[0068] Furthermore, in Embodiment 2 provided in this implementation:

[0069] The modified nanocellulose derivative is carboxylated nanocellulose.

[0070] Polymers containing dynamic chemical bonds are self-healing polyurethanes containing disulfide bonds.

[0071] The pH-sensitive unit is graphene oxide grafted with chitosan.

[0072] The biodegradable polyester is polydioxanone.

[0073] Among them, CS-g-GO improves pH responsiveness, achieving a degradation rate of up to 70% in an acidic environment after 20 days, while the degradation rate is only 25% in a neutral environment after 60 days; PPDO provides a wider degradation cycle to meet the needs of complex tissue repair.

[0074] PPDO replaces PLA, increasing fiber flexibility; CS-g-GO and CNC-COOH synergistically improve tensile strength and enhance suture operability.

[0075] CS-g-GO has an antibacterial rate of up to 90% against Staphylococcus aureus, promotes cell adhesion, enhances tissue compatibility, and is suitable for the repair of infected wounds.

[0076] Furthermore, in Example 3 provided in this embodiment, 1 to 10 parts of a synergist are also included.

[0077] The modified nanocellulose derivative is carboxylated nanocellulose.

[0078] Polymers containing dynamic chemical bonds are self-healing polyurethanes containing disulfide bonds.

[0079] The pH-sensitive unit is chitosan modified with polyphosphocholine groups.

[0080] The biodegradable polyester is polydioxanone.

[0081] The synergist is graphene oxide.

[0082] Among them, the cell membrane-like structure of CS-PC can reach a degradation rate of 75% in an acidic environment after 15 days, while the degradation rate is only 22% in a neutral environment after 90 days. It has a wider range of regulation and is suitable for high infection risk and deep tissue repair.

[0083] This embodiment also provides a preparation method for preparing the modified biodegradable fiber as described in any one of the above embodiments, comprising the following steps:

[0084] a) Chemically modify nanocellulose to obtain a matrix material.

[0085] b) Synthesize polymers containing dynamic chemical bonds as functional components.

[0086] c) Mix the pH-sensitive unit with the matrix material to obtain mixture A.

[0087] d) Mix the reinforcing agent with the functional component to obtain mixture B.

[0088] e) Mix mixture A with mixture B to prepare a spinning solution, and use a spinning process to prepare modified biodegradable fibers.

[0089] The preparation method provided in this embodiment optimizes the interfacial compatibility and distribution uniformity between components through stepwise mixing, ensuring the stability and performance consistency of the internal structure of the fiber, and enhancing the synergistic effect of adaptive degradation and mechanical properties.

[0090] Furthermore:

[0091] Step c, mixing the pH-sensitive unit with the matrix material, specifically includes: adding the pH-sensitive unit and the matrix material to a solvent, and stirring the composite solution for 1 to 3 hours using a microwave heating and stirring method, wherein the solvent is a mixture of DMF and water, with a volume ratio of 7:3 to 8:2.

[0092] Step d, which involves mixing the reinforcing agent and the functional component, specifically includes adding the reinforcing agent and the functional component to DMF and stirring the composite solution at 60-70°C using a microwave heating and stirring method for 2-3 hours.

[0093] In step e, the mass ratio of mixture A to mixture B is (1~2):1, the solid content of the spinning solution is 10~20 wt%, and the spinning process is wet spinning, electrospinning or microfluidic spinning, with a flow rate of 0.1~0.5 mL / min.

[0094] Furthermore, step a specifically includes the following sub-steps:

[0095] a1: Take nanocellulose, disperse it in deionized water, prepare a 5-10 wt% suspension, obtain a mixed solution, and place the mixed solution in a closed environment for microwave heating at 400-800W for 30-50s pretreatment.

[0096] a2: Add TEMPO and NaBr, adjust the pH to 10-11 to obtain a mixed solution, wherein the amount of TEMPO is 40%-60% of the mass of nanocellulose and the amount of NaBr is 20%-30% of the mass of TEMPO. Sonicate the mixed solution for 10-15 minutes.

[0097] a3: It is obtained by oxidizing at 20~30℃ under 100-200W microwave conditions for 2~4 hours, followed by centrifugation, washing, and freeze-drying.

[0098] Furthermore, step b specifically includes the following sub-steps:

[0099] b1: Using polytetrahydrofuran as the soft segment, isophorone diisocyanate as the hard segment, and disulfide diamine as the chain extender, the soft segment, hard segment, and chain extender are mixed in a molar ratio of 1:2:(0.01~0.02) under nitrogen protection and reacted at 60~70℃ for 4~6 hours.

[0100] b2: The reaction product is dissolved in DMF and prepared into a 10~20 wt% solution.

[0101] Furthermore, the pH-sensitive unit is graphene oxide grafted chitosan, and its preparation process includes the following steps:

[0102] Take chitosan and disperse it in a 1-2 wt% acetic acid solution to prepare a 1-3 wt% solution.

[0103] Add graphene oxide and stir until homogeneous, wherein the mass ratio of graphene oxide to chitosan is 1:(2~5).

[0104] The reaction was carried out at 60-70°C for 8-12 hours under EDC / NHS catalysis.

[0105] After centrifugation, washing, and freeze-drying, graphene oxide-grafted chitosan was obtained.

[0106] Furthermore, step e also includes the synergist graphene oxide, and the pH-sensitive unit is chitosan modified with polyphosphocholine groups. The preparation process includes the following steps:

[0107] Take chitosan and disperse it in a 1-2 wt% acetic acid solution to prepare a 1-3 wt% solution.

[0108] Add 2-methacryloxyethyl phosphocholine and stir until homogeneous, wherein the mass ratio of 2-methacryloxyethyl phosphocholine to chitosan is 1:(3~5).

[0109] Add a photoinitiator and react under UV light for 6 to 10 hours, wherein the amount of photoinitiator is 1% to 2% of the mass of 2-methacryloyloxyethyl phosphocholine.

[0110] After centrifugation, washing, and freeze-drying, chitosan modified with polyphosphocholine groups was obtained.

[0111] Specific embodiments are provided below. These embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0112] Example 1

[0113] Weigh 20.0 g of nanocellulose, add 200 mL of deionized water, and disperse using a magnetic stirrer (500 rpm) for 30 minutes to prepare a 10 wt% suspension. Pre-treat the mixture in a sealed environment using microwave heating at 400-800 W for 40 seconds. Add 8.0 g of TEMPO and 1.6 g of NaBr, adjust the pH to 10.2 by adding 1 M NaOH solution, and sonicate for 15 minutes. Oxidize at 25°C for 2.5 hours with a stirring speed of 300 rpm. After the reaction, add 40 mL of ethanol, centrifuge (5000 rpm) for 10 minutes, wash three times with deionized water, and freeze-dry (-50°C) for 48 hours to obtain CNC-COOH.

[0114] Weigh 40.0 g PTMG, 17.76 g IPDI and 0.60 g DSDA, add 200 mL DMF, and react in a constant temperature water bath (65℃) for 4.5 hours under nitrogen protection with stirring at 200 rpm. Cool the reaction product to room temperature and prepare a 15 wt% DMF solution (PU-SS) for later use.

[0115] Weigh 5.0 g of chitosan and dissolve it in 100 mL of 1 wt% acetic acid solution (60℃), stirring for 30 minutes. Add 20.0 g of CNC-COOH and disperse it in 160 mL of DMF / water (volume ratio 8:2) mixed solvent. Stir the composite solution at 30℃ using a microwave heating and stirring method (400 rpm) for 2 hours to obtain mixture A.

[0116] Weigh 5.0 g PLA, add 120 mL DMF, and stir the mixture at 60°C with microwave heating for 1 hour until completely dissolved. Add 33.33 g PU-SS solution and continue stirring at 60°C for 2.5 hours to obtain mixture B.

[0117] Mixture A and mixture B were combined at a mass ratio of 1:1, and DMF / water (8:2) was added to adjust the total solids content to 15 wt%. The mixture was stirred for 1 hour. A wet spinning machine was used with a spinning solution flow rate of 0.5 mL / min, an ethanol / water (1:1, 25℃) coagulation bath, and a receiving distance of 10 cm. The resulting fibers were stretched (stretch ratio 1.2) and then vacuum dried at 50℃ for 12 hours to obtain modified biodegradable fibers.

[0118] Mechanical properties were tested using a tensile testing machine: fiber sample length 50 mm, clamping distance 25 mm, tensile rate 5 mm / min, room temperature (25℃), humidity 50%, tensile strength (MPa) was recorded, 5 tests were performed, and the average value was taken.

[0119] Degradation performance test: Phosphate-buffered saline (PBS, 0.1 M, 37℃) with pH 5.5 and pH 7.4 was prepared to simulate the inflammatory and normal tissue environments; PBS containing 10 mM glutathione (GSH) (pH 7.4, 37℃) was prepared to simulate a highly reducing environment. 0.1 g of fiber sample was weighed and immersed in 20 mL of the test solution, with constant temperature shaking (100 rpm). The test was conducted for 30 days under pH 5.5 and pH 7.4 conditions, with samples taken every 5 days; the test was conducted for 15 days under GSH conditions, with samples taken every 3 days. After drying, the samples were weighed, and the mass loss rate (%) was calculated as (initial mass - remaining mass) / initial mass × 100. Each group was tested three times, and the average value was taken.

[0120] Biocompatibility testing: L929 mouse fibroblasts were used in DMEM culture medium (containing 10% fetal bovine serum and 1% penicillin-streptomycin). Fiber samples (0.2 g) were soaked in 5 mL of medium (37°C, 24 hours) to prepare an extract. Cells were seeded in 96-well plates, the extract was added, and the cells were cultured for 48 hours. Cell viability (%) was determined using a CCK-8 assay kit. Each test was performed six times, and the average value was taken.

[0121] The test data is shown in the table below:

[0122] Test Project Measurement results Tensile strength (MPa) 218.7 ± 4.2 Degradation rate (%) - pH 5.5, 30 days 59.3 ± 2.1 Degradation rate (%) - pH 7.4, 30 days 19.8 ± 1.3 Degradation rate (%) - GSH 10 mM, 15 days 49.6 ± 1.9 Cell viability (%) 96.2 ± 1.8

[0123] Example 2

[0124] Weigh 22.5 g of nanocellulose, add 225 mL of deionized water, and disperse using a magnetic stirrer (500 rpm) for 30 minutes to prepare a 10 wt% suspension. The resulting mixed solution was pretreated by microwave heating at 600 W for 50 s in a sealed environment. Then, 9.0 g of TEMPO and 1.8 g of NaBr were added, and 1 M NaOH solution was added dropwise to adjust the pH to 10.5. The mixed solution was then sonicated for 15 min. Finally, the solution was oxidized at 25 °C under 150 W microwave conditions for 3 hours with a stirring speed of 300 rpm. After the reaction, 40 mL of ethanol was added, and the mixture was centrifuged (5000 rpm) for 10 minutes. The mixture was washed three times with deionized water and lyophilized (-50 °C) for 48 hours to obtain CNC-COOH.

[0125] Weigh 35.0 g PTMG, 14.2 g IPDI and 0.72 g DSDA, add 180 mL DMF, and react in a constant temperature water bath (65℃) for 5 hours under nitrogen protection with stirring at 200 rpm. Cool the reaction product to room temperature and prepare a 15 wt% DMF solution (PU-SS) for later use.

[0126] Weigh 3.333 g of chitosan and dissolve it in 100 mL of 1 wt% acetic acid solution (60℃). Stir for 30 minutes. Add 1.667 g of graphene oxide, 0.8 g of EDC, and 0.48 g of NHS. React at 60℃ for 10 hours with stirring at 300 rpm. Centrifuge (5000 rpm) for 10 minutes, wash three times with deionized water, and freeze-dry (-50℃) for 48 hours to obtain CS-g-GO. Disperse 5.0 g of CS-g-GO and 22.5 g of CNC-COOH in 180 mL of DMF / water (8:2). Stir the mixture using a microwave heating method (400 rpm) for 2 hours to obtain mixture A.

[0127] Weigh 5.0 g PPDO, add 120 mL DMF, and stir at 60℃ for 1.5 hours until dissolved. Add 33.33 g PU-SS solution, and stir the mixture at 60℃ using a microwave heating and stirring method for 2.5 hours to obtain mixture B.

[0128] Mixture A and mixture B were combined at a mass ratio of 1.5:1, and DMF / water (8:2) was added to adjust the total solids content to 15 wt%. The total solvent volume was approximately 300 mL, and the mixture was stirred for 1 hour. An electrospinning machine was used with a voltage of 15 kV, a flow rate of 0.3 mL / min, a receiving distance of 15 cm, and an ethanol / water (1:1, 25℃) coagulation bath. After stretching (stretch ratio 1.3), the fibers were vacuum dried at 50℃ for 12 hours to obtain modified biodegradable fibers.

[0129] Mechanical properties were tested using a tensile testing machine: fiber sample length 50 mm, clamping distance 25 mm, tensile rate 5 mm / min, room temperature (25℃), humidity 50%, tensile strength (MPa) was recorded, 5 tests were performed, and the average value was taken.

[0130] Degradation performance test: PBS (0.1 M, 37℃) with pH 5.0 and pH 7.4 was prepared to simulate inflammatory and normal tissue environments; PBS (pH 7.4, 37℃) containing 10 mM glutathione (GSH) was prepared to simulate a highly reducing environment. 0.1 g of fiber sample was weighed and immersed in 20 mL of the test solution, with constant temperature shaking (100 rpm). Samples were taken every 5 days for pH 5.0 testing, every 60 days for pH 7.4 testing, and every 2 days for GSH testing. After drying, the samples were weighed, and the mass loss rate (%) was calculated as (initial mass - remaining mass) / initial mass × 100. Each test was performed three times, and the average value was taken.

[0131] Antimicrobial performance test: Staphylococcus aureus (ATCC 25923) was used, LB agar, 37°C, for 24 hours. 0.2 g of fiber was placed in a solution containing 1×10⁻⁶...6 The culture medium containing CFU / mL bacteria was used to measure the inhibition rate (%), and the average value was taken from three tests.

[0132] Biocompatibility testing: L929 mouse fibroblasts were used in DMEM culture medium (containing 10% fetal bovine serum and 1% penicillin-streptomycin). Fiber samples (0.2 g) were soaked in 5 mL of medium (37°C, 24 hours) to prepare an extract. Cells were seeded in 96-well plates, the extract was added, and the cells were cultured for 48 hours. Cell viability (%) was determined using a CCK-8 assay kit. Each test was performed six times, and the average value was taken.

[0133] The test data is shown in the table below:

[0134] Test Project Measurement results Tensile strength (MPa) 261.3 ± 3.9 Degradation rate (%) - pH 5.0, 20 days 69.8 ± 2.3 Degradation rate (%) - pH 7.4, 60 days 24.6 ± 1.5 Degradation rate (%) - GSH 10 mM, 10 days 54.9 ± 2.0 Antibacterial rate (%) - Staphylococcus aureus 89.7 ± 1.6 Cell viability (%) 98.1 ± 1.4

[0135] Example 3

[0136] Weigh 22.5 g of nanocellulose, add 225 mL of deionized water, and disperse using a magnetic stirrer (500 rpm) for 30 minutes to prepare a 10 wt% suspension. The resulting mixed solution was pretreated by microwave heating at 500 W for 30 s in a sealed environment. Then, 9.0 g of TEMPO and 1.8 g of NaBr were added, and 1 M NaOH solution was added dropwise to adjust the pH to 10.8. The mixed solution was then sonicated for 10 min. Finally, the solution was oxidized at 25 °C under 200 W microwave conditions for 3.5 hours with a stirring speed of 300 rpm. After the reaction, 40 mL of ethanol was added, and the mixture was centrifuged (5000 rpm) for 10 minutes. The mixture was washed three times with deionized water and lyophilized (-50 °C) for 48 hours to obtain CNC-COOH.

[0137] Weigh 35.0 g PTMG, 14.2 g IPDI and 0.88 g DSDA, add 180 mL DMF, and react in a constant temperature water bath (65℃) for 5.5 hours under nitrogen protection with stirring at 200 rpm. Cool the reaction product to room temperature and prepare a 15 wt% DMF solution (PU-SS) for later use.

[0138] Weigh 4.0 g of chitosan and dissolve it in 100 mL of 1 wt% acetic acid solution (60℃), stirring for 30 minutes. Add 1.0 g of MPC and 0.012 g of Irgacure 2959, and react under 365 nm UV light for 8 hours with stirring at 300 rpm. Centrifuge (5000 rpm) for 10 minutes, wash three times with deionized water, and freeze-dry (-50℃) for 48 hours to obtain CS-PC. Disperse 5.0 g of CS-PC and 22.5 g of CNC-COOH in 180 mL of DMF / water (7:3), and stir using a microwave heating method (400 rpm) for 2 hours to obtain mixture A.

[0139] Weigh 5.0 g of PPDO, add 120 mL of DMF, and stir the mixture at 60°C with microwave heating for 1.5 hours until dissolved. Add 33.33 g of PU-SS solution and stir at 60°C for 2.5 hours to obtain mixture B.

[0140] Mixture A and mixture B were combined at a mass ratio of 1.5:1. 2.5 g of GO was added, and the total solids content was adjusted to 15 wt% using DMF / water (7:3). The total solvent volume was approximately 315 mL, and the mixture was stirred for 1 hour. A microfluidic spinning device was used with a coaxial nozzle. The core flow rate was 0.2 mL / min (CNC-COOH and PPDO), and the shell flow rate was 0.1 mL / min (PU-SS, CS-PC, and GO). The coagulation bath was ethanol / water (2:1, 25℃). After stretching (stretch ratio 1.4), the fibers were vacuum dried at 50℃ for 12 hours to obtain modified biodegradable fibers.

[0141] Mechanical properties were tested using a tensile testing machine: fiber sample length 50 mm, clamping distance 25 mm, tensile rate 5 mm / min, room temperature (25℃), humidity 50%, tensile strength (MPa) was recorded, 5 tests were performed, and the average value was taken.

[0142] Degradation performance test: PBS (0.1 M, 37℃) with pH 5.0 and pH 7.4 was prepared to simulate inflammatory and normal tissue environments; PBS (pH 7.4, 37℃) containing 10 mM glutathione (GSH) was prepared to simulate a highly reducing environment. 0.1 g of fiber sample was weighed and immersed in 20 mL of the test solution, with constant temperature shaking (100 rpm). Samples were taken every 5 days for pH 5.0 testing, every 90 days for pH 7.4 testing, and every 2 days for GSH testing. After drying, the samples were weighed, and the mass loss rate (%) was calculated as (initial mass - remaining mass) / initial mass × 100. Each test was performed three times, and the average value was taken.

[0143] Antimicrobial performance test: Staphylococcus aureus (ATCC 25923) and drug-resistant bacteria (MRSA, ATCC 43300) were tested using LB agar at 37°C for 24 hours. 0.2 g of fiber was placed in a solution containing 1×10⁻⁶... 6 The culture medium containing CFU / mL bacteria was used to measure the inhibition rate (%), and the average value was taken from three tests.

[0144] Biocompatibility testing: L929 mouse fibroblasts were used in DMEM culture medium (containing 10% fetal bovine serum and 1% penicillin-streptomycin). Fiber samples (0.2 g) were soaked in 5 mL of medium (37°C, 24 hours) to prepare an extract. Cells were seeded in 96-well plates, the extract was added, and the cells were cultured for 48 hours. Cell viability (%) was determined using a CCK-8 assay kit. Each test was performed six times, and the average value was taken.

[0145] The test data is shown in the table below:

[0146] Test Project Measurement results Tensile strength (MPa) 284.6 ± 4.1 Degradation rate (%) - pH 5.0, 15 days 74.7 ± 2.2 Degradation rate (%) - pH 7.4, 90 days 22.3 ± 1.4 Degradation rate (%) - GSH 10 mM, 8 days 59.8 ± 1.7 Antibacterial rate (%) - Staphylococcus aureus 95.4 ± 1.3 Antibacterial rate (%) - MRSA 94.8 ± 1.5 Cell viability (%) 99.2 ± 1.2

[0147] Comparative Example 1

[0148] Weigh 50.0 g PLA and add 280 mL DMF. Stir at 60°C for 2 hours until completely dissolved to prepare a 15 wt% spinning solution. Use a wet spinning machine with a flow rate of 0.5 mL / min, a coagulation bath of ethanol / water (1:1, 25°C), and a receiving distance of 10 cm. After stretching (stretch ratio 1.2), the fibers are vacuum dried at 50°C for 12 hours to obtain the finished fibers.

[0149] Mechanical properties were tested using a tensile testing machine: fiber sample length 50 mm, clamping distance 25 mm, tensile rate 5 mm / min, room temperature (25℃), humidity 50%, tensile strength (MPa) was recorded, 5 tests were performed, and the average value was taken.

[0150] Degradation performance test: Prepare phosphate buffer (PBS, 0.1 M, 37℃) at pH 5.5 and pH 7.4 to simulate inflammatory and normal tissue environments. Weigh 0.1 g of fiber sample and immerse it in 20 mL of test solution, then shake at a constant temperature (100 rpm). Test for 30 days, sampling every 5 days. After drying, weigh the sample and calculate the mass loss rate (%) = (initial mass - remaining mass) / initial mass × 100. Perform three tests and take the average value.

[0151] The test data is shown in the table below:

[0152] Test Project Measurement results Tensile strength (MPa) 179.4 ± 3.8 Degradation rate (%) - pH 5.5, 30 days 29.8 ± 1.5 Degradation rate (%) - pH 7.4, 30 days 28.9 ± 1.4

[0153] Comparative Example 2

[0154] Weigh 30.0 g of nanocellulose and add 300 mL of deionized water. Disperse the nanocellulose using a magnetic stirrer (500 rpm) for 30 minutes to prepare a 10 wt% suspension. Add 12.0 g of TEMPO and 2.4 g of NaBr, and adjust the pH to 10.2 by adding 1 M NaOH solution dropwise. Oxidize the nanocellulose at 25 °C for 2.5 hours with a stirring speed of 300 rpm. After the reaction is complete, add 40 mL of ethanol, centrifuge (5000 rpm) for 10 minutes, wash three times with deionized water, and freeze-dry (-50 °C) for 48 hours to obtain CNC-COOH.

[0155] Weigh 30.0 g CNC-COOH and 20.0 g PLA, disperse them in 280 mL DMF / water (8:2), and stir magnetically (400 rpm) for 2 hours to prepare a 15 wt% spinning solution.

[0156] A wet spinning machine was used at a flow rate of 0.5 mL / min, with an ethanol / water coagulation bath (1:1, 25℃) and a receiving distance of 10 cm. The fibers were stretched (stretch ratio 1.2) and then vacuum dried at 50℃ for 12 hours to obtain modified biodegradable fibers.

[0157] Mechanical properties were tested using a tensile testing machine: fiber sample length 50 mm, clamping distance 25 mm, tensile rate 5 mm / min, room temperature (25℃), humidity 50%, tensile strength (MPa) was recorded, 5 tests were performed, and the average value was taken.

[0158] Degradation performance test: Phosphate-buffered saline (PBS, 0.1 M, 37℃) with pH 5.5 and pH 7.4 was prepared to simulate the inflammatory and normal tissue environments; PBS containing 10 mM glutathione (GSH) (pH 7.4, 37℃) was prepared to simulate a highly reducing environment. 0.1 g of fiber sample was weighed and immersed in 20 mL of the test solution, with constant temperature shaking (100 rpm). The test was conducted for 30 days under pH 5.5 and pH 7.4 conditions, with samples taken every 5 days; the test was conducted for 15 days under GSH conditions, with samples taken every 3 days. After drying, the samples were weighed, and the mass loss rate (%) was calculated as (initial mass - remaining mass) / initial mass × 100. Each group was tested three times, and the average value was taken.

[0159] The test data is shown in the table below:

[0160] Test Project Measurement results Tensile strength (MPa) 199.2 ± 4.0 Degradation rate (%) - pH 5.5, 30 days 27.6 ± 1.6 Degradation rate (%) - pH 7.4, 30 days 25.8 ± 1.4

[0161] Comparative Example 3

[0162] Weigh 30.0 g of nanocellulose and add 300 mL of deionized water. Disperse the nanocellulose using a magnetic stirrer (500 rpm) for 30 minutes to prepare a 10 wt% suspension. Add 12.0 g of TEMPO and 2.4 g of NaBr, and adjust the pH to 10.2 by adding 1 M NaOH solution dropwise. Oxidize the nanocellulose at 25 °C for 2.5 hours with a stirring speed of 300 rpm. After the reaction is complete, add 40 mL of ethanol, centrifuge (5000 rpm) for 10 minutes, wash three times with deionized water, and freeze-dry (-50 °C) for 48 hours to obtain CNC-COOH.

[0163] Weigh 20.0 g of chitosan and dissolve it in 400 mL of 1 wt% acetic acid solution (60℃), stirring for 30 minutes. Add 30.0 g of CNC-COOH and disperse it in 280 mL of DMF / water (8:2), stirring magnetically (400 rpm) for 2 hours to prepare a 15 wt% spinning solution. Use a wet spinning machine with a spinning solution flow rate of 0.5 mL / min, a coagulation bath of ethanol / water (1:1, 25℃), and a receiving distance of 10 cm. The resulting fibers are stretched (stretch ratio 1.2) and then vacuum dried at 50℃ for 12 hours to obtain modified biodegradable fibers.

[0164] Mechanical properties were tested using a tensile testing machine: fiber sample length 50 mm, clamping distance 25 mm, tensile rate 5 mm / min, room temperature (25℃), humidity 50%, tensile strength (MPa) was recorded, 5 tests were performed, and the average value was taken.

[0165] Degradation performance test: Prepare phosphate buffer (PBS, 0.1 M, 37℃) at pH 5.5 and pH 7.4 to simulate inflammatory and normal tissue environments. Weigh 0.1 g of fiber sample and immerse it in 20 mL of test solution, then shake at a constant temperature (100 rpm). Test for 30 days, sampling every 5 days. After drying, weigh the sample and calculate the mass loss rate (%) = (initial mass - remaining mass) / initial mass × 100. Perform three tests and take the average value.

[0166] Antimicrobial performance test: Staphylococcus aureus (ATCC 25923) was used, LB agar, 37°C, for 24 hours. 0.2 g of fiber was placed in a solution containing 1×10⁻⁶... 6 The culture medium containing CFU / mL bacteria was used to measure the inhibition rate (%), and the average value was taken from three tests.

[0167] The test data is shown in the table below:

[0168] Test Project Measurement results Tensile strength (MPa) 189.7 ± 3.9 Degradation rate (%) - pH 5.5, 30 days 39.4 ± 1.8 Degradation rate (%) - pH 7.4, 30 days 29.6 ± 1.5 Antibacterial rate (%) - Staphylococcus aureus 69.8 ± 2.0

[0169] Comparative Example 4

[0170] Weigh 22.5 g of nanocellulose and add 225 mL of deionized water. Disperse the mixture for 30 minutes using a magnetic stirrer (500 rpm) to prepare a 10 wt% suspension. Add 9.0 g of TEMPO and 1.8 g of NaBr, and adjust the pH to 10.8 by adding 1 M NaOH solution dropwise. Incubate the oxidation reaction at 25 °C for 3.5 hours with a stirring speed of 300 rpm. After the reaction is complete, add 40 mL of ethanol, centrifuge (5000 rpm) for 10 minutes, wash three times with deionized water, and freeze-dry (-50 °C) for 48 hours to obtain CNC-COOH.

[0171] Weigh 35.0 g PTMG, 14.2 g IPDI and 0.88 g DSDA, add 180 mL DMF, and react in a constant temperature water bath (65℃) for 5.5 hours under nitrogen protection with stirring at 200 rpm. Cool the reaction product to room temperature and prepare a 15 wt% DMF solution (PU-SS) for later use.

[0172] Weigh 4.0 g of chitosan and dissolve it in 100 mL of 1 wt% acetic acid solution (60℃), stirring for 30 minutes. Add 1.0 g of MPC and 0.012 g of Irgacure 2959, and react under 365 nm UV light for 8 hours with stirring at 300 rpm. Centrifuge (5000 rpm) for 10 minutes, wash three times with deionized water, and freeze-dry (-50℃) for 48 hours to obtain CS-PC. Disperse 5.0 g of CS-PC and 22.5 g of CNC-COOH in 180 mL of DMF / water (7:3) and stir magnetically (400 rpm) for 2 hours to obtain mixture A.

[0173] Weigh 5.0 g PPDO, add 120 mL DMF, and stir at 60°C for 1.5 hours until dissolved. Add 33.33 g PU-SS solution, and stir at 60°C for 2.5 hours to obtain mixture B.

[0174] Mixture A and mixture B were combined at a mass ratio of 1.5:1, and DMF / water (7:3) was added to adjust the total solids content to 15 wt%. The total solvent volume was approximately 300 mL, and the mixture was stirred for 1 hour. A microfluidic spinning device was used with a coaxial nozzle, a core flow rate of 0.2 mL / min, a shell flow rate of 0.1 mL / min, and an ethanol / water (2:1, 25℃) coagulation bath. After stretching (stretch ratio 1.4), the fibers were vacuum dried at 50℃ for 12 hours to obtain modified biodegradable fibers.

[0175] Mechanical properties were tested using a tensile testing machine: fiber sample length 50 mm, clamping distance 25 mm, tensile rate 5 mm / min, room temperature (25℃), humidity 50%, tensile strength (MPa) was recorded, 5 tests were performed, and the average value was taken.

[0176] Degradation performance test: Prepare phosphate buffer (PBS, 0.1 M, 37℃) at pH 5.0 and pH 7.4 to simulate inflammatory and normal tissue environments. Weigh 0.1 g of fiber sample and immerse it in 20 mL of test solution, shaking at a constant temperature (100 rpm). Test at pH 5.0 for 15 days and at pH 7.4 for 90 days, sampling every 5 days. After drying, weigh the sample and calculate the mass loss rate (%) = (initial mass - remaining mass) / initial mass × 100. Each group was tested 3 times, and the average value was taken.

[0177] Antimicrobial performance test: Staphylococcus aureus (ATCC 25923) and drug-resistant bacteria (MRSA, ATCC 43300) were tested using LB agar at 37°C for 24 hours. 0.2 g of fiber was placed in a solution containing 1×10⁻⁶... 6 The culture medium containing CFU / mL bacteria was used to measure the inhibition rate (%), and the average value was taken from three tests.

[0178] The test data is shown in the table below:

[0179] Test Project Measurement results Tensile strength (MPa) 249.8 ± 4.0 Degradation rate (%) - pH 5.0, 15 days 69.5 ± 2.1 Degradation rate (%) - pH 7.4, 90 days 24.7 ± 1.6 Antibacterial rate (%) - Staphylococcus aureus 89.9 ± 1.7 Antibacterial rate (%) - MRSA 88.7 ± 1.8

[0180] Comparative Example 5

[0181] Weigh 20.0 g of nanocellulose and add 200 mL of deionized water. Disperse the nanocellulose using a magnetic stirrer (500 rpm) for 30 minutes to prepare a 10 wt% suspension. Add 8.0 g of TEMPO and 1.6 g of NaBr, and adjust the pH to 10.2 by adding 1 M NaOH solution dropwise. Oxidize the nanocellulose at 25 °C for 2.5 hours with a stirring speed of 300 rpm. After the reaction is complete, add 40 mL of ethanol, centrifuge (5000 rpm) for 10 minutes, wash three times with deionized water, and freeze-dry (-50 °C) for 48 hours to obtain CNC-COOH.

[0182] Weigh 40.0 g PTMG, 17.76 g IPDI and 0.60 g DSDA, add 200 mL DMF, and react in a constant temperature water bath (65℃) for 4.5 hours under nitrogen protection with stirring at 200 rpm. Cool the reaction product to room temperature and prepare a 15 wt% DMF solution (PU-SS) for later use.

[0183] Weigh 5.0 g of chitosan and dissolve it in 100 mL of 1 wt% acetic acid solution (60℃), stirring for 30 minutes. Add 20.0 g of CNC-COOH, 33.33 g of PU-SS solution, and 5.0 g of PLA, dispersing in 280 mL of DMF / water (8:2), and magnetically stir (400 rpm) for 3 hours to prepare a 15 wt% spinning solution. Use a wet spinning machine with a spinning solution flow rate of 0.5 mL / min, a coagulation bath of ethanol / water (1:1, 25℃), and a receiving distance of 10 cm. The resulting fibers are stretched (stretch ratio 1.2) and then vacuum dried at 50℃ for 12 hours to obtain modified biodegradable fibers.

[0184] Mechanical properties were tested using a tensile testing machine: fiber sample length 50 mm, clamping distance 25 mm, tensile rate 5 mm / min, room temperature (25℃), humidity 50%, tensile strength (MPa) was recorded, 5 tests were performed, and the average value was taken.

[0185] Degradation performance test: Phosphate-buffered saline (PBS, 0.1 M, 37℃) with pH 5.5 and pH 7.4 was prepared to simulate the inflammatory and normal tissue environments; PBS containing 10 mM glutathione (GSH) (pH 7.4, 37℃) was prepared to simulate a highly reducing environment. 0.1 g of fiber sample was weighed and immersed in 20 mL of the test solution, with constant temperature shaking (100 rpm). The test was conducted for 30 days under pH 5.5 and pH 7.4 conditions, with samples taken every 5 days; the test was conducted for 15 days under GSH conditions, with samples taken every 3 days. After drying, the samples were weighed, and the mass loss rate (%) was calculated as (initial mass - remaining mass) / initial mass × 100. Each group was tested three times, and the average value was taken.

[0186] The test data is shown in the table below:

[0187] Test Project Measurement results Tensile strength (MPa) 190.3 ± 4.1 Degradation rate (%) - pH 5.5, 30 days 50.2 ± 2.0 Degradation rate (%) - pH 7.4, 30 days 24.9 ± 1.5 Degradation rate (%) - GSH 10 mM, 15 days 44.7 ± 1.8

[0188] The data above show that Examples 1-3, through the combination of CNC-COOH (matrix), PU-SS (functional component), CS / CS-g-GO / CS-PC (pH-sensitive unit), PLA / PPDO (reinforcing agent), and GO (synergist), significantly improved mechanical properties and degradation control, which were superior to Comparative Examples 1-3. Comparative Examples 1-3 verified the limitations of single PLA or the lack of functional components / reinforcing agents, proving the necessity of multi-component synergy. Comparative Example 4 lacked GO, resulting in a decrease in antibacterial properties, verifying the synergistic effect of GO.

[0189] Compared with Comparative Example 5, under the same composition, stepwise mixing increased the tensile strength from 190.3 MPa to 218.7 MPa, the pH 5.5 degradation rate from 50.2% to 59.3%, and the GSH degradation rate from 44.7% to 49.6%, demonstrating that stepwise mixing optimized the interfacial compatibility and functional distribution of the components. Stepwise mixing ensured the synergistic pH response between CS and CNC-COOH, as well as the mechanical synergy between PU-SS and the reinforcing agent.

[0190] Example 2 introduces CS-g-GO, achieving an antibacterial rate of 89.7% and expanding the degradation regulation range; Example 3 introduces CS-PC and GO, achieving an antibacterial rate of >94% and a faster degradation response, making it suitable for high infection risk and deep tissue repair.

[0191] Figures 1-2 This is an optical photograph of the biodegradable fiber prepared in Example 1 of this application. The image clearly shows that the embodiment of this application prepared biodegradable fiber filaments with uniform size. Furthermore, based on the experimental data above, it can be concluded that this application has prepared biodegradable fibers with excellent performance.

[0192] This application utilizes multiple microwave thermal shocks and microwave composite stirring methods to accelerate the movement of molecules, which is beneficial for full reaction at each stage. At the same time, compared with the traditional microwave method which is mostly used for the thermal decomposition of precursor materials, this application innovatively integrates it into the staged reaction process. On the one hand, it improves the thermal motion of molecules in the reaction process, and on the other hand, it effectively reduces problems such as agglomeration in the process. In addition, this application innovatively adopts stepwise mixing, which optimizes the interfacial compatibility and distribution uniformity between components, ensures the stability of the internal structure of the fiber and the consistency of performance, and enhances the synergistic effect of adaptive degradation and mechanical properties.

[0193] Through the design of synergistic effects of components, distribution mixing, microwave thermal shock, and microwave composite stirring process, the tensile strength reached 218.7 MPa, the pH 5.5 degradation rate reached 59.3%, and the GSH degradation rate reached 49.6%. The degradation response is fast, making it suitable for high infection risk and deep tissue repair.

[0194] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be within the scope of protection of the present invention.

Claims

1. A modified biodegradable fiber, characterized in that, The product is made from the following components in parts by weight: 30-60 parts matrix material, 20-50 parts functional components, 5-20 parts pH-sensitive unit, and 5-20 parts reinforcing agent; The matrix material is selected from nanocellulose modified derivatives, the functional components are selected from polymers containing dynamic chemical bonds, the pH-sensitive unit is selected from chitosan or its modified derivatives, and the reinforcing agent is selected from biodegradable polyester. The modified nanocellulose derivative is carboxylated nanocellulose; The polymer containing dynamic chemical bonds is a self-healing polyurethane containing disulfide bonds; The pH-sensitive unit is chitosan or graphene oxide-grafted chitosan; The biodegradable polyester is polylactic acid or polydioxanone.

2. The modified biodegradable fiber according to claim 1, characterized in that: The pH-sensitive unit may also be chitosan modified with polyphosphoric acid choline groups; when the pH-sensitive unit is chitosan modified with polyphosphoric acid choline groups, it further includes 1 to 10 parts of the synergist graphene oxide.

3. A method for preparing modified biodegradable fibers as described in claim 1 or 2, characterized in that, Includes the following steps: a) Chemical modification of nanocellulose under stepwise microwave heating conditions to obtain a matrix material; b) Synthesize polymers containing dynamic chemical bonds as functional components; c) The pH-sensitive unit is mixed with the matrix material to obtain mixture A; d) The reinforcing agent and functional components are mixed to obtain mixture B; e) Mix mixture A with mixture B to prepare a spinning solution, and use a spinning process to prepare modified biodegradable fibers.

4. The preparation method according to claim 3, characterized in that: Step c, which involves mixing the pH-sensitive unit with the matrix material, specifically includes: adding the pH-sensitive unit and the matrix material to a solvent and heating and stirring in a microwave for 1 to 3 hours, wherein the solvent is a mixture of DMF and water in a volume ratio of 7:3 to 8:

2.

5. The preparation method according to claim 3, characterized in that: The mixing of the reinforcing agent and functional components in step d specifically includes: adding the reinforcing agent and functional components to DMF and stirring the composite solution at 60-70°C for 2-3 hours using a microwave heating and stirring method. In step e, the mass ratio of mixture A to mixture B is (1~2):1, the solid content of the spinning solution is 10~20wt%, and the spinning process is wet spinning, electrospinning or microfluidic spinning, with a flow rate of 0.1~0.5 mL / min.

6. The preparation method according to claim 3, characterized in that, Step a specifically includes the following sub-steps: a1: Take nanocellulose, disperse it in deionized water, prepare a 5-10 wt% suspension, obtain a mixed solution, and place the mixed solution in a closed environment for microwave heating at 400-800W for 30-50s pretreatment. a2: Add TEMPO and NaBr, adjust the pH to 10-11 to obtain a mixed solution, wherein the amount of TEMPO is 40%-60% of the mass of nanocellulose, and the amount of NaBr is 20%-30% of the mass of TEMPO; sonicate the mixed solution for 10-15 minutes. a3: Oxidize at 20~30℃ under 100-200W microwave conditions for 2~4 hours, then centrifuge, wash, and freeze dry to obtain the product.

7. The preparation method according to claim 3, characterized in that, Step b specifically includes the following sub-steps: b1: Using polytetrahydrofuran as the soft segment, isophorone diisocyanate as the hard segment, and dithiodiamine as the chain extender, the soft segment, hard segment, and chain extender are mixed in a molar ratio of 1:2:(0.01~0.02) under nitrogen protection and reacted at 60~70℃ for 4~6 hours. b2: The reaction product is dissolved in DMF and prepared into a 10~20 wt% solution.

8. The preparation method according to claim 3, characterized in that, The preparation process of the graphene oxide-grafted chitosan includes the following steps: Take chitosan and disperse it in a 1-2 wt% acetic acid solution to prepare a 1-3 wt% solution; Add graphene oxide and stir until homogeneous, wherein the mass ratio of graphene oxide to chitosan is 1:(2~5); Under EDC / NHS catalysis, the reaction was carried out at 60~70℃ for 8~12 hours; After centrifugation, washing, and freeze-drying, graphene oxide-grafted chitosan was obtained.

9. The preparation method according to claim 3, characterized in that, Step e also includes the synergist graphene oxide, and the pH-sensitive unit is chitosan modified with polyphosphocholine groups. The preparation process includes the following steps: Take chitosan and disperse it in a 1-2 wt% acetic acid solution to prepare a 1-3 wt% solution; Add 2-methacryloxyethyl phosphocholine and stir until homogeneous, wherein the mass ratio of 2-methacryloxyethyl phosphocholine to chitosan is 1:(3~5); A photoinitiator is added, and the reaction is carried out under UV light for 6 to 10 hours, wherein the amount of the photoinitiator is 1% to 2% of the mass of 2-methacryloyloxyethyl phosphocholine; After centrifugation, washing, and freeze-drying, chitosan modified with polyphosphocholine groups was obtained.

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