A biodegradable nonwoven fabric and its preparation process

Abstract

This invention relates to the field of biomedical materials technology, and discloses a biodegradable nonwoven fabric and its preparation process. The nonwoven fabric is made of components including polylactic acid, polycaprolactone, periodate, a copolyester oligomer containing cis-1,2-cyclohexanediol structural units, and a solid biocompatible weakly basic salt. The preparation process includes mixing the components and then melt-blending and melt-blowing to prepare the nonwoven fabric. In this invention, periodate and the copolyester oligomer serve as latent reaction precursors, and the weakly basic salt acts as a pH regulator. When the nonwoven fabric comes into contact with an aqueous environment, the weakly basic salt dissolves, establishing a weakly basic microenvironment that promotes the oxidative cleavage of the copolyester oligomer by periodate, thereby generating aldehyde compounds with antibacterial activity in situ. This invention achieves on-demand generation of antibacterial substances, enabling the nonwoven fabric to possess both high antibacterial rates and low cytotoxicity, solving the technical problem of balancing activity and safety in traditional antibacterial materials.

Description

Technical Field

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

[0002] Biodegradable polymers, such as polylactic acid (PLA) and polycaprolactone (PCL), are widely used in the preparation of nonwoven fabrics and as medical products such as wound dressings and tissue engineering scaffolds due to their excellent biocompatibility and biodegradability. In these applications, the antimicrobial properties of the materials are crucial for preventing bacterial infections.

[0003] Currently, the technical approach to achieving antibacterial function in biodegradable nonwoven fabrics typically involves directly adding or blending antibacterial agents into the polymer matrix. These antibacterial agents include substances such as silver ions, quaternary ammonium salts, and triclosan. This method relies on the migration and release of antibacterial agents from the material matrix to the material surface or surrounding environment, inhibiting or killing microorganisms through direct contact. However, this approach has inherent technical drawbacks. While the added antibacterial agents exert their antibacterial effect, the components they release may also be toxic to human tissue cells, thereby affecting the normal repair and regeneration of tissues, leading to a contradiction between the antibacterial effectiveness and biocompatibility of the material.

[0004] Furthermore, the release process of antibacterial agents is often difficult to control precisely, typically exhibiting a large, explosive release in the initial stage followed by rapid attenuation. Excessively high initial concentrations can exacerbate cytotoxicity risks, while insufficient concentrations in the later stages may lead to ineffective antibacterial action or even induce bacterial resistance. Simultaneously, some antibacterial agents may decompose or become inactive under high-temperature processing conditions such as melt spinning, which not only reduces the final antibacterial performance of the product but may also introduce uncertain degradation products, affecting material safety. Therefore, there is still an urgent need for a biodegradable nonwoven fabric that can provide stable and effective antibacterial function while ensuring biosafety. Summary of the Invention

[0005] The technical problem to be solved by this invention is that existing biodegradable materials that obtain antibacterial function by directly adding antibacterial agents generally suffer from the technical contradiction of being unable to simultaneously achieve antibacterial activity and biocompatibility.

[0006] To address the above problems, the present invention provides the following technical solution:

[0007] In a first aspect, this application provides a biodegradable nonwoven fabric, which adopts the following technical solution:

[0008] A biodegradable nonwoven fabric is made from components comprising the following parts by weight:

[0009] Polylactic acid: 58-68 parts;

[0010] Polycaprolactone: 25-29 parts;

[0011] Periodate: 1-5 parts;

[0012] Copolyester oligomers containing cis-1,2-cyclohexanediol structural units: 2 to 8 parts;

[0013] Solid biocompatible weakly alkaline salt: 1-3 parts.

[0014] By employing the above technical solution, periodate (as a latent precursor), a copolyester oligomer containing cis-1,2-cyclohexanediol structural units, and a solid biocompatible weakly basic salt (as a pH regulator and catalyst) are physically coated and immobilized within a biodegradable polymer matrix composed of polylactic acid and polycaprolactone through a melt blending process. This effectively isolates the highly reactive reactants from the external biological environment. When this nonwoven fabric comes into contact with an aqueous environment, a series of slow, controllable, microscopic synergistic chemical reactions occur within it on the surface of the fiber material:

[0015] First, the solid biocompatible weakly alkaline salt is dissolved and hydrolyzed from the polymer matrix, temporarily adjusting the local microenvironment pH value on the surface of the material fibers to a weakly alkaline state, serving as a key catalytic condition for initiating subsequent oxidative pyrolysis reactions.

[0016] Then, under the aforementioned weakly alkaline conditions, the periodate oxidatively cleaves the cis-1,2-cyclohexanediol structural units on the copolyester oligomer molecular chain.

[0017] Finally, the oxidative cleavage reaction breaks the carbon-carbon single bond on the cis-1,2-cyclohexanediol structural unit and generates two aldehyde groups in situ at the break, thereby generating and releasing aldehyde compounds with antibacterial activity in situ in the nonwoven fabric.

[0018] This technical solution achieves on-demand, in-situ generation of antibacterial active substances by constructing a latent reaction system composed of two inert precursors and a pH regulator within a polymer matrix. The system cleverly utilizes wound exudate as a natural reaction trigger signal, making the generation rate of antibacterial substances positively correlated with the wound's moisture level (i.e., infection or inflammatory state), thus achieving on-demand response and intelligent regulation of antibacterial activity. This design not only avoids the potential biotoxicity caused by directly adding high concentrations of active antibacterial agents, but also automatically reduces the reaction rate as exudate decreases in the later stages of healing, avoiding potential toxicity to newly formed tissue. Simultaneously, the localized, temporary weakly alkaline environment created by the pH regulator enhances the rate and efficiency of the in-situ chemical reaction, enabling the nonwoven fabric to exhibit low cytotoxicity while achieving a high antibacterial rate.

[0019] Preferably, the nonwoven fabric is made of the following components in parts by weight: 60-65 parts of polylactic acid; 25-30 parts of polycaprolactone; 2-4 parts of periodate; 4-6 parts of copolyester oligomer containing cis-1,2-cyclohexanediol structural units; and 1.5-2.5 parts of solid biocompatible weakly basic salt.

[0020] By adopting the above technical solution, the proportions of each component have been further optimized. This proportion range ensures processing fluidity during melt spinning, while also enabling the nonwoven fabric to generate a sufficient concentration of aldehydes after contact with an aqueous environment, achieving an antibacterial rate higher than 99.9% and maintaining a level 1 cytotoxicity rating.

[0021] Preferably, the copolyester oligomer containing cis-1,2-cyclohexanediol structural units is prepared by polycondensation reaction of cis-1,2-cyclohexanediol and adipic acid, and its number-average molecular weight is 1500-5000 g / mol.

[0022] By employing the above technical solution, the source and molecular weight of the copolyester oligomer used as the reaction substrate are limited. This molecular weight range ensures that the oligomer is solid at room temperature, making it easy to mix with other powder components and disperse in the polymer matrix. At the same time, it ensures that each molecular chain contains sufficient reaction sites (cis-1,2-cyclohexanediol units) and does not affect the melt processing properties of the material due to excessively high molecular weight.

[0023] Preferably, the solid biocompatible weakly basic salt is arginine bicarbonate and / or trisodium citrate.

[0024] By adopting the above technical solution, the specific substances of the pH regulator were identified. Arginine bicarbonate and trisodium citrate are both biocompatible solid salts that can stably provide a weakly alkaline buffer system in an aqueous environment.

[0025] Preferably, the periodate is potassium periodate.

[0026] By adopting the above technical solution, the specific substance of the oxidant was identified. Potassium periodate is a stable and readily available solid oxidant that exhibits thermal stability at melt processing temperatures and can effectively oxidize 1,2-diols in an aqueous environment.

[0027] Secondly, this application provides a process for preparing the above-mentioned biodegradable nonwoven fabric, which adopts the following technical solution:

[0028] A process for preparing biodegradable nonwoven fabric includes the following steps:

[0029] Polylactic acid, polycaprolactone, periodate, copolyester oligomer containing cis-1,2-cyclohexanediol structural units, and solid biocompatible weakly basic salt are mixed to obtain a mixture.

[0030] The mixture is melt-blended and melt-blown spun to obtain ultrafine fibers;

[0031] The ultrafine fibers are collected into a web to obtain a nonwoven fabric.

[0032] By employing the above technical solution, and utilizing the anhydrous processing technology of melt blending and meltblown spinning, the reactive components are uniformly coated and dispersed in a fiber matrix composed of polylactic acid and polycaprolactone in a dry state. Since the in-situ chemical reaction requires water as a medium, no chemical reaction occurs between the components during the entire high-temperature melt processing, thus achieving the goal of stably immobilizing the complete latent chemical reaction system within the nonwoven fiber. This process is simple and suitable for large-scale industrial production.

[0033] Preferably, the periodate is further subjected to ball milling before mixing.

[0034] By adopting the above technical solution, the periodate is pretreated to reduce its particle size, which enables it to be more uniformly dispersed in the polymer melt in the subsequent melt blending step, thereby ensuring that the reaction sites inside the fiber are uniformly distributed and the antibacterial properties of the nonwoven fabric are stable.

[0035] Preferably, in the steps of melt blending and meltblown spinning, the melt temperature is 195–215°C and the hot air temperature is 200–230°C.

[0036] By adopting the above technical solution, the key process temperature range is defined. This temperature range ensures that polylactic acid and polycaprolactone are fully plasticized and have low viscosity, which is conducive to the formation of ultrafine fibers, while avoiding thermal degradation of the polymer matrix or functional additives due to excessive temperature.

[0037] Preferably, after the nonwoven fabric is collected into a web, the process further includes a hot-pressing treatment of the nonwoven fabric at a temperature of 95–110°C.

[0038] By adopting the above technical solution, the bonding points between fibers are increased through hot pressing, which improves the mechanical strength and structural density of the nonwoven fabric, making it more suitable for practical applications.

[0039] In summary, the present invention has at least one of the following beneficial technical effects:

[0040] 1. The biodegradable nonwoven fabric of this invention immobilizes periodate and copolyester oligomers, which serve as precursors for the chemical reaction, in an inert state within a polymer matrix. The antibacterial active substances are not added directly, but rather generated on demand through an in-situ chemical reaction between the precursors after the nonwoven fabric comes into contact with an aqueous environment. This design avoids the direct addition of free, highly active antibacterial agents to the material, enabling the material to exhibit a high antibacterial rate while maintaining a Grade 1 in vitro cytotoxicity level for its extract. This solves the technical problem in existing technologies where it is difficult to simultaneously achieve both antibacterial performance and biocompatibility.

[0041] 2. The biodegradable nonwoven fabric of the present invention incorporates a solid biocompatible weakly alkaline salt into the composition. When in contact with an aqueous environment, this component can adjust the microenvironment surrounding the material to a weakly alkaline pH, which effectively accelerates the oxidative degradation reaction of the copolyester oligomer by periodate. Test results show that the material containing this component exhibits significantly higher rates of antibacterial activity and a higher final antibacterial rate than the system without this component, confirming the catalytic function of this component in in-situ chemical reactions. Through the synergistic effect of the components within the system, the effective realization of the material's antibacterial function is ensured.

[0042] 3. The preparation process of this invention employs melt blending and meltblown spinning technologies. Since the in-situ chemical reaction requires water as a medium for initiation, during the entire anhydrous high-temperature melt processing, each reactive component can be uniformly dispersed and encapsulated within the polymer fibers in a chemically inert state. This process ensures the stability of the latent reaction system during preparation and storage, and enables the production of nonwoven fabric products with uniform performance and controllable trigger-based antibacterial function through mature industrial methods. Detailed Implementation

[0043] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0044] Polylactic acid (PLA), CAS No.: 26100-51-6, the weight-average molecular weight range of PLA used in the embodiments of the present invention is 150,000 to 250,000 g / mol.

[0045] Polycaprolactone (PCL), CAS No.: 24980-41-4, the weight-average molecular weight range of PCL used in the embodiments of this invention is 70,000 to 100,000 g / mol.

[0046] The 1,2-cyclohexanediol-adipic acid copolyester oligomer is a self-prepared material of this invention, and its specific preparation method is described in the subsequent preparation examples. This material is a linear copolyester oligomer obtained by polycondensation reaction of cis-1,2-cyclohexanediol (CAS No.: 1792-81-0) and adipic acid (CAS No.: 124-04-9). Its chemical structure contains vicinal diol structural units derived from cis-1,2-cyclohexanediol and adipate ester structural units derived from adipic acid. The oligomer is a colorless to pale yellow brittle solid at room temperature (25°C), with a number-average molecular weight ranging from 1500 to 5000 g / mol.

[0047] Preparation Examples 1-2:

[0048] Preparation Example 1:

[0049] This preparation example provides a method for preparing 1,2-cyclohexanediol-adipic acid copolyester oligomer (B-1), including the following steps:

[0050] 1) In a 1000mL three-necked flask equipped with a mechanical stirrer, thermometer, nitrogen protection tube and Dean-Stark water separator, add 146.14g (1.0mol) of adipic acid, 127.78g (1.1mol) of cis-1,2-cyclohexanediol, 1.4g of p-toluenesulfonic acid monohydrate as a catalyst, and 400mL of toluene as a dehydrating agent.

[0051] 2) Turn on the mechanical stirrer (200 rpm) and purge the system with nitrogen to displace the air. Heat the reaction mixture to 150°C and maintain this temperature while the toluene is refluxed. The water generated during the reaction forms an azeotrope with the toluene, which is condensed and separated into layers in a water separator and collected. Continue the reaction for 8 hours. When the amount of water collected is close to the theoretical value (1.0 mol, approximately 18 mL), stop heating and allow the reaction system to cool naturally to room temperature.

[0052] 3) Transfer the reaction product to a rotary evaporator and remove toluene under a 65°C water bath and vacuum conditions. Dissolve the resulting viscous liquid in 500 mL of dichloromethane, wash twice with 200 mL of saturated sodium bicarbonate aqueous solution, and then wash twice with 200 mL of deionized water until neutral. Separate the organic phase and dry it with anhydrous magnesium sulfate for 12 hours.

[0053] 4) After filtering to remove the desiccant, the filtrate is passed through a rotary evaporator to remove most of the dichloromethane. Finally, it is placed in a vacuum drying oven at 70°C and dried for 36 hours until constant weight is obtained to obtain product B-1.

[0054] Product B-1 is a pale yellow, brittle solid. Its number-average molecular weight was determined to be 2150 g / mol and its polydispersity index to be 1.62 by gel permeation chromatography (GPC, using tetrahydrofuran as the mobile phase and polystyrene as the standard).

[0055] Preparation Example 2:

[0056] This preparation example provides a method for preparing 1,2-cyclohexanediol-adipic acid copolyester oligomer (B-2), as follows:

[0057] The basic operating steps are the same as in Preparation Example 1. The difference lies in the amount of raw materials fed: 146.14 g (1.0 mol) of adipic acid and 121.97 g (1.05 mol) of cis-1,2-cyclohexanediol. The reaction time was extended to 10 hours to obtain a higher degree of polymerization.

[0058] The final product B-2 was a pale yellow brittle solid. Its number-average molecular weight was determined to be 4680 g / mol and its polydispersity index to be 1.85 by gel permeation chromatography (GPC, using tetrahydrofuran as the mobile phase and polystyrene as the standard).

[0059] Examples 1-4:

[0060] Example 1: This example provides a process for preparing a biodegradable nonwoven fabric, including the following steps:

[0061] 1. Raw material preparation and mixing:

[0062] According to the weight proportions, the following components were weighed: 63 parts of polylactic acid (PLA), 27 parts of polycaprolactone (PCL), 3 parts of potassium periodate after ball milling, 5 parts of 1,2-cyclohexanediol-adipic acid copolyester oligomer (B-1) obtained in Preparation Example 1, and 2 parts of arginine bicarbonate.

[0063] The weighed PLA and PCL particles were dried in a vacuum drying oven at 80°C for 10 hours; potassium periodate, oligomer B-1, and arginine bicarbonate were dried in a vacuum drying oven at 70°C for 5 hours.

[0064] Place all dried materials in a high-speed mixer and mix for 15 minutes at room temperature to ensure uniform dispersion of the components.

[0065] 2. Melt blending and meltblown spinning:

[0066] The above mixture is fed evenly into a co-rotating twin-screw extruder using a loss-in-weight feeder. The temperatures of each zone of the extruder are set as follows: feeding zone 170℃, compression zone 190℃, metering zone and die 200℃. The screw speed is set to 150 rpm.

[0067] After being plasticized and uniformly mixed by an extruder, the melt enters the meltblown die. The meltblown process parameters are set as follows: melt temperature 205℃, hot air temperature 215℃, hot air pressure 0.3 MPa, and receiving distance 30 cm. The melt stream is stretched into ultrafine fibers by high-speed hot air.

[0068] 3. Network Formation and Post-processing:

[0069] The microfibers are collected on a negative pressure suction screen and cooled to form a uniform non-woven fiber web.

[0070] The fiber web is calendered using a hot press roller with a linear pressure of 3 MPa and a temperature of 95°C to increase its surface smoothness and mechanical strength.

[0071] After the nonwoven fabric is cut, sealed and packaged, it is finally sterilized with ethylene oxide to obtain the finished product.

[0072] Example 2: This example provides a process for preparing a biodegradable nonwoven fabric, including the following steps:

[0073] 1. Raw material preparation and mixing:

[0074] According to the weight proportions, the following components were weighed: 67.2 parts of polylactic acid (PLA), 28.8 parts of polycaprolactone (PCL), 1 part of potassium periodate after ball milling, 2 parts of 1,2-cyclohexanediol-adipic acid copolyester oligomer (B-1) obtained in Preparation Example 1, and 1 part of arginine bicarbonate.

[0075] The weighed PLA and PCL particles were dried in a vacuum drying oven at 80°C for 12 hours; potassium periodate, oligomer B-1, and arginine bicarbonate were dried in a vacuum drying oven at 70°C for 6 hours.

[0076] Place all dried materials in a high-speed mixer and mix for 20 minutes at room temperature to ensure uniform dispersion of the components.

[0077] 2. Melt blending and meltblown spinning:

[0078] The above mixture is fed evenly into a co-rotating twin-screw extruder using a loss-in-weight feeder. The temperatures of each zone of the extruder are set as follows: feeding zone 160℃, compression zone 180℃, metering zone and die 190℃. The screw speed is set to 100 rpm.

[0079] After being plasticized and uniformly mixed by an extruder, the melt enters the meltblown die. The meltblown process parameters are set as follows: melt temperature 195℃, hot air temperature 200℃, hot air pressure 0.2MPa, and receiving distance 40cm. The melt stream is stretched into ultrafine fibers by high-speed hot air.

[0080] 3. Network Formation and Post-processing:

[0081] The microfibers are collected on a negative pressure suction screen and cooled to form a uniform non-woven fiber web.

[0082] After the nonwoven fabric is cut and sealed, it is finally sterilized by cobalt-60 irradiation (dose 25 kGy) to obtain the finished product.

[0083] Example 3: This example provides a process for preparing a biodegradable nonwoven fabric, including the following steps:

[0084] 1. Raw material preparation and mixing:

[0085] According to the weight parts, the following components were weighed: 58.8 parts of polylactic acid (PLA), 25.2 parts of polycaprolactone (PCL), 5 parts of potassium periodate after ball milling, 8 parts of 1,2-cyclohexanediol-adipic acid copolyester oligomer (B-1) obtained in Preparation Example 1, and 3 parts of arginine bicarbonate.

[0086] The weighed PLA and PCL particles were dried in a vacuum drying oven at 90°C for 8 hours; potassium periodate, oligomer B-1 and arginine bicarbonate were dried in a vacuum drying oven at 80°C for 4 hours.

[0087] Place all dried materials in a high-speed mixer and mix for 10 minutes at room temperature to ensure uniform dispersion of the components.

[0088] 2. Melt blending and meltblown spinning:

[0089] The above mixture is fed evenly into a co-rotating twin-screw extruder using a loss-in-weight feeder. The temperatures of each zone of the extruder are set as follows: feed zone 180℃, compression zone 200℃, metering zone and die 210℃. The screw speed is set to 200 rpm.

[0090] After being plasticized and uniformly mixed by an extruder, the melt enters the meltblown die. The meltblown process parameters are set as follows: melt temperature 215℃, hot air temperature 230℃, hot air pressure 0.4MPa, and receiving distance 20cm. The melt stream is stretched into ultrafine fibers by high-speed hot air.

[0091] 3. Network Formation and Post-processing:

[0092] The microfibers are collected on a negative pressure suction screen and cooled to form a uniform non-woven fiber web.

[0093] The fiber web is calendered using a hot press roller with a linear pressure of 5 MPa and a temperature of 110℃.

[0094] After the nonwoven fabric is cut, sealed and packaged, it is finally sterilized with ethylene oxide to obtain the finished product.

[0095] Example 4: This example provides a process for preparing a biodegradable nonwoven fabric, including the following steps:

[0096] 1. Raw material preparation and mixing:

[0097] According to the weight proportions, the following components were weighed: 63 parts of polylactic acid (PLA), 27 parts of polycaprolactone (PCL), 3 parts of potassium periodate after ball milling, 5 parts of 1,2-cyclohexanediol-adipic acid copolyester oligomer (B-2) obtained in Preparation Example 2, and 2 parts of trisodium citrate.

[0098] The drying steps for each component are the same as in Example 1.

[0099] Place all dried materials in a high-speed mixer and mix for 15 minutes at room temperature to ensure uniform dispersion of the components.

[0100] 2. Melt blending and meltblown spinning:

[0101] The process steps and parameters are the same as in Example 1. The mixture is fed into an extruder (temperature setting: 170 / 190 / 200℃; screw speed: 150rpm), and then processed into ultrafine fibers through a meltblown system (parameter settings: melt temperature 205℃, hot air temperature 215℃, hot air pressure 0.3MPa, receiving distance 30cm).

[0102] 3. Network Formation and Post-processing:

[0103] The process steps and parameters are the same as in Example 1. The fibers are formed into a web and then subjected to hot pressing (95℃, 3MPa). Finally, they are cut, packaged, and sterilized to obtain the finished product.

[0104] Comparative Examples 1-5:

[0105] Comparative Example 1:

[0106] The difference between this comparative example and Example 1 is that the formulation does not contain potassium periodate, 1,2-cyclohexanediol-adipic acid copolyester oligomer (B-1), or arginine bicarbonate. Its formulation consists only of 70 parts polylactic acid (PLA) and 30 parts polycaprolactone (PCL), with all other preparation processes and parameters being the same as in Example 1.

[0107] Comparative Example 2:

[0108] The difference from Example 1 is that the formulation of this comparative example does not contain arginine bicarbonate as a pH regulator and catalyst. Its formulation consists of 63 parts polylactic acid (PLA), 27 parts polycaprolactone (PCL), 3 parts potassium periodate, and 5 parts 1,2-cyclohexanediol-adipic acid copolyester oligomer (B-1). All other preparation processes and parameters are the same as in Example 1.

[0109] Comparative Example 3:

[0110] The difference between this comparative example and Example 1 is that the formulation does not contain the 1,2-cyclohexanediol-adipic acid copolyester oligomer (B-1) as a reaction substrate. Its formulation consists of 63 parts polylactic acid (PLA), 27 parts polycaprolactone (PCL), 3 parts potassium periodate, and 2 parts arginine bicarbonate; the remaining preparation processes and parameters are the same as in Example 1.

[0111] Comparative Example 4:

[0112] The difference from Example 1 is that the formulation of this comparative example does not contain potassium periodate as a potential oxidizing agent. Its formulation consists of 63 parts polylactic acid (PLA), 27 parts polycaprolactone (PCL), 5 parts 1,2-cyclohexanediol-adipic acid copolyester oligomer (B-1), and 2 parts arginine bicarbonate. All other preparation processes and parameters are the same as in Example 1.

[0113] Comparative Example 5:

[0114] Compared with Example 1, the difference is that this comparative example uses a conventional antibacterial agent from the prior art instead of the self-activating antibacterial system of the present invention. Its formulation does not contain potassium periodate, 1,2-cyclohexanediol-adipic acid copolyester oligomer (B-1), or arginine bicarbonate; instead, one part of polyhexamethylene biguanide (PHMB) is added during the melt blending stage. The remaining preparation processes and parameters are the same as in Example 1.

[0115] Test Examples 1-4:

[0116] Test Example 1:

[0117] This test example aims to verify that the biodegradable nonwoven fabric prepared in the embodiments of the present invention has the functional characteristic of adjusting the pH value of the environment to a weakly alkaline range in an acidic aqueous solution environment.

[0118] The experimental steps are as follows:

[0119] 1. Solution preparation: Prepare a 0.1 mol / L phosphate buffer solution (PBS) using potassium dihydrogen phosphate and disodium hydrogen phosphate, and adjust its initial pH to 5.5 ± 0.1 using phosphoric acid to simulate an acidic microenvironment.

[0120] 2. Sample preparation: Take the nonwoven fabrics prepared in Example 1, Comparative Example 1 and Comparative Example 2 respectively, and cut them into square samples with a mass of 1.0 g under sterile conditions.

[0121] 3. Immersion Test: Place each of the above samples into a sterile beaker containing 20 mL of the above-mentioned pH 5.5 PBS solution, ensuring that the sample is completely immersed. Seal the beaker with sealing film and place it in a constant temperature environment of 37°C.

[0122] 4. pH Measurement: At five time points after the start of soaking (0, 1, 4, 8, and 24 hours), the pH value of the solution in each beaker was measured using a pH meter calibrated at three points (pH 4.01, 7.00, and 10.01). Three parallel samples were prepared for each sample group, and the average value of the results was taken.

[0123] The pH value of each sample in pH 5.5 buffer solution over time is recorded in Table 1 below.

[0124] Table 1. pH value changes of each sample over time in pH 5.5 buffer solution:

[0125]

[0126] The test data in Table 1 show that after the nonwoven fabric sample of Example 1 was immersed in an acidic buffer solution with an initial pH of 5.51, the pH of the solution rapidly increased to 7.38 within 1 hour and continued to rise over the following time, stabilizing at 8.11 after 24 hours. In contrast, the pH of the solutions containing the nonwoven fabric samples of Comparative Example 1 (blank substrate) and Comparative Example 2 (lacking pH control and catalyst) did not change significantly throughout the entire 24-hour test period, remaining consistently within the range of 5.5 to 5.7.

[0127] The above results are attributed to the presence of arginine bicarbonate in the composition of Example 1. When the nonwoven fabric comes into contact with an aqueous solution, this solid, weakly basic salt component dissolves from the polymer matrix into the solution. Its hydrolysis produces bicarbonate ions (HCO3-). - ) and hydrogen ions (H+) in the solution + A reaction occurs, and the functional groups of the arginine molecule itself also participate in proton balance, jointly consuming the acidic substances in the solution. This process transforms the acidic environment into a weakly alkaline buffer environment composed of arginine and the carbonic acid system.

[0128] The test results of Comparative Examples 1 and 2 confirm that the matrix material composed of polylactic acid and polycaprolactone, potassium periodate, and the 1,2-cyclohexanediol-adipic acid copolyester oligomer do not possess the function of adjusting the pH value of the solution. Therefore, this test clearly shows that the technical feature of adding a solid biocompatible weakly alkaline salt to the nonwoven fabric of the present invention endows the material with the functional characteristic of actively adjusting the acidic pH environment to a weakly alkaline state when in contact with an aqueous environment. This characteristic is the result of the synergistic effect of the inherent components of the material.

[0129] Test Example 2:

[0130] This test example aims to quantitatively verify that the biodegradable nonwoven fabric prepared in the embodiments of the present invention can generate and release aldehyde compounds in situ through the chemical reaction of its internal components after contact with an aqueous solution.

[0131] The experimental steps are as follows:

[0132] 1. Preparation of standard solutions and reagents:

[0133] Weigh out adipic aldehyde standard and prepare a series of standard working solutions with concentration gradients (0, 5, 10, 15, 20, 25 μg / mL) using simulated body fluid (SBF).

[0134] Prepare an MBTH (3-methyl-2-benzothiazolinone hydrazone hydrochloride) detection reagent, which is used to react with aldehyde compounds and produce a colorimetric result.

[0135] 2. Sample extraction:

[0136] Take 1.0g of each of the nonwoven fabrics prepared in Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 under sterile conditions.

[0137] Each sample was placed in a sterile container containing 20 mL of SBF solution, sealed, and placed in a constant temperature environment at 37°C for extraction.

[0138] 3. Sample collection and testing:

[0139] At 4, 8 and 24 hours after the start of extraction, 1.0 mL of extract was taken from each container.

[0140] Add MBTH detection reagent to the extracted extract and perform a colorimetric reaction according to the standard colorimetric method.

[0141] The absorbance of the solution after the reaction was measured at a wavelength of 650 nm using a UV-Vis spectrophotometer.

[0142] 4. Concentration Calculation:

[0143] Perform the same operation on the adipaldehyde standard working solution as in step 3, measure its absorbance, and plot the absorbance-concentration standard working curve.

[0144] Based on the absorbance values ​​of each sample extract, the concentration of aldehydes in the extract was calculated using a standard working curve. Three parallel samples were set up for each sample group, and the results were averaged.

[0145] The concentrations of aldehydes detected in SBF solution at different time points for each sample are recorded in Table 2 below.

[0146] Table 2. Aldehyde concentrations (μg / mL) in the extracts of each sample:

[0147]

[0148] Table 2 records the concentrations of aldehydes released by each sample in simulated body fluids. In Example 1, the concentration of aldehydes in the extract increased continuously over time after immersion, reaching 22.8 μg / mL after 24 hours. Aldehydes were also detected in the sample of Comparative Example 2, but its concentration was significantly lower than that of Example 1 at all time points, reaching only 4.1 μg / mL after 24 hours. In Comparative Examples 3 and 4, the concentration of aldehydes in the extract remained at the detection baseline throughout the entire testing period.

[0149] The above results are due to the oxidative cleavage reaction between potassium periodate (inert precursor A) and 1,2-cyclohexanediol-adipic acid copolyester oligomer (inert precursor B) inside the nonwoven fabric of Example 1 after contact with an aqueous medium, thereby generating adipaldehyde in situ. A comparison of the data from Example 1 and Comparative Example 2 directly demonstrates the function of the arginine bicarbonate component: the weakly alkaline microenvironment established by this component in Example 1 resulted in a much higher rate of aldehyde generation than that in Comparative Example 2, which was triggered only by water, confirming its accelerating effect on in-situ chemical reactions.

[0150] Comparative Example 3 (lacking precursor B) and Comparative Example 4 (lacking precursor A) tested negative, confirming that the formation of aldehydes depends on the simultaneous presence of these two precursors, which are the material basis for in-situ chemical synthesis reactions. In summary, this test case demonstrates the feasibility of the technical solution of this invention: through the combination of specific components, active substances can be synthesized in-situ along a preset chemical pathway when the material comes into contact with water, and the pH-regulating component can effectively improve the efficiency of this synthesis process.

[0151] Test Example 3:

[0152] This test case aims to quantitatively evaluate the in vitro antibacterial activity of the biodegradable nonwoven fabrics prepared in the embodiments and comparative examples of the present invention against Staphylococcus aureus and Escherichia coli.

[0153] The experimental steps are as follows:

[0154] 1. Preparation of bacterial strains and bacterial suspensions: Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 8739) were inoculated separately into nutrient broth medium and cultured at 37°C and 150 rpm for 18 hours with shaking. The logarithmic growth phase bacterial suspension was diluted with phosphate-buffered saline (PBS) to adjust the concentration to 1 × 10⁻⁶. 5 -1×10 6CFU / mL was used as the bacterial suspension for testing.

[0155] 2. Sample preparation: Take the nonwoven fabrics prepared in Examples 1-4 and Comparative Examples 1-5 respectively, and cut them into samples with a mass of 0.4 g under sterile conditions.

[0156] 3. Co-culture test: Place each of the above samples into a sterile conical flask containing 20 mL of the bacterial suspension to be tested.

[0157] 4. Shaking culture: After sealing all the conical flasks, place them in a constant temperature shaking incubator at 37℃ and 150rpm for a total of 24 hours.

[0158] 5. Viable cell count: After cultivation, take 1 mL of bacterial solution from each Erlenmeyer flask and perform 10-fold serial dilutions with PBS. Take 100 μL of the appropriately diluted bacterial solution and spread it evenly on a nutrient agar plate. Incubate the plate upside down in a 37°C incubator for 24 hours, and then count the colonies on the plate.

[0159] 6. Antibacterial rate calculation: Using Comparative Example 1 (blank substrate) as the negative control group, the antibacterial rate of each sample against the two strains was calculated according to the following formula. Three parallel samples were set up for each sample group, and the results were averaged. Antibacterial rate (%) = [(number of viable bacteria in the control group - number of viable bacteria in the experimental group) / number of viable bacteria in the control group] × 100%.

[0160] The antibacterial rate data of each sample against the two test strains are recorded in Table 3 below.

[0161] Table 3. Antibacterial rates of each sample against Staphylococcus aureus and Escherichia coli:

[0162]

[0163] Table 3 records the antibacterial rates of each sample against Staphylococcus aureus and Escherichia coli. The nonwoven fabrics prepared in Examples 1, 2, 3, and 4 all exhibited antibacterial rates higher than 99.7% against both test strains, with Examples 1, 3, and 4 showing antibacterial rates higher than 99.9%. As controls, the antibacterial rates of Comparative Example 1 (blank substrate), Comparative Example 3 (lacking oligomers), and Comparative Example 4 (lacking potassium periodate) were all below 5.0%. The antibacterial rate of Comparative Example 2 (lacking arginine bicarbonate) ranged from 61.2% to 65.7%. Comparative Example 5 (containing PHMB) showed antibacterial rates of 99.53% and 99.21% against the two strains, respectively.

[0164] The above results confirm the antibacterial effectiveness of the technical solution of the present invention. The high antibacterial rate of Examples 1-4 originates from the aldehyde compounds generated in situ in an aqueous environment, which inhibit the physiological activity of bacteria by reacting with bacterial proteins. The test results of Comparative Examples 3 and 4 are close to the blank control, which clearly indicates that the realization of antibacterial function depends on the co-existence of two precursor components: potassium periodate and 1,2-cyclohexanediol-adipic acid copolyester oligomer. These two components are the material basis for the chemical reaction that generates antibacterial substances in situ.

[0165] The difference in antibacterial rate data between Example 1 and Comparative Example 2 reveals the function of pH regulation and the catalyst component. In Comparative Example 2, which lacks this component, the antibacterial rate of the material is significantly lower than that of Example 1, which includes this component. This result corresponds to the data on the aldehyde formation rate in Test Example 2, demonstrating that the weakly alkaline environment established by arginine bicarbonate improves the formation efficiency of antibacterial substances by accelerating in-situ chemical reactions, thereby resulting in higher antibacterial activity in the material. Furthermore, the data shows that even Example 2, which uses a lower component content (antibacterial rate of 99.75%–99.81%), has a higher antibacterial rate than Comparative Example 5, which uses a conventional antibacterial agent (antibacterial rate of 99.21%–99.53%), confirming the effectiveness of this technical solution.

[0166] Test Example 4:

[0167] This test case aims to evaluate the in vitro cytotoxicity of the extracts of the biodegradable nonwoven fabrics prepared in the embodiments and comparative examples of the present invention to L929 fibroblasts using the MTT assay, in accordance with ISO 10993-5:2009 standard.

[0168] The experimental steps are as follows:

[0169] 1. Preparation of extract:

[0170] The nonwoven fabrics prepared in Examples 1-4 and Comparative Examples 1-5 were taken respectively and added to a sterile container containing high-sugar DMEM complete medium (containing 10% fetal bovine serum and 1% penicillin-streptomycin) at a ratio of 0.2 g / mL (material weight / culture medium volume) under sterile conditions.

[0171] Place the container in a cell culture incubator at 37°C and 5% CO2 for 24 hours for extraction.

[0172] After extraction, the extract was sterilized by filtration through a 0.22 μm filter to obtain extracts for each sample. Meanwhile, complete culture medium without the sample was used as a negative control, and complete culture medium containing 0.1% phenol was used as a positive control.

[0173] 2. Cell Culture and Seeding: L929 mouse fibroblasts in logarithmic growth phase were digested and counted. After adjusting the cell density, they were seeded into 96-well cell culture plates at a density of 5 × 10⁶ cells per well. 3 One cell was placed in a cell culture incubator at 37°C and 5% CO2 for 24 hours until the cells were fully adhered to the incubator.

[0174] 3. Cell treatment: Remove the original culture medium from the 96-well plate, and add 100 μL of the prepared sample extract, negative control solution, and positive control solution to each well. Set up 6 replicates for each group.

[0175] 4. MTT assay: Return the culture plate to the incubator and continue incubation for 24 hours. Then, add 20 μL of 5 mg / mL MTT solution to each well and continue incubation for 4 hours. After incubation, carefully aspirate the liquid from the wells and add 150 μL of dimethyl sulfoxide (DMSO) to each well. Shake slowly on a shaker for 10 minutes to completely dissolve the formazan crystals.

[0176] 5. Data Acquisition and Calculation: The absorbance (OD value) of each well was measured at a wavelength of 490 nm using a microplate reader. The relative cell proliferation rate (RGR) was calculated using the following formula: RGR(%) = (OD value of experimental group / OD value of negative control group) × 100%;

[0177] The relative cell proliferation rate (RGR) and cytotoxicity grade of each sample after treatment with extract are recorded in Table 4 below. Cytotoxicity grading criteria: RGR≥100%, Grade 0; 75%≤RGR<100%, Grade 1; 50%≤RGR<75%, Grade 2; 25%≤RGR<50%, Grade 3; RGR<25%, Grade 4.

[0178] Table 4. Relative cell proliferation rate (RGR) and cytotoxicity grade of extracts for each sample:

[0179]

[0180] Table 4 shows that after treatment with the extracts of Examples 1, 2, 3, and 4, the relative cell growth rate (RGR) was above 88%, corresponding to a cytotoxicity grade of 1. The RGR values ​​of Comparative Examples 1, 2, 3, and 4 were also above 92%, with a toxicity grade of 1. In contrast, the RGR value of Comparative Example 5 was 68.4%, corresponding to a cytotoxicity grade of 2. The RGR value of the positive control group was 18.7%, exhibiting grade 4 toxicity.

[0181] The above results indicate that the nonwoven fabric compositions of Examples 1-4, containing potassium periodate, oligomers, and pH adjusters, did not cause significant cytotoxicity in their extracts. The mechanism of action lies in the fact that the active antibacterial substances are generated in situ through chemical reactions upon contact with the material in an aqueous environment, and their concentration is regulated by reaction kinetics. The reactants exist in solid form within the polymer matrix, avoiding the initial explosive release of high concentrations of active substances. This on-demand generation and controlled release mechanism results in low overall cytotoxicity of the material.

[0182] Comparative Example 5 showed an RGR value of 68.4%, indicating grade 2 (mild) cytotoxicity. Analysis of this data in conjunction with the antibacterial rate data of Test Example 3 shows that Comparative Example 5, which directly added the conventional antibacterial agent PHMB, achieved comparable antibacterial activity to the examples while exhibiting a higher cytotoxicity level. In contrast, the technical solutions of Examples 1-4 achieved an antibacterial rate exceeding 99.7% while maintaining a grade 1 cytotoxicity. This comparison confirms that the technical solution of this invention, through the in-situ generation of active substances from latent precursors under specific conditions, can achieve an effective balance between the antibacterial functionality and biocompatibility of materials.

[0183] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A biodegradable nonwoven fabric, characterized in that, The nonwoven fabric is made of components comprising the following parts by weight: Polylactic acid: 58-68 parts; Polycaprolactone: 25-29 parts; Periodate: 1-5 parts; Copolyester oligomers containing cis-1,2-cyclohexanediol structural units: 2 to 8 parts; Solid biocompatible weakly alkaline salt: 1-3 parts.

2. The biodegradable nonwoven fabric according to claim 1, characterized in that, The nonwoven fabric is made of components comprising the following parts by weight: Polylactic acid: 60-65 parts; Polycaprolactone: 25-30 parts; Periodate: 2-4 parts; Copolyester oligomers containing cis-1,2-cyclohexanediol structural units: 4 to 6 parts; Solid biocompatible weakly alkaline salt: 1.5–2.5 parts.

3. The biodegradable nonwoven fabric according to claim 1, characterized in that, The copolyester oligomer containing cis-1,2-cyclohexanediol structural units is prepared by polycondensation reaction of cis-1,2-cyclohexanediol and adipic acid, and its number average molecular weight is 1500-5000 g / mol.

4. The biodegradable nonwoven fabric according to claim 1, characterized in that, The solid biocompatible weakly basic salt is arginine bicarbonate and / or trisodium citrate.

5. The biodegradable nonwoven fabric according to claim 1, characterized in that, The periodate is potassium periodate.

6. A process for preparing the biodegradable nonwoven fabric as described in any one of claims 1-5, characterized in that, Includes the following steps: Polylactic acid, polycaprolactone, periodate, copolyester oligomer containing cis-1,2-cyclohexanediol structural units, and solid biocompatible weakly basic salt are mixed to obtain a mixture. The mixture is melt-blended and melt-blown spun to obtain ultrafine fibers; The ultrafine fibers are collected into a web to obtain a nonwoven fabric.

7. The preparation process according to claim 6, characterized in that, Prior to mixing, the periodate is subjected to a ball milling process.

8. The preparation process according to claim 6, characterized in that, In the steps of melt blending and meltblown spinning, the melt temperature is 195-215℃ and the hot air temperature is 200-230℃.

9. The preparation process according to claim 8, characterized in that, The melt blending step is carried out in a twin-screw extruder, wherein the metering zone and die temperature of the extruder are 190–210°C, and the screw speed is 100–200 rpm.

10. The preparation process according to claim 6, characterized in that, After the nonwoven fabric is collected into a web, the process also includes a hot-pressing treatment of the nonwoven fabric at a temperature of 95–110°C.

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