Biodegradable medical gauze based on plant fibers and its production process

Abstract

This invention relates to the field of medical materials technology, and discloses a biodegradable medical gauze based on plant fibers and its production process. The medical gauze is made from raw materials comprising the following parts by weight: 5-15 parts plant fiber; 0.5-2.0 parts tannic acid; 0.1-1.0 parts boric acid; and 100 parts 1-allyl-3-methylimidazolium chloride. The production process includes: dissolving the above raw materials in an ionic liquid to form a homogeneous solution, coating it into a film, then performing a coagulation and regeneration treatment in an alcohol-water solution, controlling the residual amount of ionic liquid in the final product, and finally drying. This invention achieves long-term functional stability by controlling a portion of the residual ionic liquid as an internal plasticizer during the coagulation step, while simultaneously embedding the antibacterial component tannic acid within the cellulose matrix. This solves the problems of rigidity and easy detachment of functional components in traditional regenerated cellulose materials. The resulting gauze possesses biodegradability, flexibility, and long-lasting antibacterial properties.

Description

Technical Field

[0001] This invention relates to the field of medical materials technology, specifically to biodegradable medical gauze based on plant fibers and its production process. Background Technology

[0002] Medical gauze, as one of the most commonly used wound dressings, directly affects the wound healing process. While traditional cotton gauze is widely used, its function is limited, and it can adhere to the wound upon contact. To overcome these shortcomings, developing novel medical dressings with additional functions such as biodegradability and antibacterial properties has become a key research focus in this field.

[0003] Plant cellulose, as the most abundant renewable natural polymer on Earth, is considered an ideal substrate for preparing novel medical materials due to its excellent biocompatibility and biodegradability. Regenerated cellulose membranes or fibers can be prepared by dissolving it in specific solvents (such as ionic liquids). However, this technological approach still faces significant technical bottlenecks when applied to medical gauze.

[0004] First, after drying, pure regenerated cellulose materials form a dense network of hydrogen bonds between their molecular chains. This results in a final product that is typically rigid, lacks flexibility, and feels like paper, failing to meet the basic requirements for medical gauze to fit snugly and comfortably against the body. To improve its flexibility, exogenous small-molecule plasticizers such as glycerin are usually added. However, these plasticizers are prone to migration and loss during long-term storage or use, which may not only affect the biocompatibility of the material but also lead to a loss of flexibility.

[0005] Secondly, to impart antibacterial and other bioactive functions to regenerated cellulose gauze, existing technologies generally employ surface treatment methods, such as impregnation, coating, or spraying with antibacterial agents. The drawback of this method is that the antibacterial components adhere to the material surface only through physical adsorption or weak chemical forces. In practical use, contact with wound exudate, physical friction, or the cleaning process can easily lead to the rapid detachment and loss of functional components, significantly reducing the durability and stability of its antibacterial effect, making it difficult to achieve long-term wound protection.

[0006] Therefore, how to develop a technical solution that can simultaneously solve the two core problems of intrinsic rigidity and poor stability of functional components in regenerated cellulose materials, so as to prepare biodegradable medical gauze with both excellent flexibility and long-lasting antibacterial properties, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides biodegradable medical gauze based on plant fibers and its production process, solving the problems that traditional regenerated cellulose materials are unsuitable for medical dressings due to their lack of inherent flexibility, as well as the insufficient stability and easy shedding of functional components in the material.

[0008] In a first aspect, this application provides a biodegradable medical gauze based on plant fibers, employing the following technical solution:

[0009] Biodegradable medical gauze based on plant fibers is made from raw materials comprising the following parts by weight:

[0010] 5-15 parts plant fiber; 0.5-2.0 parts tannic acid; 0.1-1.0 parts boric acid; 100 parts 1-allyl-3-methylimidazolium chloride.

[0011] By employing the above-mentioned technical solution, the preparation process of this medical gauze utilizes 1-allyl-3-methylimidazolium chloride as a solvent to dissolve and regenerate plant fibers, constructing the basic framework of the medical gauze. The introduction of tannic acid endows the gauze with antibacterial activity; its phenolic hydroxyl structure can bind to bacterial proteins or disrupt cell membrane integrity, effectively inhibiting microorganisms. Boric acid, as a cross-linking component, can complex or esterify with the ortho- and tho-diphenolic hydroxyl groups of tannic acid or the hydroxyl groups of cellulose. During cellulose regeneration, tannic acid molecules are physically embedded and fixed within the newly formed three-dimensional cellulose network framework. This integrated strategy simultaneously introduces functional components and constructs the material's bulk structure, realizing a transformation from traditional surface loading to bulk embedding of functional components. Furthermore, by precisely controlling the incomplete replacement of ionic liquids during the coagulation and regeneration step, a specific amount of 1-allyl-3-methylimidazolium chloride molecules is retained within the material matrix. These retained ionic liquid molecules form physical spaces between the regenerated cellulose macromolecular chains, effectively preventing the cellulose molecular chains from getting too close together and forming a large number of hydrogen bonds during the drying process. This inhibits the dense packing of the material and endows the regenerated cellulose matrix with inherent flexibility. Therefore, this medical gauze has biodegradability, high-efficiency antibacterial properties, excellent functional stability, and good flexibility.

[0012] Preferably, the plant fiber is cotton stalk fiber or bamboo pulp.

[0013] By adopting the above technical solution, the medical gauze can effectively utilize agricultural and forestry waste, realize resource utilization, reduce material costs, and ensure the wide availability of bio-based materials.

[0014] Preferably, the gauze contains 2.5-4.5% by mass of 1-allyl-3-methylimidazolium chloride.

[0015] By adopting the above technical solution, the residual amount of ionic liquid is precisely controlled and acts as a plasticizer at the molecular level, effectively adjusting the mechanical properties of regenerated cellulose material. This avoids the material becoming too rigid and losing the flexibility required for medical dressings after the ionic liquid is completely removed, thus enabling the gauze to conform to the curves of the body surface.

[0016] Preferably, the 1-allyl-3-methylimidazolium chloride is prepared by reacting N-methylimidazolium with allyl chloride at 60±5°C for 36 hours.

[0017] By adopting the above technical solution, it is possible to ensure that the ionic liquid used to prepare medical gauze has a clear chemical structure and purity, which provides a foundation for the preparation and performance stability of subsequent materials.

[0018] Secondly, this application provides a production process for biodegradable medical gauze based on plant fibers, employing the following technical solution:

[0019] The production process of biodegradable medical gauze based on plant fibers includes the following steps:

[0020] (a) Add plant fiber, tannic acid and boric acid to 1-allyl-3-methylimidazolium chloride, heat and stir until a homogeneous solution is formed;

[0021] (b) Coat the homogeneous solution obtained in step (a) into a film;

[0022] (c) The membrane obtained in step (b) is immersed in an alcohol-water solution for coagulation and regeneration treatment to control the residual amount of the 1-allyl-3-methylimidazolium chloride in the final product;

[0023] (d) Dry the coagulated and regenerated gauze.

[0024] By employing the above technical solution, this process integrates the dissolution of plant fibers, the introduction of functional components (tannic acid and boric acid), and the regeneration and fixation of cellulose with the functional components. In step (a), the dissolution of plant fibers and the mixing of functional components occur within an ionic liquid system, ensuring that tannic acid and boric acid are uniformly dispersed at the molecular level and fully contacted with the dissolved cellulose. In step (c), by precisely adjusting the coagulation and regeneration conditions (such as the concentration, temperature, and time of the alcohol-water solution), not only is the regeneration and shaping of cellulose achieved, but more importantly, by controlling the degree of ionic liquid replacement, controllable residue of the ionic liquid within the material matrix is ​​achieved, thereby endowing the material with lasting flexibility while forming its structure. This process avoids the problem of functional components merely adhering to the surface and easily detaching in traditional impregnation methods, fundamentally solving the technical defect of insufficient functional durability, and obtaining medical gauze with functional components embedded in the bulk and exhibiting stable performance.

[0025] Preferably, in step (a), the heating and stirring temperature is 90-110°C and the time is 2-6 hours.

[0026] By adopting the above technical solution, the temperature and time range can ensure the full dissolution of plant fibers in ionic liquid, while promoting the uniform dispersion and initial reaction of tannic acid and boric acid, forming a stable homogeneous spinning solution, and providing a stable precursor for subsequent film formation.

[0027] Preferably, in step (b), the homogeneous solution is coated into a wet film with a thickness of 200-800 μm.

[0028] By adopting the above technical solutions and precisely controlling the thickness of the wet film, the mass transfer rate and the formation of the internal microstructure of the material during the coagulation and regeneration process can be affected, thereby regulating the porosity and mechanical strength of the final gauze and ensuring that the product meets the requirements of medical dressings in terms of thickness and physical properties.

[0029] Preferably, after step (b) and before step (c), the method further includes a step of heat-treating the membrane at 60-80°C for 10-30 minutes.

[0030] By adopting the above technical solution, this heat treatment step can promote the initial orientation of cellulose molecular chains and stabilize the interaction between tannic acid and cellulose or boric acid to a certain extent, providing a membrane with a certain pre-organized structure for the subsequent coagulation and regeneration process, which helps to improve the mechanical properties and structural uniformity of the final gauze.

[0031] Preferably, in step (c), the alcohol-water solution is an ethanol-water solution with a volume fraction of 10-50%, and the coagulation and regeneration treatment temperature is 15-30°C, and the time is 5-20 minutes.

[0032] By adopting the above technical solution, the coagulation and regeneration conditions can effectively control the diffusion rate of ionic liquid and the regeneration speed of cellulose, thereby precisely controlling the microstructure, pore structure and final residual amount of ionic liquid of regenerated cellulose to obtain gauze with specific flexibility and antibacterial properties.

[0033] Preferably, in step (d), the drying is vacuum freeze drying.

[0034] By adopting the above technical solution, vacuum freeze-drying technology can preserve the porous structure inside the gauze to the greatest extent, avoid the pore collapse and material shrinkage that may be caused by traditional heat drying, and thus maintain the good moisture absorption and softness of the gauze.

[0035] This invention provides a biodegradable medical gauze based on plant fibers and its production process. It has the following beneficial effects:

[0036] 1. The medical gauze provided by this invention possesses excellent and lasting flexibility. This effect is achieved by precisely controlling the degree of replacement of 1-allyl-3-methylimidazolium chloride, used as a solvent, during the coagulation and regeneration step, resulting in a residual mass fraction of 2.5-4.5% in the final product. These residual ionic liquid molecules act as physical separators and plasticizers between the regenerated cellulose macromolecular chains, effectively preventing excessive aggregation and rigidity of cellulose molecules during drying due to the formation of numerous hydrogen bonds. This endows the material with inherent, non-added, soft properties, enabling it to conform well to the wound surface.

[0037] 2. The medical gauze prepared by this invention possesses stable and long-lasting antibacterial properties. The process of this invention involves adding the antibacterial component tannic acid and the cross-linking fixing component boric acid to the ionic liquid system during the plant fiber dissolution stage. In the subsequent coagulation and regeneration steps, as the cellulose skeleton reforms, the tannic acid and boric acid are physically embedded and fixed within the three-dimensional network structure. Compared to traditional surface impregnation or coating processes, this bulk embedding method fundamentally avoids the problem of easy loss of antibacterial components due to washing and friction, ensuring the long-term effectiveness of the gauze's function in actual use.

[0038] 3. The production process of this invention is simplified and achieves effective utilization of agricultural and forestry waste. This process integrates the dissolution of plant fibers (such as cotton stalks and bamboo pulp), the introduction of functional components, and the molding and regeneration of materials, eliminating the multiple post-processing, impregnation, and drying steps required in the preparation of traditional functional dressings, thus shortening the production cycle. At the same time, using widely available and low-cost cotton stalk fibers or bamboo pulp as the main raw materials provides an economically feasible approach for the preparation of high-value-added medical materials. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, comparative examples, and examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] Preparation Example 1: Preparation of the ionic liquid 1-allyl-3-methylimidazolium chloride ([AMIM]Cl)

[0041] The ionic liquid 1-allyl-3-methylimidazolium chloride ([AMIM]Cl) used in the embodiments of the present invention can be a commercially available product or can be prepared by the method disclosed in this preparation example.

[0042] In a 500 mL three-necked flask equipped with a reflux condenser, magnetic stirrer, and thermometer, 1.0 mol (82.10 g) of N-methylimidazole was added. Under ice-water bath cooling and continuous stirring, 1.1 mol (84.19 g) of allyl chloride was slowly added dropwise through a constant-pressure dropping funnel, controlling the dropping rate to maintain the reaction system temperature below 30 °C. After the addition was complete, the ice-water bath was removed, and the reaction system was heated in a constant-temperature oil bath at 60 ± 5 °C for 36 hours.

[0043] After the reaction is complete, stop heating and allow the reaction mixture to cool naturally to room temperature. Add 200 mL of ethyl acetate to the flask, stir vigorously for 30 minutes, and allow to stand to separate into layers. Discard the upper ethyl acetate phase. Repeat this washing step three times to thoroughly remove unreacted starting materials.

[0044] The viscous liquid product obtained from the lower layer was transferred to a rotary evaporator and subjected to vacuum distillation at 80 °C and a vacuum degree below 100 Pa to completely remove residual ethyl acetate and other low-boiling-point impurities. A final yield of 139.5 g of colorless, transparent, viscous liquid, the target product 1-allyl-3-methylimidazolium chloride ([AMIM]Cl), was obtained, with a yield of approximately 95%. The product was stored in a vacuum desiccator for later use.

[0045] Examples 1-4:

[0046] Example 1: 100 parts by weight of 1-allyl-3-methylimidazolium chloride ([AMIM]Cl) were added to a reactor equipped with a mechanical stirrer and a heating mantle, and the mixture was heated to 90°C.

[0047] While stirring, add 5 parts by weight of pretreated cotton stalk fiber powder, 0.5 parts by weight of tannic acid, and 0.1 parts by weight of boric acid. Continue stirring at 90°C for 2 hours until a homogeneous, clear, brown viscous solution is formed.

[0048] The above solution was kept at 80°C and coated onto a polytetrafluoroethylene plate with a thickness of 200 μm using a doctor blade coater.

[0049] Place the polytetrafluoroethylene plate with the wet film in a constant temperature oven at 60°C and heat treat for 10 minutes.

[0050] The board with the gel film was immersed in a 10% ethanol aqueous solution and subjected to coagulation and regeneration treatment at 15°C for 5 minutes to separate the gel gauze from the board.

[0051] Remove the gelled gauze, rinse it quickly with deionized water, place it in a vacuum freeze dryer, pre-freeze it at -40℃ for 2 hours, and then dry it for 24 hours at a shelf temperature of 10℃ and a vacuum degree of less than 50 Pa.

[0052] After drying, a soft, light brown porous gauze is obtained.

[0053] Example 2: 100 parts by weight of [AMIM]Cl were added to a reactor equipped with a mechanical stirrer and a heating mantle, and the mixture was heated to 100°C.

[0054] While stirring, add 10 parts by weight of pretreated cotton stalk fiber powder, 1.2 parts by weight of tannic acid, and 0.5 parts by weight of boric acid. Continue stirring at 100°C for 4 hours until a homogeneous, clear, brown viscous solution is formed.

[0055] The above solution was kept at 90°C and coated onto a polytetrafluoroethylene plate with a thickness of 500 μm using a doctor blade coater.

[0056] Place the polytetrafluoroethylene plate with the wet film in a constant temperature oven at 70°C and heat treat for 20 minutes.

[0057] The board with the gel film was immersed in a 30% ethanol aqueous solution and subjected to coagulation and regeneration treatment at 25°C for 12 minutes to separate the gel gauze from the board.

[0058] Remove the gelled gauze, rinse it quickly with deionized water, place it in a vacuum freeze dryer, pre-freeze it at -40℃ for 2 hours, and then dry it for 36 hours at a shelf temperature of 10℃ and a vacuum degree of less than 50 Pa.

[0059] After drying, a soft, brown porous gauze product is obtained.

[0060] Example 3: 100 parts by weight of [AMIM]Cl were added to a reactor equipped with a mechanical stirrer and a heating mantle, and the mixture was heated to 110°C.

[0061] While stirring, add 15 parts by weight of pretreated cotton stalk fiber powder, 2.0 parts by weight of tannic acid, and 1.0 parts by weight of boric acid. Continue stirring at 110°C for 6 hours until a homogeneous, clear, brown viscous solution is formed.

[0062] The above solution was kept at 100°C and coated onto a polytetrafluoroethylene plate with a thickness of 800 μm using a doctor blade coater.

[0063] Place the polytetrafluoroethylene plate with the wet film in a constant temperature oven at 80°C and heat treat for 30 minutes.

[0064] The board with the gel film was immersed in a 50% ethanol aqueous solution and subjected to coagulation and regeneration treatment at 30°C for 20 minutes to separate the gelled gauze from the board.

[0065] Remove the gelled gauze, rinse it quickly with deionized water, place it in a vacuum freeze dryer, pre-freeze it at -40℃ for 2 hours, and then dry it for 48 hours at a shelf temperature of 10℃ and a vacuum degree of less than 50 Pa.

[0066] After drying, a soft, dark brown porous gauze is obtained.

[0067] Example 4: This example aims to illustrate the applicability of the method of the present invention to plant fibers from different sources.

[0068] The component ratios and process parameters used in this embodiment are the same as those in Embodiment 2. The only difference is that the plant fiber raw material used in step 2 is replaced by "10 parts by weight of pretreated cotton stalk fiber powder" with "10 parts by weight of pretreated bamboo pulp powder".

[0069] The remaining operating steps are completely consistent with those in Example 2. After drying, a soft, brown porous gauze product is obtained.

[0070] Comparative Examples 1-4:

[0071] Comparative Example 1:

[0072] The difference from Example 2 is that 0.5 parts by weight of boric acid is not added in step 2. All other component ratios and process parameters are the same as in Example 2.

[0073] Comparative Example 2:

[0074] The difference from Example 2 is that 1.2 parts by weight of tannic acid are not added in step 2. The remaining component ratios and process parameters are the same as in Example 2.

[0075] Comparative Example 3:

[0076] The difference from Example 2 is that the solidification and regeneration conditions in step 5 were changed in order to completely remove the ionic liquid.

[0077] The specific procedure is as follows: Immerse the board with the gel film in pure deionized water at 25°C for 60 minutes, changing the deionized water every 15 minutes during this period, for a total of 3 changes. All other process parameters are the same as in Example 2.

[0078] Comparative Example 4:

[0079] This comparative example uses a traditional impregnation and coating method to prepare medical gauze, in order to compare the effect of the integrated process of the present invention.

[0080] The specific steps are as follows: Take commercially available regenerated cellulose gauze (viscose fiber gauze) with a mass equivalent to that used in Example 2; dissolve 1.2 parts by mass of tannic acid and 0.5 parts by mass of boric acid in 100 parts by mass of deionized water to prepare a treatment solution; immerse the gauze in the treatment solution for 2 hours, remove it, remove excess liquid by rollers, and finally dry it in an oven at 70°C to constant weight.

[0081] Test Example 1-3:

[0082] Test Example 1: Comprehensive Physical Performance Test

[0083] To objectively evaluate the physical properties of the samples prepared in the embodiments and comparative examples of the present invention, the following tests were conducted.

[0084] (1) Mechanical property testing procedures

[0085] According to the national standard GB / T 3923.1-2013, a universal testing machine was used to test the samples. First, the dried samples prepared in Examples 1-4 and Comparative Examples 1-4 were conditioned for 24 hours under standard atmospheric conditions of 20±2℃ and 65±5% relative humidity. Then, each sample was cut into strips with a width of 10 mm and a length of 80 mm. The clamping distance of the testing machine was set to 50 mm, and the tensile rate to 50 mm / min. One set of strips was directly stretched, and its dry tensile strength and elongation at break were recorded. Another set of strips was completely immersed in deionized water for 1 hour, and after removal, excess surface moisture was absorbed with filter paper. The samples were immediately tested with the same parameters, and their wet tensile strength and elongation at break were recorded. At least five strips were tested for each group of samples, and the average value was taken.

[0086] (2) Liquid absorption performance test procedure

[0087] The tests were conducted according to standard YY / T 0472-2020. Samples prepared in Examples 1-4 and Comparative Examples 1-4 were cut into 50 mm × 50 mm cubes, dried to constant weight in a 60℃ oven, and their dry weight (Wd) was accurately measured. The samples were completely immersed in a 0.9% (w / v) physiological saline solution and allowed to stand for 30 minutes. The samples were then removed from the solution using tweezers and suspended vertically for 1 minute to allow unabsorbed liquid to drip off naturally. The wet weight (Ww) of the samples was immediately measured. The absorption rate of the samples was calculated using the formula: Absorption Ratio = (Ww - Wd) / Wd. Three parallel samples were tested for each group of samples, and the average value was taken.

[0088] (3) Flexibility test procedure

[0089] The stiffness test was conducted using a cantilever inclined plane method according to standard GB / T 18318.1-2009. Samples prepared in Examples 1-4 and Comparative Examples 1-4 were cut into strips with a width of 25 mm and a length of 150 mm. The strips were placed on the horizontal platform of the instrument, with one end aligned with the edge of the platform. The strips were slowly pushed, causing them to bend along a 41.5° inclined plane under their own weight. When the free end of the strip contacted the inclined plane, the length extending from the horizontal platform was recorded; this length is the bending length. The smaller the bending length, the more flexible the material. Five strips were tested for each group of samples, and the average value was taken.

[0090] Table 1. Physical property test data of the examples and comparative samples

[0091]

[0092] Results analysis:

[0093] The test results in Table 1 show that the medical gauze prepared by this invention possesses excellent comprehensive physical properties. A comparison of the data from Example 2 and Comparative Example 1 clearly reveals the structural support role of the dynamic cross-linking network. Comparative Example 1, in the absence of boric acid, exhibits a wet tensile breaking strength of only 1.8 MPa, far lower than the 12.1 MPa of Example 2. This is because in the system of Example 2, boric acid forms dynamic covalent bonds of borate esters with the polyol hydroxyl groups on the plant fiber and tannic acid molecular chains. These chemical bonds constitute a stable three-dimensional network between molecular chains, effectively resisting the disruption of intermolecular hydrogen bonds by water molecule intrusion, thereby maintaining the structural integrity and mechanical strength of the material in a wet state.

[0094] A comparison of the data from Example 2 and Comparative Example 3 confirms the decisive influence of the controllable solvent retention process on the material's flexibility. Comparative Example 3, which removed the ionic liquid through prolonged washing, achieved a bending length of 55.4 mm, significantly higher than the 25.1 mm of Example 2, indicating a much stiffer material. The mechanism lies in the fact that the residual ionic liquid molecules in the finished product of Example 2 act as an in-situ plasticizer during the drying process, occupying the space between the cellulose molecular chains and physically preventing the chains from becoming too close together due to dehydration, thus preventing the formation of a large number of rigid hydrogen bond networks. This molecular-level steric hindrance effect makes the final material's internal structure more porous, thereby exhibiting excellent flexibility.

[0095] A comprehensive comparison of Example 2 with all comparative examples, particularly Comparative Example 4 which employed a conventional post-processing technique, reveals that the technical effect of this invention is not a simple superposition of the functions of each component, but rather stems from the synergistic effect of various technical features within an integrated process. By homogeneously compounding plant fibers, functional components, and dynamic crosslinking agents at the molecular level, followed by in-situ regeneration and plasticizing, the prepared material maintains high liquid absorbency while also possessing high wet strength and high flexibility. This combination of properties is unattainable by any comparative example lacking key components or employing a non-integrated process, demonstrating the completeness and advancement of the technical solution of this invention.

[0096] Test Example 2: Antibacterial Properties and Functional Stability Test

[0097] This test case aims to evaluate the antibacterial activity of each sample and to examine the impact of the integrated process of this invention on the stability of functional component loading.

[0098] Experimental steps:

[0099] (1) Initial antibacterial performance test

[0100] The procedure was performed in accordance with the national standard GB / T 20944.3-2008 (oscillation method).

[0101] Bacterial activation and suspension preparation: *Escherichia coli* (ATCC 8739) and *Staphylococcus aureus* (ATCC 6538) were inoculated separately into nutrient broth medium and cultured with shaking at 37°C and 150 rpm for 18-24 hours. The logarithmic-phase bacterial suspension was then diluted with phosphate-buffered saline (PBS, pH 7.2-7.4) to adjust the bacterial concentration to 1.0 × 10⁻⁶. 5 - 5.0×10 5 CFU / mL.

[0102] Sample inoculation: Accurately weigh 0.75 g of samples from Examples 1-4 and Comparative Examples 1-4, sterilize with ethylene oxide, and place them into 250 mL Erlenmeyer flasks containing 70 mL of PBS. Add 1.0 mL of the prepared bacterial suspension to each Erlenmeyer flask.

[0103] Control group setup: Add the same volume of PBS and bacterial suspension to an Erlenmeyer flask that does not contain the sample to serve as a blank control.

[0104] Shaking culture: Place all conical flasks in a constant temperature shaker at 37℃ and 150 rpm and shake for 24 hours.

[0105] Viable cell count: After cultivation, take 1.0 mL of solution from each Erlenmeyer flask and perform 10-fold serial dilutions. Spread 100 μL of the appropriately diluted bacterial solution onto a nutrient agar plate. Incubate the plates at 37°C for 24 hours, then count the colonies.

[0106] Antibacterial inhibition rate calculation: The antibacterial inhibition rate (%) is calculated according to the formula: [(B - A) / B] × 100. Where A is the average viable bacterial concentration (CFU / mL) of the sample group after culture, and B is the average viable bacterial concentration (CFU / mL) of the blank control group after culture.

[0107] (2) Functional stability (wash resistance) test

[0108] To accurately compare the differences in functional component loading stability between the integrated process of the present invention and the traditional impregnation process, this test item only selects Example 2 as the representative of the process of the present invention, and selects Comparative Example 4 as the representative of the traditional process for testing.

[0109] Washing treatment: Take one set of samples from Example 2 and Comparative Example 4, weigh them accurately, and place them in sterile conical flasks. Add sterile physiological saline at a material-to-liquid ratio of 1:100 (g / mL). Place the conical flasks on a shaker at room temperature and shake slowly at 100 rpm for 24 hours.

[0110] Antibacterial performance test after washing: Under aseptic conditions, the washed sample was taken out and rinsed quickly with a small amount of sterile deionized water to remove surface salt. Then, the antibacterial performance test was carried out on the washed sample in accordance with steps 2 to 6 of “(1) Initial antibacterial performance test” to obtain the antibacterial rate after washing.

[0111] Table 2. Test data on antibacterial properties and functional stability of the examples and comparative samples

[0112]

[0113] Results analysis:

[0114] Table 2 provides a clear picture of the source of the material's antibacterial activity and the stability of its function. A comparison of the test results of Example 2 and Comparative Example 2 clearly indicates that the material's high antibacterial activity originates from the introduction of tannic acid. Comparative Example 2, lacking tannic acid, had an inhibition rate of less than 15% and therefore lacked effective antibacterial function. In Example 2, the numerous phenolic hydroxyl groups in the tannic acid molecule can denature and inactivate bacterial proteins through hydrogen bonding or hydrophobic interactions, and can also disrupt the integrity of the cell membrane, thereby achieving highly efficient inhibition against *Escherichia coli* and *Staphylococcus aureus*.

[0115] The wash resistance test results of Example 2 and Comparative Example 4 reveal the core advantage of the integrated process of the present invention in terms of functional component loading stability. After 24 hours of agitation washing, the antibacterial rate of the sample in Example 2 remained above 99%, demonstrating extremely high functional durability. In contrast, Comparative Example 4, prepared using the traditional impregnation method, although initially exhibiting a high antibacterial rate, saw its rate drop sharply to approximately 50% under the same washing conditions. The mechanism of this phenomenon lies in the fact that the preparation method of the present invention involves homogeneously mixing tannic acid with dissolved plant fibers at the molecular scale. During the subsequent coagulation and regeneration process, tannic acid molecules are physically embedded and fixed within the reformed three-dimensional cellulose network framework.

[0116] In contrast, the traditional process in Comparative Example 4 only allows tannic acid to adhere to the fiber surface of the existing gauze. This surface adhesion relies mainly on weak physical adsorption, resulting in low binding strength. Therefore, during washing, the functional components easily detach and dissolve from the material surface, leading to a rapid loss of antibacterial function. The technical solution of this invention integrates the structural construction and functionalization of the material, realizing the transformation of functional components from surface loading to bulk embedding, thereby fundamentally solving the technical problem of functional durability and obtaining a functionalized medical material with stable performance.

[0117] Test Example 3: Determination of Residual Ionic Liquid Content

[0118] This test case aims to quantitatively analyze the final residual amount of ionic liquid in the sample to verify the controllability of solvent retention in the process of this invention.

[0119] Experimental steps:

[0120] Preparation of standard curve:

[0121] Accurately weigh 1-allyl-3-methylimidazolium chloride ([AMIM]Cl) standard, and dilute it stepwise with deionized water to prepare standard solutions with concentrations of 10, 20, 30, 40, and 50 mg / L. Using a UV-Vis spectrophotometer, measure the absorbance of each standard solution at the characteristic absorption wavelength of [AMIM]Cl, 211 nm, and plot a concentration-absorbance standard curve.

[0122] Sample extraction:

[0123] Accurately weigh 0.1 g of the dried samples from Examples 1-4 and Comparative Example 3, and place them in separate 50 mL volumetric flasks. Add approximately 40 mL of deionized water, place the flasks in an ultrasonic cleaner, and sonicate at 40 kHz for 30 minutes to ensure that any residual ionic liquid in the samples is completely dissolved in the water.

[0124] Measurement and Calculation:

[0125] The volumetric flask containing the extracted solution was brought to the mark with deionized water, shaken well, and allowed to stand. The supernatant was collected, filtered through a 0.45 μm filter membrane, and its absorbance was measured at 211 nm using a UV-Vis spectrophotometer. The measured absorbance was substituted into the standard curve equation to calculate the concentration of [AMIM]Cl in the extract, and then its mass fraction (wt%) in the original gauze sample was calculated. Each sample group underwent three parallel tests, and the average value was taken.

[0126] Table 3. Test data on residual ionic liquid in the examples and comparative samples

[0127]

[0128] Results analysis:

[0129] Table 3 presents test data that objectively quantifies the residual ionic liquid in the final product under different process conditions. The samples from Examples 1-4 all had residual ionic liquid levels within a specific range of 2.9% to 4.1%. In contrast, the sample from Comparative Example 3, after thorough washing with deionized water, had a residual liquid level as low as 0.08%. This result confirms that by controlling the concentration of the alcohol-water solution and the treatment time in the coagulation and regeneration step, incomplete replacement of the ionic liquid solvent can be achieved, thereby controllably retaining a specific amount of ionic liquid in the material matrix.

[0130] The technical solution of this invention utilizes retained ionic liquid molecules. When the ionic liquid is completely removed (as in Comparative Example 3), during the drying process, the molecular chains of regenerated cellulose become tightly packed due to strong hydrogen bonding, forming highly crystalline or dense amorphous regions, resulting in high macroscopic rigidity of the material. The retained ionic liquid molecules physically occupy the spaces between the cellulose macromolecular chains, constituting molecular-level spacers. In the subsequent drying and shaping stages, they effectively prevent the excessive proximity of cellulose molecular chains and the reformation of numerous hydrogen bonds. This plasticizing effect, completed during the formation of the material's bulk structure—in-situ plasticizing—is the structural basis for the material's intrinsic flexibility.

[0131] Controllable residual amount of ionic liquid is key to achieving a balance between the mechanical properties and flexibility of materials. Combined with physical property test data, it is known that excessively low residual amounts (Comparative Example 3) result in a severe loss of flexibility, making it unsuitable as a medical dressing that needs to conform to the body. The technical solution of this invention, by precisely controlling the residual amount of solvent, endows the material with the necessary flexibility while ensuring the integrity of the material structure. This design, which transforms the solvent from a mere processing medium into a functional component of the final product, embodies the integrated characteristics of the process and ultimately yields a medical gauze with excellent comprehensive physical properties.

Claims

1. Degradable medical gauze based on plant fibers, characterized in that, The raw materials are prepared by the following weight parts: Plant fiber: 5-15 parts; Tannic acid: 0.5-2.0 parts; Boric acid: 0.1-1.0 parts; 1-allyl-3-methylimidazole chloride: 100 parts; The gauze contains 2.5-4.5% of 1-allyl-3-methylimidazole chloride by mass fraction; The production process of the degradable medical gauze comprises the following steps: (a) adding plant fiber, tannic acid and boric acid into 1-allyl-3-methylimidazole chloride, heating and stirring until a homogeneous solution is formed; (b) coating the homogeneous solution obtained in step (a) into a film; (c) immersing the film obtained in step (b) into an alcohol aqueous solution for coagulation and regeneration treatment, and controlling the residual amount of 1-allyl-3-methylimidazole chloride in the final product; (d) drying the gauze after coagulation and regeneration treatment.

2. The plant fiber-based degradable medical gauze according to claim 1, characterized in that, The plant fiber is cotton stalk fiber or bamboo pulp.

3. The plant fiber-based degradable medical gauze according to claim 1, characterized in that, The 1-allyl-3-methylimidazole chloride is prepared by reacting N-methylimidazole with allyl chloride at 60±5℃ for 36 hours.

4. A process for the production of the plant fiber-based degradable medical gauze according to any one of claims 1 to 3, characterized by, The process comprises the following steps: (a) adding plant fiber, tannic acid and boric acid into 1-allyl-3-methylimidazole chloride, heating and stirring until a homogeneous solution is formed; (b) coating the homogeneous solution obtained in step (a) into a film; (c) immersing the film obtained in step (b) into an alcohol aqueous solution for coagulation and regeneration treatment, and controlling the residual amount of 1-allyl-3-methylimidazole chloride in the final product; (d) drying the gauze after coagulation and regeneration treatment.

5. The process for the production of degradable medical plant fiber based gauze according to claim 4, characterized in that, In step (a), the temperature of heating and stirring is 90-110℃, and the time is 2-6 hours.

6. The production process of the plant fiber-based degradable medical gauze according to claim 4, characterized in that, In step (c), the alcohol aqueous solution is an ethanol aqueous solution with a volume fraction of 10-50%, the temperature of coagulation and regeneration treatment is 15-30℃, and the time is 5-20 minutes.

7. The production process of the plant fiber-based degradable medical gauze according to claim 4, characterized in that, After step (b) and before step (c), a step of heat treating the film at 60-80℃ for 10-30 minutes is further included.

8. The production process of the plant fiber-based degradable medical gauze according to claim 4, characterized in that, In step (d), the drying is vacuum freeze-drying.

9. The production process of the plant fiber-based degradable medical gauze according to claim 4, characterized in that, In step (b), the homogeneous solution is coated into a wet film with a thickness of 200-800μm. In step (b), the homogeneous solution is coated into a wet film with a thickness of 200-800μm.

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