Chitosan fiber antimicrobial gel and method of making same

Abstract

The application provides a chitosan fiber antibacterial gel and a preparation method thereof, and belongs to the field of chitosan fiber gel preparation, wherein an alcohol / acid / water system is obtained by mixing alcohol, acid and water in a volume ratio of (50-90):(1-5):(10-50), and the alcohol / acid / water system is put into chitosan fibers to obtain a first mixed solution; then, an alcohol / water system is obtained by mixing alcohol and water in a specific ratio, a coupling agent and a carboxyl-containing antibacterial agent are pre-activated to obtain a second mixed solution; finally, the second mixed solution is added to the first mixed solution, and reaction, filtration, washing and drying are carried out to obtain the chitosan fiber antibacterial gel. According to the application, a ternary reaction system of alcohol / acid / water in a specific ratio is constructed, so that the chitosan fiber is subjected to surface antibacterial modification in a non-dissolution swelling state; after the reaction is completed, the product can be purified only by simple filtration and washing, the product retains a fiber form, and the subsequent textile processing is facilitated, and the preparation steps are simplified.

Description

Technical Field

[0001] This invention relates to the field of chitosan fiber gel preparation technology, specifically to a chitosan fiber antibacterial gel and its preparation method. Background Technology

[0002] Chitosan fibers possess excellent biocompatibility, biodegradability, and certain antibacterial properties, making them widely used in dressings for the repair of infected and diabetic wounds. However, traditional chitosan fibers suffer from poor water absorption and limited antibacterial effects, failing to meet the repair needs of complex wounds. Common improvement methods include blending chitosan fibers with antibacterial agents to enhance antibacterial properties, but this method does not significantly improve water absorption. Quaternization modification can significantly improve antibacterial properties, but it leads to increased water solubility of chitosan fibers, severely affecting textile processing performance. Therefore, how to simultaneously improve the antibacterial properties and water-absorbing gelation ability of chitosan fibers while maintaining their morphology is a key challenge in developing highly efficient chitosan-based medical materials that promote healing.

[0003] In view of this, it is necessary to design a chitosan fiber antibacterial gel and its preparation method to solve the above problems. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a chitosan fiber antibacterial gel and its preparation method, aiming to solve the technical problem of how to simultaneously improve the antibacterial properties and water absorption gelation ability of chitosan fibers while maintaining the fiber morphology.

[0005] In a first aspect, embodiments of this application provide a method for preparing chitosan fiber antibacterial gel, comprising the following steps:

[0006] S1, mix alcohol, acid and water in a volume ratio of (50-90):(1-5):(10-50) to obtain an alcohol / acid / water system, and put chitosan fiber into the alcohol / acid / water system to obtain a first mixed solution;

[0007] S2, a specific ratio of alcohol and water is mixed to obtain an alcohol / water system, and a coupling agent and a carboxyl-containing antibacterial agent are added to the alcohol / water system for pre-activation to obtain a second mixed solution;

[0008] S3, add the second mixed solution obtained in step S2 to the first mixed solution obtained in step S1, react for a certain time, filter, wash and dry to obtain chitosan fiber antibacterial gel.

[0009] In the technical solution of this application embodiment, chitosan fibers are swollen but not dissolved using a specific ratio of alcohol / acid / water system. A coupling agent and a carboxyl-containing antibacterial agent are pre-activated using the same alcohol / water system. Then, using the active amino groups in the chitosan molecules as reaction sites, a coupling reaction occurs, causing the active amino groups to react with the carboxyl groups of the antibacterial agent, thereby grafting the antibacterial agent onto the chitosan fibers, resulting in chitosan fibers with good antibacterial properties. Because the grafted antibacterial agent disrupts the hydrogen bonds within the molecules, water molecules can more easily penetrate into the fiber interior. Therefore, the final chitosan fiber antibacterial gel has excellent water absorption and swelling properties, and after water absorption and swelling, it exhibits a hydrogel morphology. Throughout the preparation process, the chitosan fibers maintain their fiber structure without dissolution. Therefore, after the reaction, only simple filtration and washing are required for purification, and the product retains its fiber morphology, which is beneficial for subsequent textile processing. This eliminates the need to collect the reaction solution, purify it, and then respin it, simplifying the preparation steps.

[0010] In some embodiments, the alcohol used in steps S1 and S2 is one or more of methanol, ethanol, and isopropanol; the acid used in step S1 is one or more of hydrochloric acid, acetic acid, oxalic acid, and citric acid.

[0011] In this embodiment, alcohol is a non-benign solvent for chitosan, while acid and water are benign solvents for chitosan. Therefore, chitosan neither swells nor dissolves in alcohol, but dissolves directly in acidic aqueous solution. This application obtains an alcohol / acid / water system by adjusting the ratio of benign to non-benign solvents. Chitosan fibers placed in this specific alcohol / acid / water system swell without dissolving, maintaining their fiber structure. After the reaction, the product can be obtained by direct filtration and washing.

[0012] In some embodiments, the volume ratio of alcohol to water in the alcohol / water system is consistent with the volume ratio of alcohol to water in the alcohol / acid / water system.

[0013] In this embodiment, maintaining a consistent volume ratio of alcohol to water in both systems helps to keep the solution ratio stable.

[0014] In some embodiments, the volume ratio of the second mixed solution to the first mixed solution is (0.1-0.5):1.

[0015] In this embodiment, by limiting the volume ratio of the two mixed solutions, it is beneficial to ensure that the coupling agent is fully dissolved and fully contacts and reacts with the chitosan fibers.

[0016] In some embodiments, in step S2, the coupling agent is a mixture of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), N,N'-dicyclohexylcarbodiimide, and N,N'-diisopropylcarbodiimide; the carboxyl-containing antibacterial agent is a polyphenolic antibacterial agent or a small molecule antibacterial agent; the polyphenolic antibacterial agent is any one of gallic acid, tannic acid, chlorogenic acid, caffeic acid, and protocatechuic acid; the small molecule antibacterial agent is any one of carbenicillin, salicylic acid, benzoic acid, fumaric acid, and dehydroacetic acid.

[0017] In some embodiments, the molar ratio of the coupling agent to the carboxyl group in the carboxyl-containing antibacterial agent is (1-5):1; the mass ratio of the carboxyl-containing antibacterial agent to the chitosan fiber is 1:(0.5-5).

[0018] In some embodiments, in step S3, the reaction refers to the reaction between the active amino groups in the chitosan molecules and the carboxyl groups of the antibacterial agent, thereby grafting the antibacterial agent onto the surface of the chitosan fibers.

[0019] In some embodiments, in step S3, the reaction time is 3-72 hours and the reaction temperature is 4-100°C.

[0020] In some embodiments, in step S3, the washing refers to washing the reaction product sequentially with alcohol solutions of increasingly higher concentrations; the volume percentage of alcohol in the alcohol solutions is 50-100%.

[0021] Secondly, embodiments of this application provide a chitosan fiber antibacterial gel, which is prepared according to the preparation method of chitosan fiber antibacterial gel described in any one of the foregoing schemes.

[0022] The beneficial effects of this application are as follows:

[0023] This application provides a chitosan fiber antibacterial gel and its preparation method. The chitosan fibers are swollen but not dissolved using a specific ratio of alcohol / acid / water system. A coupling agent and a carboxyl-containing antibacterial agent are pre-activated using the same alcohol / water system. Then, using the active amino groups in the chitosan molecules as reaction sites, a coupling reaction occurs, causing the active amino groups to react with the carboxyl groups of the antibacterial agent, thereby grafting the antibacterial agent onto the chitosan fibers, resulting in chitosan fibers with good antibacterial properties. Because the grafted antibacterial agent disrupts the hydrogen bonds within the molecules, allowing water molecules to more easily penetrate the fiber interior, the final chitosan fiber antibacterial gel exhibits excellent water absorption and swelling properties, and after absorbing water and swelling, it presents a hydrogel morphology.

[0024] In this application's technical solution, alcohol is a non-benign solvent for chitosan, while acidic aqueous solution is a benign solvent for chitosan. Therefore, chitosan neither swells nor dissolves in alcohol, but dissolves directly in acidic aqueous solution. This application obtains an alcohol / acid / water system by adjusting the ratio of benign to non-benign solvents. Chitosan fibers placed in this specific alcohol / acid / water system swell without dissolving, maintaining their fiber structure. After the reaction, the product can be obtained simply by filtration and washing. That is, throughout the entire preparation process, the chitosan fibers maintain their fiber structure without dissolution. Therefore, purification can be achieved through simple filtration and washing after the reaction, and the product retains its fiber morphology, which is beneficial for subsequent textile processing. It eliminates the need to collect the reaction solution, purify it, and respin it, simplifying the preparation steps.

[0025] The chitosan fiber antibacterial gel prepared in this application has good absorption and swelling properties, with a water absorption rate of up to 200%. It has an antibacterial rate of 99% against both Escherichia coli and Staphylococcus aureus, and has good application prospects in the fields of high-end dressings, hemostatic materials and tissue engineering.

[0026] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0028] Figure 1 This is a schematic diagram showing the water absorption and swelling effect of the chitosan fiber antibacterial gel prepared in Example 1 of this application;

[0029] Figure 2 The images shown are optical microscope images of chitosan fibers after swelling in an alcohol / acid / water system with a volume ratio of 80:1:20 in Example 1 of this application; where (a) is a low-power image, (b) is a high-power image, and (c) is a schematic diagram of fiber diameter measurement.

[0030] Figure 3 The image shows an optical microscope image of chitosan fibers in Comparative Example 1 of this application after swelling in an alcohol / water system with a volume ratio of 80:21; where (a) is a low-power image, (b) is a high-power image, and (c) is a schematic diagram of fiber diameter measurement.

[0031] Figure 4 The images shown are optical microscope images of chitosan fibers in Comparative Example 3 of this application after swelling in an isopropanol / anhydrous ethanol system with a volume ratio of 4:1; where (a) is a low-power image, (b) is a high-power image, and (c) is a schematic diagram of fiber diameter measurement.

[0032] Figure 5 This is a photograph of chitosan fibers dissolved in a propylene glycol / glacial acetic acid / water system in Comparative Example 4 of this application.

[0033] Figure 6 This is a photograph showing the dissolution or swelling of chitosan fibers in the system during the preparation of Comparative Example 5 of this application.

[0034] Figure 7 This is a photograph of the chitosan fibers prepared in Example 1 of this application after swelling in an alcohol / acid / water system with a volume ratio of 80:1:20. Detailed Implementation

[0035] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0037] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0038] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0039] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0040] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces). Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0041] To address the technical challenge of simultaneously enhancing the antibacterial properties and water-absorbing gelation capabilities of chitosan fibers while maintaining their fibrous morphology, this application provides a chitosan fiber antibacterial gel and its preparation method. The method involves constructing a ternary reaction system with a specific ratio of alcohol / acid / water, allowing the chitosan fibers to undergo surface antibacterial modification in a non-dissolving, swollen state. After the reaction, purification is achieved through simple filtration and washing, and the product retains its fiber morphology, facilitating subsequent textile processing without the need for collecting the reaction solution, purifying it, and re-spinning, thus simplifying the preparation process. The chitosan fiber antibacterial gel prepared in this application exhibits excellent absorption and swelling properties, with a water absorption rate reaching 200%. It demonstrates antibacterial rates exceeding 99% against both *Escherichia coli* and *Staphylococcus aureus*, showing promising application prospects in high-end dressings, hemostatic materials, and tissue engineering.

[0042] In a first aspect, embodiments of this application provide a method for preparing chitosan fiber antibacterial gel, comprising the following steps:

[0043] S1, mix alcohol, acid and water in a volume ratio of (50-90):(1-5):(10-50) to obtain an alcohol / acid / water system, and put chitosan fiber into the alcohol / acid / water system to obtain the first mixed solution;

[0044] S2, a specific ratio of alcohol and water is mixed to obtain an alcohol / water system, and a coupling agent and a carboxyl-containing antibacterial agent are added to the alcohol / water system for pre-activation to obtain a second mixed solution;

[0045] S3, add the second mixed solution obtained in step S2 to the first mixed solution obtained in step S1, react for a certain time, filter, wash and dry to obtain chitosan fiber antibacterial gel.

[0046] In the technical solution of this application embodiment, chitosan fibers are swollen but not dissolved using a specific ratio of alcohol / acid / water system. A coupling agent and a carboxyl-containing antibacterial agent are pre-activated using the same alcohol / water system. Then, using the active amino groups in the chitosan molecules as reaction sites, a coupling reaction occurs, causing the active amino groups to react with the carboxyl groups of the antibacterial agent, thereby grafting the antibacterial agent onto the chitosan fibers, resulting in chitosan fibers with good antibacterial properties. Because the grafted antibacterial agent disrupts the hydrogen bonds within the molecules, water molecules can more easily penetrate into the fiber interior. Therefore, the final chitosan fiber antibacterial gel has excellent water absorption and swelling properties, and after water absorption and swelling, it exhibits a hydrogel morphology. Throughout the preparation process, the chitosan fibers maintain their fiber structure without dissolution. Therefore, after the reaction, only simple filtration and washing are required for purification, and the product retains its fiber morphology, which is beneficial for subsequent textile processing. This eliminates the need to collect the reaction solution, purify it, and then respin it, simplifying the preparation steps.

[0047] Furthermore, the alcohol used in steps S1 and S2 is one or a mixture of methanol, ethanol, and isopropanol; the acid used in step S1 is one or a mixture of hydrochloric acid, acetic acid, oxalic acid, and citric acid.

[0048] In the technical solution of this application embodiment, alcohol is a non-benign solvent for chitosan, while acid and water are benign solvents for chitosan. Therefore, chitosan neither swells nor dissolves in alcohol, but dissolves directly in acid or water. This application obtains an alcohol / acid / water system by adjusting the ratio of benign to non-benign solvents. Chitosan fibers placed in this specific ratio of alcohol / acid / water system swell but do not dissolve, maintaining the fiber structure. After the reaction is complete, the product can be obtained by direct filtration and washing.

[0049] Furthermore, the mass concentration of chitosan fibers in the first mixed solution is 1-5%.

[0050] In the technical solution of this application embodiment, by limiting the mass concentration of chitosan fibers, it is beneficial to ensure that each fiber can fully contact the solvent and absorb sufficient solvent.

[0051] Furthermore, the volume ratio of alcohol to water in the alcohol / water system remains consistent with that in the alcohol / acid / water system.

[0052] In the technical solution of this application embodiment, by limiting the volume ratio of alcohol to water in the two systems to be consistent, it helps to maintain the stability of the solution ratio.

[0053] Furthermore, the volume ratio of the second mixed solution to the first mixed solution is (0.1-0.5):1.

[0054] In the technical solution of this application embodiment, by limiting the volume ratio of the two mixed solutions, it is beneficial to ensure that the coupling agent is fully dissolved and fully contacts and reacts with the chitosan fibers.

[0055] Further, in step S2, the coupling agent is a mixture of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), N,N'-dicyclohexylcarbodiimide, and N,N'-diisopropylcarbodiimide; the carboxyl-containing antibacterial agent is a polyphenolic antibacterial agent or a small molecule antibacterial agent; the polyphenolic antibacterial agent is any one of gallic acid, tannic acid, chlorogenic acid, caffeic acid, and protocatechuic acid; the small molecule antibacterial agent is any one of carbenicillin, salicylic acid, benzoic acid, fumaric acid, and dehydroacetic acid.

[0056] Furthermore, the molar ratio of the coupling agent to the carboxyl group in the carboxyl-containing antibacterial agent is (1-5):1; the mass ratio of the carboxyl-containing antibacterial agent to chitosan fiber is 1:(0.5-5).

[0057] Furthermore, in step S3, the reaction refers to the reaction between the active amino groups in the chitosan molecules and the carboxyl groups of the antibacterial agent, thereby grafting the antibacterial agent onto the surface of the chitosan fibers.

[0058] Furthermore, in step S3, the reaction time is 3-72 hours and the reaction temperature is 4-100℃.

[0059] Furthermore, in step S3, washing refers to washing the reaction product sequentially with alcohol solutions of increasingly higher concentrations; the volume percentage of alcohol in the alcohol solutions is 50-100%.

[0060] Furthermore, in step S3, the drying temperature is 60-80℃.

[0061] Secondly, embodiments of this application provide a chitosan fiber antibacterial gel, which is prepared according to the preparation method of chitosan fiber antibacterial gel according to any of the foregoing schemes.

[0062] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0063] I. Preparation Method

[0064] Example 1

[0065] Example 1 provides a method for preparing chitosan fiber antibacterial gel, which specifically includes the following steps:

[0066] S1. Ethanol, acetic acid and water in a volume ratio of 80:1:20 are mixed to obtain an 80 mL alcohol / acid / water system. 5 g of chitosan fiber with a degree of deacetylation of 85% is placed into the alcohol / acid / water system and shaken at 25°C for 1 h to obtain the first mixed solution.

[0067] S2, mix ethanol and water in a volume ratio of 80:20 to obtain a 40 mL alcohol / water system, add 2.64 g gallic acid, 2.975 g EDC and 1.785 g NHS into the alcohol / water system, pre-activate under shaking conditions for 30 min to activate the carboxyl group in gallic acid, and obtain a second mixed solution.

[0068] S3. Add the second mixed solution obtained in step S2 to the first mixed solution obtained in step S1, shake and react for 24 hours, filter, wash successively with ethanol solutions of 80%, 90%, and 100% by volume, and then dry at 60°C for 12 hours to obtain chitosan fiber antibacterial gel. The mass ratio of carboxyl-containing antibacterial agent to chitosan fiber is 1:1.89 (2.64g:5g).

[0069] Please see Figure 1 As shown, Example 1 uses a ternary system of alcohol / acid / water with a volume ratio of 80:1:20 to fully swell chitosan fibers without dissolving them, resulting in a hydrogel-like appearance. With this setup, after modifying the chitosan fibers, a chitosan fiber antibacterial gel with good water absorption, swelling, and antibacterial properties can be directly obtained through filtration, washing, and drying. Please refer to... Figure 2 As shown, the diameter of the swollen chitosan fibers is 118±0.34μm, which is about 7.3 times that before swelling.

[0070] Example 2

[0071] The difference between Example 2 and Example 1 is that in step S2, 1.056g of gallic acid, 1.19g of EDC, and 0.714g of NHS are placed in an alcohol / water system, and the mass ratio of the carboxyl-containing antibacterial agent to chitosan fiber is 1:4.73 (1.056g: 5g). Everything else is the same as in Example 1 and will not be repeated here.

[0072] Example 3

[0073] The difference between Example 3 and Example 1 is that in step S2, 5.28g of gallic acid, 5.95g of EDC, and 3.75g of NHS are placed in an alcohol / water system, and the mass ratio of the carboxyl-containing antibacterial agent to chitosan fiber is 1:0.95 (5.28g: 5g). Everything else is the same as in Example 1 and will not be repeated here.

[0074] Example 4

[0075] The difference between Example 4 and Example 1 is that in step S2, 7.92g of gallic acid, 8.925g of EDC, and 5.355g of NHS are placed in an alcohol / water system, and the mass ratio of the carboxyl-containing antibacterial agent to chitosan fiber is 1:0.63 (7.92g:5g). Everything else is the same as in Example 1 and will not be repeated here.

[0076] Comparative Example 1

[0077] The difference between Comparative Example 1 and Example 1 is that in step S1, the alcohol / acid / water system with a volume ratio of 80:1:20 is replaced with an alcohol / water system with a volume ratio of 80:21. The rest is the same as in Example 1, and will not be repeated here.

[0078] The solvent system used in Comparative Example 1 differed from that in Example 1. The chitosan fibers showed poor swelling in the alcohol / water system, and a small amount of dissolution occurred. Please refer to [link / reference]. Figure 3 As shown, the diameter of the chitosan fibers in the alcohol / water system is 44±1.19μm, which is about 2.5 times that before swelling.

[0079] Comparative Example 2

[0080] The difference between Comparative Example 2 and Example 1 is that in step S1, the alcohol / acid / water system with a volume ratio of 80:1:20 is replaced with an acid / water system with a volume ratio of 1:100. The rest is the same as in Example 1, and will not be repeated here.

[0081] The solvent system used in Comparative Example 2 is different from that used in Example 1. The chitosan fibers completely dissolved in the acid / water system, so the swelling effect could not be tested.

[0082] Comparative Example 3

[0083] The difference between Comparative Example 3 and Example 1 is that in step S1, the alcohol / acid / water system with a volume ratio of 80:1:20 is replaced with an isopropanol / anhydrous ethanol system with a volume ratio of 4:1. The rest is the same as in Example 1 and will not be repeated here.

[0084] Comparative Example 3 uses a different solvent system than Example 1. Chitosan fibers show almost no swelling in the isopropanol / anhydrous ethanol system. Please refer to [link / reference needed]. Figure 4 As shown, the diameter of the chitosan fibers in the alcohol / water system is 20.60±0.60μm, which is only about 1.3 times that before swelling.

[0085] Comparative Example 4

[0086] The difference between Comparative Example 4 and Example 1 is that in step S1, the alcohol / acid / water system with a volume ratio of 80:1:20 is replaced with a propylene glycol / glacial acetic acid / water system with a volume ratio of 4:1:95. The rest is the same as in Example 1, and will not be repeated here.

[0087] Compared to Example 1, the amount of alcohol used in Comparative Example 4 was significantly reduced, resulting in the chitosan fibers not only failing to swell sufficiently but also completely dissolving in the propylene glycol / glacial acetic acid / water system. Please refer to [link / reference needed]. Figure 5 The image shown is a photograph of chitosan fibers dissolved in a propylene glycol / glacial acetic acid / water system.

[0088] Comparative Example 5

[0089] The difference between Comparative Example 5 and Example 1 is that in step S1, 5g of chitosan fiber with a degree of deacetylation of 85% is first placed in an aqueous acetic acid solution with a volume ratio of 5%, and stirred to form a stable solution. Then, ethanol is added to the solution, and the volume ratio of ethanol to acetic acid is 80:1. The rest is the same as in Example 1, and will not be repeated here.

[0090] The mixing order of Comparative Example 5 differs from that of Example 1. In Example 1, the mixing was simultaneous, while in Comparative Example 5, chitosan fibers were mixed with acid first, followed by the addition of alcohol. Please refer to [link to relevant documentation]. Figure 6 As shown in Comparative Example 5, the chitosan fibers completely dissolved when mixed with acid. Although the subsequent addition of alcohol could cause some chitosan to be precipitated, the precipitated chitosan had lost its fiber structure, making it impossible to test the fiber diameter and preventing further swelling. Figure 7 This is a photograph of the chitosan fibers swollen in an alcohol / acid / water system with a volume ratio of 80:1:20, as shown in Example 1. Figure 6 (b) and Figure 7 In comparison, it can be seen that the volume of chitosan fiber after swelling in Example 1 is significantly larger than that in Comparative Example 5. Therefore, the swelling effect of Example 1 is significantly better than that of Comparative Example 5.

[0091] Comparing Example 1 and Comparative Examples 1-5, it is evident that the ternary system of alcohol / acid / water with a volume ratio of 80:1:20 is more conducive to the full swelling of chitosan fibers. Changing the solvent components, solvent ratio, or solvent addition order in the system cannot fully swell the chitosan fibers; on the contrary, it may cause the chitosan fibers to dissolve. Specifically, the solvent systems or mixing methods used in Example 1, Comparative Examples 1 and 3 can all cause the chitosan fibers to swell without dissolving, but the swelling effect of Comparative Examples 1 and 3 is poor. The solvent systems used in Comparative Examples 2 and 4-5 cause the chitosan fibers to dissolve, and after precipitation, they cannot swell again.

[0092] By employing a specific ratio of alcohol / acid / water system to swell but not dissolve chitosan fibers, the preparation process is simplified. Throughout the entire preparation process, the chitosan fibers maintain their fibrous structure without dissolution. Therefore, after the reaction, purification can be achieved simply through filtration and washing, and the product retains its fibrous morphology, which is beneficial for subsequent textile processing. This eliminates the need to collect the reaction solution, purify it, and then respin it, resulting in a much shorter process.

[0093] II. Testing Methods

[0094] 1. Testing the water absorption efficiency of chitosan fiber antibacterial gel

[0095] The water absorption efficiency of a gel refers to the degree to which its mass or volume (including diameter) increases after absorbing liquid. For fibrous gels, their water absorption and swelling capacity can be directly reflected by measuring the change in their diameter before and after swelling. Therefore, the formula for calculating the water absorption efficiency of fibrous gels is:

[0096] Water absorption efficiency (%) = [(D S -D0) / D0]×100%

[0097] Where D0 is the initial diameter of the gel fiber before swelling (dry state); D S The diameter of the swollen gel fiber is denoted as '-'.

[0098] 2. Testing the antibacterial rate of chitosan fiber antibacterial gel

[0099] With a concentration of 1 10 6 A bacterial suspension (containing *Escherichia coli* or *Staphylococcus aureus*) at CFU / mL was directly applied to the test gel sample and the control sample. After 24 hours, surviving bacteria were recovered and cultured for counting. The antibacterial activity (antibacterial rate) of the gel was calculated by comparing the change in the number of viable bacteria before and after the application. The calculation formula is as follows:

[0100] Antibacterial rate (%) = (average colony count in control group - average colony count in experimental group) / average colony count in control group × 100%.

[0101] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0102] The water absorption efficiency and antibacterial rate data of the chitosan fiber antibacterial gels prepared in Examples 1-4 and Comparative Examples 1-5 are shown in Table 1.

[0103] Table 1. Water absorption, swelling properties, and antibacterial properties of chitosan fiber antibacterial gel

[0104]

[0105] As can be seen from the comparison of the examples and the comparative examples, the chitosan fiber gels prepared in Examples 1 and 3-4 have significantly higher water absorption efficiency than those in Comparative Examples 1-4. This is because the grafted antibacterial agent disrupts the hydrogen bonds within the molecules, making it easier for water molecules to penetrate into the fiber interior, resulting in the chitosan fiber gels obtained in Examples 1 to 4 exhibiting excellent water absorption and swelling properties. The water absorption efficiency of Example 2 is lower compared to the other examples because the amount of coupling agent and antibacterial agent added is too small to fully disrupt the hydrogen bonds within the molecules, resulting in limited improvement in water absorption efficiency.

[0106] Furthermore, the antibacterial rates of the chitosan fiber gels prepared in Examples 1-4 were significantly higher than those in Comparative Examples 1-4. This is because the water absorption efficiency of the chitosan fiber gel facilitates sufficient contact between the antibacterial agent grafted onto the fiber and the bacteria, thereby achieving a better antibacterial effect. Since the solvent systems used in Comparative Examples 2 and 4-5 dissolved the chitosan fibers, even if they precipitated, they could not swell again, therefore no swelling data were available.

[0107] In summary, this application provides a chitosan fiber antibacterial gel and its preparation method. The chitosan fiber is swollen but not dissolved using a specific ratio of alcohol / acid / water system. A coupling agent and a carboxyl-containing antibacterial agent are pre-activated using the same alcohol / water system. Then, using the active amino groups in the chitosan molecule as reaction sites, a coupling reaction occurs, causing the active amino groups to react with the carboxyl groups of the antibacterial agent, thereby grafting the antibacterial agent onto the chitosan fiber, resulting in chitosan fiber with excellent antibacterial properties. The chitosan fiber prepared by this technology exhibits excellent antibacterial and water-absorbing properties. Furthermore, the chitosan remains in a fibrous structure throughout the preparation process without dissolving, which helps reduce the difficulty of subsequent textile processing and shortens the processing flow, demonstrating potential application value in the field of medical dressings.

[0108] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a chitosan fiber antibacterial gel, characterized in that, Includes the following steps: S1, mix alcohol, acid and water in a volume ratio of (50-90):(1-5):(10-50) to obtain an alcohol / acid / water system, and put chitosan fiber into the alcohol / acid / water system to obtain a first mixed solution; S2, a specific ratio of alcohol and water is mixed to obtain an alcohol / water system, and a coupling agent and a carboxyl-containing antibacterial agent are added to the alcohol / water system for pre-activation to obtain a second mixed solution; S3, add the second mixed solution obtained in step S2 to the first mixed solution obtained in step S1, react for a certain time, filter, wash and dry to obtain chitosan fiber antibacterial gel. The alcohol used in steps S1 and S2 is one or a mixture of methanol, ethanol, and isopropanol; the acid used in step S1 is one or a mixture of hydrochloric acid, acetic acid, oxalic acid, and citric acid. The volume ratio of alcohol to water in the alcohol / water system is consistent with the volume ratio of alcohol to water in the alcohol / acid / water system; The volume ratio of the second mixed solution to the first mixed solution is (0.1-0.5):1; In step S3, the reaction refers to the reaction between the active amino groups in the chitosan molecules and the carboxyl groups of the antibacterial agent, thereby grafting the antibacterial agent onto the surface of the chitosan fibers.

2. The method for preparing chitosan fiber antibacterial gel according to claim 1, characterized in that, In step S2, the coupling agent is one of the following: a mixture of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, N,N'-dicyclohexylcarbodiimide, and N,N'-diisopropylcarbodiimide; the carboxyl-containing antibacterial agent is a polyphenolic antibacterial agent or a small molecule antibacterial agent; the polyphenolic antibacterial agent is any one of gallic acid, tannic acid, chlorogenic acid, caffeic acid, and protocatechuic acid; the small molecule antibacterial agent is any one of carbenicillin, salicylic acid, benzoic acid, fumaric acid, and dehydroacetic acid.

3. The method for preparing chitosan fiber antibacterial gel according to claim 1, characterized in that, The molar ratio of the coupling agent to the carboxyl group in the carboxyl-containing antibacterial agent is (1-5):1; the mass ratio of the carboxyl-containing antibacterial agent to the chitosan fiber is 1:(0.5-5).

4. The method for preparing chitosan fiber antibacterial gel according to claim 1, characterized in that, In step S3, the reaction time is 3-72 hours and the reaction temperature is 4-100℃.

5. The method for preparing chitosan fiber antibacterial gel according to claim 1, characterized in that, In step S3, the washing refers to washing the reaction product sequentially with alcohol solutions of increasingly higher concentrations; the volume percentage of alcohol in the alcohol solutions is 50-100%.

6. A chitosan fiber antibacterial gel, characterized in that, The chitosan fiber antibacterial gel is prepared by the method described in any one of claims 1-5.

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