Chitosan-based antibacterial dressing and preparation method thereof

Abstract

The invention relates to the technical field of medical materials, and discloses a chitosan-based antibacterial dressing and a preparation method thereof. The antibacterial dressing comprises an adhesive tape layer, a dressing surface layer and a protective film, functional dressing liquid is adsorbed on the dressing surface layer, and the functional dressing liquid is prepared from, by weight, 2-4 parts of propolis extract, 1-3 parts of glycerinum, 1-3 parts of alginate oligosaccharide, 0.5-1 part of carbomer, 0.001-0.005 part of growth factors, 2-4 parts of modified chitosan and 3-6 parts of modified gelatin. The modified chitosan is grafted with borneol base and long-chain pyridinium salt, so that reproduction of common pathogenic bacteria can be efficiently and continuously inhibited, and wound infection is prevented; the modified gelatin can shorten the bleeding time of the wound surface and reduce the bleeding amount, and the dressing has good biocompatibility and biodegradability.

Description

Technical Field

[0001] This invention relates to the field of medical materials technology, specifically to a chitosan-based antibacterial dressing and its preparation method. Background Technology

[0002] As the largest organ in the human body, the skin serves not only as a physical barrier against external physical impacts and chemical stimuli, but also as an immune defense against the invasion of pathogenic microorganisms. It also plays a vital physiological role in thermoregulation and tactile sensation. However, in clinical practice and daily life, surgical incisions, burns, chronic ulcers, and skin damage caused by accidental injuries are highly susceptible to breaching this defense, leading to a series of problems. Medical dressings, as the core material for wound care, play a crucial role in creating a suitable healing microenvironment for the wound. Through covering and protecting the wound, they achieve basic functions such as isolating contaminants, absorbing exudate, and maintaining wound moisture. Currently used dressings such as gauze and absorbent cotton, while possessing some absorbency and physical protection, generally suffer from weak antibacterial efficacy and limited hemostatic effects, thus delaying wound healing and increasing patient suffering and treatment costs. Against this backdrop, the development of novel medical dressings that combine highly effective antibacterial properties with rapid hemostatic function has become a research hotspot in the field of wound care.

[0003] Patent application number CN201710358285.X discloses an antibacterial dressing, which modifies nano-titanium dioxide sol through cross-linking with polyisocyanate, polyethylene glycol, and tetraethylene glycol. The resulting network structure improves the antibacterial performance of the system. However, the antibacterial performance of nano-titanium dioxide is dependent on light exposure, and the antibacterial effect is significantly weakened when most wounds are in a dark or low-light environment. Patent application number CN201410445835.8 discloses an antibacterial solution, an antibacterial dressing, and a method for preparing an antibacterial dressing. It uses a mixture of biguanide antibacterial agents and quaternary ammonium salt antibacterial agents to improve the antibacterial effect of the system. However, directly adding organic antibacterial agents can easily lead to insufficient stability and large fluctuations in antibacterial efficacy. Grafting them onto natural polymer carriers can better exert their antibacterial effect. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a chitosan-based antibacterial dressing and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions: A chitosan-based antibacterial dressing includes an adhesive layer, a dressing surface layer, and a protective film. The dressing surface layer is adsorbed with a functional dressing liquid, which comprises the following raw materials in parts by weight: 2-4 parts propolis extract, 1-3 parts glycerin, 1-3 parts fucoidan, 0.5-1 part carbomer, 0.001-0.005 parts growth factor, 2-4 parts modified chitosan, and 3-6 parts modified gelatin. The material of the dressing surface layer is one of pectin fiber cloth, cotton cloth, or silk cloth; The adhesive tape layer is a 15×15cm square with a thickness of 50μm, and is made of medical-grade non-toxic acrylic. The protective film and the adhesive tape layer have the same shape and size, and the thickness is 15μm. The material is silicone paper. The modified chitosan is prepared by the following steps: Step A1: Mix 5-cyanopyridine-2-carboxylic acid and acetonitrile, add 1-chlorododecane, heat to 100℃, reflux for 12 h, after the reaction is completed, rotary evaporate, purify, concentrate under reduced pressure to obtain intermediate product 1; Furthermore, the molar ratio of 5-cyanopyridine-2-carboxylic acid, acetonitrile, and 1-chlorododecane is 0.4-0.6 mol: 200-300 mL: 0.4-0.6 mol; In step A1, 5-cyanopyridine-2-carboxylic acid and 1-chlorododecane undergo a nucleophilic substitution reaction to introduce a carboxyl group into the system, providing reaction conditions for the subsequent amide grafting reaction. The introduction of a long-chain alkyl pyridinium salt, with a positively charged pyridinium salt group in the structure, allows it to attach to the bacterial cell membrane surface through electrostatic attraction. The interaction between the long-chain alkyl group and the phospholipid bilayer leads to the leakage of intracellular substances, causing bacterial death and exhibiting good antibacterial activity.

[0006] Step A2: Mix dicyclohexylcarbodiimide, 4-dimethylaminopyridine and dimethyl sulfoxide to obtain solution 1. Under nitrogen protection, mix chitosan, intermediate product 1 and dimethyl sulfoxide, stir, add solution 1 dropwise over 2 hours, react at room temperature for 48 hours, filter after reaction, add diethyl ether to separate, wash, add deionized water, stir at room temperature for 30 minutes, adjust pH to 3.5 with 0.3wt% hydrochloric acid aqueous solution, wash, and vacuum dry to obtain intermediate product 2. Furthermore, the ratio of solution 1, chitosan, intermediate product 1, dimethyl sulfoxide, diethyl ether, and deionized water is 120-150 mL: 10 g: 0.1-0.2 mol: 200-250 mL: 300 mL: 40-60 mL; Furthermore, the ratio of dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and dimethyl sulfoxide in solution 1 is 0.2-0.4 mol: 0.02-0.04 mol: 120-150 mL; In step A2, chitosan and intermediate 1 undergo an amide grafting reaction, and the cyano group is hydrolyzed to generate a carboxyl group, providing reaction conditions for the subsequent esterification reaction. Chitosan has good biocompatibility and antibacterial properties. Grafting long-chain pyridine salts onto chitosan improves the antibacterial efficiency of the system. At the same time, chitosan also has hemostatic and wound-healing effects.

[0007] Step A3: Mix intermediate product 2 obtained in step A2 with dichloromethane, add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and 4-dimethylaminopyridine, stir for 1 h, then add dextrorotatory borneol, stir at room temperature for 6 h, after the reaction is complete, wash, separate, dry, filter, rotary evaporate, purify, rotary evaporate, and vacuum dry to obtain modified chitosan; Further, the ratio of dichloromethane, EDC·HCl, 4-dimethylaminopyridine, dextrorotatory borneol, and intermediate 1 from step A2 is 100-150 mL : 0.2-0.4 mol : 0.02-0.04 mol : 0.12-0.24 mol : 0.1-0.2 mol; In step A3, intermediate 2 and dextrorotatory borneol undergo an esterification reaction. The introduced borneol is a bicyclic monoterpene natural membrane-active antibacterial agent with broad-spectrum antibacterial properties. It achieves its antibacterial effect by disrupting the phospholipid bilayer of bacterial cell membranes and interfering with their metabolic processes. The chitosan and the natural broad-spectrum antibacterial properties of borneol and the cationic antibacterial activity of pyridine salt form a synergistic effect, enhancing the antibacterial performance.

[0008] The modified gelatin is prepared by the following steps: Step B1: Mix 4-allylcatechol, cysteine, triethylamine and tetrahydrofuran, heat to 60°C under a nitrogen atmosphere, reflux for 12 h, cool to room temperature, rotary evaporate, wash three times with methanol and toluene respectively, purify and vacuum dry to obtain the catechol derivative. Furthermore, the ratio of 4-allylcatechol, cysteine, triethylamine, tetrahydrofuran, methanol, and toluene is 0.2-0.4 mol: 0.2-0.4 mol: 0.04-0.08 mol: 150-200 mL: 300 mL: 300 mL; In step B1, 4-allyl catechol and cysteine ​​undergo a thiol-ene click reaction, introducing an amino group into the system and providing reaction conditions for the subsequent Schiff base reaction. The introduced carboxyl group provides reaction conditions for the subsequent amide grafting reaction. The negative charge of the phenolic hydroxyl group of catechol can activate coagulation factor XII, promote coagulation, and improve the hemostatic ability of the dressing. In addition, the cross-linked quinone formed by the oxidation of the phenolic hydroxyl group under oxygen or alkaline conditions can form covalent bonds with thiols, amines, and imidazoles in extracellular matrix proteins and carbohydrates to enhance tissue adhesion, which is beneficial for hemostasis and wound healing.

[0009] Step B2: Mix hexadecaldehyde, ethanol and catechol derivative, heat to 70°C under nitrogen protection, stir and react for 8 hours, cool to room temperature, filter, wash the filter cake three times each with methanol and deionized water, and dry to obtain long-chain catechol derivative. Furthermore, the ratio of hexadecaldehyde, ethanol, catechol derivatives, methanol, and deionized water is 0.1-0.2 mol: 100-150 mL: 0.1-0.2 mol: 300 mL: 300 mL; In step B2, hexadecaldehyde and catechol derivatives undergo a Schiff base reaction. The introduced hydrophobic alkyl long chain can cause a certain degree of entanglement and blockage in the blood, delaying blood flow and thus achieving hemostasis.

[0010] Step B3: Mix fish skin gelatin and deionized water, add ethylenediamine and EDC·HCl, adjust the pH to 5 with 0.3wt% hydrochloric acid aqueous solution, react for 12h, dialyze, freeze dry to obtain amino-modified gelatin; Furthermore, the ratio of fish skin gelatin, deionized water, ethylenediamine, and EDC·HCl is 5-10g: 100-200mL: 16-32mL: 2.3-4.6g; In step B3, the carboxyl groups on the gelatin molecules undergo an amide reaction with the primary amino groups of ethylenediamine, introducing a large number of free amino groups onto the gelatin backbone, thereby achieving amino modification of the gelatin and providing reaction conditions for the subsequent amide grafting reaction.

[0011] Step B4: Mix EDC·HCl, N-hydroxysuccinimide and dimethyl sulfoxide, add to a long-chain catechol derivative solution, react at room temperature in the dark for 5 hours, then add it dropwise to a 3wt% amino-modified gelatin aqueous solution within 1 hour, react for 24 hours, dialyze and freeze dry to obtain modified gelatin. Furthermore, the ratio of EDC·HCl, N-hydroxysuccinimide, dimethyl sulfoxide, long-chain catechol derivative solution, and amino-modified gelatin aqueous solution is 0.015-0.025 mol: 0.012-0.022 mol: 25-50 mL: 25-50 mL: 200 mL; Furthermore, the long-chain catechol derivative solution is prepared by mixing long-chain catechol derivatives and dimethyl sulfoxide in a volume ratio of 0.02-0.04 mol: 25-50 mL; In step B4, amino-modified gelatin and long-chain catechol derivatives undergo an amide grafting reaction to graft catechol onto the gelatin. The gelatin has good biocompatibility, can adhere to wound tissue, reduce blood leakage in the interstitial space, and synergistically with phenolic hydroxyl and alkyl long chains to improve the hemostatic performance of the dressing.

[0012] A method for preparing a chitosan-based antibacterial dressing includes the following steps: Step S1: Weigh the raw materials according to the weight proportions, mix the propolis extract, glycerin, fucoidan oligosaccharide, carbomer, growth factor, modified chitosan and modified gelatin evenly, heat in a water bath at 40-60℃, and continue stirring for 30-60 minutes to obtain the functional dressing solution. Step S2: Attach the dressing surface layer to the adhesive tape layer, apply the functional dressing liquid evenly to the dressing surface layer to allow it to absorb the functional dressing liquid evenly, cover the dressing surface layer with a protective film, and obtain the chitosan-based antibacterial dressing after sterilization.

[0013] The beneficial effects of this invention are: The chitosan-based antibacterial dressing of this invention can be widely used in clinical wound care, surgical wound repair, chronic ulcer healing, and medical scenarios such as skin abrasions / burns. Modified chitosan, through surface grafting of long-chain pyridine salts and borneol groups, can effectively inhibit the adhesion and reproduction of common clinical pathogens such as Staphylococcus aureus and Escherichia coli, effectively blocking wound infection. Simultaneously, modified gelatin endows the dressing with excellent hemostatic properties, rapidly activating the body's coagulation mechanism, shortening wound bleeding time, reducing bleeding volume, and lowering the risk of complications such as shock and infection caused by excessive wound bleeding. Furthermore, this dressing also possesses good biocompatibility and biodegradability. Compared with existing technologies, the chitosan-based antibacterial dressing prepared by this invention has long-lasting and highly effective antibacterial properties, while also possessing excellent hemostatic function, showing broad application prospects in the field of medical wound care.

[0014] The modified chitosan of this invention first undergoes a nucleophilic substitution reaction between 5-cyanopyridine-2-carboxylic acid and 1-chlorododecane to introduce a long-chain alkyl pyridinium salt. The positively charged pyridinium salt group in the structure can attach to the bacterial cell membrane surface through electrostatic attraction. The interaction between the long-chain alkyl group and the phospholipid bilayer leads to the leakage of intracellular substances, causing bacterial death and exhibiting good antibacterial activity. Subsequently, an amide grafting reaction is performed with chitosan, and the cyano group is hydrolyzed to generate a carboxyl group. Chitosan possesses good biocompatibility and antibacterial properties. Grafting the long-chain pyridinium salt onto chitosan enhances the antibacterial efficiency of the system. Simultaneously, chitosan also has hemostatic and wound-healing properties. Finally, it undergoes an esterification reaction with dextrorotatory borneol. The introduced borneol is a natural membrane-active antibacterial agent of bicyclic monoterpenoid with broad-spectrum antibacterial properties. It achieves antibacterial effect by disrupting the phospholipid bilayer of bacterial cell membranes and interfering with their metabolic processes. The chitosan and the natural broad-spectrum antibacterial properties of borneol and the cationic antibacterial activity of pyridine salt form a synergistic effect, enhancing the antibacterial performance.

[0015] The modified gelatin of this invention first utilizes a thiol-ene click reaction between 4-allyl catechol and cysteine. The negative charge of the phenolic hydroxyl group of catechol can activate coagulation factor XII, promoting coagulation and improving the hemostatic ability of the dressing. Furthermore, the cross-linked quinone formed by the oxidation of the phenolic hydroxyl group under oxygen or alkaline conditions can form covalent bonds with thiols, amines, and imidazoles in extracellular matrix proteins and carbohydrates, enhancing tissue adhesion and promoting hemostasis and wound healing. Subsequently, a Schiff base reaction occurs with hexadecaldehyde, introducing hydrophobic alkyl long chains that can cause a certain degree of entanglement and blockage of blood, delaying blood flow and achieving hemostasis. Then, a large number of free amino groups are introduced onto the gelatin backbone, achieving amino modification of the gelatin. Finally, an amide grafting reaction is used to graft catechol onto the gelatin. The gelatin has good biocompatibility, can adhere to wound tissue, reduce blood leakage in the interstitial space, and synergistically improve the hemostatic performance of the dressing with the phenolic hydroxyl group and alkyl long chains. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1: Modified chitosan was prepared by the following steps: Step A1: Mix 5-cyanopyridine-2-carboxylic acid and acetonitrile, add 1-chlorododecane, heat to 100℃, reflux for 12 h. After the reaction is complete, rotary evaporate, purify, and concentrate under reduced pressure to obtain intermediate product 1. The ratio of 5-cyanopyridine-2-carboxylic acid, acetonitrile and 1-chlorododecane is 0.4 mol: 200 mL: 0.4 mol. Step A2: Mix dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and dimethyl sulfoxide to obtain solution 1. Under nitrogen protection, mix chitosan, intermediate product 1, and dimethyl sulfoxide, stir, and add solution 1 dropwise over 2 hours. React at room temperature for 48 hours. After the reaction is complete, filter, add diethyl ether for separation and washing, then add deionized water, stir at room temperature for 30 minutes, adjust the pH to 3.5 with 0.3wt% hydrochloric acid aqueous solution, wash, and vacuum dry to obtain intermediate product 2. The volume ratio of solution 1, chitosan, intermediate product 1, dimethyl sulfoxide, diethyl ether, and deionized water is 120mL:10g:0.1mol:200mL:300mL:40mL. The volume ratio of dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and dimethyl sulfoxide in solution 1 is 0.2mol:0.02mol:120mL. Step A3: Mix intermediate product 2 obtained in step A2 with dichloromethane, add EDC·HCl and 4-dimethylaminopyridine, stir for 1 h, then add dextrorotatory borneol, stir at room temperature for 6 h. After the reaction is complete, wash, separate, dry, filter, rotary evaporate, purify, rotary evaporate, and vacuum dry to obtain modified chitosan. The ratio of dichloromethane, EDC·HCl, 4-dimethylaminopyridine, dextrorotatory borneol and intermediate product 1 in step A2 is 100 mL: 0.2 mol: 0.02 mol: 0.12 mol: 0.1 mol.

[0018] Modified gelatin is prepared by the following steps: Step B1: Mix 4-allyl catechol, cysteine, triethylamine, and tetrahydrofuran. Under a nitrogen atmosphere, heat to 60°C and reflux for 12 hours. Cool to room temperature and rotary evaporate. Wash three times with methanol and toluene, purify, and vacuum dry to obtain the catechol derivative. The molar ratio of 4-allyl catechol, cysteine, triethylamine, tetrahydrofuran, methanol, and toluene is 0.2 mol: 0.2 mol: 0.04 mol: 150 mL: 300 mL: 300 mL. Step B2: Mix hexadecaldehyde, ethanol, and catechol derivative, heat to 70°C under nitrogen protection, stir for 8 hours, cool to room temperature, filter, wash the filter cake three times each with methanol and deionized water, and dry to obtain long-chain catechol derivative. The ratio of hexadecaldehyde, ethanol, catechol derivative, methanol, and deionized water is 0.1 mol: 100 mL: 0.1 mol: 300 mL: 300 mL. Step B3: Mix fish skin gelatin and deionized water, add ethylenediamine and EDC·HCl, adjust the pH to 5 with 0.3wt% hydrochloric acid aqueous solution, react for 12h, dialyze, and freeze dry to obtain amino-modified gelatin. The ratio of fish skin gelatin, deionized water, ethylenediamine and EDC·HCl is 5g:100mL:16mL:2.3g. Step B4: Mix EDC·HCl, N-hydroxysuccinimide, and dimethyl sulfoxide, add to a long-chain catechol derivative solution, and react at room temperature in the dark for 5 hours. Then, add it dropwise to a 3wt% amino-modified gelatin aqueous solution within 1 hour, react for 24 hours, dialyze, and freeze-dry to obtain modified gelatin. The ratio of EDC·HCl, N-hydroxysuccinimide, dimethyl sulfoxide, long-chain catechol derivative solution, and amino-modified gelatin aqueous solution is 0.015 mol: 0.012 mol: 25 mL: 25 mL: 200 mL. The long-chain catechol derivative solution is prepared by mixing long-chain catechol derivative and dimethyl sulfoxide at a ratio of 0.02 mol: 25 mL.

[0019] Example 2: Modified chitosan was prepared by the following steps: Step A1: Mix 5-cyanopyridine-2-carboxylic acid and acetonitrile, add 1-chlorododecane, heat to 100℃, reflux for 12 h. After the reaction is complete, rotary evaporate, purify, and concentrate under reduced pressure to obtain intermediate product 1. The ratio of 5-cyanopyridine-2-carboxylic acid, acetonitrile and 1-chlorododecane is 0.5 mol: 250 mL: 0.5 mol. Step A2: Mix dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and dimethyl sulfoxide to obtain solution 1. Under nitrogen protection, mix chitosan, intermediate product 1, and dimethyl sulfoxide, stir, and add solution 1 dropwise over 2 hours. React at room temperature for 48 hours. After the reaction is complete, filter, add diethyl ether for separation and washing, then add deionized water, stir at room temperature for 30 minutes, adjust the pH to 3.5 with 0.3wt% hydrochloric acid aqueous solution, wash, and vacuum dry to obtain intermediate product 2. The volume ratio of solution 1, chitosan, intermediate product 1, dimethyl sulfoxide, diethyl ether, and deionized water is 135mL:10g:0.15mol:225mL:300mL:50mL. The volume ratio of dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and dimethyl sulfoxide in solution 1 is 0.3mol:0.03mol:135mL. Step A3: Mix intermediate product 2 obtained in step A2 with dichloromethane, add EDC·HCl and 4-dimethylaminopyridine, stir for 1 h, then add dextrorotatory borneol, stir at room temperature for 6 h. After the reaction is complete, wash, separate, dry, filter, rotary evaporate, purify, rotary evaporate, and vacuum dry to obtain modified chitosan. The ratio of dichloromethane, EDC·HCl, 4-dimethylaminopyridine, dextrorotatory borneol and intermediate product 1 in step A2 is 125 mL: 0.3 mol: 0.03 mol: 0.18 mol: 0.15 mol.

[0020] Modified gelatin is prepared by the following steps: Step B1: Mix 4-allyl catechol, cysteine, triethylamine, and tetrahydrofuran. Under a nitrogen atmosphere, heat to 60°C and reflux for 12 hours. Cool to room temperature and evaporate by rotary evaporation. Wash three times with methanol and toluene, purify, and vacuum dry to obtain the catechol derivative. The molar ratio of 4-allyl catechol, cysteine, triethylamine, tetrahydrofuran, methanol, and toluene is 0.3 mol: 0.3 mol: 0.06 mol: 175 mL: 300 mL: 300 mL. Step B2: Mix hexadecaldehyde, ethanol, and catechol derivative, heat to 70°C under nitrogen protection, stir for 8 hours, cool to room temperature, filter, wash the filter cake three times each with methanol and deionized water, and dry to obtain long-chain catechol derivative. The ratio of hexadecaldehyde, ethanol, catechol derivative, methanol, and deionized water is 0.15 mol: 125 mL: 0.15 mol: 300 mL: 300 mL. Step B3: Mix fish skin gelatin and deionized water, add ethylenediamine and EDC·HCl, adjust the pH to 5 with 0.3wt% hydrochloric acid aqueous solution, react for 12h, dialyze, and freeze dry to obtain amino-modified gelatin. The ratio of fish skin gelatin, deionized water, ethylenediamine and EDC·HCl is 7.5g:150mL:24mL:3.45g. Step B4: Mix EDC·HCl, N-hydroxysuccinimide, and dimethyl sulfoxide, add to a long-chain catechol derivative solution, and react at room temperature in the dark for 5 hours. Then, add it dropwise to a 3wt% amino-modified gelatin aqueous solution within 1 hour, react for 24 hours, dialyze, and freeze-dry to obtain modified gelatin. The ratio of EDC·HCl, N-hydroxysuccinimide, dimethyl sulfoxide, long-chain catechol derivative solution, and amino-modified gelatin aqueous solution is 0.02 mol: 0.017 mol: 37.5 mL: 37.5 mL: 200 mL. The long-chain catechol derivative solution is prepared by mixing long-chain catechol derivative and dimethyl sulfoxide at a ratio of 0.03 mol: 37.5 mL.

[0021] Example 3: Modified chitosan was prepared by the following steps: Step A1: Mix 5-cyanopyridine-2-carboxylic acid and acetonitrile, add 1-chlorododecane, heat to 100℃, reflux for 12 h. After the reaction is complete, rotary evaporate, purify, and concentrate under reduced pressure to obtain intermediate product 1. The ratio of 5-cyanopyridine-2-carboxylic acid, acetonitrile and 1-chlorododecane is 0.6 mol: 300 mL: 0.6 mol. Step A2: Mix dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and dimethyl sulfoxide to obtain solution 1. Under nitrogen protection, mix chitosan, intermediate product 1, and dimethyl sulfoxide, stir, and add solution 1 dropwise over 2 hours. React at room temperature for 48 hours. After the reaction is complete, filter, add diethyl ether for separation and washing, then add deionized water, stir at room temperature for 30 minutes, adjust the pH to 3.5 with 0.3wt% hydrochloric acid aqueous solution, wash, and vacuum dry to obtain intermediate product 2. The volume ratio of solution 1, chitosan, intermediate product 1, dimethyl sulfoxide, diethyl ether, and deionized water is 150mL:10g:0.2mol:250mL:300mL:60mL. The volume ratio of dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and dimethyl sulfoxide in solution 1 is 0.4mol:0.04mol:150mL. Step A3: Mix intermediate product 2 obtained in step A2 with dichloromethane, add EDC·HCl and 4-dimethylaminopyridine, stir for 1 h, then add dextrorotatory borneol, stir at room temperature for 6 h. After the reaction is complete, wash, separate, dry, filter, rotary evaporate, purify, rotary evaporate, and vacuum dry to obtain modified chitosan. The ratio of dichloromethane, EDC·HCl, 4-dimethylaminopyridine, dextrorotatory borneol and intermediate product 1 in step A2 is 150 mL: 0.4 mol: 0.04 mol: 0.24 mol: 0.2 mol.

[0022] Modified gelatin is prepared by the following steps: Step B1: Mix 4-allyl catechol, cysteine, triethylamine, and tetrahydrofuran. Under a nitrogen atmosphere, heat to 60°C and reflux for 12 hours. Cool to room temperature and evaporate by rotary evaporation. Wash three times with methanol and toluene, purify, and vacuum dry to obtain the catechol derivative. The molar ratio of 4-allyl catechol, cysteine, triethylamine, tetrahydrofuran, methanol, and toluene is 0.4 mol: 0.4 mol: 0.08 mol: 200 mL: 300 mL: 300 mL. Step B2: Mix hexadecaldehyde, ethanol, and catechol derivative, heat to 70°C under nitrogen protection, stir for 8 hours, cool to room temperature, filter, wash the filter cake three times each with methanol and deionized water, and dry to obtain long-chain catechol derivative. The ratio of hexadecaldehyde, ethanol, catechol derivative, methanol, and deionized water is 0.2 mol: 150 mL: 0.2 mol: 300 mL: 300 mL. Step B3: Mix fish skin gelatin and deionized water, add ethylenediamine and EDC·HCl, adjust the pH to 5 with 0.3wt% hydrochloric acid aqueous solution, react for 12h, dialyze, and freeze dry to obtain amino-modified gelatin. The ratio of fish skin gelatin, deionized water, ethylenediamine and EDC·HCl is 10g:200mL:32mL:4.6g. Step B4: Mix EDC·HCl, N-hydroxysuccinimide, and dimethyl sulfoxide, add to a long-chain catechol derivative solution, and react at room temperature in the dark for 5 hours. Then, add it dropwise to a 3wt% amino-modified gelatin aqueous solution within 1 hour, react for 24 hours, dialyze, and freeze-dry to obtain modified gelatin. The ratio of EDC·HCl, N-hydroxysuccinimide, dimethyl sulfoxide, long-chain catechol derivative solution, and amino-modified gelatin aqueous solution is 0.025 mol: 0.022 mol: 50 mL: 50 mL: 200 mL. The long-chain catechol derivative solution is prepared by mixing long-chain catechol derivative and dimethyl sulfoxide at a ratio of 0.04 mol: 50 mL.

[0023] Example 4: A method for preparing a chitosan-based antibacterial dressing, comprising the following steps: The functional dressing solution comprises the following raw materials in parts by weight: 2 parts propolis extract, 1 part glycerin, 1 part fucoidan oligosaccharide, 0.5 parts carbomer, 0.001 parts growth factor, 2 parts modified chitosan prepared in Example 1, and 3 parts modified gelatin prepared in Example 1. The adhesive tape layer is a 15×15cm square with a thickness of 50μm, and is made of medical-grade non-toxic acrylic. The protective film and the adhesive tape layer have the same shape and size, and the thickness is 15μm. The material is silicone paper. Step S1: Weigh the raw materials according to the weight proportions, mix the propolis extract, glycerin, fucoidan oligosaccharide, carbomer, growth factor, modified chitosan prepared in Example 1 and modified gelatin prepared in Example 1 evenly, heat in a water bath at 40°C, and continue stirring for 30 minutes to obtain the functional dressing solution. Step S2: Apply pectin fiber cloth to the adhesive layer, apply functional dressing solution evenly to the pectin fiber cloth to allow it to absorb the functional dressing solution evenly, cover the pectin fiber cloth with a protective film, and sterilize to obtain chitosan-based antibacterial dressing.

[0024] Example 5: A method for preparing a chitosan-based antibacterial dressing, comprising the following steps: The functional dressing solution comprises the following raw materials in parts by weight: 3 parts propolis extract, 2 parts glycerin, 2 parts fucoidan, 0.5 parts carbomer, 0.003 parts growth factor, 3 parts modified chitosan prepared in Example 2, and 4.5 parts modified gelatin prepared in Example 2. The adhesive tape layer is a 15×15cm square with a thickness of 50μm, and is made of medical-grade non-toxic acrylic. The protective film and the adhesive tape layer have the same shape and size, and the thickness is 15μm. The material is silicone paper. Step S1: Weigh the raw materials according to the weight proportions, mix the propolis extract, glycerin, fucoidan oligosaccharide, carbomer, growth factor, modified chitosan prepared in Example 2 and modified gelatin prepared in Example 2 evenly, heat in a water bath at 50°C, and continue stirring for 40 minutes to obtain the functional dressing solution. Step S2: Place the cotton cloth on the adhesive tape layer, apply the functional dressing solution evenly to the cotton cloth to allow it to absorb the functional dressing solution evenly, cover the cotton cloth with a protective film, and sterilize to obtain chitosan-based antibacterial dressing.

[0025] Example 6: A method for preparing a chitosan-based antibacterial dressing, comprising the following steps: The functional dressing solution comprises the following raw materials in parts by weight: 4 parts propolis extract, 3 parts glycerin, 3 parts fucoidan, 1 part carbomer, 0.005 parts growth factor, 4 parts modified chitosan prepared in Example 3, and 6 parts modified gelatin prepared in Example 3. The adhesive tape layer is a 15×15cm square with a thickness of 50μm, and is made of medical-grade non-toxic acrylic. The protective film and the adhesive tape layer have the same shape and size, and the thickness is 15μm. The material is silicone paper. Step S1: Weigh the raw materials according to the weight proportions, mix the propolis extract, glycerin, fucoidan oligosaccharide, carbomer, growth factor, modified chitosan prepared in Example 3 and modified gelatin prepared in Example 3 evenly, heat in a water bath at 60°C, and continue stirring for 60 minutes to obtain the functional dressing solution. Step S2: Place the silk fabric on the adhesive layer, apply the functional dressing solution evenly to the silk fabric to allow it to absorb the functional dressing solution evenly, cover the silk fabric with a protective film, and sterilize to obtain chitosan-based antibacterial dressing.

[0026] Comparative Example 1: This comparative example is an antibacterial dressing, which differs from Example 6 in that it uses polyhexamethylene biguanide instead of the modified chitosan prepared in Example 3, and is otherwise the same.

[0027] Comparative Example 2: This comparative example is an antibacterial dressing. The difference between this example and Example 6 is that gelatin is used instead of the modified gelatin prepared in Example 3. All other aspects are the same.

[0028] Comparative Example 3: This comparative example is an antibacterial dressing. The difference between this example and Example 6 is that polyhexamethylene biguanide is used instead of the modified chitosan prepared in Example 3, and gelatin is used instead of the modified gelatin prepared in Example 3. All other aspects are the same.

[0029] The antibacterial dressings prepared in Examples 4-6 and Comparative Examples 1-3 were subjected to performance tests: Cytotoxicity test: The dressings were tested according to the test method of GB / T14233.2-2005, and none of the dressings showed cytotoxicity.

[0030] Mouse tail cutting hemostasis experiment: 84 five-week-old mice were randomly divided into 14 groups of 6 mice each. The mice were anesthetized and fixed. The tails of the mice were cut off 1 cm from the end with surgical scissors. If blood was spilled out, an antibacterial dressing was applied immediately. Timing started from the time the tail was cut off. Antibacterial test: Staphylococcus aureus, Escherichia coli and Candida albicans were used as experimental bacteria. The antibacterial dressing was placed in a constant temperature and humidity electric drying oven, with the temperature controlled at about 40±2℃ and the humidity at 75%±5%, and left for six months to test the antibacterial rate. Mouse wound healing experiment: 72 mice weighing 40±2g were divided into 12 groups. After anesthesia, an 8mm×8mm wound was made on the back of the mice. Antibacterial dressings were applied to each group, and the wound condition was observed on days 1, 3, 7, 12, 15, 18, and 22. If the wound was full of exudate, the dressing was changed immediately. Otherwise, the dressing was changed every two days until the wound was completely healed.

[0031] The test results are shown in Table 1: Table 1: Performance Test Results As can be seen from Table 1, the antibacterial dressing prepared by the present invention has good antibacterial properties, hemostatic effect, and wound healing promotion effect. In the antibacterial test, the antibacterial dressing prepared in the example can maintain an antibacterial rate of over 91% after 6 months. Comparing Example 6 and Comparative Example 1, it can be seen that the modified chitosan prepared by the present invention has good antibacterial properties and wound healing promotion function. Comparing Example 6 and Comparative Example 2, the modified gelatin prepared by the present invention has rapid hemostatic function and works synergistically with modified chitosan to further promote wound healing.

[0032] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A chitosan-based antibacterial dressing, characterized in that, It includes an adhesive tape layer, a dressing surface layer, and a protective film. The dressing surface layer is adsorbed with a functional dressing liquid, which includes the following raw materials in parts by weight: 2-4 parts propolis extract, 1-3 parts glycerin, 1-3 parts fucoidan, 0.5-1 part carbomer, 0.001-0.005 parts growth factor, 2-4 parts modified chitosan, and 3-6 parts modified gelatin. The modified chitosan is prepared by the following steps: Step A1: Mix 5-cyanopyridine-2-carboxylic acid and acetonitrile, add 1-chlorododecane, heat to 100℃, reflux for 12 h, after the reaction is completed, rotary evaporate, purify, concentrate under reduced pressure to obtain intermediate product 1; Step A2: Mix dicyclohexylcarbodiimide, 4-dimethylaminopyridine and dimethyl sulfoxide to obtain solution 1. Under nitrogen protection, mix chitosan, intermediate product 1 and dimethyl sulfoxide, stir, add solution 1 dropwise over 2 hours, react at room temperature for 48 hours, filter after reaction, add diethyl ether to separate, wash, add deionized water, stir at room temperature for 30 minutes, adjust pH to 3.5 with 0.3wt% hydrochloric acid aqueous solution, wash, and vacuum dry to obtain intermediate product 2. Step A3: Mix intermediate product 2 obtained in step A2 with dichloromethane, add EDC·HCl and 4-dimethylaminopyridine, stir for 1 h, then add dextrorotatory borneol, stir at room temperature for 6 h. After the reaction is complete, wash, separate, dry, filter, rotary evaporate, purify, rotary evaporate, and vacuum dry to obtain modified chitosan.

2. The chitosan-based antibacterial dressing according to claim 1, characterized in that, In step A1, the ratio of 5-cyanopyridine-2-carboxylic acid, acetonitrile, and 1-chlorododecane is 0.4-0.6 mol: 200-300 mL: 0.4-0.6 mol.

3. The chitosan-based antibacterial dressing according to claim 1, characterized in that, In step A2, the ratio of the amounts of solution 1, chitosan, intermediate product 1, dimethyl sulfoxide, diethyl ether, and deionized water is 120-150 mL: 10 g: 0.1-0.2 mol: 200-250 mL: 300 mL: 40-60 mL. The ratio of the amounts of dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and dimethyl sulfoxide in solution 1 is 0.2-0.4 mol: 0.02-0.04 mol: 120-150 mL.

4. The chitosan-based antibacterial dressing according to claim 1, characterized in that, In step A3, the ratio of dichloromethane, EDC·HCl, 4-dimethylaminopyridine, dextrorotatory borneol, and intermediate product 1 from step A2 is 100-150 mL: 0.2-0.4 mol: 0.02-0.04 mol: 0.12-0.24 mol: 0.1-0.2 mol.

5. The chitosan-based antibacterial dressing according to claim 1, characterized in that, The modified gelatin is prepared by the following steps: Step B1: Mix 4-allylcatechol, cysteine, triethylamine and tetrahydrofuran, heat to 60°C under a nitrogen atmosphere, reflux for 12 h, cool to room temperature, rotary evaporate, wash three times with methanol and toluene respectively, purify and vacuum dry to obtain the catechol derivative. Step B2: Mix hexadecaldehyde, ethanol and catechol derivative, heat to 70°C under nitrogen protection, stir and react for 8 hours, cool to room temperature, filter, wash the filter cake three times each with methanol and deionized water, and dry to obtain long-chain catechol derivative. Step B3: Mix fish skin gelatin and deionized water, add ethylenediamine and EDC·HCl, adjust the pH to 5 with 0.3wt% hydrochloric acid aqueous solution, react for 12h, dialyze, and freeze dry to obtain amino-modified gelatin. The ratio of fish skin gelatin, deionized water, ethylenediamine and EDC·HCl is 5-10g: 100-200mL: 16-32mL: 2.3-4.6g. Step B4: Mix EDC·HCl, N-hydroxysuccinimide and dimethyl sulfoxide, add to a long-chain catechol derivative solution, and react at room temperature in the dark for 5 hours. Then, add it dropwise to a 3wt% amino-modified gelatin aqueous solution within 1 hour, react for 24 hours, dialyze, and freeze dry to obtain modified gelatin.

6. The chitosan-based antibacterial dressing according to claim 5, characterized in that, In step B1, the ratio of 4-allylcatechol, cysteine, triethylamine, tetrahydrofuran, methanol, and toluene is 0.2-0.4 mol: 0.2-0.4 mol: 0.04-0.08 mol: 150-200 mL: 300 mL: 300 mL.

7. The chitosan-based antibacterial dressing according to claim 5, characterized in that, In step B2, the ratio of hexadecaldehyde, ethanol, catechol derivative, methanol and deionized water is 0.1-0.2 mol: 100-150 mL: 0.1-0.2 mol: 300 mL: 300 mL.

8. The chitosan-based antibacterial dressing according to claim 5, characterized in that, In step B4, the ratio of EDC·HCl, N-hydroxysuccinimide, dimethyl sulfoxide, long-chain catechol derivative solution, and amino-modified gelatin aqueous solution is 0.015-0.025 mol: 0.012-0.022 mol: 25-50 mL: 25-50 mL: 200 mL. The long-chain catechol derivative solution is prepared by mixing long-chain catechol derivative and dimethyl sulfoxide in a ratio of 0.02-0.04 mol: 25-50 mL.

9. The chitosan-based antibacterial dressing according to claim 1, characterized in that, The dressing surface layer is made of one of the following materials: pectin fiber cloth, cotton cloth, or silk cloth. The adhesive layer is a 15×15cm square with a thickness of 50μm and is made of medical non-toxic acrylic. The protective film has the same shape and size as the adhesive layer, a thickness of 15μm, and is made of silicone paper.

10. A method for preparing the chitosan-based antibacterial dressing according to any one of claims 1-9, characterized in that, The chitosan-based antibacterial dressing is prepared by the following steps: Step S1: Weigh the raw materials according to the weight proportions, mix the propolis extract, glycerin, fucoidan oligosaccharide, carbomer, growth factor, modified chitosan and modified gelatin evenly, heat in a water bath at 40-60℃, and continue stirring for 30-60 minutes to obtain the functional dressing solution. Step S2: Attach the dressing surface layer to the adhesive tape layer, apply the functional dressing liquid evenly to the dressing surface layer to allow it to absorb the functional dressing liquid evenly, cover the dressing surface layer with a protective film, and obtain the chitosan-based antibacterial dressing after sterilization.

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