A long-acting protective chitosan-based antibacterial wound dressing and a preparation method and application thereof

Abstract

The application belongs to the field of biomedical materials, and discloses a long-acting protective chitosan-based antibacterial wound dressing and a preparation method and application thereof. The application is a long-acting protective chitosan-based antibacterial wound dressing which can be directly applied in dry and wet states through the agglomeration of chitosan quaternary ammonium salt and folic acid and the strong chelation of the surface metal ions of the nano antibacterial agent and the carboxyl group of folic acid. The wet state can be directly applied to a wound, and a stable protective barrier can be formed after being attached to a wound surface, the adhesion is excellent, and the wet state is water-resistant and not easy to fall off. The antibacterial agent can play an antibacterial role and promote wound repair and healing. The dry state can be quickly converted into a hydrogel state when contacting a water-containing medium, has excellent adhesion, and then forms a stable protective barrier. The initial structure is stable, can respond to the wound environment to realize controllable degradation, and does not need to be removed when changing dressings. Meanwhile, the growth and reproduction of bacteria can be inhibited, and wound healing can be promoted.

Description

Technical Field

[0001] This invention belongs to the field of biomedical materials, and specifically relates to a chitosan-based antibacterial wound dressing that provides long-lasting protection, its preparation method, and its application. Background Technology

[0002] Traditional dressings primarily provide basic protection and lack antibacterial and healing-promoting capabilities. For example, gauze and petroleum jelly gauze only offer basic physical isolation and exudate absorption; they lack antibacterial activity, are easily contaminated by wound secretions, and thus increase the risk of infection. They also tend to adhere to the wound, causing secondary damage during changes, and offer no active role in promoting wound healing. They are only suitable for superficial, clean wounds and cannot meet the needs of complex wound repair. While commercially available natural polymer healing dressings (ointments or sponges) containing collagen, hyaluronic acid, and chitosan can provide a moist microenvironment and promote epithelial cell migration, the healing-promoting effect of a single component is limited. Ointment dressings work by drying to form a thin polymer network, which cannot cope with complex wound environments, such as rapid degradation, dissolution upon contact with exudate, and weak adhesion. While sponges are relatively stable, they easily shift and detach in areas with wound exudate or during activity, especially during daily washing and rinsing, where neither ointments nor sponges can form a stable barrier to prevent infection. Current dressings generally lack controllable degradation capabilities, making it difficult to achieve long-term adaptability and drug delivery according to different physiological environments. For example, the oral wound environment is weakly acidic to neutral (pH approximately 6.65), where ordinary dressings dissolve rapidly and cannot maintain a barrier structure for a long time, hindering long-term therapeutic effects. Furthermore, the exudate from skin wounds contains a large amount of salt ions, causing some materials to over-swell and structurally disintegrate, making it impossible to maintain stable drug release. Therefore, designing a multifunctional absorbable material with excellent wound adhesion, structural stability in exudate and everyday water contact environments, and strong antibacterial and healing-promoting capabilities—enabling it to form a long-term stable protective layer on the wound, achieve controllable degradation and long-term drug delivery, be unaffected by exudate, effectively inhibit infection risk under everyday water contact conditions, and simultaneously promote wound repair—remains a significant challenge.

[0003] It is worth noting that for various chronic wounds, existing ointment dressings lack controlled-release capabilities for antibacterial agents such as nano-silver, and their rapid release can easily cause tissue toxicity. Block dressings, on the other hand, have excessively strong fixation capabilities for antibacterial agents but weak bactericidal ability in deep tissues. Slow degradation in response to the wound environment is crucial for achieving long-term drug delivery, reducing dressing changes, and avoiding secondary damage, directly impacting wound healing rates. Current dressing research has failed to find a low-cost solution that combines the characteristics of being suitable for both dry and wet use, constructing a long-lasting barrier, providing antibacterial properties, and promoting wound healing. Therefore, there is an urgent need for a safe and effective medical dressing that can be easily prepared to meet clinical needs. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a chitosan-based antibacterial wound dressing that provides long-lasting protection.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned chitosan-based antibacterial wound dressing with long-lasting protection.

[0006] Another object of the present invention is to provide an application of the above-mentioned chitosan-based antibacterial wound dressing that provides long-lasting protection.

[0007] The objective of this invention is achieved through the following solution:

[0008] A chitosan-based antibacterial wound dressing that provides long-lasting protection is made from chitosan quaternary ammonium salt, folic acid, and nano-antibacterial agents.

[0009] The degree of quaternary ammonium group substitution of the chitosan quaternary ammonium salt is 30-99.8%, and the molecular weight of the chitosan quaternary ammonium salt is 1.0 × 10⁻⁶. 4 -20×10 4 Da; The nano antibacterial agent refers to one or more of nano metals and nano metal oxides with biocompatibility and antibacterial properties, including one or more of nano zinc oxide, nano silver, nano silver oxide, nano copper, nano copper sulfide, nano copper oxide, nano titanium dioxide, nano magnesium oxide, nano iron oxide and nano gold.

[0010] The preparation method of the above-mentioned long-lasting protective chitosan-based antibacterial wound dressing is carried out according to the following steps: (1) Disperse folic acid in deionized water and adjust the pH value with sodium hydroxide solution to obtain folic acid solution; (2) Chitosan quaternary ammonium salt is dissolved in deionized water to obtain chitosan quaternary ammonium salt solution, and nano antibacterial agent is dispersed in deionized water to obtain nano antibacterial agent dispersion. Under stirring, chitosan quaternary ammonium salt solution and nano antibacterial agent dispersion are mixed evenly, and ultrasonic treatment is performed to obtain chitosan quaternary ammonium salt-nano antibacterial agent mixture. (3) Add the folic acid solution obtained in step (1) dropwise to the chitosan quaternary ammonium salt-nano antibacterial agent mixture obtained in step (2). After the addition is complete, stir evenly and let stand to allow the reaction to be complete, and obtain a viscous aggregate, which is a wet chitosan-based antibacterial wound dressing that can provide long-lasting protection. (4) Take the viscous aggregate obtained in step (3) and make it into a uniform film using a coating tool; then place it on a flat dryer to dry it to obtain a patch, which is a dry chitosan-based antibacterial wound dressing that can provide long-lasting protection.

[0011] The folic acid solution in step (1) has a mass-volume percentage concentration of 0.05%-4%; the pH value is 9.0-12.0.

[0012] The chitosan quaternary ammonium salt solution in step (2) has a mass-volume percentage concentration of 0.05%-4%; the nano antibacterial agent dispersion has a mass-volume percentage concentration of 0.05%-2%; and the nano antibacterial agent dispersion and the chitosan quaternary ammonium salt solution are mixed at a volume ratio of 0.05:10 to 1:10.

[0013] The ultrasonic power in step (2) is 200W-600W, the ultrasonic temperature is 25℃-40℃, and the ultrasonic time is 0-180 minutes.

[0014] In step (3), the chitosan quaternary ammonium salt-nano antibacterial agent mixture and folic acid solution are mixed at a volume ratio of 1:0.5-1:5; the standing time is 15 minutes to 3 days.

[0015] The thickness of the patch in step (4) is 20μm-400μm; the drying temperature is 40℃-50℃ and the drying time is 8-72 hours.

[0016] The aforementioned chitosan-based antibacterial wound dressing, which provides long-lasting protection, can be used as a medical dressing in the preparation of oral ulcer patches and wound repair dressings.

[0017] The aforementioned chitosan-based antibacterial wound dressing, which provides long-lasting protection, can be used as a biomedical material or cosmetic in the preparation of drug delivery systems, acne treatment drugs, or cosmetic adhesives.

[0018] This invention utilizes the aggregation effect of chitosan quaternary ammonium salt and folic acid (moderate hydrogen bonding and electrostatic interaction), as well as the strong chelation effect between metal ions on the surface of the nano-antibacterial agent and the carboxyl groups of folic acid, to assemble a viscous composite aggregate driven by multiple physical interactions. This composite aggregate is viscous in a wet state, and after drying, it can form a patch and achieve rapid adhesion after absorbing water, thus it can be made into ointments and dry patches for application. In a wet state, the fluidity of the formed viscous agglomerates is affected by the molecular weight of chitosan quaternary ammonium salt. Agglomerates made with low molecular weight chitosan quaternary ammonium salt are fluid and self-adaptive, can be applied to wounds, and are resistant to water rinsing, preventing bacteria in the water from contacting the wound, forming a stable protective barrier, and reducing the risk of wound infection. The antibacterial agent in the viscous agglomerate has an antibacterial effect, inhibiting the growth and reproduction of bacteria. When applied to wounds, this viscous agglomerate has high biocompatibility and responds to salt ions in wound exudate, and will slowly degrade, so it does not need to be removed when changing dressings, avoiding secondary damage to the wound. On the other hand, agglomerates made with high molecular weight chitosan quaternary ammonium salt are non-flowing, like putty, and still have adhesiveness, and can be filled into deeper wounds for antibacterial and healing-promoting treatment. The dressing, made into a dry patch, can transform into an adhesive aggregate in a short time when it comes into contact with the exudate of an open wound. It adheres to the wound and forms a moist antibacterial barrier, which can absorb inflammatory factors in the wound exudate, reduce local inflammatory response, inhibit bacterial growth and reproduction, and promote wound healing. The patch is non-adhesive when dry, making it easy to transport and store, and has strong adhesiveness after rehydration.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] (1) This invention utilizes the aggregation effect of chitosan quaternary ammonium salt and folic acid, combined with the strong chelation effect between nano antibacterial agent and folic acid, to obtain a chitosan-based antibacterial wound dressing that can provide long-lasting protection; the long-lasting protective effect of this dressing is due to the excellent stability, enhanced mechanical strength and good adhesion of the system.

[0021] (2) The molding method of the present invention is entirely based on the physical interaction between the raw materials. This strong interaction makes the dressing completely non-degradable in pure water environment, while having long-lasting stability (>24 h) in body fluid environment (equivalent to salt solution), and slowly degrading within a week.

[0022] (3) The physical interaction between the raw materials utilized in this invention has a dynamic effect, thus it can have the effect of slow-release antibacterial agent, avoiding the problem of ointment releasing too quickly and block dressing releasing too slowly.

[0023] (4) The wet dressing or dry composite patch obtained by the present invention can adhere to the wound to form an antibacterial barrier. Combined with the functions of chitosan quaternary ammonium salt and folic acid, it has both antibacterial and repair-promoting properties, and has excellent wound healing performance.

[0024] (5) The preparation method provided by the present invention is low-cost, simple and green, and does not require high equipment requirements and does not require the addition of an initiator.

[0025] (6) The folic acid, chitosan quaternary ammonium salt and low content antibacterial agent used in the dressing formulation of the present invention will not cause cytotoxicity and have no potential hazards.

[0026] (7) The hydrogel obtained by the present invention can exhibit different forms due to the different molecular weights of chitosan quaternary ammonium salts. The hydrogel prepared by low molecular weight chitosan quaternary ammonium salts is a fluid dynamic aggregate with self-adaptability and can be applied to wounds; while the aggregate prepared by high molecular weight chitosan quaternary ammonium salts is in the form of putty and can be filled into deeper wounds for treatment. Attached Figure Description

[0027] Figure 1 The images show the morphology and adhesion test results of the patch prepared in Example 3. (a), (b), and (c) are actual photographs of the patch, (d), (e), and (f) show the process of the patch regaining its tackiness after adding water, and (g), (h), and (i) show the adhesion of the 2.0 cm × 2.0 cm patch to a wet glass surface and weights. Figure 2 The images show the morphology of the viscous aggregates obtained in Examples 1-5 and Comparative Example 1, as well as the products obtained in Comparative Examples 2-3. Figure 3 The images show the adhesion and water resistance of the viscous aggregates and patches prepared in Examples 4 and 5 on the back of the hand. Figure 4 The graph shows the degradation of the patches prepared in Example 3 and Comparative Example 1 with four commercial oral ulcer dressings in oral simulated liquid. The left graph shows the degradation of the oral simulated liquid in each sample group, and the right graph shows the degradation rate of the patch prepared in Example 3 in oral simulated liquid. Figure 5 The images show the healing of full-thickness skin defects in diabetic rats using patches prepared in Example 3 and Comparative Example 1, as well as in the blank group and the commercial sample group. The left image shows the actual wounds of each group of rats on postoperative days 1, 3, 5, 7, 9, 11, and 14; the right image is a bar chart showing the wound healing rate of each group of rats at different time points. Figure 6 The images show antibacterial experiments on the viscous aggregates prepared in Example 3 and Comparative Example 1. The left image shows colony photos on agar plates after the two strains were treated with different samples; the right image shows a bar chart of bacterial survival rates for each group. Figure 7 Fourier transform infrared spectra of the viscous aggregates prepared in Example 3 and Comparative Example 1, as well as folic acid and chitosan quaternary ammonium salt. Detailed Implementation

[0028] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings, but the implementation methods and protection scope of the present invention are not limited thereto.

[0029] Unless otherwise specified, all raw materials used in the following examples are commercially available products. Folic acid (purity ≥97%), glacial acetic acid (purity ≥99.9%), 2,3-epoxypropyltrimethylammonium chloride (purity ≥95%), nano titanium dioxide (purity ≥99.8%), anhydrous copper sulfate (purity ≥99.0%), sodium thiosulfate pentahydrate (purity ≥99.9%), zinc acetate dihydrate (purity ≥99.99%), urea (purity ≥99%), anhydrous magnesium chloride (purity ≥99.9%), tetrachloroauric acid trihydrate (purity ≥99%), trisodium citrate (purity ≥98%), and anhydrous ferric chloride (purity ≥99.9%) were all purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Isopropanol (purity ≥99.7%) was purchased from Tianjin Damao Chemical Reagent Partnership; acetone (purity ≥99.5%) was purchased from Guangdong Guangshi Reagent Technology Co., Ltd.; sodium hydroxide (purity ≥99%) was purchased from Tianjin Zhiyuan Chemical Reagent Co., Ltd.; anhydrous ethanol (purity ≥99.5%) was purchased from Tianjin Damao Chemical Reagent Partnership; silver nitrate (purity ≥99.8%) was purchased from Chengdu Kelong Chemical Co., Ltd.; ascorbic acid (purity ≥99.99%), hydrochloric acid standard solution (0.01M), and hydrogen peroxide (30%) were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; deionized water was prepared in the laboratory.

[0030] Chitosan quaternary ammonium salts with different molecular weights and degrees of substitution were prepared in the laboratory according to the following preparation method: Chitosan (deacetylation degree ≥98%, purchased from Shandong Haiyihua Biotechnology Co., Ltd.) was dissolved in glacial acetic acid, purified by sodium hydroxide alkaline precipitation, and then dispersed evenly in isopropanol. The molar ratio of chitosan to 2,3-epoxypropyltrimethylammonium chloride was controlled at 1:1 to 1:8. The reaction was carried out at 80℃ for 6 hours. After purification with acetone, dialysis to remove impurities, and freeze-drying, chitosan quaternary ammonium salts with different degrees of substitution were obtained. Then, hydrogen peroxide was used as a degrading agent to oxidize and degrade the chitosan at a constant temperature of 60℃. After purification by dialysis and freeze-drying, chitosan quaternary ammonium salts with different molecular weights were finally obtained.

[0031] Nano-silver was prepared by dissolving silver nitrate in deionized water and heating it to boiling. Trisodium citrate solution was added dropwise to the boiling solution, and the mixture was continuously boiled and refluxed until the solution turned grayish-yellow. The system was then stirred and cooled to room temperature to obtain nano-silver.

[0032] Nano-silver oxide was prepared by the following method: silver nitrate was dissolved in deionized water, and dilute sodium hydroxide solution was slowly added dropwise to the silver nitrate aqueous solution. After the addition was completed, the mixture was stirred for 30 minutes, allowed to stand for 30 minutes, washed clean by centrifugation with water and anhydrous ethanol, and dried under vacuum in the dark to obtain nano-silver oxide.

[0033] Nano-copper was prepared by the following method: anhydrous copper sulfate was dissolved in deionized water, and the pH of the system was adjusted to 8.5 with dilute sodium hydroxide solution; dilute ascorbic acid aqueous solution was slowly added dropwise under continuous stirring, and the reaction was carried out at 80°C for 90 minutes; the product was washed by centrifugation with anhydrous ethanol and water and then vacuum dried to obtain nano-copper.

[0034] The nano-copper sulfide was prepared by the following method: copper sulfate and sodium thiosulfate pentahydrate were dissolved in deionized water, stirred and mixed evenly at room temperature, and then placed in a microwave reactor with a power of 300 W for 20 minutes; the product was washed by centrifugation with anhydrous ethanol and water, and vacuum dried to obtain nano-copper sulfide powder.

[0035] Nano-copper oxide was prepared by the following method: copper nitrate was dissolved in deionized water, and dilute sodium hydroxide solution was added dropwise under uniform stirring at room temperature; after the addition was completed, stirring was continued for 30 minutes, and the mixture was allowed to stand for 30 minutes to age. The mixture was then washed clean by centrifugation with water and anhydrous ethanol, dried, and placed in a muffle furnace for calcination at 300°C to obtain nano-copper oxide.

[0036] Nano zinc oxide was prepared as follows: Zinc acetate dihydrate was dissolved in deionized water, and the solution was stirred by ultrasonication until fully dissolved. The solution was stirred at a constant temperature of 85°C in a water bath, and dilute sodium hydroxide solution was slowly added dropwise until the pH reached 11. Water at the same temperature was added to a final volume of 40 mL, and the reaction was continued for 4 hours. The product was washed with anhydrous ethanol and water by centrifugation until the pH reached 7. The product was then dispersed evenly with deionized water and stored at 4°C to obtain nano zinc oxide.

[0037] Nano-magnesium oxide was prepared by the following method: anhydrous magnesium chloride and urea were dissolved in deionized water and reacted by stirring in a water bath at 90°C; after the reaction was completed, the mixture was cooled, washed clean by centrifugation with deionized water, dried, and then placed in a muffle furnace and calcined in an air atmosphere at 520°C to obtain nano-magnesium oxide.

[0038] Nano-iron oxide was prepared by the following method: anhydrous ferric chloride was dissolved in dilute hydrochloric acid aqueous solution, and stirred under constant temperature reflux in an oil bath at 95°C for 2 hours. The product was washed with dilute hydrochloric acid and water by centrifugation, the precipitate was collected by centrifugation, and dried to obtain nano-iron oxide.

[0039] Nanogold was prepared as follows: Tetrachloroauric acid trihydrate was dissolved in deionized water and heated to boiling. Dilute trisodium citrate aqueous solution was added at once under stirring. The mixture was kept boiling and refluxed for 15 minutes. The precipitate was collected by centrifugation to obtain nanogold.

[0040] Example 1

[0041] (1) Disperse 2 g of folic acid in deionized water to prepare a solution with a mass-volume percentage concentration of 0.05% (w / v, i.e., 0.05 g of folic acid in 100 mL of solution). Adjust the pH value to 12.0 using sodium hydroxide solution to obtain a folic acid solution. (2) Add 2 g of chitosan quaternary ammonium salt (molecular weight 5.0 × 10⁻⁶) 4 Chitosan (with a quaternary ammonium group substitution degree of 30%) was dissolved in deionized water to prepare a chitosan quaternary ammonium salt solution with a mass-volume percentage concentration of 0.05% (w / v, i.e., 0.05 g of chitosan quaternary ammonium salt in 100 mL of chitosan quaternary ammonium salt solution). Nano-antibacterial agents (nano-silver, nano-silver oxide, and nano-copper in a mass ratio of 2:1:1) were dispersed in deionized water to prepare a nano-antibacterial agent dispersion with a mass-volume percentage concentration of 2% (w / v, i.e., 2 g of nano-antibacterial agent in 100 mL of nano-antibacterial agent dispersion). Under stirring, the nano-antibacterial agent dispersion and the chitosan quaternary ammonium salt solution were mixed evenly at a volume ratio of 0.05:10. The ultrasonic power was set to 200 W, the ultrasonic temperature to 25℃, and the ultrasonic time to 180 minutes. After ultrasonic treatment, a chitosan quaternary ammonium salt-nano-antibacterial agent mixture was obtained. (3) Add the folic acid solution obtained in step (1) dropwise to the chitosan quaternary ammonium salt-nano antibacterial agent mixture obtained in step (2). The volume ratio of the chitosan quaternary ammonium salt-nano antibacterial agent mixture to the folic acid solution is controlled at 1:5. After the addition is complete, stir evenly and let stand for 15 minutes to allow the reaction to be complete, and obtain a viscous aggregate, which is a wet chitosan-based antibacterial wound dressing that can provide long-lasting protection. (4) Take out the viscous aggregate obtained in step (3), make a film with a coating tool, and then place it on a flat dryer to dry at 45°C for 8 hours to obtain a patch with a thickness of 20 μm, which is a dry chitosan-based antibacterial wound dressing that can provide long-lasting protection.

[0042] Example 2 (1) Disperse 2 g of folic acid in deionized water to prepare a solution with a mass-volume percentage concentration of 4% (w / v, i.e., 4 g of folic acid in 100 mL of solution). Adjust the pH value to 11.0 using sodium hydroxide solution to obtain a folic acid solution. (2) Add 2 g of chitosan quaternary ammonium salt (molecular weight 10.0 × 10⁻⁶) 4Chitosan (with a quaternary ammonium group substitution degree of 65%) was dissolved in deionized water to prepare a chitosan quaternary ammonium salt solution with a mass-volume percentage concentration of 4% (w / v, i.e., 4 g of chitosan quaternary ammonium salt in 100 mL of chitosan quaternary ammonium salt solution). Nano-antibacterial agents (nano-copper sulfide and nano-copper oxide in a mass ratio of 1:3) were dispersed in deionized water to prepare a nano-antibacterial agent dispersion with a mass-volume percentage concentration of 1% (w / v, i.e., 1 g of nano-antibacterial agent in 100 mL of nano-antibacterial agent dispersion). Under stirring, the nano-antibacterial agent dispersion and the chitosan quaternary ammonium salt solution were mixed evenly at a volume ratio of 0.5:10. The ultrasonic power was set to 400 W, the ultrasonic temperature to 30℃, and the ultrasonic time to 120 minutes. After ultrasonic treatment, a chitosan quaternary ammonium salt-nano-antibacterial agent mixture was obtained. (3) Add the folic acid solution obtained in step (1) dropwise to the chitosan quaternary ammonium salt-nano antibacterial agent mixture obtained in step (2). The volume ratio of the chitosan quaternary ammonium salt-nano antibacterial agent mixture to the folic acid solution is controlled at 1:0.5. After the addition is complete, stir evenly and let stand for 1 day to allow the reaction to complete, and obtain a viscous aggregate, which is a wet chitosan-based antibacterial wound dressing that can provide long-lasting protection. (4) Take out the viscous aggregate obtained in step (3), make it into a film with a coating tool, and then place it on a flat dryer to dry at 45°C for 36 hours to obtain a patch with a thickness of 100 μm, which is a dry chitosan-based antibacterial wound dressing that can provide long-lasting protection.

[0043] Example 3 (1) Disperse 2 g of folic acid in deionized water to prepare a solution with a mass-volume percentage concentration of 2% (w / v, i.e., 2 g of folic acid in 100 mL of solution). Adjust the pH value to 10.0 using sodium hydroxide solution to obtain a folic acid solution. (2) Add 2 g of chitosan quaternary ammonium salt (molecular weight 20.0 × 10⁻⁶) 4 Chitosan quaternary ammonium salt solution (with a quaternary ammonium group substitution degree of 99.8%) was dissolved in deionized water to prepare a chitosan quaternary ammonium salt solution with a mass-volume percentage concentration of 1% (w / v, i.e., 1 g of chitosan quaternary ammonium salt is contained in 100 mL of chitosan quaternary ammonium salt solution); nano zinc oxide was dispersed in deionized water to prepare a nano antibacterial agent dispersion with a mass-volume percentage concentration of 0.05% (w / v, i.e., 0.05 g of nano zinc oxide is contained in 100 mL of nano antibacterial agent dispersion); under stirring, the nano antibacterial agent dispersion and the chitosan quaternary ammonium salt solution were mixed evenly at a volume ratio of 1:10, and the ultrasonic power was set to 600 W, the ultrasonic temperature to 40℃, and the ultrasonic time to 30 minutes. After ultrasonic treatment, a chitosan quaternary ammonium salt-nano antibacterial agent mixture was obtained. (3) Add the folic acid solution obtained in step (1) dropwise to the chitosan quaternary ammonium salt-nano antibacterial agent mixture obtained in step (2). The volume ratio of the chitosan quaternary ammonium salt-nano antibacterial agent mixture to the folic acid solution is controlled at 1:2. After the addition is complete, stir evenly and let stand for 3 days to complete the reaction and obtain a viscous aggregate, which is a wet chitosan-based antibacterial wound dressing that can provide long-lasting protection. (4) Take out the viscous aggregate obtained in step (3), make a film with a coating tool, and then place it on a flat dryer at 50°C for 72 hours to obtain a patch with a thickness of 200 μm, which is a dry chitosan-based antibacterial wound dressing that can provide long-lasting protection.

[0044] Example 4 (1) Disperse 2 g of folic acid in deionized water to prepare a solution with a mass-volume percentage concentration of 1% (w / v, i.e., 1 g of folic acid in 100 mL of solution), and adjust the pH value to 9.0 using sodium hydroxide solution to obtain a folic acid solution; (2) Add 2 g of chitosan quaternary ammonium salt (molecular weight 1.0 × 10⁻⁶) 4 Chitosan (with a quaternary ammonium group substitution degree of 95%) was dissolved in deionized water to prepare a chitosan quaternary ammonium salt solution with a mass-volume percentage concentration of 2% (w / v, i.e., 2 g of chitosan quaternary ammonium salt in 100 mL of chitosan quaternary ammonium salt solution). Nano-antibacterial agents (nano-titanium dioxide and nano-magnesium oxide in a mass ratio of 1:1) were dispersed in deionized water to prepare a nano-antibacterial agent dispersion with a mass-volume percentage concentration of 0.5% (w / v, i.e., 0.5 g of nano-antibacterial agent in 100 mL of nano-antibacterial agent dispersion). Under stirring, the nano-antibacterial agent dispersion and the chitosan quaternary ammonium salt solution were mixed evenly at a volume ratio of 0.1:10. The ultrasonic power was set to 800 W, the ultrasonic temperature to 30℃, and the ultrasonic time to 60 minutes. After ultrasonic treatment, a chitosan quaternary ammonium salt-nano-antibacterial agent mixture was obtained. (3) Add the folic acid solution obtained in step (1) dropwise to the chitosan quaternary ammonium salt-nano antibacterial agent mixture obtained in step (2). The volume ratio of the chitosan quaternary ammonium salt-nano antibacterial agent mixture to the folic acid solution is controlled at 1:1. After the addition is complete, stir evenly and let stand for 2 days until the reaction is complete to obtain a viscous aggregate, which is a wet chitosan-based antibacterial wound dressing that can provide long-lasting protection. (4) Take out the viscous aggregate obtained in step (3), make it into a film with a coating tool, and then place it on a flat dryer to dry at 40°C for 24 hours to obtain a patch with a thickness of 400 μm, which is a dry chitosan-based antibacterial wound dressing that can provide long-lasting protection.

[0045] Example 5 (1) Disperse 2 g of folic acid in deionized water to prepare a solution with a mass-volume percentage concentration of 1% (w / v, i.e., 1 g of folic acid in 100 mL of solution), and adjust the pH value to 9.0 using sodium hydroxide solution to obtain a folic acid solution; (2) Add 2 g of chitosan quaternary ammonium salt (molecular weight 15.0 × 10⁻⁶) 4 Chitosan (46% quaternary ammonium group substitution) was dissolved in deionized water to prepare a chitosan quaternary ammonium salt solution with a mass-volume percentage concentration of 0.05% (w / v, i.e., 0.05 g of chitosan quaternary ammonium salt in 100 mL of chitosan quaternary ammonium salt solution); nano-antibacterial agents (nano-iron oxide and nano-gold in a mass ratio of 1:3) were dispersed in deionized water to prepare a nano-antibacterial agent dispersion with a mass-volume percentage concentration of 0.1% (w / v, i.e., 0.1 g of nano-antibacterial agent in 100 mL of nano-antibacterial agent dispersion); under stirring, the nano-antibacterial agent dispersion and the chitosan quaternary ammonium salt solution were mixed evenly at a volume ratio of 0.05:10 to obtain a chitosan quaternary ammonium salt-nano-antibacterial agent mixture; (3) Add the folic acid solution obtained in step (1) dropwise to the chitosan quaternary ammonium salt-nano antibacterial agent mixture in step (2). The volume ratio of the chitosan quaternary ammonium salt-nano antibacterial agent mixture to the folic acid solution is controlled at 1:3. After the addition is complete, stir evenly and let stand for 1 day to allow the reaction to complete, and obtain a viscous aggregate, which is a wet chitosan-based antibacterial wound dressing that can provide long-lasting protection. (4) Take out the viscous aggregate obtained in step (3), make a film with a coating tool, and then place it on a flat dryer to dry at 40°C for 48 hours to obtain a patch with a thickness of 50 μm, which is a dry chitosan-based antibacterial wound dressing that can provide long-lasting protection.

[0046] Comparative Example 1 (1) Disperse 2 g of folic acid in deionized water to prepare a solution with a mass-volume percentage concentration of 0.05% (w / v, i.e., 0.05 g of folic acid in 100 mL of solution). Adjust the pH value to 9.0 using sodium hydroxide solution to obtain a folic acid solution. (2) Add 2 g of chitosan quaternary ammonium salt (molecular weight 15.0 × 10⁻⁶) 4 Da (quaternary ammonium group substitution degree 95%) was dissolved in deionized water to prepare a chitosan quaternary ammonium salt solution with a mass-volume percentage concentration of 1% (w / v, i.e., 1 g chitosan quaternary ammonium salt is contained in 100 mL chitosan quaternary ammonium salt solution). (3) Add the folic acid solution obtained in step (1) dropwise to the chitosan quaternary ammonium salt solution in step (2). The volume ratio of chitosan quaternary ammonium salt solution to folic acid solution is controlled at 1:1. After the addition is complete, stir evenly and let stand for 1 day to allow the reaction to be complete, and obtain a viscous aggregate. (4) Take out the viscous aggregate obtained in step (3), make it into a film with a coating tool, and then place it on a flat dryer to dry at 40°C for 12 hours to obtain a patch with a thickness of 50 μm.

[0047] Comparative Example 2 (1) Disperse 2 g of folic acid in deionized water to prepare a solution with a mass-volume percentage concentration of 2% (w / v, i.e., 2 g of folic acid in 100 mL of solution). Adjust the pH value to 7.2 using sodium hydroxide solution to obtain a folic acid solution. (2) Add 2 g of chitosan quaternary ammonium salt (molecular weight 15.0 × 10⁻⁶) 4 Chitosan (46% quaternary ammonium group substitution) was dissolved in deionized water to prepare a chitosan quaternary ammonium salt solution with a mass-volume percentage concentration of 0.05% (w / v, i.e., 0.05 g of chitosan quaternary ammonium salt in 100 mL of chitosan quaternary ammonium salt solution); nano-antibacterial agents (nano-iron oxide and nano-gold in a mass ratio of 1:3) were dispersed in deionized water to prepare a nano-antibacterial agent dispersion with a mass-volume percentage concentration of 0.1% (w / v, i.e., 0.1 g of nano-antibacterial agent in 100 mL of nano-antibacterial agent dispersion); under stirring, the nano-antibacterial agent dispersion and the chitosan quaternary ammonium salt solution were mixed evenly at a volume ratio of 0.05:10 to obtain a chitosan quaternary ammonium salt-nano-antibacterial agent mixture; (3) Add the folic acid solution obtained in step (1) dropwise to the chitosan quaternary ammonium salt-nano antibacterial agent mixture in step (2). The volume ratio of the chitosan quaternary ammonium salt-nano antibacterial agent mixture to the folic acid solution is controlled at 1:1. After the addition is complete, stir evenly and let stand for 1 day to complete the reaction. A large amount of flocculent product is obtained, which cannot form viscous aggregates and cannot be used to prepare films in the future.

[0048] Comparative Example 3 (1) Disperse 2 g of folic acid in deionized water to prepare a solution with a mass-volume percentage concentration of 2% (w / v, i.e., 2 g of folic acid in 100 mL of solution). Adjust the pH value to 9.0 using sodium hydroxide solution to obtain a folic acid solution. (2) Dissolve 2 g of chitosan in a 2% (w / v) aqueous acetic acid solution to prepare a chitosan solution with a mass-volume percentage concentration of 2% (w / v, i.e., 2 g of chitosan in 100 mL of chitosan solution); (3) Add the folic acid solution obtained in step (1) dropwise to the chitosan mixture in step (2). The volume ratio of chitosan solution to folic acid solution is controlled at 1:1. After the addition is complete, stir evenly and let stand for 1 day to complete the reaction. A large amount of viscous product is obtained, which cannot form viscous aggregates and cannot be used to prepare films.

[0049] Effect verification:

[0050] Figure 1 Morphological diagrams and adhesion test images of the patch prepared in Example 3 are provided. (a), (b), and (c) are photographs of the patch; (d), (e), and (f) show the process of the patch regaining its tack after adding water; and (g), (h), and (i) show the adhesion of the 2.0 cm × 2.0 cm patch to a wetted glass surface and weights. All tests used patch samples of uniform specifications (200 μm thickness). Figure 1 As shown in (a), (b), and (c), the patch exhibits a flexible, thin film texture, easily bent and rolled into an arc shape with tweezers, without cracks or breaks. From Figure 1 As can be seen from (d), (e), and (f), after the patch is soaked in deionized water, it quickly regains its tackiness after absorbing water. From Figure 1 As can be seen from (g), (h) and (i), after the patch is restored to viscosity with water, it can stably support a metal weight of a certain mass without falling off, indicating that the patch has sufficient mechanical strength after being rehydrated.

[0051] Figure 2Macroscopic morphology comparison diagrams of the viscous aggregates obtained in Examples 1-5 and Comparative Example 1, and the products obtained in Comparative Examples 2-3 are shown. From left to right, the viscous aggregates obtained in Examples 1, 2, 3, 4, 5, and Comparative Example 1, and the products obtained in Comparative Examples 2 and 3 are shown. As can be seen from the figures, Comparative Example 2 (pH=7.2) could not form aggregates like the other groups, but instead appeared as a large amount of orange-yellow flocculent matter suspended in the solution; Comparative Example 3 (chitosan group) also could not form aggregates like the other groups, but instead appeared as a large amount of orange-yellow viscous matter. In comparison, the aggregates obtained in Examples 1-5 and Comparative Example 1 all maintained a relatively complete morphology. Among them, the aggregates in Example 3 (nano zinc oxide group), Example 5 (nano iron oxide / gold group), and Comparative Example 1 (without nano antibacterial agent) had the most dense structure, with clear block outlines, and settled to the bottom of the bottle. In Example 1 (nano silver / nano silver oxide / nano copper group) and Example 4 (nano titanium dioxide / nano magnesium oxide group), due to the low molecular weight of chitosan quaternary ammonium salt, the aggregates exhibited a soft blocky shape with a certain degree of fluidity and settled to the bottom of the bottle. In Example 2 (nano copper sulfide / nano copper oxide group), due to the medium molecular weight of chitosan quaternary ammonium salt, the aggregates exhibited a relatively soft blocky shape, with a morphology between fluidity and density, no obvious fluidity, and good structural integrity. In Example 3 (nano zinc oxide group), due to the high molecular weight of chitosan quaternary ammonium salt, the prepared aggregates exhibited a dense putty-like shape, settled to the bottom of the bottle, and did not show natural leveling. The morphology of the aggregates was regulated by the pH value of the folic acid solution, the molecular weight and degree of substitution of the chitosan quaternary ammonium salt, and the synergistic effect of the nano-antibacterial agent. Under alkaline conditions, folic acid is converted into sodium salt, which significantly increases its solubility and can coordinate with the chitosan quaternary ammonium salt to form a stable aggregate structure. Under neutral conditions, folic acid exists in the form of free acid, which has poor solubility and is difficult to complex, thus failing to form a uniform aggregate. Low molecular weight chitosan quaternary ammonium salt gives the aggregates a certain degree of fluidity, while medium molecular weight chitosan quaternary ammonium salt makes them exhibit a soft but non-fluid intermediate state. It can be seen that the high molecular weight and high degree of substitution of the chitosan quaternary ammonium salt significantly improve the compactness and structural stability of the aggregates. The nano-antibacterial agent can make the aggregate structure more compact through hydrogen bonding and coordination with the chitosan quaternary ammonium salt. For example, the structural compactness of Example 3 is better than that of Comparative Example 1 without antibacterial agent, indicating that the introduction of antibacterial agent does not destroy the structural integrity of the aggregates and endows the aggregates with antibacterial effect.

[0052] Figure 3The adhesion and water rinsing resistance of the adhesive aggregates and patches prepared in Examples 4 and 5 on the back of the hand are shown. Adhesive aggregates or patches of the same specifications were applied to the skin of the back of the hand, and continuous water rinsing was applied to evaluate their adhesion and rinsing resistance. As seen in the patch group, the patches of Examples 4 and 5 adhered tightly to the skin on the back of the hand, without lifting, peeling, or curling. After continuous water rinsing, the patches remained intact and adhered to the skin surface without falling off or shifting, with only a small amount of water droplets remaining on the surface, demonstrating excellent skin adhesion and water rinsing resistance. As seen in the adhesive aggregate group, the adhesive aggregates of Examples 4 and 5 adhered tightly to the skin surface on the back of the hand; during water rinsing, the aggregates were not washed away or detached, maintaining an intact adhesive state, demonstrating good rinsing resistance. The viscous agglomerate prepared in Example 4 has better fluidity due to the lower molecular weight of chitosan quaternary ammonium salt, making it easier to apply evenly to the skin surface and more convenient to operate; the viscous agglomerate prepared in Example 5 has a denser structure and better erosion resistance due to the higher molecular weight of chitosan quaternary ammonium salt.

[0053] Figure 4 The degradation of the patches prepared in Example 3 and Comparative Example 1, along with four commercial oral ulcer dressings (Haisihainuo oral ulcer film, compound chlorhexidine dexamethasone patch, dexamethasone acetate patch, and chitosan oral ulcer gel), after immersion in a simulated oral saliva solution for 0–120 min is shown in the figures. The simulated oral saliva solution was prepared under aseptic conditions according to an international standard artificial saliva formula: Na₂HPO₄·2H₂O 0.260 g / L, NaCl 0.700 g / L, KH₂PO₄ 0.200 g / L, NaHCO₃ 1.500 g / L, KCl 1.200 g / L, pH = 6.65 ± 0.01. 2–3 mL of the simulated oral saliva solution was added to each sample group, and the degradation was observed and photographed at 0, 15, 45, 60, 75, 90, 105, and 120 min. In the preferred embodiment, the patch prepared in Example 3 was used to measure its degradation rate in an aqueous or bodily fluid environment (oral simulated fluid). Figure 4As shown in the left figure, the compound chlorhexidine dexamethasone patch exhibited significant swelling and disintegration within 0 min, completely dissolving and spreading throughout the entire system within 15 min, leaving no intact structure. The Haisheng Hainuo oral ulcer film and chitosan oral ulcer gel gradually dissolved and faded within 15–45 min, and by 60 min, no intact sample structure was observed, and no trace of them could be detected. The dexamethasone acetate patch maintained an intact structure at 0 min, but began to swell and disintegrate at the edges between 15 and 60 min, and by 120 min, the edges were completely swollen and whitish, although their presence was still observable. The patch prepared in Comparative Example 1 maintained an intact sheet-like structure within 0–15 min, gradually swelling and lifting at the edges over time, showing significant deformation after 45 min, indicating limited resistance to degradation. The patch prepared in Example 3 showed significant disintegration at 120 min. During the observation period of min, the patch maintained its intact sheet-like structure, exhibiting only slight swelling and edge softening over time, with no obvious disintegration, dissolution, or diffusion. The sample morphology and position remained stable, and its anti-degradation performance was significantly better than Comparative Example 1 and all commercial control groups. The patch prepared in Example 3 showed excellent structural stability in the oral simulation solution. This is because the synergistic cross-linking effect of chitosan quaternary ammonium salt and nano zinc oxide made the aggregate more compact. On the other hand, during the preparation process, the folic acid solution was adjusted to an alkaline environment (pH=10), which allowed the aggregate to form more stable intermolecular interactions after drying into a patch, exhibiting good resistance to dissolution and disintegration in the weakly acidic oral simulation solution. As shown in the right figure, the patch prepared in Example 3 did not degrade in water and had excellent long-term stability. This indicates that the structure of the aggregate remained stable in a neutral aqueous environment, with no hydrolytic breakage of the polymer chains, no mass loss, and no structural collapse. In the oral simulation solution, it showed a slow and continuous degradation trend, achieving complete degradation within one week. This is because the oral simulation solution contains a variety of salt ions, which can cause the internal structure of the aggregate to gradually relax and loosen. In a short period of time, the structure can remain relatively intact and will not disintegrate or degrade rapidly, thus meeting the requirements of long-term retention. As the soaking time is extended, ions continue to penetrate and destroy the original dense network, and the patch gradually degrades. When changing the dressing, it does not need to be removed, thus achieving controlled degradation.

[0054] Figure 5The healing images of full-thickness skin defects in diabetic rats on days 1, 3, 5, 7, 9, 11, and 14 are shown for the control group, the commercial sample group, the patch prepared in Comparative Example 1, and the patch prepared in Example 3. SPF-grade SD rats (6-8 weeks old, weighing approximately 220 grams) were used to establish a diabetic full-thickness skin defect model. The rats were randomly divided into four groups: control group (no treatment), commercial sample group (commercially available 3M transparent dressing), patch prepared in Comparative Example 1, and patch prepared in Example 3, with six rats in each group. Wound photographs were taken on days 1, 3, 5, 7, 9, 10, 11, and 14 post-surgery. The wound healing rate was calculated as follows: Healing rate (%) = (Initial wound area - Current wound area) / Initial wound area × 100%. Day 1: All wounds in each group showed open defects with no obvious healing. Days 3-7: Wounds in all groups gradually healed. The wound area treated with patches prepared in Example 3 and Comparative Example 1 was significantly smaller than that in the blank group and the commercial sample group. The blank group and the commercial sample group still had obvious scabs and swelling, and healing was relatively slow. Day 9: The wound area treated with patches prepared in Example 3 and Comparative Example 1 was significantly smaller than that in the other two groups, and the scabs were reduced. The blank group and the commercial sample group still had large wound areas with obvious scabs and more severe inflammatory reactions. Day 11: The wounds treated with patches prepared in Comparative Example 1 and Example 3 were almost completely closed, with only a very small amount of light pink new epithelium remaining and no obvious scabs. The blank group and the commercial sample group still had obvious scabs and unclosed wounds, and their healing speed was significantly slower. Day 14: The wound in the blank group was not completely closed and there were still obvious bleeding points. In contrast, the wounds in the other groups were basically closed. The wounds treated with patches prepared in Example 3 and Comparative Example 1 were covered with smooth new epithelium. Although the wound in the commercial sample group was completely closed, slight scarring and pigmentation were still visible, and healing was slightly worse. This demonstrates that the addition of nano-antibacterial agent in Example 3 significantly accelerates the healing process of full-thickness skin defects in diabetic rats, exhibiting excellent healing speed as early as day 9 and achieving efficient repair by day 11. Its healing-promoting effect is significantly better than that of the patch treatment group prepared in Comparative Example 1, the commercial sample group, and the blank group. The patch prepared in Example 3 can promote healing due to the synergistic effect of chitosan quaternary ammonium salt and nano-zinc oxide. The quaternary ammonium groups on chitosan quaternary ammonium salt have antibacterial effects; nano-zinc oxide effectively inhibits wound infection and reduces local inflammatory response through synergistic antibacterial effects. The two work synergistically to achieve dual antibacterial and anti-inflammatory effects, enabling the composite patch prepared in Example 3 to accelerate the healing of full-thickness skin defects and the shedding of blood scabs in diabetic rats. Its healing-promoting effect is significantly better than that of Comparative Example 1, the commercial sample group, and the blank group.

[0055] Figure 6The in vitro antibacterial effects of the viscous aggregates prepared in Example 3 (QF / ZnO group), the viscous aggregates prepared in Comparative Example 1 (QF group), and the blank group against Staphylococcus aureus and Pseudomonas aeruginosa are shown in the figures. Staphylococcus aureus (S. aureus ATCC 6538) and Pseudomonas aeruginosa (P. aeruginosa ATCC 9027) were selected as representative Gram-positive and Gram-negative bacteria, respectively, for the in vitro antibacterial test of this invention. The antibacterial activity of the materials in this test was evaluated by plate count method. 2 mg of the viscous aggregate samples prepared in Example 3 and Comparative Example 1 were accurately weighed and added to 0.9 mL of bacterial suspension (10⁶ CFU / mL). -1 The sample was placed in a sterile centrifuge tube and incubated with the bacterial culture at 37°C for 3 hours. After the incubation period, the mixture was serially diluted 10⁻⁶ times. 6 Take 100 μL of the culture medium and inoculate it onto the surface of nutrient agar solid medium. Incubate at 37℃ for 12 hours. Finally, count and photograph the bacterial colonies on the plates. Each experiment was repeated three times, and the average number of colonies was taken to calculate the bacterial survival rate. Figure 6 It can be seen that a large number of dense colonies of Staphylococcus aureus and Pseudomonas aeruginosa appeared on the plates of the blank group, indicating normal bacterial proliferation; the QF group (comparative example 1) had a significant inhibitory effect on Staphylococcus aureus, with no visible colonies on the plate, but it had an inhibitory effect on Pseudomonas aeruginosa, with a small number of colonies remaining on the plate; the QF / ZnO group (Example 3) showed extremely strong antibacterial activity against both strains, with no visible colonies on the plates of either strain, and bacterial proliferation was completely inhibited. The synergistic effect of chitosan quaternary ammonium salt and nano zinc oxide can significantly improve the antibacterial performance of the patch. The adhesive aggregate prepared in Example 3, with its dual antibacterial mechanism, has excellent inhibitory effects on both Gram-positive and Gram-negative bacteria, and its antibacterial performance is significantly better than that of Comparative Example 1, which only contains chitosan quaternary ammonium salt.

[0056] Figure 7 The aggregates prepared in Comparative Example 1 and Example 3 are shown, along with the 4000 to 400 cm⁻¹ values ​​of chitosan quaternary ammonium salt and folic acid. -1 Fourier transform infrared spectra within the range. The figure shows that folic acid is present at 1684 cm⁻¹. -1 An asymmetric C=O stretching vibration absorption peak exists at 1603 cm⁻¹. -1 The peak at 1411 cm⁻¹ is the NH bending vibration peak. -1 Carboxyl COO - Symmetric stretching vibration peak; chitosan quaternary ammonium salt at 1639 cm⁻¹ -1 The characteristic peak of NH bending vibration appears at 1483 cm⁻¹. -1This is the absorption peak of the methyl group in the quaternary ammonium ion. In the condensate prepared in Comparative Example 1, the C=O stretching vibration and NH bending vibration peaks merge with the NH vibration peak of the chitosan quaternary ammonium salt at 1610 cm⁻¹. -1 The broad absorption peak shifts to lower frequencies and becomes broader; in the condensate prepared in Example 3, the C=O stretching vibration, NH bending vibration peaks and the NH vibration peak of chitosan quaternary ammonium salt merge to a peak of 1608 cm⁻¹. -1 A broad absorption peak shifts to lower frequencies and becomes broader. (This refers to the COO of folic acid.) - (1411 cm) -1 The symmetric stretching vibration peak has redshifted to 1406 cm⁻¹. -1 (Comparative Example 1) 1407 cm -1 (Example 3). The condensates prepared in Example 3 and Comparative Example 1 were at 1512 cm⁻¹. -1 The absorption peak at [location] is the stretching vibration peak of the C=C skeleton of folic acid aromatic ring. Its slight shift and broadening under hydrogen bonding indicates that folic acid has been successfully incorporated into the condensate. Simultaneously, chitosan quaternary ammonium salt and folic acid are combined through electrostatic interactions and intermolecular hydrogen bonds. Notably, no other new peaks appeared in the condensates prepared in Comparative Example 1 and Example 3, proving that their internal network is formed by physical interactions.

[0057] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A chitosan-based antibacterial wound dressing with long-lasting protective properties, characterized in that: This antibacterial wound dressing is made from chitosan quaternary ammonium salt, folic acid, and nano-antibacterial agents.

2. The chitosan-based antibacterial wound dressing with long-lasting protection according to claim 1, characterized in that: The degree of quaternary ammonium group substitution of the chitosan quaternary ammonium salt is 30-99.8%, and the molecular weight of the chitosan quaternary ammonium salt is 1.0 × 10⁻⁶. 4 -20×10 4 Da; The nano antibacterial agent is one or more of nano zinc oxide, nano silver, nano silver oxide, nano copper, nano copper sulfide, nano copper oxide, nano titanium dioxide, nano magnesium oxide, nano iron oxide, and nano gold.

3. The method for preparing a long-lasting protective chitosan-based antibacterial wound dressing according to claim 1, characterized in that... Follow these steps: (1) Disperse folic acid in deionized water and adjust the pH value with sodium hydroxide solution to obtain folic acid solution; (2) Chitosan quaternary ammonium salt is dissolved in deionized water to obtain chitosan quaternary ammonium salt solution, and nano antibacterial agent is dispersed in deionized water to obtain nano antibacterial agent dispersion. Under stirring, chitosan quaternary ammonium salt solution and nano antibacterial agent dispersion are mixed evenly, and ultrasonic treatment is performed to obtain chitosan quaternary ammonium salt-nano antibacterial agent mixture. (3) Add the folic acid solution obtained in step (1) dropwise to the chitosan quaternary ammonium salt-nano antibacterial agent mixture obtained in step (2). After the addition is complete, stir evenly and let stand to allow the reaction to be complete, and obtain a viscous aggregate, which is a wet chitosan-based antibacterial wound dressing that can provide long-lasting protection. (4) Take the viscous aggregate obtained in step (3) and make it into a uniform film using a coating tool; then place it on a flat dryer to dry it to obtain a patch, which is a dry chitosan-based antibacterial wound dressing that can provide long-lasting protection.

4. The method for preparing a long-lasting protective chitosan-based antibacterial wound dressing according to claim 3, characterized in that: The folic acid solution in step (1) has a mass-volume percentage concentration of 0.05%-4%; the pH value is 9.0-12.

0.

5. The method for preparing a long-lasting protective chitosan-based antibacterial wound dressing according to claim 3, characterized in that: The chitosan quaternary ammonium salt solution in step (2) has a mass-volume percentage concentration of 0.05%-4%; the nano antibacterial agent dispersion has a mass-volume percentage concentration of 0.05%-2%; and the nano antibacterial agent dispersion and the chitosan quaternary ammonium salt solution are mixed at a volume ratio of 0.05:10 to 1:

10.

6. The method for preparing a long-lasting protective chitosan-based antibacterial wound dressing according to claim 3, characterized in that: The ultrasonic power in step (2) is 200W-600W, the ultrasonic temperature is 25℃-40℃, and the ultrasonic time is 0-180 minutes.

7. The method for preparing a long-lasting protective chitosan-based antibacterial wound dressing according to claim 3, characterized in that: In step (3), the chitosan quaternary ammonium salt-nano antibacterial agent mixture and folic acid solution are mixed at a volume ratio of 1:0.5-1:5; the standing time is 15 minutes to 3 days.

8. The method for preparing a long-lasting protective chitosan-based antibacterial wound dressing according to claim 3, characterized in that: The thickness of the patch in step (4) is 20μm-400μm; the drying temperature is 40℃-50℃ and the drying time is 8-72 hours.

9. The application of the chitosan-based antibacterial wound dressing with long-lasting protection according to claim 1 in the preparation of oral ulcer patches and wound repair dressings.

10. The application of the chitosan-based antibacterial wound dressing with long-lasting protection according to claim 1 in the preparation of drug delivery systems, acne treatment drugs, or cosmetic adhesives.

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