Antibacterial dressing for diabetic foot ulcer

Abstract

The invention discloses an antibacterial dressing for diabetic foot ulcer, and belongs to the technical field of antibacterial materials, hydrogel with excellent mechanical properties is obtained by adopting dynamic covalent bonds and supramolecular action, the hydrogel has the functions of resisting bacteria, eliminating excessive ROS (reactive oxygen species) and repairing wounds, and the hydrogel has a good antibacterial effect through photo-thermal and polylysine synergistic bacteria resistance. The slow-release phenolic hydroxyl group and copper ions respectively play roles in eliminating ROS and repairing wounds.

Description

Technical Field

[0001] This invention belongs to the field of antibacterial materials technology, specifically relating to an antibacterial dressing for diabetic foot ulcers. Background Technology

[0002] With the increasing incidence of diabetes, the incidence of diabetic foot ulcers is also rising. Because diabetic foot ulcers have impaired healing ability and are often accompanied by infection, they frequently develop into chronic wounds, making diabetic wounds a unique type of chronic wound in diabetic patients. Wound healing is a dynamic and complex biological process, which can be divided into four overlapping stages: hemostasis, inflammation, proliferation, and remodeling. Diabetic patients are affected by factors such as hyperglycemia caused by the systemic effects of diabetes, unbalanced inflammatory responses, oxidative stress damage, tissue hypoxia due to lack of angiogenesis at the wound site, and an extremely high risk of bacterial infection. These factors disrupt and impair the sequence of each stage in the original acute wound healing process, leading to the transformation of acute wounds into chronic wounds.

[0003] Hydrogels, due to their high water content, can mimic the composition and mechanical properties of the extracellular matrix, providing a favorable microenvironment for cell migration and tissue regeneration. Simultaneously, the three-dimensional network structure of the gel endows it with excellent gas exchange properties and efficient absorption of tissue exudates, which is beneficial for promoting wound healing. Currently, the main methods for antibacterial hydrogel dressings involve loading antibiotics, inorganic nanoparticles, and natural antibacterial agents, as well as introducing antibacterial components (such as photothermal or photodynamic responsive compounds and inherent antibacterial cationic polymers) into the hydrogel network through physical encapsulation. However, this approach has the following problems: 1. The widespread use of antibiotics has led to the emergence of superbugs with antimicrobial resistance; 2. Metal nanoparticles have certain toxic side effects; 3. Photodynamic therapy generates excessive reactive oxygen species (ROS), inhibiting cell migration and delaying wound healing; 4. Photosensitizers obtained through physical encapsulation are prone to inactivation or the antibacterial components are released too quickly. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides an antibacterial dressing for diabetic foot ulcers. It uses dynamic covalent bonds and supramolecular interactions to obtain a hydrogel with excellent mechanical properties, which has antibacterial, ROS elimination and wound repair functions. Through photothermal and polylysine synergistic antibacterial action, the slow-released phenolic hydroxyl groups and copper ions play the roles of eliminating ROS and repairing wounds, respectively.

[0005] The technical solution to achieve the objective of this invention is as follows: an antibacterial dressing, the preparation method of which is as follows:

[0006] S1. Reaction of antibacterial polyphenols with polylysine to obtain antibacterial polyphenol-modified polylysine, followed by dissolution in water to obtain its aqueous solution;

[0007] S2. After modifying polyethylene glycol to obtain aldehyde-containing polyethylene glycol, it is dissolved in water to obtain its aqueous solution;

[0008] S3. Disperse copper ions in the aqueous solution obtained in step S2, then disperse photosensitizer in the aqueous solution obtained in step S1, mix the two and vortex to obtain antibacterial dressing;

[0009] The photosensitizer has the following chemical structure: Formula I:

[0010] In Formula I, R1 and R2 are hydroxyl groups, and R3 is one or more of hydroxyl, hydrogen, methyl, ethyl and methoxy groups.

[0011] Preferably, the antibacterial polyphenol in step S1 is one or more of 3,4,5-trihydroxybenzaldehyde, gallic acid, protocatechuic acid, and 3,4-dihydroxybenzaldehyde.

[0012] More preferably, the antibacterial polyphenol in step S1 is gallic acid.

[0013] Preferably, the molecular weight of the polylysine in step S1 is Mn = 3000-6000 Da; the copper ions in step S2 are obtained by dissolving copper chloride in water.

[0014] Preferably, the aldehyde-containing polyethylene glycol described in step S2 has the following chemical structure:

[0015] In Formula II, R1, R2, R3, R4, R5 and R6 are independently one or more of aldehyde, hydrogen, methyl, ethyl and methoxy groups, at least one of R1, R2 and R3 is an aldehyde group, at least one of R4, R5 and R6 is an aldehyde group, and m is 20 to 50.

[0016] Preferably, the mass concentration of polylysine in step S1 is 0.04–0.06 g / mL; the mass concentration of aldehyde-containing polyethylene glycol in step S2 is 0.04–0.06 g / mL; the mass concentration of copper ions after mixing in step S3 is 200–300 μg / mL; the mass concentration of photosensitizer after mixing is 60–100 μg / mL; and the volume ratio of the two in step S3 is 1:1.

[0017] Preferably, the method for preparing the antibacterial polyphenol-modified polylysine in step S1 is as follows:

[0018] Under an inert atmosphere and ice bath conditions, polylysine was dissolved in MES buffer. Then, under ice bath conditions, 1 eq of gallic acid, 1.2–1.5 eq of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 1.0–1.2 eq of N-hydroxysuccinimide were dissolved in DMF and stirred for 20–40 min. The solution was then added dropwise to the polylysine solution, and stirring continued for another 20–40 min under ice bath conditions. Stirring continued at 30–40 °C for 20–24 h. The resulting solution was dialyzed against deionized water for 2–3 days and freeze-dried to obtain antibacterial polyphenol-modified polylysine. The mass ratio of polylysine to gallic acid was 1:(2–3).

[0019] Preferably, the preparation method of the aldehyde-containing polyethylene glycol in step S2 is as follows:

[0020] Under an inert atmosphere and ice bath conditions, 2–3 eq of p-aldehyde benzoic acid, 1 eq of polyethylene glycol, 3–4 eq of N,N'-dicyclohexylcarbodiimide, and 0.2–0.3 eq of 4-dimethylaminopyridine were dissolved in anhydrous dichloromethane. The mixture was stirred at room temperature for 2–3 days, and the solid was removed by filtration. Diethyl ether was added to the resulting solution to precipitate the solid. The solid was dialyzed against deionized water for 2–3 days and then freeze-dried to obtain aldehyde-containing polyethylene glycol.

[0021] Preferably, the photosensitizer has the following chemical structure: Formula III

[0022]

[0023] Specifically, the preparation method of the chemical structure of Formula III is as follows:

[0024] (1) Dissolve 1 eq of p-nitrobenzaldehyde and 2-3 eq of 2,4-dimethylpyrrole in chloroform, add 0.5-1 w.t% of trifluoroacetic acid (total amount of system) dropwise, stir at room temperature for 12-14 h, dissolve 1-1.2 eq of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in chloroform and add it to the mixture, heat to 45-50 °C and continue stirring for 20-30 min, wash the resulting solution with water at least twice, concentrate the organic phase, and purify by column chromatography to obtain compound one;

[0025] (2) Add 1 eq of compound one to a reaction vessel, then add a mixed solution of ethanol and water, heat to 45-55°C, add 6-8 eq of iron powder and 20-30 eq of acetic acid, heat to 60-70°C and stir for 2-3 hours, cool to room temperature, filter, remove most of the ethanol by rotary evaporation, extract with chloroform, wash the obtained chloroform with ammonia water 1-2 times, dry the filtrate with anhydrous magnesium sulfate, filter to remove the solvent, and obtain compound two;

[0026] (3) Dissolve 1 eq of compound II in chloroform, add 1.5 eq of triethylamine and stir for 20-30 min, then add 2.0 eq of boron trifluoride diethyl ether complex, stir at 45-50 °C for 2-3 h, add dichloromethane to dilute the mixture, wash at least twice with saturated sodium carbonate solution, collect the organic phase, dry with anhydrous magnesium sulfate and filter, remove excess tetrahydrofuran and ethyl acetate by rotary evaporation, and purify by column chromatography to obtain compound III;

[0027] (4) Under an inert atmosphere, 1–1.5 eq of gallic acid was dissolved in chloroform, 1–2 eq of N,N-diisopropylethylamine and 1–2 eq of HATU were added and stirred, 1 eq of compound three was dissolved in chloroform and slowly added dropwise to the mixture, and stirred for 20–36 h. The solid was removed by filtration, and the organic phase was washed at least twice with 1–2 mol / L hydrochloric acid aqueous solution and saturated sodium bicarbonate aqueous solution. The organic phase was collected, the solvent was removed, and compound four was obtained.

[0028] (5) Under an inert atmosphere, compound 4 was added to the reaction vessel and dissolved in anhydrous acetonitrile. Then, 3-4 eq of p-dimethylaminobenzaldehyde was added, followed by 5-6 eq of acetic acid and 5-6 eq of pyridine. The mixture was heated to 85-95°C and stirred for 2-3 hours. The solvent was evaporated and purified by column chromatography to obtain the chemical structure of formula III.

[0029] This application also preserves the application of the above-mentioned antibacterial dressing in the treatment of diabetic foot ulcers.

[0030] Beneficial effects

[0031] This invention offers the following advantages: It utilizes dynamic covalent bonds and supramolecular interactions to obtain a hydrogel with excellent mechanical properties, possessing antibacterial, ROS elimination, and wound repair functions. Through photothermal interaction and the synergistic antibacterial effect of polylysine, the slowly released phenolic hydroxyl groups and copper ions respectively eliminate ROS and repair wounds. Specifically, the copper ions work by: initially crosslinking the antibacterial polyphenol-modified polylysine via coordination bonds, reducing gel formation time; then coordinating with a photosensitizer to improve its photothermal efficiency and stability; and after a certain period, the slowly released copper ions promote wound repair while simultaneously accelerating gel degradation. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the synthesis steps and crosslinking mechanism of the antibacterial dressing of this application;

[0033] Figure 2 This is a schematic diagram of the photosensitizer synthesis steps in this application;

[0034] Figure 3 This is the 1H NMR spectrum of photosensitizer 1 in deuterated DMSO. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0037] The raw materials and equipment used in the embodiments and comparative examples are described below:

[0038] Polylysine: L-lysine polymer, Mw=5000, purchased from Leyan;

[0039] Gallic acid: purchased from Shanghai Maclean's;

[0040] Copper chloride: purchased from Shanghai Maclean;

[0041] Polyethylene glycol: Mw=2000, purchased from Tianjin Xiens Biochemical;

[0042] p-Aldehydebenzoic acid: purchased from Shanghai Maclean;

[0043] MES buffer: pH 6.5, purchased from Shanghai Maclean's.

[0044] p-Nitrobenzaldehyde: purchased from Shanghai Maclean;

[0045] 2,4-Dimethylpyrrole: purchased from Shanghai Maclean;

[0046] p-Dimethylaminobenzaldehyde: purchased from Shanghai Maclean.

[0047] Photosensitizer 1

[0048] (1) Dissolve 1 eq of p-nitrobenzaldehyde and 3 eq of 2,4-dimethylpyrrole in chloroform, add 0.8 wt% of trifluoroacetic acid of the total system volume dropwise, stir at room temperature for 12 h, dissolve 1.2 eq of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in chloroform and add it to the mixture, heat to 50 °C and continue stirring for 30 min, wash the resulting solution with water 3 times, concentrate the organic phase, and purify by column chromatography to obtain compound one;

[0049] (2) 1 eq of compound one was added to the reaction vessel, followed by a mixed solution of ethanol and water. The mixture was heated to 50°C, 7 eq of iron powder and 25 eq of acetic acid were added, and the mixture was heated to 65°C and stirred for 3 hours. The mixture was cooled to room temperature and filtered. Most of the ethanol in the resulting liquid was removed by rotary evaporation. The liquid was extracted with chloroform and washed twice with ammonia. The filtrate was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed to obtain compound two.

[0050] (3) Dissolve 1 eq of compound II in chloroform, add 1.5 eq of triethylamine and stir for 30 min, then add 2.0 eq of boron trifluoride diethyl ether complex, stir at 50 °C for 3 h, add dichloromethane to dilute the mixture, wash 3 times with saturated sodium carbonate solution, collect the organic phase, dry with anhydrous magnesium sulfate and filter, remove excess tetrahydrofuran and ethyl acetate by rotary evaporation, and purify by column chromatography to obtain compound III;

[0051] (4) Under a nitrogen atmosphere, 1.2 eq of gallic acid was dissolved in chloroform, 1.5 eq of N,N-diisopropylethylamine and 1.3 eq of HATU were added and stirred. 1 eq of compound three was dissolved in chloroform and slowly added dropwise to the mixture. After stirring for 36 h, the solid was removed by filtration. The organic phase was washed twice with 1 mol / L hydrochloric acid aqueous solution and saturated sodium bicarbonate aqueous solution. The organic phase was collected and the solvent was removed to obtain compound four.

[0052] (5) Under a nitrogen atmosphere, compound 4 was added to the reaction vessel and dissolved in anhydrous acetonitrile. Then, 3 eq of p-dimethylaminobenzaldehyde was added, followed by 5 eq of acetic acid and 5 eq of pyridine. The mixture was heated to 90°C and stirred for 3 h. The solvent was evaporated and purified by column chromatography to obtain photosensitizer 1.

[0053] Photosensitizer 2

[0054] Compared with the preparation method of photosensitizer 1, the difference is that gallic acid is replaced with benzoic acid in step (4).

[0055] The following are the test methods for performance parameters involved in this invention:

[0056] Gel formation time test: Record the time when the hydrogel solution no longer flows after mixing in step S3 of the antibacterial dressing preparation method.

[0057] Photothermal performance testing: After preparing hydrogels from the examples and comparative examples, 1 mL was placed in a cuvette and tested under an 808 nm near-infrared laser (power density 1 W / cm²). -2 Irradiate for 5 minutes and record the temperature.

[0058] Copper ion release test: 100 mg of hydrogel was dispersed in 100 mL of phosphate buffer at pH 6.5. 1 mL of the release solution was taken at predetermined time points, and 1 mL of phosphate buffer was added at the same time to maintain a constant system volume. The copper ion release rate was monitored by ICP-MS, and the time required for the release of 20%, 40%, 60%, and 70% of copper ions was recorded.

[0059] Antioxidant Assay: The free radical scavenging ability of the hydrogel was evaluated using a DPPH free radical scavenging assay. A 0.1 mmol / L DPPH solution was prepared with ethanol, and 1 mL of DPPH solution was added to 200 μL of gel. The gel was then incubated in the dark at 37°C for 5 min. The absorbance of each sample at 525 nm was then measured using a UV spectrophotometer. The scavenging rate was calculated using the following formula:

[0060] Clearance rate (%) = (A0 - A i / A0)×100%; where A0 is the initial absorbance of the DPPH solution, A i The absorbance of the hydrogel after DPPH removal.

[0061] Hydrogel antibacterial rate determination: Add 300 μL of gel precursor solution to a 24-well plate, and add 300 μL of bacterial suspension (10... 7 CFU / mL), incubated at 37℃ for 6 h. 50 μL of the diluted solution was spread onto 60 mm diameter LB solid agar plates, divided into laser-irradiated and dark control groups. After 24 h of incubation at 37℃, the colonies were photographed and counted. A control group without any gel was used. The antibacterial rate was calculated using the following formula:

[0062]

[0063] In the formula: E anti For antibacterial rate; N c The colony count for the control group; N e The colony counts are for the examples and comparative tests.

[0064] Example 1

[0065] A method for preparing an antibacterial dressing is as follows:

[0066] S1. Under a nitrogen atmosphere and ice bath conditions, polylysine was dissolved in MES buffer. Under ice bath conditions, 1 eq of gallic acid, 1.3 eq of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1.2 eq of N-hydroxysuccinimide were dissolved in DMF and stirred for 30 min. The solution was then added dropwise to the polylysine solution. Stirring was continued for another 30 min under ice bath conditions, followed by stirring at 40 °C for 24 h. The resulting solution was dialyzed against deionized water for 2–3 days and freeze-dried to obtain antibacterial polyphenol-modified polylysine (where the mass ratio of polylysine to gallic acid was 1:2.5). This polylysine was then dissolved in water to prepare an aqueous solution with a mass concentration of 5 wt.%.

[0067] S2. Under a nitrogen atmosphere and in an ice bath, 2.5 eq of p-aldehyde benzoic acid, 1 eq of polyethylene glycol, 3 eq of N,N'-dicyclohexylcarbodiimide, and 0.3 eq of 4-dimethylaminopyridine were dissolved in anhydrous dichloromethane. The mixture was stirred at room temperature for 3 days, and the solid was removed by filtration. Diethyl ether was added to the resulting solution to precipitate the solid. The solid was dialyzed against deionized water for 3 days and freeze-dried to obtain aldehyde-containing polyethylene glycol. This was then dissolved in water to prepare an aqueous solution with a mass concentration of 5 wt.%.

[0068] S3. Disperse 2000 μg of copper chloride in 5 mL of the aqueous solution obtained in step S2, then disperse 600 μg of photosensitizer 1 in the aqueous solution obtained in step S1. Mix the two and vortex to obtain the antibacterial dressing.

[0069] Example 2

[0070] Compared with the preparation method of Example 1, the difference is that 600 μg of photosensitizer 1 in step S3 is replaced with 800 μg of photosensitizer 1.

[0071] Example 3

[0072] Compared with the preparation method of Example 1, the difference is that 600 μg of photosensitizer 1 in step S3 is replaced with 1000 μg of photosensitizer 1.

[0073] Example 4

[0074] Compared with the preparation method of Example 1, the difference is that the 2000 μg of copper chloride in step S3 is replaced with 2500 μg of copper chloride.

[0075] Example 5

[0076] Compared with the preparation method of Example 1, the difference is that the 2000 μg of copper chloride in step S3 is replaced with 3000 μg of copper chloride.

[0077] Comparative Example 1

[0078] The difference between this preparation method and that of Example 1 is that copper chloride is not added in step S3.

[0079] Comparative Example 2

[0080] The difference between this preparation method and that of Example 1 is that photosensitizer 1 is not added in step S3.

[0081] Comparative Example 3

[0082] Compared with the preparation method of Example 1, the difference is that 600 μg of photosensitizer 1 in step S3 is replaced with 600 μg of photosensitizer 2.

[0083] Comparative Example 4

[0084] Compared with the preparation method in Example 1, the difference is that in step S1, the polylysine is not modified by antibacterial polyphenols, that is, the resulting solution is an aqueous solution of polylysine.

[0085] Table 1 Performance characterization of examples and comparative examples

[0086]

[0087] As can be seen from the data in Table 1, the antibacterial dressing of this application has a fast gelation time (95-115s), excellent photothermal properties, good antioxidant and antibacterial properties, and a long sustained release time of copper ions when simulating a wound environment.

[0088] As shown in Table 1, the photothermal performance data shows that in Examples 1-3, the photothermal effect of the antibacterial dressing gradually increases with the increase of the content of photosensitizer 1. As shown in Comparative Example 1, the photothermal performance decreases slightly without the addition of copper ions, indicating that copper ions enhance the photothermal effect of the photosensitizer. As shown in Comparative Example 2, the photothermal performance decreases significantly without the addition of photosensitizer. As shown in the data of Comparative Example 3, the photothermal efficiency of the light-emitting agent 2 is relatively low because it lacks a hydroxyl structure that coordinates with copper ions.

[0089] As shown in Table 1, the gelation time data indicates that in Examples 1, 4, and 5, the gelation time is shortened as the copper ion content increases within a certain range. As shown in Comparative Examples 1 and 4, the gelation time increases without the addition of copper chloride or polylysine or without modification by antibacterial polyphenols.

[0090] As can be seen from the antioxidant data of Comparative Example 1 in Table 1, the antioxidant capacity is relatively weak when polylysine is added alone.

[0091] As can be seen from the copper ion release data of Comparative Example 4 in Table 1, the addition of polylysine alone cannot coordinate well with copper ions, resulting in an excessively fast copper ion release rate. As can be seen from the data of Examples 1, 4 and 5, the release rate will accelerate with the increase of copper ion content. This is because too many copper ions may not be able to coordinate effectively with hydroxyl groups, resulting in a faster release time.

[0092] As can be seen from the antibacterial rate data of Examples 1 to 5 in Table 1 under darkness and laser irradiation, laser irradiation can kill bacteria more efficiently.

[0093] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An antibacterial dressing, characterized in that, The method for preparing the antibacterial dressing is as follows: S1. Reaction of antibacterial polyphenols with polylysine to obtain antibacterial polyphenol-modified polylysine, followed by dissolution in water to obtain its aqueous solution; S2. After modifying polyethylene glycol to obtain aldehyde-containing polyethylene glycol, it is dissolved in water to obtain its aqueous solution; S3. Disperse copper ions in the aqueous solution obtained in step S2, then disperse photosensitizer in the aqueous solution obtained in step S1, mix the two and vortex to obtain antibacterial dressing; The photosensitizer has the following chemical structure: Formula I: In Formula I, R1 and R2 are hydroxyl groups, and R3 is one or more of hydroxyl, hydrogen, methyl, ethyl and methoxy groups.

2. The antibacterial dressing as described in claim 1, characterized in that, The antibacterial polyphenols mentioned in step S1 are one or more of 3,4,5-trihydroxybenzaldehyde, gallic acid, protocatechuic acid, and 3,4-dihydroxybenzaldehyde.

3. The antibacterial dressing as described in claim 1, characterized in that, The antibacterial polyphenol mentioned in step S1 is gallic acid.

4. The antibacterial dressing as described in claim 1, characterized in that, The molecular weight of the polylysine in step S1 is Mn = 3000-6000 Da; the copper ions in step S2 are obtained by dissolving copper chloride in water.

5. The antibacterial dressing as described in claim 1, characterized in that, The aldehyde-containing polyethylene glycol described in step S2 has the following chemical structure: In Formula II, R1, R2, R3, R4, R5 and R6 are independently one or more of aldehyde, hydrogen, methyl, ethyl and methoxy groups, at least one of R1, R2 and R3 is an aldehyde group, at least one of R4, R5 and R6 is an aldehyde group, and m is 20 to 50.

6. The antibacterial dressing as described in claim 1, characterized in that, The mass concentration of polylysine in step S1 is 0.04–0.06 g / mL; the mass concentration of aldehyde-containing polyethylene glycol in step S2 is 0.04–0.06 g / mL; the mass concentration of copper ions after mixing in step S3 is 200–300 μg / mL, and the mass concentration of photosensitizer after mixing is 60–100 μg / mL; the volume ratio of the two in step S3 is 1:

1.

7. The antibacterial dressing as described in claim 1, characterized in that, The preparation method of the antibacterial polyphenol-modified polylysine described in step S1 is as follows: Under an inert atmosphere and ice bath conditions, polylysine was dissolved in MES buffer. Then, under ice bath conditions, 1 eq of gallic acid, 1.2–1.5 eq of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 1.0–1.2 eq of N-hydroxysuccinimide were dissolved in DMF and stirred for 20–40 min. The solution was then added dropwise to the polylysine solution, and stirring continued for another 20–40 min under ice bath conditions. Stirring continued at 30–40 °C for 20–24 h. The resulting solution was dialyzed against deionized water for 2–3 days and freeze-dried to obtain antibacterial polyphenol-modified polylysine. The mass ratio of polylysine to gallic acid was 1:(2–3).

8. The antibacterial dressing as described in claim 1, characterized in that, The preparation method of the aldehyde-containing polyethylene glycol in step S2 is as follows: Under an inert atmosphere and ice bath conditions, 2–3 eq of p-aldehyde benzoic acid, 1 eq of polyethylene glycol, 3–4 eq of N,N'-dicyclohexylcarbodiimide, and 0.2–0.3 eq of 4-dimethylaminopyridine were dissolved in anhydrous dichloromethane. The mixture was stirred at room temperature for 2–3 days, and the solid was removed by filtration. Diethyl ether was added to the resulting solution to precipitate the solid. The solid was dialyzed against deionized water for 2–3 days and then freeze-dried to obtain aldehyde-containing polyethylene glycol.

9. The antibacterial dressing as described in claim 1, characterized in that, The photosensitizer has the following chemical structure, Formula III: The preparation method of the chemical structure of Formula III is as follows: (1) Dissolve 1 eq of p-nitrobenzaldehyde and 2-3 eq of 2,4-dimethylpyrrole in chloroform, add 0.5-1 w.t% of trifluoroacetic acid (total amount of system) dropwise, stir at room temperature for 12-14 h, dissolve 1-1.2 eq of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in chloroform and add it to the mixture, heat to 45-50 °C and continue stirring for 20-30 min, wash the resulting solution with water at least twice, concentrate the organic phase, and purify by column chromatography to obtain compound one; (2) Add 1 eq of compound one to a reaction vessel, then add a mixed solution of ethanol and water, heat to 45-55°C, add 6-8 eq of iron powder and 20-30 eq of acetic acid, heat to 60-70°C and stir for 2-3 hours, cool to room temperature, filter, remove most of the ethanol by rotary evaporation, extract with chloroform, wash the obtained chloroform with ammonia water 1-2 times, dry the filtrate with anhydrous magnesium sulfate, filter to remove the solvent, and obtain compound two; (3) Dissolve 1 eq of compound II in chloroform, add 1.5 eq of triethylamine and stir for 20-30 min, then add 2.0 eq of boron trifluoride diethyl ether complex, stir at 45-50 °C for 2-3 h, add dichloromethane to dilute the mixture, wash at least twice with saturated sodium carbonate solution, collect the organic phase, dry with anhydrous magnesium sulfate and filter, remove excess tetrahydrofuran and ethyl acetate by rotary evaporation, and purify by column chromatography to obtain compound III; (4) Under an inert atmosphere, 1–1.5 eq of gallic acid was dissolved in chloroform, 1–2 eq of N,N-diisopropylethylamine and 1–2 eq of HATU were added and stirred, 1 eq of compound three was dissolved in chloroform and slowly added dropwise to the mixture, and stirred for 20–36 h. The solid was removed by filtration, and the organic phase was washed at least twice with 1–2 mol / L hydrochloric acid aqueous solution and saturated sodium bicarbonate aqueous solution. The organic phase was collected, the solvent was removed, and compound four was obtained. (5) Under an inert atmosphere, compound 4 was added to the reaction vessel and dissolved in anhydrous acetonitrile. Then, 3-4 eq of p-dimethylaminobenzaldehyde was added, followed by 5-6 eq of acetic acid and 5-6 eq of pyridine. The mixture was heated to 85-95°C and stirred for 2-3 hours. The solvent was evaporated and purified by column chromatography to obtain the chemical structure of formula III.

10. The use of the antibacterial dressing as described in any one of claims 1 to 9 in the treatment of diabetic foot ulcers.

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