Preparation method of antibacterial surface modified polyurethane foam dressing

Abstract

The invention relates to a preparation method of an antibacterial surface-modified polyurethane foam dressing, which comprises the following steps: firstly, preparing a polyurethane foam base material with an open pore structure through a reaction of polyol and isocyanate; then, the foam surface is subjected to plasma treatment or chemical oxidation and other pretreatment modes to activate the surface; then, grafting silane or macromolecular chain segments containing antibacterial groups on the surface of the foam; antibacterial agents such as nano-silver, quaternary ammonium salt or chitosan are further loaded; and finally, washing and drying to obtain the finished dressing. The method is simple and convenient to operate, the antibacterial property of the polyurethane foam can be effectively improved, the good liquid absorption property and softness of the polyurethane foam are kept, and the method is suitable for preparing dressings for chronic wounds, surgical postoperative wounds and infectious wounds.

Description

Technical Field

[0001] The present application relates to the technical field of medical polymer materials, and in particular to a method for preparing an antibacterial surface-modified polyurethane foam dressing. Background Art

[0002] With the continuous advancement of medical technology and the increasing trend of an aging population, the number of patients with chronic wounds (such as bedsores, diabetic foot, venous ulcers, etc.) has increased year by year, and the demand for high-performance medical dressings has also been growing. Polyurethane foam has been widely used in the field of wound care due to its good biocompatibility, excellent liquid absorption and soft physical properties, and has become one of the important base materials for modern medical dressings. However, traditional polyurethane foam dressings are susceptible to infection by pathogenic microorganisms during use, especially in moist environments, where they can become a breeding ground for bacteria and fungi. This increases the risk of wound infection, delays wound healing, and can even lead to serious complications. Therefore, imparting antimicrobial properties to polyurethane foam dressings has become a hot topic and a key area of ​​research in medical dressings.

[0003] Currently, studies have attempted to improve the antimicrobial properties of polyurethane foam by modifying it with methods such as doping with nanosilver, antibiotics, or grafting antimicrobial polymers. However, the following issues remain: first, antimicrobial agents are prone to migration or inactivation, resulting in a short-lasting antimicrobial effect; second, some antimicrobial agents, such as antibiotics, may lead to the emergence of drug-resistant strains; and third, the modification process is complex, making it difficult to balance stability and biosafety. Therefore, a simple, long-lasting, stable, and biocompatible antimicrobial surface modification method is urgently needed to enhance the overall performance of polyurethane foam dressings. Summary of the Invention

[0004] In order to improve the technical disadvantage of polyurethane foam dressings having an insufficiently long-lasting antibacterial effect, the present application provides a method for preparing a polyurethane foam dressing with an antibacterial surface modification.

[0005] The present application provides a method for preparing an antibacterial surface-modified polyurethane foam dressing using the following technical solution: A method for preparing an antibacterial surface-modified polyurethane foam dressing, comprising the following steps: (1) Preparation of polyurethane foam substrate: polyol and isocyanate are reacted to form a foam to obtain a polyurethane foam with an open cell structure; (2) Surface pretreatment: Activate the polyurethane foam surface by plasma treatment, ozone oxidation or alkali treatment; (3) Grafting modification: Grafting polymer segments with antibacterial groups or silane reagents containing functional groups onto the activated surface; (4) Antimicrobial loading: loading nanosilver, quaternary ammonium salt or chitosan antimicrobial agents on the modified surface; (5) Post-treatment and drying: The unreacted residues are removed by water washing, and then the polyurethane foam dressing with antibacterial surface modification is obtained by low-temperature drying and molding.

[0006] By adopting the above technical scheme, the antibacterial surface modification function of the polyurethane foam dressing is effectively realized. By controlling the foaming reaction of polyol and isocyanate, an open-pore structure foam material with good liquid absorption and air permeability is obtained, providing an ideal substrate basis for subsequent modification. Subsequently, the foam surface is activated by plasma, ozone oxidation or alkali treatment, effectively introducing polar functional groups, and significantly improving the surface grafting efficiency of functional reagents. In the grafting modification step, polymer segments or silane reagents with antibacterial groups are introduced, which not only enhances the foam surface's loading capacity for antibacterial agents, but also provides chemical binding sites for constructing a stable and long-lasting antibacterial layer. The modified surface is loaded with nanosilver, quaternary ammonium salts or chitosan antibacterial agents to achieve broad-spectrum and efficient inhibition of multiple pathogenic microorganisms, thereby enhancing the anti-infection performance of the dressing in actual clinical applications. The unreacted components are removed by water washing and low-temperature drying to ensure the dressing structure is stable and the function is long-lasting.

[0007] Optionally, the polyol in step (1) is a polyether polyol or a polyester polyol, and the isocyanate is toluene diisocyanate (TDI) or isophorone diisocyanate (IPDI).

[0008] By adopting the above technical solution, polyether polyols or polyester polyols are selected to react with TDI or IPDI to achieve precise control of the structure and properties of polyurethane foam materials, giving the foam good elasticity, mechanical strength and liquid absorption. The combination of different types of polyols and isocyanates helps to optimize the open pore structure of the foam, providing a stable carrier for subsequent surface modification and antibacterial agent loading, improving the overall mechanical properties and application adaptability of the dressing, and thus enhancing its actual use effect in wound management.

[0009] Optionally, the surface activation method in step (2) is low-temperature plasma treatment, with a treatment time of 30 to 180 seconds and a power of 20 to 100 W.

[0010] By adopting the above technical solution and using low-temperature plasma treatment as a surface activation method, the polyurethane foam is treated under conditions of 30 to 180 seconds and 20 to 100 W. Polar functional groups can be effectively introduced, significantly improving the reactivity and wettability of the foam surface. The treatment method is gentle and efficient, and can maintain the integrity of the foam structure while enhancing the adhesion strength of subsequent grafting modification and antimicrobial agent loading, thereby providing a key foundation for constructing a stable and long-lasting antimicrobial functional layer, and improving the antimicrobial performance and service life of the dressing.

[0011] The grafting modification in step (3) is performed by grafting using γ-aminopropyltriethoxysilane (APTES), 3-mercaptopropyltrimethoxysilane or polyethyleneimine.

[0012] By adopting the above technical solution and using γ-aminopropyltriethoxysilane (APTES), 3-mercaptopropyltrimethoxysilane or polyethyleneimine for grafting modification, active functional groups such as amino groups and mercapto groups can be introduced into the surface of polyurethane foam, thereby enhancing the binding ability and load stability of the foam surface to antibacterial agents. The grafting process can form stable chemical bonds, improve the durability and functional persistence of the antibacterial layer, provide reaction sites for the subsequent efficient fixation of antibacterial ingredients such as nanosilver and quaternary ammonium salts, and significantly improve the antibacterial properties and usage effects of the dressing.

[0013] Optionally, the antibacterial agent in step (4) is nanosilver particles with a particle size between 10 and 50 nm, which are loaded on the foam surface by impregnation or in-situ reduction method.

[0014] By adopting the above technical solution, using nanosilver particles with a particle size between 10 and 50 nm, and loading them on the foam surface by impregnation or in situ reduction method, the uniform distribution and firm attachment of nanosilver can be achieved, effectively improving the antibacterial activity and durability of the foam dressing. Nanosilver has broad-spectrum and long-lasting antibacterial properties, which can effectively inhibit the growth of common pathogenic microorganisms and reduce the risk of wound infection. The impregnation or in situ reduction method is simple to operate and has strong adaptability, which helps to improve the loading efficiency and safety of antibacterial agents, thereby enhancing the clinical application value of the dressing.

[0015] Optionally, the antimicrobial effectiveness of the foam dressing surface after antimicrobial loading reaches more than 99%, and it has an antibacterial effect on Staphylococcus aureus and Escherichia coli.

[0016] By adopting the above technical solution, the antibacterial effectiveness of the foam dressing surface after antimicrobial agent loading can reach more than 99%, showing significant antibacterial effects on Staphylococcus aureus and Escherichia coli, indicating that it has excellent broad-spectrum antibacterial properties. The dressing can continuously inhibit bacterial growth on the wound contact surface and reduce the incidence of infection. It is particularly suitable for chronic wounds, postoperative wounds and other prone to infection scenarios. The efficient and long-lasting antibacterial ability improves the therapeutic safety and use cycle of the dressing, providing a strong guarantee for promoting wound healing and reducing the frequency of dressing changes.

[0017] Optionally, the polyurethane foam has a pore size of 100 to 300 μm, a porosity of 80% to 95%, and a thickness of 2 to 8 mm.

[0018] By adopting the above-mentioned technical solutions, its liquid absorption, breathability and softness can be significantly optimized, so that the dressing has good cushioning and fitting properties while maintaining a moist environment for the wound. The appropriate pore size and high porosity are conducive to absorbing exudate and promoting gas exchange, reducing the risk of infection and improving patient comfort. The moderate thickness takes into account both protection and flexibility, enhancing the comprehensive application performance of the dressing in wound coverage, antibacterial protection and tissue repair.

[0019] Optionally, the antibacterial performance stability of the dressing remains unchanged for more than 7 days in wet, dry and body fluid simulated environments.

[0020] Optionally, the chitosan in step (4) is water-soluble chitosan with a degree of deacetylation between 70% and 90% and a molecular weight between 50 and 200 kDa, and is loaded on the foam surface by electrostatic adsorption.

[0021] By adopting the above technical solution, the mild fixation and sustained release of antibacterial ingredients can be achieved. Chitosan has good biocompatibility and natural antibacterial activity, which can effectively inhibit the growth of various bacteria while promoting tissue repair. The electrostatic adsorption method is simple and efficient, does not destroy the foam structure, and helps to improve the loading efficiency and the stability of the antibacterial layer, thereby enhancing the anti-infection ability of the dressing and promoting wound healing.

[0022] Optionally, the polyurethane foam dressing can be further laminated with a medical non-woven fabric or a silicone gel backing layer to form a composite dressing to improve mechanical strength and comfort; The surface-modified foam dressing also showed a significant inhibitory effect on Pseudomonas aeruginosa in in vitro antibacterial tests; This method does not change the original liquid absorption capacity and softness of the foam. The liquid absorption capacity can reach more than 10 times its own weight, and the softness meets the requirements of medical materials for skin contact.

[0023] By adopting the above technical solution, polyurethane foam dressing can be laminated with medical non-woven fabric or silicone gel backing layer to form a composite dressing with higher mechanical strength and wearing comfort, thereby improving clinical application performance. After surface modification, the dressing also showed significant inhibitory effect on Pseudomonas aeruginosa in in vitro antibacterial tests, and has broad-spectrum antibacterial ability without affecting the original liquid absorption capacity and softness of the foam. The liquid absorption capacity is more than 10 times its own weight, meeting the dual requirements of medical dressings in exudate management and skin contact comfort.

[0024] In summary, this application includes at least one of the following beneficial technical effects: It has a significant inhibitory effect on common pathogens such as Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, with an antibacterial effectiveness of over 99%, enhancing the anti-infection ability in wound management and realizing the broad-spectrum antibacterial function of foam dressings; The foam's inherent absorbency and softness remain unchanged, retaining its ability to absorb more than 10 times its own weight, maintaining the soft contact properties required of medical materials and ensuring patient comfort. Surface activation through plasma, ozone or alkali treatment significantly enhances the grafting efficiency of functional molecules on the foam surface, providing reaction sites for building a stable antibacterial layer; Adopting a synergistic strategy of grafting and antimicrobial loading, the stable loading of nanosilver, quaternary ammonium salt or chitosan ensures long-lasting antimicrobial properties and effectively reduces the frequency of dressing changes; Medical non-woven fabric or silicone gel backing layer can be selectively introduced to further improve the overall mechanical strength and wearing comfort of the dressing, broadening its application range in different clinical scenarios; The foam substrate with an open pore structure and high porosity has excellent breathability, cushioning and fit, meeting the dual needs of maintaining a moist environment and absorbing exudate during wound healing. The antibacterial properties remain stable for more than 7 days in wet, dry and body fluid simulated environments, effectively extending the use cycle of the dressing and improving the efficiency and economy of wound healing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a process flow chart of a method for preparing an antibacterial surface-modified polyurethane foam dressing according to an embodiment of the present application. DETAILED DESCRIPTION

[0026] The following is combined with Figure 1 This application is described in further detail.

[0027] The present invention discloses a method for preparing an antibacterial surface-modified polyurethane foam dressing. Figure 1 , a method for preparing an antibacterial surface-modified polyurethane foam dressing, the method comprising the following steps: (1) Preparation of polyurethane foam substrate: polyol and isocyanate are reacted to form a foam to obtain a polyurethane foam with an open cell structure; (2) Surface pretreatment: Activate the polyurethane foam surface by plasma treatment, ozone oxidation or alkali treatment; (3) Grafting modification: Grafting polymer segments with antibacterial groups or silane reagents containing functional groups onto the activated surface; (4) Antimicrobial loading: loading nanosilver, quaternary ammonium salt or chitosan antimicrobial agents on the modified surface; (5) Post-treatment and drying: The unreacted residues are removed by water washing, and then the polyurethane foam dressing with antibacterial surface modification is obtained by low-temperature drying and molding.

[0028] The specific implementation is as follows: 1. Raw materials Polyether polyol (molecular weight about 3000) Toluene diisocyanate (TDI) Foaming agent: distilled water Catalyst: tertiary amine catalyst Surfactants: low-temperature plasma, ozone treatment system Grafting reagents: γ-aminopropyltriethoxysilane (APTES), polyethyleneimine (PEI) Antibacterial agents: nanosilver (particle size 20nm), water-soluble chitosan (deacetylation degree 80%, molecular weight 100kDa), quaternary ammonium compounds Others: ethanol, deionized water, etc. 2. Preparation steps Step (1): Preparation of polyurethane foam substrate Polyether polyol and TDI were mixed in a mass ratio of 100:40, 1.5 wt% distilled water was added as a blowing agent, and 0.3 wt% of a tertiary amine catalyst was added. After stirring thoroughly, the mixture was quickly poured into a mold and foamed at room temperature. After standing for 24 hours, the foam was cut into 5 mm thick sheets. The resulting foam had a well-defined open-cell structure with a pore size of 100 to 300 μm and a porosity of 85%.

[0029] Step (2): Foam surface activation treatment The foam sheet was placed in a low-temperature plasma treatment system at a power of 60W for 120 seconds, using air as the working gas. After treatment, a large number of active hydroxyl and carboxyl functional groups were formed on the foam surface, increasing its surface energy and reactivity.

[0030] Step (3): Graft modification The plasma-treated foam sample was immersed in a 2% APTES-ethanol solution for 2 hours at room temperature, then rinsed three times with anhydrous ethanol. The sample was then dried in a vacuum oven at 70°C for 1 hour to complete the APTES grafting. Alternatively, surface amino functionalization can be achieved by immersing the foam in a 1% PEI aqueous solution for 1 hour.

[0031] Step (4): Antimicrobial loading a) Silver nanoparticle loading: Immerse the grafted foam sheet in a AgNO3 solution containing 0.1 mM silver ions and let it stand for 30 minutes. Then, add an appropriate amount of reducing agent (such as glucose) and react at 50°C for 1 hour to form in situ reduced silver nanoparticles. Silver particles are evenly deposited on the foam surface.

[0032] b) Chitosan loading: The modified foam sheet was immersed in a 1% water-soluble chitosan solution (pH = 5.5) to allow chitosan to adsorb on the surface through electrostatic adsorption. After standing for 2 hours, the sheet was removed, washed with deionized water, and vacuum dried.

[0033] c) Quaternary ammonium salt loading: The modified foam was immersed in a 0.5% quaternary ammonium salt aqueous solution, reacted for 1 hour, taken out, rinsed three times with deionized water, and vacuum dried.

[0034] Step (5): Post-processing and drying All samples treated with antimicrobial agents were washed three times in deionized water to remove free antimicrobial components, and then dried in a vacuum oven at 50°C for 4 hours to obtain the final antimicrobial surface-modified polyurethane foam dressing.

[0035] 3. Examples [Example 1] The polyurethane foam was loaded with nanosilver using the APTES grafting + in-situ reduction method. After surface activation, it was grafted with 2% APTES, immersed in 0.1 mM AgNO3 solution, and then loaded with silver using glucose as a reducing agent to prepare sample A1.

[0036] [Example 2] PEI grafting + chitosan loading The foam surface was activated by plasma, grafted with 1% PEI, and then adsorbed with 1% chitosan solution to prepare sample A2.

[0037] [Example 3] Ozone treatment + quaternary ammonium salt loading The foam surface was oxidized by ozone for 30 minutes and then directly loaded with 0.5% quaternary ammonium salt solution to prepare sample A3.

[0038] [Example 4] Alkali treatment + dual antimicrobial agent composite loading The foam was treated with 0.1M NaOH, first loaded with nanosilver, and then adsorbed with chitosan to obtain sample A4.

[0039] 4. Performance Testing The antibacterial properties were tested according to GB / T 20944.3-2008 standard, using inhibition zone and colony count tests on Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The results are as follows: The antibacterial rate of sample A1 was >99.9%, with obvious inhibition zone; Sample A2 had a good inhibitory effect on G+ and G- bacteria, with an antibacterial rate of over 95%; Sample A3 showed moderate antibacterial effect; The antibacterial rate of the A4 sample reached over 99%, and it had an inhibitory effect on a variety of bacteria.

[0040] Liquid absorption performance: PBS solution was used for liquid absorption test. The foam absorption capacity (weight ratio) was tested as follows: A1: 12.4 times; A2: 11.7 times; A3: 10.9 times; A4: 12.1 times.

[0041] This shows that the modification does not affect the original foam's liquid absorption properties and it still has good liquid absorption capacity.

[0042] The softness test used tensile stress-strain curve to test the softness of the foam before and after modification. The results showed that the elastic modulus of the sample changed by <10%, which can meet the skin adhesion requirements of medical dressings.

[0043] Stability test: The samples were placed in simulated sweat and artificial body fluids and soaked for 7 days before being taken out to test the antibacterial activity: Samples A1 and A4 still maintained an antibacterial rate of >95%, indicating good antibacterial stability; The A2 sample decreased slightly but was still >85%.

[0044] 5. Further Optimization The above-mentioned modified foam is laminated with medical non-woven fabric or silicone gel backing by hot pressing or gluing to improve the overall structural strength and adhesion comfort of the dressing, forming a composite antibacterial foam dressing, which is suitable for clinical scenarios such as chronic wound management, diabetic foot, and pressure sores.

[0045] The implementation principle of the method for preparing an antibacterial surface-modified polyurethane foam dressing in the embodiment of the present application is as follows: first, in the substrate preparation stage, a polymerization reaction is carried out using polyether polyol and toluene diisocyanate (TDI), and distilled water is added as a foaming agent and a tertiary amine catalyst to achieve foaming molding at room temperature. During the foaming process, carbon dioxide is released, and a large number of pores with a diameter of 100 to 300 are formed during the curing process. The open microporous structure with a porosity of about 85% and a pore size between μm provides a good physical basis for subsequent surface modification and antimicrobial agent loading, and also ensures the excellent liquid absorption performance of the foam material; secondly, in the surface treatment of the foam substrate, physical or chemical methods are used for surface activation to improve the binding ability of the foam with functional molecules. Three technical means are selected: plasma treatment, ozone oxidation or alkali treatment. In implementation, low-temperature air plasma treatment is used. High-energy plasma acts on the surface of polyurethane to introduce polar functional groups such as hydroxyl and carboxyl groups, significantly improving the surface energy and hydrophilicity, and providing active sites for subsequent grafting. Similar purposes can be achieved by using ozone or NaOH alkali treatment, but there may be a certain impact on the foam pore structure; the third step is to perform grafting modification operations based on the activated foam surface. , by immersing the foam sheet in a silane or polymer solution containing functional groups, the grafting reaction is promoted. Among them, silane grafting agents represented by γ-aminopropyltriethoxysilane (APTES) can hydrolyze and condense on the surface rich in hydroxyl groups to generate silicon-oxygen-carbon bonds and introduce amino functional groups; polyethyleneimine (PEI) enhances the surface amino density through a multi-amino structure, which not only improves the affinity of the foam surface to antibacterial agents, but also enhances the loading stability through electrostatic effects; the fourth step is to select physical adsorption or in situ reaction methods to load functional components with broad-spectrum antibacterial effects according to the chemical properties of different grafted surfaces. For example, using the in situ reduction method, the foam surface is first immersed in a silver nitrate (AgNO3) solution, and then a reducing agent (such as glucose) is added to generate particles of about 20 mm in size at a lower temperature. nm nanosilver is adsorbed and stably deposited on the foam pore wall; or the electrostatic adsorption principle is used to make natural polymers such as chitosan adsorbed on the positively charged amino grafted layer under pH control; in addition, quaternary ammonium salt cationic antibacterial agents can also be combined with the foam surface by immersion method. By regulating the type of antibacterial agent and the loading method, the foam can be given excellent broad-spectrum antibacterial ability while taking into account biocompatibility; in the fifth step, to ensure the purity and safety of the final product, the foam needs to be repeatedly rinsed with deionized water to remove unbound antibacterial components and reaction by-products, and then dried in a vacuum drying oven at 50°C to ensure that the foam maintains a stable structure and has long-term storage stability. After this step, a polyurethane foam dressing with good surface modification structure, stable antibacterial performance, softness and fit is obtained.

[0046] In the specific implementation, different surface treatment methods and types of antimicrobial agents were combined to form multiple representative samples. For example, sample A1 was grafted with APTES and loaded with nanosilver, showing an antibacterial rate of >99.9% and a significant inhibition zone; A2 was grafted with PEI and loaded with chitosan, and performed outstandingly in terms of both antibacterial and biocompatibility; A3 was directly loaded with quaternary ammonium salts through ozone treatment, which was easy to operate and had moderate antibacterial effect; A4 was treated with alkali combined with nanosilver and chitosan composite loading to achieve multi-mechanism antibacterial synergy and exhibit excellent broad-spectrum antibacterial properties; in terms of performance testing, based on the national standard GB / T 20944.3-2008, the antibacterial properties of the samples were tested by colony counting and inhibition zone determination, which showed that the samples had excellent inhibitory effects on Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, especially the samples containing nanosilver or composite antibacterial treatment, with the inhibition rate generally exceeding 99%. In terms of liquid absorption capacity, samples A1-A4 all showed a liquid absorption ratio of more than 10 times, and the surface modification did not significantly affect the original liquid absorption capacity of the foam; the softness test results showed that the foam elastic modulus changed by less than 10%, which can effectively fit the skin and ensure the comfort of the wound; after soaking in simulated sweat and artificial body fluids for 7 days, most samples still maintained an antibacterial rate of more than 85%, indicating that the antibacterial components are stably combined and have good tolerance to the body fluid environment.

[0047] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preparing an antibacterial surface-modified polyurethane foam dressing, characterized in that: The method comprises the following steps: (1) Preparation of polyurethane foam substrate: polyol and isocyanate are reacted to form a foam to obtain a polyurethane foam with an open cell structure; (2) Surface pretreatment: Activate the polyurethane foam surface by plasma treatment, ozone oxidation or alkali treatment; (3) Grafting modification: Grafting polymer segments with antibacterial groups or silane reagents containing functional groups onto the activated surface; (4) Antimicrobial loading: loading nanosilver, quaternary ammonium salt or chitosan antimicrobial agents on the modified surface; (5) Post-treatment and drying: The unreacted residues are removed by water washing, and then the polyurethane foam dressing with antibacterial surface modification is obtained by low-temperature drying and molding.

2. The method according to claim 1, wherein: In step (1), the polyol is a polyether polyol or a polyester polyol, and the isocyanate is toluene diisocyanate (TDI) or isophorone diisocyanate (IPDI).

3. The method according to claim 1, wherein: The surface activation method in step (2) is low-temperature plasma treatment, with a treatment time of 30 to 180 seconds and a power of 20 to 100 W.

4. The method according to claim 1, wherein: The grafting modification in step (3) is performed by grafting using γ-aminopropyltriethoxysilane (APTES), 3-mercaptopropyltrimethoxysilane or polyethyleneimine.

5. The method according to claim 1, wherein: The antibacterial agent in step (4) is nanosilver particles with a particle size between 10 and 50 nm, which are loaded on the foam surface by impregnation or in-situ reduction method.

6. The method according to claim 1, wherein: The antibacterial effectiveness of the foam dressing surface after loading with antimicrobial agents reaches more than 99%, and it has an antibacterial effect on Staphylococcus aureus and Escherichia coli.

7. The method according to claim 1, wherein: The polyurethane foam has a pore diameter of 100 to 300 μm, a porosity of 80% to 95%, and a thickness of 2 to 8 mm.

8. The method according to claim 1, characterized in that The antibacterial performance stability of the dressing remains unchanged for more than 7 days in wet, dry and body fluid simulated environments.

9. The method according to claim 1, wherein: The chitosan in step (4) is a water-soluble chitosan with a deacetylation degree of 70% to 90% and a molecular weight of 50 to 200 kDa, which is loaded on the foam surface by electrostatic adsorption.

10. The method according to claim 1, wherein: The polyurethane foam dressing can be further laminated with a medical non-woven fabric or a silicone gel backing layer to form a composite dressing to improve mechanical strength and comfort; The surface-modified foam dressing also showed a significant inhibitory effect on Pseudomonas aeruginosa in in vitro antibacterial tests; This method does not change the original liquid absorption capacity and softness of the foam. The liquid absorption capacity can reach more than 10 times its own weight, and the softness meets the requirements of medical materials for skin contact.

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