A polyurethane foam dressing and a method of making the same

Abstract

The application relates to the technical field of medical dressings, in particular to a polyurethane foam dressing and a preparation method thereof. The polyurethane foam dressing is prepared by adding raw materials such as polyethylene glycol, polyhydroxy chitosan, polyhydroxy ortho-phthalic triol, antibacterial silicon dioxide, a foaming agent and 2,6-toluene diisocyanate, and then performing heat curing. The polyurethane foam dressing prepared by the application has good antibacterial and anti-inflammatory effects, so that the application has a wide application prospect in the technical field of medical dressings.

Description

Technical Field

[0001] This invention relates to the field of medical dressing technology, specifically a polyurethane foam dressing and its preparation method. Background Technology

[0002] In the field of modern wound care, polyurethane foam dressings, due to their unique three-dimensional porous structure, can effectively maintain the ideal moisture balance of the wound surface, preventing tissue maceration and avoiding the drying and damage of newly formed granulation tissue. This makes them irreplaceable in the treatment of acute and chronic wounds (such as venous ulcers, pressure ulcers, and postoperative wounds).

[0003] However, in the complex physiological process of wound healing, microbial infection and wound inflammation can easily lead to delayed healing and treatment failure. Once a wound becomes clinically infected and inflamed, it significantly prolongs hospital stays, increases the cost of debridement and the use of advanced antibiotics, and exacerbates patient suffering. Therefore, it is essential to improve the antibacterial and anti-inflammatory properties of polyurethane foam dressings to enhance healing quality and efficiency, improve patient prognosis, and reduce the social burden on healthcare.

[0004] To overcome the shortcomings of the prior art, the present invention provides a polyurethane foam dressing and a method for preparing the same. Summary of the Invention

[0005] The purpose of this invention is to provide a polyurethane foam dressing and its preparation method to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a polyurethane foam dressing includes the following steps: mixing polyethylene glycol, polyhydroxy chitosan, and polyhydroxy pyrogallol, stirring evenly, then adding antibacterial silica, a foaming agent, a catalyst, and a surfactant, heating and stirring, and allowing to stand to obtain a mixed solution; then adding 2,6-toluene diisocyanate to the mixed solution, stirring evenly, transferring to a mold, and curing to obtain the finished product;

[0008] Polyhydroxy chitosan was obtained by adding thioglycerol to modify the modified chitosan; polyhydroxy pyrogallol was obtained by adding thioglycerol to modify the modified pyrogallol; antibacterial silica was obtained by modifying silver-loaded silica with Schiff base.

[0009] In a more optimized manner, the content of each component in the finished dressing is as follows: by mass parts, 50-60 parts polyethylene glycol, 10-15 parts polyhydroxy chitosan, 10-15 parts polyhydroxy pyrogallol, 5-7 parts antibacterial silica, 1.5-2.0 parts foaming agent, 0.6-0.8 parts catalyst, 0.5-0.7 parts surfactant, and 35-45 parts 2,6-toluene diisocyanate; wherein the foaming agent is distilled water, the catalyst is triethylenediamine, and the surfactant is silicone oil.

[0010] Ideally, the mixture should be heated and stirred at 50-60℃ for 10-15 minutes, and then matured at 60-70℃ for 8-10 hours.

[0011] A more optimized preparation process for polyhydroxy chitosan is as follows:

[0012] Step S1: Mix carboxymethyl chitosan and deionized water, stir and dissolve at 60-65℃, then add trans-2-hexenal solution dropwise, cool to 45-50℃ and stir for 5-6 hours. After the reaction is completed, extract, filter, wash and dry to obtain modified chitosan.

[0013] Step S2: Thioglycerol, modified chitosan, and photoinitiator 1173 are added to tetrahydrofuran, stirred evenly, and then irradiated with ultraviolet light for 15-20 minutes. After the reaction is completed, the mixture is washed, dried, and rotary evaporated to obtain polyhydroxy chitosan.

[0014] In a more optimized manner, a trans-2-hexenal solution was added to anhydrous ethanol and stirred to obtain a trans-2-hexenal solution; wherein the reaction mass ratio of carboxymethyl chitosan to trans-2-hexenal was 1:(0.15-0.20); and the reaction mass ratio of thioglycerol, modified chitosan, and photoinitiator 1173 was (0.20-0.25):1:0.02.

[0015] A more optimized preparation process for polyhydroxypyrogallol is as follows:

[0016] Step S1: Add pyrogallol and N-hydroxymethylacrylamide to anhydrous ethanol, stir to dissolve, heat to 35-40℃, stir mechanically until uniform, add concentrated sulfuric acid dropwise, seal and react for 2-3 days after the addition is complete, add deionized water after the reaction is complete, stir and react for 3-4 hours, let stand for 1.0-1.5 days, then filter, wash, recrystallize and dry to obtain modified pyrogallol;

[0017] Step S2: Thioglycerol, modified pyrogallol, and photoinitiator 1173 are added to tetrahydrofuran, stirred evenly, and then irradiated with ultraviolet light for 15-20 minutes. After the reaction is completed, the mixture is washed, dried, and rotary evaporated to obtain polyhydroxypyrogallol.

[0018] In a more optimized manner, the reaction mass ratio of pyrogallol to N-hydroxymethylacrylamide is 1:(3.2-3.5); the reaction mass ratio of thioglycerol, modified pyrogallol, and photoinitiator 1173 is (0.8-1.0):1:0.02.

[0019] A more optimized preparation process for antibacterial silica is as follows:

[0020] Step S1: Add nano-silica microspheres to deionized water, disperse evenly by ultrasonication, then add 0.018-0.020 g / mL of silver nitrate solution, stir at 40-45℃ for 2.5-3.5 h until the solution changes from light color to dark color. After stirring, cool, centrifuge, wash with water and dry to obtain silver-loaded silica.

[0021] Step S2: Add γ-aminopropyltriethoxysilane to a mixed solvent of ethanol and deionized water, stir evenly, adjust the pH to 4.0-4.5, then add silver-loaded silica, ultrasonically disperse for 30-40 min, heat to 70-75℃ and stir for 8-10 h. After stirring, filter, wash and dry to obtain modified silver-loaded silica.

[0022] Step S3: Add modified silver-loaded silica and 2,3-dihydroxybenzaldehyde to anhydrous ethanol and reflux at 70-75℃ for 4-6 hours. After the reaction is completed, cool, filter under reduced pressure, wash and dry to obtain antibacterial silica.

[0023] In a more optimized manner, the mass ratio of nano-silica microspheres to silver nitrate is 20:(1.0-1.3); the mass ratio of γ-aminopropyltriethoxysilane to silver-loaded silica is 1:(10-15); and the mass ratio of modified silver-loaded silica to 2,3-dihydroxybenzaldehyde is 1:(0.10-0.13).

[0024] The beneficial effects of this invention are:

[0025] The key feature of this invention is that by adding carboxymethyl chitosan and trans-2-hexenal, the numerous amino groups on the carboxymethyl chitosan chain undergo a Schiff base reaction with the aldehyde groups to obtain modified chitosan. The Schiff base structure formed in this step can affect the activity of related enzymes on and inside the cell membrane by disrupting the cell membrane, thereby influencing bacterial metabolic activities. Furthermore, the remaining amino groups in the chitosan itself can also be adsorbed onto the negatively charged bacterial cell membrane through electrostatic interactions, disrupting its structural integrity and synergistically enhancing the antibacterial effect. By adding pyrogallol and N-hydroxymethylacrylamide, a Friedel-Crafts alkylation reaction occurs, yielding modified pyrogallol with active carbon-carbon double bonds. The polyphenolic structure of this modified pyrogallol enables it to effectively scavenge various ROS such as superoxide anions, hydroxyl radicals, and peroxide radicals, thus exhibiting good anti-inflammatory effects. In addition, as a typical polyphenol, pyrogallol allows the modified product to penetrate into the bacterial cell membrane, interacting with membrane proteins and lipids, increasing membrane permeability, and leading to the leakage of key intracellular substances.

[0026] The invention is characterized by further mixing the modified chitosan with thioglycerol and photoinitiator 1173 to undergo a mercapto-olefin click reaction, yielding polyhydroxy chitosan. Similarly, mixing modified pyrogallol with thioglycerol and photoinitiator 1173 to undergo a mercapto-olefin click reaction yields polyhydroxy pyrogallol. Through the mercapto-olefin reaction, multiple active hydroxyl groups are introduced onto the surfaces of the modified chitosan and modified pyrogallol, respectively. The resulting polyhydroxy chitosan and polyhydroxy pyrogallol can then crosslink with isocyanate groups, effectively participating in the structure of polyurethane foam dressings to form dressings with good antibacterial and anti-inflammatory effects.

[0027] The invention is characterized by the reaction of nano-silica microspheres and silver nitrate in a solvent to obtain silver-loaded silica. The silver-loaded silica is then modified with γ-aminopropyltriethoxysilane to introduce amino groups onto its surface, resulting in modified silver-loaded silica. The modified silver-loaded silica is then mixed with 2,3-dihydroxybenzaldehyde to undergo a Schiff base reaction, yielding antibacterial silica. During heating, the abundant silanol groups on the SiO2 surface act as a weak reducing agent, reducing Ag... + The silver nanoparticles are reduced to metallic silver and loaded onto a SiO2 microsphere structure. These silver nanoparticles exhibit excellent bactericidal effects, interfering with bacterial respiratory chain enzymes and DNA replication. Synergistically with the Schiff base antibacterial structure, a highly effective antibacterial silica is obtained. Furthermore, both the nano-silver and the Schiff base organic structure are immobilized on the SiO2 support, preventing rapid loss of the antibacterial components and ensuring long-lasting antibacterial effects.

[0028] The invention is characterized by mixing polyethylene glycol, polyhydroxy chitosan, and polyhydroxy pyrogallol, stirring until homogeneous, then adding antibacterial silica, a foaming agent, a catalyst, and a surfactant. After heating, stirring, and settling, a mixed solution is obtained. Then, 2,6-toluene diisocyanate is added to the mixed solution, stirred until homogeneous, transferred to a mold, and cured to obtain the finished polyurethane foam dressing. Polyhydroxy chitosan, polyhydroxy pyrogallol, and antibacterial silica are effectively incorporated into the structure of the polyurethane dressing through chemical bonds, thus enabling the dressing to effectively combat infection, actively control inflammation, and promote wound healing, exhibiting excellent overall performance. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Raw material source:

[0031] Carboxymethyl chitosan, provided by Wuhan Shuer Biotechnology Co., Ltd., 200 mesh; nano-silica microspheres, provided by Qinghe County Chaotai Metal Materials Co., Ltd., 2000 mesh; polyethylene glycol, provided by Jinan Xinke Chemical Co., Ltd., model PEG400; silicone oil, provided by Jinan Changyingda Chemical Co., Ltd., model 350cs; concentrated sulfuric acid, provided by Sinopharm Chemical Reagent Co., Ltd., analytical grade; by mass parts, one part is 1g.

[0032] Example 1: Step S1: Carboxymethyl chitosan and deionized water were mixed and stirred at 65°C to dissolve. Then, trans-2-hexenal solution was added dropwise. The mixture was cooled to 50°C and stirred for 6 hours. After the reaction was completed, the mixture was extracted, filtered, washed, and dried to obtain modified chitosan. The trans-2-hexenal solution was added to anhydrous ethanol and stirred to obtain a trans-2-hexenal solution. The mass ratio of carboxymethyl chitosan to trans-2-hexenal was 1:0.17.

[0033] Step S2: Thioglycerol, modified chitosan, and photoinitiator 1173 were added to tetrahydrofuran, stirred evenly, and then irradiated with a UV lamp for 20 minutes. After the reaction was completed, the mixture was washed, dried, and rotary evaporated to obtain polyhydroxy chitosan. The mass ratio of thioglycerol, modified chitosan, and photoinitiator 1173 was 0.23:1:0.02.

[0034] Step S3: Add pyrogallol and N-hydroxymethylacrylamide to anhydrous ethanol, stir to dissolve, heat to 40°C, mechanically stir until homogeneous, and then add concentrated sulfuric acid dropwise. After the addition is complete, seal and react for 3 days. After the reaction is complete, add deionized water, stir and react for 4 hours, and then let stand for 1.5 days. Then filter, wash, recrystallize and dry to obtain modified pyrogallol. The mass ratio of pyrogallol to N-hydroxymethylacrylamide is 1:3.4.

[0035] Step S4: Thioglycerol, modified pyrogallol, and photoinitiator 1173 were added to tetrahydrofuran, stirred evenly, and then irradiated with a UV lamp for 20 min. After the reaction was completed, the mixture was washed, dried, and rotary evaporated to obtain polyhydroxypyrogallol. The mass ratio of thioglycerol, modified pyrogallol, and photoinitiator 1173 was 0.9:1:0.02.

[0036] Step S5: Add nano-silica microspheres to deionized water, ultrasonically disperse them evenly, then add 0.018 g / mL silver nitrate solution, stir at 45℃ for 3.5 h until the solution changes from light to dark color. After stirring, cool, centrifuge, wash with water, and dry to obtain silver-loaded silica; the mass ratio of nano-silica microspheres to silver nitrate is 20:1.1.

[0037] Step S6: Add γ-aminopropyltriethoxysilane to a mixed solvent of ethanol and deionized water, stir until homogeneous, adjust the pH to 4.5, then add silver-loaded silica, ultrasonically disperse for 40 min, heat to 75℃ and stir for 10 h. After stirring, filter, wash and dry to obtain modified silver-loaded silica; the mass ratio of γ-aminopropyltriethoxysilane to silver-loaded silica is 1:12.

[0038] Step S7: Modified silver-loaded silica and 2,3-dihydroxybenzaldehyde were added to anhydrous ethanol and refluxed at 75°C for 6 hours. After the reaction was completed, the silica was cooled, filtered under reduced pressure, washed, and dried to obtain antibacterial silica. The mass ratio of modified silver-loaded silica to 2,3-dihydroxybenzaldehyde was 1:0.11.

[0039] Step S8: Mix 55g polyethylene glycol, 12g polyhydroxy chitosan, and 12g polyhydroxy pyrogallol, stir well, then add 6g antibacterial silica, 1.7g distilled water, 0.7g triethylenediamine, and 0.6g silicone oil. Heat and stir at 60℃ for 15 minutes, then let stand to obtain a mixed solution. Add 40g 2,6-toluene diisocyanate to the mixed solution, stir well, transfer to a mold, and cure at 70℃ for 10 hours to obtain the finished product.

[0040] Example 2: Step S1: Carboxymethyl chitosan and deionized water were mixed and stirred at 62°C to dissolve. Then, trans-2-hexenal solution was added dropwise. The mixture was cooled to 47°C and stirred for 5.5 hours. After the reaction was completed, the mixture was extracted, filtered, washed, and dried to obtain modified chitosan. The trans-2-hexenal solution was added to anhydrous ethanol and stirred to obtain a trans-2-hexenal solution. The mass ratio of carboxymethyl chitosan to trans-2-hexenal was 1:0.17.

[0041] Step S2: Thioglycerol, modified chitosan, and photoinitiator 1173 were added to tetrahydrofuran, stirred evenly, and then irradiated with a UV lamp for 17 minutes. After the reaction was completed, the mixture was washed, dried, and rotary evaporated to obtain polyhydroxy chitosan. The mass ratio of thioglycerol, modified chitosan, and photoinitiator 1173 was 0.23:1:0.02.

[0042] Step S3: Add pyrogallol and N-hydroxymethylacrylamide to anhydrous ethanol, stir to dissolve, heat to 37°C, mechanically stir until homogeneous, and then add concentrated sulfuric acid dropwise. After the addition is complete, seal and react for 2.5 days. After the reaction is complete, add deionized water, stir and react for 3.5 hours, and then let stand for 1.3 days. Then filter, wash, recrystallize, and dry to obtain modified pyrogallol. The mass ratio of pyrogallol to N-hydroxymethylacrylamide is 1:3.4.

[0043] Step S4: Thioglycerol, modified pyrogallol, and photoinitiator 1173 were added to tetrahydrofuran, stirred evenly, and then irradiated with a UV lamp for 17 min. After the reaction was completed, the mixture was washed, dried, and rotary evaporated to obtain polyhydroxypyrogallol. The mass ratio of thioglycerol, modified pyrogallol, and photoinitiator 1173 was 0.9:1:0.02.

[0044] Step S5: Add nano-silica microspheres to deionized water, disperse evenly by ultrasonication, then add 0.018 g / mL silver nitrate solution, stir at 43℃ for 3 h until the solution changes from light to dark color, after stirring, cool, centrifuge, wash with water and dry to obtain silver-loaded silica; the mass ratio of nano-silica microspheres to silver nitrate is 20:1.1;

[0045] Step S6: Add γ-aminopropyltriethoxysilane to a mixed solvent of ethanol and deionized water, stir until homogeneous, adjust the pH to 4.3, then add silver-loaded silica, ultrasonically disperse for 35 min, heat to 72℃ and stir for 9 h. After stirring, filter, wash and dry to obtain modified silver-loaded silica; the mass ratio of γ-aminopropyltriethoxysilane to silver-loaded silica is 1:12.

[0046] Step S7: Modified silver-loaded silica and 2,3-dihydroxybenzaldehyde were added to anhydrous ethanol and refluxed at 72°C for 5 hours. After the reaction was completed, the silica was cooled, filtered under reduced pressure, washed, and dried to obtain antibacterial silica. The mass ratio of modified silver-loaded silica to 2,3-dihydroxybenzaldehyde was 1:0.11.

[0047] Step S8: Mix 55g polyethylene glycol, 12g polyhydroxy chitosan, and 12g polyhydroxy pyrogallol, stir well, then add 6g antibacterial silica, 1.7g distilled water, 0.7g triethylenediamine, and 0.6g silicone oil. Heat and stir at 55℃ for 12 minutes, then let stand to obtain a mixed solution. Add 40g 2,6-toluene diisocyanate to the mixed solution, stir well, transfer to a mold, and cure at 65℃ for 9 hours to obtain the finished product.

[0048] Example 3: Step S1: Carboxymethyl chitosan and deionized water were mixed and stirred at 60°C to dissolve. Then, trans-2-hexenal solution was added dropwise. The mixture was cooled to 45°C and stirred for 5 hours. After the reaction was completed, the mixture was extracted, filtered, washed, and dried to obtain modified chitosan. The trans-2-hexenal solution was added to anhydrous ethanol and stirred to obtain a trans-2-hexenal solution. The mass ratio of carboxymethyl chitosan to trans-2-hexenal was 1:0.17.

[0049] Step S2: Thioglycerol, modified chitosan, and photoinitiator 1173 were added to tetrahydrofuran, stirred evenly, and then irradiated with a UV lamp for 15 minutes. After the reaction was completed, the mixture was washed, dried, and rotary evaporated to obtain polyhydroxy chitosan. The mass ratio of thioglycerol, modified chitosan, and photoinitiator 1173 was 0.23:1:0.02.

[0050] Step S3: Add pyrogallol and N-hydroxymethylacrylamide to anhydrous ethanol, stir to dissolve, heat to 35°C, mechanically stir until homogeneous, and then add concentrated sulfuric acid dropwise. After the addition is complete, seal and react for 2 days. After the reaction is complete, add deionized water, stir and react for 3 hours, and then let stand for 1.0 day. Then filter, wash, recrystallize and dry to obtain modified pyrogallol. The mass ratio of pyrogallol to N-hydroxymethylacrylamide is 1:3.4.

[0051] Step S4: Thioglycerol, modified pyrogallol, and photoinitiator 1173 were added to tetrahydrofuran, stirred evenly, and then irradiated with a UV lamp for 15 min. After the reaction was completed, the mixture was washed, dried, and rotary evaporated to obtain polyhydroxypyrogallol. The mass ratio of thioglycerol, modified pyrogallol, and photoinitiator 1173 was 0.9:1:0.02.

[0052] Step S5: Add nano-silica microspheres to deionized water, disperse evenly by ultrasonication, then add 0.018 g / mL silver nitrate solution, stir at 40℃ for 2.5 h until the solution changes from light to dark color. After stirring, cool, centrifuge, wash with water, and dry to obtain silver-loaded silica; the mass ratio of nano-silica microspheres to silver nitrate is 20:1.1.

[0053] Step S6: Add γ-aminopropyltriethoxysilane to a mixed solvent of ethanol and deionized water, stir until homogeneous, adjust the pH to 4.0, then add silver-loaded silica, ultrasonically disperse for 30 min, heat to 70℃ and stir for 8 h. After stirring, filter, wash and dry to obtain modified silver-loaded silica; the mass ratio of γ-aminopropyltriethoxysilane to silver-loaded silica is 1:12.

[0054] Step S7: Modified silver-loaded silica and 2,3-dihydroxybenzaldehyde were added to anhydrous ethanol and refluxed at 70°C for 4 hours. After the reaction was completed, the silica was cooled, filtered under reduced pressure, washed, and dried to obtain antibacterial silica. The mass ratio of modified silver-loaded silica to 2,3-dihydroxybenzaldehyde was 1:0.11.

[0055] Step S8: Mix 55g polyethylene glycol, 12g polyhydroxy chitosan, and 12g polyhydroxy pyrogallol, stir well, then add 6g antibacterial silica, 1.7g distilled water, 0.7g triethylenediamine, and 0.6g silicone oil. Heat and stir at 50℃ for 10 minutes, then let stand to obtain a mixed solution. Add 40g 2,6-toluene diisocyanate to the mixed solution, stir well, transfer to a mold, and cure at 60℃ for 8 hours to obtain the finished product.

[0056] Comparative Example 1: The polyhydroxy chitosan was removed, and the rest was the same as in Example 1. The specific steps are as follows: Step S1: Pyrogallol and N-hydroxymethylacrylamide were added to anhydrous ethanol, stirred and dissolved, and then heated to 40°C. After mechanical stirring until homogeneous, concentrated sulfuric acid was added dropwise. After the addition was completed, the mixture was sealed and reacted for 3 days. After the reaction was completed, deionized water was added, and the mixture was stirred and reacted for 4 hours. After standing for 1.5 days, the mixture was then filtered, washed, recrystallized, and dried to obtain modified pyrogallol. The mass ratio of pyrogallol to N-hydroxymethylacrylamide was 1:3.4.

[0057] Step S2: Thioglycerol, modified pyrogallol, and photoinitiator 1173 were added to tetrahydrofuran, stirred evenly, and then irradiated with a UV lamp for 20 min. After the reaction was completed, the mixture was washed, dried, and rotary evaporated to obtain polyhydroxypyrogallol. The mass ratio of thioglycerol, modified pyrogallol, and photoinitiator 1173 was 0.9:1:0.02.

[0058] Step S3: Add nano-silica microspheres to deionized water, disperse evenly by ultrasonication, then add 0.018 g / mL silver nitrate solution, stir at 45℃ for 3.5 h until the solution changes from light to dark color. After stirring, cool, centrifuge, wash with water, and dry to obtain silver-loaded silica; the mass ratio of nano-silica microspheres to silver nitrate is 20:1.1.

[0059] Step S4: Add γ-aminopropyltriethoxysilane to a mixed solvent of ethanol and deionized water, stir until homogeneous, adjust the pH to 4.5, then add silver-loaded silica, ultrasonically disperse for 40 min, heat to 75℃ and stir for 10 h. After stirring, filter, wash and dry to obtain modified silver-loaded silica; the mass ratio of γ-aminopropyltriethoxysilane to silver-loaded silica is 1:12.

[0060] Step S5: Modified silver-loaded silica and 2,3-dihydroxybenzaldehyde were added to anhydrous ethanol and refluxed at 75°C for 6 hours. After the reaction was completed, the silica was cooled, filtered under reduced pressure, washed, and dried to obtain antibacterial silica. The mass ratio of modified silver-loaded silica to 2,3-dihydroxybenzaldehyde was 1:0.11.

[0061] Step S6: Mix 55g polyethylene glycol and 12g pyrogallol, stir well, then add 6g antibacterial silica, 1.7g distilled water, 0.7g triethylenediamine and 0.6g silicone oil. Heat and stir at 60℃ for 15min, then let stand to obtain a mixture. Add 40g 2,6-toluene diisocyanate to the mixture, stir well, transfer to a mold, and cure at 70℃ for 10h to obtain the finished product.

[0062] Comparative Example 2: The polyhydroxy chitosan and polyhydroxy pyrogallol were removed, and the rest was the same as in Example 1. The specific steps are as follows: Step S1: The nano-silica microspheres were added to deionized water and ultrasonically dispersed evenly. Then, 0.018 g / mL of silver nitrate solution was added until the solution changed from light color to dark color. The mixture was stirred at 45°C for 3.5 h. After stirring, the mixture was cooled, centrifuged, washed with water, and dried to obtain silver-loaded silica. The mass ratio of nano-silica microspheres to silver nitrate was 20:1.1.

[0063] Step S2: Add γ-aminopropyltriethoxysilane to a mixed solvent of ethanol and deionized water, stir until homogeneous, adjust the pH to 4.5, then add silver-loaded silica, ultrasonically disperse for 40 min, heat to 75℃ and stir for 10 h. After stirring, filter, wash and dry to obtain modified silver-loaded silica; the mass ratio of γ-aminopropyltriethoxysilane to silver-loaded silica is 1:12.

[0064] Step S3: Modified silver-loaded silica and 2,3-dihydroxybenzaldehyde were added to anhydrous ethanol and refluxed at 75°C for 6 hours. After the reaction was completed, the silica was cooled, filtered under reduced pressure, washed, and dried to obtain antibacterial silica. The mass ratio of modified silver-loaded silica to 2,3-dihydroxybenzaldehyde was 1:0.11.

[0065] Step S4: Mix 55g polyethylene glycol, 6g antibacterial silica, 1.7g distilled water, 0.7g triethylenediamine, and 0.6g silicone oil evenly, heat and stir at 60℃ for 15min, and let stand to obtain a mixture; then add 40g 2,6-toluene diisocyanate to the mixture, stir evenly, transfer to a mold, and mature at 70℃ for 10h to obtain the finished product.

[0066] Comparative Example 3: The polyhydroxy chitosan, polyhydroxy pyrogallol, and antibacterial silica were removed, and the rest were the same as in Example 1. The specific steps are as follows: Step S1: 55g polyethylene glycol, 1.7g distilled water, 0.7g triethylenediamine, and 0.6g silicone oil were mixed evenly, heated and stirred at 60°C for 15min, and allowed to stand to obtain a mixed solution; then 40g 2,6-toluene diisocyanate was added to the mixed solution, stirred evenly, transferred to a mold, and cured at 70°C for 10h to obtain the finished product.

[0067] Testing and experimentation:

[0068] Antibacterial rate test: Escherichia coli was selected as the test strain, and the concentration was diluted to obtain 2×10⁻⁶. 6 CFU / mL Escherichia coli bacterial suspension. Finished polyurethane foam dressings were cut into 2×2cm samples. E. coli bacterial suspension was dropped onto the sample surface and incubated at 37℃ for 20 hours. The samples were then serially diluted with PBS solution, and the diluted solutions were spread onto the surface of solid culture medium. After incubation at 37℃ for 20 hours, the colony count was recorded. A blank control group was also included, and colony counts were recorded. The antibacterial rate was calculated by substituting the data from both groups into the formula.

[0069] Animal surface experiment: Thirty male mice were divided into 6 groups. After anesthesia with isoflurane, the hair on their backs was removed, and wound surfaces were created. The pre-prepared polyurethane foam dressings prepared in the examples and comparative examples were placed on the wound surfaces sequentially. Filter paper was gently used to absorb the blood until no more seepage occurred. The surface condition of the wound was observed, and the dressings were changed daily. The surface condition of the wound was recorded on days 1 and 3. The results are shown in the table below:

[0070]

[0071] Conclusion: In Examples 1-3, the dosage remained unchanged, with only some reaction parameters modified. Experimental data showed no significant fluctuations in the performance of the samples.

[0072] Comparative Example 1: The polyhydroxy chitosan was removed, and the rest was the same as in Example 1. The experimental data showed that the antibacterial rate was reduced to 90.3% compared with Example 1. The wound showed mild inflammation on the first day and was basically healed on the third day with no redness or swelling. The reason for this is that the Schiff base structure and chitosan structure in the polyhydroxy chitosan can effectively resist bacterial growth. Therefore, removing it reduced the antibacterial effect, lowered the antibacterial rate, and caused mild inflammation of the wound.

[0073] Comparative Example 2: The polyhydroxy chitosan and polyhydroxy pyrogallol were removed, while the rest were the same as in Example 1. The experimental data showed that the antibacterial rate was reduced to 82.4% compared with Example 1. The wound condition was moderate inflammation after the first day, and the wound condition was roughly healed after the third day, with redness and swelling. The reason for this was that, based on Comparative Example 1, Comparative Example 2 further removed polyhydroxy pyrogallol. Polyhydroxy pyrogallol can effectively kill bacteria and reduce inflammation. Therefore, after removing it, the antibacterial rate was reduced and the wound condition showed moderate inflammation.

[0074] Comparative Example 3: The polyhydroxy chitosan, polyhydroxy pyrogallol, and antibacterial silica were removed, while the rest remained the same as in Example 1. Experimental data showed that the antibacterial rate decreased to 75.4% compared to Example 1. The wound showed moderate inflammation on day 1 and was largely healed with some redness and swelling on day 3. The reason for this was that, based on Comparative Example 2, Comparative Example 3 further removed the antibacterial silica. Antibacterial silica has a nano-silver bactericidal structure and a Schiff base structure, which can effectively resist bacterial growth. Therefore, removing it reduced the antibacterial effect, lowered the antibacterial rate, and resulted in moderate inflammation of the wound.

[0075] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process method article or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process method article or apparatus.

[0076] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a polyurethane foam dressing, characterized in that: Includes the following steps: Polyethylene glycol, polyhydroxy chitosan, and polyhydroxy pyrogallol are mixed and stirred evenly. Then, antibacterial silica, a foaming agent, a catalyst, and a surfactant are added. The mixture is heated, stirred, and allowed to stand to obtain a liquid mixture. 2,6-Toluene diisocyanate is then added to the liquid mixture, stirred evenly, transferred to a mold, and cured to obtain the finished product. The composition, by weight, is 50-60 parts polyethylene glycol, 10-15 parts polyhydroxy chitosan, 10-15 parts polyhydroxy pyrogallol, 5-7 parts antibacterial silica, 1.5-2.0 parts foaming agent, 0.6-0.8 parts catalyst, 0.5-0.7 parts surfactant, and 35-45 parts 2,6-Toluene diisocyanate. The foaming agent is distilled water, the catalyst is triethylenediamine, and the surfactant is silicone oil. Polyhydroxy chitosan was obtained by adding thioglycerol to modify the modified chitosan; polyhydroxy pyrogallol was obtained by adding thioglycerol to modify the modified pyrogallol; antibacterial silica was obtained by modifying silver-loaded silica with Schiff base.

2. The method for preparing a polyurethane foam dressing according to claim 1, characterized in that: Heat and stir at 50-60℃ for 10-15 minutes; then mature at 60-70℃ for 8-10 hours.

3. The method for preparing a polyurethane foam dressing according to claim 1, characterized in that: The preparation process of polyhydroxy chitosan is as follows: Step S1: Mix carboxymethyl chitosan and deionized water, stir and dissolve at 60-65℃, then add trans-2-hexenal solution dropwise, cool to 45-50℃ and stir for 5-6 hours. After the reaction is completed, extract, filter, wash and dry to obtain modified chitosan. Step S2: Thioglycerol, modified chitosan, and photoinitiator 1173 are added to tetrahydrofuran, stirred evenly, and then irradiated with ultraviolet light for 15-20 minutes. After the reaction is completed, the mixture is washed, dried, and rotary evaporated to obtain polyhydroxy chitosan.

4. The method for preparing a polyurethane foam dressing according to claim 3, characterized in that: A trans-2-hexenal solution was added to anhydrous ethanol and stirred to obtain a trans-2-hexenal solution; wherein the reaction mass ratio of carboxymethyl chitosan to trans-2-hexenal was 1:(0.15-0.20); and the reaction mass ratio of thioglycerol, modified chitosan, and photoinitiator 1173 was (0.20-0.25):1:0.

02.

5. The method for preparing a polyurethane foam dressing according to claim 1, characterized in that: The preparation process of polyhydroxypyrogallol is as follows: Step S1: Add pyrogallol and N-hydroxymethylacrylamide to anhydrous ethanol, stir to dissolve, heat to 35-40℃, stir mechanically until uniform, add concentrated sulfuric acid dropwise, seal and react for 2-3 days after the addition is complete, add deionized water after the reaction is complete, stir and react for 3-4 hours, let stand for 1.0-1.5 days, then filter, wash, recrystallize and dry to obtain modified pyrogallol; Step S2: Thioglycerol, modified pyrogallol, and photoinitiator 1173 are added to tetrahydrofuran, stirred evenly, and then irradiated with ultraviolet light for 15-20 minutes. After the reaction is completed, the mixture is washed, dried, and rotary evaporated to obtain polyhydroxypyrogallol.

6. The method for preparing a polyurethane foam dressing according to claim 5, characterized in that: The reaction mass ratio of pyrogallol and N-hydroxymethylacrylamide is 1:(3.2-3.5); the reaction mass ratio of thioglycerol, modified pyrogallol, and photoinitiator 1173 is (0.8-1.0):1:0.

02.

7. The method for preparing a polyurethane foam dressing according to claim 1, characterized in that: The preparation process of antibacterial silica is as follows: Step S1: Add nano-silica microspheres to deionized water, disperse them evenly by ultrasonication, then add 0.018-0.020 g / mL of silver nitrate solution, stir and react at 40-45℃ for 2.5-3.5 h, and after stirring, cool, centrifuge, wash with water and dry to obtain silver-loaded silica; Step S2: Add γ-aminopropyltriethoxysilane to a mixed solvent of ethanol and deionized water, stir evenly, adjust the pH to 4.0-4.5, then add silver-loaded silica, ultrasonically disperse for 30-40 min, heat to 70-75℃ and stir for 8-10 h. After stirring, filter, wash and dry to obtain modified silver-loaded silica. Step S3: Add modified silver-loaded silica and 2,3-dihydroxybenzaldehyde to anhydrous ethanol and reflux at 70-75℃ for 4-6 hours. After the reaction is completed, cool, filter under reduced pressure, wash and dry to obtain antibacterial silica.

8. The method for preparing a polyurethane foam dressing according to claim 7, characterized in that: The mass ratio of nano-silica microspheres to silver nitrate is 20:(1.0-1.3); the mass ratio of γ-aminopropyltriethoxysilane to silver-loaded silica is 1:(10-15); and the mass ratio of modified silver-loaded silica to 2,3-dihydroxybenzaldehyde is 1:(0.10-0.13).

9. A polyurethane foam dressing, characterized in that, Prepared according to any one of claims 1-8.

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