A guanidine compound antibacterial agent and a preparation method thereof

Abstract

The application belongs to the technical field of antibacterial agents, and aims at the problem of easy loss of the antibacterial active ingredient PHMB in the prior art, and provides a guanidine compound antibacterial agent and a preparation method thereof.The guanidine compound antibacterial agent comprises a compound antibacterial active ingredient, a carrier matrix (chitosan) and a reinforcing material (silicon dioxide).In the preparation process, the zinc ion coordination stability is enhanced through methylation modification, the modified polyglycerol is covalently fixed with PHMB, and the structural stability is improved through a crosslinking network, the chitosan is coated and combined with silicon dioxide to enhance the mechanical properties and swelling resistance, PHMB destroys the bacterial cell membrane to create a penetration channel for the zinc ion ligand, the zinc ion inhibits DNA replication, and the methylated gallic acid blocks energy metabolism, so that the high-efficiency and long-acting antibacterial effect is achieved in cooperation.

Description

Technical Field

[0001] This application relates to the field of antibacterial agent technology, specifically to a guanidine-based composite antibacterial agent and its preparation method. Background Technology

[0002] Antimicrobial agents are functional substances that can inhibit or kill microorganisms. Their core function is to reduce the harm of microorganisms to human health, production, daily life, or the material environment by intervening in the growth, reproduction, or metabolic processes of microorganisms. Antimicrobial agents include natural antimicrobial agents extracted from plants, animals, or microorganisms, such as plant essential oils, microbial metabolites, and animal-derived components. These have good biocompatibility and high safety, but their efficacy may be weak and their stability poor. Biological antimicrobial agents are based on the metabolic products of microorganisms themselves; a typical example is antibiotics, which mainly target bacteria and are mostly used in the medical field. However, they easily lead to drug-resistant bacteria, and their application requires strict control. Chemically synthesized antimicrobial agents are artificially synthesized compounds. These antimicrobial agents are highly effective and stable, and are currently the most widely used category. Among them, polyhexamethylene biguanide (PHMB) is a low-toxicity, broad-spectrum cationic antimicrobial agent that has been widely used in the food industry and plastics, but PHMB has disadvantages such as high water solubility and easy loss, which limits its application. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this application provides a guanidine-based composite antibacterial agent and its preparation method. The guanidine-based composite antibacterial agent of this application comprises a composite antibacterial active ingredient, a carrier matrix (chitosan), and a reinforcing material (silica). The preparation process enhances zinc ion coordination stability through methylation modification, modifies polyglycerol to covalently fix PHMB and improves structural stability through a cross-linked network, and uses chitosan to coat silica to enhance mechanical properties and swelling resistance. PHMB disrupts the bacterial cell membrane, creating penetration channels for zinc ion ligands. Zinc ions inhibit DNA replication, and methylated gallic acid blocks energy metabolism, synergistically achieving highly efficient and long-lasting antibacterial effects.

[0004] To achieve the above objectives, this application adopts the following technical solution:

[0005] In a first aspect, this application provides a guanidine-based composite antibacterial agent, comprising a composite antibacterial active ingredient, a carrier matrix, and a reinforcing material. The composite antibacterial active ingredient comprises polyhexamethylene biguanide, hexamethylene diisocyanate, and a second intermediate solution. The second intermediate solution is obtained by reacting modified polyglycerol, a first intermediate solution, a sulfonic acid resin, and vitamin E. The first intermediate solution is obtained by reacting zinc sulfate heptahydrate, methylated gallic acid, and disodium ethylenediaminetetraacetate. The methylated gallic acid is obtained by reacting gallic acid, dimethyl carbonate, and anhydrous calcium carbonate. The carrier matrix is ​​chitosan, which is coated on the surface of the composite antibacterial active ingredient. The reinforcing material is silica, which is uniformly dispersed in the carrier matrix.

[0006] In one feasible implementation, the mass ratio of the carrier matrix, reinforcing material, and composite antibacterial active ingredient is (4.9-5.1):0.25:(4.8-5); the mass ratio of the modified polyglycerol, the first intermediate solution, the sulfonic acid resin, and vitamin E is (82-86):(45-50):(6.9-7.1):1; the mass ratio of the zinc sulfate heptahydrate, methyl gallic acid, and disodium ethylenediaminetetraacetate is 9:(3.27-4.9):0.5; the mass ratio of the gallic acid, dimethyl carbonate, and anhydrous calcium carbonate is (10.2-10.8):35:2; the particle size of the silica is 50±5 nm; and the sulfonic acid resin is 732 cation exchange resin.

[0007] Secondly, this application provides a method for preparing a guanidine-based complex antibacterial agent, comprising the following steps:

[0008] S1. Gallic acid, dimethyl carbonate, anhydrous calcium carbonate and ethanol are mixed and reacted to obtain methylated gallic acid; zinc sulfate heptahydrate is dissolved in phosphate buffer, and the methylated gallic acid and disodium ethylenediaminetetraacetate are added to react to obtain the first intermediate solution.

[0009] S2. Toluene and isocyanate are added to polyglycerol and reacted under a nitrogen atmosphere to obtain modified polyglycerol. The modified polyglycerol, the first intermediate solution and the sulfonic acid resin are mixed and the pH is adjusted to 5±0.1. After the reaction, the mixture is filtered and vitamin E is added to the filtrate and stirred evenly to obtain the second intermediate solution.

[0010] S3. Prepare a polyhexamethylene biguanide solution, mix the second intermediate solution with the polyhexamethylene biguanide solution, and obtain a reaction solution after the first reaction. Add hexamethylene diisocyanate to the reaction solution to carry out a second reaction, and spray dry to obtain a composite antibacterial active ingredient.

[0011] S4. Dissolve chitosan in acetic acid solution, add silica and the composite antibacterial active ingredient, sonicate, dry, and sieve to obtain the guanidine composite antibacterial agent.

[0012] In one feasible implementation, the mass ratio of dimethyl carbonate to ethanol is 35:40; the mass fraction of the polyhexamethylene biguanide solution is 20%; the temperature of the mixing reaction is 55-65℃, the reaction time is 3-4 hours, the pH is adjusted to 5±0.1 after the reaction, and the methylated gallic acid is obtained by filtration.

[0013] In the presence of anhydrous calcium carbonate (alkaline catalyst), the phenolic hydroxyl group of gallic acid undergoes a nucleophilic substitution reaction with the methyl group of dimethyl carbonate to form a methyl ether bond, thus achieving methylation modification of the benzene ring. After the reaction, the pH is adjusted to 5±0.1 to precipitate the methylated gallic acid. Methylation modification introduces steric hindrance to gallic acid, reducing subsequent competition for coordination with metal ions such as calcium and magnesium ions, and improving the coordination stability of zinc ions.

[0014] In one feasible implementation, the solid-liquid mass ratio of zinc sulfate heptahydrate to phosphate buffer is 9:(18-22), the pH of the phosphate buffer is 6.5, and the reaction time of the first intermediate solution is 40-60 min.

[0015] The zinc ions released from zinc sulfate heptahydrate form a five-membered ring chelate with the ortho-phenolic hydroxyl group of methyl gallic acid through a coordinate bond. Disodium ethylenediaminetetraacetate, as an auxiliary ligand, preferentially binds to free zinc ions, inhibiting the non-specific coordination of zinc ions with other groups (such as polyglycerol hydroxyl groups). The ligand formed between zinc ions and methyl gallic acid is one of the core antibacterial units, which not only retains the antibacterial activity of zinc ions, but also enhances antioxidant activity through the phenolic hydroxyl group of gallic acid.

[0016] In one feasible implementation, the mass ratio of polyglycerol, toluene, and isocyanate is (45-50):30:(10-12), the isocyanate is added at 40-50°C, and the reaction time under nitrogen atmosphere is 3-5 hours.

[0017] The hydroxyl groups of polyglycerol undergo an addition reaction with the -NCO groups of isocyanate to form urethane bonds (-O-CO-NH-), introducing active -NCO groups onto the polyglycerol backbone. This provides reaction sites for subsequent covalent coupling with polyhexamethylene biguanide (PHMB), thus achieving stable fixation of PHMB.

[0018] In one feasible implementation, the reaction time of the modified polyglycerol, the first intermediate solution, and the sulfonic acid resin mixture is 1.5 to 2.5 hours.

[0019] The hydroxyl groups of modified polyglycerol and the carboxyl groups of methyl gallic acid undergo esterification under the action of sulfonic acid resin (732 cation exchange resin, acidic catalyst) to form ester bonds. The esterification reaction grafts zinc ions and ligands of methyl gallic acid onto the polyglycerol backbone to form a unified polymer carrier structure. After filtration to remove the resin, the phenolic hydroxyl groups of vitamin E combine with free radicals in the system to inhibit the oxidative deactivation of the phenolic hydroxyl groups of gallic acid, exert an antioxidant effect, and prolong the shelf life of the antibacterial agent.

[0020] In one feasible implementation, the mass ratio of the second intermediate solution to the polyhexamethylene biguanide solution is (2.8-3):1, and the amount of hexamethylene diisocyanate used is 1.8% to 2.2% of the mass of the reaction solution.

[0021] The -NCO group of modified polyglycerol undergoes an addition reaction with the guanidinium group of PHMB to form a urea bond (-NH-CO-NH-), achieving covalent coupling with the carrier backbone. The added hexamethylene diisocyanate (crosslinking agent) reacts with the remaining -NCO group of modified polyglycerol and the guanidinium group of PHMB through the -NCO group to form a three-dimensional crosslinked network structure, further enhancing the structural stability of the carrier and improving its resistance to hydrolysis under extreme environments (such as acidity). Spray drying (50°C inlet air) evaporates moisture through hot air to obtain a powdered composite antibacterial active ingredient, which is convenient for subsequent mixing and coating with the carrier matrix. Covalent coupling (urea bond) can significantly reduce the loss rate of PHMB and solve its easy diffusion problem.

[0022] In one feasible implementation scenario, the first reaction conditions are 40-45°C for 0.5-1.5 hours; the second reaction time is 20-40 minutes.

[0023] In one feasible implementation, the solid-liquid mass ratio of the chitosan to the acetic acid solution is (0.9-1.1):20, the concentration of the acetic acid solution is 0.8%~1.2%, and the ultrasonication time is 15~30 min.

[0024] In acetic acid solution (acidic environment), the amino group (-NH2) of chitosan is protonated to form -NH3⁺, enhancing water solubility and forming a viscous solution. Added silica (50±5nm) is uniformly dispersed in the chitosan solution, and agglomeration is broken up by ultrasound. After the composite antibacterial active ingredient is mixed with the chitosan solution, chitosan coats the surface of the active ingredient through hydrogen bonds and electrostatic interactions, forming a coating layer after drying. Chitosan, as a carrier matrix, provides good biocompatibility and membrane barrier function, reducing the toxicity of the antibacterial ingredient to normal cells. Silica, as a reinforcing material, improves the mechanical strength and swelling resistance of the coating layer, enhancing the stability of the antibacterial agent in humid environments.

[0025] Beneficial technical effects:

[0026] The guanidine composite antibacterial agent prepared in this application introduces polyhexamethylene biguanide into the composite antibacterial active ingredient. Its cationic guanidine group interacts electrostatically with the anionic phospholipids of the bacterial cell membrane, thereby disrupting the cell membrane structure and creating a channel for the complex formed by methylated gallic acid and zinc ions. The free zinc ions inhibit bacterial DNA polymerase, while the phenolic hydroxyl group of methylated gallic acid inhibits pyruvate kinase, thus blocking energy metabolism. On the other hand, the modified polyglycerol, with its -NCO group introduced via isocyanate, forms a urea bond with the guanidine group of PHMB to achieve fixation. The cross-linked network formed by isocyanate further reduces PHMB loss, while the phenolic hydroxyl groups of methylated gallic acid synergistically scavenge free radicals with vitamin E to prevent PHMB oxidative inactivation. In addition, by adding chitosan, protonated amino groups are coated with active ingredients and biocompatibility is provided. Silica is uniformly dispersed in the coating to enhance the mechanical strength and swelling resistance of the coating layer and reduce the loss of active ingredients caused by swelling. The synergistic cooperation of the components enables the antibacterial agent to achieve an antibacterial rate of over 99.5% against Escherichia coli and Staphylococcus aureus, and retains over 95% after swelling. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the preparation method of the guanidine-based compound antibacterial agent of this application. Detailed Implementation

[0028] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the application will be further described in detail below with reference to embodiments. However, this should not be construed as limiting the scope of this application to the following examples. All other embodiments obtained by those skilled in the art without creative effort without departing from the above-described methodological spirit of this application are within the scope of protection of this application.

[0029] In this application, the terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0030] The singular forms “for,” “or,” “a,” “any,” and “the” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] The following will describe in detail, with reference to different embodiments, a guanidine-based composite antibacterial agent and its preparation method provided in this application.

[0033] Example 1

[0034] like Figure 1As shown, a method for preparing a guanidine-based compound antibacterial agent includes the following steps:

[0035] 1. Gallic acid, dimethyl carbonate, anhydrous calcium carbonate and ethanol were mixed in a mass ratio of 10.5:35:2:40 and reacted at 60℃ for 3.5 h. After the reaction was completed, the pH of the reaction system was adjusted to 5±0.1, filtered, washed and dried to obtain methylated gallic acid.

[0036] 2. Zinc sulfate heptahydrate was dissolved in phosphate buffer at pH 6.5 at a solid-liquid mass ratio of 9:20. Methylated gallic acid and disodium ethylenediaminetetraacetate were added, and the reaction was carried out for 50 min to obtain the first intermediate solution. The mass ratio of zinc sulfate heptahydrate, methylated gallic acid and disodium ethylenediaminetetraacetate was 9:3.85:0.5.

[0037] 3. Dissolve polyglycerol in toluene, add isocyanate dropwise at 45°C. The mass ratio of polyglycerol, toluene and isocyanate is 48:30:11. After the addition is complete, react under nitrogen protection for 4 hours. Remove the solvent by rotary evaporation to obtain modified polyglycerol.

[0038] 4. Mix modified polyglycerol, the first intermediate solution, and 732 cation exchange resin, adjust the pH to 5±0.1, react for 2 hours, filter, add vitamin E to the filtrate and stir well to obtain the second intermediate solution; the mass ratio of modified polyglycerol, the first intermediate solution, 732 cation exchange resin, and vitamin E is 84:48:7:1; mix the second intermediate solution with polyhexamethylene biguanide solution (mass fraction of 20%) at a mass ratio of 2.9:1, react at 40℃ for 1 hour to obtain a reaction solution, add 2% hexamethylene diisocyanate by mass of the reaction solution and react for 30 minutes, spray dry (air inlet 50℃) to obtain the composite antibacterial active ingredient;

[0039] 5. Chitosan was dissolved in 1% acetic acid solution at a solid-liquid mass ratio of 1:20. Silica (particle size 50±5nm) and composite antibacterial active ingredients were added. The mixture was sonicated for 20 minutes. The mass ratio of chitosan, silica and composite antibacterial active ingredients was 5:0.25:4.9. After drying, the mixture was passed through an 80-mesh sieve to obtain a guanidine composite antibacterial agent.

[0040] Example 2

[0041] like Figure 1 As shown, a method for preparing a guanidine-based compound antibacterial agent includes the following steps:

[0042] 1. Gallic acid, dimethyl carbonate, anhydrous calcium carbonate and ethanol were mixed in a mass ratio of 10.2:35:2:40 and reacted at 55°C for 4 hours. After the reaction was completed, the pH of the reaction system was adjusted to 5±0.1, filtered, washed and dried to obtain methylated gallic acid.

[0043] 2. Zinc sulfate heptahydrate was dissolved in phosphate buffer at pH 6.5 at a solid-liquid mass ratio of 9:18. Methylated gallic acid and disodium ethylenediaminetetraacetate were added, and the reaction was carried out for 40 min to obtain the first intermediate solution. The mass ratio of zinc sulfate heptahydrate, methylated gallic acid and disodium ethylenediaminetetraacetate was 9:3.27:0.5.

[0044] 3. Dissolve polyglycerol in toluene, add isocyanate dropwise at 40°C. The mass ratio of polyglycerol, toluene and isocyanate is 45:30:12. After the addition is complete, react under nitrogen protection for 5 hours. Remove the solvent by rotary evaporation to obtain modified polyglycerol.

[0045] 4. Mix modified polyglycerol, the first intermediate solution, and 732 cation exchange resin, adjust the pH to 5±0.1, react for 1.5 h, filter, add vitamin E to the filtrate and stir evenly to obtain the second intermediate solution; the mass ratio of modified polyglycerol, the first intermediate solution, 732 cation exchange resin, and vitamin E is 82:50:6.9:1; mix the second intermediate solution with polyhexamethylene biguanide solution (mass fraction of 20%) at a mass ratio of 2.8:1, react at 45℃ for 0.5 h to obtain the reaction solution, add 1.8% hexamethylene diisocyanate by mass of the reaction solution and react for 40 min, spray dry (air inlet 50℃) to obtain the composite antibacterial active ingredient;

[0046] 5. Chitosan was dissolved in 0.8% acetic acid solution at a solid-liquid mass ratio of 0.9:20. Silica (particle size 50±5nm) and composite antibacterial active ingredients were added. The mixture was sonicated for 15 minutes. The mass ratio of chitosan, silica and composite antibacterial active ingredients was 4.9:0.25:5. After drying, the mixture was passed through an 80-mesh sieve to obtain a guanidine composite antibacterial agent.

[0047] Example 3

[0048] like Figure 1 As shown, a method for preparing a guanidine-based compound antibacterial agent includes the following steps:

[0049] 1. Gallic acid, dimethyl carbonate, anhydrous calcium carbonate and ethanol were mixed in a mass ratio of 10.8:35:2:40 and reacted at 65°C for 3 hours. After the reaction was completed, the pH of the reaction system was adjusted to 5±0.1, filtered, washed and dried to obtain methylated gallic acid.

[0050] 2. Zinc sulfate heptahydrate was dissolved in phosphate buffer at pH 6.5 at a solid-liquid mass ratio of 9:22. Methylated gallic acid and disodium ethylenediaminetetraacetate were added, and the reaction was carried out for 60 min to obtain the first intermediate solution. The mass ratio of zinc sulfate heptahydrate, methylated gallic acid and disodium ethylenediaminetetraacetate was 9:4.9:0.5.

[0051] 3. Dissolve polyglycerol in toluene, add isocyanate dropwise at 50°C. The mass ratio of polyglycerol, toluene and isocyanate is 50:30:10. After the addition is complete, react under nitrogen protection for 3 hours. Remove the solvent by rotary evaporation to obtain modified polyglycerol.

[0052] 4. Mix modified polyglycerol, the first intermediate solution, and 732 cation exchange resin, adjust the pH to 5±0.1, react for 2.5 h, filter, add vitamin E to the filtrate and stir evenly to obtain the second intermediate solution; the mass ratio of modified polyglycerol, the first intermediate solution, 732 cation exchange resin, and vitamin E is 86:45:7.1:1; mix the second intermediate solution with polyhexamethylene biguanide solution (mass fraction of 20%) at a mass ratio of 3:1, react at 45℃ for 1.5 h to obtain the reaction solution, add 2.2% hexamethylene diisocyanate by mass of the reaction solution and react for 2 min, spray dry (air inlet 50℃) to obtain the composite antibacterial active ingredient;

[0053] 5. Chitosan was dissolved in 1.2% acetic acid solution at a solid-liquid mass ratio of 1.1:20. Silica (particle size 50±5nm) and composite antibacterial active ingredients were added. The mixture was sonicated for 30 minutes. The mass ratio of chitosan, silica and composite antibacterial active ingredients was 5.1:0.25:4.8. After drying, the mixture was passed through an 80-mesh sieve to obtain a guanidine composite antibacterial agent.

[0054] Comparative Example 1

[0055] A method for preparing a guanidine complex antibacterial agent is implemented with the same steps and parameters as in Example 1, except that gallic acid is not methylated, and gallic acid is used directly instead of methylated gallic acid.

[0056] Comparative Example 2

[0057] A method for preparing a guanidine-based compound antibacterial agent, with the same steps and parameters as in Example 1, except that zinc sulfate heptahydrate is not added.

[0058] Comparative Example 3

[0059] A method for preparing a guanidine-based composite antibacterial agent, the implementation steps and parameters are the same as in Example 1, the difference being that isocyanate is not added.

[0060] Comparative Example 4

[0061] A method for preparing a guanidine-based composite antibacterial agent is provided, with the same steps and parameters as in Example 1, except that silica is not added.

[0062] Performance testing:

[0063] The performance of the guanidine composite antibacterial agents prepared in Examples 1-3 and Comparative Examples 1-4 of this application was tested. The test items and methods are as follows:

[0064] 1. Antibacterial performance test:

[0065] Using the suspension method (shaking flask method, suspension test), Escherichia coli and Staphylococcus aureus were selected to prepare 10 μL of each. 6 CFU / mL bacterial suspension; 10 μg / mL of the guanidine complex antibacterial agent prepared in the examples and comparative examples of this application was added to the bacterial suspension as the experimental group, and the experiment without antibacterial agent was set as the control group; shake culture at 37℃ for 24 h, after the reaction, samples were taken, serially diluted with physiological saline, and plated for 48 h;

[0066] Count the number of viable bacteria; Antibacterial rate (%) = (number of viable bacteria in the control group - number of viable bacteria in the experimental group) / number of viable bacteria in the control group × 100%, the results are shown in Table 1.

[0067] 2. Anti-swelling stability test:

[0068] Take 0.5g of the guanidine composite antibacterial agent sample prepared in this application, soak it in 10mL of physiological saline (37℃), take it out after 72h, absorb the surface moisture and weigh it, and calculate the swelling rate: swelling rate = (mass after soaking - initial mass) / initial mass × 100%. Test the antibacterial rate of the swollen guanidine composite antibacterial agent against Escherichia coli and Staphylococcus aureus. The results are shown in Table 1.

[0069] Table 1. Performance test results of guanidine composite antibacterial agents prepared in the examples and comparative examples.

[0070]

[0071] As shown in Table 1, the guanidine composite antibacterial agents prepared in Examples 1-3 of this application have antibacterial rates of 99.6%~99.8% and 99.5%~99.7% against Escherichia coli and Staphylococcus aureus, respectively. After swelling, the antibacterial rates are 95.8%~96.5% and 95.5%~96.2%, respectively, and the swelling rate is 17.8%~19.5%.

[0072] Comparative Example 1, without methylation of gallic acid, directly used gallic acid to prepare a guanidine-based antibacterial agent with antibacterial rates of 92.3% and 91.5% against *Escherichia coli* and *Staphylococcus aureus*, respectively. After swelling, the antibacterial rates were 87.6% and 86.8%, respectively, with a swelling rate of 24.6%. When gallic acid is unmethylated, its phenolic hydroxyl groups lack steric hindrance protection, making it prone to competing for coordination with calcium or magnesium ions (common in physiological environments). This leads to decreased coordination stability between zinc ions and gallic acid, and the reduction in free zinc ions directly weakens its inhibitory effect on bacterial DNA polymerase. Simultaneously, the unmethylated phenolic hydroxyl groups of gallic acid are more easily oxidized, weakening the antioxidant synergistic effect and causing the antibacterial active ingredient to be easily inactivated. Furthermore, insufficient coordination stability makes the antibacterial agent more prone to loss during swelling, further reducing the antibacterial rate after swelling.

[0073] Comparative Example 2, without the addition of zinc sulfate heptahydrate, prepared a guanidine complex antibacterial agent with antibacterial rates of 75.2% and 73.8% against *Escherichia coli* and *Staphylococcus aureus*, respectively. After swelling, the antibacterial rates were 68.5% and 67.2%, respectively, significantly lower than the example. The swelling rate was 20.3%, close to that of the example. The lack of zinc sulfate heptahydrate means there is no source of zinc ions, preventing the formation of antibacterial ligands between zinc ions and methylated gallic acid. This loss of zinc ions results in the inability to inhibit bacterial DNA polymerase. Furthermore, after PHMB disrupts the cell membrane, no zinc ions penetrate into the cell to block DNA replication, thus losing the synergistic effect of zinc ions and PHMB.

[0074] Comparative Example 3, without the addition of isocyanate, prepared a guanidine-based composite antibacterial agent with antibacterial rates of 82.5% and 81.2% against *Escherichia coli* and *Staphylococcus aureus*, respectively. After swelling, the antibacterial rates were 72.3% and 71.0%, respectively, significantly lower than in the previous example. Without isocyanate, polyglycerol cannot form a carbamate bond through the addition reaction of hydroxyl groups with -NCO groups, and therefore cannot subsequently form a urea bond with the guanidine group of PHMB to achieve covalent coupling. In this case, PHMB is only physically dispersed in the system and is not stably fixed. During storage and swelling, it is easily lost in large quantities due to its high water solubility, leading to a decrease in the content of antibacterial active ingredients. Simultaneously, due to the lack of a polymeric carrier structure provided by modified polyglycerol, the Zn in the first intermediate solution... 2+ The methylated gallic acid ligand cannot be grafted onto the polyglycerol backbone via esterification, making it prone to aggregation, reducing the contact area with bacteria, and weakening its inhibitory effect on DNA polymerase and metabolic enzymes. Furthermore, the lack of cross-linking sites formed by isocyanate modification makes it difficult for subsequently added hexamethylene diisocyanate to construct a three-dimensional cross-linked network, resulting in decreased structural stability and increased structural loosening during swelling. This further exacerbates the loss of antibacterial components, and multiple factors combined lead to a significant decrease in antibacterial rate.

[0075] Comparative Example 4, without the addition of silica, prepared a guanidine composite antibacterial agent with initial antibacterial rates against *Escherichia coli* and *Staphylococcus aureus* similar to the examples. However, after swelling, the antibacterial rates were 83.5% and 82.8%, respectively, a significant decrease, while the swelling rate increased dramatically to 38.6%. Silica, as a reinforcing material, can form a rigid support and porous structure in the chitosan coating layer. Without silica, the mechanical strength of the chitosan coating layer decreases, and structural collapse easily occurs during swelling in physiological saline, leading to a significant loss of the composite antibacterial active ingredients. The initial antibacterial rate was similar because the active ingredients were not lost, but after swelling, the antibacterial rate decreased significantly due to component loss and the failure of the coating layer's barrier function.

[0076] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0077] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. A guanidine-based compound antibacterial agent, characterized in that, The product comprises a composite antibacterial active ingredient, a carrier matrix, and a reinforcing material. The composite antibacterial active ingredient includes polyhexamethylene biguanide, hexamethylene diisocyanate, and a second intermediate solution. The second intermediate solution is obtained by reacting modified polyglycerol, a first intermediate solution, a sulfonic acid resin, and vitamin E. The first intermediate solution is obtained by reacting zinc sulfate heptahydrate, methylated gallic acid, and disodium ethylenediaminetetraacetate. The methylated gallic acid is obtained by reacting gallic acid, dimethyl carbonate, and anhydrous calcium carbonate. The carrier matrix is ​​chitosan, which coats the surface of the composite antibacterial active ingredient. The reinforcing material is silica, which is uniformly dispersed in the carrier matrix. The modified polyglycerol is obtained by adding toluene and isocyanate to polyglycerol and reacting under a nitrogen atmosphere. The composite antibacterial active ingredient is obtained by preparing a polyhexamethylene biguanide solution, mixing the second intermediate solution with the polyhexamethylene biguanide solution, performing a first reaction to obtain a reaction solution, adding hexamethylene diisocyanate to the reaction solution for a second reaction, and spray drying.

2. The guanidine compound antibacterial agent according to claim 1, characterized in that, The mass ratio of the carrier matrix, reinforcing material, and composite antibacterial active ingredient is (4.9-5.1):0.25:(4.8-5); the mass ratio of the modified polyglycerol, the first intermediate solution, the sulfonic acid resin, and vitamin E is (82-86):(45-50):(6.9-7.1):1; the mass ratio of the zinc sulfate heptahydrate, methylated gallic acid, and disodium ethylenediaminetetraacetate is 9:(3.27-4.9):0.5; the mass ratio of the gallic acid, dimethyl carbonate, and anhydrous calcium carbonate is (10.2-10.8):35:2; the particle size of the silica is 50±5 nm; and the sulfonic acid resin is 732 cation exchange resin.

3. A method for preparing a guanidine-based complex antibacterial agent as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Gallic acid, dimethyl carbonate, anhydrous calcium carbonate and ethanol are mixed and reacted to obtain methylated gallic acid; zinc sulfate heptahydrate is dissolved in phosphate buffer, methylated gallic acid and disodium ethylenediaminetetraacetate are added, and the reaction is carried out to obtain the first intermediate solution. S2. Toluene and isocyanate are added to polyglycerol and reacted under a nitrogen atmosphere to obtain modified polyglycerol. The modified polyglycerol, the first intermediate solution and the sulfonic acid resin are mixed and the pH is adjusted to 5±0.

1. After the reaction, the mixture is filtered and vitamin E is added to the filtrate and stirred evenly to obtain the second intermediate solution. S3. Prepare a polyhexamethylene biguanide solution, mix the second intermediate solution with the polyhexamethylene biguanide solution, and obtain a reaction solution after the first reaction. Add hexamethylene diisocyanate to the reaction solution to carry out the second reaction, and spray dry to obtain a composite antibacterial active ingredient. S4. Dissolve chitosan in acetic acid solution, add silica and composite antibacterial active ingredients, sonicate, dry, and sieve to obtain guanidine composite antibacterial agent.

4. The method for preparing a guanidine-based composite antibacterial agent according to claim 3, characterized in that, The mass ratio of dimethyl carbonate to ethanol is 35:40; the mass fraction of the polyhexamethylene biguanide solution is 20%; the temperature of the mixing reaction is 55-65℃, the reaction time is 3-4h, the pH is adjusted to 5±0.1 after the reaction, and the methylated gallic acid is obtained by filtration.

5. The method for preparing a guanidine-based composite antibacterial agent according to claim 3, characterized in that, The solid-liquid mass ratio of zinc sulfate heptahydrate to phosphate buffer is 9:(18-22), the pH of the phosphate buffer is 6.5, and the reaction time of the first intermediate solution is 40-60 min.

6. The method for preparing a guanidine-based composite antibacterial agent according to claim 3, characterized in that, The mass ratio of polyglycerol, toluene and isocyanate is (45-50):30:(10-12), the isocyanate is added at 40-50°C, and the reaction time under nitrogen atmosphere is 3-5 hours.

7. The method for preparing a guanidine-based composite antibacterial agent according to claim 3, characterized in that, The reaction time for the modified polyglycerol, the first intermediate solution, and the sulfonic acid resin mixture is 1.5 to 2.5 hours.

8. The method for preparing a guanidine-based composite antibacterial agent according to claim 3, characterized in that, The mass ratio of the second intermediate solution to the polyhexamethylene biguanide solution is (2.8-3):1, and the amount of hexamethylene diisocyanate used is 1.8% to 2.2% of the mass of the reaction solution.

9. The method for preparing a guanidine-based composite antibacterial agent according to claim 3, characterized in that, The first reaction condition is 40-45℃ for 0.5-1.5 h; the second reaction time is 20-40 min.

10. The method for preparing a guanidine-based composite antibacterial agent according to claim 3, characterized in that, The solid-liquid mass ratio of chitosan to the acetic acid solution is (0.9-1.1):20, the concentration of the acetic acid solution is 0.8%~1.2%, and the ultrasonication time is 15~30 min.

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