An antibacterial composite coating based on quaternized nano zinc oxide, its preparation method and application

Abstract

This invention discloses a method for preparing and applying an antibacterial composite coating based on quaternized zinc oxide nanoparticles. The preparation method includes: grafting quaternary ammonium salt compounds onto the surface of zinc oxide nanoparticles to prepare synergistic antibacterial nanoparticles; modifying the substrate surface by co-deposition of dopamine and polyethyleneimine to introduce active functional groups; and spraying or dipping the quaternized zinc oxide nanoparticles onto the modified substrate surface to obtain the antibacterial composite coating. This novel antibacterial material preparation scheme can integrate the advantages of zinc oxide nanoparticles and quaternary ammonium salts, while solving key technical problems such as nanoparticle aggregation, weak interfacial bonding, and limited antibacterial efficiency. It is of great significance for promoting the upgrading of hygiene and safety in the fields of medicine, food, and building materials.

Description

Technical Field

[0001] This invention belongs to the field of antibacterial materials technology, and relates to antibacterial composite coatings and their preparation methods, specifically to an antibacterial composite coating based on quaternized nano zinc oxide, its preparation method, and its application. Background Technology

[0002] With the increasingly severe global situation of bacterial contamination, bacterial infections have become a common challenge in many fields, seriously threatening human health. Especially in the post-pandemic era, public health awareness has generally increased, and hygiene and safety requirements in fields such as medicine, food, and the environment have become more stringent, significantly increasing the market demand for performance-enhancing antimicrobial functional materials. Recent studies have shown that with the emergence of bacterial resistance, single antimicrobial mechanisms are insufficient to cope with complex microbial environments, and the ecotoxicity of traditional antimicrobial agents has also attracted much attention.

[0003] Metal nanoparticles and their oxides have been extensively studied due to their excellent antibacterial properties. Among them, nano-zinc oxide has become a key research object in the field of antibacterial materials due to its advantages such as good biocompatibility, strong chemical stability, and low raw material cost. However, there are still three key problems in its practical industrial application: First, nanoparticles have a large specific surface area and high surface energy, making them prone to aggregation, resulting in insufficient exposure of antibacterial active sites and directly reducing antibacterial efficiency; second, in complex environments, the dispersibility and stability of nano-zinc oxide further decrease, and its antibacterial performance is easily inhibited, making it difficult to maintain long-term antibacterial effects; third, nano-zinc oxide has poor interfacial compatibility with polymer matrices, easily leading to uneven dispersion and weak bonding, resulting in a decline in the mechanical properties of the material and limiting its large-scale application in composite materials.

[0004] Quaternary ammonium salts are antibacterial organic compounds with contact activity. The positively charged quaternary ammonium ions in their molecules can effectively adsorb onto the negatively charged bacterial cell walls, thereby disrupting cell membrane integrity and achieving a bactericidal effect. However, when used alone, quaternary ammonium salts suffer from problems such as easy migration and loss, poor long-term antibacterial stability, and weak binding ability with inorganic particles or polymer matrices, making it difficult to balance high efficiency and durability.

[0005] In summary, existing antibacterial materials either cannot cope with drug-resistant bacteria and complex environments due to their single antibacterial mechanism, or their applications are limited by problems such as nanoparticle aggregation and poor interfacial compatibility, or the antibacterial agents themselves lack stability and safety to meet industry demands. Therefore, developing a novel antibacterial material preparation scheme that can integrate the advantages of nano-zinc oxide and quaternary ammonium salts while solving key technical problems such as nanoparticle aggregation, weak interfacial bonding, and limited antibacterial efficiency has become an urgent technological direction to be explored in the field of antibacterial materials, and is of great significance for promoting the upgrading of hygiene and safety in the medical, food, and building materials industries. Summary of the Invention

[0006] The purpose of this invention is to provide an antibacterial composite coating based on quaternized nano zinc oxide, its preparation method and application. By modifying the substrate surface with dopamine and polyethyleneimine deposition, the dispersibility and interfacial compatibility of nano zinc oxide in the polymer coating are improved, resulting in a composite coating with excellent antibacterial efficiency and strong stability. Moreover, the preparation process is mild and easy to scale up.

[0007] This invention is achieved through the following technical solution: A method for preparing an antibacterial composite coating based on quaternized nano zinc oxide includes the following steps: Step 1: Graft quaternary ammonium salt compounds onto the surface of nano-zinc oxide to prepare quaternized zinc oxide nano-particles with synergistic antibacterial properties. Step 2: Modify the substrate surface by co-deposition of dopamine and polyethyleneimine to introduce active functional groups; Step 3: Spray or dip-coat the modified substrate surface with quaternized nano zinc oxide to obtain an antibacterial composite coating.

[0008] Preferably, the method for grafting quaternary ammonium salt compounds onto the surface of nano-zinc oxide as described in step one includes the following steps: S1: Disperse 0.5~5 g of nano zinc oxide uniformly in 50~500 mL of solvent to prepare a nanoparticle dispersion; S2: Add 1~10 g of silane coupling agent containing quaternary ammonium functional groups to the dispersion, and stir continuously at 60~90 ℃ for 12~24 h. After the reaction is completed, centrifuge, wash with alcohol and dry to obtain quaternized zinc oxide nanoparticles.

[0009] Furthermore, the solvent mentioned in step S1 is a mixed solvent prepared by methanol and deionized water at a volume ratio of 1:4.

[0010] Furthermore, the silane coupling agent containing quaternary ammonium functional groups mentioned in step S2 includes any one of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, dimethylhexadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, dimethyltetradecyl[3-(trimethoxysilyl)propyl]ammonium chloride, and dimethyldodecyl[3-(trimethoxysilyl)propyl]ammonium chloride.

[0011] Preferably, the method for co-depositing and modifying the substrate surface with dopamine and polyethyleneimine in step two specifically includes the following steps: S1: The substrate is ultrasonically cleaned sequentially with methanol and acetone, and then dried in a forced-air oven; S2: Dissolve dopamine hydrochloride and polyethyleneimine in Tris-HCl buffer; wherein the mass ratio of dopamine hydrochloride and polyethyleneimine is 1:1, and the concentrations are 1~10 mg / mL, respectively. S3: Immerse the substrate completely in the above solution and keep it in the dark with a 100 rpm oscillation environment for 24 h; S4: Thoroughly clean with deionized water and dry to obtain the modified substrate.

[0012] Furthermore, the substrate mentioned in step two includes any one of metal, inorganic non-metallic materials, and polymer materials.

[0013] Preferably, the method for spraying or dipping quaternized nano zinc oxide onto the modified substrate surface as described in step three includes the following steps: S1: Prepare a quaternized zinc oxide nano-dispersion with a concentration of 0.1~10 mg / mL; S2: The dispersion is sprayed or dipped onto the modified substrate surface by spraying or dipping; the spraying pressure is 0.2~0.6 MPa, the distance between the spray gun and the substrate surface is 200~250 mm, and the spray gun moving speed is 300~500 mm / s. S3: Vacuum dry the coating at 60 ℃ for 5~12 h to obtain the antibacterial composite coating.

[0014] Furthermore, the solvent for the quaternized nano zinc oxide dispersion mentioned in step S1 includes any one of methanol, ethanol, isopropanol, acetone, and chloroform.

[0015] This invention also protects an antibacterial composite coating based on quaternized nano zinc oxide prepared by the method described above, and its application on substrate surfaces in the fields of medicine, food, building materials, and textiles.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention functionalizes the surface of nano zinc oxide through quaternization modification, combining a dual antibacterial strategy of "zinc ion release sterilization" and "quaternary ammonium salt contact sterilization". Compared with using nano zinc oxide or traditional quaternary ammonium salt alone, it has more efficient and broad-spectrum antibacterial activity and reduces the risk of bacterial resistance. Excellent antibacterial efficiency can be obtained with low addition amount, which reduces the material preparation cost and reduces the ecotoxicity that may be caused by excessive release of antibacterial components, thus balancing efficacy and safety. This invention utilizes dopamine and polyethyleneimine co-deposition to modify the substrate surface, forming a highly adhesive intermediate layer. Quaternized zinc oxide nanoparticles are then chemically bonded to achieve a tight bond between the substrate, co-deposited layer, and antibacterial agent. Regarding coating stability, the catechol groups of polydopamine and the amino groups of polyethyleneimine interact with various substrates, forming multiple interactions such as covalent bonds, hydrogen bonds, and coordination bonds, achieving universal strong adhesion. The quaternized zinc oxide nanoparticles further form ionic and covalent bonds with the amino and hydroxyl groups in the co-deposited layer, achieving "chemical anchoring" of the antibacterial agent. Simultaneously, quaternization modification not only endows the nano-zinc oxide with superior antibacterial activity but also improves its dispersibility and interfacial compatibility in polymer coatings, reducing nanoparticle aggregation and detachment. This results in a composite coating with strong stability, maintaining excellent antibacterial performance even under repeated cleaning, friction, or long-term use. In terms of biocompatibility, the quaternized zinc oxide nanoparticles are chemically bonded to the co-deposited network, achieving Zn... 2+ Slow and controllable release; the length and modification density of the quaternary ammonium chain can be adjusted, which can reduce toxicity to mammalian cells while ensuring antibacterial activity; The entire preparation process of this invention does not require high temperature or strong corrosive reagents. The preparation process conditions are mild and easy to scale up. It is compatible with a variety of substrates such as metals, polymers, and ceramics. By adjusting the carbon chain length of the selected quaternary ammonium salt, the concentration of nanoparticles, and the type of substrate, the macroscopic properties of the composite coating, such as hydrophilicity / hydrophobicity and mechanical properties, can be controlled, thereby meeting the diverse needs of different application scenarios such as medical, construction, and packaging. The coating of this invention has good biocompatibility. When applied to the surface of medical catheters made of polyurethane or silicone rubber, the effective antibacterial activity of quaternized nano zinc oxide can effectively inhibit bacterial colonization and biofilm formation. The structure formed by chemical bonding of the coating can meet the stability requirements for long-term use, and is expected to promote the development of next-generation antibacterial medical devices and implantable materials. The coating of this invention possesses properties such as hydrophobicity, strong adhesion, long-lasting antibacterial effect, and biosafety. Through co-deposition and chemical bonding technology, it can stably modify the surface of high-strength synthetic fibers such as polyester, nylon, and aramid, endowing the fibers with durable antibacterial properties and resistance to washing and mechanical friction. At the same time, its excellent cell compatibility effectively reduces the risk of sensitization. It can be applied to protective equipment in outdoor sportswear, special industrial workwear, and medical and food processing fields, thereby improving the functionality and hygiene safety of fabrics. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the interaction mechanism between quaternized nano zinc oxide (ZnO-Q) and polydopamine-polyethyleneimine (PDA-PEI) in this invention. Figure 2The following are the infrared (FTIR) spectra provided in Comparative Example 1 and Example 2 of this invention; Figure 3 (a) and (b) correspond to the static water contact angle photographs provided in Comparative Examples 1 and 2 of this invention. Figure 3 (c)~(d) are static water contact angle photographs provided in Embodiments 1~2 of the present invention; Figure 4 (a) and (b) correspond to the antibacterial test results provided in Comparative Examples 1 and 2 of the present invention. Figure 4 (c)~(e) are the antibacterial test results provided in Examples 1~3 of the present invention; Figure 5 The results of cytotoxicity tests provided for Comparative Example 1 and Example 2 of this invention. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0019] The nano zinc oxide used in the following examples has a particle size of 10~100 nm.

[0020] The molecular weight of the polyethyleneimine used in the following examples is 600-70000.

[0021] The substrate of this invention includes metals such as titanium alloys, stainless steel, iron, and cobalt-chromium alloys; inorganic non-metallic materials such as ceramics and glass; and polymeric materials such as silicone rubber, polyurethane, polyethersulfone, polyetheretherketone, polypropylene, polyethylene, polyester, nylon, and aramid.

[0022] Example 1: Step 1: Preparation of quaternized zinc oxide nanoparticles: 5 g of 30 nm zinc oxide nanoparticles were ultrasonically treated at 40 kHz and 200 W for 3 h and uniformly dispersed in a mixed solvent of deionized water (400 mL) and methanol (100 mL) to prepare a nanoparticle dispersion; 7 g of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride was added to the dispersion, and the mixture was stirred continuously at 70 °C for 24 h; after the reaction was completed, the modified zinc oxide nanoparticles were separated by centrifugation and washed three times with anhydrous ethanol to remove unreacted grafted silane coupling agent; the product was dried at 60 °C for 12 h to obtain quaternized zinc oxide nanoparticles; Step 2: Co-deposition modification of substrate surface with polydopamine and polyethyleneimine: Low-density polyethylene (PE) film was selected as the substrate. The PE was ultrasonically cleaned with methanol and acetone sequentially for 10 min, and then dried in a forced-air oven at 60 ℃ for 30 min. Dopamine hydrochloride and polyethyleneimine (… M w=70000) was dissolved in Tris-HCl buffer (10 mM, pH 8.5) at a concentration of 2 mg / mL; the PE film was completely immersed in the above solution and kept in the dark with shaking at 100 rpm for 24 h; it was thoroughly washed with deionized water and dried under vacuum at 60 ℃ for 8 h to obtain the modified substrate; Step 3: Spraying or dipping quaternized nano zinc oxide onto the substrate surface: Prepare a quaternized nano zinc oxide dispersion with a concentration of 0.1 mg / mL, immerse the modified substrate in the nanoparticle dispersion, let it stand for 12 h, and rinse the surface thoroughly with deionized water; dry the coating at 60 ℃ for 8 h to obtain an antibacterial composite coating.

[0023] Example 2: Step 1: Preparation of quaternized zinc oxide nanoparticles: 5 g of 30 nm zinc oxide nanoparticles were ultrasonically treated at 40 kHz and 200 W for 3 h and uniformly dispersed in a mixed solvent of deionized water (400 mL) and methanol (100 mL) to prepare a nanoparticle dispersion; 7 g of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride was added to the dispersion, and the mixture was stirred continuously at 70 °C for 24 h; after the reaction was completed, the modified zinc oxide nanoparticles were separated by centrifugation and washed three times with anhydrous ethanol to remove unreacted grafted silane coupling agent; the product was dried at 60 °C for 12 h to obtain quaternized zinc oxide nanoparticles; Step 2: Co-deposition modification of substrate surface with polydopamine and polyethyleneimine: Silicone rubber was selected as the substrate. The silicone rubber was ultrasonically cleaned with methanol and acetone sequentially for 10 min, and then dried in a forced-air oven for 30 min. Dopamine hydrochloride and polyethyleneimine (… M w =70000) was dissolved in Tris-HCl buffer (10 mM, pH 8.5) at a concentration of 2 mg / mL; the silicone rubber was completely immersed in the above solution and kept in the dark with shaking at 100 rpm for 24 h; it was thoroughly washed with deionized water and dried under vacuum at 60 ℃ for 8 h to obtain the modified substrate; Step 3: Spraying or dipping quaternized nano zinc oxide onto the substrate surface: Prepare a quaternized nano zinc oxide dispersion with a concentration of 1 mg / mL, immerse the modified substrate in the nanoparticle dispersion, let it stand for 12 h, and rinse the surface thoroughly with deionized water; dry the coating at 60 ℃ for 8 h to obtain an antibacterial composite coating.

[0024] Example 3: Step 1: Preparation of quaternized zinc oxide nanoparticles: 5 g of 30 nm zinc oxide nanoparticles were ultrasonically treated at 40 kHz and 200 W for 3 h and uniformly dispersed in a mixed solvent of deionized water (400 mL) and methanol (100 mL) to prepare a nanoparticle dispersion; 7 g of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride was added to the dispersion, and the mixture was stirred continuously at 70 °C for 24 h; after the reaction was completed, the modified zinc oxide nanoparticles were separated by centrifugation and washed three times with anhydrous ethanol to remove unreacted grafted silane coupling agent; the product was dried at 60 °C for 12 h to obtain quaternized zinc oxide nanoparticles; Step 2: Co-deposition and modification of substrate surface with polydopamine and polyethyleneimine: Nylon fiber was selected as the substrate. The nylon fiber was ultrasonically cleaned with methanol and acetone sequentially for 10 min, and then dried in a forced-air oven for 30 min. Dopamine hydrochloride and polyethyleneimine (…) were then co-deposited onto the substrate surface. M w =70000) was dissolved in Tris-HCl buffer (10 mM, pH 8.5) at a concentration of 2 mg / mL; the nylon fiber was completely immersed in the above solution and kept in the dark with shaking at 100 rpm for 24 h; it was thoroughly washed with deionized water and dried under vacuum at 60 °C for 8 h to obtain the modified substrate; Step 3: Spraying or dipping quaternized nano zinc oxide onto the substrate surface: Prepare a quaternized nano zinc oxide dispersion with a concentration of 10 mg / mL, immerse the modified substrate in the nanoparticle dispersion, let it stand for 12 h, and rinse the surface thoroughly with deionized water; dry the coating at 60 ℃ for 8 h to obtain an antibacterial composite coating.

[0025] Comparative Example 1: Preparation of unmodified substrates, including, Low-density polyethylene (PE) film was selected as the substrate. The PE was ultrasonically cleaned with methanol and acetone for 10 min in sequence, and then dried in a forced-air oven for 30 min to obtain an unmodified PE sample.

[0026] Comparative Example 2: Preparation of a composite coating based on unmodified nano-zinc oxide, including, Step 1: Co-deposition and modification of substrate surface with polydopamine and polyethyleneimine: Low-density polyethylene (PE) film was selected as the substrate. The PE was ultrasonically cleaned with methanol and acetone sequentially for 10 min, and then dried in a forced-air oven for 30 min. Dopamine hydrochloride and polyethyleneimine (…) were then co-deposited and modified on the substrate surface. M w=70000) was dissolved in Tris-HCl buffer (10 mM, pH 8.5) at a concentration of 2 mg / mL; the PE film was completely immersed in the above solution and kept in the dark with shaking at 100 rpm for 24 h; it was thoroughly washed with deionized water and vacuum dried at 60 ℃ for 8 h to obtain the modified substrate; Step 2: Spraying or dipping unmodified nano zinc oxide onto the substrate surface: Prepare a nano zinc oxide dispersion with a concentration of 1 mg / mL, immerse the modified substrate in the nanoparticle dispersion, let it stand for 12 h, and rinse the surface thoroughly with deionized water; dry the coating at 60 ℃ for 8 h to obtain an antibacterial composite coating.

[0027] like Figure 1 The diagram illustrates the interaction mechanism between quaternized nano-zinc oxide (ZnO-Q) and polydopamine-polyethyleneimine (PDA-PEI) in this invention. First, the PDA-PEI co-deposition forms a strong, stable, and functionally rich intermediate interface (-NH2, -OH, -NH-) between the inert substrate surface and the nanoparticles. Dopamine self-polymerizes in an alkaline environment, and its catechol groups are oxidized to quinone groups, endowing it with universal adhesion to various substrates. Simultaneously, the amino groups in polyethyleneimine (PEI) can undergo a Schiff-base reaction with the quinone groups of PDA, forming a more stable and dense cross-linked network, thereby significantly enhancing the coating's stability. Second, the PDA-PEI intermediate layer provides an ideal platform for the loading and fixation of ZnO-Q. PDA-PEI is rich in amino and phenolic hydroxyl groups. On the one hand, it can form hydrogen bonds with unreacted hydroxyl groups on the surface of nanoparticles. On the other hand, it can coordinate with zinc ions on the surface of nanoparticles to form stable metal-organic coordination bonds, thereby further enhancing the binding force between the two.

[0028] like Figure 2 The image shown is a Fourier Transform Infrared (FTIR) spectrum of Comparative Example 1 and Example 2 of this invention. It can be seen that the unmodified polyethylene (PE) sample at 2916 cm⁻¹... -1 and 2848 cm -1 The absorption peak at 1464 cm⁻¹ corresponds to the stretching vibration peak of CH. -1 and 719 cm -1 The peaks at these locations correspond to the scissor bending vibration peak and the in-plane rocking vibration absorption peak of CH, respectively, both characteristic peaks of PE. The spectrum corresponding to PE / PDA-PEI shows absorption peaks in the range of 3100 ~ 3600 cm⁻¹. -1 The corresponding peak becomes broader, which is due to the stretching vibration of the phenolic hydroxyl group in catechol, and at 1638 cm⁻¹ -1 The peak shape of the bending vibration of NH at 1287 cm⁻¹ changes.1 The presence of CO tensile vibrations indicates that PDA and PEI are loaded on the PE surface. After ZnO-Q is deposited on the surface, the FTIR spectrum of the coating does not change significantly. This is because the nanoparticles have less organic functional groups than the matrix PE / PDA-PEI, and cannot be clearly characterized by FTIR spectroscopy.

[0029] like Figure 3 Table 1 shows the static water contact angle test results of the sample surfaces in Comparative Examples 1, 2, and Examples 1-3 of this invention.

[0030] Table 1 Static water contact angles of samples from Comparative Example 1, Comparative Example 2, and Examples 1-3 It can be seen that the water contact angle of the unmodified PE surface (Comparative Example 1) is 102.9°. 0.3 After modification with nano-zinc oxide (ZnO) (Comparative Example 2), the water contact angle of the coating was 79.7°. 1.2 This is attributed to the presence of hydrophilic hydroxyl groups on the ZnO surface; after modification with different concentrations of quaternized nano-zinc oxide (ZnO-Q), the water contact angle of the coatings was significantly improved. The coatings prepared with ZnO-Q dispersions at concentrations of 0.1, 1, and 10 mg / mL (Examples 1-3) corresponded to water contact angles of 88.3°. 1.4 95.4 1.5 and 98.6 0.9 This is attributed to the hydrophobicity of the quaternary ammonium groups. The change in water contact angle indicates the successful preparation of the nanoparticle coating.

[0031] The antibacterial properties of Comparative Examples 1 and 2, as well as the samples from Examples 1-3 of this invention, were tested using the plate coating method. Staphylococcus aureus was selected for preliminary investigation, and the test results are as follows: Figure 4 As shown. The specific test method is as follows: First, sterilize the sample by irradiating both sides with ultraviolet light for 30 minutes each, then add 50 μL of bacterial suspension (10 6 A bacterial suspension (CFU / mL) was dropped onto the sample surface and covered with a sterile covering film to ensure uniform distribution of the bacterial suspension on the sample surface. After co-culturing the sample and bacterial suspension at 37 °C for 24 h, the sample surface was thoroughly rinsed with 2 mL of sterile PBS solution, and the eluent was serially diluted. 100 μL of the diluted eluent was evenly spread onto agar medium and incubated at 37 °C for 18 h, during which time the colony count was recorded. Figure 4 (a) and (b) correspond to Comparative Examples 1 and 2 of the present invention. Figure 4 (c)~(e) correspond to Examples 1~3 of the present invention. It can be seen that dense colony growth was observed on the agar plate corresponding to PE (Comparative Example 1), indicating that PE does not possess antibacterial properties. In contrast, a significant reduction in colony count was observed on the agar plate corresponding to the nano-zinc oxide (ZnO) coating (Comparative Example 2), which is attributed to the inherent antibacterial properties of ZnO. However, no colony growth was observed on the agar plate corresponding to the quaternized nano-zinc oxide (ZnO-Q) coating (Examples 1~3), demonstrating an antibacterial efficiency greater than 99.9%. Furthermore, the ZnO-Q concentration in Example 1 of the present invention was only 0.1 mg / mL, indicating that the coating possesses excellent antibacterial properties even at low addition levels, verifying the synergistic and efficient antibacterial effect of zinc ions and quaternary ammonium salts.

[0032] The biocompatibility of the samples in Comparative Example 1 and Example 2 of this invention was evaluated by performing cytotoxicity tests, and the test results are as follows: Figure 5 As shown. The specific test method is as follows: The effect of the quaternized zinc oxide nano-antibacterial coating on cell viability was detected by the CCK-8 method, with human biliary epithelial cells as a representative. The ultraviolet-sterilized sample was placed in a 96-well plate, and the cell suspension was seeded into each well, adjusting the cell concentration to 3×10⁶. 5 / well. Cells were incubated at 37 °C for 48 h in a 5% CO2 incubator, followed by incubation with 10 μL of CCK-8 solution for 90 min. The absorbance at 490 nm was measured using a microplate reader. CCK-8 solution and unmodified PE were used as the blank and control groups, respectively, and cell viability was calculated using the following formula.

[0033] It can be seen that the cell survival rate of the sample modified with quaternized nano zinc oxide coating (Example 2) is not significantly different from that of the unmodified PE (Comparative Example 1). The composite coating has good biocompatibility and has the potential to be applied to different application scenarios such as medical devices, food packaging, and water treatment.

[0034] Example 4: Step 1: Preparation of Quaternized Zinc Oxide Nanoparticles: 0.5 g of zinc oxide nanoparticles with a particle size of 10 nm were ultrasonically treated at 40 kHz and 200 W for 2 h and uniformly dispersed in a mixed solvent of deionized water (40 mL) and methanol (10 mL) to prepare a nanoparticle dispersion; 1 g of dimethylhexadecyl[3-(trimethoxysilyl)propyl]ammonium chloride was added to the dispersion, and the mixture was stirred continuously at 90 °C for 12 h; after the reaction was completed, the modified zinc oxide nanoparticles were separated by centrifugation and washed three times with anhydrous ethanol to remove unreacted grafted silane coupling agent; the product was dried at 60 °C for 12 h to obtain quaternized zinc oxide nanoparticles; Step 2: Co-deposition modification of substrate surface with polydopamine and polyethyleneimine: A titanium alloy plate was selected as the substrate. The titanium alloy plate was ultrasonically cleaned with methanol and acetone sequentially at 40 kHz and 100 W for 5 min, and then dried in a forced-air oven at 60 ℃ for 30 min. Dopamine hydrochloride and polyethyleneimine (… M w =70000) was dissolved in Tris-HCl buffer (10 mM, pH 8.5), with a concentration of 1 mg / mL; the titanium alloy plate was completely immersed in the above solution and kept in the dark with 100 rpm shaking environment for 24 h; it was thoroughly washed with deionized water and dried under vacuum at 60 ℃ for 8 h to obtain the modified substrate; Step 3: Spraying or dipping quaternized nano zinc oxide onto the substrate surface: Prepare a quaternized nano zinc oxide dispersion with a concentration of 5 mg / mL, immerse the modified substrate in the nanoparticle dispersion, let it stand for 12 h, and rinse the surface thoroughly with deionized water; dry the coating at 60 ℃ for 12 h to obtain an antibacterial composite coating.

[0035] Titanium alloys can be used as orthopedic implants. Applying the coating of this invention to their surface and the co-deposited layer can promote osteoblast adhesion and differentiation. The effective antibacterial activity of quaternized nano zinc oxide can effectively prevent early postoperative bacterial colonization and delayed infection. Its strong bonding force can withstand friction during surgical implantation and remain stable during long-term service in the body, which is expected to promote the development of a new generation of antibacterial medical devices and implant materials.

[0036] Example 5: Step 1: Preparation of quaternized zinc oxide nanoparticles: 2 g of 100 nm zinc oxide nanoparticles were ultrasonically treated at 40 kHz and 200 W for 6 h and uniformly dispersed in a mixed solvent of deionized water (80 mL) and methanol (20 mL) to prepare a nanoparticle dispersion; 10 g of dimethyltetradecyl[3-(trimethoxysilyl)propyl]ammonium chloride was added to the dispersion, and the mixture was stirred continuously at 70 °C for 18 h; after the reaction was completed, the modified zinc oxide nanoparticles were separated by centrifugation and washed three times with anhydrous ethanol to remove unreacted grafted silane coupling agent; the product was dried at 60 °C for 12 h to obtain quaternized zinc oxide nanoparticles; Step 2: Co-deposition and modification of the substrate surface with polydopamine and polyethyleneimine: A glass plate was selected as the substrate. The glass plate was ultrasonically cleaned with methanol and acetone sequentially for 10 min, and then dried in a forced-air oven at 60 ℃ for 30 min. Dopamine hydrochloride and polyethyleneimine (… M w=70000) was dissolved in Tris-HCl buffer (10 mM, pH 8.5) at a concentration of 5 mg / mL; the glass plate was completely immersed in the above solution and kept in the dark with shaking at 100 rpm for 24 h; it was thoroughly washed with deionized water and dried under vacuum at 60 ℃ for 8 h to obtain the modified substrate; Step 3: Spraying or dipping quaternized nano zinc oxide onto the substrate surface: Prepare a quaternized nano zinc oxide dispersion with a concentration of 3 mg / mL, immerse the modified substrate in the nanoparticle dispersion, let it stand for 12 h, and rinse the surface thoroughly with deionized water; dry the coating at 60 ℃ for 8 h to obtain an antibacterial composite coating.

[0037] Example 6: Step 1: Preparation of quaternized zinc oxide nanoparticles: 5 g of 40 nm zinc oxide nanoparticles were ultrasonically treated at 40 kHz and 200 W for 3 h and uniformly dispersed in a mixed solvent of deionized water (200 mL) and methanol (50 mL) to prepare a nanoparticle dispersion; 7 g of dimethyl dodecyl[3-(trimethoxysilyl)propyl]ammonium chloride was added to the dispersion, and the mixture was stirred continuously at 60 °C for 24 h; after the reaction was completed, the modified zinc oxide nanoparticles were separated by centrifugation and washed three times with anhydrous ethanol to remove unreacted grafted silane coupling agent; the product was dried at 60 °C for 12 h to obtain quaternized zinc oxide nanoparticles; Step 2: Co-deposition and modification of the substrate surface with polydopamine and polyethyleneimine: A cobalt-chromium alloy film was selected as the substrate. The cobalt-chromium alloy film was ultrasonically cleaned with methanol and acetone sequentially for 15 min, and then dried in a forced-air oven at 60 ℃ for 30 min. Dopamine hydrochloride and polyethyleneimine (… M w =70000) was dissolved in Tris-HCl buffer (10 mM, pH 8.5), with a concentration of 10 mg / mL; the cobalt-chromium alloy film was completely immersed in the above solution and kept in the dark with shaking at 100 rpm for 24 h; it was thoroughly washed with deionized water and dried under vacuum at 60 ℃ for 5 h to obtain the modified substrate; Step 3: Spraying or dipping quaternized nano zinc oxide onto the substrate surface: Prepare a quaternized nano zinc oxide dispersion with a concentration of 8 mg / mL, and spray the nanoparticle dispersion onto the modified substrate surface. The spraying pressure is 0.3 MPa, the distance between the spray gun and the substrate surface is 220 mm, and the spray gun moving speed is 400 mm / s. Rinse the surface thoroughly with deionized water. Dry the coating at 60℃ for 8 h to obtain an antibacterial composite coating.

[0038] Example 7 Example 7 is basically the same as Example 6, except that in step 3 the spraying pressure is 0.2 MPa, the distance between the spray gun and the substrate surface is 200 mm, and the spray gun moving speed is 300 mm / s.

[0039] Example 8 Example 8 is basically the same as Example 6, except that in step 3 the spraying pressure is 0.6 MPa, the distance between the spray gun and the substrate surface is 250 mm, and the spray gun moving speed is 500 mm / s.

[0040] The coating of this invention has good biocompatibility. When applied to the surface of medical catheters made of polyurethane or silicone rubber, the effective antibacterial activity of quaternized nano zinc oxide can effectively inhibit bacterial colonization and biofilm formation. The structure formed by the chemical bonding of the coating can meet the stability requirements for long-term use, and is expected to promote the development of next-generation antibacterial medical devices and implantable materials.

[0041] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an antibacterial composite coating based on quaternized nano zinc oxide, characterized in that, Includes the following steps: Step 1: Graft quaternary ammonium salt compounds onto the surface of nano-zinc oxide to prepare quaternized zinc oxide nano-particles with synergistic antibacterial properties. Step 2: Modify the substrate surface by co-deposition of dopamine and polyethyleneimine to introduce active functional groups; Step 3: Spray or dip-coat the modified substrate surface with quaternized nano zinc oxide to obtain an antibacterial composite coating.

2. The method for preparing the antibacterial composite coating based on quaternized nano zinc oxide according to claim 1, characterized in that, The method for grafting quaternary ammonium salt compounds onto the surface of nano-zinc oxide as described in step one includes the following steps: S1: Disperse 0.5~5 g of nano zinc oxide uniformly in 50~500 mL of solvent to prepare a nanoparticle dispersion; S2: Add 1~10 g of silane coupling agent containing quaternary ammonium functional groups to the dispersion, and stir continuously at 60~90 ℃ for 12~24 h. After the reaction is completed, centrifuge, wash with alcohol and dry to obtain quaternized zinc oxide nanoparticles.

3. The method for preparing the antibacterial composite coating based on quaternized nano zinc oxide according to claim 2, characterized in that, The solvent mentioned in step S1 is a mixed solvent prepared by methanol and deionized water at a volume ratio of 1:

4.

4. The method for preparing the antibacterial composite coating based on quaternized nano zinc oxide according to claim 2, characterized in that, The silane coupling agent containing quaternary ammonium functional groups mentioned in step S2 includes any one of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, dimethylhexadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, dimethyltetradecyl[3-(trimethoxysilyl)propyl]ammonium chloride, and dimethyldodecyl[3-(trimethoxysilyl)propyl]ammonium chloride.

5. The method for preparing the antibacterial composite coating based on quaternized nano zinc oxide according to claim 1, characterized in that, The method for co-depositing and modifying the substrate surface with dopamine and polyethyleneimine as described in step two specifically includes the following steps: S1: The substrate is ultrasonically cleaned sequentially with methanol and acetone, and then dried in a forced-air oven; S2: Dissolve dopamine hydrochloride and polyethyleneimine in Tris-HCl buffer; wherein the mass ratio of dopamine hydrochloride and polyethyleneimine is 1:1, and the concentrations are 1~10 mg / mL, respectively. S3: Immerse the substrate completely in the above solution and keep it in the dark with a 100 rpm oscillation environment for 24 h; S4: Thoroughly clean with deionized water and dry to obtain the modified substrate.

6. The method for preparing the antibacterial composite coating based on quaternized nano zinc oxide according to claim 1, characterized in that, The substrate mentioned in step two includes any one of metal, inorganic non-metallic materials, and polymer materials.

7. The method for preparing the antibacterial composite coating based on quaternized nano zinc oxide according to claim 1, characterized in that, The method for spraying or dipping quaternized nano zinc oxide onto the modified substrate surface as described in step three includes the following steps: S1: Prepare a quaternized zinc oxide nano-dispersion with a concentration of 0.1~10 mg / mL; S2: The dispersion is sprayed or dipped onto the modified substrate surface by spraying or dipping; the spraying pressure is 0.2~0.6 MPa, the distance between the spray gun and the substrate surface is 200~250 mm, and the spray gun moving speed is 300~500 mm / s. S3: Vacuum dry the coating at 60 ℃ for 5~12 h to obtain the antibacterial composite coating.

8. The method for preparing the antibacterial composite coating based on quaternized nano zinc oxide according to claim 7, characterized in that, The solvent for the quaternized nano zinc oxide dispersion mentioned in step S1 includes any one of methanol, ethanol, isopropanol, acetone, and chloroform.

9. An antibacterial composite coating based on quaternized nano zinc oxide prepared by the method according to any one of claims 1-8.

10. The application of the antibacterial composite coating based on quaternized nano zinc oxide as described in claim 9 on the surface of substrates in the fields of medical, food, building materials, and textiles.

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