Antibacterial coating, preparation method and application

Abstract

According to the antibacterial coating and the preparation method provided by the invention, the degradation rate of the magnesium alloy can be remarkably reduced by the composite coating formed by combining the micro-arc oxidation film layer and the copper-doped ZIF-8 coating, copper is doped when the ZIF-8 coating is prepared, and the ZIF-8 coating can be endowed with relatively strong antibacterial performance aiming at gram-positive bacteria and gram-negative bacteria; the coating material is mainly applied to the surface of a magnesium alloy implantation instrument, and a stable surface structure with excellent biocompatibility is formed by controlling the degradation rate of magnesium alloy, so that subcutaneous gas accumulation generated by rapid degradation and hemolysis and bone dissolution caused by a local strong alkaline environment are avoided; severely, the problems that an implantation instrument loses fixing and supporting functions before tissue healing, and implantation fails are caused are solved; meanwhile, the early adhesion of bacteria and the formation of bacterial biofilms are effectively inhibited by utilizing the antibacterial function of the coating, so that the infection risk generated in the implanting and using processes of the implanting instrument is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of antibacterial and anticorrosive coatings, and in particular to an antibacterial coating and a preparation method thereof. Background Art

[0002] Magnesium (Mg) and its alloys have excellent mechanical applicability, biocompatibility and biodegradability, and have received widespread attention in the field of tissue engineering. Its density and elastic modulus are similar to those of natural cortical bone, thereby reducing the stress shielding effect. In addition, magnesium can be completely degraded in human body fluids and excreted from the body through metabolism, thereby avoiding secondary surgery for removal, reducing medical costs and alleviating patient pain (J Mater Sci Technol, 2013, 29 (6): 489-502.). The main challenge currently faced by magnesium alloys in clinical practice is that the rapid degradation rate leads to the production of a large amount of hydrogen and a rapid increase in the pH of the local microenvironment, which causes subcutaneous gas accumulation, hemolysis and osteolysis, and in severe cases may lead to implant failure. In order to solve this problem, the present invention designs a protective coating on the surface of the magnesium-based implant material to control its degradation rate. In the past, it was widely believed that the alkaline microenvironment generated by the degradation of magnesium alloys is conducive to improving the bactericidal function and thus reducing the risk of implant infection. However, studies have shown that magnesium-based metals do not have antibacterial function in the body (Bioactive Materials 6 (2021)

[0003] 3049-3061), so it is very necessary to give the magnesium alloy surface coating antibacterial functionality.

[0004] Micro-arc oxidation (MAO) is one of the most commonly used and effective surface modification techniques for preparing protective coatings on magnesium alloy surfaces. MAO treatment can form surface coatings on magnesium alloys that exhibit high hardness, good wear and corrosion resistance, excellent thermal stability, and superior biocompatibility. This technology is environmentally friendly, simple, economical, and highly efficient. However, there are few reports on using MAO to produce antibacterial coatings on magnesium alloy surfaces. This is because inorganic antibacterial ions, such as Cu and Ag ions, are difficult to incorporate into the coating, necessitating additional treatment to enhance its antibacterial properties.

[0005] ZIF-8 is a subfamily of metal-organic frameworks (MOFs) composed of zinc ions coordinated with imidazole tetrahedra (Proc. Natl. Acad. Sci. USA, 118(10)(2021), Article e2008880118). ZIF-8 coatings are easy to synthesize and have good chemical and thermal stability (ACS Appl. Bio Mater., 3(6)(2020), pp.3673-3680; J. Mater. Sci., 54(7)(2018), pp.5513-5527). ZIF-8 has good antibacterial properties against Gram-positive bacteria (such as Staphylococcus aureus), but has low antibacterial efficiency against Gram-negative bacteria (such as Escherichia coli) (Journal of Environmental Chemical Engineering 2021Vol.9Issue 1).

[0006] Existing coatings designed to control the degradation rate of magnesium alloys generally lack antibacterial properties, making implants susceptible to bacterial infection during implantation and use. Once a bacterial biofilm forms on an implant, it is extremely difficult to remove, requiring a secondary surgery for removal, increasing medical costs and causing significant pain for the patient. The preparation of ZIF-8 coatings typically requires stringent conditions, such as high temperature and high pressure, and the complex preparation process limits their application. Furthermore, when ZIF-8 coatings are prepared on top of MAO coatings, the high temperature and high pressure environment can easily cause defects or even damage to the MAO coating, resulting in poor degradation protection. Furthermore, single ZIF-8 coatings have low antibacterial efficiency against Gram-negative bacteria, such as Escherichia coli. Summary of the Invention

[0007] In view of this, it is necessary to provide an antibacterial coating, preparation method and application that can effectively control the degradation rate of magnesium alloy and has good biocompatibility to address the technical problem of poor antibacterial performance of current medical magnesium alloy samples.

[0008] To solve the above problems, this application adopts the following technical solutions:

[0009] One of the purposes of this application is to provide a method for preparing an antibacterial coating, comprising the following steps:

[0010] The magnesium alloy is placed in an electrolyte and subjected to micro-arc oxidation treatment to form a micro-arc oxidation film layer;

[0011] The magnesium alloy after micro-arc oxidation treatment is placed in a mixed solution of solution A and solution B and allowed to stand at room temperature, and then taken out and dried to obtain a copper-doped ZIF-8 coating formed on the surface of the micro-arc oxidation film layer;

[0012] Wherein: the solution A is a solution in which Zn(NO3)·6H2O and CuSO4·5H2O are dissolved in anhydrous methanol, and the solution B is a solution in which 2-mIm is dissolved in anhydrous methanol.

[0013] In some embodiments, the step of placing the magnesium alloy in an electrolyte for micro-arc oxidation treatment specifically includes the following steps:

[0014] The magnesium alloy is placed in an electrolyte and subjected to micro-arc oxidation treatment in a single-pulse constant current mode. After the reaction is completed, the sample is taken out, ultrasonically cleaned with anhydrous ethanol, and dried to obtain a magnesium alloy with a micro-arc oxidation film. The electrolyte contains NaOH, Ca(H2PO4)2 and Na 12 The mass ratio of Phy was 3:2:2, and the reaction conditions were 25-75 mA cm -2 constant current, 25-35% duty cycle, 1000-2000Hz pulse frequency, and processing time of 3-5min.

[0015] In some embodiments, before the step of placing the magnesium alloy in an electrolyte for micro-arc oxidation treatment, the following steps are also included:

[0016] The magnesium alloy is ground with SiC sandpaper or any grinding equipment, and ultrasonically cleaned with acetone and anhydrous ethanol. The magnesium alloy is then taken out and dried for later use.

[0017] In some embodiments, the magnesium alloy after micro-arc oxidation treatment is placed in a mixed solution including solution A and solution B and allowed to stand at room temperature for treatment, and then taken out and dried to obtain a copper-doped ZIF-8 coating formed on the surface of the micro-arc oxidation film layer. In the step, 10.6g Zn(NO3)·6H2O and 4.4g CuSO4·5H2O are added to each liter of anhydrous methanol in the solution A; 16.2g 2-mIm is added to each liter of anhydrous methanol in the solution B; the volume ratio of the solution A to the solution B is 1:1, and the molar ratio of the Zn(NO3)·6H2O, the CuSO4·5H2O, and the 2-mIm is 15:8:51.

[0018] In some embodiments, the standing treatment time is 12h-24h.

[0019] The second purpose of this application is to provide an antibacterial coating prepared by the preparation method.

[0020] The third purpose of this application is to provide an application of the antibacterial coating in an orthopedic implant.

[0021] This application adopts the above technical solution, and its beneficial effects are as follows:

[0022] The antibacterial coating and preparation method provided in the present application, a composite coating combining a micro-arc oxidation film layer with a copper-doped ZIF-8 coating, can significantly reduce the degradation rate of magnesium alloys. Copper is doped during the preparation of the ZIF-8 coating, which can give it strong antibacterial properties against Gram-positive and Gram-negative bacteria. The coating material is mainly used on the surface of magnesium alloy implants. By controlling the degradation rate of the magnesium alloy to form a stable surface structure with excellent biocompatibility, the subcutaneous gas accumulation caused by rapid degradation and the hemolysis and osteolysis caused by the local strong alkaline environment are avoided. In severe cases, the implanted device may lose its fixation and support functions before tissue healing, resulting in implant failure. At the same time, the antibacterial function of the coating is used to effectively inhibit the early adhesion of bacteria and the formation of bacterial biofilms, thereby reducing the risk of infection generated by the implanted device during implantation and use. The present invention enhances the potential for clinical application of magnesium alloys in orthopedics by constructing a layer of antibacterial coating with good biocompatibility on the surface of the magnesium alloy implant material that can effectively control the degradation rate of the magnesium alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 A flowchart of the steps of a method for preparing an antibacterial coating provided in one embodiment of the present invention.

[0025] Figure 2 The electrochemical test results of the antibacterial composite coating provided in one embodiment of the present invention in PBS solution.

[0026] Figure 3 Schematic diagram of bacterial plate and statistical analysis of the co-culture of the Cu@ZIF-8-MAO composite coating and Escherichia coli for 24 hours provided by one embodiment of the present invention.

[0027] Figure 4 Schematic diagram of bacterial plate and statistical analysis of the co-culture of the Cu@ZIF-8-MAO composite coating and Staphylococcus aureus for 24 hours provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0029] In the description of this application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this application.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0031] In order to make the purpose, technical solutions and advantages of this application more clear, this application is further described in detail below with reference to the accompanying drawings and embodiments.

[0032] See also Figure 1 , provides a step flow chart of a method for preparing an antibacterial coating for an embodiment of the present application, specifically including the following steps S110 to S120, and the implementation method of each step is described in detail below.

[0033] Step S110: placing the magnesium alloy in an electrolyte for micro-arc oxidation treatment to form a micro-arc oxidation film.

[0034] In this embodiment, the step of placing the magnesium alloy in an electrolyte for micro-arc oxidation treatment specifically includes the following steps:

[0035] The magnesium alloy is placed in an electrolyte and subjected to micro-arc oxidation treatment in a single-pulse constant current mode. After the reaction is completed, the sample is taken out, ultrasonically cleaned with anhydrous ethanol, and dried to obtain a magnesium alloy with a micro-arc oxidation film. The electrolyte contains NaOH, Ca(H2PO4)2 and Na 12 The mass ratio of Phy was 3:2:2, and the reaction conditions were 25-75 mA cm -2 constant current, 25-35% duty cycle, 1000-2000Hz pulse frequency, and processing time of 3-5min.

[0036] Furthermore, before the step of placing the magnesium alloy in an electrolyte for micro-arc oxidation treatment, the method further includes the following steps: grinding the magnesium alloy with SiC sandpaper or any grinding equipment, ultrasonically cleaning it with acetone and anhydrous ethanol, and then taking out the magnesium alloy and drying it for later use.

[0037] Step S120: placing the magnesium alloy after micro-arc oxidation treatment in a mixed solution of solution A and solution B and standing it at room temperature, then taking it out and drying it to obtain a copper-doped ZIF-8 coating formed on the surface of the micro-arc oxidation film layer, wherein: the solution A is a solution of Zn(NO3)·6H2O and CuSO4·5H2O dissolved in anhydrous methanol, and the solution B is a solution of 2-mIm dissolved in anhydrous methanol.

[0038] In some embodiments, in the step of placing a magnesium alloy after micro-arc oxidation treatment in a mixed solution including solution A and solution B for standing treatment at room temperature, and then removing and drying to obtain a copper-doped ZIF-8 coating formed on the surface of the micro-arc oxidation film layer, 10.6g of Zn(NO3)·6H2O and 4.4g of CuSO4·5H2O are added to each liter of anhydrous methanol in solution A; 16.2g of 2-mIm is added to each liter of anhydrous methanol in solution B; the volume ratio of solution A to solution B is 1:1, and the molar ratio of Zn(NO3)·6H2O, CuSO4·5H2O, and 2-mIm is 15:8:51. The standing treatment time is 12-24 hours.

[0039] Furthermore, in this embodiment, a copper-doped ZIF-8 coating is formed on the surface of the micro-arc oxidation film layer, thereby forming an antibacterial composite coating. The thickness of the composite coating is 16-100 μm. In practice, the coating thickness can be changed by changing the micro-arc oxidation process and the components of solution A and solution B.

[0040] It is understandable that the preparation of ZIF-8 coatings usually requires some relatively harsh conditions, such as high temperature and high pressure, and the preparation process is relatively complex, so its application limitations are relatively large. In addition, when preparing ZIF-8 coatings on the surface of MAO coatings, the high temperature and high pressure environment can easily cause defects or even damage to the MAO coating, resulting in poor degradation protection of the coating. The ZIF-8 coating in-situ growth method selected in the above-mentioned embodiments of the present application can react and form at room temperature and pressure, and the target coating can be obtained at room temperature through a simple chemical reaction, which can reduce the destructive effect on the MAO coating during the preparation process and will not produce destructive effects on the MAO coating.

[0041] It can be understood that a single ZIF-8 coating has low antibacterial efficiency against Gram-negative bacteria (such as Escherichia coli). In the above embodiment of the present application, copper is doped when preparing the ZIF-8 coating, which enables the coating to exhibit excellent antibacterial function against both Gram-positive and Gram-negative bacteria.

[0042] The antibacterial coating and preparation method provided in the above-mentioned embodiments of the present application, which combines a micro-arc oxidation film layer with a copper-doped ZIF-8 coating to form a composite coating, can significantly reduce the degradation rate of magnesium alloys. The copper element is doped during the preparation of the ZIF-8 coating, which can give it strong antibacterial properties against Gram-positive and Gram-negative bacteria. The coating material is mainly used on the surface of magnesium alloy implants. By controlling the degradation rate of the magnesium alloy to form a stable surface structure with excellent biocompatibility, it avoids the accumulation of subcutaneous gas caused by rapid degradation and the hemolysis and osteolysis caused by the local strong alkaline environment. In severe cases, the implanted device may lose its fixation and support functions before tissue healing, leading to implant failure. At the same time, the antibacterial function of the coating is used to effectively inhibit the early adhesion of bacteria and the formation of bacterial biofilms, thereby reducing the risk of infection during implantation and use of the implanted device. The present invention constructs a layer of antibacterial coating with good biocompatibility on the surface of the magnesium alloy implant material that can effectively control the degradation rate of the magnesium alloy. It can be used in the preparation of orthopedic implants to enhance the potential of magnesium alloys in orthopedic clinical applications.

[0043] Example

[0044] The metal substrate used in this embodiment is WE43 magnesium alloy, and the thickness of the Cu@ZIF-8-MAO composite coating is 80 μm. The preparation method of the antibacterial coating used in this embodiment can be found in the above description. Only the experimental results are given here.

[0045] 1) Degradation performance of Cu@ZIF-8-MAO composite coating

[0046] Electrochemical tests were carried out using ZIF-8-MAO composite coatings and copper-doped ZIF-8 composite coatings (Cu@ZIF-8-MAO) in PBS solution. The polarization curves and impedance spectrum test results are shown in Figure 2. Figure 2 As shown in (a) polarization curve, (b) impedance spectrum. As can be seen from the figure, the corrosion current density of the Cu@ZIF-8-MAO coating is reduced compared with that of the WE43 magnesium alloy, while the electrochemical impedance arc radius is greatly increased compared with that of the WE43 magnesium alloy, indicating that the degradation rate of the WE43 magnesium alloy is effectively reduced.

[0047] 2) Antibacterial properties of Cu@ZIF-8-MAO composite coating

[0048] The ZIF-8-MAO composite coating samples and Cu@ZIF-8-MAO composite coating samples were co-cultured with Escherichia coli (E. coli) or Staphylococcus aureus (S. aureus) for 24 hours, and a plate coating experiment was performed. The plate counting method was used to evaluate the antibacterial properties of the ZIF-8-MAO composite coating samples and Cu@ZIF-8-MAO composite coating samples.

[0049] Figure 2 The bacterial plate represented by the co-culture of Cu@ZIF-8-MAO composite coating and E. coli for 24 h (see Figure 2 (a)) and statistical analysis (see Figure 2 (b)).

[0050] Figure 3 The Cu@ZIF-8-MAO composite coating was co-cultured with Staphylococcus aureus for 24 h on bacterial plates (see Figure 3 (a)) and statistical analysis (see Figure 3 (b)).

[0051] Depend on Figure 2 and Figure 3 It can be seen that the ZIF-8-MAO composite coating sample has poor antibacterial performance against Escherichia coli, and the Cu@ZIF-8-MAO composite coating exhibits good antibacterial performance against both Escherichia coli and Staphylococcus aureus.

[0052] It can be understood that the various technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0053] The above are merely preferred embodiments of the present application and only specifically describe the technical principles of the present application. These descriptions are intended only to explain the principles of the present application and should not be construed in any way as limiting the scope of protection of the present application. Based on the explanations herein, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application, as well as other specific implementations of the present application that can be conceived by those skilled in the art without inventive effort, shall be included within the scope of protection of the present application.

Claims

1. A method for preparing an antibacterial coating, characterized in that: The steps include: The magnesium alloy is placed in an electrolyte and subjected to micro-arc oxidation treatment to form a micro-arc oxidation film layer; The magnesium alloy after micro-arc oxidation treatment is placed in a mixed solution of solution A and solution B and allowed to stand at room temperature, and then taken out and dried to obtain a copper-doped ZIF-8 coating formed on the surface of the micro-arc oxidation film layer; Wherein: the solution A is a solution in which Zn(NO3)·6H2O and CuSO4·5H2O are dissolved in anhydrous methanol, and the solution B is a solution in which 2-mIm is dissolved in anhydrous methanol.

2. The method for preparing the antibacterial coating according to claim 1, wherein: The step of placing the magnesium alloy in an electrolyte for micro-arc oxidation treatment specifically includes the following steps: The magnesium alloy is placed in an electrolyte and subjected to micro-arc oxidation treatment in a single-pulse constant current mode. After the reaction is completed, the sample is taken out, ultrasonically cleaned with anhydrous ethanol, and dried to obtain a magnesium alloy with a micro-arc oxidation film. The electrolyte contains NaOH, Ca(H2PO4)2 and Na 12 The mass ratio of Phy was 3:2:2, and the reaction conditions were 25-75 mA cm -2 constant current, 25-35% duty cycle, 1000-2000Hz pulse frequency, and processing time of 3-5min.

3. The method for preparing the antibacterial coating according to claim 1 or 2, wherein: Before the step of placing the magnesium alloy in an electrolyte for micro-arc oxidation treatment, the method further includes the following steps: The magnesium alloy is ground with SiC sandpaper or any grinding equipment, and ultrasonically cleaned with acetone and anhydrous ethanol. The magnesium alloy is then taken out and dried for later use.

4. The method for preparing the antibacterial coating according to claim 1, wherein: The magnesium alloy after micro-arc oxidation treatment is placed in a mixed solution including solution A and solution B, and is allowed to stand at room temperature for treatment, and then taken out and dried to obtain a copper-doped ZIF-8 coating formed on the surface of the micro-arc oxidation film layer. In the step of: in the solution A, 10.6g Zn(NO3)·6H2O and 4.4g CuSO4·5H2O are added to each liter of anhydrous methanol; in the solution B, 16.2g 2-mIm is added to each liter of anhydrous methanol; the volume ratio of the solution A and the solution B is 1:1, and the molar ratio of the Zn(NO3)·6H2O, the CuSO4·5H2O, and the 2-mIm is 15:8:

51.

5. The method for preparing the antibacterial coating according to claim 1 or 4, wherein: The time for the static treatment is 12h-24h.

6. An antibacterial coating, characterized in that The compound is prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the antibacterial coating according to claim 6 in an orthopedic implant.

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