A photothermal, antibacterial, and corrosion-resistant medical magnesium alloy composite coating and its preparation method

Abstract

The present invention discloses a photothermal antibacterial and corrosion-resistant medical magnesium alloy composite coating and a preparation method thereof, comprising: step one, pretreatment; step two, micro-arc oxidation treatment; step three, hydrothermal preparation. Using Mg-Zn-Ca alloy as the matrix material, a layer of micro-arc oxidation coating is first prepared, and then the simple preparation technology of hydrotalcite is combined with MOFs to prepare a composite antibacterial coating of magnesium-iron LDH and MOFs by a two-step hydrothermal method. The preparation method of the present invention is simple to operate and has a short process flow; the prepared medical magnesium alloy composite coating has strong corrosion resistance, and at the same time, because the coating contains LDH and iron in MOFs, it has certain photothermal conversion performance and can achieve antibacterial properties.

Description

Technical Field

[0001] The present invention relates to the technical field of biomedical magnesium alloy surface modification, and in particular to a photothermal, antibacterial, and corrosion-resistant medical magnesium alloy composite coating and a preparation method thereof. Background Art

[0002] Ideal orthopedic implants should possess specific biological properties (such as biocompatibility and bioactivity) as well as mechanical and chemical properties (such as corrosion resistance and an elastic modulus similar to that of human bone). Magnesium and its alloys have outstanding mechanical properties, biocompatibility, and biodegradability, making them widely used in orthopedic implant research. Although medical magnesium alloys have been developed as materials for orthopedic implants, many challenges and difficulties remain to be overcome, including rapid osteogenesis and osseointegration on the implant surface, as well as the prevention of bacterial infection. This is particularly true for the non-invasive, rapid, and efficient in situ treatment and elimination of infections that develop on the implant surface, as well as the development of drug-resistant bacteria during subsequent antibiotic treatment. These issues often lead to implant failure in vivo. Surface coating technologies, with their superior surface properties and adaptable chemical structures, can enhance the other desired surface properties of bone implants, such as corrosion resistance and antibacterial properties, without compromising the overall material performance. Consequently, antimicrobial coating technology has garnered significant attention in recent years and has become a compelling research area.

[0003] Photothermal therapy is a remotely controlled, non-invasive treatment method. It avoids the drawbacks of traditional invasive treatments, achieving localized treatment without causing side effects on surrounding tissues. Therefore, the photothermal effect is used to efficiently eliminate bacteria while improving the biocompatibility of the coating.

[0004] (Dou J, Wang J, Lu Y, et al. Bioactive MAO / CS composite coatings onMg-Zn-Ca alloy for orthopedic applications[J]. Progress in Organic Coatings,2021, 152:106112. Imran M, Saifullah S, Kanwal T, et al. Synthesis ofchitosan coated metal organic frameworks (MOFs) for increasing vancomycinbactericidal potential against resistant S. aureus strain[J]. MaterialsScience and Engineering C, 2019, 105.) Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide a medical magnesium alloy composite coating having good corrosion resistance and antibacterial ability after near-infrared light activation and a preparation method thereof.

[0006] In a first aspect, a method for preparing a photothermal, antibacterial, and corrosion-resistant medical magnesium alloy composite coating of the present invention comprises the following steps:

[0007] Step 1, preprocessing;

[0008] The Mg-Zn-Ca alloy sample is polished, cleaned and dried to obtain a sample to be used;

[0009] Step 2: micro-arc oxidation treatment;

[0010] An electrolyte was prepared, and the sample to be used was used as an anode, stainless steel was used as a cathode, and the MAO mode was set to a constant current mode to obtain a Mg-Zn-Ca alloy micro-arc oxidation coating;

[0011] Step 3, hydrothermal preparation;

[0012] (1) Dissolve ferric nitrate, magnesium nitrate, sodium carbonate, and sodium hydroxide in water to prepare a hydrothermal treatment solution, transfer the sample with the micro-arc oxidation coating obtained in step 2 and the hydrothermal treatment solution to a reactor, place them in a drying oven for hydrothermal reaction, cool them to room temperature with the furnace after the reaction, take out the sample, ultrasonically treat it with anhydrous ethanol, and dry it with cold air to obtain the MAO / LDH coating;

[0013] (2) 0.2-1 g of ferric chloride and 0.2-5 g of sodium ferrocyanide were added to water to prepare a MOFs precursor solution. The MAO / LDH sample was placed vertically in a polytetrafluoroethylene-lined hydrothermal reactor. The MOFs precursor solution was then poured into the hydrothermal reactor. Finally, the reactor was placed in an oven for hydrothermal reaction. After the reaction was completed, the reactor was naturally cooled. The sample was taken out and placed in deionized water for ultrasonic treatment. After drying, the MAO / LDH / MOFs composite coating was obtained.

[0014] Furthermore, in step three, the composition of the hydrothermal treatment solution is: 3-100 g / L of ferric nitrate, 6-100 g / L of magnesium nitrate, 1-10 g / L of sodium carbonate, and 2-60 g / L of sodium hydroxide.

[0015] Furthermore, in the hydrothermal reactions (1) and (2) of step three, the reaction temperature is 40-120° C., and the reaction time is 4-12 h.

[0016] Furthermore, in step 3, the ultrasonic treatment time of deionized water is 10 to 20 minutes.

[0017] Furthermore, in step 2, the electrolyte uses water as a solvent and is composed of: 1-50 g / L sodium silicate, 1-50 g / L sodium hexametaphosphate, and 0.5-20 g / L sodium hydroxide.

[0018] Furthermore, the near-infrared light response temperature rise curve of the magnesium alloy composite coating prepared by the preparation method is from 0.6 w / cm 2 It is produced by near-infrared light excitation at a wavelength of 808 nm at low power.

[0019] In a second aspect, the present invention provides a photothermal, antibacterial, and corrosion-resistant magnesium alloy composite coating, which is prepared using the preparation method described in any one of the first aspects.

[0020] Furthermore, the phase components of the composite coating are magnesium oxide, magnesium silicate, magnesium hydroxide, hydrotalcite and MOFs.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The preparation method of the present invention combines the simple preparation technology of hydrotalcite with MOFs, and prepares them through a two-step hydrothermal method, so that they work together to produce photothermal properties. Through photothermal antibacterial, it is used to achieve the reduction of bacterial infection during the implantation of medical magnesium alloys. At the same time, MOFs are degradable metabolites, which increases biosafety.

[0023] (2) The preparation method of the present invention uses micro-arc oxidation to generate a MAO coating with a relatively thick thickness, which can effectively improve the corrosion resistance of medical magnesium alloys;

[0024] (3) The LDH coating prepared by the preparation method of the present invention can effectively seal the micropores and microcracks inherent in the MAO coating, so that the corrosion resistance of the sample is significantly improved on the basis of the MAO coating. By combining the hydrothermal method with the micro-arc oxidation method, the thickness of the prepared sample is increased while ensuring the functional effects such as photothermal antibacterial, thereby effectively increasing the corrosion resistance of the medical magnesium alloy;

[0025] (4) The composite coating prepared by the preparation method of the present invention has certain photothermal properties, can provide a new direction for clinical sterilization, and has new utility for postoperative infection problems caused by multidrug resistance. Its research significance is important and its development and application prospects are good.

[0026] It should be understood that the contents described in the summary of the invention are not intended to limit the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0028] Figure 1 Surface SEM images of MAO, MAO / LDH, and MAO / LDH / MOFs composite coatings, wherein (a) is the surface morphology of Comparative Example 1, (b) is the surface morphology of Comparative Example 2, and (c) is the surface morphology of Example 1;

[0029] Figure 2 The annual corrosion rate curves of MAO, MAO / LDH and MAO / LDH / MOFs composite coatings obtained after 16 days of hydrogen evolution;

[0030] Figure 3 Electrochemical impedance spectroscopy of MAO, MAO / LDH and MAO / LDH / MOFs composite coatings;

[0031] Figure 4 The MAO, MAO / LDH and MAO / LDH / MOFs composite coatings were 0.6 w / cm 2 Photothermal curve of near-infrared light excitation with a wavelength of 808 nm at different powers. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the invention are shown in the accompanying drawings.

[0033] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments. Example 1

[0034] A method for preparing a photothermal, antibacterial, and corrosion-resistant medical magnesium alloy composite coating, comprising the following steps:

[0035] Step 1, preprocessing;

[0036] An 8 mm diameter and 3 mm thick extruded magnesium alloy (Mg-Zn-Ca alloy, 3.0% Zn mass fraction, 0.2% Ca mass fraction) was selected as the substrate. The substrate was gradually polished to 3000# with silicon carbide (SiC) sandpaper, then washed with ethanol and deionized water for 5 min respectively, and finally dried in air.

[0037] Step 2: micro-arc oxidation (MAO) treatment;

[0038] (1) A mixed aqueous solution of 10 g / L sodium silicate, 3 g / L sodium hexametaphosphate, and 5 g / L sodium hydroxide was prepared to prepare an electrolyte;

[0039] (2) The sample was used as the anode and the stainless steel was used as the cathode. The MAO mode was constant current mode with a positive current of 0.6 A, a negative current of 0.1 A, a frequency of 500 Hz, a positive duty cycle of 40%, a negative duty cycle of 20%, and a treatment time of 12 min. The reaction temperature was controlled below 35 °C to obtain a Mg-Zn-Ca alloy micro-arc oxidation coating. The sample was then ultrasonically treated in anhydrous ethanol and dried with a hair dryer.

[0040] Step 3, hydrothermal preparation;

[0041] (1) Take 7.415 g of ferric nitrate, 6.0465 g of magnesium nitrate, 0.79 g of sodium carbonate, and 6 g of sodium hydroxide and dissolve them in 110 mL of water to prepare a hydrothermal treatment solution. Transfer the sample with micro-arc oxidation coating obtained in step 2 and the hydrothermal treatment solution to a reactor, put it in a drying oven at 85 ° C, and heat it for 12 h. After the hydrothermal reaction, cool it to room temperature with the furnace, take it out, treat it with anhydrous ethanol by ultrasonic treatment, and blow dry it with cold air from a hair dryer to obtain the MAO / LDH coating.

[0042] (2) Add 0.27 g of ferric chloride and 0.5 g of sodium ferrocyanide to water to prepare a MOFs precursor solution. Place the MAO / LDH sample vertically in a polytetrafluoroethylene-lined hydrothermal reactor. Then pour the MOFs precursor solution into the hydrothermal reactor. The reaction temperature is 40 °C. Place the reactor in an oven and react for 6 h before cooling naturally. Take out the sample and place it in deionized water for ultrasonic treatment for 10 min. After drying, the MAO / LDH / MOFs composite coating is obtained.

[0043] Prussian blue nanoparticles (PBNPs) are a long-established MOF material with exceptionally high biosafety. They have been approved by the FDA for clinical use as an antidote. In this example, the primary component of the MOF precursor solution is Prussian blue (PB). Example 2

[0044] The main difference between this embodiment and embodiment 1 is the hydrothermal preparation in step 3. The specific implementation process of step 3 in this embodiment is as follows:

[0045] (1) Take 7.415 g of ferric nitrate, 6.0465 g of magnesium nitrate, 0.79 g of sodium carbonate, and 6 g of sodium hydroxide and dissolve them in 110 mL of water to prepare a hydrothermal treatment solution. Transfer the sample with micro-arc oxidation coating obtained in step 2 and the hydrothermal treatment solution to a reactor, place it in a drying oven at 85 ° C, and heat it for 12 h. After the hydrothermal reaction, cool it to room temperature with the furnace, take it out, treat it with anhydrous ethanol by ultrasonication, and blow dry it with cold air from a hair dryer to obtain MAO / LDH.

[0046] (2) Add 0.2 g of ferric chloride and 0.2 g of sodium ferrocyanide to water to prepare a MOFs precursor solution. Place the MAO / LDH sample vertically in a polytetrafluoroethylene-lined hydrothermal reactor. Then pour the MOFs precursor solution into the hydrothermal reactor. The reaction temperature is 40 °C. Place the reactor in an oven and react for 6 h before cooling naturally. Take out the sample and place it in deionized water for ultrasonic treatment for 10 min. After drying, the MAO / LDH / MOFs composite coating is obtained. Example 3

[0047] The main difference between this embodiment and embodiment 1 is the hydrothermal preparation in step 3. The specific implementation process of step 3 in this embodiment is as follows:

[0048] (1) Take 7.415 g of ferric nitrate, 6.0465 g of magnesium nitrate, 0.79 g of sodium carbonate, and 6 g of sodium hydroxide and dissolve them in 110 mL of water to prepare a hydrothermal treatment solution. Transfer the sample with micro-arc oxidation coating obtained in step 2 and the hydrothermal treatment solution to a reactor, place it in a drying oven at 85 ° C, and heat it for 12 h. After the hydrothermal reaction, cool it to room temperature with the furnace, take it out, treat it with anhydrous ethanol by ultrasonication, and blow dry it with cold air from a hair dryer to obtain MAO / LDH.

[0049] (2) Add 1 g of ferric chloride and 5 g of sodium ferrocyanide to water to prepare a MOFs precursor solution. Place the MAO / LDH sample vertically in a polytetrafluoroethylene-lined hydrothermal reactor. Then pour the MOFs precursor solution into the hydrothermal reactor. The reaction temperature is 40 °C. Place the reactor in an oven and react for 6 h before cooling naturally. Take out the sample and place it in deionized water for ultrasonic treatment for 10 min. After drying, the MAO / LDH / MOFs composite coating is obtained. Comparative Example 1

[0050] A method for preparing a photothermal, antibacterial, and corrosion-resistant medical magnesium alloy composite coating, comprising the following steps:

[0051] Step 1, preprocessing;

[0052] An 8 mm diameter and 3 mm thick extruded magnesium alloy (Mg-Zn-Ca alloy, 3.0% Zn mass fraction, 0.2% Ca mass fraction) was selected as the substrate. The substrate was gradually polished to 3000# with silicon carbide (SiC) sandpaper, then washed with ethanol and deionized water for 5 min respectively, and finally dried in air.

[0053] Step 2: micro-arc oxidation (MAO) treatment;

[0054] (1) A mixed aqueous solution of 10 g / L sodium silicate, 3 g / L sodium hexametaphosphate, and 5 g / L sodium hydroxide was prepared to prepare an electrolyte;

[0055] (2) The sample was used as the anode and the stainless steel was used as the cathode. The MAO mode was constant current mode with a positive current of 0.6 A, a negative current of 0.1 A, a frequency of 500 Hz, a positive duty cycle of 40%, a negative duty cycle of 20%, and a treatment time of 12 min. The reaction temperature was controlled below 35 °C to obtain a Mg-Zn-Ca alloy micro-arc oxidation coating. The sample was then ultrasonically treated in anhydrous ethanol and dried with a hair dryer. Comparative Example 2

[0056] The main difference between this comparative example and comparative example 1 is that step 3 is added. The specific implementation process of step 3 in this comparative example is as follows:

[0057] Take 7.415 g of ferric nitrate, 6.0465 g of magnesium nitrate, 0.79 g of sodium carbonate, and 6 g of sodium hydroxide and dissolve them in 110 mL of water to prepare a hydrothermal treatment solution. The sample with the micro-arc oxidation coating obtained in step 2 and the hydrothermal treatment solution are transferred to a reactor and placed in a drying oven at 85°C for 12 h. After the hydrothermal reaction, the sample is cooled to room temperature with the furnace, taken out, ultrasonically treated with anhydrous ethanol, and dried with cold air from a hair dryer to obtain the MAO / LDH coating.

[0058] Test Case

[0059] Example 1 was selected as a representative example, and surface SEM, annual corrosion rate, electrochemical impedance and near-infrared light excitation temperature rise tests were performed on the samples prepared in Comparative Examples 1 and 2, respectively. The results are shown in Table 1. Figures 1 to 4 .

[0060] like Figure 1 As shown in the surface SEM images, Figure (a) shows that the surface of the sample after micro-arc oxidation treatment has a typical porous morphology of micro-arc oxidation, proving that the micro-arc oxidation coating is successfully prepared on the Mg-Zn-Ca alloy substrate; Figure (b) shows that the surface of the sample after one-step hydrothermal treatment is completely covered by nanosheet-structured LDH, proving the successful loading of the LDH coating; Figure (c) shows that the surface of the sample prepared by the two-step hydrothermal method is covered with flat and uniform small cubic particles, which is the typical structure of PB, proving that PB is successfully prepared on the sample surface.

[0061] like Figure 2 As shown in the annual corrosion rate curve obtained after 16 days of hydrogen evolution, the corrosion rate of the MAO / LDH / MOFs composite coating did not change much in the first few days, and changed relatively slowly in the later period, with the lowest annual corrosion rate, indicating that it has good corrosion resistance. Only the corrosion rate of the micro-arc oxidation (MAO) coating on the surface changed significantly, with an annual corrosion rate of 0.4, indicating that it has a certain protective effect, but not as good as the composite coating. The annual corrosion rates of the two are quite different. The corrosion resistance of the MAO / LDH / MOFs composite coating is greatly improved than that of the micro-arc oxidation coating.

[0062] like Figure 3 As shown in the electrochemical impedance spectrum, the MAO / LDH / MOFs coating has a larger semicircle diameter, and its diameter is much larger than the diameter of micro-arc oxidation. Since the larger the impedance ring radius, the better the corrosion resistance, MAO / LDH / MOFs has better corrosion resistance.

[0063] like Figure 4As shown in the photothermal curve, the photothermal temperature curve of the MAO sample finally rises to about 45°C, and the photothermal temperature of the MAO / LDH coating is about 48°C. This is because the effect of Fe in hydrotalcite (LDH) gives the coating certain photothermal properties, and the photothermal temperature after MAO / LDH / MOFs is increased to about 54°C compared with MAO / LDH. This is because the effect of PB makes its photothermal performance further improved compared with hydrotalcite. With this photothermal performance, this temperature can effectively kill bacteria, which provides a new direction for clinical sterilization and has new effectiveness for postoperative infection problems caused by multidrug resistance.

[0064] The photothermal temperature of the MAO / LDH coating in the composite coating provided by the present invention is between 40°C and 50°C, while the photothermal temperature of the LDH and MOFs composite coating after micro-arc oxidation is 60°C. After 16 days of hydrogen evolution, the annual corrosion rate of the micro-arc oxidation coating is 0.4, while the corrosion rate of the LDH and MOFs composite coating after micro-arc oxidation is 0.3. In summary, the medical magnesium alloy composite coating prepared by the preparation method of the present invention has excellent corrosion resistance and can effectively protect the magnesium alloy substrate.

[0065] The preparation method of the present invention combines the simple preparation technology of hydrotalcite with MOFs, and is prepared through a two-step hydrothermal method, so that their combined action produces photothermal properties; in addition, the thickness of the coating prepared by LDHs is not sufficient to ensure its corrosion resistance, so the preparation method of the present invention combines the hydrothermal method with the micro-arc oxidation method, while ensuring functional effectiveness, increasing the coating thickness and significantly improving its corrosion resistance.

[0066] Throughout this specification, terms such as "one embodiment" or "some embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0067] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a photothermal, antibacterial, and corrosion-resistant medical magnesium alloy composite coating, characterized in that: The steps include: Step 1, preprocessing; The Mg-Zn-Ca alloy sample is polished, cleaned and dried to obtain a sample to be used; Step 2: micro-arc oxidation treatment; An electrolyte was prepared, and the sample to be used was used as an anode, stainless steel was used as a cathode, and the MAO mode was set to a constant current mode to obtain a Mg-Zn-Ca alloy micro-arc oxidation coating; Step 3, hydrothermal preparation; (1) Ferric nitrate, magnesium nitrate, sodium carbonate, and sodium hydroxide are dissolved in water to prepare a hydrothermal treatment solution. The sample with the micro-arc oxidation coating obtained in step 2 and the hydrothermal treatment solution are transferred to a reactor and placed in a drying oven for hydrothermal reaction. After the reaction is completed, the sample is cooled to room temperature with the furnace. The sample is taken out and ultrasonically treated with anhydrous ethanol, and dried with cold air to obtain the MAO / LDH coating; (2) 0.2-1 g of ferric chloride and 0.2-5 g of sodium ferrocyanide were added to water to prepare a MOFs precursor solution. The MAO / LDH sample was placed vertically in a polytetrafluoroethylene-lined hydrothermal reactor. The MOFs precursor solution was then poured into the hydrothermal reactor. Finally, the reactor was placed in an oven for hydrothermal reaction. After the reaction was completed, the reactor was naturally cooled. The sample was taken out and placed in deionized water for ultrasonic treatment. After drying, the MAO / LDH / MOFs composite coating was obtained.

2. The method for preparing a photothermal, antibacterial, and corrosion-resistant medical magnesium alloy composite coating according to claim 1, characterized in that: In the step 3, the composition of the hydrothermal treatment solution is: 3-100 g / L of ferric nitrate, 6-100 g / L of magnesium nitrate, 1-10 g / L of sodium carbonate, and 2-60 g / L of sodium hydroxide.

3. The method for preparing a photothermal, antibacterial, and corrosion-resistant medical magnesium alloy composite coating according to claim 1, characterized in that: In the hydrothermal reactions (1) and (2) of step 3, the reaction temperature is 40-120° C., and the reaction time is 4-12 h.

4. The method for preparing a photothermal, antibacterial, and corrosion-resistant medical magnesium alloy composite coating according to claim 1, characterized in that: In the step 3, the ultrasonic treatment time of deionized water is 10 to 20 minutes.

5. The method for preparing a photothermal, antibacterial, and corrosion-resistant medical magnesium alloy composite coating according to claim 1, characterized in that: In the step 2, the electrolyte uses water as a solvent and is composed of 1-50 g / L sodium silicate, 1-50 g / L sodium hexametaphosphate, and 0.5-20 g / L sodium hydroxide.

6. The preparation method according to any one of claims 1 to 5, characterized in that The near infrared light response temperature rise curve of the magnesium alloy composite coating prepared by the preparation method is 0.6 w / cm 2 It is produced by near-infrared light excitation at a wavelength of 808 nm at low power.

7. A photothermal, antibacterial and corrosion-resistant medical magnesium alloy composite coating, characterized in that: The method according to any one of claims 1 to 6 is used for preparation.

8. The photothermal, antibacterial, and corrosion-resistant magnesium alloy composite coating according to claim 7, characterized in that: The phase components of the composite coating are magnesium oxide, magnesium silicate, magnesium hydroxide, hydrotalcite and MOFs.

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