A medical magnesium alloy material with tannic acid-optimized micro-arc oxidation film and its preparation method and application

Abstract

The application discloses a medical magnesium alloy material with tannic acid optimized micro-arc oxidation film sealing and a preparation method and application thereof, and belongs to the technical field of medical degradable metal surface modification. The medical magnesium alloy material comprises a medical magnesium alloy base body, a micro-arc oxidation ceramic layer is formed on the surface of the medical magnesium alloy base body, and a composite sealing layer is filled in the surface and micropores of the micro-arc oxidation ceramic layer; and the composite sealing layer comprises a tannic acid magnesium organic phase and a NaMgF3 inorganic phase. The tannic acid magnesium organic phase and the NaMgF3 inorganic phase are used to form the composite sealing layer filled in the surface and micropores of the micro-arc oxidation ceramic layer, so that the compactness of the medical magnesium alloy material is obviously improved, the corrosion resistance is greatly improved, the degradation rate is controllable, the composite sealing layer is excellent in biocompatibility and free of heavy metal residues, and the surface protection requirement of medical degradable implant devices such as orthopedic and cardiovascular devices is met. Meanwhile, the application is gentle and green and free of toxicity.

Description

Technical Field

[0001] This invention belongs to the field of surface modification technology for medical biodegradable metal materials, specifically relating to a medical magnesium alloy material with tannic acid-optimized micro-arc oxidation film sealing, its preparation method, and its application. Background Technology

[0002] In recent years, biodegradable metallic materials for medical use have attracted widespread attention in fields such as orthopedic implants, cardiovascular stents, and wound repair due to their good biocompatibility, suitable strength, and degradation cycle matching that of human tissue. Among them, magnesium alloys have become one of the most promising biodegradable implant materials because of their density being close to that of human bone tissue, excellent mechanical properties, biodegradability in vivo, and non-toxic and harmless degradation products. However, magnesium alloys are chemically reactive and are prone to rapid and uneven corrosion degradation in the human physiological environment. This causes the implant to lose its mechanical strength before tissue repair is completed, while also generating large amounts of hydrogen gas and alkaline products, leading to local inflammation, tissue irritation, and other problems, severely limiting their clinical application. Therefore, surface protection treatment of magnesium alloys to improve their corrosion resistance, biocompatibility, and structural stability has become a key technology in the research of biodegradable magnesium materials for medical use.

[0003] Currently, surface protection technologies for magnesium alloys mainly include anodizing, micro-arc oxidation, electrochemical deposition, and polymer coating. Among these, micro-arc oxidation (MAO) has become the most mainstream surface modification method for medical magnesium alloys because it can generate a high-hardness, high-adhesion ceramic oxide film on the surface of magnesium alloys in situ, significantly improving the corrosion resistance and wear resistance of the substrate. However, MAO films inherently have a porous structure with numerous through-holes and microcracks. Under physiological conditions, bodily fluids can still penetrate through these pores to the substrate interface, leading to a rapid decline in the protective effect of the film and making it difficult to achieve long-term stable corrosion control. Therefore, subsequent sealing treatment of the MAO film to close surface defects and increase film density is a necessary step to further improve the long-term reliability of medical magnesium alloys. However, traditional sealing agents often have drawbacks such as high toxicity, poor biocompatibility, and complex processes, making them unsuitable for the stringent standards of biodegradable medical materials. Therefore, developing a method for sealing magnesium alloy micro-arc oxidation films that combines good sealing effect, high bonding strength, excellent biosafety, and simple and reliable process has significant scientific research value and clinical application prospects. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a medical magnesium alloy material with tannic acid-optimized micro-arc oxidation film sealing, its preparation method and application, so as to solve the technical problems of poor bonding strength and biocompatibility of the sealing layer of existing magnesium alloy materials, as well as poor corrosion resistance due to poor sealing effect.

[0005] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a medical magnesium alloy material with tannic acid-optimized micro-arc oxidation film for sealing pores, comprising a medical magnesium alloy substrate, wherein a micro-arc oxidation ceramic layer is formed on the surface of the medical magnesium alloy substrate, and a composite sealing layer is filled on the surface and in the micropores of the micro-arc oxidation ceramic layer; the composite sealing layer comprises a magnesium tannic acid organic phase and a NaMgF3 inorganic phase.

[0006] Preferably, the main phase composition of the micro-arc oxidation ceramic layer includes magnesium oxide and magnesium fluoride, and the thickness is 10 μm to 15 μm.

[0007] Preferably, the medical magnesium alloy matrix includes one of Mg-Zn-Ca magnesium alloy, Mg-Zn magnesium alloy and Mg-Ca magnesium alloy.

[0008] This invention also provides a method for preparing the medical magnesium alloy material with tannic acid-optimized micro-arc oxidation film for pore sealing, comprising the following steps: Provides medical-grade magnesium alloy matrix; A micro-arc oxidation ceramic layer is formed on the surface of the medical magnesium alloy substrate; The sealing solution is brought into contact with the medical magnesium alloy substrate on which the micro-arc oxidation ceramic layer is formed, and an in-situ sealing reaction is carried out. Intertwined magnesium tannate organic phase and NaMgF3 inorganic phase are generated in situ on the surface and micropores of the micro-arc oxidation ceramic layer to form a composite sealing layer, thereby obtaining medical magnesium alloy material.

[0009] Preferably, the formation process of the composite sealing layer is as follows: the medical magnesium alloy substrate on which the micro-arc oxidation ceramic layer is formed is immersed in the sealing treatment solution, and the substrate is immersed at a constant temperature of 45~55℃ for 30~60 minutes to carry out the in-situ sealing reaction, and then rinsed and dried; the sealing treatment solution includes sodium fluoride, tannic acid, borax and deionized water, wherein the sodium fluoride, tannic acid and borax account for 0.8%~1.4%, 0.3%~0.9% and 0.1%~0.4% of the mass of the deionized water, respectively.

[0010] More preferably, during the formation of the composite sealing layer, the drying conditions are: drying at 60 to 80°C for 30 minutes; during the in-situ sealing reaction, magnesium ions react with sodium ions and fluoride ions in the solution to generate the NaMgF3 inorganic phase; tannic acid simultaneously chelates with magnesium ions to form the magnesium tannate organic phase, and under the induction of tannic acid, the NaMgF3 inorganic phase crystallizes uniformly to form a two-phase interwoven filling micropore.

[0011] Preferably, the pH value of the sealing solution is 7.0 to 9.0, and it is adjusted using sodium hydroxide.

[0012] More preferably, the sealing solution is prepared by adding 8-12 g / L NaF, 3-8 g / L tannic acid and 1-2 g / L borax to 1 L of deionized water.

[0013] Preferably, the formation process of the micro-arc oxidation ceramic layer is as follows: the medical magnesium alloy substrate is placed in an electrolyte, and the electrolyte temperature is controlled below 40°C at a forward voltage of 320~380V, a frequency of 500Hz, and a duty cycle of 15% for 10~15 minutes, followed by rinsing and drying; the electrolyte comprises sodium silicate, sodium fluoride, sodium phosphate, and deionized water, wherein the sodium silicate, sodium fluoride, and sodium phosphate account for 1.0%, 0.3%, and 0.5% of the mass of the deionized water, respectively.

[0014] More preferably, the electrolyte is prepared by adding 10 g / L sodium silicate, 3 g / L sodium fluoride, and 5 g / L sodium phosphate to deionized water.

[0015] Preferably, the pretreatment of the medical magnesium alloy matrix includes the following steps: 1) Place the medical magnesium alloy substrate in an alkaline degreasing solution and immerse it at a constant temperature for 10 minutes; 2) Pickle the medical magnesium alloy substrate obtained in step 1) at room temperature; 3) Rinse and dry the medical magnesium alloy substrate obtained in step 2).

[0016] Preferably, the alkaline degreasing solution is prepared from sodium hydroxide and sodium carbonate, wherein the concentration of sodium hydroxide in the alkaline degreasing solution is 20 g / L to 60 g / L, the concentration of sodium carbonate is 10 g / L to 40 g / L, and the remainder is water.

[0017] In a further preferred embodiment, in the pretreatment of the medical magnesium alloy substrate, in step 2), the medical magnesium alloy substrate obtained in step 1) is acid-washed and activated with an 8% (v / v) dilute phosphoric acid solution at room temperature to remove surface oxide scale and impurities; in step 3), the medical magnesium alloy substrate obtained in step 2) is rinsed three times with deionized water and dried with cold air.

[0018] The present invention also provides the application of the aforementioned medical magnesium alloy material in the preparation of biodegradable medical implants.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a medical magnesium alloy material with tannic acid-optimized micro-arc oxidation film sealing. Compared with an unsealed micro-arc oxidation sample, in the medical magnesium alloy material of this invention, tannic acid and Mg²⁺ in the micro-arc oxidation ceramic layer are more effectively sealed. +In-situ chelation reaction is performed on the surface and micropores of the micro-arc oxidation ceramic layer to generate magnesium tannate organic phase. The magnesium tannate organic phase and the NaMgF3 inorganic phase synergistically fill the surface and micropores of the micro-arc oxidation ceramic layer, significantly improving the density of the medical magnesium alloy material. This effectively blocks the intrusion channels of corrosive media and significantly reduces the self-corrosion current density of the medical magnesium alloy material. Experiments show that the corrosion current density of the medical magnesium alloy material of this invention can be reduced to 10. -7 ~10 -8 A / cm 2 The corrosion potential increases to -1.3 to -1.1 V (V SCE). -1 The electrochemical impedance modulus has been increased to 20,000-40,000 Ω. cm 2 Meanwhile, tannic acid, as a natural biomass material, is non-toxic and non-irritating. It bonds tightly with the micro-arc oxidation ceramic membrane through coordination bonds, significantly improving the bonding strength between the composite sealing layer and the medical magnesium alloy substrate. This makes the coating formed by the medical magnesium alloy substrate, the micro-arc oxidation ceramic layer, and the composite sealing layer less prone to peeling and highly stable. Furthermore, tannic acid itself possesses excellent bioactivity and biocompatibility, promoting cell adhesion and proliferation, enhancing the bone integration capacity of medical magnesium alloy materials, and meeting the biosafety requirements of medical implants. As a widely available, green, non-toxic, and highly biocompatible natural polyphenol compound, its molecular structure is rich in phenolic hydroxyl groups, allowing for strong coordination with metals and metal oxides. It also possesses good film-forming properties, wettability, and bioactivity, making it ideal for surface modification of medical materials. Experiments show that the cell survival rate of the medical magnesium alloy material of this invention is not less than 85%, and it has no obvious cytotoxicity. Furthermore, the surface and micropores of the micro-arc oxidation ceramic layer are effectively filled by a composite phase composed of magnesium tannate organic phase and NaMgF3 inorganic phase, with a surface contact angle of 30°~60°, exhibiting good hydrophilicity and biocompatibility. This medical magnesium alloy material does not contain chloride ions and has no cytotoxicity, hemolytic reaction, or inflammatory stimulation.

[0020] Furthermore, in the micro-arc oxidation ceramic layer, magnesium oxide is its intrinsic ceramic phase, providing film hardness and insulation. Magnesium fluoride itself has a much lower solubility in the physiological environment than magnesium oxide, enabling it to form the first corrosion-resistant barrier within the micro-arc oxidation ceramic layer itself. This prevents the micro-arc oxidation ceramic layer from being merely a physical barrier and still chemically susceptible to corrosion by Cl. -The issue of penetration. The lower limit of the thickness of the micro-arc oxidation ceramic layer is 10 μm: to ensure that the ceramic layer body has sufficient thickness to block the corrosive medium from reaching the magnesium alloy substrate before the micropores / microcracks formed by micro-arc discharge are completely sintered and closed. Otherwise, the composite sealing layer would have to bear the barrier function alone, which would be too heavy a load. The upper limit is 15 μm: as the thickness of the micro-arc oxidation film increases, the internal stress increases and the tendency for brittle fracture increases. Excessive thickness may induce macro-cracks, which become shortcuts for corrosion. At the same time, it is easy to cause insufficient exchange of reaction liquid at the bottom of deep holes and uneven in-situ formation.

[0021] Furthermore, among the medical magnesium alloy matrix, the three types of alloys, namely Mg-Zn-Ca series magnesium alloy, Mg-Zn series magnesium alloy and Mg-Ca series magnesium alloy, are all essential trace element systems for the human body: Zn participates in bone metabolism and enzyme activity, Ca is the main component of bone matrix, and the biosafety of degradation products is higher than that of industrial magnesium alloys containing Al and RE (rare earth), which is in line with the medical application. Solid solution strengthening and dynamic precipitation (MgZn2 phase) of Zn in magnesium matrix can refine grains, and Ca precipitation of Mg2Ca phase further strengthens the matrix, so that the mechanical properties of the matrix meet the implant load-bearing requirements. Chemical compatibility with the sealing layer: Zn and Ca do not form competitive chelation interference in the sealing solution—tannic acid preferentially binds with Mg. 2+ Chelation to form magnesium tannate, Zn 2+ / Ca 2+ It is basically retained on the substrate side and will not compete for the sealing reaction path; Mg-Ca degradation products contain Ca, which can promote calcium and phosphorus deposition at the implantation interface and aid in bone integration; Mg-Zn degradation products contain Zn. 2+ The sustained-release formula has a certain antibacterial effect, which is superimposed on the antibacterial effect of tannic acid.

[0022] This invention also provides a method for preparing a medical magnesium alloy material with tannic acid-optimized micro-arc oxidation film for pore sealing. The method involves contacting a sealing solution with a medical magnesium alloy substrate having the micro-arc oxidation ceramic layer formed thereon to perform an in-situ sealing reaction. This generates an interwoven organic phase of magnesium tannic acid and an inorganic phase of NaMgF3. The magnesium tannic acid organic phase and the NaMgF3 inorganic phase are co-deposited in the same reaction space, with the organic phase connected to the inorganic phase and the inorganic phase embedded within the organic phase. This interwoven structure eliminates the obvious organic / inorganic separation layers in the composite sealing layer, significantly reducing the risk of interlayer delamination compared to simple organic and inorganic layer stacks. Combining micro-arc oxidation with chemical conversion allows the fluidity of the conversion solution to penetrate into the micropores and undergo an in-situ reaction, achieving effective pore sealing. Furthermore, this in-situ sealing reaction is carried out under mild conditions without stirring, pressurization, or ultraviolet light, ensuring that the sealing process does not damage the structure of the micro-arc oxidation ceramic film substrate.

[0023] Furthermore, during the formation of the composite sealing layer, Mg² + Na+ F - In-situ reactions occur on the surface and inside the micropores of the micro-arc oxidation ceramic layer, generating an inorganic sealing phase of NaMgF3; tannic acid reacts with Mg... 2+ An in-situ chelation reaction occurs on the micropore wall to generate a magnesium tannate organic sealing phase, which interweaves to achieve effective pore sealing. The F in sodium fluoride... - With Mg 2+ The reaction produces an inorganic phase, NaMgF3, with a lower limit of 0.8% ensuring the presence of F within the micropores. - The concentration is sufficient to drive NaMgF3 nucleation; the upper limit of 1.4% prevents F - Excessive attack on the substrate (F) - (It has an etching effect on magnesium; excessively high concentrations can actually enlarge micropores during the sealing stage.) A lower limit of 0.3% for tannic acid ensures sufficient chelation reaction on the inner wall of the micropores, preventing incomplete pore sealing. An upper limit of 0.9% prevents tannic acid from undergoing self-oxidation and polymerization in weakly alkaline hydrothermal solutions, forming loose aggregates that clog the pore openings, resulting in voids and poor sealing. Borate ions in borax can react with magnesium... 2+ Formation of weak complexes, regulating Mg 2+ The rate of dissolution from the arc-oxidized ceramic layer matches the deposition rate of magnesium tannate and NaMgF3, which is conducive to the formation of an interwoven structure of the organic phase of magnesium tannate and the inorganic phase of NaMgF3. Its mass percentage of 0.1% to 0.4% is beneficial to maintaining pH stability.

[0024] Furthermore, the chelating active species of tannic acid is the phenoxy anion (O2). - pH increases → Deprotonation increases → O - The proportion increases → with Mg 2+ The coordination ability is enhanced; however, at pH < 7.0, tannic acid mainly exists in the form of phenol-OH, with weak chelating power, low magnesium tannate yield, and incomplete pore sealing; at pH > 9.0, on the one hand, there is an excessive amount of tannic acid phenol-oxygen anions, and O2 in the aqueous solution oxidizes tannic acid (polyphenol → quinone), leading to inactivation; on the other hand, Mg 2+ Under strong alkaline conditions, Mg(OH)₂ precipitate is preferentially formed, competing with the formation pathways of magnesium tannin and NaMgF₃. Furthermore, Mg(OH)₂ exhibits poor corrosion resistance in physiological environments, negatively impacting performance. The chelation window for tannin is 7.0–9.0 °C, which is also the chelation window for Mg. 2+ The optimal range for preventing premature precipitation and alkali corrosion of the substrate; in addition, the buffering capacity of borax plays its role in this range, ensuring that the pH drift is ≤0.5 within 60 min of reaction, thus guaranteeing batch stability.

[0025] 45~55℃ / 30~60 min: Temperature <45℃: Tannic acid chelation kinetics are too slow, and the reaction does not penetrate deep pores within 30 min; Temperature >55℃: Oxidation of tannic acid phenol groups is accelerated, and Mg2+ If dissolution is too rapid, Mg(OH)2 will precipitate and form a crust at the orifice, blocking the penetration of the drug solution into the deep pores; Time <30 min: The reaction at the bottom of the deep hole is not complete; >60 min: Diminishing marginal benefits, and the substrate is at risk of excessive corrosion after prolonged immersion in weak alkaline solution.

[0026] Furthermore, the roles of the various components of the electrolyte during the formation of the micro-arc oxidation ceramic layer are as follows: Sodium silicate (1.0%): SiO3 2- Under high temperature and high pressure in the discharge channel, it decomposes into SiO2 and forms a MgO-SiO2 composite ceramic phase with MgO, thereby forming a micro-arc oxidation ceramic layer, which improves the density and impedance of the micro-arc oxidation ceramic layer; 1.0% mass ratio is the balance point between the growth rate of the micro-arc oxidation ceramic layer and the conductivity of the solution (too low a mass ratio results in a thin micro-arc oxidation ceramic layer, too high a mass ratio results in high solution viscosity and unstable arc initiation). Sodium fluoride (0.3%): F - MgF2 is generated by entering the micro-arc oxidation ceramic layer, while F - It has a micro-etching-repassivation effect on the discharge channel, refining the pore size distribution; Sodium phosphate (0.5%): PO4 3- The addition of trace amounts of Mg3(PO4)2 enhances biological activity; at the same time, phosphate ions regulate the conductivity of the solution, making the discharge more uniform. 320~380V: Below 320V, the discharge energy is insufficient, the micro-arc oxidation ceramic layer is thin and the micropores are not fully opened, which easily leads to the inability of subsequent sealing solution to penetrate; above 380V, the arc is too large, and the micro-arc oxidation ceramic layer will have ablation macropores, which cannot be filled by sealing. 500Hz / 15% duty cycle: High-frequency short pulses make the discharge points dense and the micropores small and uniform, which is conducive to in-situ interwoven sealing. Otherwise, if the pore size is too large, the NaMgF3 crystals will not fill properly, and if the pore size is too small, the sealing solution will not be able to enter. 10~15 min: It is conducive to obtaining a micro-arc oxidation ceramic layer with a thickness of 10μm~15μm.

[0027] Furthermore, in the pretreatment steps of the medical magnesium alloy substrate, step 1) alkaline degreasing and constant temperature soaking for 10 minutes: This helps to remove processing oil and organic contaminants from the surface of the medical magnesium alloy substrate. Otherwise, uneven discharge at oil spots during the arc ignition of the micro-arc oxidation ceramic film will result in localized thin films or perforations, easily leading to leakage; Step 2) room temperature acid washing: This helps to remove the native MgO / Mg(OH)2 natural oxide film of the medical magnesium alloy substrate, exposing a clean magnesium substrate and ensuring the consistency of the arc ignition of the micro-arc oxidation ceramic film. If the natural oxide film remains, the micro-arc discharge will preferentially break down at the weak points of the film, resulting in a dispersed film thickness distribution; Step 3) rinsing and drying: This helps to prevent residual liquid from steps 1) and 2) from being carried into the electrolyte and causing contamination (especially Cl). -If residue remains, pinholes will appear in the micro-arc oxidation ceramic film.

[0028] Furthermore, in the alkaline degreasing solution, the concentration of NaOH is 20 g / L ~ 60 g / L: primarily targeting the saponification of greases; too low a concentration will result in incomplete degreasing, while too high a concentration will cause the surface of the medical magnesium alloy substrate to pulverize (magnesium still reacts slowly in strong alkali: Mg + 2H2O → Mg(OH)2 + H2↑, excess alkali accelerates this reaction); the concentration of Na2CO3 is 10 g / L ~ 40 g / L: the hydrolysis of carbonate ions in it provides OH-. - It acts as a buffer, inhibiting excessive corrosion of magnesium by NaOH, while sodium carbonate also has a dispersing and emulsifying effect, preventing the detached oil from being re-adsorbed. The combination of the two has a higher degreasing efficiency than NaOH alone, and the erosion rate of the magnesium matrix is ​​controlled within an acceptable range (10 min of treatment will not result in significant weight loss).

[0029] This invention also provides the application of medical-grade magnesium alloy materials in the preparation of biodegradable medical implants. Tannic acid itself has antibacterial, antioxidant, and endothelialization-promoting effects, which are not found in traditional sealing agents (silane, boiling water, rare earth elements), making this material particularly suitable for bone implantation and scenarios where infection may occur; furthermore, the matrix is ​​biodegradable, the sealing agent is biodegradable, and the degradation products (Mg...) 2+ Zn 2+ Ca 2 + (Tanic acid metabolites) are all metabolizable by the human body, so they meet the regulatory requirements for biodegradable implants. Attached Figure Description

[0030] Figure 1 This is a flowchart of the preparation process of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to understand the features and effects of the present invention, the following descriptions and definitions are only general descriptions of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in the event of any conflict, the definitions in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0033] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0034] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0035] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0036] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0037] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents parts by weight, and "ratio" represents weight proportion.

[0038] Example 1 like Figure 1 As shown, a medical magnesium alloy material for sealing pores using tannic acid-optimized micro-arc oxidation film includes a medical magnesium alloy substrate, a micro-arc oxidation ceramic layer, and a tannic acid-NaMgF3 composite sealing layer. The substrate magnesium alloy is Mg-5Zn-1Ca. The sealing solution comprises sodium fluoride, tannic acid, and borax at 0.8%, 0.3%, and 0.1% of the deionized water mass, respectively. The electrolyte comprises sodium silicate, sodium fluoride, and sodium phosphate at 1.0%, 0.3%, and 0.5% of the deionized water mass, respectively.

[0039] Preparation method: First, the magnesium alloy was immersed in an alkaline degreasing solution prepared with sodium hydroxide and sodium carbonate for 10 minutes at a constant temperature to remove surface oil. The alkaline degreasing solution was prepared with sodium hydroxide and sodium carbonate, with a sodium hydroxide concentration of 20 g / L, a sodium carbonate concentration of 10 g / L, and the remainder being water. Then, it was activated by acid washing with an 8% (v / v) dilute phosphoric acid solution at room temperature to remove surface oxide scale and impurities. Finally, it was rinsed three times with deionized water and dried with cold air. The micro-arc oxidation ceramic film was prepared by using deionized water as a solvent and sequentially adding sodium silicate, sodium fluoride, and sodium phosphate to obtain an electrolyte. The magnesium alloy substrate was used as the anode, and the stainless steel plate was used as the cathode. Both the cathode and anode were completely immersed in the electrolyte at room temperature. The forward voltage was set to 320 V, the frequency to 500 Hz, the duty cycle to 15%, and the electrolyte temperature was controlled to be below 40℃. After 10 minutes of treatment, an 11 μm porous micro-arc oxidation ceramic film with magnesium oxide and magnesium fluoride as the main phases was generated in situ on the magnesium alloy surface. Next, a sealing solution was prepared using deionized water as the solvent. Sodium fluoride, tannic acid, and borax were added sequentially, and the pH was adjusted to 7.0-9.0 with sodium hydroxide. The solution was stirred thoroughly and set aside. The magnesium alloy sample with the micro-arc oxide film was completely immersed in the sealing solution and incubated at 45 °C for 45 min for in-situ sealing. During this process, magnesium ions dissolved from the film reacted with sodium and fluoride ions in the solution to form NaMgF3 inorganic microcrystals. Tannic acid simultaneously chelated with magnesium ions to form magnesium tannate organic phase. Under the induction of tannic acid, NaMgF3 crystallized uniformly, and the two phases intertwined to fill the micropores. X-ray diffraction (XRD) was used to characterize the crystalline inorganic phase composition of the film. By comparing with standard PDF cards, the NaMgF3 inorganic crystalline phase within the sealing layer was identified. Fourier transform infrared spectroscopy (FTIR) was used to identify the coordination characteristic peaks of tannic acid functional groups, confirming the presence of the magnesium tannate organic phase. Finally, the sample was taken out and rinsed twice with deionized water, and dried in an oven at 60 ℃ for 30 min to obtain a dense composite sealing layer.

[0040] According to the relevant standards for performance testing of medical magnesium alloy materials, the performance of the samples after tannic acid-optimized micro-arc oxidation film sealing treatment was characterized. Electrochemical performance tests were performed on the samples according to GB / T 19292.1-2018 "Metals and Alloys - Corrosion Resistance Test Methods for Corrosion Coatings". Before conducting the simulated body fluid immersion test, the samples were dried at 60℃ to reduce the interference of moisture and impurities on the experimental results.

[0041] Example 2 A medical-grade magnesium alloy material for micro-arc oxidation film sealing with tannic acid optimization includes a medical-grade magnesium alloy substrate, a micro-arc oxidation ceramic layer, and a tannic acid-NaMgF3 composite sealing layer. The magnesium alloy substrate is Mg-2Zn-0.5Ca. The sealing solution comprises sodium fluoride, tannic acid, and borax at 1%, 0.5%, and 0.2% of the deionized water mass, respectively. The electrolyte comprises sodium silicate, sodium fluoride, and sodium phosphate at 1.0%, 0.3%, and 0.5% of the deionized water mass, respectively.

[0042] Preparation method: First, the magnesium alloy was immersed in an alkaline degreasing solution prepared with sodium hydroxide and sodium carbonate for 10 minutes at a constant temperature to remove surface oil. The alkaline degreasing solution was prepared with sodium hydroxide and sodium carbonate, with a sodium hydroxide concentration of 40 g / L, a sodium carbonate concentration of 30 g / L, and the remainder being water. Then, it was activated by acid washing with an 8% (v / v) dilute phosphoric acid solution at room temperature to remove surface oxide scale and impurities. Finally, it was rinsed three times with deionized water and dried with cold air. The micro-arc oxidation ceramic film was prepared by using deionized water as a solvent and sequentially adding sodium silicate, sodium fluoride, and sodium phosphate to obtain an electrolyte. The magnesium alloy substrate was used as the anode, and the stainless steel plate was used as the cathode. Both the cathode and anode were completely immersed in the electrolyte at room temperature. The forward voltage was set to 380 V, the frequency to 500 Hz, the duty cycle to 15%, and the electrolyte temperature was controlled to be below 40℃. After 12 minutes of treatment, a 12 μm porous micro-arc oxidation ceramic film with magnesium oxide and magnesium fluoride as the main phases was generated in situ on the magnesium alloy surface. Next, a sealing solution was prepared using deionized water as the solvent. Sodium fluoride, tannic acid, and borax were added sequentially, and the pH was adjusted to 7.0-9.0 with sodium hydroxide. The solution was stirred thoroughly and set aside. The magnesium alloy sample with the micro-arc oxide film was completely immersed in the sealing solution and incubated at 50 °C for 30 min for in-situ sealing. During this process, magnesium ions dissolved from the film reacted with sodium and fluoride ions in the solution to form NaMgF3 inorganic microcrystals. Tannic acid simultaneously chelated with magnesium ions to form magnesium tannate organic phase. Under the induction of tannic acid, NaMgF3 crystallized uniformly, and the two phases intertwined to fill the micropores. X-ray diffraction (XRD) was used to characterize the crystalline inorganic phase composition of the film. By comparing with standard PDF cards, the NaMgF3 inorganic crystalline phase within the sealing layer was identified. Fourier transform infrared spectroscopy (FTIR) was used to identify the coordination characteristic peaks of tannic acid functional groups, confirming the presence of the magnesium tannate organic phase. Finally, the sample was taken out and rinsed twice with deionized water, and dried in an oven at 60 ℃ for 30 min to obtain a dense composite sealing layer.

[0043] According to the relevant standards for performance testing of medical magnesium alloy materials, the performance of the samples after tannic acid-optimized micro-arc oxidation film sealing treatment was characterized. Electrochemical performance tests were performed on the samples according to GB / T 19292.1-2018 "Metals and Alloys - Corrosion Resistance Test Methods for Corrosion Coatings". Before conducting the simulated body fluid immersion test, the samples were dried at 60℃ to reduce the interference of moisture and impurities on the experimental results.

[0044] Example 3 A medical-grade magnesium alloy material for micro-arc oxidation film sealing with tannic acid optimization includes a medical-grade magnesium alloy substrate, a micro-arc oxidation ceramic layer, and a tannic acid-NaMgF3 composite sealing layer. The magnesium alloy substrate is Mg-6Ca-0.5Zr. The sealing solution comprises sodium fluoride, tannic acid, and borax at 1.2%, 0.7%, and 0.3% of the deionized water mass, respectively. The electrolyte comprises sodium silicate, sodium fluoride, and sodium phosphate at 1.0%, 0.3%, and 0.5% of the deionized water mass, respectively.

[0045] Preparation method: First, the magnesium alloy was immersed in an alkaline degreasing solution prepared with sodium hydroxide and sodium carbonate for 10 minutes at a constant temperature to remove surface oil. The alkaline degreasing solution was prepared with sodium hydroxide and sodium carbonate, with a sodium hydroxide concentration of 60 g / L, a sodium carbonate concentration of 40 g / L, and the remainder being water. Then, it was activated by acid washing with an 8% (v / v) dilute phosphoric acid solution at room temperature to remove surface oxide scale and impurities. Finally, it was rinsed three times with deionized water and dried with cold air. The micro-arc oxidation ceramic film was prepared by using deionized water as a solvent and sequentially adding sodium silicate, sodium fluoride, and sodium phosphate to obtain an electrolyte. The magnesium alloy substrate was used as the anode, and the stainless steel plate was used as the cathode. Both the cathode and anode were completely immersed in the electrolyte at room temperature. The forward voltage was set to 320 V, the frequency to 500 Hz, the duty cycle to 15%, and the electrolyte temperature was controlled to be below 40℃. After 15 minutes of treatment, a 13 μm porous micro-arc oxidation ceramic film with magnesium oxide and magnesium fluoride as the main phases was generated in situ on the magnesium alloy surface. Next, a sealing solution was prepared using deionized water as the solvent. Sodium fluoride, tannic acid, and borax were added sequentially, and the pH was adjusted to 7.0-9.0 with sodium hydroxide. The solution was stirred thoroughly and set aside. The magnesium alloy sample with the micro-arc oxide film was completely immersed in the sealing solution and incubated at 55 °C for 30 min for in-situ sealing. During the process, magnesium ions dissolved from the film reacted with sodium and fluoride ions in the solution to form NaMgF3 inorganic microcrystals. Tannic acid simultaneously chelated with magnesium ions to form magnesium tannate organic phase. Under the induction of tannic acid, NaMgF3 crystallized uniformly, and the two phases intertwined to fill the micropores. X-ray diffraction (XRD) was used to characterize the crystalline inorganic phase composition of the film. By comparing with standard PDF cards, the NaMgF3 inorganic crystalline phase within the sealing layer was identified. Fourier transform infrared spectroscopy (FTIR) was used to identify the coordination characteristic peaks of tannic acid functional groups, confirming the presence of the magnesium tannate organic phase. Finally, the sample was taken out and rinsed twice with deionized water, and dried in an oven at 60 ℃ for 30 min to obtain a dense composite sealing layer.

[0046] According to the relevant standards for performance testing of medical magnesium alloy materials, the performance of the samples after tannic acid-optimized micro-arc oxidation film sealing treatment was characterized. Electrochemical performance tests were performed on the samples according to GB / T 19292.1-2018 "Metals and Alloys - Corrosion Resistance Test Methods for Corrosion Coatings". Before conducting the simulated body fluid immersion test, the samples were dried at 60℃ to reduce the interference of moisture and impurities on the experimental results.

[0047] Example 4 A medical-grade magnesium alloy material for micro-arc oxidation film sealing with tannic acid optimization includes a medical-grade magnesium alloy substrate, a micro-arc oxidation ceramic layer, and a tannic acid-NaMgF3 composite sealing layer. The magnesium alloy substrate is Mg-6Zn-0.5Zr. The sealing solution comprises sodium fluoride, tannic acid, and borax at 1.4%, 0.9%, and 0.4% of the deionized water mass, respectively. The electrolyte comprises sodium silicate, sodium fluoride, and sodium phosphate at 1.0%, 0.3%, and 0.5% of the deionized water mass, respectively.

[0048] Preparation method: First, the magnesium alloy was immersed in an alkaline degreasing solution prepared with sodium hydroxide and sodium carbonate for 10 minutes at a constant temperature to remove surface oil. The alkaline degreasing solution was prepared with sodium hydroxide and sodium carbonate, with a sodium hydroxide concentration of 20 g / L, a sodium carbonate concentration of 10 g / L, and the remainder being water. Then, it was activated by acid washing with an 8% (v / v) dilute phosphoric acid solution at room temperature to remove surface oxide scale and impurities. Finally, it was rinsed three times with deionized water and dried with cold air. The micro-arc oxidation ceramic film was prepared by using deionized water as a solvent and sequentially adding sodium silicate, sodium fluoride, and sodium phosphate to obtain an electrolyte. The magnesium alloy substrate material was used as the anode, and the stainless steel plate was used as the cathode. Both the cathode and anode were completely immersed in the electrolyte at room temperature. The forward voltage was set to 320 V, the frequency to 500 Hz, the duty cycle to 15%, and the electrolyte temperature was controlled to be below 40℃. After 10 minutes of treatment, a 15 μm porous micro-arc oxidation ceramic film with magnesium oxide and magnesium fluoride as the main phases was generated in situ on the magnesium alloy surface. Next, a sealing solution was prepared using deionized water as the solvent. Sodium fluoride, tannic acid, and borax were added sequentially, and the pH was adjusted to 7.0-9.0 with sodium hydroxide. The solution was stirred thoroughly and set aside. The magnesium alloy sample with the micro-arc oxide film was completely immersed in the sealing solution and incubated at 45 °C for 60 min for in-situ sealing. During the process, magnesium ions dissolved from the film reacted with sodium and fluoride ions in the solution to form NaMgF3 inorganic microcrystals. Tannic acid simultaneously chelated with magnesium ions to form magnesium tannate organic phase. Under the induction of tannic acid, NaMgF3 crystallized uniformly, and the two phases intertwined to fill the micropores. X-ray diffraction (XRD) was used to characterize the crystalline inorganic phase composition of the film. By comparing with standard PDF cards, the NaMgF3 inorganic crystalline phase within the sealing layer was identified. Fourier transform infrared spectroscopy (FTIR) was used to identify the coordination characteristic peaks of tannic acid functional groups, confirming the presence of the magnesium tannate organic phase. Finally, the sample was taken out and rinsed twice with deionized water, and dried in an oven at 60 ℃ for 30 min to obtain a dense composite sealing layer.

[0049] According to the relevant standards for performance testing of medical magnesium alloy materials, the performance of the samples after tannic acid-optimized micro-arc oxidation film sealing treatment was characterized. Electrochemical performance tests were performed on the samples according to GB / T 19292.1-2018 "Metals and Alloys - Corrosion Resistance Test Methods for Corrosion Coatings". Before conducting the simulated body fluid immersion test, the samples were dried at 60℃ to reduce the interference of moisture and impurities on the experimental results.

[0050] Table 1 shows the performance characterization results of the medical magnesium alloy materials prepared in Examples 1-4.

[0051] Table 1

[0052] As shown in Table 1 above, the corrosion current density of the medical magnesium alloy material prepared by this method can be reduced to 10. -7 ~10 - 8 A / cm 2 The corrosion potential increases to -1.3 to -1.1 V (V SCE). -1 The electrochemical impedance modulus has been increased to 20,000-40,000 Ω. cm 2 The cell survival rate is not less than 85%, and there is no obvious cytotoxicity. The micropores on the membrane surface are effectively filled by the NaMgF3 and magnesium tannate composite phase, and the surface contact angle is 30°~60°, which has good hydrophilicity and biocompatibility.

[0053] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A medical magnesium alloy material for sealing pores in a micro-arc oxidation film optimized with tannic acid, characterized in that, The invention includes a medical magnesium alloy substrate, on the surface of which a micro-arc oxidation ceramic layer is formed, and the surface and micropores of the micro-arc oxidation ceramic layer are filled with a composite sealing layer; the composite sealing layer comprises a magnesium tannate organic phase and a NaMgF3 inorganic phase.

2. The medical magnesium alloy material for pore sealing using tannic acid-optimized micro-arc oxidation film according to claim 1, characterized in that, The main phase components of the micro-arc oxidation ceramic layer include magnesium oxide and magnesium fluoride, and the thickness is 10 μm ~ 15 μm.

3. The medical magnesium alloy material for sealing pores with tannic acid-optimized micro-arc oxidation film according to claim 1 or 2, characterized in that, The medical magnesium alloy matrix includes one of Mg-Zn-Ca magnesium alloy, Mg-Zn magnesium alloy and Mg-Ca magnesium alloy.

4. A method for preparing a medical magnesium alloy material with tannic acid-optimized micro-arc oxidation film for pore sealing as described in any one of claims 1-3, characterized in that, Includes the following steps: Provides medical-grade magnesium alloy matrix; A micro-arc oxidation ceramic layer is formed on the surface of the medical magnesium alloy substrate; The sealing solution is brought into contact with the medical magnesium alloy substrate on which the micro-arc oxidation ceramic layer is formed, and an in-situ sealing reaction is carried out. Intertwined magnesium tannate organic phase and NaMgF3 inorganic phase are generated in situ on the surface and micropores of the micro-arc oxidation ceramic layer to form a composite sealing layer, thereby obtaining medical magnesium alloy material.

5. The preparation method according to claim 4, characterized in that, The process of forming the composite sealing layer is as follows: the medical magnesium alloy substrate on which the micro-arc oxidation ceramic layer is formed is immersed in the sealing treatment solution and soaked at a constant temperature of 45~55℃ for 30~60 minutes to carry out the in-situ sealing reaction. The sealing treatment solution includes sodium fluoride, tannic acid, borax and deionized water. The sodium fluoride, tannic acid and borax account for 0.8%~1.4%, 0.3%~0.9% and 0.1%~0.4% of the mass of the deionized water, respectively.

6. The preparation method according to claim 5, characterized in that, The pH value of the sealing solution is 7.0~9.

0.

7. The preparation method according to claim 6, characterized in that, The formation process of the micro-arc oxidation ceramic layer is as follows: the medical magnesium alloy substrate is placed in an electrolyte, and the electrolyte is treated for 10-15 minutes at a forward voltage of 320-380V, a frequency of 500Hz, a duty cycle of 15%, and a temperature below 40℃. The electrolyte consists of sodium silicate, sodium fluoride, sodium phosphate, and deionized water, wherein the sodium silicate, sodium fluoride, and sodium phosphate account for 1.0%, 0.3%, and 0.5% of the mass of the deionized water, respectively.

8. The preparation method according to claim 4, characterized in that, The pretreatment of the medical magnesium alloy matrix includes the following steps: 1) Place the medical magnesium alloy substrate in an alkaline degreasing solution and immerse it at a constant temperature for 10 minutes; 2) Pickle the medical magnesium alloy substrate obtained in step 1) at room temperature; 3) Rinse and dry the medical magnesium alloy substrate obtained in step 2).

9. The preparation method according to claim 8, characterized in that, The alkaline degreasing solution is prepared from sodium hydroxide and sodium carbonate. The concentration of sodium hydroxide in the alkaline degreasing solution is 20 g / L to 60 g / L, the concentration of sodium carbonate is 10 g / L to 40 g / L, and the balance is water.

10. The use of the medical magnesium alloy material according to any one of claims 1-3 in the preparation of biodegradable medical implants.

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