A degradable surface-modified magnesium alloy material with corrosion resistance, antibacterial and bone-promoting properties and a preparation method thereof

Abstract

This invention discloses a biodegradable surface-modified magnesium alloy material with corrosion resistance, antibacterial properties, and osteogenic properties, as well as a method for preparing the same. The biodegradable surface-modified magnesium alloy material comprises a micro-arc magnesium oxide coating with a porous structure and an iron hydroxyl oxide layer formed in situ on the surface of the magnesium oxide coating. The iron hydroxyl oxide at least partially seals the porous structure of the micro-arc magnesium oxide coating.

Description

Technical Field

[0001] This invention relates to a biodegradable surface-modified magnesium alloy material with corrosion resistance, antibacterial properties and osteogenic properties, and its preparation method, belonging to the field of surface modification technology of metallic materials. Background Technology

[0002] Magnesium and magnesium alloys possess advantages such as good mechanical properties and biodegradability, with degradation products being excreted through metabolism, and an elastic modulus close to that of bone tissue, earning them the reputation of "next-generation medical metal materials." However, the rapid degradation rate of magnesium and magnesium alloys in vivo, along with their poor biocompatibility, antibacterial properties, and ability to promote bone differentiation, limits their widespread clinical application.

[0003] The rapid degradation rate of magnesium and magnesium alloys in vivo leads to premature loss of mechanical properties and can also cause an increase in the pH of the tissue fluid around the implant, resulting in an inflammatory response. Surface modification of magnesium alloys is a common method to improve corrosion resistance. In recent years, the exploration and development of micro-arc oxidation coatings has attracted widespread attention from researchers. However, micro-arc oxidation coatings themselves have a porous structure, which easily leads to localized corrosion, resulting in insufficient corrosion resistance. Furthermore, the main phase of micro-arc oxidation coatings is magnesium oxide, which lacks excellent biological functions.

[0004] Therefore, developing a novel intelligent self-assembling anti-corrosion functional coating is of great significance. However, there are few reports on the preparation of intelligent coatings to improve the corrosion resistance of samples by regulating the corrosion reaction, while simultaneously combining the coating characteristics to achieve functional design and corresponding products. How to design and obtain magnesium alloy surfaces with good corrosion resistance, while also promoting bone differentiation and antibacterial properties, is of great practical significance, and this is also a key focus and challenge in the research of surface modification of medical magnesium alloys. Summary of the Invention

[0005] To address the issues of rapid degradation and insufficient biofunctionality of medical-grade bio-magnesium alloys, this invention provides a biodegradable surface-modified magnesium alloy material and its preparation method that combines corrosion resistance, antibacterial properties, and osteogenic properties. This material improves the corrosion resistance of the micro-arc oxidation coating while also possessing biological functions such as promoting osteogenic differentiation and antibacterial properties, thereby meeting clinical needs for magnesium alloy degradation rate, osteogenic differentiation, and antibacterial performance.

[0006] In a first aspect, the present invention provides a biodegradable surface-modified magnesium alloy material. The biodegradable surface-modified magnesium alloy material comprises a micro-arc magnesium oxide coating with a porous structure and an iron hydroxyl oxide layer formed in situ on the surface of the magnesium oxide coating, wherein the iron hydroxyl oxide at least partially seals the porous structure of the micro-arc magnesium oxide coating.

[0007] The micro-arc oxidation coating grows in situ on the magnesium alloy surface, bonding firmly to the substrate and reducing the corrosion rate of the magnesium alloy to a certain extent. Utilizing the alkaline environment generated by the corrosion reaction of the magnesium alloy itself, FeOOH nanosheets self-assemble on the magnesium oxide coating surface, effectively sealing the pores of the porous magnesium oxide layer and further improving the coating's corrosion resistance, while also enhancing the material's biocompatibility. The biodegradable surface-modified magnesium alloy material of this invention utilizes the photocatalytic and photothermal properties of the FeOOH coating to effectively eliminate bacterial infections before and after implantation. Simultaneously, the FeOOH coating effectively controls the corrosion and release of magnesium and iron ions in the magnesium implant, improving cell adhesion, diffusion, proliferation, and osteogenic differentiation activity, thus promoting osteogenic formation in vivo.

[0008] Preferably, the pore size of the micro-arc magnesium oxide coating is 0.1 to 1.8 μm.

[0009] Preferably, the biodegradable surface-modified magnesium alloy material has an iron atomic mass percentage of 3.9% to 20.3%. An iron atomic mass percentage below 3.9% will result in the coating failing to effectively seal the microporous structure of the micro-arc oxidation coating. An iron atomic mass percentage above 20.3% will result in weak adhesion of the coating, making it prone to detachment.

[0010] Preferably, the total thickness of the coating of the biodegradable surface-modified magnesium alloy material is 3–7 μm. More preferably, the thickness of the hydroxyl iron oxide layer is 0.2–1.2 nm.

[0011] In this invention, the hydroxyl iron oxide coating can effectively seal the porous structure of the micro-arc porous magnesium oxide coating, thereby improving the corrosion resistance, biocompatibility and osteogenic properties of the micro-arc oxidation coating; in addition, due to the photogenerated carrier effect and photothermal conversion performance of FeOOH, the coating has a certain antibacterial effect under simulated sunlight and near-infrared light irradiation.

[0012] Secondly, the present invention provides a method for preparing the biodegradable surface-modified magnesium alloy material as described in any of the above claims. The preparation method includes: constructing a porous micro-arc magnesium oxide coating on the surface of a magnesium alloy using micro-arc oxidation technology; immersing the magnesium alloy coating covered with the micro-arc magnesium oxide coating in a ferrous ion solution, and forming a hydroxyl iron oxide layer on the surface of the magnesium oxide coating through in-situ reaction. The reason for choosing an aqueous solution of ferrous ions to form the hydroxyl iron oxide layer is that the main phase of the micro-arc oxidation coating is MgO, which is a basic oxide and easily dissolved in an acidic environment. The pH value of ferric ion solutions is usually below 4, indicating acidity, which would damage the micro-arc magnesium oxide coating. The pH value of the ferrous ion solution is close to neutral and will not damage the micro-arc magnesium oxide coating.

[0013] Preferably, the ferrous ion solution is an aqueous solution of ferrous sulfate and / or ferrous chloride; the concentration of the ferrous ion solution is 1–4 g / L.

[0014] Preferably, the immersion temperature is 20–40°C, and the immersion time is 0.5–4 hours. If the immersion temperature is too high, ferrous ions are easily oxidized to ferric ions too quickly, making the immersion solution acidic and damaging the micro-arc oxidation coating. If the immersion time is too long, FeOOH cannot effectively bind to the surface, resulting in weak adhesion. The concept of this invention lies in the localized alkaline environment generated by micro-arc magnesium oxide to precipitate ferrous ions and form FeOOH. Excessive immersion time prevents the effective formation of a localized alkaline environment on the sample surface to precipitate ferrous ions and form FeOOH, and also results in weak adhesion of the coating, making it prone to peeling off.

[0015] Preferably, the steps for constructing a porous micro-arc magnesium oxide coating on the surface of a magnesium alloy using micro-arc oxidation technology are as follows: using a magnesium alloy as a substrate, and using an aqueous solution of sodium glycerophosphate at a concentration of 5-15 g / L and potassium hydroxide at a concentration of 10-15 g / L as an electrolyte, the porous micro-arc magnesium oxide coating is prepared by micro-arc oxidation.

[0016] Preferably, the process parameters for the micro-arc oxidation are: voltage of 320-360V, current of 0.6-1.0A, duty cycle of 8-12%, and frequency of 800-1200Hz.

[0017] Thirdly, the present invention provides a method for improving the corrosion resistance of a micro-arc porous magnesium oxide coating on a magnesium alloy surface. The method includes: constructing a micro-arc magnesium oxide coating with a porous structure on the surface of a magnesium alloy using micro-arc oxidation technology; immersing the magnesium alloy covered with the micro-arc magnesium oxide coating in a ferrous ion solution, and forming a hydroxyl iron oxide layer on the surface of the magnesium oxide coating through in-situ reaction.

[0018] Beneficial effects

[0019] 1. The iron hydroxyl oxide (FeOOH) coating prepared by this invention can cleverly utilize the alkaline microenvironment formed during the corrosion process of the micro-arc porous magnesium oxide coating to react and generate a nano-scale iron hydroxyl oxide (FeOOH) coating, effectively sealing the pores of the porous micro-arc magnesium oxide coating and improving the corrosion resistance of the coating.

[0020] 2. The iron hydroxyl oxide (FeOOH) coating prepared by this invention possesses excellent photocatalytic and photothermal properties, enabling the elimination of bacteria before and after implantation. Simultaneously, during implant degradation, the material exhibits excellent bone differentiation-promoting effects under the synergistic effect of magnesium and iron ions.

[0021] 3. The hydroxyl iron oxide coating prepared by this invention enhances the corrosion resistance of the micro-arc porous magnesium oxide coating. This coating can be used directly as an anti-corrosion coating for magnesium and its alloys or as a pretreatment layer, and is expected to be applied in aerospace, transportation and medical metal materials and other fields.

[0022] 4. Compared with magnesium and its alloy surface coatings prepared by other methods, the coating of this invention has an in-situ bond with the substrate, has strong adhesion, does not require complicated equipment, is relatively safe in the experimental process, and is conducive to large-scale industrialization. Attached Figure Description

[0023] Figure 1 The following are scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) spectra of the sample surfaces in Example 1: a) is the microscopic surface of the untreated micro-arc porous oxide in Example 1; b) is the cross-section of the untreated micro-arc porous magnesium oxide in Example 1; c) is the EDS spectrum of the untreated micro-arc porous magnesium oxide in Example 1.

[0024] Figure 2 The following are scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) spectra of the sample surface in Example 2: a) Microscopic surface of iron hydroxyl oxide (FeOOH) prepared by immersion in Example 2; b) Cross-section of iron hydroxyl oxide (FeOOH) prepared by immersion in Example 2; c) EDS spectrum of iron hydroxyl oxide prepared by immersion in Example 2.

[0025] Figure 3 The following are scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) spectra of the sample surface in Example 3: a) Microscopic surface of iron hydroxyl oxide (FeOOH) prepared by immersion in Example 3; b) Cross-section of iron hydroxyl oxide (FeOOH) prepared by immersion in Example 3; c) EDS spectrum of iron hydroxyl oxide prepared by immersion in Example 3.

[0026] Figure 4 The following are scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) spectra of the sample surface in Example 4: a) Microscopic surface of iron hydroxyl oxide (FeOOH) prepared by immersion in Example 4; b) Cross-section of iron hydroxyl oxide (FeOOH) prepared by immersion in Example 4; c) EDS spectrum of iron hydroxyl oxide prepared by immersion in Example 4.

[0027] Figure 5 a shows the X-ray diffraction (XRD) patterns of Examples 1-4; b shows the Raman spectrum of the sample prepared in Example 4; c and d show the high-resolution X-ray photoelectron spectra of Fe 2p and O1s of Example 4, respectively.

[0028] Figure 6Figure a shows the polarization curves of samples from Examples 1-4; Figure b shows the hydrogen release curves of samples from Examples 1-4. The curves in b, from top to bottom, are AZ31, PEO, PEO-Fe1, PEO-Fe2, and PEO-Fe3.

[0029] Figure 7 The osteoblast (MC3T3-E1) proliferation results of Examples 1-4 are shown.

[0030] Figure 8 In Figure a, the photocurrent test results of Examples 2-4 are shown, and in Figure b, the photothermal test results of Examples 1-4 are shown.

[0031] Figure 9 The results of antibacterial test plates for Examples 1-4 are shown.

[0032] Figure 10 The bacterial colony counts for antimicrobial tests in Examples 1-4 are shown.

[0033] Figure 11 Osteogenic performance tests of Examples 1 and 4 with AZ31 magnesium alloy as a control group are shown. Detailed Implementation

[0034] The present invention is further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention. Unless otherwise specified, all percentage contents refer to mass percentage contents.

[0035] Current research indicates that elemental and nanoparticle doping, along with surface sealing, are the main methods for improving the corrosion resistance of micro-arc oxidation coatings. However, existing sealing techniques typically employ hydroxyapatite (hydrothermal method) or polymers (spin-coating or immersion method). While these methods can improve the mechanical stability and corrosion resistance of the coating to some extent, and reduce the contact between corrosion products and the substrate, they still suffer from problems such as weak coating adhesion and insufficient biocompatibility.

[0036] Therefore, this invention provides a surface-modified magnesium alloy material for bone tissue repair. The surface of the surface-modified magnesium alloy has: an in-situ generated micro-arc magnesium oxide layer, and a nanoscale iron hydroxyl oxide (FeOOH) coating in-situ generated within and on the surface of porous magnesium oxide pores. The FeOOH has a nanosheet structure, and the coating is crack-free. The micro-arc magnesium oxide coating grows in-situ on the magnesium alloy surface, and this coating is firmly bonded to the substrate, reducing the degradation rate of the material to a certain extent and improving its corrosion resistance. This coating also has good stability, which is beneficial for the in-situ self-assembly of the FeOOH coating on its surface. This invention is the first to introduce iron-based materials into the surface modification of medical implants. The preparation method is simple, suitable for industrial production, and suitable for surface modification of complex components.

[0037] Furthermore, the surface-modified magnesium alloy material (self-assembled intelligent nano-FeOOH coating material) exhibits excellent corrosion resistance and biocompatibility, which is beneficial to the adhesion and proliferation of mouse embryonic osteoblastic progenitor cells. In addition, the ALP activity and extracellular matrix mineralization level of mouse embryonic osteoblastic progenitor cells on the modified material surface are significantly increased, and the modified material surface also exhibits antibacterial activity against Staphylococcus aureus. Therefore, the surface-modified magnesium alloy material of this invention can be widely used in medical devices related to bone tissue repair.

[0038] This invention also relates to a method for surface modification of medical biodegradable magnesium alloys. Specifically, it is a surface modification method that first constructs a micron-scale porous magnesium oxide coating on the material surface using micro-arc oxidation (MAO) technology, and then further constructs a nano-scale iron hydroxyl oxide (FeOOH) coating on the surface of the micro-arc porous magnesium oxide coating using an immersion process.

[0039] A micron-sized magnesium oxide coating was constructed on the surface of a magnesium alloy using micro-arc oxidation technology. Using a polished magnesium alloy sheet as a substrate, a mixed solution of 5–15 g / L sodium glycerophosphate and 10–15 g / L potassium hydroxide was prepared in deionized water as the micro-arc oxidation electrolyte. In some embodiments, the micro-arc oxidation parameters were: voltage 320–360 V, current 0.6–1.0 A, duty cycle 8–12%, and frequency 800–1200 Hz. The resulting micro-arc magnesium oxide coating had a pore size range of 0.1–1.8 μm.

[0040] Micron-sized magnesium oxide coatings are immersed in a ferrous ion solution to obtain nano-sized FeOOH coatings. A method for preparing iron hydroxyl oxide coatings on the surface of micro-arc oxidation coatings using an immersion method involves placing the micro-arc magnesium oxide coating in a ferrous ion solution. Magnesium oxide is alkaline, generating a large number of hydroxide ions (OH-) around it. - ), reacts with free ferrous ions to form ferrous hydroxide (Fe(OH)2), which is unstable and is oxidized by surrounding oxygen to ferric hydroxide (FeOOH). The specific reaction is as follows: Fe 2+ +2OH - =Fe(OH)2, 4Fe(OH)2+O2=4FeOOH+2H2O.

[0041] The ferrous ion solution is either ferrous chloride or ferrous sulfate, and the solvent is water. The ferrous ion concentration is 1–4 g / L. When the ferrous ion concentration is too low, the ferric hydroxide coating thickness is too low, failing to seal the pores of the porous micro-arc magnesium oxide coating, thus resulting in poor corrosion resistance. When the ferrous ion concentration is too high, the solution acidity increases, easily generating magnesium hydroxide during immersion, reducing the coating's corrosion resistance.

[0042] The preferred immersion temperature is room temperature, between 20 and 35°C. The immersion time is between 0.5 and 4 hours. If the immersion time is too short, the iron content will be too low, failing to improve corrosion resistance. If the immersion time is too long, the ferrous ions will gradually oxidize in the air, preventing further increase in the iron content of the coating.

[0043] The total thickness of the coating on the biodegradable surface-modified magnesium alloy material is 3–7 μm. In some embodiments, the total thickness of the hydroxyl iron oxide-reinforced micro-arc magnesium oxide anti-corrosion coating can be 4–5.5 μm.

[0044] Micro-arc oxidation technology can be used to construct micron-sized porous magnesium oxide coatings in situ on magnesium alloy surfaces. This coating, prepared via plasma arc discharge, is hard and firmly bonded to the substrate, effectively improving the corrosion resistance of the magnesium alloy. To further enhance the coating's corrosion resistance and endow it with certain biological functions, a FeOOH coating is formed in situ via a one-step immersion method on the surface of the micro-arc oxidation coating. This FeOOH coating grows in situ within and on the surface of the porous magnesium oxide coating, effectively sealing the pores and further improving the material's corrosion resistance. Simultaneously, utilizing the photocatalytic and photothermal properties of the FeOOH coating, bacterial clearance is achieved before and after implantation. Combined with the synergistic effect of iron and magnesium ion release, this endows the material with excellent bone differentiation-promoting function, resulting in a surface-modified magnesium alloy material with good corrosion resistance, bone differentiation-promoting, and antibacterial properties.

[0045] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0046] Polarization curves: The potentiodynamic polarization curves of the samples were measured using an electrochemical workstation (CH1760C, Chenhua, Shanghai). The solution used for testing was 0.9 wt% NaCl solution (PBS, Sigma, USA). The working system was a three-electrode system, with a graphite auxiliary electrode, a KCl solution-saturated calomel electrode (SCE) as the reference electrode, and the test sample as the working electrode. The test area was 0.255 cm². 2 Before testing the polarization curves, the samples were immersed in PBS solution for 400 s to obtain a stable open-circuit potential. The polarization curve testing potential range was -2V to 0V, the scan rate was 10mV / s, and the testing temperature was room temperature.

[0047] Hydrogen evolution experiment: The hydrogen evolution rate of the samples was tested using a graduated funnel and beakers. Four parallel samples were placed in the beakers, and 250 mL of 0.9 wt% NaCl solution was added. The apparatus was placed in a 37°C water bath. The amount of hydrogen released was recorded daily.

[0048] Cell experiments

[0049] Cell proliferation: MC3T3-E1 cells were used to evaluate the effect of the samples on cell proliferation. Samples were placed in 24-well culture plates and sterilized by UV irradiation for 12 h. Cells were added to each well at a density of 5 × 10⁶ cells / well. 4 Cells were cultured on the sample surface for 1, 4, and 7 days, and the cell proliferation rate was detected using AlamarBlue.

[0050] Alkaline phosphatase (ALP) expression: Samples were placed in 24-well culture plates and sterilized by UV irradiation for 12 h. 1 mL of LF12 basal medium + 10% fetal bovine serum (FBS) + 1% penicillin + streptomycin was added to each well, and the plates were incubated at 37°C and 5% CO2 for 24 h. The culture medium was then used as an extraction medium, and osteogenic induction medium (100 nM dexamethasone + 10 mM β-glycerophosphate sodium + 50 mM ascorbic acid and glutamine) was added to the extraction medium. The plates were then stored at 4°C for later use. C3H10T1 / 2 cells (2 × 10⁻⁶) were then cultured. 4 Cells were seeded in 24-well culture dishes for 12 hours, and then the culture medium was replaced with the extract from each group of samples. At 3 and 7 days of culture, the cells were washed twice with PBS, and 40 μL of IRIPA lysis buffer (without phosphatase inhibitors) was added. Lysis was performed on ice for 10 min. The lysate was scraped off with a clean cell scraper and transferred to an enzyme-free 1.5 mL centrifuge tube. Centrifugation was performed at 12000 rpm for 15 min, and the supernatant was used as the protein lysis buffer. Alkaline phosphatase (ALP) activity was quantitatively assessed using an ALP assay kit and a Bicinchonic acid (BCA) protein quantification kit (both from Beyotime Biotechnology, China).

[0051] Antibacterial experiment: Gram-positive Staphylococcus aureus (S. aureus, ATCC 25923) was selected as the model pathogen, and 500 μL of diluted bacterial suspension (10⁷ CFU / mL) was co-cultured with the sample in a 24-well plate for 12 h. Subsequently, some wells were irradiated with xenon lamp (0.2 W / cm², 15 min) and 808 NIR (0.8 W / cm², 10 min) as simulated visible light treatment group and near-infrared light treatment group, respectively. Then, the sample was transferred to a test tube containing 4 mL of saline solution, and the bacteria adhering to the sample surface were separated by shaking. Next, the solution was diluted 100 times, and 100 μL of the diluted bacterial solution was spread onto a standard agar plate. The plate was incubated at 37 °C for 18 hours, and the bacterial colonies were photographed and counted.

[0052] Photocurrent testing: The photoelectrochemical properties of the samples were measured using an electrochemical workstation in a 0.1M sodium sulfate (Na₂SO₄) aqueous solution. A xenon lamp was used to provide a light source to simulate sunlight (0.2 W / cm²). 2 Xenon lamp).

[0053] Photothermal testing: Samples were placed in 24-well plates containing 500 μL PBS, and the light intensity of the samples under 808 nm NIR light (1.0 W / cm²) was monitored using a FLIR ONE infrared thermometer. 2 Temperature changes under irradiation.

[0054] Example 1

[0055] (1) Remove the surface oxide layer of an AZ31 magnesium alloy disc with a thickness of 2mm and a diameter of 10mm using 1000-grit SiC sandpaper, and then clean it with alcohol by ultrasonic cleaning to serve as a substrate.

[0056] (2) Prepare a mixed aqueous solution of 10 g / L sodium glycerophosphate and 12.5 g / L potassium hydroxide using deionized water as the electrolyte for micro-arc porous magnesium oxide.

[0057] (3) The magnesium alloy sheet was electrolyzed in constant voltage mode with the following parameters: cutoff voltage 340V, current 0.8A, duty cycle 10%, and frequency 1000Hz. The prepared sample surface was covered with a micro-arc porous magnesium oxide coating, labeled as PEO.

[0058] from Figure 1 It can be seen that the surface of the PEO sample has a porous structure and the coating thickness is about 4.2 μm.

[0059] Example 2

[0060] (1) Prepare a 2 g / L FeCl2·4H2O solution using deionized water.

[0061] (2) The magnesium alloy sample coated with the micro-arc porous magnesium oxide coating in Example 1 was immersed in the prepared ferrous chloride solution for 0.5 hours. The prepared sample was labeled as PEO-Fe1.

[0062] from Figure 2 As can be seen, the surface of the PEO-Fe1 sample has a semi-closed porous structure, and the coating thickness is about 4.1 μm, which is not significantly different from the micro-arc porous magnesium oxide sample without iron modification treatment in Example 1.

[0063] XRD and XPS results indicate the formation of iron hydroxyl oxide on the surface; energy dispersive spectroscopy results indicate that the iron atomic mass percentage of the coating is 3.9%; polarization curves and hydrogen evolution experiments show that the modified coating improves the corrosion resistance of the sample; cell experiments show that the modified coating improves the biocompatibility of the sample; antibacterial experiments show that the coating has antibacterial effects under certain simulated sunlight and near-infrared light irradiation.

[0064] Example 3

[0065] (1) Prepare a 2 g / L FeCl2·4H2O solution using deionized water.

[0066] (2) The magnesium alloy sample coated with the micro-arc porous magnesium oxide coating in Example 1 was immersed in the prepared ferrous chloride solution for 1 hour. The prepared sample was labeled as PEO-Fe2.

[0067] from Figure 3 As can be seen, the sample surface exhibits a microscopic, protruding nanosheet structure, with a coating thickness of approximately 5.0 μm. XRD and XPS results show the formation of iron hydroxyl oxide on the surface; energy dispersive spectroscopy results indicate that the iron atomic mass percentage of the coating is 10.3%; polarization curves and hydrogen evolution experiments show that the modified coating improves the corrosion resistance of the sample; cell experiments show that the modified coating improves the biocompatibility of the sample; and antibacterial experiments show that the coating has antibacterial effects under certain simulated sunlight and near-infrared light irradiation.

[0068] Example 4

[0069] (1) Prepare a 2 g / L FeCl2·4H2O solution using deionized water.

[0070] (2) The magnesium alloy sample coated with the micro-arc porous magnesium oxide coating of Example 1 was immersed in the prepared ferrous chloride solution for 2 hours. The prepared sample was labeled as PEO-Fe3.

[0071] from Figure 4 As can be seen, the surface of the PEO-Fe3 sample has a nanosheet structure, and the coating thickness is about 5.5 μm.

[0072] from Figure 5As can be seen, XRD results show that the iron-containing coating prepared by the immersion method exhibits a small peak of FeOOH on the sample prepared in Example 4; further Raman spectroscopy and XPS tests show that the iron-containing coating prepared by the immersion method is iron hydroxyl oxide (FeOOH). XRD and XPS results show that iron hydroxyl oxide is formed on the surface; energy dispersive spectroscopy results show that the atomic mass percentage of iron in the coating is 14.8%; polarization curves and hydrogen evolution experiments show that the modified coating improves the corrosion resistance of the sample; cell experiments show that the modified coating improves the biocompatibility of the sample; antibacterial experiments show that the coating has antibacterial effects under certain simulated sunlight and near-infrared light irradiation; osteogenic experiments show that the coating has enhanced osteogenic properties.

[0073] from Figure 6 As can be seen, in Examples 1-4, the corrosion current and hydrogen release decreased with increasing iron hydroxyl oxide (FeOOH) content, indicating a progressively stronger corrosion resistance. The increased iron hydroxyl oxide content signifies a better sealing effect of the coating on the micro-arc coating, thus gradually improving corrosion resistance.

[0074] from Figure 7 As can be seen from the results of Examples 1-4, the osteoblast activity on the sample surface increases with the increase of ferric hydroxide (FeOOH) content, and the biocompatibility of the samples increases accordingly. The osteogenic activity of magnesium-based alloy implants is closely related to their corrosion resistance. Rapid corrosion can easily cause a strong inflammatory response in the tissue, delaying osteogenic formation. Therefore, improving the corrosion resistance of modified magnesium alloy materials will improve their osteogenic activity.

[0075] from Figure 8 As can be seen, iron hydroxyl oxide (FeOOH) possesses the ability to generate photocarriers and exhibits photothermal conversion performance. FeOOH itself is a semiconductor material with a band gap of 2.2 eV. Under visible light irradiation, electrons at the bottom of the valence band are excited to the conduction band, generating electron-hole pairs (carriers). Therefore, the photogenerated carriers of the modified magnesium alloy material described in this invention can be improved. The micro-arc oxidation coating is white, while the iron hydroxyl oxide coating is yellow and has a stronger light absorption capacity. Part of the absorbed light is converted into heat energy. At the same time, due to the poor thermal conductivity of magnesium oxide, the coating temperature rises under near-infrared light irradiation. This is the aforementioned photothermal conversion performance of the iron hydroxyl oxide coating.

[0076] from Figure 9As can be seen, the iron hydroxyl oxide (FeOOH) sample exhibits good antibacterial effects under both simulated sunlight and near-infrared light irradiation. Higher iron hydroxyl oxide content results in more photogenerated charge carriers (electron-hole pairs; electrons have strong reducing properties, and holes have strong oxidizing properties) generated under simulated sunlight irradiation, which kill bacteria. Furthermore, higher iron hydroxyl oxide content leads to higher coating temperatures under near-infrared light irradiation; excessively high temperatures can effectively kill bacteria.

[0077] from Figure 10 It can be seen that the iron hydroxy oxide (FeOOH) sample exhibits good antibacterial effects under simulated sunlight and near-infrared light irradiation.

[0078] from Figure 11 It can be seen that iron hydroxyoxide (FeOOH) has an enhanced osteogenic effect compared to AZ31 and Example 1.

[0079] Example 5

[0080] (1) Prepare a 1 g / L FeCl2·4H2O solution using deionized water.

[0081] (2) The magnesium alloy sample covered with micro-arc porous magnesium oxide coating in Example 1 was immersed in the prepared ferrous chloride solution for 4 hours.

[0082] SEM results showed that the sample exhibited a micro-protruding nanosheet structure; XRD and XPS results showed that hydroxyl iron oxide was formed on the surface; energy dispersive spectroscopy results showed that the atomic mass percentage of iron in the coating was 19.7%; polarization curves and hydrogen evolution experiments showed that the modified coating improved the corrosion resistance of the sample; cell experiments showed that the modified coating improved the biocompatibility of the sample; antibacterial experiments showed that the coating had antibacterial effects under certain simulated sunlight and near-infrared light irradiation.

[0083] Example 6

[0084] (1) Prepare a 4 g / L FeCl2·4H2O solution using deionized water.

[0085] (2) The magnesium alloy sample covered with micro-arc porous magnesium oxide coating in Example 1 was immersed in the prepared ferrous chloride solution for 2 hours.

[0086] SEM results showed that the sample had a nanosheet structure; XRD and XPS results showed that hydroxyl iron oxide was formed on the surface; energy dispersive spectroscopy results showed that the atomic mass percentage of iron in the coating was 20.3%; polarization curves and hydrogen evolution experiments showed that the modified coating improved the corrosion resistance of the sample; cell experiments showed that the modified coating improved the biocompatibility of the sample; antibacterial experiments showed that the coating had antibacterial effects under certain simulated sunlight and near-infrared light irradiation.

Claims

1. A biodegradable surface-modified magnesium alloy material, characterized in that, The biodegradable surface-modified magnesium alloy material includes a micro-arc magnesium oxide coating with a porous structure and an iron hydroxyl oxide layer formed in situ on the surface of the magnesium oxide coating, wherein the iron hydroxyl oxide at least partially seals the porous structure of the micro-arc magnesium oxide coating. The method for preparing the biodegradable surface-modified magnesium alloy material includes: constructing a porous micro-arc oxide magnesium coating on the surface of the magnesium alloy using micro-arc oxidation technology; The magnesium alloy covered with the micro-arc magnesium oxide coating is immersed in a ferrous ion solution, and a hydroxyl iron oxide layer is formed on the surface of the magnesium oxide coating through in-situ reaction. The ferrous ion solution is an aqueous solution of ferrous sulfate and / or ferrous chloride; the concentration of the ferrous ion solution is 1–4 g / L. The soaking temperature is 20–40°C, and the soaking time is 0.5–4 hours; The steps for constructing a porous micro-arc magnesium oxide coating on the surface of a magnesium alloy using micro-arc oxidation technology are as follows: using a magnesium alloy as a substrate, an aqueous solution of sodium glycerophosphate with a concentration of 5-15 g / L and potassium hydroxide with a concentration of 10-15 g / L is used as an electrolyte, and the porous micro-arc magnesium oxide coating is prepared by micro-arc oxidation.

2. The biodegradable surface-modified magnesium alloy material according to claim 1, characterized in that, The micro-arc magnesium oxide coating has a pore size of 0.1–1.8 μm.

3. The biodegradable surface-modified magnesium alloy material according to claim 1 or 2, characterized in that, The biodegradable surface-modified magnesium alloy material has an iron atom mass percentage of 3.9% to 20.3%.

4. The biodegradable surface-modified magnesium alloy material according to any one of claims 1 or 2, characterized in that, The total coating thickness of the biodegradable surface-modified magnesium alloy material is 3–7 μm.

5. The biodegradable surface-modified magnesium alloy material according to claim 1, characterized in that, The process parameters for micro-arc oxidation are: voltage 320-360V, current 0.6-1.0A, duty cycle 8-12%, and frequency 800-1200Hz.

6. A method for preparing a biodegradable surface-modified magnesium alloy material, characterized in that, The biodegradable surface-modified magnesium alloy material is the biodegradable surface-modified magnesium alloy material as described in claim 1, comprising: constructing a micro-arc magnesium oxide coating with a porous structure on the surface of a magnesium alloy by micro-arc oxidation technology; immersing the magnesium alloy covered with the micro-arc magnesium oxide coating in a ferrous ion solution, and forming a hydroxyl iron oxide layer on the surface of the magnesium oxide coating by in-situ reaction.

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