| Biomedical magnesium alloy materials have the advantages of biodegradability,biocompatibility and their elastic modulus is close to that of human bone,so there is great potential for development in areas such as bone tissue repair.As a substitute bone implant material for the human body,magnesium alloy can effectively avoid the impact of “stress shielding” and reduce risks such as secondary surgical infection.However,in clinical trials,it has been found that magnesium alloy can rapidly corrode in body fluids,causing it to prematurely lose its mechanical integrity,making it impossible to obtain complete physical support for damaged tissues.In addition,the hydrogen generated by its degradation in human body fluids,as well as the negative effects of the degradation products,such as the rapid rise in the p H value of the local environment of the human body,greatly limit the clinical application of magnesium alloys.In order to provide magnesium alloys with good corrosion resistance and antibacterial properties,surface treatment is an effective method.A more effective method of surface treatment is to prepare functional coatings on the surface of magnesium alloys,which comprehensively improve the performance of magnesium alloys through the advantages of corrosion resistance,antibacterial property,and biocompatibility of the coatings.MOFs,or metal organic skeleton materials,are porous materials produced by the interaction of organic ligands with metal ions or metal clusters.They have the advantages of large specific surface areas,easy modification of functional groups,and some series have good biocompatibility.They are one of the research hotspots in the field of new functional materials,and have great potential in the field of medical magnesium alloy surface coating materials.In this paper,bimetallic Mg-Cu-MOF-74 powders were prepared by hydrothermal synthesis and Mg-Cu-MOF-74 coatings were prepared on AZ31 B magnesium alloy surfaces.Silane/Mg-Cu-MOF-74 and PLA/Mg-Cu-MOF-74 composite coatings were prepared on magnesium alloy surfaces by dip coating method.Their corrosion resistance and antibacterial properties were evaluated through experimental analysis.Before preparing bimetallic MOFs coatings,magnesium ions in the magnesium matrix were activated by hydrofluoric acid pretreatment,and Mg-Cu-MOF-74 coatings with strong adhesion were prepared by in-situ growth.After the preparation of the composite coating on the surface of magnesium alloy,it is characterized and measured to analyze and judge the surface morphology and structure of the composite coating;Its corrosion resistance in SBF simulated body fluid was tested through electrochemical and immersion experiment;The antibacterial properties of the coating against Staphylococcus aureus were tested by plate coating method.The main experimental results of this study are as follows:(1)The Silane/Mg-Cu-MOF-74 and PLA/Mg-Cu-MOF-74 composite coatings on magnesium alloy surfaces were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),contact angle measurement,and adhesion testing.The obtained XRD、FTIR、and scanning electron microscope results indicate that dense and continuously distributed bimetallic MOFs(Mg-Cu-MOF-74)coatings have been successfully synthesized on the surface of magnesium alloys.The surface water contact angle test results show that compared to the bare magnesium alloy sample and the Mg-MOF-74 coated magnesium alloy sample,the Silane/Mg-Cu-MOF-74 composite coated magnesium alloy sample has better hydrophilicity,significantly improving the hydrophilicity of the coating,which is conducive to promoting the proliferation and differentiation of bone cells on the surface of magnesium alloy to a certain extent.(2)The Tafel curve and AC impedance spectroscopy were tested through electrochemical tests.The results showed that compared to magnesium alloy bare parts,Mg-MOF-74 coated samples,and PLA coated samples,magnesium alloy samples prepared with Silane/Mg-Cu-MOF-74 and PLA/Mg-Cu-MOF-74 composite coatings had a corrected corrosion potential and lower corrosion current density,while the capacitive impedance arc of the impedance spectroscopy was significantly increased;During the hydrogen evolution test,the hydrogen evolution amount of Silane/Mg-Cu-MOF-74 and PLA/Mg-Cu-MOF-74 coated magnesium alloy samples significantly decreased;The p H value test results show that the p H value of Silane/Mg-Cu-MOF-74 coating magnesium alloy has a smaller change range than that of Mg-Cu-MOF-74 coating magnesium alloy,but the p H value of PLA coating magnesium alloy is higher than that of PLA/Mg-Cu-MOF-74 composite coating magnesium alloy,which is mainly due to the neutralization of acidic substances produced by the degradation product of Mg-Cu-MOF-74 rich in-OH.The above test results indicate that magnesium alloy samples coated with Silane/Mg-Cu-MOF-74 and PLA/Mg-Cu-MOF-74 composite coatings have better corrosion resistance.(3)The bactericidal quantity of the sample soaked in Staphylococcus aureus bacterial solution reflects the antibacterial ability.In the antibacterial test results,both the Silane/Mg-Cu-MOF-74 sample and the Mg-MOF-74 sample have better antibacterial properties compared to the bare magnesium alloy,indicating that the introduction of the inorganic antibacterial agent Cu improves the bactericidal ability of the magnesium alloy,making the magnesium alloy based on the Mg-Cu-MOF-74 composite coating have better antibacterial properties. |
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