Antibacterial sol-gel AgMnFe₂O₄ composite coatings added with degradable MgO

The AgMnFe₂O₄-MgO composite coatings with the Ag/(Mn+Fe) atomic ratio of 0, 0.3%, 1% and 3%, respectively were prepared by sol-gel method to improve antibacterial property and biocompatibility of titanium for orthopaedic implants. SEM observation shows rare cracks of the films due to the gelling effect of MgO and silver nanoparticles precipitation at the surface. XRD analysis reveals the decreased crystallinity of MnFe₂O₄ by the addition of MgO. XPS analysis indicates metallic Ag, high-valence manganese, Fe³⁺ and Mg²⁺ species in the composite film. Contact angle measurement and potentiodynamic polarization test show that the coating samples have higher contact angles and better corrosion resistance than the polished titanium. The bonding strength of the coating is relatively low tested by the pull-out method (2.6 MPa for sample with 1%Ag). Plate counting test demonstrates the silver content dependent antibacterial activity of the coating samples against E. coli, and the antibacterial rate reaches 100% at 1%Ag. MTT assay shows good compatibility with MC3T3-E1 cells for the samples with Ag ratio up to 1%. Silver, manganese ferrite and degradable MgO together determine the biological properties of the composite coatings.