Enhanced corrosion resistance and antibacterial performance of Ti–6Al-7Nb via silver-modified micro arc oxidation

Titanium alloys are extensively utilised in orthopaedic and dental implants; however, concerns related to corrosion-induced ion release and implant-associated infections necessitate advanced surface engineering strategies. In this investigation, micro-arc oxidation (MAO) was employed to fabricate bioactive oxide coatings on Ti6Al7Nb alloy, followed by addition of silver nanoparticles (AgNPs) to impart antibacterial functionality. The performance of MAO-coated Ti6Al7Nb was systematically compared with Ti6Al4V ELI under identical processing conditions. Surface characterization revealed a porous TiO₂-based coating composed of anatase and rutile phases with uniformly incorporated Ca and P. Electrochemical impedance spectroscopy demonstrated a bilayer coating structure, having porous outside layer and a dense inside barrier layer responsible for superior corrosion resistance. The inner layer resistance of Ti–6Al–7Nb (97,980 Ω.cm²) exceeded that of Ti–6Al–4V ELI, indicating enhanced electrochemical stability, likely associated with the presence of niobium oxide. Biocompatibility assessment using MTT assay showed that MAO-coated Ti–6Al–7Nb achieved the highest average cell viability (94.53%), significantly exceeding the ISO 10993-5 threshold of 70% and outperforming uncoated counterparts. Incorporation of AgNPs resulted in stronger antibacterial performance verses S. aureus and E. coli, having a maximum inhibition zone of 16.5 millimetre at 1.5 g/L silver nanoparticles concentration. The antibacterial effect was concentration-dependent and attributed to membrane disruption and sustained Ag⁺ ion release. Overall, the combined improvements in corrosion resistance, cytocompatibility, and antibacterial performance demonstrate that AgNP-incorporated MAO-coated Ti6Al7Nb is a highly promising candidate for next-generation implants requiring long-term stability and infection resistance.