Influence of Ag alloying on the antibacterial properties, bio-corrosion resistance and biocompatibility of α-Nb₅Si₃ nanocrystalline coating

Abstract

To improve the corrosion resistance and impart the bioactivity and antibacterial functionalities to titanium alloys for biomedical applications, α-(Nb₁₋ₓAgₓ)₅Si₃ compounds, with three different Ag contents, were deposited on Ti–6Al–4V by double cathode glow discharge method. The new α-(Nb₁₋ₓAgx)₅Si₃ coatings, each about 16 μm in thickness, exhibited a compact uniform structure, composed of equiaxed nanocrystalline grains. Nanoindentation measurements revealed that Ag alloying reduced the hardness (H) and elastic modulus (E) values of the α-(Nb1-xAgx)5Si3 coatings. Compared to Ti–6Al–4V, the α-(Nb₁₋ₓAgₓ)₅Si₃ coatings exhibited improved corrosion resistance in Ringer’s physiological solution, as well as newly added in-vitro bioactivity and antibacterial ability against both E. coli and S. aureus. A MTT assay experiment shows that the two α-(Nb₁₋ₓAgₓ)₅Si₃(x = 0 and 0.05) coatings were as non-cytotoxic as bare Ti-6Al-4V. However, the MC3T3-E1 osteoblast-like cell viability for the α-(Nb₀.₉Ag₀.₁)₅Si₃ coating was slightly reduced, suggesting that the proliferation of MC3T3-E1 osteoblast-like cell was affected to some degree by excess Ag added to α-Nb₅Si₃. Overall, the α-(Nb₀.₉₅Ag₀.₀₅)₅Si₃ coating provides an attractive combination of good bioactivity, high corrosion resistance and new antibacterial function, and thus demonstrates great potential for applications in orthopedic devices.