Long-term antibacterial performance and bioactivity of plasma-engineered Ag-NPs/TiO₂ nanotubes for bio-implants

We prepared TiO₂ nanotubes (NT) on commercially pure titanium (cp-Ti) substrate by plasma electrolyte oxidation and adapted magnetron sputtering for incorporation of Ag-nanoparticles (Ag-NPs) onto the nanotubes (Ag-NPs/TiO₂ nanotube). Power input to the Ag target per unit time was varied (5, 10, 15 W/cm²) to fabricate different shapes of Agnanoparticles onto the nanotubes while net energy input was fixed by maintaining a constant total sputter time (30, 15, 10 s, respectively). For investigation of experimental samples' characteristics, FE-SEM, TEM, EDS, XRD, XPS, SPM analysis and contact angles measurement was carried out. Through these characterization, plasma engineered Ag-NPs was successfully formed on/in the entire nanotube structure. In terms of antibacterial ability, plasma engineered Ag-NPs/TiO₂ nanotubes samples significantly reduced S. aureus colony numbers compared with control. Also, simulated body fluid immersion tests with hydroxyapatite showed ion precipitation onto the surface of all experimental groups, confirmed by XRD and EDS analysis. However, plasma engineered Ag-NPs/TiO₂ nanotubes groups were not cytotoxic. Furthermore, MC3T3-E1 cells were cultured on Ag-NPs/TiO₂ nanotubes groups to evaluate the effect of nanostructured surface on cell functionality such as a cell proliferation and ALP activity. Ag-NPs/TiO₂ nanotubes have both biocompatible and antibacterial characteristics.