Antimicrobial Effect of Medical Grade Ti-6Al-4V Alloy after Oxygen Plasma Modification

Titanium (Ti-6Al-4V) alloy is one of the most widely used metallic biomaterials in orthopaedic surgeries due to its good mechanical properties and cyto-compatibility. However, post-operative implant related bacterial infection is not uncommonly seen. This may eventually lead to implant removal if antibiotic therapy fails. Bacterial adhesion on implant surface is an important virulent factor in local implant-related infection. To avoid bacterial infection, the primary line to defence is to inhibit the initial adhesion of bacteria on the implant surface. If maintained, suppression of subsequent bacterial proliferation and biofilm formation will be possible. In this study, oxygen plasma immersion ion implantation (O-PIII) had been employed to produce antibacterial surface on medical grade titanium alloy. The elemental depth profiles were determined by X-ray photoelectron spectroscopy with the use of aluminum X-ray source with 350W, and the surface topography and roughness were determined by atomic force microscopy. The bacterial adhesion was assessed by counting colony forming unit (CFU) using clinically isolated S.aureus culture. The number of cells was determined by surface plating on Brain Heart Infusion agar after 24hrs incubation. LIVE/ DEAD BacLight Viability Kit staining was applied to evaluate the adhered bacteria morphology. Furthermore, enhanced green fluorescent protein (EGFP) mouse osteoblastic cells were used to evaluate the cytocompatibility of these samples after the plasma treatments. Our results suggested that the surface modified by O-PIII at different implantation frequencies could significantly suppress bacterial adhesion while the cytocompatibility could be maintained. The nanoscale TiO2 surface is promising to minimize the implant-related bacterial infection of orthopaedic implants made of Ti-6Al-4V alloy.