The emergence of antibiotic-resistant bacteria has increased the number of implant revision procedures in the Netherlands due to implant-associated infections (IAI). Staphylococci strains accounted for more than 50% of all IAI cases. Preventative measure, such as active antibacterial surfaces on the implant, are urgently needed. This study aims to synthesize and characterize antibacterial surfaces containing silver nanoparticles (Ag NPs) and pure zinc nanoparticles (Zn NPs) on selective laser melting (SLM) Ti6Al4V implants, and evaluate the in vitro antibacterial properties against methicillin-resistant Staphylococcus Aureus (MRSA).

Porous SLM Ti6Al4V implants were biofunctionalized using plasma electrolytic oxidation (PEO) surface modification technique with calcium and phosphorus-based electrolyte bearing combinations of Ag NPs and pure Zn NPs. After PEO processing, the surface morphology and chemical compositions of the implant surface was analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The Ag+ and Zn2+ ion release kinetics were measured for 28 days and hydroxyl (•OH) radical generation was determined using electron paramagnetic resonance (EPR) for 150 minutes. Finally, in vitro antibacterial properties were evaluated against MRSA.

PEO processing resulted in implant surfaces with seven different Ag NPs and pure Zn NPs rations with interconnected micro/nano-porous surface. The presence of Ag NPs and pure Zn NPs on the implants surface was confirmed with SEM and EDS analysis. The Ag+ and Zn2+ ion release accumulated over time, up to 28 days. From the measured ion release kinetics, the addition of Ag NPs stimulated the Zn2+ ion release in early hours in the implant groups with Ag NPs and pure Zn NPs combinations. Antibacterial mechanisms through the •OH radical generations were also detected in all PEO-modified groups, with PT–Zn generating the highest intensity. The antibacterial properties demonstrated comparable inhibition zones between PT–Ag and implant groups with Ag NPs and pure Zn NPs combinations, while no inhibition zone was observed in PT–Zn. Bactericidal properties against adherent MRSA were observed on PT–Ag and implant groups with Ag NPs and pure Zn NPs combinations, while only PT–Ag Zn 75 25, PT–Ag, and PT–Ag Zn killed the non-adherent MRSA. As well, prevention against MRSA biofilm formation for 24 hours were observed only in PT–Ag and the implants groups with Ag NPs and pure Zn NPs combinations.

Antibacterial surfaces bearing Ag NPs and pure Zn NPs on porous SLM Ti6Al4V implants demonstrated promising in vitro antibacterial properties, which should be further developed for prevention of IAI in clinical applications.