In vitro antibacterial activity of porous TiO2–Ag composite layers against methicillin-resistant Staphylococcus aureus

The aim of this study was the synthesis of a porous TiO2-Ag composite coating and assessment of its in vitro bactericidal activity against methicillin-resistant Staphylococcus aureus. The coating was produced by plasma electrolytic oxidation of Ti–6Al–7Nb medical alloy in a calcium acetate/calcium glycerophosphate electrolyte bearing Ag nanoparticles. Following oxidation, the surface of the titanium substrate was converted into the corresponding oxide (TiO2) bearing Ca and P species from the electrolyte. In addition, Ag was detected associated with particles present in the oxide layers. The coatings revealed a porous interconnected structure with pores up to 3 μm in size, a threefold increase in roughness and improved wettability relative to the non-oxidized specimens. The composite TiO2-Ag coating showed complete killing of methicillin-resistant S. aureus within 24 h in all culture conditions, whereas a 1000-fold increase in bacterial numbers was recorded with the ground titanium specimens and the samples oxidized in the absence of Ag nanoparticles.