Antibacterial activity of a porous silver doped TiO2 coating on titanium substrates synthesized by plasma electrolytic oxidation

The objective of this study was the development of Ag-rich antibacterial coatings on titanium to prevent post-operative infections. A series of Ag-doped TiO2 coatings were synthesized on Ti discs by plasma electrolytic oxidation in an electrolyte containing AgNPs. The incorporation, distribution and chemical composition of the AgNPs on Ti were determined using scanning electron microscopy-energy dispersive spectroscopy. The crystalline structure and wettability of the coating was characterized by X-ray diffraction and water contact angle analysis respectively. Surface roughness and hardness of the coating were examined using surface profilometry and Knoop indentation test respectively, while silver ion release was quantified using inductively coupled plasma-mass spectroscopy. Following PEO, the surface of the Ti substrate was converted to TiO2 composed of anatase and rutile phases. The SEM micrographs showed that the AgNPs were distributed throughout the oxide layer, without changing the morphology of the coating. The coatings also revealed an increased surface roughness, microhardness and improved surface wettability relative to untreated Ti substrates. Furthermore, the incorporation of Ag into the coating did not alter the phase component, roughness, microhardness and wettability. A series of in-vitro antibacterial assays indicated that increasing the number of AgNPs in the electrolyte led to excellent antibacterial activities.