In vitro cytotoxicity evaluation of porous TiO₂-Ag antibacterial coatings for human fetal osteoblasts

Implant-associated infections (IAIs) may be prevented by providing antibacterial properties to the implant surface prior to implantation. Using a plasma electrolytic oxidation (PEO) technique, we produced porous TiO₂ coatings bearing various concentrations of Ag nanoparticles (Ag NPs) (designated as 0 Ag, 0.3 Ag and 3.0 Ag) on a Ti-6Al-7Nb biomedical alloy. This study investigates the cytotoxicity of these coatings using a human osteoblastic cell line (SV-HFO) and evaluates their bactericidal activity against methicillin-resistant Staphylococcus aureus (MRSA). The release of Ag and the total amount of Ag in the coatings were determined using a graphite furnace atomic absorption spectrometry technique (GF-AAS) and flame-AAS, respectively. Cytotoxicity was evaluated using the AlamarBlue assay coupled with the scanning electron microscopy (SEM) observation of seeded cells and by fluorescence microscopy examination of the actin cytoskeleton and nuclei after 48 h of incubation. Antibacterial activity was assessed quantitatively using a direct contact assay. AlamarBlue viability assay, SEM and fluorescence microscopy observation of the SV-HFO cells showed no toxicity for 0 Ag and 0.3 Ag specimens, after 2, 5 and 7 days of culture, while 3.0 Ag surfaces appeared to be extremely cytotoxic. All Ag-bearing surfaces had good antibacterial activity, whereas Ag-free coatings showed an increase in bacterial numbers. Our results show that the 0.3 Ag coatings offer conditions for optimum cell growth next to antibacterial properties, which makes them extremely useful for the development of new antibacterial dental and orthopedic implants.