Quantification of silver ion release, in vitro cytotoxicity and antibacterial properties of nanostuctured Ag doped TiO2 coatings on stainless steel deposited by RF magnetron sputtering

Surface treatments on biomaterials using several methods have greatly reduced the in vivo bacterial attachment, surface colonization and formation of biofilm. In this study, the effect of silver (Ag) ion release against in vitro antibacterial activity and cytotoxicity of 1–4wt% Ag doped titania (TiO2) thin film coatings were evaluated. These coatings were deposited for 1–6 h onto stainless steel substrate (SS) using (radio frequency) RF magnetron sputtering technique. The coatings predominantly in the crystalline anatase phase were configured using X-ray Diffraction (XRD). Scanning electron microscopy (SEM) observation showed the presence of Ag–TiO2 nanoparticles of less than 100 nm in all the coated surfaces confirming the formation of nanostructured coatings. An initial rapid release, followed by a sustained lower release of Ag ion concentration was measured between 0.45 and 122 ppb when all the coated substrates immersed in Phosphate Buffered Saline (PBS) for 1–10 days. The obtained concentration was less than the maximum toxic concentration for human cells; yet achieved antibacterial concentration, sufficient to kill or inhibit the growth of bacteria. In vitro cytotoxicity results have indicated that 1–4 wt% of Ag doped TiO2 coatings had no adverse effect on mouse fibroblast proliferation, confirming its cytocompatibility. The antibacterial assessment was performed on 1 and 2 wt% Ag–TiO2 coatings using Staphylococcus aureus (S. aureus) whereby significant antibacterial activity was observed in 2 wt% Ag–TiO2 coatings.

► RF magnetron sputtering of Ag doped TiO2 coatings on stainless steel substrate.
► Ag ion achieved maximum antimicrobial concentration within 24 h of immersion.
► Lower sustained release of Ag ion for pro-longed antimicrobial activity.
► Ag ion was not toxic to cells but protects against S. aureus bacteria.