Evaluation of cell activation promoted by tantalum and tantalum oxide coatings deposited by reactive DC magnetron sputtering

Previous studies have shown both Ta and Ta-O to be bioactive, rapidly forming a strongly-bonded surface- adherent layer of bone-like hydroxyapatite (HAp) when immersed in simulated body fluid (SBF). Consequently, Ta and Ta-O coatings are promising for the surface-modification of Ti or stainless steel endodontic endosseous implants, being conducive to a reduction in the risk of developing post-operatory infection and/or peri-implantitis disease. That said, few studies have investigated the effect of Ta or Ta-O coatings on such phenomena as cell activation, adhesion, and proliferation.& para;& para;To that effect, Ta, and Ta-O films were deposited onto type 316L stainless steel (SS 316L) substrates by reactive DC magnetron sputtering, after which their biological response was evaluated following co-incubation with the murine macrophage-like cell line RAW 264.7. Cell morphology after adhesion was observed by SEM, whereas cell viability and proliferation were evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylte-trazolium bromide (MTT) colorimetric assay. Lastly, inflammatory response was assessed by quantification of the cytokines interleukin-6 (IL-6) and interleukin-10 (IL-10).& para;& para;In terms of phase composition, Ta showed a mixture of the alpha-Ta and beta-Ta phases, whereas Ta-O showed a nanocrystalline structure. Moreover, a decrease in average roughness (R-a) from 21 nm to 7 nm was observed between Ta and Ta-O, accompanied by a decrease in water contact angle (theta(W)) from 106 degrees to 83 degrees.& para;& para;In vitro studies showed that cells exhibited significantly better adhesion to Ta, in comparison with both Ta-O and SS 316L. Furthermore, both Ta and Ta-O were shown to be non-cytotoxic, with Ta outperforming Ta-O in terms of relative cell viability, both at 24 h and 48 h. Lastly, both Ta and Ta-O showed vastly inferior IL-6 and IL-10 levels to those obtained for cells treated with bacterial lipopolysaccharides (LPS)-prompting the conclusion that the coatings do not in any way induce an inflammatory response from macrophage cells.