Cell response to plasma electrolytic oxidation surface-modified low-modulus β-type titanium alloys

Plasma electrolytic oxidation (PEO) has been demonstrated to be an effective surface treatment for enhancing the osteoconduction and osseointegration of commercially pure alpha-Ti (CP alpha-Ti) dental implant materials for clinical application. To explore the feasibility of extending the application of PEO to low-modulus beta-type titanium alloys for load-bearing orthopaedic implants, a thorough understanding of the effect of substrate material on the biological performance of the PEO-treated surface is required. A 10 kW 50 Hz KeroniteTM processing unit was used to modify the surface of low-modulus near beta-Ti13Nb13Zr and beta-Ti45Nb substrates. CP alpha-Ti and (alpha + beta)-Ti6Al4V were also used in parallel as reference materials. In vitro culture of foetal human osteoblast (fHOb) cells on PEO-treated low-modulus near beta-Ti13Nb13Zr and beta-Ti45Nb alloys revealed comparable behaviour to that seen with CP alpha-Ti and (alpha + beta)-Ti6Al4V with respect to metabolic activity, collagen production, matrix formation and matrix mineralisation. No difference was observed in TNF-alpha and IL-10 cytokine release from CD14(+) monocytes as markers of inflammatory response across samples. Cell interdigitation into the porous structure of the PEO coatings was demonstrated and cell processes remained adherent to the porous structure despite rigorous sonication. This study shows that PEO technology can be used to modify the surface of low-modulus beta-type titanium alloys with porous structure facilitating osseointegration, without impeding osteoblast activity or introducing an untoward inflammatory response.