Insights into the surface and biocompatibility aspects of laser shock peened Ti-22Nb alloy for orthopedic implant applications

This paper reports the effect of varying laser-peening fluences (3, 6 and 9 GW/cm2) on surface topography, oxide composition and wettability of low modulus Ti-22Nb at.% (Ti-35.4Nb wt.%) alloy with specific focus on the ensuing fretting wear and biocompatibility. Microtopography with nano-sized pores were generated during the laser interaction. LP-6 and LP-9 GW/cm(2) surfaces displayed nano-porous distribution, with topographies characterized by negative skewness and platykurtosis. X-ray photoelectron studies revealed the development of mixed oxide layers rich in Ti4+ and Nb5+ when laser fluence was increased. Improved hydrophilic behavior was observed with increment in laser fluence displaying contact angles of 47.1 & nbsp; and 43.2 & nbsp; for LP-6 and LP-9 GW/cm(2). Based on the preliminary surface characterizations, LP-6 and LP-9 GW/cm(2) which displayed a platykurtic surface with negative skewness, Ti-Nb based mixed oxides and stable hydrophilic nature were selected for further analysis. Presence of Nb5+ ions rendered the oxide surfaces less defective, thereby improving fretting wear resistance. In particular, well-spread cells and up-regulation of beneficial genetic-markers (Ki67) on laser-peened surfaces demonstrated the role of nano-sized cues and oxide-layer in improving osseointegration aspects. Results demonstrate that LP-6 and LP-9 GW/cm(2) surfaces on low modulus Ti-22Nb alloy can beneficially contribute towards the fretting wear and biocompatibility.