Mechanistic insight on the combined effect of albumin and hydrogen peroxide on surface oxide composition and extent of metal release from Ti6Al4V

The titanium-aluminium (6wt%)-vanadium (4wt%) (Ti6Al4V) alloy is widely used as an orthopedic and dental implant material due to its high corrosion resistance in such environments. The corrosion resistance is usually determined by means of electrochemical methods, which may not be able to detect other chemical surface reactions. Literature findings report a synergistic effect of the combination of the abundant protein albumin and hydrogen peroxide (H2O2) on the extent of metal release and corrosion of Ti6Al4V. The objectives of this study were to gain further mechanistic insight on the interplay of H2O2 and albumin on the metal release process of Ti6Al4V with special focus on (1) kinetics and (2) H2O2 and albumin concentrations. This was accomplished mainly by metal release and surface oxide composition investigations, which confirmed the combined effect of H2O2 and albumin on the metal release process, although not detectable by electrochemical open circuit potential measurements. A concentration of 30mM H2O2 induced substantial changes in the surface oxide characteristics, an oxide which became thicker and enriched in aluminum. Bovine serum albumin (BSA) seemed to be able to deplete this aluminum content from the outermost surface or at least to delay its surface enrichment. This effect increased with increased BSA concentration, and for time periods longer than 24h. This study hence suggests that short-term (accelerated) corrosion resistance measurements are not sufficient to predict potential health effects of Ti6Al4V alloys since also chemical dissolution mechanisms play a large role for metal release, possibly in a synergistic way. (c) 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 855-867, 2019.