Development of titanium oxide films biofunctionalized with structural and chemical gradient on the Ti-40Nb alloy for osseointegrated implants

The persistence of complications after artificial joint surgery has indicated that there is still an intense demand for improvements on orthopedic implant materials. Current requirements to avoid the most frequent clinical problems involve tribocorrosion resistance, low elastic modulus, fast promotion of osseointegration, and broad antibacterial activity. Binary Ti-Nb alloys are under attention of the scientific community mainly due to their attractive low Young’s modulus, whereas the micro-arc oxidation (MAO) technique allows the biofunctionalization of the implant surface in a versatile and low-cost way. Therefore, this work aimed at investigating, for the first time, a new process of surface functionalization by MAO technique, consisting on the formation of porous layers incorporated with bioactive agents (Ca, P, Mg, Zn, and Sr) and ceramic nanoparticles (ZrO2 NPs) gradually distributed on the surface of the biomedical Ti-40Nb alloy (wt.%) for osseointegrated implants. MAO coatings were formed under the influence of different processing voltages, with or without the presence of ZrO2 NPs in the electrolyte. The general mechanisms of oxide growth and incorporation of ZrO2 NPs were discussed for the different processing conditions, through morphological, chemical and structural analysis. The tribocorrosion behavior of the new surfaces was elucidated for two loading conditions in physiological solution. The results indicated that an improved inert incorporation of ZrO2 NPs could contribute to the accommodation of internal stresses, and then delay eventual phenomena of brittleness and cracking associated with rutile-rich MAO coatings during vigorous mechanical solicitations. (AU)