Biofunctionalization of biomedical Ti-based alloys using micro-arc oxidation and the concept of high entropy oxides

Abstract

In orthopedy, total joint replacements for hip (THR) and knee (TKR) based on titanium have been the main focus of researchers in the biomedical area, once the region supports critical biomechanical loads of the human body joints, which expose the materials to constant corrosion and wear mechanisms, resulting in a decay of their lifespan. The Ti-6Al-4V alloy (ASTM F136) is the most used titanium alloy worldwide, especially in medicine. However, the ion release of potentially toxic and allergenic Al and V ions after long-term implantation has required new strategies for surface coating. Within the available surface modification techniques of metals, plasma-based techniques have been highlighted in the biomedical field, especially the micro-arc oxidation (MAO) treatment. The MAO has been established as an important tool to modify the titanium's surface, forming porous oxide coatings, strongly bound to the substrate, and enriched with specific chemical species from the electrolytic solution. One exciting possibility, never exploited before in the biomedical field, is the usage of high entropy oxide (HEO) coatings, composed of at least five distinct oxides, which have obtained emerging properties for diverse current technological applications. In this sense, the project has the goal to evaluate, for the first time, the MAO effect in the production of porous high entropy alloys (PHEOs) based on transition metallic oxides (OTMs) of Ti, Mn, Al, Mo, and Fe, and enriched with bioactive elements (Ca and P). With a specific focus on the biofunctionalization of the biomedical Ti-6Al-4V alloy, targeting potential applications as orthopedic implants. (AU)