Improvement on biosafety and bioactivity of Ti–6Al–4V alloys by construction the three-dimensional grid structure though electrochemical dealloying

Abstract

Bioactive porous structure coatings have received extensive attention because they can significantly improve the surface bioactivity of medical metal implants. However, traditional porous making technologies were restricted by the “upward growth” mode, with an obvious interface with the substrate, resulting in weak bonding and biological safety problems. This research innovatively proposed to selectively dissolve harmful Al element on the surface of Ti6Al4V alloy through an electrochemical dealloying process, forming a three-dimensional grid porous structure in situ on the surface, with the following three notable advantages: (1) The dealloying process was a “downward growth” mode, there was no obvious interface between the porous layer and the substrate, so the bond was firm; (2) The harmful element Al was effectively removed, and the biological safety was greatly improved; (3) The three-dimensional grid porous structure owned high-efficiency osteogenic activity, which solved the problem of Ti6Al4V biological inertness. The electrode potential and corrosion current density difference of metal elements were studied by electrochemical methods to analyze the corrosion and dissolution mechanism, the successful removal of the element Al, and the thickness of the porous layer were analyzed by XPS sputtering. Furthermore, the bioactivity was verified by co-cultivation with osteoblasts. Interestingly, the results of ALP expression, collagen secretion, and calcification all implied that the dealloyed porous structure could significantly promote the osteogenic differentiation of cells. Employing the electrochemical dealloying, a “subtractive” structure was formed on the surface of Ti6Al4V, which greatly improves the bioactivity and at the same time increased its osteogenic activity, which displayed extremely high research value and bright application value.