Biological Activity of Tantalum Oxide Coating Doped with Calcium and Strontium by Micro-Arc Oxidation under Osteoimmunomodulation

Tantalum is widely used in clinics due to its excellent properties. However, its high density and elastic modulus constrain its application as a large implant. The new porous tantalum material addresses the issue of incompatibility between the implant and the human body; nevertheless, it still exhibits biological inertia and limited bone-bonding ability, therefore, it is necessary to modify its surface. At present, some surface modification methods have inconsistent results in vitro and in vivo. To solve this problem, this study described the preparation of a ceramic coating with a "trabeculae-like" structure on the surface of pure tantalum using micro-arc oxidation (MAO), calcium and strontium ions were introduced by adding acetate to the electrolyte. The effects of incorporating bioactive ions Ca2+ and Sr2+ into the electrolyte on the coating's morphology, coating thickness, phase composition, roughness, hydrophilicity, and the activity of MC3T3-E1 osteoblast cells under osteoimmunomodulation were investigated. The results demonstrated that the introduction of bioactive ions did not change the porous morphology of the coating; instead, it led to an increase in coating thickness, enhancement of surface roughness and hydrophilicity, as well as promotion of osteoblast spreading, proliferation, and ALP activity. Moreover, it regulated the phenotypic polarization of RAW264.7 macrophages to augment osteoblast proliferation, spreading, and ALP activity, implying that the coating has superior osteogenic potential under osteoimmunomodulation.