Initial osteoblast functions on Ti-5Zr-3Sn-5Mo-15Nb titanium alloy surfaces modified by microarc oxidation

This study is intended to evaluate the effects of microarc oxidation (MAO) on the biocompatibility of near beta titanium alloy Ti-5Zr-3Sn-5Mo-15Nb (TLM) in vitro. Two porous bioactive surfaces with different surface characteristics were grown on TLM substrates via MAO process at two different final voltages. Both calcium and phosphorus were incorporated into the oxidized surfaces, and their content was dependent on the voltage applied. Surface roughness was enhanced on the MAO surfaces, which was higher when a higher voltage was applied. After MAO treatment, water contact angles became smaller and surface energies were increased, especially the polar components, which were also related to the MAO final voltage. Cell culture experiments showed an enhanced osteoblasts adhesion, spread, and viability on the microarc oxidized surfaces, and better cell spread and viability were found on the surface formed at 450 V than that at 300 V. No obvious variations in gene expression of integrin beta1 (Itg beta 1), core binding factor-alpha1, osteopontin, collagen type I alpha2-chain, and fibronectin by osteoblasts were observed on different surfaces. The expression of osteocalcin was strikingly increased on MAO surfaces after 72 h, thus indicating enhanced osteoblasts differentiation on MAO surfaces. Interestingly, obvious enhanced bone morphogenetic proteins (BMP)-2 and BMP-4 expression was observed on MAO surfaces, which may be a reason for the enhanced osteoblasts functions on MAO-modified TLM surfaces.