Rapid nano-scale surface modification on micro-arc oxidation coated titanium by microwave-assisted hydrothermal process.

Nano to submicron scaled surface possesses excellent biological affinity and several processes have been undertaken to develop titanium implant with specific surface chemical and phase composition and nano-scale features. A simple process was used to modify the nano topographies on a micro-arc-oxidation (MAO) surface which shortens the time for the conventional hydrothermal process (HT). Nano-scaled anatase precipitates on the MAO surface with different crystallinities and morphologies were regulated via microwave-assisted hydrothermal in pure water (MWDD) or in pH conditioned mediums containing calcium and phosphorus ions (MWCP, MWCP9, MWCP11). The surface morphologies and structures were investigated by SEM, XRD, FTIR, and TEM. Anatase crystals as nano-spikes along [001] direction were observed on the surface of the MWDD and MWCP groups. Increasing the pH of the conditioned medium leads the precipitate to lose its crystallinity; the surface of MWCP11 is covered with amorphous anatase which has a 3D nano-sheet architecture. The MW treated surfaces possess superior hydrophilicity can adsorb more proteins (fibronectin and bovine serum albumin), and the osteoblasts-like MG63 cells on these surfaces have higher spreading ratios than on the MAO and HT groups. The cell viabilities in the MW groups were significantly higher than in the MAO and HT groups on the 7th day (P < 0.05), although their cell viabilities were similar on the first day. MWCP and MWCP11 have higher alkaline phosphatase activity on days 7 and 14 compared to other groups (P < 0.05). The MW treatment produces different nanomorphologies on the MAO surface and retains the original micro/submicron pores and surface calcium and phosphorus contents, thus it is expected to promote osseointegration without compromising the bond strength.