Proliferation and differentiation of osteoblastic cells on titanium modified by ammonia plasma immersion ion implantation

We report here a new method of titanium surface modification through ammonia (NH3) plasma immersion ion implantation (PIII) technique and its effect on the cellular behaviors of MC3T3-E1 osteoblastic cells. The NH3 PIII-treated titanium substrates (NH3–Ti) were characterized by X-ray photoelectron (XPS), which showed that NH3–Ti had a nitrogen-rich surface. However, there was no significant difference between the surface morphology of NH3–Ti and unmodified Ti. When MC3T3-E1 cells were cultured on NH3–Ti substrates, it was found that cell proliferation was accelerated at 4 and 7 days of culture. Meanwhile, cell differentiation was evaluated using type I collagen (COL I), osteocalcin (OC) and bone sialoprotein (BSP) as differentiation markers. It was found that expression of COL I and OC genes was up-regulated on NH3–Ti substrates. However, no significant difference was found in BSP gene expression between NH3–Ti and unmodified Ti substrates. Therefore, findings from this study indicate that surface modification of titanium through NH3 PIII favors osteoblastic proliferation and differentiation and as a result, it may be used to improve the biocompatibility of Ti implants in vivo.