Improved Cell Adhesion and Osseointegration on Anodic Oxidation Modified Titanium Implant Surface

Although titanium material is currently widely used in dental and orthopedic application, the bio-inertness of Ti impairs its further use. We previously reported the good bioactivity and biocompatibility of TiO2 nanotube layer fabricated by anodic oxidation technique using in vitro tests. In the present work, we further clarify the cell adhesion and osseointegration properties of anodized surface through both in vitro and in vivo tests. After anodic oxidation (AO), the structure of nanotubes was confirmed by scanning electron microscopy. The surface roughness and hydrophilic properties of the AO and pristine Ti surfaces were evaluated by atomic force microscopy and contact angle measurement test, respectively. It was found that the AO surface displayed moderately higher surface roughness and obviously increased wettability, compared to the original Ti surface. In vitro cellular activity tests demonstrated that osteoblast cells cultured on the AO surface exhibited a much well-spread cytoskeleton organization with more stretched actin filaments, compared to those cultured on the Ti surface. The adherent cell number was also higher on the AO surface than the pure Ti substrate. In addition, we explore the molecular basis of mechanism by analyzing gene expression levels of adhesion and osteogenesis-related genes in MC3T3-E1 cells cultured on different surfaces using quantitative real-time PCR. Increased mRNA levels of vinculin, collagen type I, osteopontin and osteocalcin were found on the AO surface, compared with the control group. Furthermore, in vivo animal experiment using a rat model revealed that anodized implant surface promotes osseointegration and demonstrated higher bone bonding strength compared to the pure Ti substrate. Our study revealed the superior cell adhesion property, increased adherent and osteogenesis-related gene expressions and enhanced osseointegration by anodized surface, thus implying its enlarged application in future.