HA has a very similar chemical composition to the inorganic part of human hard tissue, such as bone and teeth, so most of bones form a direct chemical bonding to an HA implant without forming a collagen interface layer. In this study, we tried to observe the bone formation of the biocomposite mixed with stem cells and hydroxyapatite (HA) powders with different particle sizes in rabbit long-bone defects, and investigated the size effects of hydroxyapatite particles on the formation of new bone. From the radiological photographs of the implanted biocomposites into rabbits weekly for 8 weeks, nanoscale HA biocomposites show a higher bone formation rate than that of micrometer scale HA biocomposites. Added stem cells into the biocomposite induced homogeneous bone formation and enhanced the bone formation ability. Conclusively, nanoscale HA powder with stem cells is an adequate biocomposite for new bone formation in bone defects.

Keywords: Hydroxyapatite, Stem cell, Bone formation, Size effects