Bone formation on apatite-coated titanium incorporated with bone morphogenetic protein and heparin

Purpose: Bone morphogenetic proteins (BMPs) strongly induce osteogenesis and are enhanced by heparin. In this study, a potent osteoinductive material was developed by coating the surface of titanium with apatite incorporated with BMP and heparin. Materials and Methods: Titanium samples were treated with a 5 N NaOH solution and heated at 600°C for 24 hours. The treated titanium was soaked in simulated body fluid (SBF) for 4 days and additionally soaked in SBF containing recombinant human BMP-2 (rhBMP-2;l,000 ng/mL) with or without heparin (30 μg/mL) for 3 days at 37°C. The surfaces of each sample were examined with scanning electron microscopy. The presence of rhBMP-2 on the surface of the apatite-coated titanium was examined using the immunogold method. MC3T3-E1 osteoblast-like cells were cultured on the surface of each sample. The number and morphology of the adherent cells, alkaline phosphatase activity, and osteocalcin mRNA expression were examined. Results: Apatite was formed on the surface of alkaline heat-treated titanium after soaking in SBF for 7 days. The presence of rhBMP-2 was confirmed by the distribution of BMP-positive immunogold particles. The incorporation of (≥ 3 μg/mL) heparin significantly increased alkaline phosphatase activity and osteocalcin mRNA expression in the cells on apatite-coated titanium containing rhBMP-2. Conclusion: These findings demonstrate that heparin enhanced BMP-2-induced osteogenesis on apatite-coated titanium without the loss of BMP-2 activity. The combination of BMP-2 and heparin was effective even in the thin apatite layer formed on titanium using the alkaline heat treatment method. Int j Oral Maxillofac Implants 2008;23:1013-1019.