Osteoblast interactions with calcium phosphate ceramics modified by coating with type I collagen

Complications associated with the use of autogenous bone in the repair or replacement of tissue lost through injury or disease have driven the search for alternative sources of graft material. Bioceramics containing hydroxyapatite (HA), tricalcium phosphate (TCP), or composites that combine the best properties of both of these materials are among the principal candidates. In this study, we have investigated the in vitro proliferation, morphology, and viability of an immortalized rat osteoblast cell line cultured on HA, TCP, and composites of the two in the ratios 75:25 (H75), 50:50 (H50), and 25:75 (H25) for 28 days. The biocompatibility of each material was examined in the presence and absence of a collagen coating. With the exception of H50, cell proliferation, quantified by carboxyfluorescein fluorescence, was enhanced by collagen coating of all materials for the first 14 days, although at later time points cell numbers were unaffected. It is notable that the collagen coating was least stable on H50, the only material not to show enhancement of cell growth on coating. Confocal laser scanning microscopy confirmed that cell growth was more extensive on coated materials over the first 7-14 days in culture, and the development of cell extensions and bridges across the pores in the materials was observed. Results indicate that collagen coating of calcium phosphate ceramics may also increase their compatibility and osseointegration in vivo.