Microspheres of hydroxyapatite/reconstituted collagen as supports for osteoblast cell growth

Microspheres comprised of particulate hydroxyapatites dispersed in fibrous collagen matrices were prepared. The procedure involved the droplet formation of hydroxyapatite/collagen mixture emulsified in olive oil, followed by the reconstitution of collagen in the presence of hydroxyapatite particles at 37°C. Various sizes of microspheres could be obtained by controlling the stirring speed of the emulsified mixture. By increasing the stirring speed from 200 to 350 and 500 rpm, the average diameter of the microspheres decreased from 1038 to 513 and 226 μm, respectively. The sizes of the microspheres reduced substantially to a range of 141 μm when 2% Span 85 was present in the emulsion mixture stirring at 200 rpm. The microspheres thus obtained can be used as carriers to support the growth of osteoblast cells. Osteoblast cells derived from calvaria proliferated from 1.5×105 to 4.5×105 cells/ml in 7 days. Correspondingly, the alkaline phosphatase activity increased 6 fold during this period. These results suggested that the hydroxyapatite/collagen microspheres could be used as the filling materials for bone defect.