In vitro biocompatibility testing of collagen-calcium phosphate composites using human bone derived osteoblasts

Human bone derived osteoblasts were cultured on collagen-calcium phosphate composites. The ability of the substrates to support cell attachment, proliferation and bone formation was assessed using histochemical staining for alkaline phosphatase activity and immunolocalisation of transforming growth factor-beta 1 and type 1 collagen. The effect of calcium phosphate phase and crystal size was investigated and the calcified samples compared with uncalcified collagen. Osteoblasts adhere to the collagen-calcium phosphate composites and express a mature osteoblast phenotype in vitro. Cell adhesion was greater on unmineralised collagen than on the mineralised composites, however, these cells were less differentiated. The presence of larger crystals seemed to have a detrimental effect on the cells, reducing proliferation and alkaline phosphatase activity. There was no discernible difference between the effect of hydroxyapatite and octacalcium phosphate on the cells.