The inflammatory potential of biphasic calcium phosphate granules in osteoblast/macrophage co-culture

Some biological properties of a range of biphasic calcium phosphate (BCP) granules were quantified using a co-culture model of primary unstimulated human osteoblasts and macrophages. The BCP granules were classified in terms of diameter and the ratio of tricalcium phosphate (TCP): hydroxyapatite (HA). All granules were 50% porous and sterilised by gamma-irradiation. Primary unstimulated human osteoblasts and macrophages were cultured in contact with the range of BCP granules for 1, 7 and 14 days. The response of the cells was determined and quantified by the assessment of viable cell adhesion to the substrate, using lactate dehydrogenase assay, and the production and release of the cytokines; interleukin 1beta, (IL-1beta), tumour necrosis factor alpha (TNF-alpha) and prostaglandin E2 (PGE2). Throughout the test period viable cell adhesion on all BCP granules was significantly lower than the tissue culture polystyrene control. Higher content TCP materials, (80% and 100% TCP) did not support viable cell adhesion after 1 day, lower content TCP materials, (20% and 50% TCP) granules did support viable cell adhesion throughout the time period. The percentage content of TCP was a more significant factor than granule size within the test conditions at all time points.