Effect of Carbonate Content on the Response of Human Osteoblast-Like Cells to Carbonate Substituted Hydroxyapatite

摘要

Four batches of carbonate-substituted hydroxyapatite discs, designated CA1, CA2, CA3 and CA4, were prepared with carbonate contents of 5.4, 6.1, 8.2 and 11.3 wtpercent, respectively. The biological response to these materials was compared with the response to stoichiometric hydroxyapatite (HA) by biochemical evaluation of human osteoblast-like cells (HOBs) incubated both in direct contact with the discs and in culture medium containing solutes from the five substrates. Assessment of the cellular response to solutes from the five substrates demonstrated enhanced activity in those cells exposed to CA3 discs. Biochemical and morphological assessment of HOBs in direct contact with the disc surfaces supported this finding with enhanced proliferation being achieved in cells incubated on CA3 discs as compared to HA. However, while the response to CA4 was found to be comparable to the HA, proliferation was suppressed in cells incubated on CA1 and CA2 discs, as confirmed by the poor morphological appearance of cells on these discs, apparently due to increased ceramic solubility leading to a degradation in the cell/substrate interface. This indicates that HOB cell metabolism is highly sensitive to the precise level of carbonate ion substitution, which in low carbonate HA reflects the solubility of the material. Moreover, the optimum level of carbonate substitution has been identified as similar to that found in bone mineral.