Hydroxyapatite (HA), partially fluoride substituted hydroxyapatite (fHA), and fluorapatite (FA) were synthesized in-house and characterised. Cell attachment and proliferation on polystyrene, titanium, HA, fHA and FA were investigated. It was found that fHA was a promising biomaterial. This material supports osteoblast cell attachment equivalent to that observed with polystyrene (plastic tissue culture well), titanium (a widely used metal implant material), HA and FA. However, it is significantly superior to these materials in inducing proliferation of the human osteoblast cell line. The cell proliferation rate on fHA is more than double the rate of the remaining materials, including HA, a widely used biomaterial. fHA may thus be a potential candidate biomaterial for biomedical applications.

The use of radiolabeled precursor molecules for the metabolic analysis of cell functions is commonplace. Tritiated thymidine, in particular, has been used to quantitate cellular proliferation in numerous cells, including osteoblasts, when cultured on various biomaterials. Our aim was to assess cellular protein synthesis and proliferation, on a range of fluoride ion-substituted hydroxyapatites. Initially, we used a classical metabolic analysis strategy with radiolabeled tracer molecules. Our results suggested that these materials supported enhanced protein synthesis and proliferation of SaOS-2 human osteoblast-like cells. However, control samples also revealed enhanced adsorption of the radiolabeled tracer. We have shown that this arises because partially fluoride ion-substituted hydroxyapatite exhibits enhanced adsorptive characteristics of radiolabeled leucine and thymidine over tissue culture plastic, hydroxyapatite, and fluoroapatite. Moreover, manual cell count data obtained through SEM analysis showed no significant difference in cell proliferation between any of the materials, further indicating that our initial results were artifacts. These results highlight the use and reporting of appropriate cell-free controls are critical in bioassays examining functional responses of cells to biomaterials, and if absent, may confound accurate data interpretation. Our findings have general implications for investigations of cell function on other novel ceramic biomaterials.