Effect of biphasic calcium phosphate on human macrophage functions in vitro

Bioceramics may initiate several and complex biological reactions in host tissues. The cell-biomaterial interaction can determine macrophage activation that may elicit and sustain inflammatory response at the implant site. The current study describes some of the in vitro phenomena regarding the effect of surface reactivity of biphasic calcium phosphate (BCP) granules on human macrophages locomotion and secretion. X-ray diffraction analysis indicated that the synthesized ceramic presented 80% hydroxyapatite and 20% tricalcium phosphate. When BCP was put in contact with human macrophage cells, we observed that cells and BCP granules attached to each other. Cells attached to BCP presented a higher intracellular free Ca(2+) concentration compared with nonattached neighbors and secreted calcium phosphate particles into the medium. Energy dispersive X-ray analysis showed that the secreted particles presented a calcium/phosphorus ratio of 1.64 +/- 0.05, similar to hydroxyapatite. We propose that the secreted particles create a transition zone that allows further macrophage adhesion.