Apatite precipitation after incubation of biphasic calcium-phosphate ceramic in various solutions: influence of seed species and proteins.

The dissolution-precipitation process for calcium-phosphate ceramics in contact with biological fluid was studied by incubating blocks of biphasic calcium phosphate composed of hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP) in different solutions: ionic simulated body fluid (SBF) without protein or SBF that contained various proteins and macromolecules separately (fibronectin, vitronectin, albumin, and poly-L-glutamic acid). Transmission electron microscopy studies revealed that apatite-precipitated microcrystals appeared around ceramic crystals as a result of secondary nucleation; microcrystals were in continuity with the lattice planes of the HA crystals but in a different direction from that of beta-TCP; the size of the precipitates was smaller when fibronectin, vitronectin, and poly-(L-glutamic acid) were present in SBF as compared to SBF without protein; and fibronectin and vitronectin initiated crystal nucleation in the void spaces between the ceramic crystals.