In Vitro Bioactivity and Cell Biocompatibility of a Hypereutectic Bioceramic

Two dense biphasic ceramics, with a hypereutectic composition of 30 wt % CaSiO3-70 wt % Ca-3(PO4)(2), were synthesized by a solid-state reaction of homogeneous pressed combinations of previously synthesized synthetic CaSiO3 and Ca-3(PO4)(2) powders. The objective was to produce a dense structure to generate large enough in situ pores for the ceramic to be used in tissue engineering. To develop such a structure, two grain sizes of CaSiO3 were used (63-100 mu m and 100-150 mu m) and some of their properties were studied in vitro, as they are relevant for tissue engineering. X-ray diffraction analysis, mu-Raman spectroscopy, diametrical compression test, and scanning electron microscopy with elemental mapping showed a coarse-grained homogeneous microstructure for the materials, which consisted of wollastonite (alpha-CaSiO3) and tricalcium phosphate (alpha-Ca-3(PO4)(2)), with adequate mechanical properties for implantation. In vitro bioactivity was evaluated in simulated body fluid (SBF) by exploring a hydroxyapatite (HA)-like formation. The results showed that tricalcium phosphate grains dissolved more preferentially than those of wollastonite, but not fast enough to leave a pore before the surface was coated with an HA-like layer after soaking only for three days. Biocompatibility was evaluated by in vitro cell experiments, which showed cell proliferation, adhesion, and spreading on the ceramic surface. This ceramic is expected to be used as a bone graft substitute.