Nacre Compared to Aragonite as a Bone Substitute: Evaluation of Bioactivity and Biocompatibility

Aragonite is a metastable polymorph of calcium carbonate found in mollusk's shells, appearing in tiles and prismatic columns, cemented in a protein matrix - mainly proteins - that acts as a framework on which the aragonite is nucleated forming nacre, besides selecting the morphology of the nucleated cristaline phase. The presence of the mineralyzing organic matrix may affect osteoinductive properties of biogenic aragonite, hypothesis tested by combinated tests, comparing viability and bioactivity of biomineralizated aragonite and nacre. Bioactivity was observed by deposition of Ca-P (presumably calcium phosphate) on the surface of samples immersed in Simulated Body Fluid; biocompatibility was verified by adhesion with VERO cells; cytotoxicity and alkaline phosphatase activity assays were performed with human adipose stem cells (hASC). Samples were characterized by scanning electron microscopy and X-ray diffraction. Both materials showed similar behaviour on bioactivity assay; in contrast, exhibited different behaviours in the presence of hASC.