Effects of carbonate ions in phosphate solution on the fabrication of carbonate apatite through a dissolution–precipitation reaction

Abstract

Carbonate apatite (CO3Ap) artificial bone has attracted much attention due to its high osteoconductivity and replacement to bone. CO3Ap is an inorganic component of bone, and has been fabricated by compositional transformation through a dissolution–precipitation reaction in Na2HPO4 solution using calcium carbonate as a precursor. In this study, the effects of the CO32− concentration in the Na2HPO4 solution on the CO3Ap fabrication reaction and the properties of the fabricated CO3Ap were investigated. The rate of the compositional transformation became faster, and more CO3 containing CO3Ap was fabricated using CO32− concentrated in Na2HPO4 solution. The crystal shape of CO3Ap changed from scale-like to hexagonal crystals. In addition, the crystallite size increased with increasing CO32− concentration in the Na2HPO4 solution. These changes lead to larger pores (≥0.02 μm) and decreased number of small pores (<0.02 μm) according to the CO3 content in CO3Ap, even though the total pore volume remained the same. These findings indicate that the CO32− concentration in Na2HPO4 solution is an important factor for the CO3Ap fabrication reaction and affects the properties of the fabricated CO3Ap.