Novel one-step synthesis and characterization of bone-like carbonated apatite from calcium carbonate, calcium hydroxide and orthophosphoric acid as economical starting materials

There is growing interest in the development of substituted calcium hydroxyapatite (Ca-HA) for biomedical applications. Carbonated apatite (CAP) appears as an important substituted Ca-HA because of its better biocompatibility compared to pure Ca-HA. This paper reports a novel pressure-mediated one-step synthesis of CAP starting from orthophosphoric acid, calcite and calcium hydroxide as available and high-purity starting materials. Under moderate synthesis conditions (80 °C and <13 bar), CAP with different carbonate contents could be obtained. The ratio of calcite/calcium hydroxide mixture played a crucial role for both the advancement of reaction and the carbonate content inserted in CAPʹs structure. At 80 °C, the total decomposition of calcite required a calcite/calcium hydroxide mixture containing at least a half of calcite. CAPs containing 2.25–4.17 wt% of carbonate inserted in its structure were obtained as a function of the composition of calcite/calcium hydroxide mixture. The results open a simple but effective way for the synthesis of high quality biomimetic CAP.