Synthesis of a novel b-tricalcium phosphate/hydroxyapatite biphasic calcium phosphate containing niobium ions and evaluation of its osteogenic properties

To promote the osteogenic properties of osteoblasts, we synthesized a hydroxyapatite (HAp) with β-tricalcium phosphate (β-TCP) biphasic calcium phosphate containing Nb ions (NbTCP/HAp). NbTCP/HAp was prepared by annealing precipitates obtained by coprecipitation of an aqueous solution of Ca(NO3)2 and a mixture of (NH4)2HPO4 and aqueous Nb solution. The precipitates can be regarded as a calcium-deficient HAp, the PO4 sites of which are partly occupied by Nb ions. NbTCP/HAp was successfully synthesized by thermal decomposition of the precipitates. NbTCP/HAp enhanced the calcification of normal human osteoblasts (NHOst), and the amount of calcified tissue increased in proportion to the Nb ion concentration in the NbTCP/HAp. The alkaline phosphatase (ALP) activity of NHOst was also enhanced by NbTCP/HAp. Because Nb ions significantly enhance the ALP activity of NHOst, calcification by NbTCP/HAp is considered to be due to enhancement of ALP activity induced by Nb ions dissolved from NbTCP/HAp. These results indicate that NbTCP/HAp can be an effective bone repair material.