Fabrication of dicarboxylic-acid-substituted octacalcium phosphate blocks via cementing

Abstract

Octacalcium phosphate (OCP) blocks with substituted dicarboxylic acid are attractive materials for new bioceramics because the substituted dicarboxylic acid enhances and regulates the biocompatibility of OCP. Therefore, OCP blocks can be model materials for biological bones and new medical combination products. However, dicarboxylic-acid-substituted OCP blocks are difficult to fabricate using conventional OCP fabrication methods such as dissolution–precipitation and simple precipitation methods because the counter cations in buffer solutions strongly inhibit dicarboxylic acid substitution into the OCP unit lattice. This study proposes a pure OCP-block fabrication method based on the cement setting of CaCO3, H3PO4, and dicarboxylic acid, which inserts dicarboxylic acid into the OCP matrix. OCP blocks with various dicarboxylic-acid substituents (succinate, thiomalate, and citrate) were obtained after optimizing the amount of CaCO3 in the mixtures. The mechanical strength of the dicarboxylic-acid-substituted OCP blocks significantly exceeded that of unsubstituted OCP.