Synthesis of Substituted Octacalcium Phosphate for Filling Composite Implants Based on Polymer Hydrogels Produced by Stereolithographic 3D Printing

Abstract

Based on theoretical and experimental analysis of ionic equilibria in buffer solutions, we have found conditions for octacalcium phosphate (OCP), Ca₈(HPO₄)₂(PO₄)₄ ∙ 5H₂O, synthesis. Succinate-substituted OCP, Ca₈(HPO₄)_2–хSuc_x(PO₄)₄ ∙ 5H₂O, with x = 0.8–0.9 has been synthesized at pH 5.5 and t = 60°C in 3 h via α-TCP hydrolysis in a 0.25 M succinic buffer solution. The synthesis product is more stable to thermolysis than is pure OCP: the apatite-like product is stable up to 630°C. The succinate@OCP powder has been used as a filler for poly(ethylene glycol)diacrylate-based hydrogel in producing a composite implant by stereolithographic 3D printing.