Formation of octacalcium phosphate with incorporated succinic acid through gel-mediated processing

Abstract

Calcium phosphate crystals were formed by diffusion of calcium ions into polyacrylamide (PAAm) hydrogels containing phosphate ions and succinic acid. Octacalcium phosphate (OCP) and OCP with incorporated succinate (Suc–OCP) were formed in the PAAm hydrogel. Suc–OCP was formed in the presence of excess amounts of succinic acid. The precipitates of OCP and Suc–OCP had a layered structure, composed of alternating layers of fine or irregular-shaped particles, and large spherical crystals that were the focus of this work. All of the spherical crystals were composed of many flake-like crystals. When the succinic acid concentration was ≤0.375 mol·dm⁻³ a network-like structure was observed on the spherulites, and for succinic acid concentrations ≥0.75 mol·dm⁻³ a petal-like structure was observed. These morphological changes were probably caused by adsorption of succinate ions on the (100) plane of OCP.