Synthesis and in vitro biodegradation of pure octacalcium phosphate spheres

Octacalcium phosphate (OCP) is a key precursor of biological apatite in hard tissues with excellent osteoconductive and biodegradable properties for bone regeneration. OCP spherical granules are expected to be useful as drug delivery carriers, since OCP has high specific surface area. Although there have been some reports of OCP sphere preparation, methods for preparing pure OCP spheres are limited. The objective of this study is the preparation of spherical granules of pure OCP and assessment of their in vitro biodegradation in physiological conditions. We successfully prepared spherical pure OCP granules with a size of ~500 µm without any organic additives by simple immersion of α‐tricalcium phosphate spherical granules in pH 5.0 acetate buffered solutions at 60°C. The granules had core‐shell structure composed of OCP crystals different particle size. The spherical granules showed 20%‐40% in vitro degradation in physiological conditions; however, the phase transition of OCP was not significantly observed.