Biomimetic synthesis of the composites of hydroxyapatite and chitosan–phosphorylated chitosan polyelectrolyte complex

A polyelectrolyte complex (PEC) composed of chitosan (CS) and phosphorylated chitosan (PCS) was used to encapsulate a calcium phosphate by a biomimetic method. An acidic CS (polycation) solution containing calcium and phosphate ions (Ca2+: 6 mM, Ca/P = 1.67) was added into a PCS (polyanion) solution leading to the formation of a polyelectrolyte complex (PEC) with nanoscopic carbonate-containing, low-crystallinity hydroxyapatite (HA) distributed evenly in the fibrils of the PEC by controlled crystal growth. The resulting composite material, PEC–HA, has a complicated porous structure that is expected to have high biocompatibility and that may be of use as materials for bone replacement and a carrier for controlled-release therapeutic agents.