Preparation of Nanotextured and Nanofibrous Hydroxyapatite through Dicalcium Phosphate with Gelatin

Organized nanostructures of hydroxyapatite (HAp) were produced using a novel preparation route through the topotactic transition of dicalcium phosphate dihydrate (DCPD) containing gelatin molecules. A nanoscale texture of dicalcium phosphate (DCP) was formed by the dehydration of DCPD prepared in gelatin gel containing phosphate ions. A three-dimensionally oriented framework of HAp consisting of ca. 20 nm grains was prepared by a rapid hydrolysis of the nanotextured DCP with a sodium hydroxide solution. Nanoscale HAp fibers elongated along the c axis with a diameter of ca. 50 nm were also obtained by a moderate hydrolysis with ammonia water. The hierarchical architectures of the nanostructured HAp were successfully achieved by the phase transition associated with the specific interaction of the organic molecules.