A method to fabricate hydroxyapatite/poly(lactic acid) microspheres intended for biomedical application

The interaction between organic and inorganic materials enables one to fabricate inorganic/organic microsphere composites. In a novel microemulsion method, we have prepared surfactant-free poly(lactic acid) (PLA)/hydroxyapatite (HAp) microspheres by using the interfacial interaction between inorganic and organic materials, because surfactants are undesireble materials for biomedical applications due to their non-biodegradability. The studies that varied the ion concentrations in oil/water microemulsions revealed that HAp was nucleated at the end group PLA, COOH, and the array of the PLA end groups determined the crystal phase of the calcium phosphate as HAp under the low ion concentration condition. PLA induced the nucleation and precipitation of HAp at the oil/water interface, simultaneously, the precipitated HAp stabilized the microemulsion without surfactants. This novel process made surfactants unnecessary for organic/inorganic microsphere fabrications.