Preparation and characterization of hollow hydroxyapatite microspheres by the centrifugal spray drying method

Hollow hydroxyapatite microspheres were fabricated using the centrifugal spray drying method. The ammonium bicarbonate was added as the pore forming agent which can be decomposed at the low temperature. The influences of the addition amount of ammonium bicarbonate on size distribution and specific surface area of hollow hydroxyapatite microspheres were also discussed. The results revealed that almost all the microspheres had good spherical morphology with a hollow internal structure, and their walls were composed of nanosized particles. It also has been found that the inner diameter of the hollow microspheres was very large. A high specific surface area (72.517 m2/g) and porosity of the hollow microspheres could be obtained when the addition amount of ammonium bicarbonate was about 7 wt.%. These hollow microspheres may be a promising candidate for drug carriers and cell deliveries systems.