Control of bisphosphonate release using hydroxyapatite granules.

The efficacy of hydroxyapatite (HAp) as a carrier was investigated to establish a method of local administration of bisphosphonates (Bps), which has currently been administered systemically. HAp granules (300-500 microm in size) with different physicochemical features were prepared by altering the sintering temperature. To ascertain the physicochemical properties of the HAp granules, their crystallinity was assessed using X-ray diffraction, the surface morphology was examined under scanning electron microscopy, and the specific surface area and calcium dissolution were evaluated. Different Bps-HAp composites were subsequently prepared and the concentration of Bps released from these composites was measured. The influence of Bps-HAp composites on the rate of osteoclast survival was also evaluated. The results revealed that (1) HAp solubility depends on the sintering temperature; (2) The concentration of released Bps could be controlled by regulating the sintering temperature of HAp as a carrier; and (3) Bps released from Bps-HAp composites reduced the number of osteoclasts. These findings indicated that Bps-HAp composites could be locally administered as a drug delivery system to areas with bone resorption.