Calcium phosphate granules for use as a 5-Fluorouracil delivery system

The possibility of tailoring apatite granules as a controlled release system for the drug model 5-Fluorouracil (5FU) has been examined. Apatite granules (SDG) were obtained by spray drying suspensions of hydroxyapatite (HAP) nanoparticles previously precipitated from citrate solutions [M.A. Martins, C. Santos, M.E.V. Costa, M.M. Almeida, Preparation of porous hydroxyapatite particles to be used as drug delivery systems, Advanced Materials Forum II (455) (2004) 353–357]. SDG had donut shape and very high specific surface area (150 m2/g) indicative of high porosity. SDG were poorly crystalline HAP but turned into biphasic granules (HSDG) with crystalline tricalcium phosphate and HAP after annealing at 800 °C, while reducing their surface area down to ∼6 m2/g. SDG and HSDG were soaked in a 5FU solution at pH 5.2 and room temperature during several days and then transferred to a phosphate buffered solution (PBS) at pH 7.4 and 37 °C, for releasing 5FU. The comparison between the 5FU adsorbing and releasing behaviours exhibited by SDG and HSDG shows that engineering the granules characteristics, i.e. specific surface area, surface chemical composition, porosity and crystal phase composition allows the 5FU release profile to be controlled.