Functionally gradient chitosan/hydroxyapatite composite scaffolds for controlled drug release.

This study explored the potential of chitosan/hydroxyapatite (HA) composites to act as a controlled drug delivery system by developing functional scaffolds with a gradient of structure and drug concentration. Firstly, a porous composite scaffold was prepared and tetracycline hydrochloride (TCH) was impregnated in the scaffold as a model drug. The pore size of the scaffold was negatively dependent on the HA content and ranged about 40-250 microm. Subsequently, a porous chitosan/HA composite layer without drug was coated on the scaffold to create a gradient drug concentration in the specimen. The in vitro drug-release test demonstrated that the porous layer without drug on the outer surface of the scaffold significantly reduced the initial burst of drug release and extended the release period. Finally, a successive and dense chitosan/HA composite layer endowed the scaffold with a sustained, drug-release pattern without any initial drug burst. These findings confirmed the high effectiveness of the hybrid scaffolds in regulating the release of drugs, and hence their capability to serve as a temporary drug carrier in tissue regeneration. These functional scaffolds also have potential application to the delivery of some bioactive molecules such as growth factors.