Novel synthesis of AB-type carbonated hydroxyapatite hierarchical microstructures with sustained drug delivery properties

In this study, AB-type carbonated hydroxyapatite (CHAp) nanosheet-assembled hollow microstructures were rapidly synthesized via a hydrothermal process without sintering. Urea was employed as both a pH adjusting agent and a CO32- source during hydrothermal reaction. The influence of hydrothermal time on the final morphologies of the products was systematically investigated. The as-prepared CHAp hollow microstructures with a diameter of about 3-4 mu m consist of numerous radially oriented CHAp nanosheets as building units with an average thickness of about 10 nm. The morphology of the product can vary from a hollow microstructure to a solid dandelion-like structure with increasing hydrothermal time. Possible mechanisms for the formation of a nanosheet-assembled CHAp hollow microstructure and a solid dandelion-like microstructure in the presence of both urea and ethylenediaminetetraacetic acid (EDTA) are illustrated. Moreover, the as-prepared CHAp hollow microstructures exhibit a high drug loading capacity and sustained drug release properties.