Hydroxyapatite nanorod-assembled hierarchical microflowers: rapid synthesis via microwave hydrothermal transformation of CaHPO4 and their application in protein/drug delivery

Hydroxyapatite (HAP) nanostructured materials have attracted much attention due to their excellent biocompatibility and promising applications in various biomedical fields. In this study, a facile method has been developed to synthesize HAP with flower-like hierarchical nanostructures. The flower-like CaHPO4 precursor is firstly synthesized using triethyl phosphate (TEP) as the organic phosphorus source by the solvothermal method. The HAP hierarchical microflowers constructed with nanorods are then fabricated through rapid microwave hydrothermal transformation of the CaHPO4 precursor in NaOH aqueous solution. The as-prepared HAP nanorod-assembled hierarchical microflowers are explored to study the protein/drug loading and release properties using hemoglobin (Hb) and ibuprofen (IBU) as a model protein and drug, respectively. The experimental results indicate that the as-prepared HAP nanorod-assembled hierarchical microflowers have relatively large specific surface area, high biocompatibility, high protein/drug loading capacity and pH-dependent sustained release properties. Thus, the as-prepared HAP nanorod-assembled hierarchical microflowers are promising for the applications in protein/drug delivery.