Hydrothermal fabrication of porous hollow hydroxyapatite microspheres for a drug delivery system

Porous hollow hydroxyapatite microspheres (PHHMs) are the promising biomaterials, owing to their excellent biocompatibility, biodegradability and bioactivity. PHHMs have been used as drug controlled carriers due to their advantages such as large drug loading capacity, nanochannels for drug loading and release and high specific surface area. In this study, PHHMs were prepared successfully in Na2HPO4 solution by an anion-exchange process using vaterite CaCO3 through a hydrothermal method. The previous vaterite CaCO3 was synthesized by a polymer-templated method in the poly(styrene sulfonic acid) sodium salt (PSS) aqueous solutions. The PHHMs have a size distribution from 0.8 to 2.0 μm, with an average pore size of about 24.3 nm. The wall of PHHMs is constructed with building units of hydroxyapatite nanofibers with an average length of 300 nm and an average width of 20 nm. The PHHMs displayed a high drug loading capacity and pH-responsive sustained-controlled drug release behavior when we used doxorubicin hydrochloride (DOX) as a loading drug. Moreover, the controlled drug release system showed a high ability to kill cancer cells and less damage to normal cells. These results indicated that PHHMs are promising for applications in various biomedical fields such as drug delivery system and oncotherapy.