Rapid microwave synthesis of hydroxyapatite phosphate microspheres with hierarchical porous structure

Hierarchical Hydroxyapatite (Ca10(PO4)6(OH)2, HA) microspheres can be applied as microcarriers in cell carriers and drug delivery. However, it is difficult to prepare monodispersed and hierarchical microspheres in short time with conventional method. Here, we report the preparation of hierarchical HA microspheres through a novel microwave-assisted method in several minutes, where similar structured calcium carbonate (CaCO3) microspheres acts as sacrificial hard-templates. The SEM images indicated that surface microstructure and microspheres size were effectively controlled by changing starting parameters such as microwave react time and stirring speed. XRD patterns and BET results further proved that the pure HA microspheres with great specific surface area can be prepared in a short time. The Ca ions release of samples showed that the degradation of HA microspheres decreased with microwave processing time of samples. Drug release of samples showed that on one hand vancomycin release concentration decreased with microwave processing time of samples, on the other hand increased obviously with the lower pH value of buffer solution. Human osteoblasts-like cells were cultured with different concentration of microspheres extracts to investigate in vitro biocompatibility. The results of the CCK-8 assay and Live/Dead staining proved that the cells grew well in all sample extracts, suggesting that cells responded well to the microspheres. Our work provides a novel and rapid way to produce hierarchical HA microspheres for bone repair or drug delivery.