Oppositely charged polyurethane/hydroxyapatite(PU/HA) microspheres were successfully prepared by using the self-emulsifying method,in which 2,2-Bis(hydroxymethyl) propionic acid(DMPA) and N-Methyldiethanolamine(MDEA) was used as chain extender,respectively.The self-assembled gel system was formed by electrostatic force between oppositely charged microspheres.The physicochemical properties of these microspheres were characterized and analyzed by means of SEM,Laser particle size analyzer,ζ potentiometer,XRD a...