Biomineralization synthesis of hollow microspheres of hydroxyapatite using tea saponin as a template

Porous hollow hydroxyapatite (HA) microspheres were synthesized by biomineralization using Ca(NO3)2 · 4H2O and (NH4)3PO4 · 3H2O as starting materials and tea saponin as a template. With increasing amounts of tea saponin, the HA morphology exhibited a variation from irregular floccules to rod-like, which formed a spherical prototype, and then grew into porous hollow microspheres. With further increase in the tea saponin concentration, the rods became sheet-like and then formed cross-flakes. A possible mechanism for this morphology change was also discussed.