Fabrication of monodisperse mesoporous hydroxycarbonate apatite microspheres by emulsion method

Mesoporous hydroxycarbonate apatites have been widely used as bone cavity filling materials and drug delivery systems, but the synthesis of monodisperse microspheres with mesoporous structure presents still a fundamental challenge. This drawback has been addressed by using emulsion method. A cetyltrimethylammonium bromide (CTAB)/Na2HPO4 solution/cyclohexane/n-butanol emulsion system has served as microreactors, in which CaCO3 microspheres (CCMs) are converted to mesoporous hydroxycarbonate apatite microspheres (MHAMs). After soaking CCMs in the emulsion system, hydroxycarbonate apatites are heterogeneously nucleated on the surfaces of CCMs via a dissolution–precipitation reaction. The as-formed hydroxycarbonate apatite nanoparticles aggregate to produce plates with the average thickness of ∼40 nm and form mesopores with the pore size of ∼3.9 nm and ∼7.4 nm among them. In addition, the formation mechanism of MHAMs has been discussed further in the present work.