Fabrication and osteoregenerative application of composition-tunable CaCO3/HA composites

A series of porous CaCO3/HA composites have been produced with an increased molar percentage of HA from 0, 10, 25, 50, 75 to 100%. The compression strength of the CaCO3/HA composites increases proportionally before reaching 50% and gradually levels off with a further increase up to 100%. The 50% CaCO3/HA composite, with a similar compression strength to natural bone, has been evaluated in vitro and in vivo, showing great potential for osteoregenerative applications. A three-step chemical process for preparing the CaCO3/HA composites has been revealed by time-dependent XRD analysis: (i) CaCO3 -> CaO + CO2 up arrow, (ii) 10CaO + 6(NH4)(2)HPO4 -> Ca-10(PO4)(6)(OH)(2) + 12NH(3) up arrow + 8H(2)O up arrow, and (iii) CaO + CO2 -> CaCO3/Ca(OH)(2) + CO2 -> CaCO3 + H2O. The initial formation of porous CaO by a fast release of CO2 at high temperature leads to the production of the porous CaCO3/HA composites. Such understanding may allow us to extend this solid-phase fabrication approach to various other porous composites with controlled compositions for promising applications.