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

Abstract

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↑, (ii) 10CaO + 6(NH₄)₂HPO₄ → Ca₁₀(PO₄)₆(OH)₂ + 12NH₃↑ + 8H₂O↑, 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.