title: Novel synthesis and characterization of an AB-type carbonate-substituted hydroxyapatite.
abstract: A novel synthesis route has been developed to produce a high-purity mixed AB-type carbonate-substituted hydroxyapatite (CHA) with a carbonate content that is comparable to the type and level observed in bone mineral. This method involves the aqueous precipitation in the presence of carbonate ions in solution of a calcium phosphate apatite with a Ca/P molar ratio greater than the stoichiometric value of 1.67 for hydroxyapatite (HA). The resulting calcium-rich carbonate-apatite is sintered/heat-treated in a carbon dioxide atmosphere to produce a single-phase, crystalline carbonate-substituted hydroxyapatite. In contrast to previous methods for producing B- or AB-type carbonate-substituted hydroxyapatites, no sodium or ammonium ions, which would be present in the reaction mixture from the sodium or ammonium carbonates commonly used as a source of carbonate ions, were present in the final product. The chemical and phase compositions of the carbonate-substituted hydroxyapatite was characterized by X-ray fluorescence and X-ray diffraction, respectively, and the level and nature of the carbonate substitution were studied using C-H-N analysis and Fourier transform infrared spectroscopy, respectively. The carbonate substitution improves the densification of hydroxyapatite and reduces the sintering temperature required to achieve near-full density by approximately 200 degrees C compared to stoichiometric HA. Initial studies have shown that these carbonate-substituted hydroxyapatites have improved mechanical and biologic properties compared to stoichiometric hydroxyapatite.
authors.affiliation: IRC in Biomedical Materials, Queen Mary, University of London, Mile End Road, London, E1 4NS, United Kingdom. I.R.Gibson@qmw.ac.uk
authors.forename: Iain R
authors.initials: IR
authors.lastname: Gibson
authors.forename: William
authors.initials: W
authors.lastname: Bonfield
mesh_terms: D018786:Bone Substitutes / Q000138:chemical synthesis* / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry*; D006882:Hydroxyapatites / Q000138:chemical synthesis* / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D018786:Bone Substitutes; D002254:Carbonates; D006882:Hydroxyapatites