Carbonate substitution in the mineral component of bone: Discriminating the structural changes, simultaneously imposed by carbonate in A and B sites of apatite

Honey Madupalli, Barbara Pavan, Mary M.J. Tecklenburg

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113 Scopus citations

Abstract

The mineral component of bone and other biological calcifications is primarily a carbonate substituted calcium apatite. Integration of carbonate into two sites, substitution for phosphate (B-type carbonate) and substitution for hydroxide (A-type carbonate), influences the crystal properties which relate to the functional properties of bone. In the present work, a series of AB-type carbonated apatites (AB-CAp) having varying A-type and B-type carbonate weight fractions were prepared and analyzed by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and carbonate analysis. A detailed characterization of A-site and B-site carbonate assignment in the FTIR ν3 region is proposed. The mass fractions of carbonate in A-site and B-site of AB-CAp correlate differently with crystal axis length and crystallite domain size. In this series of samples reduction in crystal domain size correlates only with A-type carbonate which indicates that carbonate in the A-site is more disruptive to the apatite structure than carbonate in the B-site. High temperature methods were required to produce significant A-type carbonation of apatite, indicating a higher energy barrier for the formation of A-type carbonate than for B-type carbonate. This is consistent with the dominance of B-type carbonate substitution in low temperature synthetic and biological apatites.

Original languageEnglish
Pages (from-to)27-35
Number of pages9
JournalJournal of Solid State Chemistry
Volume255
DOIs
StatePublished - Nov 2017

Keywords

  • A-type carbonate
  • B-type carbonate
  • Carbonated apatite
  • Infrared
  • Microstructural analysis
  • XRD

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