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Electron Paramagnetic Resonance Study of Carbonated Hydroxyapatite Synthesized through Calcium Phosphate Cements



Alline F. Myers, Shozo Takagi, Stanislav Frukhtbeyn, Laurence Chow, Veronika Szalai, Lonnie Cumberland, Ileana Pazos, Eaman Karim


Ionizing radiation-induced paramagnetic defects in calcified tissues like tooth enamel are indicators of irradiation dose. Hydroxyapatite (HA), the principal constituent in these materials, incorporates a variety of anions (CO32, F, Cl, SiO44 ) and cations (Mn2+, Li+, Cu2+, Fe3+, Mg2+) that directly or indirectly contribute to formation of stable paramagnetic centers upon irradiation. Here, we used an underexploited synthesis method based on the ambient-temperature setting reaction of a self-hardening calcium phosphate cement (CPC) to create carbonate-containing hydroxyapatite (CHA) and investigate its paramagnetic properties following -irradiation. Powder X-ray diffraction and IR spectroscopic characterization of the hardened CHA samples indicate formation of pure B-type CHA cement with a low degree of crystallinity. CHA samples exposed to -radiation doses ranging from 10-3 kGy to 102 kGy exhibited an EPR signal from an orthorhombic CO2• free radical. At -radiation doses from 30 kGy to 150 kGy, a second signal emerged that is assigned to the CO3• free radical. We observed that formation of this second species is dose-dependent, which provided a means to extend the useful dynamic range of irradiated CHA to doses > 30 kGy. These results indicate that CHA synthesized via a CPC cement is a promising substrate for EPR-based dosimetry. Further studies on the CHA cement are underway to determine the suitability of these materials for a range of biological and industrial dosimetry applications.
Inorganic Chemistry


Calcium phosphate cement, Carbonated hydroxyapatite cement, Electron paramagnetic resonance dosimetry, Bio-dosimetry, Setting reactions of calcium phosphate cement (CPC) method


Myers, A. , Takagi, S. , Frukhtbeyn, S. , Chow, L. , Szalai, V. , Cumberland, L. , Pazos, I. and Karim, E. (2022), Electron Paramagnetic Resonance Study of Carbonated Hydroxyapatite Synthesized through Calcium Phosphate Cements, Inorganic Chemistry, [online],, (Accessed April 24, 2024)
Created August 5, 2022, Updated November 29, 2022