Chemical and structural characterization of selenium-incorporated hydroxyapatite

Alkan, Barış
In case of severe bone damage or fracture, synthetic bone grafts have long been applied for replacing natural bone tissue. Recent advances in this area have led to development of dual-functional synthetic hard tissue analogs exhibiting high biocompability/osteoconductivity together with therapeutic effect. Metallic ions are promising therapeutic agents in treatment of bone tumors due to their high physiological stability and availability compared to other alternative therapeutic agents such as recombinant proteins, therapeutic nucleic acids and anti-cancer drugs. Selenium, in that respect, is effective therapeutic agent with promising anti-oxidant and anti-carcinogenic effect when used in proper doses. In this study, selenium-incorporated hydroxyapatite (HAp:Se) particles have been synthesized by modified aqueous precipitation method using calcium (Ca(NO3)2•4H2O) and phosphate ((NH4)2HPO4) salts with sodium selenite (Na2SeO3). The effect of Se incorporation in different amounts on the physical, chemical properties and crystal structure of resultant HAp powders have been explored. Complete chemical identification was performed with spectroscopical chemical analyses including Fourier transform infrared and x-ray photoelectron spectroscopy to elucidate the mechanism and chemical nature of Se incorporation in HAp. Meanwhile, transmission electron microscopy and x-ray diffraction studies by Rietveld refinement have conducted to explain changes in the HAp crystallite and crystal structure upon Se incorporation. The results indicate that vi well-incorporated selenite ions in HAp mostly accommodate near very top surface of HAp (1-2 nm). Also, position of Se ions in HAp crystal structure were estimated to be inside phosphate tetrahedral with limited extend of Se ions. B-type carbonation (3-5 wt. %), nanocrystalline structure and low crystalline surface of HAp:Se particles are believed to lead to high biocompatibility and increased solubility of these particles. Also, anti-cancer effect of Se ion incorporates in HAp nanoparticles are associated with two-step release of Se ionic species; first surface release of them in high extents and subsequently release from HAp:Se crystallites in low extends; therefore, initial release kinetics of Se ions are believed to be critical in biological tests.
Citation Formats
B. Alkan, “Chemical and structural characterization of selenium-incorporated hydroxyapatite,” M.S. - Master of Science, Middle East Technical University, 2015.