engleski

Thermal stability of gamma radiation induced radicals in ion-substituted hydroxyapatites

Hydroxyapatite (HA, Ca10(PO4)6(OH)2) is the thermodynamically most stable calcium phosphate phase and also among the most frequently used hard tissue regeneration materials. However, bone mineral itself is non-stoichiometric, ion- substituted, poorly crystalline HA. Inspired by nature, doping of HA with ions which have different biological roles, like Mg, Si, Zn, Sr, is applied as a method of improving its bioactivity. Frequent method of sterilization of such materials is γirradiation, which can result in formation of radicals and structural changes in the material itself. Therefore, for the safe application of ion- substituted HA, it is important to determine not only the stability of the formed radicals, but also get an insight in the induced structural changes. In this work, HA and 3 different ion-substituted HAs doped with 2% Mg ; 2% Mg + 0.4% Si and 2% Mg + 1.25% Si were irradiated to 25 kGy with 60Co γ-rays and studied. Their relative radical concentration, determined by electron paramagnetic resonance (EPR) spectroscopy, was monitored as a function of time at different temperatures in the presence of air. The temperature and time dependence of each sample is presented and discussed, as well as the changes in the X-ray diffraction patterns.

hydroxiapatite ; ion-substitution ; EPR spectroscopy

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