Hydroxyapatite particles as carriers for ²²³Ra

Systematic investigation of optimal conditions for preparation and in vitro stability of HAP particles labeled with 223Ra, that could be considered as promising candidates for targeted α-therapy, has been carried out. Two different approaches to HAP labelling were tested: sorption of Ra2+ on pre-synthesized HAP-particles and incorporation of Ra2+ into the structure of HAP during its synthesis. Two textural forms of HAP particles were used—nanoparticles and particles with the diameter of 350 ± 20 μm. Kinetics of 223Ra sorption on HAP of different particle size and desorption in 0.9 % NaCl solution were studied. The influence of solution acidity and solid to liquid phase ratio on sorption of Ra was evaluated and the sorption yield up to 98 % was achieved. It was found that the optimal conditions for the sorption included synthesis of HAP nanoparticles in the presence of 223Ra at pH values of 4–7 followed by annealing at 900 °C. In this case subsequent cumulative desorption of Ra was <5 % of initial activity.