Hydroxyapatite particles as carriers for 223Ra

Systematic investigation of optimal conditions for preparation and in vitro stability of HAP particles labeled with Ra-223, that could be considered as promising candidates for targeted alpha-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 mu m. Kinetics of Ra-223 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 Ra-223 at pH values of 4-7 followed by annealing at 900 A degrees C. In this case subsequent cumulative desorption of Ra was < 5 % of initial activity.