In vitro studies of radium-223 and actinium-225 labelled α-zirconium phosphate as potential carrier for alpha targeted therapy

Nanoparticles of α-zirconium phosphate (α-ZrP) were selected and tested as potential carriers of ²²³Ra and ²²⁵Ac. Nanoparticles of α-ZrP were prepared by the reaction of zirconium oxychloride octahydrate aqueous solution with sodium dihydrogen phosphate solution in hydrochloric acid under reflux. The prepared particles were washed by deionised water and then redispersed in ultrapure water. The size of the particles was determined using dynamic light scattering method and the Ζ-potentials were also measured. Consequently, samples were labelled in aqueous solution with ²²³Ra and ²²⁵Ac. The labelling yield exceeded 98 % in most cases both for ²²³Ra and ²²⁵Ac. Subsequently, in vitro stability studies were carried out in four biological matrices: blood serum, blood plasma, saline and 5 % albumin solution during 48 h period. Measurements of released activities revealed that samples exhibit the highest stability in saline. Released activity of ²²³Ra, ²²⁵Ac and their daughter radionuclides was around 0,5 %. On the other hand, the lowest stability was shown in blood plasma for ²²³Ra, where released activity was above 15 % and 18 % for ²¹¹Pb and ²¹¹Bi after 48 h. In blood serum was measured highest release activity for ²²⁵Ac (close to 18 %) and its daughter radionuclides ²²¹Fr (more than 20 %) and ²¹³Bi (above 32 %).