ИСТИНА

Alpha-emitters are of the great interest for nuclear medicine due to the high linear energy transfer of α-particles and recoil nuclei. A pathlength of α-particles in biological tissue is much less than that of β-particles and comparable to a cell size (10-100 µm). Being delivered to the tumor cells, α-particles provide its targeted destruction and minimal damage to surrounding organs. Among various α-emitters, 223Ra is one of the promising candidates for targeted α-therapy. A radiopharmaceutical Xofigo® on the basis of 223RaCl2 is registered and produced by Bayer Company for the therapy of bone metastases. Another approach is a targeted delivery of 223Ra using various transporters to the cancer cells such as peptides, liposomes or various inorganic carriers. Hydroxyapatite (HAP) particles could be considered as possible carriers of Ra. Two different approaches to HAP labeling were tested: sorption of Ra on pre-synthesized HAP-particles and insertion of Ra into the structure of HAP during its synthesis. Two textural forms of HAP particles were used – nanoparticles and particles with the diameter of 300±20 μm. Kinetics of sorption of Ra on HAP of different particle size and desorption of Ra in 0.9 % NaCl solution was studied. The influence of solution acidity and solid to liquid phase ratio on sorption of Ra was evaluated and the sorption yield of up to 98% was achieved. It was found that the optimal conditions for the sorption includes synthesis of HAP nanoparticles in the presence of 223Ra at pH 4-7 and following annealing at 900 ⁰C. In this case subsequent cumulative desorption of Ra is less than 5% of initial activity. Cross-sectional distribution of Ra inside a HAP particle with diameter 450-550 μm was studied by autoradiography on the plates of polyallildiglycol carbonate. Kinetics of Ra diffusion into a large HAP particle was estimated. Using of HAP as carriers is regarded to be prospective for 223Ra α-therapeutic applications due to the similarity of properties of radium and calcium, as well as bioavailability and biocompatibility of hydroxyapatite. This work was supported by Russian foundation for basic research with grant № 16-33-00200.