Encapsulation and retention of 225AC, 223Ra, 227Th, and decay daughters in zircon-type gadolinium vanadate nanoparticles

Unwanted targeting of healthy organs caused by the relocation of radionuclides from the target site has been one of the limiting factors in the widespread application of targeted alpha therapy in patient regimens. GdVO4 nanoparticles (NPs) were developed as platforms to encapsulate a-emitting radionuclides Ra-223, Ac-225, and Th-227, and retain their decay daughters at the target site. Polycrystalline GdVO4 NPs with different morphologies and a zircon-type tetragonal crystal structure were obtained by precipitation of GdCl3 and Na3VO4 in aqueous media at room temperature. The ability of GdVO4 crystals to host multivalent ions was initially assessed using La, Cs, Bi, Ba, and Pb as surrogates of the radionuclides under investigation. A decrease in Ba encapsulation was obtained after increasing the concentration of surrogate ions, whereas the encapsulation of La cations in GdVO4 NPs was quantitative (similar to 100%). Retention of radionuclides was assessed in vitro by dialyzing the radioactive GdVO4 NPs against deionized water. While Th-227 was quantitatively encapsulated (100%), a partial encapsulation of Ra-223 (similar to 75%) and Ac-225 (>60%) was observed in GdVO4 NPs. The maximum leakage of Fr-221 (1st decay daughter of Ac-225) was 55.4 +/- 3.6%, whereas for Ra-223 (1st decay daughter of Th-227) the maximum leakage was 73.0 +/- 4.0%. These results show the potential of GdVO4 NPs as platforms of alpha-emitting radionuclides for their application in targeted alpha therapy.