Gadolinium vanadate nanocrystals as carriers of α-emitters (²²⁵Ac, ²²⁷Th) and contrast agents

Gadolinium vanadate (GdVO₄) core and core + 2 shell nanocrystals (NCs) were evaluated for in vitro retention of ²²⁵Ac, ²²⁷Th, and their first decay daughters, ²²¹Fr and ²²³Ra, respectively. GdVO₄ NCs with a tetragonal crystal system (zircon-type) and spherical morphology were obtained by precipitation of GdCl₃ and Na₃VO₄ using sodium citrate as a complexing agent. The growth of two nonradioactive GdVO₄ shells on both Gd(²²⁵Ac)VO₄ and Gd(²²⁷Th)VO₄ core NCs was demonstrated by an increase of 0.7 nm and 2 nm in the crystallite size, respectively. The maximum leakage of ²²⁵Ac was 15% and 2.4% from core and core + 2 shells, whereas the leakage of ²²⁷Th was 3% and 1.5%, respectively. The presence of two nonradioactive GdVO₄ shells increased the retention of ²²¹Fr and ²²³Ra by 20% and 15% with respect to core NCs. Furthermore, a longitudinal proton relaxivity, r₁ = 0.9289 s⁻¹ mM⁻¹, confirmed their potential application as contrast agents for magnetic resonance imaging. In summary, GdVO₄ NCs show promising capabilities as radionuclide carriers with partial retention of decay daughters and as contrast agents for theranostic applications.