Spatial distribution and stability of Gd_0.6Eu_0.4VO₄ nanoparticles injected in mouse ear pinnae

X-Ray Fluorescence (XRF) mapping is employed for the study of the spatial distribution of GdVO₄:Eu nanoparticles (NPs) after their injection into mouse ear pinnae. The injected NP colloids were detectable in a concentration range from 5 to 30 mM in vanadate ions (90–530 nM in NP concentrations). The distribution maps were recorded separately for Gd, Eu, and V and reveal that the three elements are collocalized, indicating the NP stability after the injection. The distribution pattern of the NPs is not homogeneous; they follow bifurcated paths of easy flow demonstrating the complexity of the tissue-colloid interactions. The V–K, Gd-L₃ and Eu-L₃-edge X-ray Absorption Fine Structure (XAFS) spectra of the NPs recorded prior to and after their injection confirm that the integrity of the nanoparticles is preserved after injection. This combined XRF/XAFS analysis paves the way for studies on the long-term fate of injected Gd-containing NPs in tissues.