Integrity of 111In-radiolabeled superparamagnetic iron oxide nanoparticles in the mouse

IntroductionIron-oxide nanoparticles can act as contrast agents in magnetic resonance imaging (MRI), while radiolabeling the same platform with nuclear medicine isotopes allows imaging with positron emission tomography (PET) or single-photon emission computed tomography (SPECT), modalities that offer better quantification. For successful translation of these multifunctional imaging platforms to clinical use, it is imperative to evaluate the degree to which the association between radioactive label and iron oxide core remains intact in vivo.MethodsWe prepared iron oxide nanoparticles stabilized by oleic acid and phospholipids which were further radiolabeled with 59Fe, 14C-oleic acid, and 111In.ResultsMouse biodistributions showed 111In preferentially localized in reticuloendothelial organs, liver, spleen and bone. However, there were greater levels of 59Fe than 111In in liver and spleen, but lower levels of 14C.ConclusionsWhile there is some degree of dissociation between the 111In labeled component of the nanoparticle and the iron oxide core, there is extensive dissociation of the oleic acid component.