Gamma-Camera Direct Imaging of the Plasma and On/Intra Cellular Distribution of the ^99mTc-DPD-Fe₃O₄ Dual-Modality...

The radiolabeled iron oxide nanoparticles constitute an attractive choice to be used as dual-modality contrast agents (DMCAs) in nuclear medical diagnosis, due to their ability to combine the benefits of two imaging modalities, for instance single photon emission computed tomography (SPECT) with magnetic resonance imaging (MRI). Before the use of any DMCA, the investigation of its plasma extra- and on/intra cellular distribution in peripheral human blood is of paramount importance. Here, we focus on the in vitro investigation of the distribution of ^99mTc-DPD-Fe₃O₄ DMCA in donated peripheral human blood (the ligand 2-3-dicarboxypropane-1-1-diphosphonic-acid is denoted as DPD). Initially, we described the experimental methods we performed for the radiosynthesis of the ^99mTc-DPD-Fe₃O₄, the preparation of whole blood and blood plasma samples, and their incubation conditions with ^99mTc-DPD-Fe₃O₄. More importantly, we employed a gamma-camera apparatus for the direct imaging of the ^99mTc-DPD-Fe₃O₄-loaded whole blood and blood plasma samples when subjected to specialized centrifugation protocols. The direct comparison of the gamma-camera data obtained at the exact same samples before and after their centrifugation enabled us to clearly identify the distribution of the ^99mTc-DPD-Fe₃O₄ in the two components, plasma and cells, of peripheral human blood.