Development of 177Lu-DOTA-Dendrimer and Determination of Its Effect on Metal and Ion Levels in Tumor Tissue

Dendrimers are synthetic nanomolecules with well-defined chemical structures. Different strategies have been used for radiolabeling dendrimers with different radioisotopes. In this study, the aim was to conjugate dendrimers with 177Lu, to observe the in vivo behavior of the labeled compound and to measure the elementary changes in tumor tissue that could be caused by ionizing radiation. PAMAM G4 dendrimers conjugated with DOTA were labeled with 177Lu. The radiolabeled compound was characterized and its stability was evaluated by reverse phase high performance liquid chromatography. Radiolabeling yield was >98% and stable for 24 hours. Biodistribution studies of 177Lu-DOTA-dendrimers in C57BL/6 melanoma-bearing mice showed blood clearance with hepatic and renal depuration and tumor uptake. The concentrations of Br, Ca, Cl, Fe, K, Mg, Na, Rb, S, and Zn were determined in tumor tissues of C57BL/6 mice treated with 177Lu-DOTA-dendrimers and in untreated mice. The results showed decreased concentrations of Br (62%), Ca (24%), Cl (51%), K (12%) and Na (60%) and increased concentrations of Fe (8%), Mg (28%), Rb (100%), S (6%) and Zn (4%) in tumor tissues of mice treated with 177Lu-DOTA-dendrimers. These data may be useful to evaluate changes in tumor tissues as indicators of damage that could be caused by ionizing radiation.