Labeling, biodistribution and evaluation of [125I] gemcitabine: A potential agent for tumor diagnosis and radiotherapy

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In this study, the optimization of gemcitabine labeling with iodine-125 and its biological evaluation are described. Gemcitabine was labeled via direct electrophilic substitution using chloramine-T as an oxidizing agent. The optimum amounts of reactants were 75 μg gemcitabine, 75 μg chloramine-T and 18MBq carrier-free Na125I. The labeled gemcitabine was stable for more than 20 h. Results of the in vivo evaluation revealed that the new tracer, [125I] gemcitabine, tends to localize in tissues with high proliferation rate with preferential accumulation in cancerous tissues. Imaging should be carried at 2-h postinjection. The in vitro cell growth inhibition assay showed that the effect of [125I] gemcitabine was stronger than the effect of tenfold cold gemcitabine, which strongly suggested that its cytotoxicity was mainly due to radiotoxicity rather than chemotherapeutic activity. The binding assay revealed that [125I] gemcitabine uptake by the Ehrlich cells was high and that it bound well to DNA where the decay of the radionuclide introduced lethal irreversible double-strand breaks. Copyright © 2009 John Wiley & Sons, Ltd.

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