99mTc-labeling studies of a modified metronidazole and its biodistribution in tumor bearing animal models

A cysteine-based bifunctional chelating agent viz. N-(2'-hydroxybenzyl)-cysteine with a free carboxylic acid group (CAA) was synthesized. Bearing in mind the affinity of localization of nitroimidazoles in hypoxic tissues, this bifunctional chelating agent was coupled to metronidazole (MNZ). The Tc-99m labeling studies of the novel agent (MNZCAA) thus obtained, was carried out and the radiolabeled product was subsequently purified. The complexation yield under optimized condition was similar to85%. Biodistribution studies carried out in Swiss mice bearing 'barcl-95' tumors showed selective accumulation of the injected activity in the tumor (1.70%/g at 30 min p.i.) with renal as well as hepatobiliary clearance. High tumor/muscle ratio (14.7 at 3 h post-injection) of the novel agent indicates considerable promise towards further evaluation. (C) 2003 Elsevier Science Inc. All rights reserved.