Preparation of 99mTc-metronidazole as a model for tumor imaging

Metronidazole (MTNZ) is an antiprotozoa drug, could be labeled with the 99mTc. MTZL could be used as an ideal vehicle to deliver radioactive decay energy of 99mTc to the sites of tumor, thus facilitate tumor imaging. The process of labeling was done using tin chloride as reducing agent. The optimum conditions required to label 25 μg MTZL were 100 lg stannous chloride, 30 min reaction time, room temperature at pH 7-9 using 0.5 M phosphate buffer. The radiochemical purity of the labeled compound, at the above conditions, was determined using paper chromatography. The yield was about 93%. About 2.5 x 106 of Ehrlich Ascites Carcinoma (EAC) was injected intrapritoneally (i.p) to produce ascites and intramuscularly (i.m) in the right thigh to produce solid tumor in female mice. Biodistribution studies were carried out by injecting solution of 99mTc-MTZL in normal and tumor bearing mice. The uptake in ascites was over 5% of the injected dose per gram tissue body weight, at 4 h post injection and above 4% in solid tumor. These data revealed localization of the tracer in the tumor tissues with high percentage sufficient to use 99mTc MTZL as promising tool for diagnosis of tumor. (author)