Diagnosis of tumour hypoxia is an important aspect in determining the
course of tumour therapy. In this study, we developed a novel imaging agent, 99mTcethylenedicysteine-
bis-misonidazole (99mTc-EC-MISO), for diagnosing tumour hypoxia.
We used 2-nitroimidazole as a reactant to synthesize the amino derivative of
misonidazole (MISO) in the first step and then conjugated the di-amino derivative of
MISO to the chelating agent ethylenedicysteine (EC) for labelling 99mTc in the second
step. 99mTc-pertechnetate (99mTcO4
-) was reduced by tin chloride (SnCl2) for radiolabeling.
The radiochemical purity was up to 94%. Tissue biodistribution and SPECT/CT imaging studies were conducted
on subcutaneous gliomal tumour-bearing mice. The tumour-to-muscle ratio in the 99mTc-EC-MISO group increased with
time, up to 4.6 at 4 h after injection. SPECT/CT imaging confirmed that the tumours could be visualized clearly with
99mTc-EC-MISO at 2 h. By introducing a second 2-nitroimidazole redox centre, an apparent hypoxic accumulation of this
novel 99mTc-labeled imaging agent in the tumour was observed.
Keywords: Tumour hypoxia, imaging agent, misonidazole (MISO), technetium-99m-labeled.
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