Synthesis and biodistribution of a new oxo-technetium-99m bis(aminothiol) complex as a potential melanoma tracer

[I-123]-N-(2-Diethylaminoethyl)-4-iodoben (I-123-BZA) has been the best sci ntigraphic agent described so far far malignant melanoma and ocular melanom a diagnosis. We replaced I-123 by the more convenient radioisotope Tc-99m a nd synthesized four bis(aminoethanethiol) derivatives. We describe the synt hesis of a new oxo-technetium complex (TcO-Cf), prepared in very high yield (radiochemical yield > 95%), that exhibits an affinity for the pigmented t umor cells. This complex was evaluated in vivo in mice,bearing C57B16 murin e melanoma. After injection, a rapid decrease in the radioactivity levels w as noted for all tissues and organs except for eyes (1.26 %ID/g at 1 h and 2.69 %ID/g at 24 h postinjection) and the tumor (1.19 %ID/g at 1 h and 0.80 %ID/g at 24 h postinjection), suggesting a specific in vivo binding of thi s complex to the pigmented cells. These results were compared with those al ready published for three other technetium-99m bis(aminothiol) complexes wi th benzamide derivatives.