Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

The aim of the paper was to synthesize and investigate the conjugate of the “4+1” mixed-ligand technetium(III) complex with the vasopressin peptide-^99mTc(NS₃)(CN-AVP). The overexpression of vasopressin receptor V2 has been found in the case of small-cell lung cancer.
The “4+1” mixed-ligand technetium complex consists of central metal ion Tc(III) coordinated simultaneously by a tetradentate NS₃ tripodal chelator tris(2-mercaptoethyl)-amine and a monodentate isocyanide ligand, previously coupled with the selected biomolecule. The identity of the ^99mTclabelled vasopressin peptide was corroborated by investigation of the analogous rhenium compound. The ^99mTc-labelling vasopressin conjugate was formed in two-step synthesis, via the ^99mTc-EDTA intermediate complex, with the final yield of 95%. After 24 h of incubation of the conjugate in the 10 mM solution of histidine or cysteine, the obtained highperformance liquid chromatography chromatograms have shown the existence of one radioactive species, with the retention time characteristic for the complex studied. The log D value of −0.48±0.02 for the 99mTclabelled vasopressin peptide was found. This value (higher than the lipophilicity of the free vasopressin peptide equal to −2.15) can be corrected by introducing a hydrophilic group, R, at the periphery of the NS₃ ligand.