Ligand-exchange reaction of labile "3+1"Tc-99m(V) complexes with SH group-containing proteins

The reactivity of labile 3 + 1 mixed-ligand Tc-99m complexes of the type [( TcO)-Tc-99m(SES)(RS)] with SES being a tridentate dithiol ligand and glutat hione or dimethyleysteamine as monodentate ligands RSH towards proteins was investigated in vitro and in vivo. It was found that the complexes undergo reversible transchelation reactions with SH group-containing components of blood such as albumin or haemoglobin. High labelling yields were obtained when 3 + 1 complexes with the tridentate SSS ligand were used. The biodistr ibution of blood proteins labelled by ligand exchange reaction with the [(T cO)-Tc-99m(SSS)] or [(TcO)-Tc-99m(SNMeS)] core was studied and compared wit h the in vivo distribution of the labile 3 + 1 complexes containing glutath ione as monodentate ligand. (C) 2001 Elsevier Science Ltd. All rights reser ved.