No carrier added preparations of ‘3 + 1’ mixed-ligand 99mTc complexes

The no carrier added (n.c.a.) preparation of potentially receptor-binding ‘3 + 1’ mixed-ligand technetium complexes has not so far been successfully accomplished. This article deals with our results in the preparation of n.c.a. Tc complexes with tridentate S-S-S or S-N-S ligands and a series of bulky monothiolato ligands. It was found that Tc(V) gluconate or Tc(V) ethylene glycolate are suitable precursors for the complex formation. In a two-step procedure consisting of a reaction of the monothiolato ligand with the precursor and subsequent addition of the tridentate ligand, the desired ‘3 + 1’ mixed-ligand complexes are formed with yields of up to 90%. Low ligand concentrations and pH 9–10 promote the formation of the technetium compounds. A comparison of their analytical properties (TLC, HPLC) and biodistribution data of carrier added and no carrier added technetium complexes show the identity of the investigated compounds.