[The chemistry of indium complexes]

There are no complexes of indium known to occur naturally in the human. Several radiopharmaceuticals labelled with In-111 or In-113m have been investigated for their application to localization studies. Most of the indium radiopharmaceuticals have a weak thermodynamic stability and, therefore, no specificity. It is known that such compounds are converted in vivo to In-labelled transferrin. Experiments to increase the thermodynamic stability, thereby leading to an increase in specificity have been followed up in two directions: Modification of polyaminocarboxylic acids (e.g. EDTA, DTPA) by reaction with a benzene diazonium salt or by substitution with methylene phosphoric acid instead of acetic acid in the EDTA molecule. Application of lipid soluble chelates of indium-111 for blood cell labelling (e.g. erythrocytes, leucocytes and platelets). The results are promising.