Cell labelling with 67Ga-citrate.

A method of cell labelling with carrier-free 67Ga-citrate, based on a co-binding with iron from ferric lactate has been developed. 67Ga-binding has a direct relationship with the iron incorporation by the cell. Using this method Ehrlich ascites tumor cells increase their uptake from 5% (no ferric lactate) to 89% (5 mumol of ferric lactate). Erythrocytes have shown the same pattern of 67Ga-binding. In vivo cytotoxic assays (ascites formation and animal survival) have demonstrated the lack of cytotoxicity of ferric lactate under these experimental conditions. Electrophoretic analyses of 67Ga-labelled tumor cells and erythrocytes have shown the absence of free 67Ga-citrate.