Cell labelling and cell damage with indium-111 acetylacetone-an alternative to indium 111 oxine

The labelling of HeLa S3 cells with 111In acetylacetone (111In-acac) was studied together with cell damage, measured by the reduction in colony-forming ability of labelled cells. Using 2 X 10(5) cells/ml in Hepes saline buffer at pH 7.6 incubated with 7.4-185 kBq (0.2-5.0 microCi)/ml 111In-acac, containing 0.19% acetylacetone for 15 minutes at room temperature, 60-80% 111In was bound to the cells. The cell binding was linear with activity and resulted in an exponential reduction in colony forming ability and a D0 of 26 kBq (0.7 microCi)/2 X 10(5) cells. Radiation was shown to be the major cause of cell damage. It is concluded that 111In-acac is preferable to 111In oxine because it is soluble in physiological buffers, which eliminates the use of ethanol; it is quick and easy to prepare; and compared with previous results using HeLa S3 cells labelled with 111In oxine, 111In-acac gives much more reproducible results and is no more toxic. Clinically 111In-acac was shown to give similar results to 111In oxine.