Co, Fe and Ga chelates for cell labelling: A potential use in PET imaging?

The radiolabelling of blood cellular elements with PET radionuclides offers a higher sensitivity and resolution than conventional imaging, but short-l ived PET radionuclides have limited clinical use in cell labelling. Medium half-life PET radionuclides, such as Co-55 (t(1/2) = 18.2 h), Fe-52 (t(1/2) = 8.3 h) and Ga-66 (t(1/2) = 9.4 h), enable quantitative uptake and cell k inetic studies with radiolabelled blood cellular elements. Co(II) oxine, Co (III) tropolonate, Fe(III) oxine, Ga(III) oxine and Ga(III) MPO were prepar ed using gamma-emitting radionuclides and a number of cell labelling parame ters were investigated. The uptake of Co-57(II) oxine into erythrocytes was only 37%, and 65% of the activity eluted from the cells in cell-free plasm a within 30 min. In contrast, high leukocyte and erythrocyte labelling effi ciencies (> 90%) were obtained with Co-57(III) tropolonate containing cobal t carrier and the elution in cell-free plasma over 4 h was < 8%. High label ling efficiencies were also observed with Fe-59(III) oxine and Ga-67-MPO an d the elution from leukocytes over 4 h was < 25%. We conclude that Co(III) tropolonate, Fe(III) oxine and Ga-MPO may be useful for radiolabelling leuk ocytes for PET investigations. ((C) 1999 Lippincott Williams & Wilkins).