Examination of Co-complexes for radiolabeling of platelets in positron emission tomographic studies

Oxine, tropolonate, and mercaptopyridine-N-oxide (MPO) have been widely use d with In-111 for platelet labeling. The use of positron emission tomograph y (PET) radioisotopes for platelet labeling would offer a higher sensitivit y and resolution over conventional imaging. The medium half-life PET radioi sotope Co-55 (t(1/2)=18.2 hours) would enable quantitative uptake and cell kinetic studies with radiolabeled platelets. To identify the optimal comple x for radiolabeling of platelets with Co-55, we investigated the platelet u ptake of Co-57-oxine, Co-57-tropolonate, and Co-57-MPO in varying different parameters. The platelet uptake of Go-complexes was generally low (5-12%), dependent on time and temperature of incubation and density of platelets b ut independent of the amount of radioactivity. These findings are not promi sing for potential PET application. (C) 1999 Elsevier Science Ltd. All righ ts reserved.