ALBUMIN MICROSPHERES LABELED WITH GA-67 BY CHELATION - CONCISE COMMUNICATION

Abstract

Albumin microspheres were synthesized with EDTA and DTPA [diethylenetriaminepentaacetic acid] chelating groups covalently bound to their surface. The microspheres may be labeled with 67Ga at high yield (97 .+-. 2%) by transcomplexation from a 0.1 M 67Ga-acetate solution. With EDTA microspheres the resulting label dissociates only slightly after 24 h in 50% plasma at 37.degree. C; with DTPA microspheres the label shows no detectable dissociation over this period. By contrast, microspheres without chelating groups lose their label virtually completely under these conditions. Following i.v. administration of sized 67Ga DTPA microspheres in mice, about 84 .+-. 16% of the activity localizes in the lungs at 5 min, with 60 .+-. 7% remaining after 2 h. Since labeling is by chelation, the microspheres may also be tagged with other metallic radionuclides.