GA-68 LABELING OF ALBUMIN AND ALBUMIN MICROSPHERES

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 20  (5) , 428-433
Abstract
Because of the high stability constant of Ga transferrin, the formation of a protein that will be stable in vivo and labeled with 68Ga (a positron emitter) requires preliminary coupling of a strong chelating group to the protein. A reaction developed by Krejcarek and Tucker was used in which DTPA [diethylenetriaminepentaacetic acid] is coupled to proteins by the formation of an amide bond. Using human serum albumin (HSA) as a model, the efficiency of the reaction of HSA with the mixed acid anhydride of the quarternary triethyl ammonium salt of DTPA and butyl formate was studied as a function of the ratio of albumin to DTPA. After purification of the DTPA-labeled HSA, it is possible to prepare 68Ga-labeled albumin in high yield by chelation of the 68Ga with the DTPA-labeled protein. In vitro and in vivo stability studies showed that the labeled protein was stable over a period of several hours. The same type of bifunctional chelate has been used to attach 68Ga to HSA microspheres.

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