Characterization of antibody-chelator conjugates: determination of chelator content by terbium fluorescence titration

Abstract

Fluorescence titrations were performed by adding varying mole ratios of terbium(III) to antibody conjugates formed by benzyl isothiocyanate derivatives of three different polyaminopolycarboxylate chelators (NTA, EDTA, and DTPA) and the results compared to values for average chelator content obtained by cobalt-57 binding assays. For two different murine monoclonal antibodies, the average chelator content obtained by terbium fluorescence titration correlated closely with that measured by the cobalt-57 binding assay. It is concluded that lanthanide fluorescence titrations provide a useful alternative to radiometal binding assays for the determination of chelator content in protein-chelator conjugates.

Spectrophotometric method for the determination of a bifunctional DTPA ligand in DTPA-monoclonal antibody conjugates

“…bifunctional EDTA,1 DTPA, etc. ), these methods include mIn (6,7) and 57Co (8) binding assays, Tb fluorescence titrations (9), and use of uC-labeled ligands (10). In this laboratory, mAb conjugates with UC labeled ligands were prepared for preclinical studies, but these conjugates have been restricted from use in patients because of the 14C label.…”