Technetium-99m labeling on monoclonal antibodies via N,N'-ethylene-bis-L-cysteine

A new developed excellent kidney imaging agent, N,N'-ethylene-bis-L-cysteine (EC) has been used as a bifunctional chelating agent (BFCA) for Tc-99m labeling of monoclonal antibodies (MoAb). A new conjugation agent N-hydroxyl-1,4-epoxyl-cyclohex-5-ene-2,3-di-carboxyl-imide (HONCE) and a water-soluble dehydrating agent 1-ethyl-3-(3-dimethylaminopropyl)-carbo-diimide (EDC) were used to accomplish the conjugation of EC with antibodies. A conjugation yield of 30-40% was obtained. The experimental conditions were optimized for the best conjugation performance. Tc-99m labeling was then completed after conjugation. More than 80% of the immunoreactivity was retained after monoclonal antibodies conjugated with EC. More than 70% of the radioactivity was retained in the labeled complex Tc-99m-EC-Ab after incubation in fresh EC and cysteine solutions for 16-20 h. The biodistributions of labeled antibody in mice were also determined. (orig.)