A Simple and Effective Approach to Preparation of Radioimmunoconjugate with DTPA derivative

Radioimmunotherapy (RIT), which uses a monoclonal antibody labeled with a radionuclide to deliver radiation to target sites of disease, has been extensively studied in this population. It is important that the radionuclide be stably coupled to the antibody when administered in vivo and not interfere with immune activity of the antibody (Ab). Labeling the Ab directly with a radionuclide is inadequate because of the possibility that the radionuclide could attach to an immune determinant region and interfere with its activity or specificity. As an alternative to direct labeling, bifunctional chelating agent (BFCA) with a strong chelating group capable of covalently bonding the Ab and the labeling radionuclide is introduced. Any suitable chelator combined with a variety of reactive groups may be used, but the most popular are diethylene triamine penta acetic acid (DTPA) and ethylenediamine tetra acetic acid (EDTA). Often the formation of conjugates between Ab and DTPA resulted to a less stable agent due to differential position in antibody and leads to radiolabeling inefficiency. The main goal of this study was to optimize the most important step in immunoconjugation using a BFCA for the preparation of radioimmunoconjugate. We introduced a derivative of DTPA, DTPA-NCS, to conjugate Ab. Characterization of immunoconjugation was carried out