ALTERNATIVE METHOD OF LABELING ANTIBODIES WITH TC-99M

This study presents an alternative method of labelling antibodies and other polypeptides useful in nuclear medicine with technetium-99m. Dex tran T10 was mildly oxidized with sodium periodate. The dextran deriva tive then reacted with a monoclonal anticytokeratin antibody. After co njugation, the bonds were stabilised with sodium cyanoborohydride. The dextranated antibody was purified by HPLC, analyzed for dextran conte nt and tested for immunoreactivity. The conjugate was labelled with Tc -99m in the presence of tin chloride and the labelling efficiency was accessed by thin layer chromatography. With this method, approximately 1.5 molecules of dextran could be conjugated per mab with preserved i mmunoreactivity. The conjugate was successfully labelled with Tc-99m, 42-47 MBq was incorporated into 35 mu g of conjugate. The labelling ef ficiency was 84-94%. This mild method of dextran conjugation and the s ubsequent Tc-99m labelling, utilizing the strong tendency of reduced t echnetium-99m to complex with dextran, can be of general interest for Tc-99m labelling in radioimmunoscintigraphy.