Radiolabeling of Antibodies for Aβ and TfR Binding

The antibodies, mAb3D6 and mAb3D6-scFv8D3, were labeled with iodine-125 (¹²⁵I) by direct iodination with chloramine T [36 (link)]. Briefly, antibody (mAb3D6 or mAb3D6-scFv8D3), ¹²⁵I stock solution (Perkin Elmer, USA) and chloramine T (5 µg) were mixed in PBS to a final volume of 110 μL, and then incubated 90 s in room temperature. The labeling reaction was quenched with 10 μg sodium metabisulfite. Radioiodinated antibody was purified with Zeba Spin Desalting Columns (7 K MWCO, 0.5 mL, Thermo Fisher Scientific, Waltham, MA, USA). Binding of [¹²⁵I]I-mAb3D6 and [¹²⁵I]I-mAb3D6-scFv8D3 to Aβ and TfR was tested with ELISA directly after radiolabeling according to a previously described method [16 (link)].