Radiolabeling

Antibodies were radiolabeled with [¹²⁵I]Na using Iodogen® according to the manufacturer’s instructions. For ¹¹¹In labeling, IgG was rendered metal-free with DTPA treatment then reacted with an excess of DOTA-SCN at pH 8.5 in metal-free bicarbonate buffer for 1 hour at ambient temperature followed by purification into metal-free 50 mM ammonium acetate, 150 mM NaCl, pH 4.5 using a 10-DG desalting column (Bio-Rad) previously rendered metal-free by treatment with DTPA. The resultant metal-free mAb-DOTA conjugate was labeled with ¹¹¹InCl₃ at 37°C for 1 hour at pH 4.5 and purified into PBS using 10-DG desalting columns.

Typical labeling using this approach resulted in >99% radiochemical purity by instant thin layer chromatography in 10 mM EDTA mobile phase on silica.