Radioiodination of protein using 2,3,5,6-tetrafluorophenyl 3-(nido-carboranyl) propionate (TCP) as a potential bi-functional linker: Synthesis and biodistribution in mice

2,3.5.6-Tetrafluorophenyl 3-(nido-carboranyl) propionate (TCP), as a new potential bi-functional linker for radiohalogenation of proteins or peptides, was synthesized. With this bi-functional linker, the first attempt to conjugate bovine serum albumin (BSA) with I-125 was made and the biodistribution of the conjugated BSA (I-125-TCP-BSA) was investigated in NIH strain mice. By the use of TCP as the linker, BSA was conjugated with I-125 in a labeling yield of 58-75% and with radiochemical purity of 99.8% after purification by Sephadex (TM) G-50. Even after being kept at room temperature for 72 h, the radiochemical purity of I-125-TCP-BSA was still more than 98%, much higher than that of the directly I-125-labeled BSA (I-125-BSA). Meanwhile, biodistribution experiments in mice indicated that the uptake of I-125 with I-125- TCP-BSA into thyroid was obviously less than that with I-125-BSA post-injection. All the results implied that the I-125-conjugated BSA (I-125-TCP-BSA) was considerably stable in vivo as well as in vitro, and TCP was regarded as a promising bi-functional linker for radiohalogenation of proteins. (C) 2008 Elsevier Ltd. All rights reserved.