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Updated: Mar 21, 2026

An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group
Published on: October 10, 2016
Highly efficient method for 125I-radiolabeling of biomolecules using inverse-electron-demand Diels-Alder reaction
Mi Hee Choi1, Ha Eun Shim1, Seong-Jae Yun1
1Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup, Jeonbuk 56212, Republic of Korea.
Abstract:
In this report, we present a rapid and highly efficient method for radioactive iodine labeling of trans-cyclooctene group conjugated biomolecules using inverse-electron-demand Diels-Alder reaction. Radioiodination reaction of the tetrazine structure was carried out using the stannylated precursor 2 to give 125I-labeled product ([125I]1) with high radiochemical yield (65±8%) and radiochemical purity (>99%). For radiolabeling application of [125I]1, trans-cyclooctene derived cRGD peptide and human serum albumin were prepared. These substrates were reacted with [125I]1 under mild condition to provide the radiolabeled products [125I]6 and [125I]8, respectively, with excellent radiochemical yields. The biodistribution study of [125I]8 in normal ICR mice showed significantly lower thyroid uptake values than that of 125I-labeled human serum albumin prepared by a traditional radiolabeling method. Therefore [125I]8 will be a useful radiolabeled tracer in various molecular imaging and biological studies. Those results clearly demonstrate that [125I]1 will be used as a valuable prosthetic group for radiolabeling of biomolecules.
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