Facile radiolabeling of antibody-mimetic protein with In-111 via an inverse-electron-demand Diels-Alder reaction

• Published in: Journal of radiopharmaceuticals and molecular probes : JRMP Vol. 5; no. 2; pp. 83 - 88
• Main Authors: Nam, You Ree, Shim, Ha Eun, Lee, Dong-Eun
• Format: Journal Article
• Language: Korean
• Published: 대한방사성의약품학회 01.12.2019
• Subjects: 방사선과학; repebody protein; Radiolabeling; radio-ITLC; invers-electron-demand Diels-Alder reaction; In-111
• ISSN: 2384-1583; 2508-3848

In order to understand the in vivo biodistribution of repebody protein (RB), an efficient and simple radiolabeling method for the protein is needed. We demonstrate a detailed protocol for the radiosynthesis of an 111In radiolabeled tetrazine prosthetic group and its application to the efficient radiolabeling of trans-cyclooctene-group conjugated repebody protein using inverse-electron-demand Diels-Alder reaction. First, 1,2,4,5-tetrazine (Tz) conjugated with a DOTA chelator, was used for preparing the radiolabeled DOTA complex with 111In. Second, the trans-cyclooctene (TCO) functionalized repebody protein was synthesized which allows for the preparation of radiolabeled proteins by copper-free click chemistry. Following incubation with the 111In-radiolabeled DOTA complex (111In-Tz), the TCO-functionalized RB (TCO-RB) was radiolabeled successfully with 111In, with a high radiochemical yield (69.5%) and radiochemical purity (>99%). The radiolabeling of repebody protein by copper-free click chemistry was accomplished within 20 min, with great efficiency in aqueous conditions. These results clearly indicate that the present radiolabeling method will be useful for the efficient and convenient radiolabeling of trans-cyclooctene-group containing biomolecules.