[11 C]Carboxylated Tetrazines for Facile Labeling of Trans-Cyclooctene-Functionalized PeptoBrushes.

Functionalization of macromolecules (antibodies, polymers, nanoparticles) with click-reactive groups greatly enhances the versatility of their potential applications. Click chemistry based on tetrazine - trans-cyclooctene (TCO) ligation is especially promising and is already widely applied for pretargeted imaging and therapy. Indirect radiolabeling of TCO-functionalized macromolecules with sub-stoichiometric amounts of radioactive tetrazines is a convenient way to monitor the fate of those macromolecules by means of positron emission tomography (PET) imaging after their administration into the test subject. In this work, we report on the preparation of TCO-containing graft copolymers, namely PeptoBrushes (polyglutamic acid-graft-polysarcosine), novel [11C]carboxylated tetrazines and their combined use in radiolabeling the polymer by inverse electron demand Diels Alder reaction, to investigate it's potential for an application in pretarget imaging or injectable brachytherapy. The procedure for [11C]tetrazine production is easy and scalable, while indirect TCO-PeptoBrushes labeling with these [11C]tetrazines is mild, fast and quantitative. Our strategy allows facile 11C-labeling of diverse TCO-functionalized macromolecules, so that their localization and distribution shortly after injection can be assessed by PET. This article is protected by copyright. All rights reserved.