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RESEARCH PRODUCT

Modular Assembly of Multimodal Imaging Agents through an Inverse Electron Demand Diels–Alder Reaction

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International audience; The combination of two imaging probes on a same biomolecule gives access to targeted bimodal imaging agents that can provide more accurate diagnosis, complementary information, or that may be used in different applications, such as PET imaging and fluorescence imagingassisted surgery. In this study, we demonstrate that dichlorotetrazine, a small, commercially available compound, can be used as a modular platform to easily assemble various imaging probes. Doubly-labeled tetrazines can then be conjugated to a protein through a biorthogonal IEDDA reaction. A series of difunctionalized tetrazine compounds containing various chelating agents and fluorescent dyes was synthesized. As a proof of concept, one of these bimodal probes was conjugated to trastuzumab, previously modified with a constrained alkyne group, and the resulting dual-labeled antibody was evaluated in a mice model, bearing a HER2-positive tumor. A significant uptake into tumor tissues was observed by both SPECT-CT and fluorescence imaging, and confirmed ex-vivo in biodistribution studies.