Single Fluorinated Agent for Multiplexed 19F‐MRI with Micromolar Detectability Based on Dynamic Exchange

The weak thermal polarization of nuclear spins limits the sensitivity of MRI, even for MR‐sensitive nuclei as fluorine‐19. Therefore, despite being the source of inspiration for the development of background‐free MRI for various applications, including for multiplexed imaging, the inability to map very low concentrations of targets using 19F‐MRI raises the need to further enhance this platform's capabilities. Here, we employ the principles of CEST‐MRI in 19F‐MRI to obtain a 900‐fold signal amplification of a biocompatible fluorinated agent, which can be presented in a “multicolor” fashion. Capitalizing on the dynamic interactions in host–guest supramolecular assemblies in an approach termed GEST, we demonstrate that an inhalable fluorinated anesthetic can be used as a single 19F‐probe for the concurrent detection of micromolar levels of two targets, with potential in vivo translatability. Further extending GEST with new designs could expand the applicability of 19F‐MRI to the mapping of targets that have so‐far remained non‐detectable. Relying on principles of supramolecular chemistry, this manuscript describes the design, characterization, and implementation of a method for the generation of artificial (non‐luminescent) colors for MRI applications. The proposed approach, which is termed GEST, exploits the reversible binding of inhalable biocompatible fluorinated agent to macrocycle hosts for micromolar detectability of host–guest complexes using background‐free 19F‐MRI.