Fluoride-specific fluorescence/MRI bimodal probe based on a gadolinium(III)-flavone complex: synthesis, mechanism and bioimaging application in vivo

Molecular imaging is a powerful tool to visualize cellular processes and activity levels of biomarkers at the cellular and molecular level, in which a molecular probe is a prerequisite for the molecular imaging technique. The present work reports a bimodal probe for the fluorescence and magnetic resonance detection of fluoride ions (F-) in aqueous media and in vivo. The bimodal probe, EDTA-Gd-HF, was prepared by self-assembly of the EDTA-Gd complex with 3-hydroxyflavone (HF). In the system, HF plays the role of spectroscopic reporter and Gd(III) serves as a MRI signal output unit as well as the fluoride ion binding site. Upon addition of fluoride ions into an aqueous solution of EDTA-Gd-HF, the replacement of one coordinated water molecule and then liberation of HF led to remarkable spectroscopic recovery and distinct changes to the longitudinal relaxivity (r1), by which fluorescence/MRI bimodal fluoride ion sensing was achieved. In vivo magnetic resonance imaging (MRI) in mice indicates that EDTA-Gd-HF can be potentially used in biomedical diagnosis and therapy fields.