Design of a Coumarin-Based Fluorescent Probe for Efficient In Vivo Imaging of Amyloid-β Plaques

Amyloid-β (Aβ) is the core constituent protein of senile plaques, which is one of the key pathological hallmarks of Alzheimer's disease (AD). Here we describe the design, synthesis, and evaluation of coumarin-derived small molecule fluorophores for Aβ imaging. By embedding the aromatic coumarin framework into π bridge of a push–pull chromophore, a novel fluorescence probe XCYC-3 applicable to efficient Aβ recognition was discovered. XCYC-3 displays higher fluorescent enhancement for aggregated Aβ than monomeric Aβ, and possesses good blood-brain barrier permeability. In vitro staining and in vivo imaging studies demonstrated that XCYC-3 could efficiently recognize Aβ plaques in the brain of AD transgenic mice. These results suggest that XCYC-3 is a promising fluorescence imaging agent for Aβ, which might provide important clues for the future development of potent NIR fluorescent probes for Aβ diagnosis.