A Near-infrared Fluorescent Probe for Sensing Cuprous ions

The redox character of copper with interconversion between Cu(I) and Cu(II) is essential for many physiological processes. Either deficiency or excess of copper may lead to disease conditions. In this work, a novel fluorescent probe (NS-5) for selective recognition of Cu(I) was reported based on the coordination chemistry between Cu(I) and the thioether tetradentate ligand scaffold. The probe features multiple favorable properties, such as near-infrared (NIR) emission (λ_em = 720 nm), working in aqueous media, significant fluorescence increase (>13-fold) and preferable mitochondrial localization. The successful imaging of Cu(I) in live cells and mouse demonstrates the practical applications of the probe.