A colorimetric and ratiometric fluorescent probe with enhanced near-infrared fluorescence for selective detection of cysteine and its application in living cells

Abstract

Ratiometric near-infrared (NIR) fluorescent probes are attractive tools for bioimaging applications. Although many fluorescent probes have been developed for detection of the biologically important cysteine (Cys), ratiometric NIR fluorescent probes for Cys are very rare, particularly those with significant fluorescence enhancement in the NIR region. In this work, a new ratiometric NIR fluorescent probe with significant NIR fluorescent turn-on changes was reported for rapid, colorimetric and ratiometric fluorescent detection of Cys. This probe is able to detect Cys in aqueous solution under mild conditions, with high selectivity and sensitivity for Cys over various analytes including the similar structured homocysteine (Hcy) and glutathione (GSH). The detection limit of this probe for Cys was found to be as low as 0.2 μM, which is far below the normal content of Cys (30–200 μM) in cells. Besides the excellent sensing properties, this probe shows low cytotoxicity and can be conveniently applied to image intracellular Cys in living cells, indicating it is a promising tool for biological applications.