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[Display omitted] • An easily prepared and novel flavone-based fluorescent probe LFA was synthesized for detecting Cys in lysosome. • Experimental results indicated that LFA exhibited rapid response, high sensitivity and selectivity toward Cys. • Living cell imaging of LFA toward Cys was successfully performed for lysosomal imaging in CHL cells with low cytotoxicity. Cysteine (Cys) is one of the most important biothiols that plays a crucial role in many physiological and pathological processes, and therefore it is of great importance to detect and analyze Cys in subcellular environments, such as in lysosomes. However, only a few fluorescent probes were reported to be capable of detecting Cys in lysosomes selectively. In this wok, we designed and developed a simple, accessible flavone-based fluorescent probe LFA for detecting Cys in lysosomes. Morpholine was employed as the targeting unit for lysosome, and acrylate group was chosen as the Cys-response unit. The probe was easily prepared by a two-step procedure and displayed large Stokes shift, high sensitivity, turn-on response toward Cys over homocysteine (Hcy), glutathione (GSH), and other amino acids. With low cytotoxicity and good cell permeability, the probe could be successfully applied for fluorescence imaging of Cys in living cells. Furthermore, colocalization experiment revealed that lysosomal-targetable ability of LFA was significant. These results indicated that such simple fluorescent probe could provide a promising tool for detection of lysosomal Cys in living biological systems. [ABSTRACT FROM AUTHOR]

As an important sulfur-containing amino acid, aberrant levels of cysteine are closely related with an array of dieases. Although many Cys-specific fluorescent probes have been designed, most of them wouldn't be able to detect Cys in buffer solution, which limits the application of the probe in biological system. In this work, a novel near-infrared fluorescent probe Cys-WR with a large Stokes shift (about 110 nm) was developed for the detection of Cys by conjugating the fluorophore WR-4 with crotonate moiety. The probe exhibited off-on response to Cys with wide linear range of 0–100 μM, as well as the color of the probe solution changes from deep pink to brown observed by naked eyes. Moreover, the probe showed little cytotoxicity. Imaging of Cys using this probe in living A549 cells and zebrafish had also been well demonstrated. Image 1 • A novel near-infrared fluorescent probe Cys-WR with a large Stokes shift was constructed for detection of Cys. • The probe Cys-WR showed NIR off-on response to Cys with high sensitivity and selectivity. • The probe Cys-WR can be employed to monitor exogenous and endogenous Cys fluctuation in living cells and zebrafish. [ABSTRACT FROM AUTHOR]