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[Display omitted] • An "off–on" long-wavelength fluorescent probe is synthesized for Cys detection. • The probe has a large Stokes shift (211 nm) and reacted with Cys specifically. • The probe can monitor Cys fluctuations caused by redox imbalance in HepG2 cells. • The probe can be used for fluorescence imaging in cells and mice. In this research, an "off–on" long-wavelength fluorescent probe (DCMN-Cl) based on (E)-2-(3-(2-(6-hydroxynaphthalen-2-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile (DCMN) is designed and synthesized for cysteine (Cys) detection. DCMN-Cl exhibits a large Stokes shift (211 nm) and shows rapid response and high specificity to Cys. The fluorescence initensity at 635 nm reveals a good linear relationship with Cys concentration in the 0 to 50 μM range, and the detection limit is as low as 159 nM. The probe is also used for fluorescence imaging of Cys in cells and mice. Moreover, the probe provided visual evidence of Cu2+ and curcumin-induced intracellular Cys fluctuations. [ABSTRACT FROM AUTHOR]

The abnormality of Cys concentration in organism could lead to a series of diseases, so its effective detection is of great importance in disease diagnosis. Here we developed a novel ESIPT fluorescent probe HBT-IDAc based on the classic ESIPT fluorophore 2-(2′-hydroxyphenyl)benzothiazole (HBT) and indanone, which could selectively and sensitively detect Cys with a large Stokes shift up to 210 nm and the detection limit to 0.89 μM. In addition, the probe exhibited good anti-interference and low cytotoxicity, and has been successfully applied to monitor Cys in cells. • A novel ESIPT fluorescent probe for selective and sensitive detection of Cys was developed. • The probe has the large stokes shift (210 nm) and good LOD (0.89 μM) in aqueous environment. • The probe exhibits low cytotoxicity and has been applied for imaging Cys in cells. [ABSTRACT FROM AUTHOR]

Abstract In this work, we have designed and synthesized a dinitrobenzene-sulfonate tetrahydro[5]helicene (H-DNP) as an effective fluorescent probe for detection of hydrogen sulfide (H 2 S). Upon the addition of H 2 S, a significant fluorescence enhancement (75-fold) at 495 nm can be observed with a distinct color change from colorless to yellow. Additionally, H-DNP shows low background spectroscopic signal, large Stokes Shift up to ~140 nm, good sensitivity, rapid response time less than 2 min, low detection limit (48 nM) and high selectivity toward common bio-thiols (Cysteine, Homocysteine and Glutathione). Compared with the previous dinitrophenoxy tetrahydro[5]helicene, this probe has shorter response time and lower detection limit. Most importantly, this probe H-DNP has low toxicity to cells and excellent cell permeability, which can be applied to visualize H 2 S in living cells. Graphical abstract Unlabelled Image Highlights • A tetrahydro[5]helicene based fluorescence probe displayed a rapid, sensitive and selective in response to H 2 S. • The probe has very low detection limit and fast response time. • The response mechanism is confirmed to be thiolysis reaction induced by H 2 S. • The detection of intracellular H 2 S was successfully demonstrated in living cells. [ABSTRACT FROM AUTHOR]

Abstract A new imidazo [1,5- a ]pyridine-based fluorescent probe, named MZC-AC, is developed for the detection of cysteine (Cys) based on an excited state intramolecular proton transfer (ESIPT) mechanism. The probe MZC-AC uses an acrylate moiety as the ESIPT blocking group as well as the recognition site. Upon the treatment with Cys, MZC-AC exhibits a dramatic fluorescence enhancement (85-fold) and a large Stokes shift (166 nm). The limit of detection obtained from fluorescent titration was as low as 0.07 μM. MZC-AC displays highly sensitive and selective response to Cys over homocysteine (Hcy) and glutathione (GSH). Significantly, MZC-AC could be used to detect Cys in living cells. Graphical abstract Image 1 Highlights • An imidazo [1,5- a ]pyridine-based fluorescent probe MZC-AC was developed. • MZC-AC can detect cysteine with high sensitivity and selectivity. • MZC-AC shows a large Stokes shift. • The limit of detection was as low as 0.07 μM. • MZC-AC can be applied in imaging intracellular cysteine in living cells. [ABSTRACT FROM AUTHOR]

A series of fluorescent dyes based on 2-(2′-hydroxyphenyl)benzothiazole derivatives were designed and synthesized. Because of their structural characteristics of "AIE + ESIPT", they have long-wavelength emission and a larger Stokes shift. The fluorescent probe HBTN-Y was prepared based on the fluorescent dye HBTN. Probe HBTN-Y can recognize cysteine (Cys) with a high selectivity, "OFF-ON" fluorescence response, a large Stokes shift (263 nm) and long-wavelength emission (637 nm) in MeCN/H 2 O (1:1, v/v, PBS 20 mM, pH = 8.4) solution. The probe exhibits good anti-interference ability, a low detection limit of 6.51 × 10−6 M, and is suitable for application at near neutral and weak alkaline pH (7–9) conditions. Moreover, HBTN-Y is applicable to image Cys in living MCF-7 cells. A new fluorescence "AIE + ESIPT" characteristics probe HBTN-Y for the detection of cysteine has been developed. [Display omitted] • A series of fluorescent dyes with "AIE + ESIPT" features were synthesized. • A cascade reaction-based fluorescence "turn on" probe (HBTN-Y) has been developed. • HBTN-Y displays highly selective recognition for Cys in an aqueous solution. • HBTN-Y can detect Cys with a long wavelength emission and a large Stokes shift. • HBTN-Y is capable of imaging Cys in living MCF-7 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel coumarin-based fluorescent probe with large Stokes shift (216 nm) is designed and synthesized. • The probe exhibits fast-response (<4s), high sensitivity and low detection limit (8.82 × 10−8 M) towards Cys. • The probe is successfully applied in living cells. A new fluorescence probe L , which featured with a large Stokes shift (216 nm), was designed for sensitive detection of cysteine (Cys) and a potential sensing mechanism derived from excited state intramolecular proton transfer (ESIPT) was proposed. More importantly, probe L exhibits higher selective to Cys than other amino acid due to its specific cyclization between acrylate group and Cys. Meanwhile, the probe L shows a low detection limit of 8.82 × 10−8 M, which is enough for detecting Cys in organisms. Furthermore, this probe displays high biocompatibility and can image Cys in living cells. [ABSTRACT FROM AUTHOR]