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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]

A smart fluorescent probe DPAS-Cys has been rationally designed based on a typical AIEgen DPAS and an acrylate moiety. The probe DPAS-Cys not only can be used for the detection of cysteine (Cys) selectively with large Stokes shift (200 nm) and relatively low detection limit (2.4 μM), but also shows lipid droplets (LDs) targeting property. The response mechanism for Cys was carefully verified. Importantly, due to the aggregation-induced emission characteristic, the introduction of considerable percentage of traditional organic solvent is avoidable, which makes it suitable for bioimaging in physiological systems. In addition, the confocal fluorescence imaging demonstrates that DPAS-Cys is able to detect Cys in LDs of different cell lines with universality. Our study opens a new avenue to understand the importance of LDs in biosystem, for which the gap between the essential biothiol Cys and the energy storage organelle LDs was bridged for the first time. Image 1 • A smart fluorescent probe DPAS-Cys is developed for selective detection of cysteine. • DPAS-Cys shows aggregation-induced emission characteristic and large Stokes shift. • DPAS-Cys exhibits lipid droplets targeting property with universality. [ABSTRACT FROM AUTHOR]

Abstract Cysteine (Cys) plays a vital role in many physiological processes, and also is closely related to various diseases, thus the development of novel high selectivity and sensitivity fluorescent probes for in situ monitoring of biothiol (Cys) is crucial. Herein, we present a fluorogenic method to detect Cys in vitro and live cells based on fluorescent protein chromophores, which have been modulated by chemical reaction. Probe (RFP) is a fluorescence turn on probe with red emission wavelength and large Stokes shift (127 nm). This Michael-addition reaction-based probe exhibits low detection limit (18.7 μM), fast response time, and low cytotoxicity. RFP can differentiate the Cys and Hcy, using the difference of reaction time between probe and Cys or Hcy. Together, this probe exhibited excellent cell permeability, and can be successfully applied to detect the endogenous Cys in living cells. Highlights • Provide a fluorogenic method to detect Cys based on fluorescent protein chromophores. • Realize the red emission and large Stokes shift using chemical modulation method. • Differentiate the Cys and Hcy using the difference of reaction time. • Detection endogenous or exogenous Cys in living cells and served as bioimaging reagent. [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 hydroxyphenylquinazolinone-based fluorescent probe DAP-1 with a large Stokes shift (162 nm) was firstly developed for detection of cysteine. The probe DAP-1 with two acrylate as highly Cys-selective sites was designed based on the combination of excited state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) mechanism. Upon the treatment with cysteine, DAP-1 displayed a strong fluorescence enhancement (65-fold). The limit of detection obtained from fluorescent titration was as low as 0.03 μM. DAP-1 could detect cysteine with high selectivity and sensitivity. Significantly, DAP-1 could be used to detect cysteine in living cells. [ABSTRACT FROM AUTHOR]

A novel 4′-hydroxybiphenyl-4-carbonitrile-based fluorescent probe, 1 , for selective detection of cystein (Cys) over homocystein (Hcy) and glutathione (GSH) was developed. This probe had simple structure and could be easily synthesized with good yield from commercially available materials. Moreover, probe 1 showed a remarkable large Stokes shift (180 nm) and displayed a rapid (5 min) and highly sensitive response (the detection limit was 0.15 μM) for Cys with fluorescence turn-on signal changes (142-fold fluorescence enhancement). Importantly, probe 1 could be used to detect and image both exogenous and endogenous Cys in living A549 cells. [ABSTRACT FROM AUTHOR]

Cysteine is an organic small molecule that plays an important role in human physiological processes. It is meaningful to detect it easily with high selectivity and sensitivity. In this work, a fluorescent probe Lyso-CDC based on chalcone fluorescent dyes for the effective detection of Cys in lysosomes was designed and synthesized. After adding Cys, the fluorescence of the probe Lyso-CDC at 568 nm was significantly enhanced, displaying a large Stokes shift (168 nm) and a color change from light yellow to bright yellow that was visible to naked eyes. The selectivity and sensitivity of the probe Lyso-CDC for Cys were much higher than other amino acids, and the detection limit for Cys was calculated to be 1.44 × 10−8 M. Furthermore, the probe Lyso-CDC possessed low cytotoxicity, excellent biocompatibility and outstanding lysosome targeting ability. The probe was successfully applied to detect Cys in lysosomes of living cells. [Display omitted] • Lyso-CDC was easy to synthesize. • Lyso-CDC specifically recognized Cys with a large Stokes shift of 168 nm. • Lyso-CDC had a low detection limit of 1.44 × 10−8 M for Cys. • Lyso-CDC has been successfully used to detect and image Cys in living cells. • Lyso-CDC was lysosome-targeting. [ABSTRACT FROM AUTHOR]

[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]

We constructed a novel cysteine fluorescent probe with large stokes shift for imaging in the living cells, zebrafish, and living mice. [Display omitted] • The new probe Ty-Cys1 had a very large Stokes shift. • The robust probe Ty-Cys1 showed a good selectivity, sensitivity to Cysteine. • The novel probe Ty-Cys1 was successfully applied to measure Cys in living cells, zebra fishes, and living mice. The small molecule biological thiols, such as Cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play crucial roles in maintaining various cellular vital activities. In the organism, abnormal levels of small-molecule biological thiols have been associated with a variety of diseases. Therefore, quantitative determination of biological thiols, especially Cys, is significant for understanding their functions in various biological processes. Thus, in this work we designed a new fluorescent probe Ty-Cys1 with a large Stokes shift of 207 nm to monitor Cysteine. The maximum absorption wavelength of Ty-Cys1 was 418 nm, and the maximum emission wavelength was 625 nm. Significantly, the novel probe Ty-Cys1 was effectively in detecting of Cys changes in living cells, zebrafishes, and living mice. [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] • Fluorescent probe TNP-SBD-Cl was developed based on naphthimine-sulfonyl benzoxadiazole. • TNP-SBD-Cl can specifically recognize Cys with a large Stokes shift (157 nm). • TNP-SBD-Cl showed good selectivity and sensitivity for the detection of Cys (0.87 μM). • TNP-SBD-Cl has been successfully applied to fluorescence imaging of Cys in living cells. Biothiols play an important role in many physiological and pathological processes, especially in the occurrence of oxidative stress caused by abnormal cysteine (Cys) concentration. Therefore, it is particularly critical to develop a method that can specifically identify Cys to avoid interference from other biological analytes. However, most Cys-specific fluorescent probes are difficult to distinguish between homocysteine (Hcy) and glutathione (GSH). In this work, to avoid the interference of Hcy and GSH, we developed a fluorescent probe triarylimidazole-naphthalimide-piperazine-sulfonyl benzoxadiazole (TNP-SBD-Cl) based on fluorescence resonance energy transfer (FRET) on platform of naphthalimide-sulfonyl benzoxadiazole (SBD), the main SBD 4-chlorine groups have mild reactivity to undergo substitution and rearrangement to distinguish Hcy and GSH. The TNP-SBD-Cl response to Cys would turn on FRET and generate a new yellow fluorescence with a large Stokes shift (157 nm), and with excellent selectivity and low detection limit (0.87 μM). Moreover, TNP-SBD-Cl can be used to monitor Cys in living HeLa cells with low cytotoxicity, suggesting that it has markedly diagnostic significance in physiological and pathological processes. [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]

A new strategy endowing probe with large Stokes shift, high quantum yield and red emission was developed by incorporating tetrahydroquinoxaline unit and five-membered pyrrolidine ring on fluorophore. As demonstrated, a novel probe was rationally designed and synthesized for sensitive monitor of cellular cysteine (Cys) and endogenous aminoacylase with large Stokes shift and high quantum yield. Image 1 • A novel fluorescent probe with large Stokes shift, high quantum yield and red emission was rationally designed and synthesized. • The probe was exhibited fast-response, high sensitivity and high selectivity towards cysteine. • The probe was successfully applied to real-time monitor and visualize endogenous cysteine and intracelluar aminoacylase in living cells. [ABSTRACT FROM AUTHOR]

• A new highly sensitive probe that capable of specifically detecting cysteine was developed. • The fluorescence of PYAC exhibits "off–on" switching property and a large Stokes shift after the addition of Cys. • The detect limitation is down to 0.062 μM. • The probe has negligible toxicity to cells and has been successfully applied to detect Cys in Hela cells. This paper reports a novel fluorescent probe 4-acrylatepyrene (PYAC) based on 4-hydroxypyrene, which can effectively detect cysteine (Cys). The probe PYAC uses acrylate moiety as a recognition site and has relatively high selectivity and sensitivity for Cys with the detection limit of 0.062 μM. After treatment with Cys, PYAC exhibits "off–on" switching property and large Stokes shift (171 nm). Due to nucleophilic addition and specific intramolecular cyclization, it exhibits higher selectivity for Cys than other amino acids and common ions, including homocysteine (Hcy) and glutathione (GSH) with similar structures to Cys. The recognition mechanism has been characterized by high-performance liquid chromatography (HPLC) and nuclear magnetic resonance spectroscopy (1H NMR). Anti-interference test and pH influence test display it is suitable for detecting Cys in living cells. Finally, the probe PYAC has been successfully applied to cell imaging with negligible cytotoxicity. [ABSTRACT FROM AUTHOR]

Cysteine has a great effect on the physiological and pathological processes, which could bring out various diseases such as skin lesions, edema, hair depigmentation, Alzheimer's, Parkinson's, and liver damage due to the abnormal concentrations of cysteine. Therefore, it is of great impoatance to develop a method for imaging Cys. Herein, a novel fluorescent probe was developed for imaging Cys in vivo specially. This turn-on probe exhibited favorable advantages including large Stokes shift (90 nm), fast response (10 min), good selectivity, low cytotoxicity and so on. Furthermore, the probe could be applied to monitoring cysteine in living HeLa cells, which indicates that this turn-on probe could penetrate viable cell membranes and image Cys over other analystes especially HCy and GSH. Unlabelled Image • A novel fluorescent probe NBDS was developed for imaging Cys in vivo specially exhibiting favorable advantages including large Stokes shift (90 nm), fast response (10 min), good selectivity, low cytotoxicity. • This turn-on probe exhibited favorable advantages including large Stokes shift (90 nm), fast response (10 min), good selectivity, low cytotoxicity. • In vivo cell imaging indicates that the probe NBDS could be suitable to reveal the vital role of Cys in various physiological processes. [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]