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• A deep-red emission fluorescent probe (DRP-Cys) for Cys based on a hemicyanine scaffold was developed. • A tailed malononitrile group could chromatically shift excitation/emission wavelengths to the deep-red emission range. • The probe could detect Cys with an ultrafast response time of about 1 min and a low limit of detection of 10 nM • The probe was also successfully applied for visualizing endogenous Cys in living HeLa cells and mice. It is still challenging how to selectively and sensitively detect cysteine in living systems which plays crucial roles in many physiological and biological processes. Here, we developed a deep-red emission fluorescent probe (DRP-Cys) for Cys based on a hemicyanine scaffold. A tailed malononitrile group could chromatically shift excitation/emission wavelengths to avoid the limitations such as photo-damage or auto-fluorescence in biological samples. Compared with other amino acids, Cys could trigger the Michael addition reaction to release a dramatic enhancement in fluorescence centering at around 645 nm in DMSO aqueous solution under physiological conditions with an ultrafast response time of about 1 min and a low limit of detection of 10 nM which significantly benefited from the introduction of the malononitrile moiety. The probe was also successfully applied for visualizing endogenous Cys in living HeLa cells and mice with low cytotoxicity and good cell-membrane permeability. [ABSTRACT FROM AUTHOR]

Abstract As the second most abundant transition metal after iron in biological systems, Zn2+ takes part in various fundamental life processes such as cellular metabolism and apoptosis, neurotransmission. Thus, the development of analytical methods for fast detection of Zn2+ in biology and medicine has been attracting much attention but still remains a huge challenge. In this report, we develop a novel Zn2+-specific light-up fluorescent probe based on intramolecular charge transfer combined with chelation enhanced fluorescence induced by structural transformation. Addition of Zn2+ in vitro can induce a remarkable color change from colorless to green and a strong fluorescence enhancement with a red shift of 43 nm. Moreover, the probe shows an extremely low detection limit of 13 nM and ultra-fast response time of less than 1 s. The Zn2+ sensing mechanism was fully supported by TDDFT calculations as well as HRMS and 1H NMR titrations. The recognition of Zn2+ in living Hela cells as well as the MTT assay demonstrate that the probe can rapidly light-up detect Zn2+ in vivo with low cytotoxicity and good cell-permeability. Furthermore, the probe can also be successfully applied to bioimaging Zn2+ in living zebrafish. Graphical Abstract Unlabelled Image Highlights • A novel Zn2+-specific light-up fluorescent probe is prepared on the modulation of ICT and CHEF. • The probe shows an extremely low detection limit of 13 nM and ultra-fast response time of less than 1 s. • The probe can be successfully applied to bioimaging Zn2+ in living HeLa cells and zebrafish. [ABSTRACT FROM AUTHOR]

Zn2+ plays fundamental roles in cellular metabolism and apoptosis, as well as neurotransmission. However, how to fast detect Zn2+ in biology is still challenging and meaningful. In this study, we rationally synthesized a simple OFF–ON fluorescent probe for fast detection of Zn2+ based on intramolecular charge transfer and chelation-enhanced fluorescence. Addition of Zn2+ into the probe induced a significant fluorescence enhancement with a bathochromic shift of 55 nm. Moreover, the probe demonstrated excellent sensitivity (detection limit = 0.072 μM) and outstanding selectivity toward Zn2+ and an ultra-fast response rate of two seconds. The recognition mechanism of the probe toward Zn2+ was fully confirmed by HRMS and 1H NMR spectra, as well as TDDFT calculations. Furthermore, the probe could rapidly visualize Zn2+ in living cells and zebrafish models in bioimaging experiments with low cytotoxicity and good biocompatibility. [ABSTRACT FROM AUTHOR]

As a second messenger, hydrogen peroxide plays significant roles in numerous physiological and pathological processes and is related to various diseases including inflammatory disease, diabetes, neurodegenerative disorders, cardiovascular disease and Alzheimer's disease. Two-photon (TP) fluorescent probes reported for the detection of endogenous H 2 O 2 are rare and most have drawbacks such as slow response and low sensitivity. In this report, we demonstrate a simple H 2 O 2 -specific TP fluorescent probe ( TX-HP ) containing a two-photon dye 6-hydroxy-2,3,4,4a-tetrahydro-1H-xanthen-1-one ( TX ) on the modulation of the ICT process. The probe exhibits a rapid fluorescent response to H 2 O 2 in 9 min with both high sensitivity and selectivity. The probe can detect exogenous H 2 O 2 in living cells. Furthermore, the probe is successfully utilized for imaging H 2 O 2 in liver tissues. [ABSTRACT FROM AUTHOR]

• A simple dual-emission fluorescent biothiol probe was designed and synthesized. • The probe could discriminate cysteine from homocysteine and glutathione in both blue and green channels. • The probe could be successfully applied for visualizing biothiols in living HeLa cells and zebrafish. Cellular biothiols function crucially and differently in physiological and pathological processes. However, it is still challenging to detect and discriminate thiols within a single one molecule, especially for cysteine (Cys) and homocysteine (Hcy). In this study, a simple two-emission turn-on fluorescent biothiol probe (ICN-NBD) was rationally designed and synthesized through a facile ether bond linking 7-nitro-1,2,3-benzoxadiazole (NBD) and phenanthroimidazole containing a cyano tail. The probe in the presence of Cys elicited two fluorescence responses at 470 nm and 550 nm under excitation at 365 nm and 480 nm, respectively, because of the concomitant generation of both the fluorophore and NBD- N -Cys. In contrast, addition of Hcy and glutathione (GSH) could result in only a blue fluorescence enhancement at 470 nm. which was reasonably attributed to rearrangement from NBD- S -Hcy/GSH to NBD- N -Hcy/GSH as a result of geometrical constraints or solvent effects. Therefore, the fluorescent probe with the NBD scaffold could detect biothiols and simultaneously discriminate Cys from Hcy/GSH in both blue and green channels. The probe has been successfully applied for visualizing biothiols in living cells and zebrafish. [ABSTRACT FROM AUTHOR]

Hydrazine is an important reactive base in chemistry, pharmacy and agriculture and an effective propellant in aeronautics and astronautics. However, tiny leakage might induce serious environmental contamination and fatal biological damage. Thus, how to rapidly detect hydrazine with high selectivity and sensitivity is of significance and challenge. In this report, we demonstrate a hydrazine-specific fluorescent probe on the modulation of intramolecular charge transfer process. This probe contains a 4-bromobutyl group as a recognition site for hydrazine anchored on the fluorescent dye. Leaving of 4-bromotutylate moiety leads to a marked NIR fluorescent emission at 715 nm induced by hydrazine. Additionally, presence of hydrazine leads to a color change from green to blue-purple and a ratiometric UV–vis absorption change with a clear isosbestic point at 635 nm. The good linear relationship between fluorescence intensity and concentration of hydrazine results in a low detection limit of 5.09 ppb. The color and fluorescence two-output signals are preferable for qualitative and quantitative detection of hydrazine with high sensitivity and specificity. More importantly, the probe is also successfully applied to visualize hydrazine in living both cells and mice. [ABSTRACT FROM AUTHOR]

Hydrazine is carcinogenic and highly toxic so that it can lead to serious environmental contamination and serious health risks although it has been extensively used as an effective propellant and an important reactive base in industry. Thus, the development of two-emission NIR fluorescent probes for rapid detection of hydrazine with high selectivity and sensitivity is of significance and of great challenge in both biological and environmental sciences. Here, we report a two-emission colorimetric fluorescent probe for the specific detection of hydrazine based on hydrazinolysis reaction under physiological conditions. In the presence of hydrazine, the probe showed an extremely remarkable fluorescence enhancement at 627 nm compared to the decrease at 814 nm excited at different wavelength in aqueous solution. This distinct difference of two emission intensities is suitable for detection of low concentration hydrazine with a detection limit of 0.38 ppb. Addition of hydrazine resulted in a remarkable color change from blue-green to red observed by the naked eye. Kinetic study indicated a fast response of the probe toward hydrazine in minutes. Furthermore, the probe can bioimage hydrazine in living HeLa cells and mice with low cytotoxicity and excellent biocompatibility. [ABSTRACT FROM AUTHOR]