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Herein we have reported a fluorescent probe (MB-M) based on MB derivative for Cu2+ ions detection. The probe was well characterized by 1H NMR, 13C NMR and HR-MS spectrum. Probe MB-M showed naked-eyes recognition to Cu2+ as color change from colorless to indigo. The probe exhibited promising features such as high fluorescence and UV–vis selectivity, fast response (5 mint), workable at pH 2–7, and low limit of detection (LOD = 0.33 µM). Probe MB-M was also used for Cu2+ ions imaging in HepG-2 cells and detection in daily life (Test Strip and lake water). Moreover, non-covalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analysis were used to study the interaction between MB-M and Cu2+ ions. By examining the electronic characteristics of the complex using natural bond orbital (NBO), electron density difference (EDD), and frontier molecular orbital (FMO) analysis, the sensitivity of MB-M towards Cu2+ ions were investigated. The results illustrated that the interactions between MB-M and Cu2+ ions involved chemisorption. [ABSTRACT FROM AUTHOR]

Determining the activity of lysosomal β-hexosaminidase in cells is of great importance for understanding the roles that these enzymes play in pathophysiological events. Herein, we designed the new fluorescent probe, βGalNAc-Rhod-CM(NEt 2), which consisted of a βGalNAc-linked rhodol unit serving as a β-hexosaminidase reactive fluorogenic moiety and a N,N′ -diethylaminocoumarin (CM(NEt 2)) group acting as a fluorescence marker for determining the degree of cell permeabilization. Treatment of βGalNAc-Rhod-CM(NEt 2) with β-hexosaminidase promoted generation of Rhod-CM(NEt 2), thereby leading to an increase in the intensity of fluorescence of Rhod. However, this probe did not respond to the functionally related glycosidase, O-GlcNAcase. The detection limit of βGalNAc-Rhod-CM(NEt 2) for β-hexosaminidase was determined to be 0.52 nM, indicating that it has high sensitivity for this enzyme. Furthermore, the probe functioned as an excellent fluorogenic substrate for β-hexosaminidase with k cat and K m values of 17 sec−1 and 22 μM, respectively. The results of cell studies using βGalNAc-Rhod-CM(NEt 2) showed that levels of β-hexosaminidase activity in cells can be determined by measuring the intensity of fluorescence arising from Rhod and that the intensity of fluorescence of CM(NEt 2) can be employed to determine the degree of cell permeabilization of the probe. Utilizing the new probe, we assessed β-hexosaminidase activities in several types of cells and evaluated the effect of glucose concentrations in culture media on the activity of this enzyme. [Display omitted] • Development of the sensitive and selective fluorescent probe for β-hexosaminidase. • Determination of levels of β-hexosaminidase activities in several types of cells. • Evaluation of effect of glucose concentrations in media on β-hexosaminidase activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Al3+ Schiff base probe JHK was designed and synthesized. • JHK has high selectivity, high fluorescence quantum yield and low detection limit for Al3+. • JHK was successfully applied to living cells and zebrafish. A novel fluorescent probe N'-(2-hydroxybenzylidene)-indole-3-formylhydrazine (JHK) was designed and synthesized based on the condensation reaction of indole-3-formylhydrazine and salicylaldehyde. The probe JHK solution could highly selectively recognize Al3+ by the obvious fluorescence enhancement (288-fold) after adding Al3+. And the probe solution with Al3+ had a very high fluorescence quantum yield (89.29 %). The detection limit was calculated to be 1.135 nM, which was significantly lower than many reported detection limits, indicating that the probe JHK had pretty good sensitivity. The ratio of JHK to Al3+ (1:1) and the sensing mechanism were determined by Job's plot, 1H NMR spectra, FTIR spectra, ESI-MS and Gaussian calculation. The probe solution and medium-speed filter paper were successfully used to make test papers for more convenient detection of Al3+. Furthermore, the probe JHK had been successfully applied to the detection of Al3+ in real water, zebrafish and living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe EDPH specializes in the detection of H 2 S with high selectivity, high sensitivity and good detection limits. • The probe EDPH has been shown to have applications in intracellular fluorescence imaging. • Purine-based fluorescent probes for the detection of H 2 S are a new direction. Hydrogen sulfide (H 2 S) is a gas with a toxic odor that plays an irreplaceable role in physiological activities within the mammalian body. Therefore, it is important to do the distribution and quantitative detection of H 2 S in mammalian cells. In this paper, a fluorescence probe (EDPH) based on purine scaffold was designed and synthesized with high sensitivity and good selectivity. H 2 S induced ether bond breakage in EDPH , resulting in a significant redshift of the absorption band (from 370 nm to 500 nm) with a Stokes shift of 130 nm. After the addition of H 2 S, the fluorescence intensity of EDPH showed a good linear correlation with the concentration of H 2 S, which enabled the quantitative detection of H 2 S with a low limit of detection (41 nM). Finally, the EDPH was applied to the cellular Hele, and the probe has good cellularity imaging capability for the detection of H 2 S in living systems. [ABSTRACT FROM AUTHOR]

The abnormally elevated expression level of glutathione (GSH) has been observed in various human cancer cells and tissue. Thus, effective methods for glutathione detection are of great importance in early diagnosis of cancer. However, many fluorescent probes for GSH detection suffer from the interference of the abundantly existent nucleophilic biomolecules in biological environment. In this work, we propose a sequential activation strategy to overcome this problem by designing and synthesizing a series of 1,3,5-triazinyl resorufin turn-on fluorescent probe (Probes 1–3). As two electrophilic sites are presented in probes, GSH sequentially reacts with the resorufin and the triazine moiety, resulting in significant fluorescence augmentation (up to 165.0-fold). Designed probes possess low limit of detection as low as 1.8 μM). Cellular fluorescent imaging has been successfully applied to selectively detect GSH in several living cells. [Display omitted] • Novel sequential activation strategy allows the Probe 1–3 to detect GSH with high selectivity. • Designed fluorescent probes exhibited strong fluorescence intensity as response. • Designed probes realized GSH visualization in multiple cells with high fidelity. [ABSTRACT FROM AUTHOR]

[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]