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Ferric ion (Fe3+) serves as an essential and indispensable inorganic element in various biological process. Excess Fe3+ is harmful for biological systems and human health. Herein, highly sensitive carbon quantum dots (Fe-CQDs) for ferric ions were synthesized by a high-efficiency, one-step hydrothermal route utilizing L-arginine and citric acid. The prepared Fe-CQDs exhibited good water solubility, high photostability, and bright blue florescence with relatively high quantum yields (QYs) over 21.33% and a Stokes shift exceeding 100 nm. The functionalized Fe-CQDs offer rapid, sensitive, and selective recognition of Fe3+ with a linear relationship from 0.6 to 80 μM and a low detection limit of 0.2 μM. Moreover, the synthesized Fe-CQDs illustrated strong anti-interference properties in samples and buffer solutions. The developed sensor demonstrated high biocompatibility and was successfully applied for intracellular Fe3+ determination in SHSY5Y and HT22 cells, illustrating excellent imaging application. The present work provides a promising platform for the early clinical diagnosis of Fe3+-associated diseases. [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]

[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]

Biothiols, including cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play key roles in biological processes, and detecting such thiols selectively is critical for understanding functions of biothiols. In this work, a pyridazine annelated perylene–based fluorescent probe PAPC is synthesized for highly selective detection of Cys. PAPC exhibits strong blue emission in PBS, while the red emission at 605 nm can be observed in the presence of Cys. The probe PAPC shows ratiometric fluorescence (I605/I460) detection of Cys with wide linear range of 1–120 μM and low detection limit of 0.19 μM. Super large Stokes shift (170 nm) and ratiometric fluorescence endow the probe low background signal. The discrimination of Cys over Hcy and GSH can be achieved through the difference of the ratiometric fluorescence. In addition, the probe has been proven to track Cys in real samples such as urine and HeLa cells. Therefore, PAPC probe is a promising candidate for detecting Cys in practical application. [ABSTRACT FROM AUTHOR]

A multiple turn-on fluorophore (FHCS), combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone into a molecule, was identified and developed based on density functional theoretical calculation. It was expected that FHCS could express exclusive fluorescent signals and improved Stokes shifts when chelating Al3+ or Zn2+. After it was synthesized and characterized in detail, it was noted that FHCS could turn-on fluorescently discriminate trace Al3+ and Zn2+ under the optimized conditions, i.e., from no-fluorescence to strong blue fluorescence for Al3+ and to green fluorescence for Zn2+ with low detection limits of 5.37 × 10−8 M and 7.90 × 10−8 M respectively. Owing to its low toxicity, FHCS was successfully applied for quantitative determination of Al3+ and Zn2+ in natural aqueous samples and toxicity evaluation of Al3+ and Zn2+ in living cells and bio-tissues with excellent linear relationships. The action mechanisms for FHCS with Al3+ and Zn2+ were confirmed to form stable 5-member-co-6-member condensed rings between Al3+/Zn2+ and N/O atoms in FHCS by both theoretic and experimental methods, which resulted in turn-on fluorescence with different dipolar moments and improved Stokes shifts. A multiple turn-on fluorophore, combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone into a molecule (FHCS), was identified and developed for turn-on fluorescently discriminate trace Al3+ and Zn2+ in natural aqueous, living cells and bio-tissue samples with quite low detection limits of 5.37 × 10−8 M and 7.90 × 10−8 M respectively. The action mechanisms for FHCS with Al3+ and Zn2+ were confirmed by both theoretic and experimental methods to form stable 5-member-co-6-member condensed rings between Al3+/Zn2+ and N/O atoms, which resulted in turn-on fluorescence with different dipolar moments and improved Stokes shift. Image 1 • A multiple turn-on fluorophore combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone was developed. • It could turn-on fluorescently monitor Al3+ and Zn2+ in aqueous. • It was applied for cell imaging of Al3+ and Zn2+ in bio-samples. • The reaction mechanism was to form stable 5-member-co-6-member condensed rings with improved Stokes shift. [ABSTRACT FROM AUTHOR]

• A novel NIR colorimetric-fluorescence probe was prepared for detection of hydrogen sulfide. • The probe showed rapid, specific and sensitive detection of hydrogen sulfide with a large Stokes shift. • The probe was capable of imaging hydrogen sulfide in living cells and mice. We presented here a novel near-infrared fluorescent probe based on 2-(2′-hydroxyphenyl)benzothiazole -dicyanoisophorone as fluorophore and 2,4-dinitrobenzenesulfonyl moiety as detection functionalized group for the discrimination of hydrogen sulfide (H 2 S). Probe L exhibited good specificity and sensitivity "turn on" response at 720 nm with a large Stokes shift (155 nm), rapid response (< 60 s) and low detection limit (3.15 × 10−7 M), which also could be identified by the naked eyes. Moreover, probe L was successfully used to image exogenous/endogenous H 2 S in cells and mice, which demonstrated its potential applications in living systems. A novel fluorescein based on 2-(benzo[ d ]thiazol-2-yl)phenol-dicyanoisophorone probe was constructed for the discrimination of hydrogen sulfide. The probe was applied for the rapid, sensitive, large Stokes shift, colorimetric and large near-infrared fluorometric determination of H 2 S, based on the displacement approach. The low cytotoxicity and excellent imaging performance was successfully applied for mitochondrial localization in living cells and endogenous and exogenous H 2 S detection in vivo. [Display omitted] [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]

The abnormal expression of cytochrome P450 2J2 (CYP2J2) is closely related to the proliferation of human cancer cells. In this study, a red-emitting probe with an aggregation-induced emission (AIE) effect for the quantification of CYP2J2 was developed by modifying the typical AIE fluorescent group tetraphenylethylene (TPE) through two-step synthesis. Upon addition of CYP2J2, the probe underwent O-demethylation and spontaneously 1,6-elimination reactions of p-hydroxybenzyl that allowed it to alter its photophysical properties, thus realizing light-up detection of CYP2J2 with extremely large Stokes shift (236 nm), excellent sensitivity and selectivity, low detection limit (1.09 nM). Moreover, this new AIE-active probe with good biocompatibility was admirably employed to tracking endogenous CYP2J2 in living cells. • An AIE-based fluorescent probe (TPE-Bn) was designed to detect CYP2J2. • This probe showed significant Stokes shift (236 nm), good photostability, excellent sensitivity and selectivity, and low cytotoxicity. • This probe can be used to visualize endogenous CYP2J2 in living cells and tissues. [ABSTRACT FROM AUTHOR]