Rapid Turn-on Research Articles

In-situ growth of cobalt oxyhydroxide on graphitic-phase C3N4 nanosheets for fluorescence turn-on detection and imaging of ascorbic acid in living cells.

Cobalt oxyhydroxide (CoOOH) was grown on the surface of graphitic-phase C3N4 nanosheets to obtain an activatable fluorescent nanoprobe for ascorbic acid (AA). The probe was applied to the detection of AA in biological fluids and to image AA in HeLa cells. The negatively charged nanosheets first adsorb Co2+, and then the CoOOH nanoflakes are generated in-situ on the surface of g-C3N4. This results in the quenching of the blue fluorescence (with excitation/emission maxima of 345/435nm) via fluorescence resonance energy transfer from g-C3N4 to CoOOH. The AA-induced redox reaction reduces the trivalent cobalt ion in CoOOH to Co2+ which then becomes released from the nanosheets. This leads to the recovery of fluorescence. The method can quantify AA in the 1.0 to 800μM concentration range at near neutral pH values. When applied to cell extracts, the limit of detection is 0.14μM. The nanoprobe was successfully applied to the determination of AA in serum and urine, and to image AA in living HeLa cells. Additional attractive features include the ease of preparation, low cytotoxicity, rapid fluorometric turn-on response, and good biocompatibility. Graphical abstract Schematic presentation of an activatable fluorescent nanoprobe. It consists of CoOOH nanoflakes that were modified withg-C3N4 nanosheets. It enables monitoring of AA in the biological samples as well as imaging of AA in living cells.

Operation Mechanism of a MoS₂/BP Heterojunction FET.

The electrical characteristics and operation mechanism of a molybdenum disulfide/black phosphorus (MoS2/BP) heterojunction device are investigated herein. Even though this device showed a high on-off ratio of over 1 × 107, with a lower subthreshold swing of ~54 mV/dec and a 1fA level off current, its operating mechanism is closer to a junction field-effect transistor (FET) than a tunneling FET. The off-current of this device is governed by the depletion region in the BP layer, and the band-to-band tunneling current does not contribute to the rapid turn-on and extremely low off-current.

A red to near-infrared fluorescent probe featuring a super large Stokes shift for light-up detection of endogenous H2S

In this work, a new reaction-based red to near-infrared (NIR) fluorescent turn-on probe for H2S was developed. This probe uses a readily prepared dicyanoisophorone as the fluorophore and a 2, 4-dinitrobenzenether with an ortho-aldehyde group as the reaction site. Upon addition of H2S, a fast nucleophilic addition of H2S to the aldehyde group and a following efficient intramolecular thiolysis of dinitrophenyl ether occurred, which leads to release the fluorophore and give a rapid NIR fluorescence turn-on response for H2S with a super large Stokes shift (244 nm). The fluorescence enhancement was found up to 105-fold and the detection limit was determined to be as low as 42 nM. Importantly, this probe shows high selectivity and sensitivity for H2S without interference from biothiols. Furthermore, NIR fluorescent imaging of exogenous and endogenous H2S in living cells with this probe was also successfully applied. All the results indicate that this probe is excellent and highly valuable.

A dicyanoisophorone-based near-infrared fluorescent probe and its application for detecting thiophenols in water and living cells

We report herein a new dicyanoisophorone-based colorimetric and near-infrared (NIR) fluorescent probe for rapid detection of thiophenols. This probe possesses a remarkable large Stokes shift (208 nm) and works in almost pure aqueous solution under mild conditions. More importantly, it displays a rapid, highly selective and sensitive dual colorimetric and NIR fluorescent turn-on signal responses for thiophenols and allows the detection of thiophenols in the presence of analytes including amino acids, biothiols and aliphatic thiols. Moreover, the fluorescence of this probe at 655 nm displays a good linear relationship with the thiophenol concentration ranging from 0 to 20 μM, and the detection limit is as low as 12 nM. Furthermore, the practicability of this new probe has been successfully proved by detection of thiophenol in real water samples and bioimaging of thiophenol in living cells.

A Multi-signal Fluorescent Probe with Multiple Binding Sites for Simultaneous Sensing of Cysteine, Homocysteine, and Glutathione.

A novel fluorescent probe was developed by integrating chlorinated coumarin and benzothiazolylacetonitrile and exploited for simultaneous detection of cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). Featuring four binding sites and different reaction mechanisms for different biothiols, this probe exhibited rapid fluorescence turn-on for distinguishing Cys, Hcy, and GSH with 108-, 128-, 30-fold fluorescence increases at 457, 559, 529 nm, respectively, across different excitation wavelengths. Furthermore, the probe was successfully applied to the fluorescence imaging of endogenous Cys and GSH and exogenous Cys, Hcy, and GSH in living cells.

A rapid cell-permeating turn-on probe for sensitive and selective detection of sulfite in living cells.

A rapid cell-permeating probe NJUXJ-1 was introduced for sensitive and selective detection of sulfite in living cells. It generated a turn-on response to sulfite with high sensitivity (detection limit 13.0 nM) and selectivity (at a physiological level) and low toxicity. The fluorescence of the detecting system was steady for a wide pH range (5-8) and a long period of time (over 12 h). The most attractive point, its rapid cell-permeating ability, made it suitable for bioimaging with a 2 min incubation time and shortened the whole detecting period (cell-permeation and reaction), and thus could decrease background interference. It offered a convenient approach for determining exogenous or endogenous sulfite levels in living cells and further applications.

2D g-C3N4–MnO2nanocomposite for sensitive and rapid turn-on fluorescence detection of H2O2and glucose

2D g-C3N4–MnO2nanocomposite for sensitive and rapid turn-on fluorescence detection of H2O2and glucose.

Molecular Engineering of α-Substituted Acrylate Ester Template for Efficient Fluorescence Probe of Hydrogen Polysulfides.

In this article, hydrogen polysulfide (H2Sn)-mediated Michael addition/cyclization cascade reactions toward acrylate ester analogues were exploited and utilized to construct novel and robust H2Sn-specific fluorescence probe for the first time. Through rational molecular engineering of the α-substituted acrylate ester template, the optimal candidate probe FP-CF3 containing trifluoromethyl-substituted acrylate ester group as recognition unit and 3-benzothiazol-7-hydroxycoumarin dye BHC as signal reporter can highly selectively detect H2Sn over other reactive sulfur species, especially biothiols including cysteine (Cys) and homocysteine (Hcy)/glutathione (GSH), with a rapid and significant turn-on fluorescence response (less than 60 s for response time and over 44-fold for signal-to-background ratio). The fast response and high selectivity of FP-CF3 for H2Sn could be attributed to a kinetically and spatially favored pentacyclic addition produced by the dual nucleophilic reaction of H2Sn with the CF3-substituted acrylate group. The big off-on fluorescence response is due to the pentacyclic intermediate results in the release of the highly fluorescent BHC. Moreover, it has been successfully applied in imaging of endogenous H2Sn fluctuation in living cells.

P.3.d.003 - Aripiprazole once-monthly long-acting injectable in schizophrenia

A new simple and readily available fluorescent probe for cysteine (Cys) was reported. This probe is based on an excited-state intramolecular proton transfer (ESIPT) dye and uses two acrylate moieties as the Cys reaction sites to promote signal changes. Importantly, this probe shows rapid fluorescent turn-on signal changes for Cys with high selectivity and sensitivity over various analytes including the similar structured homocysteine (Hcy) and glutathione (GSH) in aqueous solution under mild conditions. The detection limit of this probe for Cys was found to be as low as 0.80 μM, which is far below the normal content of Cys (30–200 μM) in cells. This probe was also successfully applied for bioimaging of intracellular Cys in living cells with low cytotoxicity. Besides, a paper test strip system was developed with this probe for a convenient detection of Cys.

A novel near-infrared fluorescent probe for sensitive detection of β-galactosidase in living cells

A novel near-infrared fluorescent probe for β-galactosidase has been developed based on a hemicyanine skeleton, which is conjugated with a d-galactose residue via a glycosidic bond. The probe serves as a substrate of β-galactosidase and displays rapid and sensitive turn-on fluorescent responses to β-galactosidase in aqueous solution. A 12.8-fold enhancement of fluorescence intensity at 703 nm was observed after incubation of 10 nM of β-galactosidase with 5 μM probe for 10 min. The probe can sensitively detect as little as 0.1 nM of β-galactosidase and shows linear responses to the enzyme concentration below 1.4 nM. The kinetic study showed that the probe has high binding affinity to β-galactosidase with Km = 3.6 μM. The probe was used to detect β-galactosidase in living cells by employing the premature cell senescence model. The probe exhibited strong fluorescent signals in senescent cells but not in normal cells, which demonstrates that the probe is able to detect the endogenous senescence-associated β-galactosidase in living cells.

A novel turn-on fluorescent strategy for sensing ascorbic acid using graphene quantum dots as fluorescent probe

In this paper, a facile and rapid fluorescence turn-on assay for fluorescent detection of ascorbic acid (AA) was developed by using the orange emission graphene quantum dots (GQDs). In the presence of horse radish peroxidase (HRP) and hydrogen peroxide (H2O2), catechol can be oxidized by hydroxyl radicals and converted to o-benzoquinone, which can significantly quench the fluorescence of GQDs. However, when AA present in the system, it can consume part of H2O2 and hydroxyl radicals to inhibit the generation of o-benzoquinone, resulting in fluorescence recovery. Under the optimized experimental conditions, the fluorescence intensity was linearly correlated with the concentration of H2O2 in the range of 3.33–500µM with a detection limit of 1.2µM. The linear detection for AA was in the range from 1.11 to 300µM with a detection limit of 0.32µM. The proposed method was applied to the determination of AA in human serum samples with satisfactory results.

A rapid and sensitive turn-on fluorescent probe for ascorbic acid detection based on carbon dots–MnO2 nanocomposites

A rapid turn-on fluorescent probe is proposed for the sensitive and specific determination of ascorbic acid based on carbon dots–MnO2 nanocomposites.

A simple and readily available fluorescent turn-on probe for cysteine detection and bioimaging in living cells

A new simple and readily available fluorescent probe for cysteine (Cys) was reported. This probe is based on an excited-state intramolecular proton transfer (ESIPT) dye and uses two acrylate moieties as the Cys reaction sites to promote signal changes. Importantly, this probe shows rapid fluorescent turn-on signal changes for Cys with high selectivity and sensitivity over various analytes including the similar structured homocysteine (Hcy) and glutathione (GSH) in aqueous solution under mild conditions. The detection limit of this probe for Cys was found to be as low as 0.80 μM, which is far below the normal content of Cys (30–200 μM) in cells. This probe was also successfully applied for bioimaging of intracellular Cys in living cells with low cytotoxicity. Besides, a paper test strip system was developed with this probe for a convenient detection of Cys.

Emissive H-Aggregates of an Ultrafast Molecular Rotor: A Promising Platform for Sensing Heparin.

Constructing "turn on" fluorescent probes for heparin, a most widely used anticoagulant in clinics, from commercially available materials is of great importance, but remains challenging. Here, we report the formation of a rarely observed emissive H-aggregate of an ultrafast molecular rotor dye, Thioflavin-T, in the presence of heparin, which provides an excellent platform for simple, economic and rapid fluorescence turn-on sensing of heparin. Generally, H-aggregates are considered as serious problem in the field of biomolecular sensing, owing to their poorly emissive nature resulting from excitonic interaction. To the best of our knowledge, this is the first report, where contrastingly, the turn-on emission from the H-aggregates has been utilized in the biomolecule sensing scheme, and enables a very efficient and selective detection of a vital biomolecule and a drug with its extensive medical applications, i.e., heparin. Our sensor system offers several advantages including, emission in the biologically advantageous red-region, dual sensing, i.e., both by fluorimetry and colorimetry, and most importantly constructed from in-expensive commercially available dye molecule, which is expected to impart a large impact on the sensing field of heparin. Our system displays good performance in complex biological media of serum samples. The novel Thioflavin-T aggregate emission could be also used to probe the interaction of heparin with its only clinically approved antidote, Protamine.

40 - Novel Selective Fluorescent Probes for Imaging Superoxide, Peroxynitrite, Hypochlorous Acid, Hydrogen Peroxide and Hydroxyl Radical

Remarkable advances of biological understanding have been made on the complex roles of reactive oxygen/nitrogen species (ROS/RNS) both as signaling molecules and pathogenic contributors in health and disease contexts. However, due to a persistent lack of reliable molecular tools, particularly small-molecule fluorogenic probes with decisively robust properties such as selectivity, sensitivity, chemo-/photo-stability, organelle-specificity, and rapid turn-on, researchers continue to face challenges of how to establish a strong mechanistic base for ever more intricate phenomena. Here we report the design, synthesis and application of several efficient fluorescent probes (HKSOX, HKGreen/Yellow, HKOCl, HKPerox, and HKOH series) for the selective detection and molecular imaging of endogenous superoxide, peroxynitrite, hypochlorous acid, hydrogen peroxide and hydroxyl radical, respectively, with cytosol, mitochondria and lysosome targeting capacity. Those probes open up exciting opportunities for establishing new experimental paradigms and accelerating mechanistically focused biological discoveries.

Lighting up carbon monoxide in living cells by a readily available and highly sensitive colorimetric and fluorescent probe

Carbon monoxide (CO) is an important gasotransmitter in living systems. The biological detection of this gasotransmitter is still in its infancy and urgently needs probes. In this paper, a novel fluorescent probe system, which is based on the Pd0-mediated Tsuji–Trost reaction, is reported for rapid detection of CO both in in vitro and in living cells. This probe system is readily available and shows excellent sensing properties for CO including rapid and distinct colorimetric and fluorescent turn-on responses, high selectivity and sensitivity with a low detection limit (25nM) in aqueous solution under mild conditions. In addition, fluorescent imaging of CO in living cells can be conveniently achieved by a low dose of this probe system.

Exploitation and Application of a Highly Sensitive Ru(II) Complex-Based Phosphorescent Chemodosimeter for Hg2+ in Aqueous Solutions and Living Cells

A novel Ru(II) complex-based phosphorescent probe Rubpy-1 was designed and synthesized conveniently by incorporating of chemodosimeter into the luminophor, which exhibits good water solubility, longer excitation wavelength, and rapid turn-on phosphorescent response only toward Hg(2+) in aqueous system under physiological pH. The spectral response mechanism and Hg(2+)-promoted structure change of the chemodosimeter were analyzed in detail by theoretical calculations and electrospray ionization mass spectrometry. When time-resolved photoluminescence techniques were used, the Rubpy-1 could eliminate effectively the signal interference from the short-lived background fluorescence in complicated media, accompanied by the significant improvement of the signal-to-noise ratio and the accuracy of the detection. Furthermore, Rubpy-1 showed low cytotoxicity and excellent membrane permeability toward living cells, which was successfully applied to monitor intracellular Hg(2+) effectively by confocal luminescence imaging.

A readily available colorimetric and near-infrared fluorescent turn-on probe for rapid and selective detection of cysteine in living cells

A readily available naphthofluorescein-based near-infrared (NIR) fluorescent probe was reported for rapid, colorimetric and NIR fluorescent turn-on detection of cysteine (Cys) with high selectivity and sensitivity over various analytes including the similar structured homocysteine (Hcy) and glutathione (GSH). This probe was successfully applied to bioimage intracellular Cys in living cells with low cytotoxicity.

A selective fluorescence turn-on sensing system for evaluation of Cu2+ polluted water based on ultra-fast formation of fluorescent copper nanoclusters

We report on a rapid and selective fluorescence turn-on detection system for Cu2+ based on the formation of highly fluorescent copper nanoclusters (CuNCs).

Transient quantum coherent response to a partially coherent radiation field

The response of an arbitrary closed quantum system to a partially coherent electric field is investigated, with a focus on the transient coherences in the system. As a model we examine, both perturbatively and numerically, the coherences induced in a three level V system. Both rapid turn-on and pulsed turn-on effects are investigated. The effect of a long and incoherent pulse is also considered, demonstrating that during the pulse the system shows a coherent response which reduces after the pulse is over. Both the pulsed scenario and the thermally broadened CW case approach a mixed state in the long time limit, with rates dictated by the adjacent level spacings and the coherence time of the light, and via a mechanism that is distinctly different from traditional decoherence. These two excitation scenarios are also explored for a minimal "toy" model of the electronic levels in pigment protein complex PC645 by both a collisionally broadened CW laser and by a noisy pulse, where unexpectedly long transient coherence times are observed and explained. The significance of environmentally induced decoherence is noted.