Reaction-based Fluorescent Probe Research Articles

A novel reaction-based fluorescent probe for the detection of cysteine in milk and water samples

A novel fluorescent probe 3′-hydroxy-3-oxo-3H-spiro [isobenzofuran-1,9′-xanthene]-6′-yl-2,4-dinitrobenzenesulfonate (probe 1) was designed and synthesized as a visual sensor for the detection of cysteine levels in milk and water samples. The addition of cysteine to the solution of probe 1 resulted in an increase in fluorescence intensity and color change, from light yellow to yellow-green. The distinct color response indicated that probe 1 could be used as a visual sensor for cysteine. Cysteine can be detected quantitatively at concentrations between 0 and 400 μM and the detection limit of the fluorescence response to the probe was 6.5 μM. This suggests that probe 1 could be used as a signaling tool to determine the cysteine levels in samples, such as milk and water.

A novel reaction-based fluorescent probe for sensitive and selective detection of Cu 2+

A novel reaction-based fluorescent probe (2) for Cu2+ was designed and synthesized. 2 exhibited remarkable fluorescence enhancement (65-fold) after the addition of Cu2+. Base on the absorption spectra, fluorescence spectra, ESI-MS and 1H NMR spectra analysis, the fluorescence response was attributed to Cu2+-promoted hydrolysis of the picolinate moiety to yield a highly fluorescent product, 6-acetyl-2-hydroxynaphthalene (1). Moreover, 2 not only displayed a rapid response time (within 6 min), high sensitivity (detection limit of 8.5 nM), and high selectivity for Cu2+ over other metal ions, but also could detect Cu2+ by absorption spectra, fluorescence spectra, even an obvious fluorescence color change at room temperature.

A reaction-based ratiometric fluorescent sensor for the detection of Hg(ii) ions in both cells and bacteria.

A novel reaction-based fluorescent probe (ATC-Hg) was designed and synthesized via the "covalent assembly" principle, which exhibited excellent selectivity and high sensitivity for Hg2+ and CH3Hg+. Moreover, it is the first Hg(ii) sensitive fluorescent probe that has been successfully applied in imaging in both cells and Escherichia coli.

Reaction-based fluorescent probe for the selective and sensitive detection of thiophenols with a large Stokes shift and its application in water samples.

Although widely used in organic synthesis, pharmaceuticals and agrochemicals, thiophenol has brought about a series of ecological problems due to its high toxicity. Therefore, the development of efficient methods to discriminate thiophenols from aliphatic thiols is of great importance. In this work, a new reaction-based turn-on red fluorescence probe for the detection of thiophenols has been developed for the first time by employing dicyanomethylene-4H-pyran (DCM) as a fluorescence reporter and 2,4-dinitrobenzene-sulfonate (DNBS) as a recognition unit. The probe displayed a highly selective and sensitive (63 fold-fluorescence enhancement) response to thiophenols over aliphatic thiols. Additionally, the probe also exhibited a large Stokes shift (159 nm) and the detection limit reached as low as 8.3 nM. Moreover, this probe was also proved suitable for the quantification of thiophenol in real environmental water samples.

Reaction-based fluorescent probes for rapid detection of hydrogen sulfide in vivo

The probe exhibited high sensitivity, selectivity, and fast response for real-time detection of H2S in vivo.

Reaction-Based Fluorescent Probes for the Imaging of Nitroxyl (HNO) in Biological Systems.

Nitroxyl (HNO) has been identified as an important signaling molecule in biological systems and plays critical roles in many physiological processes. Fluorescence imaging could provide a robust approach to explore the biological formation of HNO and its physiological functions. Herein, we summarize the organic reaction types for constructing HNO probes and specifically focus on review of the recent advances in the development of the reaction-based HNO probes and their imaging applications in living systems.

Selective Modulation of Internal Charge Transfer and Photoinduced Electron Transfer Processes in N-Aryl-1,8-Naphthalimide Derivatives: Applications in Reaction-Based Fluorogenic Sensing of Sulfide.

Three reaction-based fluorescent probes based on two new naphthalimide platforms were developed for the detection of H2S. A new approach in detecting H2S by the reduction of an azide to a triazene intermediate in aqueous media is reported. Given their design features, these chemodosimeters provide useful insights into the relatively unexplored area of C0 spacers between receptor:reporter components. The N-aryl-1,8-naphthalimide platform features straightforward placement of the internal charge transfer and photoinduced electron transfer (PET) modulators on the same molecule. In the three examples presented, the N-aryl component proved to be an effective photophysical device as it allows the placement of a PET modulator at the strategically important and less explored imide position of 1,8-naphthalimides. These probes or dosimetric agents demonstrated good selectivity, two-signal response, and the desirable OFF-ON fluorescence response. By implementation of both the azido and nitro group as sulfide-reactive functionalities on the same chemosensory platform in probe SNAN-3, a much broader range of H2S can be detected. Remarkably, probe SNAN-3 exhibits both a dual-emission and dual-response for the detection of sulfide in aqueous solution.

Cu2+-selective fluorescent probe based on the hydrolysis of semicarbazide derivative of 2-(2-aminophenyl)benzothiazole

A new Cu2+-selective reaction-based fluorescent probe 1 based on the semicarbazide-bearing derivative of 2-(2-aminophenyl)benzothiazole has been developed. Designed probe 1 exhibited turn-on-type fluorescence signaling behavior that was more prominent toward Cu2+ ions than to other environmentally relevant metal ions. The signaling of probe 1 was due to the Cu2+-induced hydrolysis of semicarbazide moiety to form its strongly fluorescent parent dye. Cu2+ signaling of probe 1 was not influenced by the presence of commonly encountered metal ions, and the detection limit was 1.71 × 10−8 M (1.1 ppb). As a practical application, the determination of Cu2+ in simulated semiconductor wastewater was conducted using a smartphone as a portable signal detection tool. For the color test analysis, enhanced reproducibility of Cu2+-sensing was realized using the grayscale image rather than the red, green, or blue channel image.

Quantitative real-time imaging of glutathione

Glutathione plays many important roles in biological processes; however, the dynamic changes of glutathione concentrations in living cells remain largely unknown. Here, we report a reversible reaction-based fluorescent probe—designated as RealThiol (RT)—that can quantitatively monitor the real-time glutathione dynamics in living cells. Using RT, we observe enhanced antioxidant capability of activated neurons and dynamic glutathione changes during ferroptosis. RT is thus a versatile tool that can be used for both confocal microscopy and flow cytometry based high-throughput quantification of glutathione levels in single cells. We envision that this new glutathione probe will enable opportunities to study glutathione dynamics and transportation and expand our understanding of the physiological and pathological roles of glutathione in living cells.

Investigation of Drug-Induced Hepatotoxicity and Its Remediation Pathway with Reaction-Based Fluorescent Probes.

Drug-induced liver injury (DILI) is considered a serious problem related to public health, due to its unpredictability and acute response. The level of peroxynitrite (ONOO-) generated in liver has long been regarded as a biomarker for the prediction and measurement of DILI. Herein we present two reaction-based fluorescent probes (Naph-ONOO- and Rhod-ONOO-) for ONOO- through a novel and universally applicable mechanism: ONOO--mediated deprotection of α-keto caged fluorophores. Among them, Rhod-ONOO- can selectively accumulate and react in mitochondria, one of the main sources of ONOO-, with a substantial lower nanomolar sensitivity of 43 nM. The superior selectivity and sensitivity of two probes enable real-time imaging of peroxynitrite generation in lipopolysaccharide-stimulated live cells, with a remarkable difference from cells doped with other interfering reactive oxygen species, in either one- or two-photon imaging modes. More importantly, we elucidated the drug-induced hepatotoxicity pathway with Rhod-ONOO- and revealed that CYP450/CYP2E1-mediated enzymatic metabolism of acetaminophen leads to ONOO- generation in liver cells. This is the first time to showcase the drug-induced hepatotoxicity pathways by use of a small-molecule fluorescent probe. We hence conclude that fluorescent probes can engender a deeper understanding of reactive species and their pathological revelations. The reaction-based fluorescent probes will be a potentially useful chemical tool to assay drug-induced hepatotoxicity.

Reaction-based fluorescent turn-on probe for selective detection of thiophenols in aqueous solution and living cells

A novel turn-on florescent probe based on a nucleophilic substitution reaction was developed for the detection of thiophenols in aqueous solution and in living cells. In this probe, 10-hydroxyl derivative of coumarin 6H was selected as fluorophore, 2, 4-dinitrophenlate moiety acted simultaneously as recognition unit and fluorophore quencher. This probe features a remarkable large Stokes shift (128 nm) and shows a highly selective detection process for thiophenols with significant fluorescence turn-on response. Notably, biothiols, aliphatic thiols, amino acids and reducing anions do not interfere with the sensing of thiophenols. The probe shows good linearity ranges with low detection limit of 36 nM for thiophenols. More importantly, it was successfully applied for practical detection of thiophenols in real water samples with a good recovery and imaging of thiophenols in living cells, demonstrating its practical application in environmental samples and biological systems.

Self-restricted oxazolone GFP chromophore for construction of reaction-based fluorescent probe toward dopamine

The β-barrel provides a confined environment for chromophores of the green fluorescent protein (GFP) family, defining their emission profiles by the chromophore/β-barrel interactions. Here, we describe the generation of self-restricted oxazolone GFP chromophore (GFPc) for construction of reaction-based fluorescent probe toward dopamine by mimicking the confinement effect of the β-barrel. Through standard synthetic method, the first self-restricted GFPc oxazolone analogue (MBDO) and the conventional pyrenyl-based chromophore (PDO) were prepared respectively. Under the same condition, MBDO shows much better emission response with fluorescent quantum yield (QY) over one order of magnitude higher than that of PDO due to the generation of the self-restricted effect. And, the fluorescent QY of MBDO reaches above 30% in dimethyl sulfoxide, which is the largest ever recorded for unlocked GFPc analogues in highly polar solvents. Moreover, theoretical calculations further reveal that the enhanced emission of MBDO is due to the inhibition of conformational motions around the exocyclic CC bonds. Combination the enhanced emission and the reactivity of the lactone, MBDO is applied to construct reaction-based fluorescent probe toward dopamine via a ring-opening reaction of the lactone. Prospectively, the destruction of the oxazolone would break the effective conjugated structure of the chromophore, which can decrease the corresponding fluorescence. This work puts forward a novel approach to generate highly emissive GFPc oxazolone analogue, which can be used to fabricate reaction-based fluorescent probe toward dopamine, potentially promoting the biochemical applications using synthetic GFP chromophore analogues.

Rapid and highly sensitive detection of extracellular and intracellular H2S by an azide-functionalized Al(iii)-based metal-organic framework.

A new, azide-functionalized Al(iii)-based metal-organic framework (MOF) denoted as CAU-10-N3 (1, CAU = Christian-Albrechts-University) and consisting of the 5-azido-isophthalic acid (H2IPA-N3) ligand was employed as a reaction-based fluorescent turn-on probe for the detection of H2S. The activated compound (1') showed fast, selective and highly sensitive sensing properties for extracellular H2S in HEPES buffer (10 mM, pH = 7.4). The material retained its high selectivity even in the presence of possibly competing biological species. The limit of detection of 1' for H2S is 2.65 μM, which is lower than the earlier reports on MOFs for H2S sensing. The material displayed a short response time (420 s) and a significant increase (20-fold and 26-fold after 1 and 7 min of addition of Na2S, respectively) in the fluorescence intensity towards H2S. Macrophage cells loaded with probe 1' exhibited blue fluorescence with a response time of 15 min after Na2S addition, indicating the suitability of the probe for intracellular H2S detection. Moreover, CAU-10-N3 featured excellent detection performance (quick response and 32-fold increment in fluorescence intensity after 7 min of Na2S addition) in water. Hence, it can be utilized to regulate the H2S level in aqueous samples collected from the environment.

A reaction-based fluorescent probe for the selective detection of formaldehyde and methylglyoxal via distinct emission patterns

A simple and stable fluorescent probe L based on a novel ortho-diaminorhodamine derivative for discrimination and detection of formaldehyde (FA), methylglyoxal (MGO) and oxalaldehyde (OA) from other aldehydes has been developed. This reaction-based probe, displayed distinct emission patterns for FA (turn-on) and MGO (turn-off) by single wavelength excitation, can be used for imaging of FA and MGO in living cells.

A novel reaction-based fluorescent turn-on probe for biothiols and its application in cell imaging

In this work, a novel fluorescent probe (DOCOU) based on coumarin has been designed and synthesized for the detection of biothiols. In this probe, a new hydroxy-coumarin-based fluorescent dye, HOCOU, was firstly used as the fluorophore and 2, 4-dinitrobenzenesulfonyl (DNBS) group was incorporated as both a recognition unit and a fluorescence quencher. The probe DOCOU shows high selectivity and sensitivity for Cys, Hcy, and GSH over other amino acids and interfering species under physiological conditions. Mechanism study indicated that the remarkable fluorescence turn-on response is induced via a thiolate mediated SNAr reaction. Furthermore, DOCOU features good linearity ranges with low detection limit of 17.1nM for Cys, 14.5nM for GSH, and 40nM for Hcy, respectively. In addition, the probe was successfully applied for imaging biothiols in Hela cells with low cytotoxicity.

Cascade reaction-based fluorescent probe for detection of H2S with the assistance of CTAB micelles

We report a turn-on fluorescent probe for H2S through a cascade reaction using a new trap group 4-(bromomethyl)benzoate, based on excited-state intramolecular proton transfer (ESIPT) sensing mechanism. The probe showed good selectivity and high sensitivity towards H2S and it was capable of detecting and imaging H2S in living HeLa cells, indicating its potential biological applications.

Mitochondria-Targeted Reaction-Based Fluorescent Probe for Hydrogen Sulfide.

In this study, we developed a turn-on mitochondria-targeting hydrogen sulfide, "probe 1", based on the selective thiolysis of 7-nitro-1,2,3-benzoxadiazole amine moiety attached to the piperazine-based naphthalimide scaffold. Probe 1 exhibited excellent properties with 68-fold fluorescence enhancement, a low detection limit (2.46 μM), a low cytotoxicity, and a good selectivity toward hydrogen sulfide. The success of intracellular imaging indicated that probe 1 could be used in further applications for the investigation of biological functions and pathological roles of H2S in living systems.

A reaction-based fluorescent probe for rapid detection of hypochlorite in tap water, serum, and living cells

A highly sensitive and selective fluorescein-based fluorescent probe for the efficient detection of OCl− over other ions has been developed. The probe was successfully applied for quantitative detection of OCl− in real life water samples and bovine plasma with satisfactory results. Confocal fluorescence imaging of cells for detecting OCl− in vivo was carried, which could provide a potential and powerful approach for the detection of OCl− in biological system.

A reaction-based fluorescent turn-on probe for Cu2+ in complete aqueous solution

FP can detect Cu2+ in complete aqueous solution with a rapid response time, high sensitivity, and high selectivity.

Theoretical and Experimental Investigation of Thermodynamics and Kinetics of Thiol-Michael Addition Reactions: A Case Study of Reversible Fluorescent Probes for Glutathione Imaging in Single Cells.

Density functional theory (DFT) was applied to study the thermodynamics and kinetics of reversible thiol-Michael addition reactions. M06-2X/6-31G(d) with the SMD solvation model can reliably predict the Gibbs free energy changes (ΔG) of thiol-Michael addition reactions with an error of less than 1 kcal·mol(-1) compared with the experimental benchmarks. Taking advantage of this computational model, the first reversible reaction-based fluorescent probe was developed that can monitor the changes in glutathione levels in single living cells.