Coumarin-based Fluorescent Probe Research Articles

A coumarin-based fluorescent probe with 4-phenylselenium as the active site for multi-channel discrimination of biothiols.

Biological mercaptans, also known as biothiols, play their own roles in a number of important physiological processes, and the abnormal levels of biothiols are closely associated with a variety of diseases. Therefore, the selective detection of biothiols in biological systems is crucial for understanding their roles in physiological processes and the early diagnosis of diseases. In this article, we developed a coumarin-based fluorescent probe (CouSePh) with 4-phenylselenium as the active site for the discriminative detection of all three biothiols. By introducing 4-phenylselenium as the active group, the probe CouSePh exhibits a rapid and sensitive response to three biothiols. For all three biothiols, the first-step sensing reaction is the nucleophilic substitution of 4-phenylselenium by the thiol group of biothiols, and they subsequently undergo three distinct intramolecular reactions to form three sensing products with different fluorescence emissions. The sensing mechanisms of the three biothiols have been demonstrated by spectral measurements and the analysis of high resolution mass spectrometry as well as the separation and characterization of the sensing product. Furthermore, by two-channel fluorescence imaging, probe CouSePh has been successfully applied in the discriminative detection of endogenous biothiols in living cells.

Role of folate metabolizing genes and homocysteine in mothers of Down syndrome children.

Folates are essential nutrients required for the synthesis of DNA/RNA in cell division and segregation. Folates are reduced and methylated in the liver with the help of enzymes such as methylenetetrahydrofolate reductase (MTHFR), MTR MTRR, reduced folate carrier 1, and cystathionine-β-synthase. Variants in the genes encoding these enzymes may lead to hypomethylation, resulting in nondisjunction which in turn increases the risk for Down syndrome (DS). The present study was conducted to genotype these genes and to see their association with homocysteine levels. A total of 213 mothers having DS children and 220 mothers having normal children were enrolled in the study. Genomic DNA was isolated from lymphocytes followed by polymerase chain reaction/Restriction Fragment Length Polymorphism for genotyping. Homocysteine levels were checked by chemoassay utilizing coumarin-based fluorescent probe. Genotypic frequency of MTHFR 1298 A > C polymorphism was significantly different among cases and controls (χ 2 = 5.83, P = 0.01), presence of C instead of A allele provided protection against DS in mothers (odds ratios = 0.57, 95% confidence interval = 0.35-0.91, P = 0.01). Higher levels of homocysteine were independently associated with the risk of having DS child (P = 0.0001). Homocysteine acted as an independent risk factor in the present study and was not associated with folate metabolizing gene variants.

A coumarin-based fluorescent probe for NIR imaging-guided photodynamic therapy against S. aureus-induced infection in mouse models.

A coumarin-based viscosity-responsive fluorescent probe (HZAU800) was designed and synthesized. The probe, containing a strong electron-donating and rigid group on the 7-position of coumarin and a rhodamine derivative containing an oxonium ion on 3-position, could not only shift the emission wavelength to near-infrared region (NIR, λem = 800 nm) but also deliver a good PDT effect due to its high rigid planarity. The NIR fluorescence of HZAU800 can be lighted up in the S. aureus-infected region due to its high viscous environment. Under the laser's irradiation at 690 nm, the PDT effect was effectively triggered up, and the antibacterial evaluation in vitro and in vivo was successfully carried out. This study not only offers a new strategy for constructing coumarin-based phototherapy agents but also facilitates the exploration of the next generation of antibacterial materials based on coumarin architectures.

A coumarin-based fluorescent probe for specific detection of cysteine in the lysosome of living cells

Cysteine (Cys), the only amino acid in the 20 natural amino acids that contains a reduced sulfhydryl group, plays important roles in the balance of redox homeostasis in biological systems. Lysosome is an important organelle containing a variety of hydrolases and has been proved to be the decomposition center of a variety of exogenous and endogenous macromolecular substances. In this research, a coumarin-based fluorescent probe MCA for the detection of Cys in lysosomes of living cells was developed. Due to the acrylate moiety, this probe exhibited high sensitivity (detection limit = 6.8 nM) and selectivity towards Cys superior to other analytes. Moreover, the probe was proved to be lysosome-targetable and showed good cell imaging ability and low cell toxicity.

Coumarin-based Fluorescent Probes for Bioimaging: Recent Applications and Developments

Coumarin-based derivatives have easy modification and tunable properties and have been synthesized and applied in many areas including pro-drugs, biomedical materials, and chemical and biological sensing. In this review, recent advances of coumarin-based fluorescent probes for biosensing are reported for metal ion imaging. Metal detection in living cells are highlighted with representative examples together with fluorescence response mechanisms such as Photoinduced Electron Transfer (PET), Intramolecular Charge Transfer (ICT), and Fluorescence Resonance Energy Transfer (FRET). Some future perspectives are also briefly mentioned.

A Novel Coumarin-based Fluorescent Probe with Aggregation Induced Emission for Detecting CN- and its Applications in Bioimaging.

Although cyanogen ion (CN-) plays important role in industry which also bring acute environmental pollution. More serious, trace CN- enters the human body can cause serious consequences and even death. Therefore, it is of great significance to detect trace CN- with high sensitivity. Herein, a novel aggregation-induced emission (AIE) probe C-BH was synthesized based on coumarin matrix. Probe C-BH showed high selectivity and sensitivity toward CN- by dual channel response due to the excited state intramolecular proton transfer (ESIPT). The low detection limit was calculated to be 0.05µM. Moreover, probe C-BH was successfully used for imaging CN- in living cells and zebrafish due to its low toxicity and excellent optical properties.

Dual detection of mercury (II) and lead (II) ions using a facile coumarin-based fluorescent probe via excited state intramolecular proton transfer and photo-induced electron transfer processes

A Schiff base fluorophore coumarin incorporated 4-(diethylamino)salicylaldehyde (Cou-S) is designed and synthesized to allow an excited state intramolecular proton transfer and photo-induced electron transfer processes for detecting toxic heavy metal ions of Hg2+ and Pb2+ in aqueous samples. The solid blue emission of Cou-S was gradually quenched to weak cyan in Hg2+ detection and to green channels in the presence of Pb2+. The coordination behaviours of the probe with Hg2+/Pb2+ are studied using a series of spectroscopic measurements and density functional theory (DFT) calculations. The probe exhibited good water solubility, great selectivity and excellent sensitivity with the LOD values of 8.3 and 10.5 nM for Hg2+ and Pb2+ in aqueous medium, respectively. The utility of Cou-S towards dual ions detection was explored in various sources of water samples, Whatmann paper strips, Boolean logic NOR gate operations and PC3 live cells, demonstrating the promising on-site visualization of the probe in controlling the toxicity levels in waste water sources and biosystems.

A Novel Coumarin-based Fluorescent Probe for Recognition of Copper(II) Ions and Its Application in Bioimaging.

Simple, accurate and real-time analytical methods are required for the detection of metal ions in a complex environment. In the present work, a fluorescent probe CPB based on coumarin was designed for recognizing Cu2+ ions. The fluorescence of CPB gradually quenched with increasing concentration of Cu2+ ions, due to the interactions between CPB and Cu2+ ions. With the addition of Cu2+ ions, the emission changes of CPB exhibited a good liner relationship toward the Cu2+ ions content in solution. Additionally, CPB could highly selective recognize Cu2+ ions among other metal ions in solution. Bearing the selectivity and fluorescence property toward Cu2+ ions, CPB was successfully applied to monitoring Cu2+ ions in Hela cells and zebrafish.

Highly sensitive and selective “turn-off” fluorescent probes based on coumarin for detection of Cu2+

As the third most abundant trace element in human internal environment, Cu2+ has a significant impact on organisms and ecosystems. The determination of Cu2+ is an important topic in the field of environmental protection and food safety. In this study, a coumarin-based fluorescent probe (denoted by ICTAB) was designed and synthesized. The results indicate that ICTAB is a “turn-off” fluorescent probe for Cu2+, with extremely high selectivity and sensitivity. The limit of detection is down to 0.27 μM. Mass spectroscopy and Job's plot show that ICTAB and Cu2+ form 2:1 coordinate complexes, and the specific binding sites of Cu2+ on ICTAB were determined by FTIR and 1H NMR. More importantly, the fluorescent emission of ICTAB can be repeatedly recovered by removing Cu2+ with S2−, which functions as an effective “turn-off” fluorescent probe. ICTAB demonstrated over 89% of recoveries as being applied in detecting Cu2+ in water.

A new coumarin based Schiff base fluorescence probe for zinc ion

Herein, a novel coumarin-based fluorescent probe ( FS3 ) was designed, synthesized, and characterized. It exhibited significant fluorescence quenching in the presence of Zn 2+ ions. Just a minor alteration occurred in the fluorescence intensity of FS3 in the presence of other metals studied. The limit of detection for the determination of Zn 2+ by FS3 was calculated to be 3.43 × 10 −9 M. Since the Job’s graph of 1/(F 0 –F) and 1/[Zn 2+ ] had a linear fit, it was determined that the binding stoichiometry between the FS3 and Zn 2+ was 1:1. The association constant of the system was found to be 2.39 × 10 4 M − 1 and confirmed by ESI-MS and FT-IR. It was demonstrated that the developed highly reversible sensor system works by performing real sample analysis. Moreover, the FS3 which has shown no toxicity and displayed a strong fluorescence image will act as an efficient and non-destructive sensor for the determination of Zn 2+ in living organisms. • A novel coumarin-based fluorescent probe (FS3) was designed, synthesized, and characterized. • Significant fluorescence quenching was observed in the presence of Zn 2+ ions. • Stoichiometry between the FS3 and Zn 2+ was 1:1. • The association constant for Zn 2+ binding with FS3 was found to be 2.39 × 10 4 M −1 according to the Benesi-Hildebrand method.

Development of a coumarin-based fluorescent probe for hydrogen peroxide based on the Payne/Dakin tandem reaction

Hydrogen peroxide (H2O2) is associated with many physiological and pathological processes in biological systems. Here, we report 7-diethylamino-3-formyl-coumarin (Cou-CHO) as a turn-on fluorescent probe for H2O2. The proposed probe employs a tandem Payne/Dakin reaction to convert the electron-withdrawing aldehyde to the electron-donating hydroxyl group, thus hindering the formation of twisted intramolecular charge transfer (TICT) state of 7-diethylaminocoumarin, and thereby resulting in a fluorescence turn-on response. Cou-CHO features high specificity, excellent sensitivity and fast response toward H2O2. In particular, Cou-CHO enables the direct visualization of basal and endogenously produced H2O2 in living cells. The results demonstrate that the tandem Payne/Dakin reaction can provide a new choice to develop H2O2-selective probes.

Hydrazone derivative bearing coumarin for the relay detection of Cu2+ and H2S in an almost neat aqueous solution and bioimaging in lysosomes

A new morpholine functionalized coumarin-based fluorescent probe 1 was easily synthesized. The probe realized the sequentially detecting of Cu2+ and H2S in the HEPES buffer solution (20 mM, pH = 5.0). It made a turn-off fluorescence response to Cu2+ by using a complex formation with a 2:1 binding mode, and the resulting complex was able to detect H2S according to the displacement approach with a turn-on fluorescence response. The detecting limits of probe 1 for Cu2+ and 1–Cu2+ system for H2S were calculated to be 26 nM and 88.5 nM, respectively. This “on-off-on” recognition process was demonstrated by ultraviolet–visible spectroscopy, fluorescence spectroscopy, using proton nuclear magnetic resonance studies, electrospray ionization mass spectroscopy, single crystal X-ray diffraction, and using density functional theory calculations. In addition, both cell imaging and co-staining experiments showed that the probe could be utilized to visually detect Cu2+ and H2S in lysosomes.

A metal-free coumarin-based fluorescent probe for the turn-on monitoring of carbon monoxide in an aqueous solution and living cells.

Endogenous carbon monoxide (CO) is an essential cell signaling molecule, which is closely related to numerous physiological and pathological processes. Therefore, it is of great significance to monitor CO in living samples. Fluorescent probe technique provides an effective and convenient method for monitoring CO. Although many fluorescent probes of CO have been reported, most of them require the introduction of heavy metal ions (Pd2+), which is not conducive to the practical application of these probes. Herein, a metal-free coumarin-based fluorescent probe was developed for monitoring CO. For this probe, coumarin was selected as the fluorophore, the aromatic nitro group was used as the reactive site, and the carboxyl moiety acted as the water-soluble unit. As a result, this probe has been proved to be able to monitor CO with good specificity and excellent sensitivity in water medium. After interacting with CO, the aromatic group was reduced to an aryl amino group; accordingly, the emission intensity of the peak corresponding to the probe at 450 nm significantly increased. Moreover, it successfully realized the detection of CO in living cells by a fluorescence signal.

Development of an ultrafast fluorescent probe for specific recognition of hypochlorous acid and its application in live cells.

Hypochlorous acid (HOCl), a highly potent oxidant of reactive oxygen species, plays critical roles in many physiological and pathological processes. In this work, a novel coumarin-based fluorescent probe, Cou–HOCl, was prepared for the detection of HOCl. The probe exhibited good selectivity over other analytes, excellent sensitivity with a detection limit of 16 nM, and fast response within 5 s. And further study demonstrated that the probe could be used not only to image exogenous HOCl in various cells, but also to determine the fluctuating levels of HOCl in macrophage cells during inflammation.

Coumarin-based fluorescent probe for the detection of glutathione and nitroreductase

With this research we set out to develop a coumarin-based novel fluorescent probe NTR-AHC for the detection of biological thiols and nitroreductase (NTR). Probe NTR-AHC was constructed by attaching the NTR trigger moiety (p-nitrobenzyl) and biothiol acceptor (maleic acid monoamide), to the core fluorophore AHC. In the presence of both glutathione (GSH) and NTR, probe NTR-AHC produced a >8-fold increase in fluorescence intensity at 463 nm.

Theoretical study on the sensing mechanism of a coumarin-based fluorescent probe for biological thiols

The sensing mechanism of a reported fluorescence probe for cysteine, homocysteine and glutathione (Yin et al., 2018) has been investigated by time-dependent density functional theory. Experimental absorption and emission spectra of the probe before and after thiol addition were reproduced well by theoretical calculations, which validated the rationality of the method. Optimized geometries showed that the probe molecule had distinctly different geometries in its ground and excited states. It corresponded to the photoisomerization process and explained the weak fluorescence of the probe molecule. Moreover, by the potential energy curve scan, photoisomerization was further confirmed to be a spontaneous process with a barrier that barely existed. Frontier orbital analysis indicated that this photoinduced isomerization of the probe molecule derived from the antibonding character for lowest unoccupied molecular orbital at its CC double bond. In contrast, probe-thiol complexes exhibited similar geometries in their ground and excited states, which was responsible for the strong fluorescence of the probe with thiols. Due to distinct excited-processes, the probe can be used to sense thiols by monitoring the fluorescent change.

A Coumarin-Based Fluorescent Probe for Ratiometric Detection of Cu2+ and Its Application in Bioimaging.

The fluorescent probe L, based on naphthalimide-modified coumarin, was designed, synthesized, and characterized, which could recognize Cu2+ from other cations selectively and sensitively in HEPES buffer (10 mM, Ph = 7. 4)/CH3CN (1:4, V/V). When the probe L interacted with Cu2+, the color and the fluorescent intensity changed obviously and it provided the naked-eye detection for Cu2+. The recognition mode between them was achieved by Job's plot, IR, MS, SEM, and 1HNMR. In addition, test strips made from L could still interact with Cu2+ in tap water effectively. The limit of detection (LOD) of L was 3.5 × 10−6 M. Additionally, the density functional theory (DFT) calculation method was used to analyze the action mechanism of L toward Cu2+. Importantly, the fluorescent probe L could demonstrate favorable selectivity toward Cu2+ in Caenorhabditis elegans. Thus, L was considered to have some potential for application in bioimaging.

The novel HOCl fluorescent probe CAN induced A549 apoptosis by inhibiting chlorination activity of MPO

Hypochlorous acid (HOCl) is an important signaling molecule for cell survival. However, it has been reported that excessive HOCl contributes to a variety of diseases such as cancers. And in cancer cells, the level of HOCl is much higher than that in normal cells. Here a coumarin-based fluorescent probe 7-Diethylamino-3-(2,3-dihydro-1H-perimidin-2-yl)-chromen-2-one (CAN) was successfully developed for HOCl detection. The probe could be oxidized by HOCl to induce significant change in its fluorescence profile, which made it feasible for ratiometric detecting HOCl. CAN (below 1 µM) did not affect cell viability and had good capacity in ratiometric detection of HOCl in RAW 264.7 cells. CAN induced A549 apoptosis and inhibited tumor growth in vitro and in vivo. And CAN could decrease the chlorination activity of myeloperoxidase (MPO) in A549. These findings suggested that CAN (below 1 µM) would develop into a HOCl probe. High activity of MPO and level of HOCl might be helpful for A549 survival. A549 could be induced apoptosis by reducing the HOCl level by CAN. It implies a new anticancer strategy by targeting HOCl.

Design and applications of a novel fluorescent probe for detecting glutathione in biological samples

This study aimed to develop a novel and practical fluorescent method for GSH detection in complex biological samples. To this end, a series of coumarin-based fluorescent probes was designed and synthesized using various aliphatic halogens as the sensing group. By using a new evaluation method of GSH/Cys/Hcy coexisting conditions, the probe with chloropropionate (CBF3) showed a high selectivity, excellent sensitivity, good stability for GSH detection. The reaction mechanism is proposed as nucleophilic substitution/cyclization and intramolecular charge transfer (ICT), which was confirmed by LC-MS and NMR analysis, as well as density functional theory calculations. In addition, CBF3 was demonstrated to be competent not only for the quantitative detection of GSH in real serum samples, but also for sensing GSH changes in different oxidative stress models in living cells and nematodes. This study showed a practical strategy for constructing GSH-specific fluorescent probes, and provided a sensitive tool for real-time sensing of GSH in real biological samples. The findings would greatly facilitate further investigations on GSH-associated clinical diagnosis and biomedical studies.

A coumarin-fused 'off-on' fluorescent probe for highly selective detection of hydrazine.

Hydrazine is a kind of widely used industrial raw material and a toxic biochemical reagent. Due to its toxic to organisms, hydrazine has been classified to be a hazardous environmental pollutant. It is urgent to develop fluorescent probe tools for selective sensitivity detection of hydrazine in the environment and the body. We developed here a new coumarin-based fluorescent probe for hydrazine detection. The probe can selectively detect hydrazine over other environmental and endogenous interfering analytes with a large off-on fluorescence response. The detection limit is 8.55ppb, which is well below the allowed threshold limit value. The sensing mechanism is hydrazine-induced pyrazole ring formation, which is confirmed by HRMS and DFT calculation methods. Additionally, the probe could also be applied for hydrazine imaging in living HeLa cells.