Dual-emission Fluorescent Probe Research Articles

A dual-emission fluorescent probe for simultaneous detection of singlet oxygen and hypochlorous acid in lipid droplets

Singlet oxygen (1O2) and hypochlorite (ClO-) are two important reactive oxygen species. They coexist in living systems and can be interconverted in organisms, being involved in a variety of pathophysiological processes. Lipid droplets (LDs) are organelles that transport and store lipids, and 1O2 and ClO- tend to destroy unsaturated lipids, leading to lipid oxidation and causing a range of diseases. Here we proposed the first dual-response fluorescent probe DBCC that can simultaneously distinguish 1O2 and ClO- within LDs. The probe is almost non-fluorescent, while significant fluorescence enhancement can be observed in the blue and green channels after treatment with 1O2 and ClO-, respectively. With the excellent properties of high sensitivity, good selectivity and wide tolerance range, the probe DBCC has been successfully used to detect 1O2 and ClO- in HepG2 cells and zebrafish, and faultlessly realized endogenous and exogenous 1O2 and ClO- imaging in LDs. This work provides a powerful analytical tool for further investigating the levels of 1O2 and ClO- in LDs and associated diseases.

Ratiometric fluoroprobe based on Eu-MOF@Tb3+ for detecting tetracycline hydrochloride in freshwater fish and its application in rapid visual detection

Tetracycline hydrochloride (TCH), a prevalent antibiotic in aquaculture for treating bacterial infections, poses challenges for on-site detection. This study employed the reversed-phase microemulsion method to synthesize a uniform nano metal-organic framework (MOF) material, europium-benzene-p-dicarboxylic acid (Eu-BDC), doped with Tb3+ to form a dual-emission fluorescence probe. By leveraging the combined a-photoinduced electron-transfer (a-PET) and inner filter effect (IFE) mechanisms, high-sensitivity TCH detection in Carassius auratus and Ruditapes philippinarum was achieved. The detection range for TCH is 0.380–75 μM, with a low limit of detection (LOD) at 0.115 μM. Upon TCH binding, Eu-BDC fluorescence rapidly decreased, while Tb3+ fluorescence remained constant, establishing a ratiometric fluorescence change. Investigation into the TCH quenching mechanism on Eu-BDC was conducted using time-dependent density functional theory (TD-DFT) calculations and fluorescence quenching kinetic equations, suggesting a mixed quenching mechanism. Furthermore, a novel photoelectric conversion fluorescence detection device (FL-2) was developed and evaluated in conjunction with high-performance liquid chromatography-diode-array detection (HPLC-DAD). This is the first dedicated fluorescence device for TCH detection, showcasing superior photoelectric conversion performance and stability that reduces experimental errors associated with smartphone photography methods, presenting a promising avenue for on-site rapid TCH detection.

Rational design of a near-infrared dual-emission fluorescent probe for ratiometric imaging of glutathione in cells.

Sensors for which the output signal is an intensity change for a single-emission peak are easily disturbed by many factors, such as the stability of the instrument, intensity of the excitation light, and biological background. However, for ratiometric fluorescence sensors, the output signal is a change in the intensity ratio of two or more emission peaks. The fluorescence intensity of these emission peaks is similarly affected by external factors; thus, these sensors have the ability to self-correct, which can greatly improve the accuracy and reliability of the detection results. To accurately image glutathione (GSH) in cells, gold nanoclusters (AuNCs) with intrinsic double emission at wavelengths of 606nm and 794nm were synthesized from chloroauric acid. With the emission peak at 606nm as the recognition signal and the emission peak at 794nm as the reference signal, a near-infrared dual-emission ratio fluorescence sensing platform was constructed to accurately detect changes in the GSH concentration in cells. In vitro and in vivo analyses showed that the ratiometric fluorescent probe specifically detects GSH and enables ultrasensitive imaging, providing a new platform for the accurate detection of active small molecules.

Paper-based ratiometric fluorescent sensing platform based on mixed quantum dots for the detection of glucose in urine.

A paper-based ratiometric fluorescent sensing platform has been developed for glucose detection based on a dual-emission fluorescent probe consisting of carbon quantum dots (C QDs) and CdTe QDs. When the two kinds of QDs are mixed, the fluorescence of C QDs is reversibly quenched by CdTe QDs. However, in the presence of glucose, the fluorescence of CdTe QDs is quenched by H2O2 catalyzed by glucose oxidase (GOx), which restores the fluorescence of C QDs. The proposed paper-based ratiometric fluorescent sensing platform exhibited good sensitivity and selectivity towards glucose. The working linear range was 0.1 mM to 50 mM with a limit of detection (LOD) of 0.026 mM. Additionally, the proposed paper-based sensor possesses viability for the determination of glucose in actual urine samples.

A dual-emission turn-on fluorescent probe for specific detecting Cys/Hcy from GSH through thiol-chromene click reaction

A dual-emission fluorescent probe was developed for detecting biothiols, a coumarin-chromene scaffold. In this work, the sensing mechanism of probe BDU towards biothiols was through two different pathways. For Hcy and Cys, it went through a cascade reaction followed by an isomerization, which formed a salicylic carbonate structure and coumarin substance. While for GSH, only the nucleophilic reaction was carried out without further isomerization. The probe exhibits selectivity for Hcy/Cys (Em = 470 nm) and GSH (Em = 546 nm) in PBS buffer containing 0.5 % DMSO. Besides, this probe could effectively sense biothiols in vitro and in vivo with low detecting limits, fast responses, good biocompatibility, and low toxicity. With all these excellent properties, this probe exhibits great potential value for applications in biological study.

Synthesis of a dual-emission fluorescent probe using graphitic carbon nitride as a carrier for the rapid detection of mesosulfuron-methyl

Pesticides play an irreplaceable role in ensuring increased food production and income, but the overuse of pesticides can also pose a threat to food and environmental safety. A novel dual-emission fluorescent probe was developed for the facile and accurate detection of sulfonylurea herbicides. A Förster resonance energy transfer system, based on N-doped carbon dots (N-CDs) and thioglycolic acid-capped cadmium telluride quantum dots (TGA-CdTe QDs) as energy donor–acceptor pairs, was established using graphitic carbon nitride (g-C3N4) as a substrate and successfully applied for the micro-detection of mesosulfuron-methyl (Mes). The CDs-CdTe/C3N4 probe exhibits emission peaks at 445 and 593 nm with strong fluorescence intensity under single-wavelength excitation. Mes was shown to significantly decrease the fluorescence intensity of each emission peak via different quenching mechanisms, and the degree of quenching was proportional to Mes concentration. The linear range of fluorescence measurement was 0–90 µM, with limits of detection at 1.3 µM (445 nm) and 0.8 µM (593 nm). The dual-emission fluorescent probe exhibited excellent selectivity for Mes compared with the other eleven herbicides. The fluorescent probe has a satisfying detection performance in environmental water samples and wheat samples, and has potential application in the portable detection of pesticide residues.

Double-emitting lanthanide metal–organic frameworks composed of Eu/Tb doping and ratiometric fluorescence detection of nitrofurazone

Lanthanide metal–organic frameworks (LnMOFs) have substantial potential in luminescence due to their unique antenna effect. Nevertheless, the single emission is susceptible to pseudo-signals caused by external environmental conditions, which significantly threaten the accurate measurement of the concentration. In this case, we prepared a dual-emission fluorescent probe {EuxTb1-x(NH2-BDC)3(DMF)4·2DMF}∞ (NH2-BDC = Diaminoterephthalic acid, DMF = N,N-dimethylformamide). The stable dual-emission signal provides a superior signal output for detecting nitrofurazone (NFZ), which is detected by the probe with excellent fluorescence for 0–10 μM NFZ. In the investigation of the detection mechanism, it is speculated that NFZ incorporates with probe to generate a novel complex. Furthermore, The UV absorption curves of the novel complexes and NFZ overlap extensively with those of the probe. The addition of NFZ attenuates the characteristic luminescence of Eu and Tb by competing for the absorption of the excitation light of the probe. The probe has exhibits rapid response, excellent sensitivity, visual detection and a meagre detection limit (LOD = 0.013 μM) for the detection of NFZ. This work not only broadens the application of LnMOFs in the field of ratiometric detection but also provides a favorable fluorescent probe for the quantitative detection of NFZ.

A promising tool for clinical diagnostics: Dual-emissive carbonized polymer dots based cross-linking enhanced emission for sensitive detection of alkaline phosphatase and butyrylcholinesterase

Compared with single signal readout, dual-signal readout commendably corrects the impact of systematic or background error, achieving more accurate results for the diagnosis of many diseases. This work aimed to design and prepare dual-emissive fluorescent probes for the construction of ratiometric fluorescence biosensors to detect liver disease biomarkers. Sodium alginate (SA) with numerous potential sub-fluorophores and active sites and 4,4′,4′′,4′′′-(porphine-5,10,15,20-tetrayl) tetrakis (benzoic acid) (TCPP) with macrocyclic conjugated structures were introduced to prepare the carbonized polymer dots (CPDs) with red/blue dual emission based on the cross-linking enhanced emission (CEE) effect and the luminescence of macrocyclic conjugated structures. The ratiometric fluorescence sensing systems were constructed by integrating the specific response of CPDs to Cu2+ and the affinity difference of Cu2+ to substrates or products of enzymes. The sensing systems, CPDs/Cu2+/PPi and CPDs/Cu2+/BTCh, were designed to detect liver disease biomarkers, alkaline phosphatase (ALP) and butyrylcholinesterase (BChE), respectively. The limit of detection for ALP and BChE was 0.35 U/L and 0.19 U/L, respectively. The proposed sensors were successfully applied to human serum samples from different health stages with satisfactory recoveries. These results demonstrate the successful design of a novel dual-emissive fluorescent probe and provide a feasible strategy for clinical detection.

Novel dual-emission sulfur quantum dot sensing platform for quantitative monitoring of pesticide 2,4-dichlorophenoxyacetic acid

In this work, a novel environment-friendly dual-emission Rhodamine B modified sulfur quantum dots (RhB-SQDs) sensing platform was established to economically monitor organochlorine pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) through regulating the activity of alkaline phosphatase (ALP). This dual emission RhB-SQDs exhibited excellent fluorescence and high photostability with emission wavelengths of 455 nm and 580 nm. ALP catalyzed the hydrolysis of the substrate p-nitrophenyl phosphate to p-nitrophenol, which quenched RhB-SQDs fluorescence at 455 nm due to the internal filtration effect, but had no effect the fluorescence intensity of RhB-SQDs at 580 nm. When 2,4-D was present, the activity of ALP was specifically inhibited and enzymatic reaction was interrupted, leading to the reduction of p-nitrophenol production, so the fluorescence of RhB-SQDs at 455 nm was restored. It demonstrated a good linear relationship between the concentration of 2,4-D and F455/F580 in the range of 0.050–0.500 μg mL−1, with a detection limit of 17.3 ng mL−1. The dual-emission fluorescent probe was successfully realized in the identification of 2,4-D in natural water samples and vegetables with the advantages of exceptional accuracy, immunity to interference, and selectivity. The platform offers a fresh look at pesticide monitoring and has the potential to prevent pesticide-related health issues.

Construction of ratiometric fluorescence determination of ethylene thiourea in foods based on the nanocomposite combining with sulfur quantum dots and gold clusters

A nanocomposite-based dual-emission fluorescent probe was constructed to detect ethylene thioureas (ETU). The nanocomposite SQDs@GSH-AuNCs was formed by the combination of sulfur quantum dots (SQDs) and glutathione stabilized gold clusters (GSH-AuNCs). After the combination, the fluorescence intensities at 450 nm and 570 nm decreased due to the aggregation fluorescence quenching effect. However, the addition of ETU resulted in a partial recovery of fluorescence at 570 nm. A possible reason was the occurrence of a ligand reaction between the zero- and one-valence gold and ETU to form a complex, which weakened the aggregation fluorescence quenching effect. Under the optimal reaction conditions, the concentration of ETU in the range of 2.5 μM to 100 μM had a good linear relationship with the ratio of fluorescence intensity (I570/I450), and the detection limit was 2.08 μM. The experimental results showed that the method had high selectivity and sensitivity, and had a good recovery of ETU in agricultural products. In addition, the hydrolysis process of mancozeb (Mz) was simulated, and by the use of SQDs@GSH-AuNCs, the conditions for promoting and inhibiting the hydrolysis of Mz to produce ETU were analyzed and obtained, which provided an experimental basis for the storage of Mz and a new method for analyzing the hydrolysis process of Mz.

A dual-emission fluorescence probe for the detection of viscosity and hydrazine in environmental and biological samples

The microenvironments of biological systems are associated with the pathology of organisms. This study, aimed to construct a hemicyanine-based probe (1), which can respond to mitochondrial viscosity and hydrazine (N2H4), for imaging application in living cells and zebrafish. The probe showed no fluorescence due to the intramolecular rotation in the solution; however, it exhibited a strong emission at 730 nm when the molecules were restricted to a high-viscosity environment. The addition of N2H4 caused an elimination reaction of the N-substituted group in the pyridinium part and further broke the CC bond to produce a highly fluorescent hydrazone. Also, the probe could selectively and quantitatively detect N2H4 via the fluorescence enhancement at 510 nm in a concentration range of 0 μM–140μM, with the limit of detection being 0.0485 μM. This probe may be used to study diseases related to N2H4 and viscosity changes in biological systems. Furthermore, the analysis methods based on probe 1 for N2H4 detection in soil, water, and air samples were successfully established.

Dual-nanocluster of copper and silver as a ratiometric-based smartphone-assisted visual detection of biothiols

Ratiometric-based probes improve detection precision and accuracy by minimizing the influence of various experimental conditions. Here, we present a unique dual-emission fluorescence probe constructed by a dual-nanocluster. This sensing platform is composed of copper nanoclusters (CuNCs) as a reference signal and silver nanoclusters (AgNCs) as a response signal. Uracil was used as a capping agent to improve the stability of AgNCs by forming a complex with silver metal. Ratiometrically, the composite of copper/silver bimetallic nanoclusters (Cu@Ag NCs) was used to measure the amount of cysteine as a typical biothiol. The Cu@Ag NCs showed a reddish fluorescence that originated from AgNCs and CuNCs when excited by a UV lamp. Under UV illumination, the addition of cysteine caused a noticeable fluorescence color shift from red to blue. Due to the color tonality, a smartphone and the Color Grab app were used to analyze red, green, and blue (RGB) values from the images of the dual-nanocluster solutions before and after the addition of cysteine. A satisfactory linear correlation between the ratio of red to blue values as a function of cysteine concentration was established for the quantitative measurement of cysteine from 20 to 180 μM with a limit of detection of 7.0 μM. The proposed probe was applied to assay cysteine in human serum with satisfactory accuracy and precision.

A ratiometric fluorescent probe based on a dual-ligand lanthanide metal–organic framework (MOF) for sensitive detection of aluminium and fluoride ions in river and tap water

A dual-emission fluorescent probe towards Al3+and F−using a Ln-MOF material Eu-BDC-NH2/TDA is employed with exceptional sensitivity, high selectivity, low LOD, excellent anti-interference characteristics and direct visual observation.

Dual-emission fluorescent probe for discriminative sensing of biothiols

• A new dual-emission fluorescent probe ( RED-NBD ) was developed. • RED-NBD has high sensitivity and can discriminate Cys/Hcy from GSH. • Probe RED-NBD can operate under a single wavelength excitation. • RED-NBD can be used for differentiate imaging of Cys/Hcy and GSH in cells. Herein, a dual-emission fluorescent probe ( RED-NBD ) for discriminative detection of cysteine/homocysteine (Cys/Hcy) and glutathione (GSH) was reported. Probe RED-NBD was prepared by conjugating a new red-emissive fluorophore ( RED ) with nitrobenzofurazan moiety ( NBD ). Upon reacting with Cys/Hcy, RED-NBD can be cleaved into fluorophore RED and NBD-Cys/Hcy, which can display distinct red and green fluorescence under a single-wavelength excitation, respectively. While the reaction between RED-NBD with GSH generates the red-emissive NBD and nonfluorescent NBD-SH. Thus, the RED-NBD can differentiate Cys/Hcy from GSH and realize the sensitive detection of these biothiols with low detection limits. Additionally, RED-NBD has also been used for discriminative visualizing of Cys/Hcy and GSH in cells.

A Novel Dual-Emission Fluorescence Probe Based on CDs and Eu3+ Functionalized UiO-66-(COOH)2 Hybrid for Visual Monitoring of Cu2.

In this work, CDs@Eu-UiO-66(COOH)2 (denoted as CDs-F2), a fluorescent material made up of carbon dots (CDs) and a Eu3+ functionalized metal-organic framework, has been designed and prepared via a post-synthetic modification method. The synthesized CDs-F2 presents dual emissions at 410 nm and 615 nm, which can effectively avoid environmental interference. CDs-F2 exhibits outstanding selectivity, great sensitivity, and good anti-interference for ratiometric sensing Cu2+ in water. The linear range is 0-200 µM and the limit of detection is 0.409 µM. Interestingly, the CDs-F2's silicon plate achieves rapid and selective detection of Cu2+. The change in fluorescence color can be observed by the naked eye. These results reveal that the CDs-F2 hybrid can be employed as a simple, rapid, and sensitive fluorescent probe to detect Cu2+. Moreover, the possible sensing mechanism of this dual-emission fluorescent probe is discussed in detail.

A novel dicyanisophorone-based colorimetric and ratiometric fluorescent probe for the detection of hypochlorite in the environment and living cells

A novel dual emissive fluorescent probe SFQ was designed and synthesized by linking dicyanisophorone and thiophene aldehyde units to carbazole groups. The probe SFQ has high selectivity and sensitivity toward ClO−. Upon addition of ClO− to the solution of probe SFQ resulted in a noticeable color changed from orange to pink under natural light. Meanwhile, SFQ could make a ratiometric fluorescence response to ClO− at two different excitation wavelengths, with the change of color from orange-red fluorescence to cyan fluorescence under the 365 nm UV lamp. The detection limit was 1.4 × 10−7 mol/L under ratiometric conditions. The study on the reaction mechanism showed that when SFQ reacted with ClO−, the cyano group disappeared and the cyclic ketone SFQ-O came into being. Furthermore, probe SFQ was successfully used to monitor ClO− in HepG2 cells and detect ClO− in actual environmental water samples.

Carbon dots@Cu metal-organic frameworks hybrids for ratiometric fluorescent determination of pesticide thiophanate-methyl.

A dual-emission fluorescent (FL) probe was constructed by coordinating Cu2+ of copper metal-organic frameworks (Cu-MOFs) with - COO- group of carbon dots (CDs) for pesticide thiophanate-methyl (TM) determination. TM was recognized by organic ligands (H2BDC and H2BDC-NH2) of Cu-MOFs via π stacking. Due to the higher affinity of Cu2+ to TM than ligands and CDs, TM chelated with Cu2+ to form TM-Cu complex. Thus coordination of Cu-MOFs was damaged and the ligands were released resulting in the FL intensity increase of Cu-MOFs (F430). And also CDs were released from CDs@Cu-MOFs hybrids and electron transfer from CDs to CuMOFs was inhibited, leading to the FL intensity increase of CDs (F600). The FL intensity ratio (F430/F600) showed a good linear relationship with TM concentrations of 0.0307-0.769μmol L-1 with a limit of detection (LOD) of ~ 3.67nmol L-1. The probe was successfully applied to detect TM in spiked food samples with satisfactory recoveries of 93.1-113%. Additionally, visual detection of TM was achieved according to the fluorescence color variation from blue to carmine, indicating promising application of CDs@Cu-MOFs probe.

A “bottle-around-ship” method to encapsulated carbon nitride and CdTe quantum dots in ZIF-8 as the dual emission fluorescent probe for detection of mercury (II) ion

A facile and efficient "bottle-around-ship" approach for preparing the ratiometric fluorescent probe has been developed by encapsulating the red-colored fluorescence CdTe quantum dots (QDs) and blue-colored fluorescence graphitic carbon nitride quantum dots (g-CNQDs) into the zeolitic imidazolate metal-organic frameworks (ZIF-8) in one step. At a single excitation of 360nm, the obtained probe ZIF-8@g-CNQD/CdTe shows the dual-emission peaked at 450 and 633nm, respectively. The red emission of CdTe QDs is selectively quenched by the Hg2+, whereas the blue fluorescence of g-CNQDs as an internal reference is insensitive, resulting in an apparent color transformation from pink to blue for special recognition of Hg2+. By this approach, the relative fluorescence intensity ratio (F633/F450) decreased linearly with increasing Hg2+ concentration in the 0.2-3.5μM range with a low limit of detection (LOD) of ~ 46nM. Therefore, we demonstrate that this "bottle-around-ship" process provides a new strategy for the construction of ratiometric fluorescent Hg2+ probes with good simplicity, high efficiency, and excellent stabilities. Moreover, the obtained Hg2+ fluorescent probe shows good results in the detection of actual samples.

A highly water-stable dual-emission fluorescent probe based on Eu3+-loaded MOF for the simultaneous detection and quantification of Fe3+ and Al3+ in swine wastewater

A novel dual-emissive Eu3+-loaded metal–organic framework (MOF) is designed and successfully fabricated by introducing 2-hydroxyterephthalic acid (H2BDC-OH) and Eu3+ ions into an UiO-66-type MOF material. The obtained MOF, here referred to as EuUCH, exhibits dual emission at 450 and 614 nm, and both emissions are quite stable in aqueous media in the pH range of 4–11. EuUCH is characterized by a high selectivity and sensitivity toward Fe3+ and Al3+, which yield different responsive modes. The two emissions of EuUCH are quenched by Fe3+; by contrast, only the emission at 450 nm is quenched by Al3+ showing a ratiometric fluorescence signal. More importantly, as there is no clear interference between the signals of Fe3+ and Al3+, EuUCH is successfully utilized for the simultaneous detection of Fe3+ and Al3+ in their mixtures. In addition, the simultaneous quantification of Fe3+ and Al3+ is achieved in more complicated swine wastewater with good recoveries. This work provides a water-stable dual-emissive probe and the possibility to achieve the simultaneous quantification of Fe3+ and Al3+ in complicated environment wastewater.

A dual-emission fluorescent ratiometric probe based on bimetallic lanthanide complex interacted in nanoclay for monitoring of food spoilage

Owing to increasing food-safety issues, food insecurity is an enormous threat to human health and the economy. Therefore, it is necessary to explore efficient and early food spoilage detection. Herein, we develop a ratiometric fluorescent probe based on the embedding of bimetallic Ln3+ (Eu3+ and Tb3+) complex intercalated in nanoclay, which can monitor the real-time visual surveillance freshness of food. The fluorescent probe exhibits a dual-emission responsive to biogenic amine along with a significant decrease in Tb3+ emission intensity and an increase in Eu3+ emission intensity, enabling an obviously distinguishable color transition from yellow to orange to rose red clearly discerned by naked eyes. The probe shows an outstanding response and excellent sensitivity which has a low limit of detection (LOD=0.137 mg L−1) for target biogenic amines (histamine) in the range (4–22 mg L−1). Besides, we use the gel to inspect the change in the freshness of raw fish in a hermetic space. It is proved that the nanocomposite can be applied to the on-site inspection of the food freshness. This work provides a novel direction for the evolution of fluorescent nano-clay based lanthanide complexes as a new platform for application in food surveillance.