Ratiometric Fluorescent Probe Research Articles

Dual-emission Tb-based coordination polymer as a ratiometric fluorescence probe for the detection of phosphate.

A simple, sensitive dual-emission probe was developed for the detection of phosphate (Pi). The probe Tb-BTB/DPA was synthesized by mixing dual-ligand, 1,3,5-tri(4-carboxyphenyl) benzene (H3BTB) and dipicolinic acid (DPA), with metal ions Tb3+ in ethanol-water solution at 40℃ for 2h. Tb-BTB/DPA exhibits two emission peaks, the emission at 362nm is attributed to H3BTB, an energy transfer between Tb3+ nodes, and DPA further enhances the fluorescence of Tb3+ at 544nm. Pi competes with ligand H3BTB to coordinate Tb3+, resulting in partial collapse of the Tb-BTB/DPA structure and interrupting the electron transfer between H3BTB and Tb3+. Therefore, the emission at 362nm is enhanced, while the emission at 544nm is unchanged, and a ratiometric fluorescence method is developed to detect Pi. Tb-BTB/DPA exhibits good linearity within the Pi concentration range (0.1-50µmol/L), and the detection limit was 25.8nmol/L. This study provides a new way to prepare probes with dual emission sensing properties.

Zn-CD@Eu Ratiometric Fluorescent Probe for the Detection of Dipicolinic Acid, Uric Acid, and Ex Vivo Uric Acid Imaging.

Development of reliable methods for the detection of potential biomarkers is of the utmost importance for an early diagnosis of critical diseases and disorders. In this study, a novel lanthanide-functionalized carbon dot-based fluorescent probe Zn-CD@Eu is reported for the ratiometric detection of dipicolinic acid (DPA) and uric acid (UA). The Zn-CD@Eu nanoprobe was obtained from a simple room-temperature reaction of zinc-doped carbon dots (Zn-CD) and the EDTA-Eu lanthanide complex. Under optimal conditions, a good linear response was obtained for DPA in two concentration ranges of 0-55 and 55-100 μM with a limit of detection of 0.53 and 2.2 μM respectively, which is significantly below the infectious dosage of anthrax (∼55 μM). Furthermore, the Zn-CD@Eu/DPA system was employed for the detection of UA with a detection limit of 0.36 μM in the linear range of 0-100 μM. The fluorescent probe was successfully implemented for determining DPA and UA in human blood serum, sweat, and natural water bodies with considerable recovery rates. In addition, the potential of the nanoprobe for ex vivo visualization of UA was demonstrated in fruit fly (Drosophila melanogaster) as a model organism.

Nitrogen and Chlorine Co-Doped Carbon Dots with Yellow-Green Emission as a Ratiometric Fluorescent and Colorimetric Dual-Signal Probe for Quercetin Detection and Cell Imaging

Despite the emergence of numerous carbon dots (CDs)-based sensors, most of them are fluorescent probes. To improve the reliability of the results, using ratiometric fluorescence/UV-vis absorption dual-signal probes is an effective method. Herein, nitrogen and chlorine co-doped carbon dots (N, Cl-CDs) with yellow-green fluorescence were prepared and used as a dual-function probe for ratiometric fluorescence/UV-vis. The detection range of the fluorescence method was 0.05–78[Formula: see text][Formula: see text]M, and the limit of detection (LOD) was 1.2[Formula: see text]nM (3[Formula: see text]/s). For the colorimetric method, the linear range was 0.05–186[Formula: see text][Formula: see text]M with LOD of 10.7[Formula: see text]nM. Importantly, the N, Cl-CDs were successfully used to detect Quercetin (QT) in actual water samples. Besides, due to their good biocompatibility, the N, Cl-CDs were applied to in vivo biological imaging of oocysts and shown the potential for environmental survey and biological assay.

Dual-ligand lanthanide metal-organic framework based ratiometric fluorescent platform for visual monitoring of aminoglycoside residues in food samples

Herein, a dual-emission Eu metal-organic framework (Eu-MOF) is prepared and used as the ratiometric fluorescence probe for ultrasensitive detection of aminoglycoside antibiotics (AGs). Due to the strong hydrogen bond interactions between AGs and Eu-MOF, the blue emission is enhanced while the red emission has little fluctuation in Eu-MOF with the addition of AGs, thus a good linear relationship with the logarithm of AGs concentrations from 0.001 to 100 μg/mL can be established for quantitative analysis. Good sensitivity with the detection limit of 0.33 ng/mL for apramycin, 0.32 ng/mL for amikacin and 0.30 ng/mL for kanamycin is achieved. The proposed assay demonstrates good selectivity and applicability for determination of AGs in real milk and honey samples. The Eu-MOF materials are further fabricated as fluorescent test papers for facile visual detection. The as-established ratio fluorescence platform offers a portable and economical way for rapid monitoring AGs residues in complex food samples.

Coumarin-hemicyanine-based ratiometric fluorescent probes for detection of strong acidity

Fluorescent probes for determination of strongly acidic pH values are urgently needed, especially the ones with ratiometric signal changes. Here, two fluorescent probes (CP and CyC) based on coumarin-hemicyanine were synthesized. Both probes emitted red fluorescence under weakly acidic to weakly alkaline conditions, whereas blue fluorescence under strongly acidic conditions. Notably, probe CP displayed good stability, water solubility, anti-interference ability, repeated utilization and instant response. Encouraged by the good performance, probe CP based test strips were used to indicate the pH of aqueous solutions, and to detect HCl or NH3 vapor in air reversibly.

A mitochondrial targeted dual ratiometric near-infrared fluorescent probe based on ICT effect for the detection of SO2 derivative and its bioimaging

SO2 derivatives play an important role in many metabolic processes, excessive ingestion of them can lead to serious complications of various diseases. In this work, a novel dual ratiometric NIR fluorescent probe XT-CHO based on ICT effect was synthesized for detecting SO2 derivative. In the design of the probe, the α, β-unsaturated bond formed between benzopyran and coumarin was used as the reaction site for SO2, meanwhile, the extended π-conjugate system promoted maximum emission wavelength of the probe up to 708 nm. Notably, the probe exhibited high selectivity and sensitivity for detecting SO2, the limit of detection reached 2.13 nM and 58.5 nM in fluorescence spectra and UV–Vis absorption spectra, respectively. The reaction mechanism of SO2 and XT-CHO had been verified by 1H NMR, ESI-MS spectra and DFT calculation. Moreover, the probe was successfully applied in detecting endogenous and exogenous SO2 in living cells and proved possessed the mitochondrial targeted ability.

A new oligo(N,O-donor)-like ratiometric fluorescent probe with FRET effect for dual-channel recognition of B4O72- ions in practical water samples

B4O72- ions are widely found in various production and living environments, and can cause serious effects on human health. For this reason, it is necessary to develop a high-efficiency method for the detection of B4O72- ions. Here a oligo(N,O-donor)-like dual-channel ratiometric fluorescence probe H3L was designed and synthesized for the detection of B4O72- ions in environmental samples. The recognition of B4O72- is based on the FRET effect by the probe H3L, the naphthalene ring partially serves as an energy donor, benzene ring partially serves as an energy acceptor, and phenolic oxygen acts as a reaction site for B4O72-. The probe H3L mainly displays the blue fluorescence of the donor; the presence of the B4O72- ions turns on the FRET effect, which will lead to yellow fluorescence of the benzene ring acceptor, enabling a ratiometric fluorescence recognition process. The probe has a large Stokes red shift (Δλ = 123 nm), which makes the emission wavelength after red shift more than 500 nm, and the obvious colourless to yellow color change can be observed by naked eyes, which solves the background fluorescence interference problem of short-wavelength fluorescence probe. At the same time, the probe has high selectivity and high sensitivity (low detection limit of 17.3 nM). In addition, we have successfully used this probe to detect B4O72- ions in actual samples. These results showed that the probe has a broad application prospect.

A ratiometric fluorescent probe with dual-targeting capability for heat shock imaging

HSO3− is an important reactive sulfur species that maintains the normal physiological activities of living organisms and participates in a variety of redox homeostatic processes. It has been found that changes in HSO3− levels is closely related to the heat stroke phenomenon of the organism. Heat stroke causes damage to normal cells, which in turn causes damage to the body and even death. It is crucial to accurately monitor and track the physiological behavior of HSO3− during heat stroke. Herein, a ratiometric multifunctional fluorescent probe DRM-SO2 with dual-targeting ability to rapidly and precisely recognize HSO3− being constructed based on the FRET mechanism. DRM-SO2 has extra Large Stokes shift (216 nm), very high sensitivity (DL = 12.2 nM), fast response time and good specificity. When DRM-SO2 undergoes Michael addition with HSO3−, the fluorescence emission peak was blue-shifted from 616 nm to 472 nm, and a clear ratiometric signal appeared. The interaction between lysosomes and mitochondria in maintaining cellular homeostasis was investigated by the dual-targeting ability of the probe using HSO3− as a mediator. DRM-SO2 achieved successful targeting and real-time monitoring of exogenous and endogenous HSO3− in the cells. More importantly, imaging experiments in heat stroke mice revealed high HSO3− expression in intestinal tissues. This provides new ideas and research tools for early prevention of heat stroke-induced diseases such as intestinal injuries. In addition, the semi-quantitative monitoring experiments for paper-based visualization of HSO3− make the probe promising for the design of portable detectors.

Ratiometric Sensing of Azithromycin and Sulfide Using Dual Emissive Carbon Dots: A Turn On-Off-On Approach.

A novel ratiometric fluorescence probe was developed for the determination of azithromycin (AZM) and sulfide ions based on the differential modulation of red emissive carbon dots (R-N@CDs) and blue emissive carbon dots (B-NS@CDs). The addition of sulfide anion selectively quenched the red emission of R-N@CDs while the blue emission of B-NS@CDs unaffected. Upon subsequent introduction of AZM to this R-N@CDs@sulfide system, the quenched red fluorescence was restored. Comprehensive characterization of the CDs was performed using UV-Vis, fluorescence, FTIR spectroscopy, XPS, and TEM. The proposed method exhibited excellent sensitivity and selectivity, with limits of detection of 0.33 µM for AZM and 0.21 µM for sulfide. Notably, this approach enabled direct detection of sulfide without requiring prior modulation of the CDs with metal ions, as is common in other reported methods. The ratiometric probe was successfully applied for the determination of AZM in biological fluids and sulfide in environmental water samples with high selectivity. This work presents the first fluorometric method for the detection of AZM in biological fluids.

An Experimental and Theoretical Study on Mechanistic Insights into Urolithin-Based Ratiometric Fluorescent Probe for Instant Quantitative Detection of Fluoride Ions

Fluoride detection has been playing an important role in chemical, biological, and medicinal field, especially for keeping physical health and resisting environmental pollution. Herein, a urolithin B fluorescent probe has been successfully developed with good sensitivity, selectivity, anti-interference ability. The low limit of detection (LOD) refers to 0.156 μM, and the instant response time to F- is less than 1 second. The probe is suitable for quantitatively and qualitatively ratiometric detection for F- in solution with two distinct emission bands at 425 (blue) and 566 nm (orange), with the coordinate change of CIE from (0.38, 0.41) to (0.22, 0.11). Urolithin B displayed a remarkable ratiometric fluorescence response towards F-. The detection mechanistic was further proposed by NMR and electronic spectroscopic experiments combining with time-dependent density functional theoretical calculation.

Synthesis and fluorescence properties of a two-dimensional Cd-complex for the ratiometric fluorescence detection of Zn2+ ions

The two-dimensional complex [Cd3(L)(2,2′-bpy)2]n (1) was synthesized solvothermally from 4,5-di(3,5-dicarboxylphenoxy)phthalic acid (H6L) and 2,2′-bipyridine (2,2′-bpy) and fully characterized by elemental analysis, infrared spectroscopy, single crystal and powder X-ray diffraction. Complex 1 displays high stability in water and resistance towards acidic and basic media. Fluorescence studies revealed that it may be acted as a ratiometric fluorescence probe to detect Zn2+ ions in water with a superior detection limit of 3.48 nM. The fluorescence recognition mechanism stems from weak interactions between Zn2+ ions and complex 1. Its pronounced stability and recyclability suggest that the new material may be used for high-precision detection of Zn2+ ions in real-life aqueous samples, even under acidic and basic conditions.

Development of a ratiometric fluorescent probe for the detection of peroxynitrite

Peroxynitrite is one of the important reactive oxygen species in the human body and is closely related to the physiological and pathological processes of many diseases. Therefore, the development of probes to detect peroxynitrite is important for diagnostic and pathologic studies of many diseases. In this work, a ratiometric probe was designed using benzopyran as the recognition site, and the sensitivity and selectivity of the probe were tuned by modification of substituents on benzopyran. Upon reaction with peroxynitrite, the color of the solution changes to the naked eye (from blue to yellow), and the fluorescence changes from red to blue. The probe SJ has the advantages of large Stokes shift (237 nm), fast response (≤10 s), wide linear range, good selectivity, low detection line (21.3 nm), and low cytotoxicity. Probe SJ has been successfully used for bioimaging of endogenous and exogenous peroxynitrite.

AIEE-active dichlorobenzene and chlorobenzene ratiometric fluorescent probe based on [2.2]paracyclophane

Two AIEE-active [2.2]paracyclophanyl-based diester and monoester (1a and 1b) were facilely synthesized by one-pot method and applied as ratiometric fluorescent probe to detect dichlorobenzene (DCB) and chlorobenzene (CB). Compared with compound 1b, 1a exhibits high sensitivity and low detection limits for DCB and CB in dichloromethane (DCM), particularly, the detection sensitivities for ortho-dichlorobenzene (o-DCB), meta-dichlorobenzene (m-DCB) and chlorobenzene can be modulated by AIEE behavior with lower detection limits of 23.64, 56.27, and 5.92 ppm, respectively in THF/H2O mixed solutions with water fraction (fw) of 70 % due to the formation of aggregation-state. The X-ray structure analysis, theoretical calculations and photophysical properties in different solvents were investigated to reveal the distinctive photophysical behaviors of 1a and 1b. The facile synthesis, X-ray structure, AIEE modulated sensing properties for o-DCB, m-DCB, and CB in DCM and THF/H2O mixed solutions make 1a potential application as fluorescent probe for trace DCB and CB detection in drinking water.

Quantitative detection of L-cysteine with a ratiometric probe combined with smartphone imaging and fluorescent test strips

Cysteine is an important thiol involved in the vital activities of the human body, and many physiological processes in the body are associated with it. Accurate detection of cysteine is of great importance in monitoring the development of diseases. In this paper, we prepared a ratiometric flavonoid fluorescent probe, HDFA, that exhibits specific selectivity for L-cysteine. HDFA was the first fluorescent probe that can distinguish between L-cysteine and D-cysteine. When detecting L-cysteine, the fluorescence color changed from blue to yellow, and the fluorescence quantum yield increased from 16.96 % to 21.30 %. The probe has a short response time (90 s) to L-cysteine, a large Stokes shift (186 nm), good selectivity, and anti-interference, and the detection limit was 0.32 μM. The detection mechanism was confirmed by mass spectrometry. In addition, HDFA has good applications in cell imaging, smartphone fluorescence imaging and fluorescence test strip detection.

Lanthanide metal-organic framework-based surface molecularly imprinted polymers ratiometric fluorescence probe for visual detection of perfluorooctanoic acid with a smartphone-assisted portable device

Perfluorooctanoic acid (PFOA) poses a threat to the environment and human health due to its persistence, bioaccumulation, and reproductive toxicity. Herein, a lanthanide metal-organic framework (Ln-MOF)-based surface molecularly imprinted polymers (SMIPs) ratiometric fluorescence probe (Eu/Tb-MOF@MIPs) and a smartphone-assisted portable device were developed for the detection of PFOA with high selectivity in real water samples. The integration of Eu/Tb MOFs as carriers not only had highly stable multiple emission signals but also prevented deformation of the imprinting cavity of MIPs. Meanwhile, the MIPs layer preserved the fluorescence of Ln-MOF and provided selective cavities for improved specificity. Molecular dynamics (MD) was employed to simulate the polymerization process of MIPs, revealing that the formation of multiple recognition sites was attributed to the establishment of hydrogen bonds between functional monomers and templates. The probe showed a good linear relationship with PFOA concentration in the range of 0.02–2.8 μM, by giving the limit of detection (LOD) of 0.98 nM. Additionally, The red-green-blue (RGB) values analysis based on the smartphone-assisted portable device demonstrated a linear relationship of 0.1–2.8 μM PFOA with the LOD of 3.26 nM. The developed probe and portable device sensing platform exhibit substantial potential for on-site detecting PFOA in practical applications and provide a reliable strategy for the intelligent identification of important targets in water environmental samples.

Hydrothermal route upcycling surgical masks into dual-emitting carbon dots as ratiometric fluorescent probe for Cr (VI) and corrosion inhibitor in saline solution

Exploration effective route to convert plastic waste into valuable carbon dots with bifunction of metal fluorescence monitoring and corrosion protection in seawater is promising. Herein, using “white-pollution” polypropylene surgical masks as a single precursor, dual-emitting carbon dots (CDs) with excellent ratiometric fluorescent sensitivity and corrosion inhibitor efficiency were fabricated with high yield (∼100 %) by a one-pot in situ acid oxidation hydrothermal strategy without post-treatment and organic solvents. Chemical, structural, morphological, optical properties and the Cr (VI) detection and Cu inhibition mechanism of the synthesized CDs had been systematically studied. Furthermore, a dual-response-OFF proportional fluorescent probe had been developed for the detection of the analyte Cr (VI) with a low detection limit of 24 nM. Additionally, the corrosion inhibition efficiency of the prepared CDs reached approximately 94.01 % for Cu substrate in 3.5 wt% NaCl electrolyte under a CDs concentration of 200 mg/L, which is higher than that of most previous reports.

A Phenanthrenequinone-Based Ratiometric Fluorescent Probe for Rapid Detection of Peroxynitrite with Imaging in Osteoblast Precursor Cells.

In the current situation, peroxynitrite (ONOO-) is drawing the increasing attention of researchers for its pivotal role in diverse pathological and physiological processes on grounds of robust oxidation and nitrification. Herein, we have successfully designed and synthesized a phenanthrenequinone benzyl borate-based chemosensor for fast and selective detection of ONOO-. The probe PTDP itself had an orange fluorescence, which was changed to strong blue fluorescence upon the addition of ONOO-, indicating the ratiometric response of the probe. This is so because of the cleavage of the benzyl boronate-protecting group of PTDP upon the addition of ONOO- with simultaneous releasing of pyridinyl-based chemosensor PPI. The PTDP showed outstanding performance in the various photophysical studies such as good selectivity, excellent sensitivity with a very low detection limit of 2.74 nM, and a very fast response time (<15 s). Furthermore, for practical applicability, it was successfully applied in the ratiometric detection of ONOO- in osteoblast precursor cells.

Real-Time Monitoring of Tyrosine Hydroxylase Activity with a Ratiometric Fluorescent Probe.

Parkinson's disease (PD) represents the second most widespread neurodegenerative disease, and early monitoring and diagnosis are urgent at present. Tyrosine hydroxylase (TH) is a key enzyme for producing dopamine, the levels of which can serve as an indicator for assessing the severity and progression of PD. This renders the specific detection and visualization of TH a strategically vital way to meet the above demands. However, a fluorescent probe for TH monitoring is still missing. Herein, three rationally designed wash-free ratiometric fluorescent probes were proposed. Among them, TH-1 exhibited ideal photophysical properties and specific dual-channel bioimaging of TH activity in SH-SY5Y nerve cells. Moreover, the probe allowed for in vivo imaging of TH activity in zebrafish brain and living striatal slices of mice. Overall, the ratiometric fluorescent probe TH-1 could serve as a potential tool for real-time monitoring of PD in complex biosystems.

Development of a polarity-sensitive ratiometric fluorescent probe based on the intramolecular reaction of spiro-oxazolidine and its applications for in situ visualizing the fluctuations of polarity during ER stress

Polarity is a vital element in endoplasmic reticulum (ER) microenvironment, and its variation is closely related to many physiological and pathological activities of ER, so it is necessary to trace fluctuations of polarity in ER. However, most of fluorescent probes for detecting polarity dependent on the changes of single emission, which could be affected by many factors and cause false signals. Ratiometric fluorescent probe with “built-in calibration” can effectively avoid detection errors. Here, we have designed a ratiometric fluorescent probe HM for monitoring the ER polarity based on the intramolecular reaction of spiro-oxazolidine. It forms ring open/closed isomers driven by polarity to afford ratiometric sensing. Probe HM have manifested its ratiometric responses to polarity in spectroscopic results, which could offer much more precise information for the changes of polarity in living cells with the internal built-in correction. It also showed large emission shift ( 133 nm), high selectivity and photo-stability. In biological imaging, HM could selectively accumulate in ER with high photo-stability. Importantly, HM has ability for in situ tracing the changes of ER polarity with ratiometric behavior during the ER stress process with the stimulation of tunicamycin, dithiothreitol and hypoxia, suggesting that HM is an effective molecule tool for monitoring the variations of ER polarity.

A novel core–shell lanthanide coordination polymer ratiometric fluorescent probe for the ultrasensitive and visual detection of anthrax biomarker

A novel core–shell based lanthanide ratiometric fluorescent probe is designed for the rapid and sensitive detection of 2, 6-pyridine dicarboxylic acid (DPA), which is the biomarker of Bacillus anthracis. The fluorescent dye molecule 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) was encapsulated in silica nanoparticles as a reference signal and externally connected with guanine mononucleotide europium coordination polymers (Eu/GMP) as a response signal so as to construct a double-emission fluorescent sensor. The visual detection was enabled by the fluorescence color change from green to red under an UV lamp with the addition of DPA. In addition, the RGB auxiliary detection platform was built using color scanning software of smartphone. This work presents a novel and efficient method for detecting anthrax biomarkers.