Fluorophore Group Research Articles

A novel pyridinium-based fluorescent probe for ratiometric detection of peroxynitrite in mitochondria.

Peroxynitrite (ONOO-) is a primary kind of reactive oxygen species. Excessive ONOO- can induce oxidative damage to biomolecules and further results in various diseases. So, quantitative monitoring ONOO- with excellent selectivity and sensitivity is imperative for elucidating its role in biological processes. In this study, a novel pyridinium fluorescent ONOO- probe (CPC) has been constructed base on ICT-modulated by combining coumarin fluorophore and diphenylphosphinate recognition group. The fluorescence response of CPC for ONOO- is realized via the removal of diphenylphosphinate group. The probe CPC shows prominent features for detection of ONOO- including fast response rate (within 3 min), excellent selectivity and sensitivity, distinct colorimetric (red to green), and a large emission wavelength shift (105 nm). The emission intensity ration (I538/I643) exhibits 153-fold enhancement along with the increasing ONOO- and the detection limit is as low as 1.60 × 10-8 M. These good response properties make CPC possible to quantitative detection of ONOO- concentration. By using the strategy, the ratiometric CPC has been employed to detection of mitochondrial ONOO- in live cell successfully.

Non-Typical Fluorescence Effects and Biological Activity in Selected 1,3,4-thiadiazole Derivatives: Spectroscopic and Theoretical Studies on Substituent, Molecular Aggregation, and pH Effects.

The below article presents the results of spectroscopic research, theoretical (time-dependent density functional theory (TD-DFT)), microbiological, and antioxidative calculations for three compounds from the group of 1,3,4-thiadiazoles: 2-amino-5-phenyl-1,3,4-thiadiazole (TB), 2-amino-5-(2-hydroxyphenyl)-1,3,4-thiadiazole (TS), 2-amino-5-(2-hydroxy-5-sulfobenzoyl)-1,3,4-thiadiazole (TSF). In the fluorescence emission spectra (TS) of solutions with varying concentrations of hydrogen ions, a particularly interesting effect of dual fluorescence was observed. The aforementioned effect was observed even more clearly in the environment of butan-1-ol, relative to the compound’s concentration. Depending on the modification of the resorcylic substituent (TS and TSF), we observed the emergence of two separate, partially overlapping, fluorescence emission spectra or a single emission spectrum. Interpretation of the obtained spectra using stationary and time-resolved spectroscopy allowed the correlation of the effect’s emergence with the phenomenon of molecular aggregation (of a particular type) as well as, above all, the structure of the substituent system. The overlap of said effects most likely induces the processes related to the phenomenon of charge transfer (in TS) and is responsible for the observed fluorescence effects. Also, the position of the –OH group (in the resorcylic ring) is significant and can facilitate the charge transfer (CT). The determinations of the changes in the dipole moment and TD-DFT calculations further corroborate the above assumption. The following paper presents the analysis (the first for this particular group of analogues) of the fluorescence effects relative to the changes in the structure of the resorcylic group combined with pH effects. The results of biological studies also indicate the highest pharmacological potential of the analogue in the case where the effects of dual fluorescence emission are observed, which predisposes this particular group of fluorophores as effective fluorescence probes or potential pharmaceuticals with antimycotic properties.

Analysis of fluorophores of organic substances dissolved in Suvani river water using reversed-phase liquid chromatography

Reversed-phase high-efficiency liquid chromatography was used in combination with detection by multiwave fluorescence for analysis of organic substances dissolved in natural water of the Suwannee River. Also analyzed were the stable electrophoretic fractions А, В, and C+D, obtained by a combination of preparative size-exclusion chromatography and analytical electrophoresis in a polyacrylamide gel. Fraction А has the largest molecular size, and fraction C+D, the smallest. Using 3D fluorescent analysis, humic-like fluorescence was detected both in the original sample and in all fractions; protein-like fluorescence is almost fully localized in fractions А and В of the largest and middle molecular sizes. The wide peak of humic-like fluorescence is split into several groups of fluorophores with different emissions maxima (435, 455, 460, and 465 nm) and degrees of hydrophobicity. The obtained results were analyzed in relation to contemporary theories of formation of humic-like fluorescence of dissolved organic substances. The low-molecular free aromatic amino acids tyrosine and tryptophan were identified in fractions А and В of the highest molecular size and constitute >50% of the protein-like fluorescence of the organic substances dissolved in the Suwannee River water. The data obtained ensure better understanding of the molecular nature of protein-like and humic-like fluorescence of organic substance dissolved in natural water.

An ultrasensitive fluorescence sensor for determination of trace levels of copper in blood samples.

A novel SBA-15-based fluorescent sensor, SBA-PI: mesoporous SBA-15 structure modified with iminostilbene groups, was designed, synthesized, and characterized by Fourier transform-infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), low-angle X-ray diffraction techniques (low-angle XRD), and N2 adsorption-desorption techniques. The SBA-PI as a sensor with a selective behavior for detection of Cu2+ comprises iminostilbene carbonyl as the fluorophore group. The SBA-PI sensor displays an excellent fluorescence response in aqueous solutions and the fluorescence intensity quenches remarkably upon addition of Cu2+. Other common interfering ions even at high concentration ratio showed either no or very small changes in the fluorescence intensity of SBA-PI in the absence of Cu2+. A limit of detection of 8.7 × 10-9M for Cu2+ indicated that this fluorescence sensor has a high sensitivity and selectivity toward the target copper (II) ion. The fabricated Cu2+ sensor was successfully applied for the determination of the Cu2+ in human blood samples without any significant interference. With the selective analysis of Cu2+ ions down to 0.9nM in blood, the sensor is a promising and a novel detection candidate for Cu2+ and can be applied in the clinical laboratory. A reversibility and accuracy in the fluorescence behavior of the sensor was found in the presence of I¯ that was described as a masking agent for Cu2+. Graphical abstract.

A near-infrared xanthene-based fluorescent probe for selective detection of hydrazine and its application in living cells

Developing fluorescent probes for selective determination of the toxic and carcinogenic hydrazine are pretty significant. Herein, a rhodamine dye coupled to naphthalene was selected as a near-infrared fluorophore and acetyl group as a trigger unit for hydrazine sensing with a Stokes shifts of 62 nm. The probe showed about 77-fold NIR fluorescence enhancement in the presence of hydrazine. In addition, the detection limit was as low as 3.4 ppb, and the fluorescence intensity at 654 nm showed a satisfactory linearity with the concentration range of hydrazine from 0 to 120 μM. More importantly, the practical utility of probe has been successfully proved through the fluorescence bioimaging of hydrazine in living cells with low cytotoxicity and quantitative N2H4 detection in environmental water samples.

Analysis of Fluorophores of Dissolved Organic Matter in the Suwannee River by Reversed-Phase Liquid Chromatography

Reversed-phase high performance liquid chromatography in combination with a multiwave fluorescence detector has been used to analyze the natural water of the Suwannee River for dissolved organic matter and its stable electrophoretic fractions A, B, and C + D, obtained by a combination of preparative exclusive chromatography with analytical electrophoresis in polyacrylamide gel. The fraction A had the largest molecular size, while that of the fraction C + D was the smallest. Three-dimensional fluorescent analysis revealed humic-like fluorescence both in the source preparation and in all fractions, while protein-like fluorescence was almost completely localized in fractions A and B with the largest and medium molecular size. A wide peak of humic-like fluorescence was found to split into several groups of fluorophores with different emission maximums (435, 455, 460, and 465 nm) and hydrophobic properties. The obtained results are discussed in the context of the modern theories describing the formation of humic-like fluorescence of dissolved organic matter. Identified in the fractions A and B of the largest molecular size were low-molecular free aromatic amino acids tyrosine and tryptophan, which account for >50% of the protein-like fluorescence of dissolved organic matter in Suwannee water. The obtained data contribute to the understanding of the molecular nature of protein-like and humic-like fluorescence of dissolved organic matter in natural water.

Characterization of Nile Red as a Tracer for Laser-Induced Fluorescence Spectroscopy of Gasoline and Kerosene and Their Mixture with Biofuels.

Suitable fluorescence tracers (“dyes”) are needed for the planar measurement of droplet sizes by using a combination of laser-induced fluorescence (LIF) and Mie scattering. Currently, no suitable tracers have been characterized for application in planar droplet sizing in gasoline and kerosene fuels, as well as biofuel blends. One promising tracer is nile red, which belongs to the fluorophore group. For its utilization for droplet size measurements, preliminary characterization of the fluorescence of the respective fuel tracer mixtures are mandatory. For this purpose, the fluorescence and absorption behavior of nile red dissolved in the surrogate fuels Toliso and Jet A-1 as well as in biofuel blends was investigated. The fluorescence signal for nile red that was dissolved in the two base fuels Toliso and Jet A-1 showed a linear behavior as a function of dye concentration. The temperature effect on spectral absorption and emission of nile red was investigated in a specially designed test cell. An ethanol admixture to Toliso led to a spectral shift towards higher wavelengths. The absorption and emission bands were shifted towards lower wavelengths with increasing temperature for all fuels. Both absorption and fluorescence decreased with increasing temperature for all fuels, except for E20, which showed an increased fluorescence signal with increasing temperature. Jet A-1 and its blends with hydroprocessed esters and fatty acids (HEFA) and farnesane did not exhibit explicit variations in spectral absorption or emission, but these blends showed a more distinct temperature dependence compared to the Toliso-ethanol-blends. The effect of photo-dissociation of the LIF signal of the fuel tracer mixtures was studied, and all fuel mixtures besides Toliso showed a more or less distinct decay in the fluorescence signal with time. In summary, all investigated fuel-tracer mixtures are suitable for LIF/Mie ratio droplet sizing in combination with nile red at moderate temperatures and low evaporation cooling rates.

Recognition Moieties of Small Molecular Fluorescent Probes for Bioimaging of Enzymes.

Enzymes are a class of important substances for life, and their abnormal levels are associated with many diseases. Thus, great progress has been made in the past decade in detecting and imaging enzymes in living biosystems, and in this respect fluorescent probes combined with confocal microscopy have attracted much attention because of their high sensitivity and unrivaled spatiotemporal resolution. Fluorescent probes are usually composed of three moieties: a signal or fluorophore moiety, a recognition or labeling moiety, and an appropriate linker to connect the two aforementioned moieties. At present, however, research and reviews on enzymatic probes mostly focus on fluorophores and/or linkers, whereas those on the recognition moiety are relatively few. Moreover, current enzymatic probes with some recognition moieties have drawbacks such as poor selectivity, high background fluorescence, or/and low sensitivity and are unsatisfactory for practical applications. Thus, developing new recognition moieties with higher specificity or/and sensitivity to the enzyme of interest is very desirable but still challenging. In this Account, we introduce the recognition moieties of fluorescent probes for several enzymes, including tyrosinase, monoamine oxidase A (MAO-A), nitroreductase (NTR), and aminopeptidases. Highlights are given on how new specific recognition moieties of tyrosinase and MAO-A were designed to eliminate the interference by reactive oxygen species (ROS) and MAO-B, respectively. Here we present four recent examples in which designed fluorescent probes are employed to image enzymes in living biosystems. The first example shows that 3-hydroxyphenyl can serve as a new and more specific recognition moiety than the traditional 4-hydroxyphenyl group for tyrosinase, enabling the development of a highly selective fluorescent probe for imaging of tyrosinase without interference by ROS. The second presents a general design strategy for fluorescent probes specific for an enzyme, which involves combining the characteristic structure of an inhibitor of the target enzyme along with its traditional reactive group as a new recognition moiety, and successfully demonstrates it by selective detection of MAO-A in the presence of its isomeric MAO-B. The third mainly illustrates that 5-nitrothiophen-2-yl alcohol with a stronger electron-donating S atom is a better fluorescence quenching and recognition moiety than 5-nitrofuran-2-yl alcohol for NTR, leading to the development of a highly sensitive method for NTR assay. Lastly, on the basis of known observations, we show that besides the specific interaction with the target, another function of some recognition moieties may be responsible for tuning the fluorescence signal, which is exemplified by the linking of several aminopeptidases' recognition moieties to the free hydroxyl or amino group of different fluorophores. It is our wish that this Account will promote the appearance of more specific recognition moieties and fluorescent probes with excellent properties and that new biofunctions of the enzymes will be uncovered.

Synthesis of polymacrocyclic compounds via Pd-catalyzed amination and evaluation of their derivatives as metal detectors

Abstract A mini-review is dedicated to the application of Pd(0)-catalyzed amination reactions for the synthesis of polymacrocyclic compounds of various architectures. Such molecules comprise diazacrown ether moieties or structural fragments of tri- and tetraazamacrocycles, polyamine or polyoxadiamine chains of different length and aromatic spacers. Polymacrocyclic compounds thus formed possess an increased number of coordination sites and are suitable for testing as potential receptors of metal cations. Some of these macrocyclic compounds were decorated with the exocyclic dansyl fluorophore group or were coupled with porphyrin units to form polymacrocyclic conjugates. Fluorescent spectra of these compounds were studied in the presence of various metal perchlorates and several macrocycles were found to act as chemosensors or molecular probes for such cations like Cu(II), Al(III), Cr(III).

Diketopyrrolopyrrole Bis-Phosphonate Conjugate: A New Fluorescent Probe for In Vitro Bone Imaging.

The synthesis of a conjugate molecule between an unusual red-fluorescent diketopyrrolopyrrole (DPP) unit and a bis-phosphonate (BP) precursor by a click-chemistry strategy to target bone tissue and monitor the interaction is reported. After thorough investigation, conjugation through a triazole unit between a γ-azido rather than a β-azido BP and an alkyne-functionalized DPP fluorophore group turned out to be the winning strategy. Visualization of the DPP-BP conjugate on osteoclasts and specific antiresorption activity were successfully demonstrated.

Crosslinking induced photoluminescence quenching in polyvinyl alcohol-carbon quantum dot composite

Highly luminescent and water-soluble carbon quantum dots (CQDs) have been integrated into polyvinyl alcohol (PVA) recently to realize composites with synergistic functionalities. The effects of chemical interactions between CQDs and PVA matrix on the changes in optical properties of CQDs or physicochemical properties of PVA are yet to be investigated fully. Herein, we first synthesized CQDs with different surface chemistry via varying the molar ratio between citric acid (CA) and ethylenediamine and then embedded the CQDs into PVA with or without additional CA crosslinking. Infrared and UV–vis studies on CQDs and composites showed that condensation between CQDs and PVA induced a redshift in the absorption peak originating from CQDs’ surface fluorophore groups. Interestingly, CA crosslinking significantly increased the water resistance, but it quenched the photoluminescence of composites. The quenching effects were reduced by using CQDs having less reactivity with CA.

A colorimetric and ratiometric fluorescent probe with ultralow detection limit and high selectivity for phosgene sensing

Phosgene is a kind of colourless and extreme toxic gas that poses a serious threat to public health and safety. A colorimetric and ratiometric fluorescent probe (AC-6ED), with anthracene carboximide as fluorophore and ethylenediamine group as recognition moiety has been developed for phosgene detection in solutions and in the gas phase based on the intramolecular charge transfer (ICT) mechanism. The AC-6ED traps phosgene molecule via intramolecular cyclization reaction to afford color and fluorescence emission change. The AC-6ED features low detection limit (0.09 nM), fast response (<20 s), remarkable colorimetric and ratiometric signal, excellent selectivity for phosgene over other interference analytes such as nerve agent mimics, various acyl chlorides and analogues. The AC-6ED loaded TLC plate can serve as a highly selective tool for phosgene sensing in the gas phase below health risk concentrations in a fast, portable, visible, and highly sensitive manner.

Spectroscopic Studies of Dual Fluorescence in 2-(4-Fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole: Effect of Molecular Aggregation in a Micellar System.

The article presents the results of spectroscopic studies focused on a selected compound from the 1,3,4-thiadiazole group—2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thia-diazole (FABT)—in a micellar system formed by Triton X-100, a non-ionic detergent. Fluorescence measurements revealed the phenomenon of dual fluorescence whose emergence is related to the particular molecular organisation of the compound, which depends both on the concentration of the detergent and, most of all, the concentration of the compound itself. Dual fluorescence of FABT in a micellar system was observed for the compound dissolved in a methanol aqueous system, i.e., an environment wherein the dual fluorescence of the compound had never been reported before. Based on the interpretation of UV-Vis electronic absorption, resonance light scattering (RLS), emission and excitation fluorescence spectra, as well as measurements of dynamic light scattering (DLS) and Principal Component Analysis (PCA), we were able to relate the occurrence of this effect to the process of molecular aggregation taking place between FABT molecules in the micellar system in question. Results of fluorescence spectra measurements and time-correlated single photon counting (TCSPC) indicate that dual fluorescence occurs at detergent concentrations necessary to form micellar systems, which in turn facilitate the process of aggregation of FABT molecules. The correlation between the observed fluorescence effects and the previous measurements performed for analogues from this group suggests the possibility of charge transfer (CT) within the range of detergent concentrations wherein the aforementioned fluorescence effects are observed. It ought to be emphasised that this type of fluorescence effects are relatively easy to induce, which predisposes this groups of fluorophores as ideal fluorescence probes in the context of biological samples.

An enhanced fluorescence sensor for specific detection Cys over Hcy/GSH and its bioimaging in living cells.

Cysteine (Cys) is not only the central matter of sulfur metabolism in cells but also the only amino acid with reduced thiol group in 20 kinds of natural amino acids. In animal cells, Cys is taking part in many important and essential biological functions including protein synthesis, detoxification and metabolism. The development and application of fluorescent probes for the detection of Cys have attracted more and more attention and interest. Herein, we report a new fluorescent probe NFA that utilized naphthyl carboxy fluorescein as fluorophore and acryloyl group as reaction site for Cys specific detection. The probe essentially has weak fluorescence. Cys addition to NFA containing system induced distinct enhanced fluorescence emission which was attributed to the nucleophilic reaction of cysteine and acryloyl to release the fluorophore. The signal fluorescent response detection system allows NFA to be a reliable tool for Cys detection with low detection limit (0.58 μM). And NFA has been successfully applied for Cys imaging specifically in live Hela cells, which promotes the probe as a potential tool to understand the pathology of Cys related diseases.

A nitroso-based fluorogenic probe for rapid detection of hydrogen sulfide in living cells

A turn-on fluorescent probe for hydrogen sulfide (H2S) employing flavylium derivative as the fluorophore and nitroso group as the recognition unit and was designed and synthesized. The free probe is almost non-fluorescent. Upon addition of H2S to the solution of the probe, its nitroso group was transformed to the corresponding amino group with fast reaction kinetics, affording a dramatic enhancement of fluorescence emission. The fluorescence intensity of the proposed probe at 625 nm showed a good linear with the concentration of NaHS over a range from 0 to 4 μM, with a limit detection of 29 nM (3δ). The proposed probe exhibited high selectivity, excellent sensitivity and rapid response (∼5 min) for H2S. Moreover, this probe was successfully used for fluorescence imaging of exogenous and endogenous H2S in living cells.

A dual-signal colorimetric and near-infrared fluorescence probe for the detection of exogenous and endogenous hydrogen peroxide in living cells

As a classic kind of reactive oxygen species (ROS), hydrogen peroxide (H2O2) plays a critical role in physiological and pathological processes. It is of significant importance to detect H2O2 with sufficient sensitivity, selectivity and universality in biological field. Herein a novel near-infrared probe (DCM-B) containing dicyanomethylene-4H-pyran as fluorophore and boronate ester group as the recognition unit was developed for the detection of H2O2. Experiments showed that the remarkable fluorescence enhancement and noticeable color change from yellow to purple were observed while H2O2 was added to DCM-B solution. It is proved that the boronate ester group of DCM-B cleavage and fluorescence off-on response based on intramolecular charge transfer (ICT) mechanism were obtained when the probe reacted with H2O2, and DCM-B showed excellent sensitivity, high selectivity to H2O2 detection in the presence of many competing analytes. Encouraged by the optical properties of near-infrared emission, it was successfully applied to the imaging of exogenous and endogenous hydrogen peroxide in living cells. More importantly, considering that the final metabolite of choline and glucose is H2O2 in living cells and organism, we expanded DCM-B to the indirect detection of choline and glucose with satisfactory performance.

Synthesis and fluorescence spectral studies of novel quinolylbenzothiazole-based sensors for selective detection of Fe3+ ion

Four novel fluorescence sensors bearing a quinolylbenzothiazole platform were synthesized and characterized. The sensors displayed excellent selectivity and highly sensitive fluorescence response to Fe3+ ion in H2O/DMSO buffer solution (1:4 volume ratio; Tris-HCl, 0.01 mol/L; pH = 7.40) at 500 nm originating from quinolylbenzothiazole fluorophore group. Other cations, namely Li+, Na+, K+, Mg2+, Ca2+, Co2+, Ni2+, Cd2+, Cu2+, Zn2+, Mn2+, Ba2+, Pb2+, Hg2+, Al3+, and Eu3+, showed no appreciable change in fluorescence spectrum. The binding stoichiometry between sensors L1, L2, L3, or L4 and Fe3+ was observed to be 1:1 based on fluorescence titration and Jobs plot analysis. The detection limits of L1, L2, L3, and L4 for Fe3+ were found to be 0.155, 0.362, 0.249, and 0.517 μmol/L, respectively. Furthermore, possible utilization of sensors to detect Fe3+ in living HeLa cells was also investigated by confocal fluorescence microscopy.

A highly selective fluorescent probe for the detection of hypochlorous acid in tap water and living cells

A turn-on fluorescent probe (DAME) for sensing hypochlorous acid (HClO) with excellent selectivity was presented. The fluorescent probe was composed of coumarin derivative as the fluorophore and dimethylcarbamothioic chloride group with a sulfide moiety as modulator. Additionally, the sulfide moiety would be oxidized by HClO, and then free dye of coumarin derivate was released and exhibited significant fluorescence. In addition, the probe could respond to HClO in solutions within 60 s and the limit of detection was down to 34.75 nM. Moreover, the probe was used for the detection of HClO in tap water through the home-made test paper. And confocal images confirmed that probe DAME could be used for recognizing HClO in living cells.

Synthesis and properties of ortho-carborane-appended 4-amino-phthalimide and its epoxy resin

A novel o-carborane derivative incorporating 4-amino-phthalimide as fluorophore group 1,2-bis(4-amino-phthalimidomethyl)-1,2-dicarba–closo-dodecaborane has been successfully synthesized and characterized. The new compound is found to emit green light. Incorporation of o-carborane cluster into the fluorophore leads to a small bathochromic shift of λabs and λem and a slight enhancement of quantum yield. The cross-linked polymer bearing o-carborane cage is prepared based on heat-curing reaction of the o-carborane appended 4-amino-phthalimide with epoxy resin. The polymer exhibits yellow-green emission property and excellent thermal stability.

Recent advances in capillary electrophoresis separation of monosaccharides, oligosaccharides, and polysaccharides

This article illustrates the basis and applications of methodologies for the analysis of simple and complex carbohydrates by means of CE. After a description of the most common and novel approaches useful for the analysis and characterization of carbohydrates, this review covers the recent advances in CE separation of monosaccharides, oligosaccharides, and polysaccharides. Various CE techniques are also illustrated for the study of carbohydrates derived from complex glyco-derivatives such as glycoproteins and glycolipids, essential for biopharmaceutical and glycoproteomics applications as well as for biomarker detection. Most glycans have no significant UV absorption, and derivatization with fluorophore groups prior to separation usually results in higher sensitivity and an improved electrophoretic profile. We also discuss the recent applications and separations by CE of derivatized simple and more complex carbohydrates with different chromophoric active tags. Overall, this review aims to give an overview of the most recent state-of-the-art techniques used in carbohydrate analysis by CE.