Fluorescent Probe For Quantitative Detection Research Articles

Facile preparation of low temperature carbon dots with long-wavelength emission and their sensing applications for crystal violet

Crystal violet (CV) is one of the main components of common fungicides in daily life, which has inhibitory effect on gram-positive bacteria. However, CV remains in the environment for a long time and have potential risk of disease. Therefore, it is necessary to develop effective methods for detecting CV. Low-temperature carbon dots (LT-CDs) are studied to provide a new idea for the development of CDs green preparation technology from the perspective of low energy consumption. In this experiment, LT-CDs with long-wavelength emission were prepared based on the oxidation, cross-linking polymerization and Schiff base reaction using o-phenylenediamine and hydroquinone as carbon source at low temperature, and were characterized by various techniques. It was found that LT-CDs could be used as a fluorescent probe for quantitative detection of CV based on the inner filter effect, and the practicability of the method was verified by real samples.

Development of a carbazole-based fluorescent probe for quantitative detection of fluoride ions in aqueous systems

Development of a carbazole-based fluorescent probe for quantitative detection of fluoride ions in aqueous systems

Self-organized nanoreceptors-based fluorescent probe for quantitative detection of denatured glutathione

Though a number of protocols have been developed for the detection of glutathione (GSH), insufficient attention has been paid to the quantitative discrimination of the denaturation of GSH. In this study, monolayer protected gold nanoparticles (MPGN) featured with cationic trimethylammonium headgroups were elaborately designed as self-organized nanoreceptors. Taken 1-pyrenesulfonic acid sodium salt as indicator, of which the fluorescence can be completely quenched through the binding with MPGN and recovered by the presence of GSH, the detection of GSH can be achieved. Moreover, due to the dominating role of thiol group played in the GSH discrimination process, the GSH/GSSG (glutathione disulfide) ratio can be quantitatively analyzed through the fluorescence response. The facile methodology presented herein will provide instructive direction for the evaluation of GSH based pharmaceuticals.

A highly selective and sensitive ratiometric fluorescent probe for quantitative detection of Al(III) in different natural matrices

A highly selective and sensitive assay of Al(III) using ratiometric fluorescence enhancement is reported in an aqueous solution. The probe (named RS5) exhibits a red-shift of 54 nm upon binding with Al(III) ion. The significant enhancement response of RS5 at 481 nm is attributed to the formation of a 1:1 complex between the probe and Al(III), wherein RS5 acts as a tridentate NNN-donor ligand. The complexation process is ascertained by 1H, 13C, and 27Al NMR and HR-MS spectral techniques. The binding constant of the complex is determined to be 1.3 × 105 M−1. The ratiometric change in fluorescence upon complexation with Al(III) is ascribed to an increase in intramolecular charge transfer (ICT) transition along with chelation enhanced fluorescence (CHEF) processes. The probe can be applied for monitoring Al(III) in a pH range of 6–8. The limit of detection (LOD) of RS5 for the examination of Al(III) is found to be 0.3 μM. With an aim to understand the sensing behavior of RS5, the optical properties of the probe and its Al(III) complex are investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The probe is successfully employed for the determination of Al(III), with very high recovery percentages, in natural matrices like deep well water, tap water, drinking water, pond water, river water, bovine serum albumin (BSA) solution and blood serum.

A novel ratiometric fluorescent probe for quantitative detection of isocyanates in air

Abstract Isocyanates are important industrial raw materials, but they are hazardous to human health. Especially, gaseous isocyanates cause serious public health problems. Therefore, it is significant to monitor isocyanates in air. In this work, a novel ratiometric fluorescent probe based on a new fluorophore platform, which is designed by inserting a styryl π-bridge between donor and acceptor units of 1, 8-naphthalimide, was developed for quantitative detection of gaseous isocyanates. In the presence of isocyanates, fluorescence of probe solution changed from orange to yellow-green, which caused by alteration of substituent at the 4th position of styryl group resulted from reaction between isocyanates and probe, thus achieving ratiometric detection for isocyanates. And this probe exhibited a fast, sensitive and selective response towards isocyanates. Furthermore, probe solution absorption method was employed to detect quantitatively isocyanates in air. This strategy may be a powerful tool for monitoring isocyanates in air, and also provide a referable approach for detection of volatile organic compounds in air.

A highly selective colorimetric and fluorescent probe for quantitative detection of Cu2+/Co2+: The unique ON-OFF-ON fluorimetric detection strategy and applications in living cells/zebrafish.

Identifying and detecting similar target cations through combining "turn on" and "turn off" fluorescence mechanism is effective and challenging. Now a new colorimetric and ON-OFF-ON fluorescent probe N'-((7-(diethylamino)-2-oxo-2H-chromen-3-yl)methylene)-3-hydroxy-2-naphthohydrazide (L) was reported, which could detect Cu2+ and Co2+ in phosphate buffered CH3CH2OH-H2O solvent system. With the assistance of glutathione and pH adjustment, a unique ON-OFF-ON fluorescence detection strategy could be achieved for distinguishing Cu2+ and Co2+. The emission of probe could recover from the L-Cu2+ and L-Co2+ system by addition of GSH or adjusting pH value to 4, respectively, which is due to the abolishment of paramagnetic Cu2+/Co2+. Based on fluorescence titration experiments, the limit of detection was determined as 3.84 × 10-9 M and 4.55 × 10-9 M for Cu2+ and Co2+, respectively. Meanwhile, the detection limit reached 6.21 × 10-8 M for Cu2+ and 6.96 × 10-8 M for Co2+ according to absorbance signal output. Fast recognition of Cu2+/Co2+ can be achieved by obvious color changes from green to colorless under UV light, as well as from yellow to orange-red in room light. The binding mode of L toward Cu2+ and Co2+ have been systematically studied by Job's plot analysis, ESI-MS, IR and density functional theory calculations. Most strikingly, further practical applications of the probe L in fluorescence imaging were investigated in MCF-7 cells and zebrafish due to its low cytotoxicity and good optical properties, suggesting that L could serve as a fluorescent sensor for tracking Cu2+ and Co2+in vivo.

A Novel ESIPT Phthalimide-Based Fluorescent Probe for Quantitative Detection of H2O2.

Hydrogen peroxide (H2O2) is a majority reactive oxygen species (ROS) and acts as an essential role in pathological and physiological processes. Therefore, the development of quantitative detection of methods for H2O2 is necessary. Here, we constructed of a novel simple fluorescence probe for detection of H2O2 based on the excited-state intramolecular proton transfer process. The probe utilized a phthalimide derivative as the fluorophore and selected phenylboronic acid as the recognition site for H2O2. In response to H2O2, the probe exhibited 63-fold fluorescence intensity enhancement, a low detection limit (8.4 × 10–8 M), and large Stokes shift (111 nm). In addition, the probe displayed high selectivity for H2O2 over other ROS. Moreover, the probe was successfully employed for imaging of H2O2 in living cells.

A highly sensitive and selective fluorescent probe for quantitative detection of Al3+ in food, water, and living cells.

Three novel β-pinene-based fluorescent probes 2a–2c were designed and synthesized for the selective detection of Al3+. Probe 2a showed higher fluorescence intensity toward Al3+ than the other two compounds. Probe 2a determined the concentration of Al3+ with a rapid response time (45 s), wide pH range (pH = 1–9), excellent sensitivity (LOD = 8.1 × 10−8 M) and good selectivity. The recognition mechanism of probe 2a toward Al3+ was confirmed by 1H NMR, HRMS and DFT analysis. Probe 2a was successfully used as a signal tool to quantitatively detect Al3+ in food samples and environmental water samples. Furthermore, probe 2a was successfully utilized to label intracellular Al3+, indicating its promising applications in living cells.

A highly selective and sensitive fluorescent probe for quantitative detection of Hg2+ based on aggregation-induced emission features

A π-conjugated cyanostilbene derivative of (Z)-2-(4-nitrophenyl)-3-(4-(vinyloxy)phenyl)acrylonitrile (CN-vinyl) had been designed, synthesized and confirmed by the standard spectroscopic analyses. CN-vinyl possesses an unusual high emissive aggregation-induced emission (AIE) feature in a tetrahydrofuran/water mixture (2:8, v/v). The fluorescence intensity of CN-vinyl can be quenched linearly with the addition of Hg2+ in a range of 0–50μM with a correlation coefficient of R2=0.9957. The detection limit of Hg2+ is 37nM. The mechanism for Hg2+-mediated optical properties of CN-vinyl is due to the selective cleavage of vinyl group by Hg2+. Accuracy of the proposed methodology was evaluated by means of the recovery study in real samples and the analyzing certified reference material of the standard solution of Hg2+. By this novel strategy, CN-vinyl can be used for quantitative detection of Hg2+ as well as the presence of other physiological relevant metal ions.

Ratiometric Two-Photon Fluorescent Probe for Quantitative Detection of β-Galactosidase Activity in Senescent Cells

We reported a ratiometric two-photon fluorescent probe (SG1) for β-galactosidase (β-gal) and its application to quantitative detection of β-gal activity during cellular senescence in live cells and in aged tissues. This probe is characterized by a significant two-photon excited fluorescence, a marked blue-to-yellow emission color change in response to β-gal, easy loading, insensitivity to pH and reactive oxygen species (ROS), high photostability, and low cytotoxicity. In addition, we show that SG1 labeling is an effective tool for quantitative detection of senescence-associated β-gal activity at the subcellular level in situ. This finding demonstrates that SG1 will find useful applications in biomedical research, including studies of cell aging.

New rhodamine-based turn-on and colorimetric probe for copper(II) ion with high selectivity and sensitivity

A new rhodamine-based derivative fluorescent probe (L) was synthesized as a highly selective and turn-on fluorescent probe for quantitative detection of Cu2+ exhibiting an almost 200-fold fluorescence increase. Moreover, the X-ray single crystal structure of the probe had also been measured. Besides, the fluorescent probe can also be considered as a good OFF–ON switch for Cu2+ with naked-eye colour change from colorless to pink. The 1:1 binding ratio between chemosensor L and Cu2+ was investigated using Job’s plot method, 1H NMR titration and ESI-MS. The probe exhibited excellent selectivity and sensitivity toward Cu2+ with little interference, meanwhile the detection limit of Cu2+ was at a quite lower micromolar level.

A Highly Selective Fluorescent Probe for Quantitative Detection of Hydrogen Sulfide

We designed and synthesized a highly selective and sensitive fluorescent probe for hydrogen sulfide (H2S) based on the one step nucleophilic addition reaction between H2S and electron-poor C=C double bond. Our proposed probe displayed high selectivity for H2S over other analytes including cysteine (Cys) and glutathione (GSH), which might be because the steric hindrance of H2S is less than other thiols. Additionally, a linear relationship between fluorescence intensity and the concentrations of Na2S (0-450 μM) was obtained in an aqueous buffer solution (pH 7.4, 20 mM PBS). Particularly, we found that the adoption of the acetyl benzimidazole derivative as a recognition receptor to distinguish H2S from other thiols and analytes provides a promising methodology for the design of fluorescent probes for the determination of H2S.

A colorimetric and ratiometric fluorescent probe for quantitative detection of GSH at physiologically relevant levels

A naphthalene derivate containing piazselenole (NDP) has been developed as an example of colorimetric and ratiometric fluorescent probes for glutathione (GSH) at physiologically relevant concentration. Upon addition of GSH, the probe displayed a ratiometric fluorescent response with an enhancement of the ratios of emission intensities at 436 and 615 nm, accompanied with the solution color change from jacinth to colorlessness. The detection range is 0–80 mM with the detection limit of 0.178 mM. Moreover, the probe showed good selectivity and satisfying results in the determination of GSH. As the linear response range covers the concentration range of biological samples, the probe may have the potential to determine GSH directly in biological samples in the future.

Studies of Interaction Between Cyanine Dye T-284 and Fibrillar Alpha-Synuclein

A key feature of Parkinson's disease is the formation and accumulation of amyloid fibrils of the natively unfolded protein α-synuclein (ASN) inside neurons. Recently we have proposed novel sensitive monomethinecyanine dye T-284 as fluorescent probe for quantitative detection of ASN amyloid fibrils. In this study the T-284 dye complex with ASN fibril was characterized by means of fluorescence anisotropy, atomic force microscopy and time-resolved fluorescence techniques to give further insights into the mode of dye interaction with amyloid fibrils. The fluorescence anisotropy of T-284 was shown to noticeably increase upon addition of aggregated proteins indicating on stable dye/amyloid fibril complex formation. AFM imaging of fibrillar wild-type ASN revealed differences in heights between ASN fibrils alone and in presence of the T-284 dye (6.37 ± 1.0nm and 8.0 ± 1.1nm respectively), that is believed to be caused by embedding of T-284 dye molecules in the "binding channel" running along the fibril. Fluorescence decay analysis of the T-284 in complexes with fibrillar ASN variants revealed the fluorescence lifetime values for T-284/fibril complexes to be an order of magnitude higher as compared to the free dye. Also, the fluorescence decay of free T-284 was bi-exponential, while dye bound to protein yields tri-exponential decay. We suppose that in complexes with fibrillar ASN variants T-284 dye might exist in different "populations" due to interaction with fibrils in different conformers and ways. The exact binding mode of T-284 with ASN fibrils needs further studies. Studied parameters of dye/amyloid fibril complexes are important for the characterization and screening of newly-developed amyloid-sensitive dyes.

Synthesis and Characterization of Double-layer Quantum-Dots-Tagged Microspheres

Quantum-dots-tagged poly (styrene-acrylamide-acrylic acid) microspheres (QDsAAMs) were synthesized and modified with hydrazine hydrate through hydrazinolysis. Azidocarbonyl groups, which can be rapidly coupled with proteins under mild conditions, were introduced onto the surface of QDsAAM using azido reaction. Bovine serum albumin (BSA) was selected as model protein to be covalently immobilized on the azidocarbonyl QDsAAM. Instruments such as fluorescence microscope, optical microscope, confocal laser scanning microscope, UV-visible spectrometer, Fourier transform infrared spectrometer, size analyzer, and fluorescence spectrophotometer were used to characterize QDsAAM. Results showed that QDsAAM had a regular double-layer spherical shape and an average diameter of 11.2 microm. It also displayed high fluorescence intensity (lambda(ex)/lambda(em) = 250 nm/370 nm), which showed linearity with concentrations ranging from 3.0 x10(-3) to 90.0 x10(-3) g.L(-1). In addition, external factors such as pH and ionic strength exerted little influence on fluorescent characteristic. BSA immobilization indicated that QDsAAM with azidocarbonyl groups could be covalently coupled with BSA at the rate of 40 x10(-3) g/g (BSA/QDsAAM), while fluorescence linearity correlation was also found. This functional azidocarbonyl QDsAAM with sensitive fluorescence and active azidocarbonyl groups could be used as a promising fluorescent probe for quantitative detection, protein immobilization, and early rapid clinical diagnostics.

Novel functionalized ternary copolymer fluorescent nanoparticles: synthesis, fluorescent characteristics and protein immobilization

Novel fluorescent poly(styrene-acrylamide-acrylic acid) nanoparticles (FPSAAN) were synthesized by means of soapless emulsion polymerization and being modified with hydrazine hydrate by hydrazinolysis. The azidocarbonyl groups which can be rapidly coupled with proteins under mild condition were introduced onto the fluorescent nanoparticles by azido-reaction. Bovine serum albumin (BSA) was selected as a model protein to be covalently immobilized on the azidocarbonyl FPSAAN. Atom force microscopy (AFM), Transmission electron microscopy (TEM), Ultraviolet-visible (UV/Vis) spectrometer, Fourier transforms infrared spectrometer (FTIR), nanoparticle size analyzer and fluorescence spectrophotometer were used to characterize the FPSAAN. Results showed that FPSAAN had a regular spherical shape, and a dramatic narrow size distribution (polydispersity index 0.046 +/- 0.009). The fluorescence intensity of FPSAAN (lambda(ex)/lambda(em) = 253/306 nm), hydrazide-FPSAAN (lambda(ex/)lambda(em) = 260/326 nm), and protein-immobilized FPSAAN (lambda(ex)/lambda(em) = 258/325 nm) was linearly related to the concentration ranging from 1.0 x 10(-3) g l(-1) to 10.0 x 10(-3) g l(-1). The linear relationship was obtained. The equations are y = 52.808x + 16.465 (R (2) = 0.9927), y = 5.1814x + 4.1535 (R (2) = 0.9935) and y = 5.2227x + 5.2883 (R (2) = 0.9937), respectively. In addition, external factors such as pH and ionic strength exert a slight influence on fluorescent properties. The experiments of the immobilization of BSA indicated that FPSAAN with azidocarbonyl groups could be covalently coupled with BSA at the rate of 41.1%. Meanwhile, hCG antibody immobilized FPSAAN have the similar fluorescence characteristics to BSA immobilized FPSAAN. Only negligible difference of the fluorescence characteristics can be found. Furthermore, the fluorescence characteristics of hCG antibody immobilized FPSAAN have not been obviously affected after mixed with the hCG antigen and human plasma. These novel azidocarbonyl FPSAAN with stable fluorescence and active functional azidocarbonyl groups could be used as a promising fluorescent probe for quantitative detection, protein immobilization, cell labeling research and early rapid clinical diagnostics.