scholarly journals Novel Time-Resolved Fluorescence Immunochromatography Paper-Based Sensor with Signal Amplification Strategy for Detection of Deoxynivalenol

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6577
Author(s):  
Haowei Dong ◽  
Xingshuang An ◽  
Yaodong Xiang ◽  
Fukai Guan ◽  
Qi Zhang ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
High Sensitivity ◽  
Detection Sensitivity ◽  
Intensity Change ◽  
Fluorescence Signal ◽  
Time Resolved Fluorescence ◽  
Working Standard ◽  
Time Resolved ◽  
Field Detection ◽  
Antibody Labeling

Immunoassay has the advantages of high sensitivity, high specificity, and simple operation, and has been widely used in the detection of mycotoxins. For several years, time-resolved fluorescence immunochromatography (TRFIA) paper-based sensors have attracted much attention as a simple and low-cost field detection technology. However, a traditional TRFIA paper-based sensor is based on antibody labeling, which cannot easily meet the current detection requirements. A second antibody labeling method was used to amplify the fluorescence signal and improve the detection sensitivity. Polystyrene fluorescent microspheres were combined with sheep anti-mouse IgG to prepare fluorescent probes (Eu-IgGs). After the probe fully reacted with the antibody (Eu-IgGs-Abs) in the sample cell, it was deployed on the paper-based sensor using chromatography. Eu-IgGs-Abs that were not bound to the target were captured on the T-line, while those that were bound were captured on the C-line. The paper-based sensor reflected the corresponding fluorescence intensity change. Because a single molecule of the deoxynivalenol antibody could bind to multiple Eu-IgGs, this method could amplify the fluorescence signal intensity on the unit antibody and improve the detection sensitivity. The working standard curve of the sensor was established under the optimum working conditions. It showed the lower limit of detection and higher recovery rate when it was applied to actual samples and compared with other methods. This sensor has the advantages of high sensitivity, good accuracy, and good specificity, saving the amount of antibody consumed and being suitable for rapid field detection of deoxynivalenol.

Novel electrochemiluminescent materials for sensor applications

2014 ◽  
Vol 174 ◽  
pp. 357-367 ◽  
Author(s):  
Lynn Dennany ◽  
Zahera Mohsan ◽  
Alexander L. Kanibolotsky ◽  
Peter J. Skabara
Keyword(s):  
Redox Reactions ◽  
Limit Of Detection ◽  
Signal To Noise Ratio ◽  
High Sensitivity ◽  
Radical Cations ◽  
Detection Sensitivity ◽  
Sensor Development ◽  
Sensor Applications ◽  
Sensor Devices ◽  
The Impact

Electrochemiluminescence (ECL) uses redox reactions to generate light at an electrode surface, and is gaining increasing attention for biosensor development due to its high sensitivity and excellent signal-to-noise ratio. ECL studies of monodisperse oligofluorene–truxenes (T4 series) have been reported previously, showing the production of stable radical cations and radical anions, generating blue ECL. The compound in this study differs from the original structures, in that there are 2,1,3-benzothiadazole (BT) units inserted between the first and second fluorene units of the quarterfluorenyl arms. It was therefore anticipated that the incorporation of these highly luminescent and ECL-active compounds into sensor development would lead to significant decreases in detection limits. In this contribution, we report on the impact of incorporating these novel complexes into sensor devices on the ECL efficiency, as well as the ability of these to improve the detection sensitivity and decrease the limit of detection using the reagent-free detection of model analytes. The real world impact of these compounds is elucidated through the comparison with more standard ECL materials such as ruthenium-based compounds. The potential for multiple applications is to be examined within this contribution.

A Homogeneous Caspase-3 Activity Assay Using HTRF® Technology

2002 ◽  
Vol 7 (3) ◽  
pp. 267-274 ◽  
Author(s):  
M. Preaudat ◽  
J. Ouled-Diaf ◽  
B. Alpha-Bazin ◽  
G. Mathis ◽  
T. Mitsugi ◽  
...  
Keyword(s):  
Cysteine Proteases ◽  
Fluorescence Signal ◽  
Time Resolved Fluorescence ◽  
Time Resolved ◽  
Drug Candidates ◽  
Cell Death Pathway ◽  
Donor And Acceptor ◽  
Close Proximity ◽  
Active Cell Death ◽  
Cellular Components

Caspases are cysteine proteases presenting a conserved active site that cleaves protein substrates at a highly specific position. They are involved in different aspects of the active cell death pathway. Most of them act through proteolytic degradations of cellular components. This paper describes the assay development, assay validation, and screening for inhibitors of this enzyme, which could be potential drug candidates. The assay uses homogeneous time-resolved fluorescence based on energy transfer from europium cryptate as donor to cross-linked allophyco-cyanin as acceptor (XL665). A double-tagged substrate, biotinyl-E-aminocaproyl-L-aspartyl-L-glutamyl-L-valyl-L-aspartyl-L-alanyl-L-propyl-N∊-(2,4-dinitrophenyl)-L-lysine-amide (biotin-X-DEVDAPK(dnp)-NH2), is conjugated with streptavidin cryptate and anti-dnp-XL665 monoclonal antibody. The close proximity between donor and acceptor induces a specific time-resolved fluorescence signal. In the presence of enzyme activity, the substrate cleavage induces an unlinking of the two fluorescent probes and, subsequently, the disappearance of the specific signal as a result of loss of proximity. Experiments to optimize the reagent concentration, incubation times, precision, reproducibility, and robustness are discussed in comparison with a fluorometric method.

scholarly journals Determination of Anti-Acetylcholine Receptor Antibodies in Myasthenic Patients by Use of Time-resolved Fluorescence

2002 ◽  
Vol 48 (3) ◽  
pp. 549-554 ◽  
Author(s):  
Jan Říčný ◽  
Libuše Šimková ◽  
Angela Vincent
Keyword(s):  
Acetylcholine Receptor ◽  
Acetylcholine Receptors ◽  
Limit Of Detection ◽  
Linear Regression Analysis ◽  
Time Resolved Fluorescence ◽  
Time Resolved ◽  
Use Of Time ◽  
A Value ◽  
Restricted Use

Abstract Background: Autoantibodies against nicotinic acetylcholine receptor (nAChR) in myasthenia gravis (MG) patients are usually detected by radioimmunoprecipitation assays using extracted acetylcholine receptors labeled irreversibly with 125I-α-bungarotoxin (α-BuTx). To provide a nonradioactive immunoassay, we established an assay using nAChRs labeled with Eu3+-α-cobratoxin (α-CTx). Methods: We derivatized α-CTx with a diethylenetriaminepentaacetate moiety and formed a complex with Eu3+. The complex was purified by HPLC, and the fractions were tested for binding to Torpedo and human nAChRs. The most active fractions were used to label nAChRs for the immunoprecipitation assay, and the bound Eu3+ was quantified by time-resolved fluorescence. Results: Eu3+-labeled α-CTx competed with 125I-α-BuTx for binding to Torpedo nAChRs and saturated the binding sites of human nAChRs, with a Kd of 7.2 × 10−9 mol/L. Results of the immunoassay performed with Eu3+-labeled α-CTx were similar to those obtained with 125I-α-BuTx, with a slightly higher limit of detection [0.3 nmol/L (n = 6) vs ∼0.1 nmol/L for isotopic assay]. None of 34 negative sera tested (16 healthy controls, 10 patients with nonmyasthenia-related disease, 8 patients seronegative for MG) gave a value >0.3 nmol/L. Of the 35 positive myasthenic sera (with antibody values, previously determined by isotopic assay, of 0.4–1290 nmol/L) compared in the two assays, 32 tested positive with the Eu3+ assay. Linear regression analysis yielded the equation: y = 1.035x − 0.013 nmol/L; Sy|x = 0.172 nmol/L; r2 = 0.977. Conclusions: The new time-resolved fluorescence method for quantification of antibodies to nAChRs in MG patients provides a performance similar to that of the widely used isotopic assay and could be used in laboratories with restricted use of isotopes.

scholarly journals A FRET-ICT Dual-Modulated Ratiometric Fluorescence Sensor for Monitoring and Bio-Imaging of Cellular Selenocysteine

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 4999
Author(s):  
Zongcheng Wang ◽  
Chenhong Hao ◽  
Xiaofang Luo ◽  
Qiyao Wu ◽  
Chengliang Zhang ◽  
...  
Keyword(s):  
Real Time ◽  
Limit Of Detection ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
High Sensitivity ◽  
Fluorescence Sensor ◽  
Quantitative Detection ◽  
Fluorescence Signal ◽  
Ratiometric Fluorescence ◽  
Sensitivity And Selectivity

Since the fluctuation of cellular selenocysteine (Sec) concentration plays an all-important role in the development of numerous human disorders, the real-time fluorescence detection of Sec in living systems has attracted plenty of interest during the past decade. In order to obtain a faster and more sensitive small organic molecule fluorescence sensor for the Sec detection, a new ratiometric fluorescence sensor Q7 was designed based on the fluorescence resonance energy transfer (FRET) strategy with coumarin fluorophore as energy donor and 4-hydroxy naphthalimide fluorophore (with 2,4-dinitrobenzene sulfonate as fluorescence signal quencher and Sec-selective recognition site) as an energy acceptor. The sensor Q7 exhibited only a blue fluorescence signal, and displayed two well distinguished emission bands (blue and green) in the presence of Sec with ∆λ of 68 nm. Moreover, concentrations ranging of quantitative detection of Sec of Q7 was from 0 to 45 μM (limit of detection = 6.9 nM), with rapid ratiometric response, high sensitivity and selectivity capability. Impressively, the results of the living cell imaging test demonstrated Q7 has the potentiality of being an ideal sensor for real-time Sec detection in biosystems.

Time-Resolved Fluorescence-Based Assay for the Determination of Alkaline Phosphatase Activity and Application to the Screening of Its Inhibitors

2007 ◽  
Vol 13 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Petra Schrenkhammer ◽  
Ina C. Rosnizeck ◽  
Axel Duerkop ◽  
Otto S. Wolfbeis ◽  
Michael Schäferling
Keyword(s):  
Alkaline Phosphatase ◽  
Limit Of Detection ◽  
Single Step ◽  
Central Metal ◽  
Time Resolved Fluorescence ◽  
Time Resolved ◽  
State Measurement ◽  
Steady State Measurement ◽  
Enzyme Alkaline Phosphatase

A single-step end point method is presented for determination of the activity of the enzyme alkaline phosphatase (ALP) using the effect of enhancement of fluorescence of the easily accessible europium(III)-tetracycline 3:1 complex (Eu3TC). Its luminescence, peaking at 616 nm if excited at 405 nm, is enhanced by a factor of 2.5 in the presence of phosphate. Phenyl phosphate was used as a substrate that is enzymatically hydrolyzed to form phenol and phosphate. The latter coordinates to Eu3TC and enhances its luminescence intensity as a result of the displacement of water from the inner coordination sphere of the central metal. The assay is performed in a time-resolved (gated) mode, which is shown to yield larger signal changes than steady-state measurement of fluorescence. The limit of detection for ALP is 4 µmol L—1. Based on this scheme, a model assay for theophylline as inhibitor for ALP was developed with a linear range from 14 to 68 µmol L— 1 of theophylline. ( Journal of Biomolecular Screening 2008:9-16)

scholarly journals Visualizing the emission of a single photon with frequency and time resolved spectroscopy

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 474
Author(s):  
Aleksei Sharafiev ◽  
Mathieu L. Juan ◽  
Oscar Gargiulo ◽  
Maximilian Zanner ◽  
Stephanie Wögerer ◽  
...  
Keyword(s):  
Quantum Electrodynamics ◽  
Quantum Physics ◽  
Single Photon ◽  
High Sensitivity ◽  
Analytical Description ◽  
Ultrafast Dynamics ◽  
Level System ◽  
Time Resolved Fluorescence ◽  
Resonant Frequencies ◽  
Time Resolved

At the dawn of Quantum Physics, Wigner and Weisskopf obtained a full analytical description (a photon portrait) of the emission of a single photon by a two-level system, using the basis of frequency modes (Weisskopf and Wigner, "Zeitschrift für Physik", 63, 1930). A direct experimental reconstruction of this portrait demands an accurate measurement of a time resolved fluorescence spectrum, with high sensitivity to the off-resonant frequencies and ultrafast dynamics describing the photon creation. In this work we demonstrate such an experimental technique in a superconducting waveguide Quantum Electrodynamics (wQED) platform, using single transmon qubit and two coupled transmon qubits as quantum emitters. In both scenarios, the photon portraits agree quantitatively with the predictions of the input-output theory and qualitatively with Wigner-Weisskopf theory. We believe that our technique allows not only for interesting visualization of fundamental principles, but may serve as a tool, e.g. to realize multi-dimensional spectroscopy in waveguide Quantum Electrodynamics.

scholarly journals Europium Nanoparticles and Time-resolved Fluorescence for Ultrasensitive Detection of Prostate-specific Antigen

2001 ◽  
Vol 47 (3) ◽  
pp. 561-568 ◽  
Author(s):  
Harri Härmä ◽  
Tero Soukka ◽  
Timo Lövgren
Keyword(s):  
Detection Limit ◽  
Prostate Specific Antigen ◽  
Specific Antigen ◽  
High Specific Activity ◽  
Microtiter Plate ◽  
Detection Sensitivity ◽  
Time Resolved Fluorescence ◽  
Time Resolved ◽  
Biochemical Assays ◽  
Microtiter Plate Format

Abstract Background: Nanoparticle-based detection technologies have the potential to improve detection sensitivity in miniature as well as in conventional biochemical assays. We introduce a detection technology that relies on the use of europium(III) nanoparticles and time-resolved fluorometry to improve the detection limit of biochemical assays and to visualize individual molecules in a microtiter plate format. Methods: Streptavidin was covalently coated on 107-nm nanoparticles containing >30 000 europium molecules entrapped with β-diketones. In a model assay system, these nanoparticles were used to trace biotinylated prostate-specific antigen (PSA) in a microtiter plate format. Results: The detection limit (mean + 3 SD of the zero calibrator) of biotinylated PSA was 0.38 ng/L, corresponding to 10 fmol/L or 60 zeptomoles (60 × 10−21 moles) of PSA. Moreover, single nanoparticles, representing individual PSA molecules, were visualized in the same microtiter wells with a time-resolved fluorescence microscope using a ×10 objective. Single nanoparticles, possessing high specific activity, were also detected in solution by a standard time-resolved plate fluorometer. Conclusions: The universal streptavidin-coated europium(III) nanoparticle label is suitable for detection of any biotinylated molecule either in solution or on a solid phase. The europium(III) nanoparticle labeling technology is applicable to many areas of modern biochemical analysis, such as immunochemical and multianalyte DNA-chip assays as well as histo- and cytochemistry to improve detection sensitivities.

Analytical Models for Time-Resolved Fluorescence Spectroscopy in Tissues

2000 ◽  
Author(s):  
Mostafa Sadoqi ◽  
Peter Riseborough ◽  
Sunil Kumar
Keyword(s):  
Numerical Solutions ◽  
Analytical Models ◽  
Fluorescence Signal ◽  
Scattering Medium ◽  
Time Resolved Fluorescence ◽  
Time Resolved ◽  
Scattering Material ◽  
Emission Light

Abstract Laser induced fluorescence is a rapidly growing technique for the characterization of scattering material, most notably in in-vivo biomedical testing. Most previous applications have relied on the measurements of the steady-state emission spectrum, with subsequent analysis of the spectrum for relative concentrations of potential fluorophores. Only recently a few investigators have explored the use of the fluorescence lifetimes as a diagnostic tool by taking advantage of the perturbation of the lifetime by multiple scattering of the excitation and emission light in the tissue. We have developed a model to study the fluorescence signal generated by a fluorophore distributed in a scattering medium. This model is based on two coupled transient transfer phenomena: the transport of the pulsed source laser, and the induced transient fluorescence excited by the laser. The two are coupled through the source term for the induced fluorescence field. Whereas previous research focused mainly on the fluorescence properties of various dyes, compounds, and materials, only recently have such transport questions been addressed by researchers. In addition, the studies that have been done in the literature have taken the optical properties of the tissue to be the same at the excitation and emission wavelengths. We have presented analytical and numerical solutions for finite, infinite, cylindrical and spherical geometries.

scholarly journals An Aptamer-Array-Based Sample-to-Answer Biosensor for Ochratoxin A Detection via Fluorescence Resonance Energy Transfer

Chemosensors ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 309
Author(s):  
Yongning Li ◽  
Zhenfei Peng ◽  
Yaxi Li ◽  
Min Xiao ◽  
Gongjun Tan ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Ochratoxin A ◽  
Fluorescence Resonance Energy Transfer ◽  
Limit Of Detection ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
High Sensitivity ◽  
Detection Methods ◽  
Fluorescence Signal ◽  
Fluorescence Resonance

Food toxins are a hidden threat that can cause cancer and tremendously impact human health. Therefore, the detection of food toxins in a timely manner with high sensitivity is of paramount importance for public health and food safety. However, the current detection methods are relatively time-consuming and not practical for field tests. In the present work, we developed a novel aptamer-chip-based sample-to-answer biosensor (ACSB) for ochratoxin A (OTA) detection via fluorescence resonance energy transfer (FRET). In this system, a cyanine 3 (Cy3)-labeled OTA-specific biotinylated aptamer was immobilized on an epoxy-coated chip via streptavidin-biotin binding. A complementary DNA strand to OTA aptamer at the 3′-end was labeled with a black hole quencher 2 (BHQ2) to quench Cy3 fluorescence when in proximity. In the presence of OTA, the Cy3-labeled OTA aptamer bound specifically to OTA and led to the physical separation of Cy3 and BHQ2, which resulted in an increase of fluorescence signal. The limit of detection (LOD) of this ACSB for OTA was 0.005 ng/mL with a linearity range of 0.01–10 ng/mL. The cross-reactivity of ACSB against other mycotoxins, ochratoxin B (OTB), aflatoxin B1 (AFB1), zearalenone (ZEA), or deoxynilvalenol (DON), was less than 0.01%. In addition, this system could accurately detect OTA in rice samples spiked with OTA, and the mean recovery rate of the spiked-in OTA reached 91%, with a coefficient of variation (CV) of 8.57–9.89%. Collectively, the ACSB may represent a rapid, accurate, and easy-to-use platform for OTA detection with high sensitivity and specificity.

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