The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Ulrich J Krull - One of the best experts on this subject based on the ideXlab platform.
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paper based solid phase multiplexed nucleic acid hybridization assay with tunable dynamic range using immobilized quantum dots as donors in fluorescence resonance energy transfer
Analytical Chemistry, 2013Co-Authors: Omair M Noor, Ulrich J KrullAbstract:A multiplexed solid-phase nucleic acid hybridization assay on a paper-based platform is presented using multicolor immobilized quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET). The surface of paper was modified with imidazole groups to immobilize two types of QD-probe oligonucleotide conjugates that were assembled in solution. Green-emitting QDs (gQDs) and red-emitting QDs (rQDs) served as donors with Cy3 and Alexa Fluor 647 (A647) acceptors. The gQD/Cy3 FRET pair served as an internal standard, while the rQD/A647 FRET pair served as a detection channel, combining the control and Analytical test zones in one physical location. Hybridization of dye-labeled oligonucleotide targets provided the proximity for FRET sensitized emission from the acceptor dyes, which served as an Analytical Signal. Hybridization assays in the multicolor format provided a limit of detection of 90 fmol and an upper limit of dynamic range of 3.5 pmol. The use of an array of detection zones was designed t...
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paper based solid phase nucleic acid hybridization assay using immobilized quantum dots as donors in fluorescence resonance energy transfer
Analytical Chemistry, 2013Co-Authors: Omair M Noor, Anna Shahmuradyan, Ulrich J KrullAbstract:A paper-based solid-phase assay is presented for transduction of nucleic acid hybridization using immobilized quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET). The surface of paper was modified with imidazole groups to immobilize QD–probe oligonucleotide conjugates that were assembled in solution. Green-emitting QDs (gQDs) were FRET-paired with Cy3 acceptor. Hybridization of Cy3-labeled oligonucleotide targets provided the proximity required for FRET-sensitized emission from Cy3, which served as an Analytical Signal. The assay exhibited rapid transduction of nucleic acid hybridization within minutes. Without any amplification steps, the limit of detection of the assay was found to be 300 fmol with the upper limit of the dynamic range at 5 pmol. The implementation of glutathione-coated QDs for the development of nucleic acid hybridization assay integrated on a paper-based platform exhibited excellent resistance to nonspecific adsorption of oligonucleotides and showed no reducti...
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multiplexed interfacial transduction of nucleic acid hybridization using a single color of immobilized quantum dot donor and two acceptors in fluorescence resonance energy transfer
Analytical Chemistry, 2010Co-Authors: Russ W Algar, Ulrich J KrullAbstract:A multiplexed solid-phase assay for the detection of nucleic acid hybridization was developed on the basis of a single color of immobilized CdSe/ZnS quantum dot (QD) as a donor in fluorescence resonance energy transfer (FRET). This work demonstrated that two channels of detection did not necessitate two different QD donors. Two probe oligonucleotides were coimmobilized on optical fibers modified with QDs, and a sandwich assay was used to associate the acceptor dyes with interfacial hybridization events without target labeling. FRET-sensitized acceptor emission provided an Analytical Signal that was concentration dependent down to 10 nM. Changes in the ratio of coimmobilized probe oligonucleotides were found to yield linear changes in the relative amounts of acceptor emission. These changes were compared to previous studies that used mixed films of two QD donors for two detection channels. The analysis indicated that probe dilution effects were primarily driven by changes in acceptor number density and tha...
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toward a multiplexed solid phase nucleic acid hybridization assay using quantum dots as donors in fluorescence resonance energy transfer
Analytical Chemistry, 2009Co-Authors: Russ W Algar, Ulrich J KrullAbstract:Solid-phase assays using immobilized quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET) have been developed for the selective detection of nucleic acids. QDs were immobilized on optical fibers and conjugated with probe oligonucleotides. Hybridization with acceptor labeled target oligonucleotides generated FRET-sensitized acceptor fluorescence that was used as the Analytical Signal. A sandwich assay was also introduced and avoided the need for target labeling. Green and red emitting CdSe/ZnS QDs were used as donors with Cy3 and Alexa Fluor 647 acceptors, respectively. Quantitative measurements were made via spectrofluorimetry or fluorescence microscopy. Detection limits as low as 1 nM were obtained, and the discrimination of single nucleotide polymorphisms (SNPs) with contrast ratios as high as 31:1 was possible. The assays retained their selectivity and at least 50% of their Signal when tested in bovine serum and against a large background of noncomplementary genomic DNA. Mixed ...
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interfacial transduction of nucleic acid hybridization using immobilized quantum dots as donors in fluorescence resonance energy transfer
Langmuir, 2009Co-Authors: Russ W Algar, Ulrich J KrullAbstract:Fluorescence resonance energy transfer (FRET) using immobilized quantum dots (QDs) as energy donors was explored as a transduction method for the detection of nucleic acid hybridization at an interface. This research was motivated by the success of the QD-FRET-based transduction of nucleic acid hybridization in solution-phase assays. This new work represents a fundamental step toward the assembly of a biosensor, where immobilization of the selective chemistry on a surface is desired. After immobilizing QD-probe oligonucleotide conjugates on optical fibers, a demonstration of the retention of selectivity was achieved by the introduction of acceptor (Cy3)-labeled single-stranded target oligonucleotides. Hybridization generated the proximity required for FRET, and the resulting fluorescence spectra provided an Analytical Signal proportional to the amount of target. This research provides an important framework for the future development of nucleic acid biosensors based on QDs and FRET. The most important fin...
Russ W Algar - One of the best experts on this subject based on the ideXlab platform.
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multiplexed interfacial transduction of nucleic acid hybridization using a single color of immobilized quantum dot donor and two acceptors in fluorescence resonance energy transfer
Analytical Chemistry, 2010Co-Authors: Russ W Algar, Ulrich J KrullAbstract:A multiplexed solid-phase assay for the detection of nucleic acid hybridization was developed on the basis of a single color of immobilized CdSe/ZnS quantum dot (QD) as a donor in fluorescence resonance energy transfer (FRET). This work demonstrated that two channels of detection did not necessitate two different QD donors. Two probe oligonucleotides were coimmobilized on optical fibers modified with QDs, and a sandwich assay was used to associate the acceptor dyes with interfacial hybridization events without target labeling. FRET-sensitized acceptor emission provided an Analytical Signal that was concentration dependent down to 10 nM. Changes in the ratio of coimmobilized probe oligonucleotides were found to yield linear changes in the relative amounts of acceptor emission. These changes were compared to previous studies that used mixed films of two QD donors for two detection channels. The analysis indicated that probe dilution effects were primarily driven by changes in acceptor number density and tha...
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toward a multiplexed solid phase nucleic acid hybridization assay using quantum dots as donors in fluorescence resonance energy transfer
Analytical Chemistry, 2009Co-Authors: Russ W Algar, Ulrich J KrullAbstract:Solid-phase assays using immobilized quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET) have been developed for the selective detection of nucleic acids. QDs were immobilized on optical fibers and conjugated with probe oligonucleotides. Hybridization with acceptor labeled target oligonucleotides generated FRET-sensitized acceptor fluorescence that was used as the Analytical Signal. A sandwich assay was also introduced and avoided the need for target labeling. Green and red emitting CdSe/ZnS QDs were used as donors with Cy3 and Alexa Fluor 647 acceptors, respectively. Quantitative measurements were made via spectrofluorimetry or fluorescence microscopy. Detection limits as low as 1 nM were obtained, and the discrimination of single nucleotide polymorphisms (SNPs) with contrast ratios as high as 31:1 was possible. The assays retained their selectivity and at least 50% of their Signal when tested in bovine serum and against a large background of noncomplementary genomic DNA. Mixed ...
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interfacial transduction of nucleic acid hybridization using immobilized quantum dots as donors in fluorescence resonance energy transfer
Langmuir, 2009Co-Authors: Russ W Algar, Ulrich J KrullAbstract:Fluorescence resonance energy transfer (FRET) using immobilized quantum dots (QDs) as energy donors was explored as a transduction method for the detection of nucleic acid hybridization at an interface. This research was motivated by the success of the QD-FRET-based transduction of nucleic acid hybridization in solution-phase assays. This new work represents a fundamental step toward the assembly of a biosensor, where immobilization of the selective chemistry on a surface is desired. After immobilizing QD-probe oligonucleotide conjugates on optical fibers, a demonstration of the retention of selectivity was achieved by the introduction of acceptor (Cy3)-labeled single-stranded target oligonucleotides. Hybridization generated the proximity required for FRET, and the resulting fluorescence spectra provided an Analytical Signal proportional to the amount of target. This research provides an important framework for the future development of nucleic acid biosensors based on QDs and FRET. The most important fin...
Omair M Noor - One of the best experts on this subject based on the ideXlab platform.
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paper based solid phase multiplexed nucleic acid hybridization assay with tunable dynamic range using immobilized quantum dots as donors in fluorescence resonance energy transfer
Analytical Chemistry, 2013Co-Authors: Omair M Noor, Ulrich J KrullAbstract:A multiplexed solid-phase nucleic acid hybridization assay on a paper-based platform is presented using multicolor immobilized quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET). The surface of paper was modified with imidazole groups to immobilize two types of QD-probe oligonucleotide conjugates that were assembled in solution. Green-emitting QDs (gQDs) and red-emitting QDs (rQDs) served as donors with Cy3 and Alexa Fluor 647 (A647) acceptors. The gQD/Cy3 FRET pair served as an internal standard, while the rQD/A647 FRET pair served as a detection channel, combining the control and Analytical test zones in one physical location. Hybridization of dye-labeled oligonucleotide targets provided the proximity for FRET sensitized emission from the acceptor dyes, which served as an Analytical Signal. Hybridization assays in the multicolor format provided a limit of detection of 90 fmol and an upper limit of dynamic range of 3.5 pmol. The use of an array of detection zones was designed t...
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paper based solid phase nucleic acid hybridization assay using immobilized quantum dots as donors in fluorescence resonance energy transfer
Analytical Chemistry, 2013Co-Authors: Omair M Noor, Anna Shahmuradyan, Ulrich J KrullAbstract:A paper-based solid-phase assay is presented for transduction of nucleic acid hybridization using immobilized quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET). The surface of paper was modified with imidazole groups to immobilize QD–probe oligonucleotide conjugates that were assembled in solution. Green-emitting QDs (gQDs) were FRET-paired with Cy3 acceptor. Hybridization of Cy3-labeled oligonucleotide targets provided the proximity required for FRET-sensitized emission from Cy3, which served as an Analytical Signal. The assay exhibited rapid transduction of nucleic acid hybridization within minutes. Without any amplification steps, the limit of detection of the assay was found to be 300 fmol with the upper limit of the dynamic range at 5 pmol. The implementation of glutathione-coated QDs for the development of nucleic acid hybridization assay integrated on a paper-based platform exhibited excellent resistance to nonspecific adsorption of oligonucleotides and showed no reducti...
Avinoam Shenhar - One of the best experts on this subject based on the ideXlab platform.
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simultaneous voltammetric determination of uric and ascorbic acids in urine
Talanta, 1997Co-Authors: E M Strochkova, Ya I Turyan, Ilya Kuselman, Avinoam ShenharAbstract:Anodic voltammetric method for simultaneous determination of uric acid (UA) and ascorbic acid (AA) in urine has been developed with the use of a commercial working rotating glassy carbon electrode. UA may be determined in a sample diluted by the buffer supporting electrolyte (HOAc+NH4OH; pH 5.1–5.2) ≈100 times, and AA-in a sample diluted ≈20 times. Before obtaining the Analytical Signal the electrode should be maintained in the diluted sample during 3 min at potential 0 V and the working electrode rotating 100 rpm, for achievement of the adsorption equilibrium of inhibitors from the urine matrix. For UA the electron transfer is close to reversible, for AA it is an irreversible one. Optimal voltammetric techniques are the square-wave for UA and the differential pulse for AA. Calibration curves, detection limits and recoveries for both determinations were evaluated as satisfactory.
E Kirowaeisner - One of the best experts on this subject based on the ideXlab platform.
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trace determination of mercury by anodic stripping voltammetry at the rotating gold electrode
Analytica Chimica Acta, 2000Co-Authors: Y Bonfil, M Brand, E KirowaeisnerAbstract:Abstract A simple and highly reliable method for the determination of mercury on a rotating gold disk electrode is reported. The Signal is linear with concentration over a wide concentration range (0.2–400 nM). The stability of the electrode is excellent. No mechanical polishing between runs is required and a simple electrochemical pretreatment is applied about once in 100 runs. The detection limit in synthetic solutions, applying the subtractive mode of anodic stripping voltammetry (SASV) is 50 pM for a 120 s deposition time at 5000 rpm and 4 nM in urine sample for 180 s deposition time. The reproducibility of the Analytical Signal is better than 2% in solutions containing 1 nM Hg(II). The applicability of the method in urine analysis was demonstrated with the use of certified samples. No interference by lead, copper, cadmium, chromium or selenium was found at concentrations corresponding to their toxic occurrence in urine.