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Electrochemical Signal (electrochemical + signal)
Selected AbstractsIn vivo monitor oxidative burst induced by Cd2+ stress for the oilseed rape (Brassica napus L.) based on electrochemical microbiosensorPHYTOCHEMICAL ANALYSIS, Issue 2 2010Qiao Xu Abstract Introduction , Since the mechanism of Cd2+ stress for plants is not clear, an in vivo method to monitor Cd2+ stress for plants is necessary. However, oxidative burst (OB) is a signal messenger in the process of Cd2+ stress for plants. Objective , To establish an electrochemical method with poly- o -phenylenediamine and Pt microparticle modified Pt electrode (POPD,Pt-MP,Pt) as a microbiosensor for the in vivo detection of oxidative burst induced by Cd2+ stress in oilseed rape (Brassica napus L.). Methodology , The optimal fabrication of POPD,Pt-MP,Pt biosensor was achieved. Electrochemical signal was collected by amperometry. Results , After oilseed rape was exposed to 84.9,mM CdCl2 stress, three oxidative bursts were observed in oilseed rape by amperometry at 3.3,h, 8.4,h and 13.2,h, respectively. However, there was no obvious signal observed in the controlled assay. Conclusion , This contribution presents the in vivo monitoring of the OB process induced by Cd2+ stress in oilseed rape by POPD,Pt-MP,Pt microbiosensor in real-time. The novel electrochemical microbiosensor not only facilitates the real-time study in plant self-defence response to the adverse environment such as Cd2+ stress, but also provides an effective tool for probing the self-defence mechanism in plants. Copyright © 2009 John Wiley & Sons, Ltd. [source] Real Time Electrochemical Monitoring of DNA/PNA Dissociation by Melting Curve AnalysisELECTROANALYSIS, Issue 14 2009Xiaoteng Luo Abstract An immobilization-free electrochemical method is reported for real-time monitoring of the DNA hybrid dissociation between a ferrocene labeled peptide nucleic acid (PNA) and a fully-complementary or single-base-mismatched DNA. This method takes advantages of electrostatic charge characteristics and interactions among the neutrally charged PNA, the negatively charged DNA and the negatively charged electrode surface made of indium tin oxide (ITO). When a ferrocene labeled PNA (Fc-PNA) sequence is hybridized to a complementary DNA strand, electrostatic repulsion between the negatively charged PNA/DNA hybrid and the negative ITO surface retards the diffusion of the electroactive Fc to the electrode, resulting in a much reduced electrochemical signal. On the other hand, when the Fc-PNA is dissociated from the hybrid at elevated temperatures, the neutrally charged Fc-PNA easily diffuses to the electrode with an enhanced electrochemical signal. Therefore, an electrochemical melting curve of the Fc-PNA/DNA hybrid can be obtained by measuring the Fc signal with the increasing temperature. This strategy allows monitoring of the dissociation of the DNA hybrid in real time, which might lead to a simple detection method for single nucleotide polymorphism (SNP) analysis. [source] Sensitive Electrochemical Detection of Native and Aggregated ,-Synuclein Protein Involved in Parkinson's DiseaseELECTROANALYSIS, Issue 13-14 2004Michal Masa Abstract The aggregation of ,-synuclein, a 14,kDa protein, is involved in several human neurodegenerative disorders, including Parkinson's disease. We studied native and in vitro aggregated ,-synuclein by circular dichroism (CD), atomic force microscopy (AFM) and electrochemical methods. We used constant current chronopotentiometric stripping analysis (CPSA) to measure hydrogen evolution catalyzed by ,-synuclein (peak H) at hanging mercury drop electrodes (HMDE) and square-wave stripping voltammetry (SWSV) to monitor tyrosine oxidation at carbon paste electrodes (CPE). To decrease the volume of the analyte, most of the electrochemical measurements were performed by adsorptive transfer (medium exchange) from 3,6,,L drops of ,-synuclein samples. With both CPE and HMDE we observed changes in electrochemical responses of ,-synuclein corresponding to protein fibrillization detectable by CD, fluorescence and AFM. Aggregation-induced changes in peak H at HMDE were relatively large in strongly aggregated samples, suggesting that this electrochemical signal may find use in the analysis of early stages of ,-synuclein aggregation. This assumption was documented by marked changes in the peak H potential and height in samples withdrawn at the end of the lag and the beginning of the elongation phase. Native ,-synuclein can be detected down to subnanomolar concentrations by CPSA. [source] Quantum-Dot-Functionalized Poly(styrene- co -acrylic acid) Microbeads: Step-Wise Self-Assembly, Characterization, and Applications for Sub-femtomolar Electrochemical Detection of DNA HybridizationADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Haifeng Dong Abstract A novel nanoparticle label capable of amplifying the electrochemical signal of DNA hybridization is fabricated by functionalizing poly(styrene- co -acrylic acid) microbeads with CdTe quantum dots. CdTe-tagged polybeads are prepared by a layer-by-layer self-assembly of the CdTe quantum dots (diameter,=,3.07,nm) and polyelectrolyte on the polybeads (diameter,=,323,nm). The self-assembly procedure is characterized using scanning and transmission electron microscopy, and X-ray photoelectron, infrared and photoluminescence spectroscopy. The mean quantum-dot coverage is (9.54,±,1.2),×,103 per polybead. The enormous coverage and the unique properties of the quantum dots make the polybeads an effective candidate as a functionalized amplification platform for labelling of DNA or protein. Herein, as an example, the CdTe-tagged polybeads are attached to DNA probes specific to breast cancer by streptavidin,biotin binding to construct a DNA biosensor. The detection of the DNA hybridization process is achieved by the square-wave voltammetry of Cd2+ after the dissolution of the CdTe tags with HNO3. The efficient carrier-bead amplification platform, coupled with the highly sensitive stripping voltammetric measurement, gives rise to a detection limit of 0.52 fmol L,1 and a dynamic range spanning 5 orders of magnitude. This proposed nanoparticle label is promising, exhibits an efficient amplification performance, and opens new opportunities for ultrasensitive detection of other biorecognition events. [source] Stripping Voltammetry at Microdisk Electrode Arrays: TheoryELECTROANALYSIS, Issue 24 2009Abstract Anodic stripping voltammetry (ASV) is an extremely powerful tool for detection of metal ions in solution through a two step process of preconcentration of the metal at the electrode surface, followed by electrodissolution. The second phase produces an electroanalytical response proportional to the amount of material deposited in the first phase. This paper utilizes theory to explore the electrochemical signals produced when considering ASV at a microelectrode or ultramicroelectrode arrays. The theory outlined is applicable mostly to thin mercury film absorption and metal adsorption. [source] Gold electrodes modified with poly(4-aminophenol): incorporation of nitrogenated bases and an oligonucleotidePOLYMER INTERNATIONAL, Issue 4 2008Lucas F Ferreira Abstract BACKGROUND: Investigations of chemical modification of electrode surfaces and immobilization of nitrogenated bases and oligonucleotides are considered essential for the construction of DNA electrochemical nanodevices. Modification of gold electrode surfaces with poly(4-aminophenol) was carried out in order to produce polymers capable of immobilizing purine bases and oligonucleotides. RESULTS: Gold electrodes coated with poly(4-aminophenol) showed improved analytical characteristics and considerably enhanced the electrochemical signals associated with the detection of adenine and guanine by factors of ca 3 and ca 6, respectively, when compared with non-coated gold surfaces. Impedance studies indicated higher charge transfer impedance to modified electrodes containing adenosine monophosphate. Atomic force microscopy images showed that nitrogenated bases have a strong influence over the morphology of the modified electrode surface. It was observed that the modified electrode containing guanine presents globular morphology. CONCLUSION: The modified electrodes increased the amplitude of the current signal of nitrogenated bases when compared to non-coated gold surfaces and produced good response and peaks to the detection of an oligonucleotide. This work presents, for the first time, the electropolymerization of 4-aminophenol on gold electrodes, as well as the detection of nitrogenated bases and an oligonucleotide incorporated on these modified electrodes. Copyright © 2007 Society of Chemical Industry [source] | |||||||||||||