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J. Justin Gooding - One of the best experts on this subject based on the ideXlab platform.

  • Determination of sulfite in beer samples using an amperometric fill and flow channel biosensor employing sulfite oxidase
    Analytica Chimica Acta, 2006
    Co-Authors: Min Zhao, D. Brynn Hibbert, J. Justin Gooding
    Abstract:

    A simple method is described to determine sulfite in beer samples using a fill and flow channel biosensor. A droplet of sample is placed into the inlet of a rectangular flow cell and begins to flow through the channel by capillarity. The flow is maintained and controlled by a porous outlet plug of defined porosity. In a rectangular flow cell, the sample solution flows through three consecutive zones: over a predictor electrode, an Enzyme Layer and a detector electrode. Together these three zones enable the differentiation between current due to sulfite and current due to other electroactive species in the sample. The predictor electrode is located upstream, and on the opposite channel wall to the Enzyme Layer and detector electrode, and is poised at the same potential (+0.65 V versus Ag/AgCl) as the detector electrode. On this electrode, the current contribution from all species in the sample solution that are oxidized at that potential is determined. The Enzyme Layer contains sulfite oxidase, which, in the process of oxidizing sulfite, produces hydrogen peroxide, which itself is reduced by excess sulfite. The current at the downstream detector electrode is therefore different from that at the predictor electrode as a result of the Enzyme reaction and the difference of the currents, corrected for the dimensions of the electrodes, is proportional to the concentration of sulfite. The method enables a straightforward correction of the interfering current at the detector electrode and a determination of the analyte concentration. The effect of interferences from ascorbic acid, ethanol, sorbic acid and tartaric acid in the detection of sulfite is efficiently removed. The concentration of sulfite in a sample of beer measured by the biosensor is equivalent to that measured using a reference method based on the AOAC-recommended Monier-Williams method.

  • Which Parameters Affect the Response of the Channel Biosensor
    Electroanalysis, 2003
    Co-Authors: Dusan Losic, Min Zhao, Joseph G. Shapter, J. Justin Gooding
    Abstract:

    The important parameters in defining the response of the portable channel biosensor described previously are explored by connecting the portable flow cell to a gravity feed flow system and using a highly defined Enzyme immobilization protocol which ensures the Enzyme reaction is a surface reaction. The Enzyme glucose oxidase (GOD) was immobilized by covalent attachment to a self-assembled monoLayer modified gold surface. As a glucose solution flowed down the rectangular duct defined by the flow cell, it passed over the Enzyme Layer where the Enzyme reaction produced hydrogen peroxide. The hydrogen peroxide was swept further downstream to the detector electrode. The response of such an Enzyme electrode was shown to be limited by mass transport of the cosubstrate oxygen to the Enzyme Layer. Increasing the amount of oxygen in the sample meant the response of the biosensor became limited by the Enzyme kinetics. The influence of parameters such as flow rate, height of the channel, Enzyme Layer length and the gap between the Enzyme Layer and the detector electrode were explored.

  • An oxygen-rich fill-and-flow channel biosensor.
    Biosensors and Bioelectronics, 2003
    Co-Authors: Min Zhao, D. Brynn Hibbert, J. Justin Gooding
    Abstract:

    An oxygen-rich fill-and-flow channel biosensor has been developed for the measurement of glucose in wine. Glucose oxidase (GOD), immobilised in carbon paste (CP), was located in a well adjacent to a downstream detector electrode. When the analyte solution flows, hydrogen peroxide produced in the Enzyme reaction is swept down to the detector electrode. Mineral oil and Kel-F oil (poly(chlorotrifluorethylene)) were used to prepare an Enzyme Layer of GOD within a CP. The hydrophobicity of the CP confined the reaction between the Enzyme and its substrate to the surface of the Enzyme Layer. The oxidation current of hydrogen peroxide was sensitive to the Enzyme loading but insensitive to mass transport variations such as flow rate. This response was, therefore, limited by the kinetics of the reaction between the Enzyme and the substrate. For Kel-F oil, which can support a high concentration of dissolved oxygen, good reproducibility and greater dynamic range was obtained and the response did not decrease after degassing for 40 min with argon. Analysis of wine samples showed good agreement with the values obtained by spectrophotometric Enzyme assay.

  • A SIMPLE MODEL FOR AN AMPEROMETRIC CHANNEL BIOSENSOR
    Electrochemistry Communications, 1999
    Co-Authors: J. Justin Gooding
    Abstract:

    Abstract A simple model is presented for the channel biosensor where an oxidase Enzyme Layer is located upstream of a detector electrode. In this model the Enzyme kinetics are restricted to the linear region. The model enables the elucidation of the parameters important in tuning the response of the biosensor. Two extreme regimes of operation are identified; the kinetically limited and mass transport limited regimes both provide features which overcome reproducibility problems associated with the classical Enzyme electrode geometry.

  • From Thick Films to MonoLayer Recognition Layers in Amperometric Enzyme Electrodes
    Electroanalysis, 1998
    Co-Authors: J. Justin Gooding, Elizabeth A. H. Hall, D. Brynn Hibbert
    Abstract:

    Theoretical models of the conventional thick-film Enzyme electrode and monoLayer electrodes are used to determine the important parameters in defining the response of both types of biosensors with regard to their reproducible fabrication. The response of the thick-film biosensors are very sensitive to the thickness of the Enzyme Layer and therefore highly precise methods of depositing the Enzyme Layer are required if reproducible biosensors are to be manufactured. Covalent attachment of an Enzyme to a monoLayer of alkanethiols self-assembled onto a gold electrode could potentially provide this more precise fabrication method. A model for monoLayer Enzyme electrodes gives an excellent fit to an experimental calibration plot for a monoLayer of glucose oxidase attached to a self-assembled monoLayer. The model showed the response was highly dependent on the amount of Enzyme immobilized and therefore the reproducibility of monoLayer Enzyme electrodes will be limited by the reproducibility of the Enzyme immobilization. The model predicts the response of the monoLayer biosensor is limited by the turnover rate of the Enzyme rather than the supply of substrate as is the case with thick-film biosensors.

Christopher M. A. Brett - One of the best experts on this subject based on the ideXlab platform.

  • Characterisation of poly(neutral red) modified carbon film electrodes; application as a redox mediator for biosensors
    Journal of Solid State Electrochemistry, 2007
    Co-Authors: Rasa Pauliukaite, Mariana Emilia Ghica, Madalina Barsan, Christopher M. A. Brett
    Abstract:

    The polymer redox mediator, poly(neutral red) (PNR), has been synthesised and characterised electrochemically to investigate the best electropolymerisation and mediation conditions for application in Enzyme biosensors and to clarify the mechanism of action. Neutral red was electropolymerised by potential cycling on carbon film electrode substrates by allowing the monomer to be oxidised during the full 20 cycles of polymerisation or reducing the positive limit of the potential window after the first 2 cycles to impede monomer oxidation with a view to obtaining longer polymer chains and a lesser degree of branching. Comparison was made with glassy carbon substrates. The PNR films on carbon film electrodes were characterised using cyclic voltammetry and electrochemical impedance spectroscopy, as well as in glucose biosensors prepared with PNR. Glucose oxidase Enzyme was immobilised by encapsulation in silica sol-gel and compared with that obtained by cross-linking with glutaraldehyde. The biosensors were evaluated by chronoamperometry in 0.1 M phosphate buffer saline solution, pH 7.0, and showed evidence of electron transfer between the Enzyme cofactor flavin adenine dinucleotide and PNR dissolved in the Enzyme Layer competing with PNR-mediated electrochemical degradation of H_2O_2 formed during the enzymatic process.

  • development and evaluation of electrochemical glucose Enzyme biosensors based on carbon film electrodes
    Talanta, 2005
    Co-Authors: Monica Florescu, Christopher M. A. Brett
    Abstract:

    Abstract Electrochemical glucose Enzyme biosensors have been prepared on carbon film electrodes made from carbon film electrical resistors. Evaluation and characterisation of these electrodes in phosphate buffer saline solution has been carried out with and without pretreatment by cycling in perchloric acid or at fixed applied potential. Both pretreatments led to a reduction in the carbon surface oxidation peak and enabled better detection of hydrogen peroxide in the pH range of 5–7. Glucose oxidase Enzyme was immobilised on the carbon surface by mixing with glutaraldehyde, bovine serum albumin and with and without Nafion. The performance of these two types of electrode was similar, that containing Nafion being more physically robust. Linear ranges were up to around 1.5 mM, with detection limits 60 μM, and pretreatment of the carbon film electrode at a fixed potential of +0.9 V versus SCE for 5 min was found to be the most beneficial. Michaelis–Menten constants between 5 mM and 10 mM were found under the different experimental conditions. Coating the immobilised Enzyme Layer with a thin Layer of Nafion was found to give similar results in the determination of glucose to mixing it but with benefits against interferences for the analysis of complex matrices, such as wine. Potentialities, for a short-term-use or disposable sensors, are indicated.

Elisabeth Lojou - One of the best experts on this subject based on the ideXlab platform.

  • efficiency of enzymatic o2 reduction by myrothecium verrucaria bilirubin oxidase probed by surface plasmon resonance pmirras and electrochemistry
    ACS Catalysis, 2016
    Co-Authors: Cristina Gutierrezsanchez, Alexandre Ciaccafava, Pierre Yves Blanchard, Karen Monsalve, Marie Therese Giudiciorticoni, Sophie Lecomte, Elisabeth Lojou
    Abstract:

    Deciphering which parameters control the immobilization of Enzymes on solid supports is essential for the development of biotechnological devices such as biosensors, bioreactors, and enzymatic fuel cells. In this work, we used surface plasmon resonance (SPR) coupled with electrochemistry and polarization modulated infrared reflection absorption spectroscopy (PMIRRAS) to correlate the loading, the conformation, and the activity of Myrothecium verrucaria bilirubin oxidase (Mv BOD) Enzymes immobilized on two oppositely charged self-assembled monoLayers (SAMs) on gold electrodes. The SPR signal showed that an Enzyme Layer close to a monoLayer was formed by spontaneous adsorption on both negatively and positively charged SAMs. A different catalytic process for O2 reduction was obtained, however, being a direct catalysis at negative interfaces and a mediated catalysis at positive interfaces, in relation to the charge of the amino acids surrounding the surface of the Cu T1 and the dipole moment direction of Mv B...

Elizabeth A. H. Hall - One of the best experts on this subject based on the ideXlab platform.

  • From Thick Films to MonoLayer Recognition Layers in Amperometric Enzyme Electrodes
    Electroanalysis, 1998
    Co-Authors: J. Justin Gooding, Elizabeth A. H. Hall, D. Brynn Hibbert
    Abstract:

    Theoretical models of the conventional thick-film Enzyme electrode and monoLayer electrodes are used to determine the important parameters in defining the response of both types of biosensors with regard to their reproducible fabrication. The response of the thick-film biosensors are very sensitive to the thickness of the Enzyme Layer and therefore highly precise methods of depositing the Enzyme Layer are required if reproducible biosensors are to be manufactured. Covalent attachment of an Enzyme to a monoLayer of alkanethiols self-assembled onto a gold electrode could potentially provide this more precise fabrication method. A model for monoLayer Enzyme electrodes gives an excellent fit to an experimental calibration plot for a monoLayer of glucose oxidase attached to a self-assembled monoLayer. The model showed the response was highly dependent on the amount of Enzyme immobilized and therefore the reproducibility of monoLayer Enzyme electrodes will be limited by the reproducibility of the Enzyme immobilization. The model predicts the response of the monoLayer biosensor is limited by the turnover rate of the Enzyme rather than the supply of substrate as is the case with thick-film biosensors.

  • An Enzyme electrode with response independent of the thickness of the Enzyme Layer
    Sensors and Actuators B: Chemical, 1996
    Co-Authors: J. Justin Gooding, M. Hämmerle, Elizabeth A. H. Hall
    Abstract:

    The common biosensor geometry where the immobilisation matrix is cast directly over the electrode has been shown, using a numerical model, to be highly sensitive to the thickness of the biorecognition Layer. An alternative geometry where a permeable electrode is located on the solution side of the matrix, such that the substrates must pass through the electrode before being able to react with the Enzyme, was shown to give a thickness independent response. The theoretical conclusions for this geometry appear to be verified by initial experimental results. The alternative geometry was successfully employed in the development of an electrochemical formaldehyde biosensor.

  • Redox Enzyme linked electrochemical sensors: Theory meets practice
    Microchimica Acta, 1995
    Co-Authors: Elizabeth A. H. Hall, J. Justin Gooding, Carl E. Hall
    Abstract:

    Information from theoretical models of redox Enzyme linked biosensors highlights the importance of membrane thickness and Enzyme loading on signal response in regard to both sensitivity and reproducibility. The conclusions are substantiated by examination of practical examples in the literature and, with a view to the importance of the character of the Enzyme Layer and overLayers, immobilization techniques are assessed which are in current use.

  • An assessment of mediators as oxidants for glucose oxidase in the presence of oxygen
    Biosensors and Bioelectronics, 1995
    Co-Authors: Nicolas Martens, Alistair A. Hindle, Elizabeth A. H. Hall
    Abstract:

    Abstract Amperometric Enzyme electrodes often employ a redox mediator to act as an electron shuttle between the Enzyme and the electrode. In this study we discuss the influence of oxygen on the current response mediated either by a ferrocene derivative or by diaminodurene (DAD), a novel mediator for glucose oxidase electrodes. A reaction model, which describes an Enzyme reoxidation competition between oxygen and the mediator, is investigated and a model which excludes concentration polarisation in the Enzyme Layer is eliminated.

  • Model for an immobilized oxidase Enzyme electrode in the presence of two oxidants
    Analytical Chemistry, 1994
    Co-Authors: Nicolas Martens, Elizabeth A. H. Hall
    Abstract:

    In mediated oxidase electrodes, the artificial electron acceptor competes with oxygen for the reoxidation of the Enzyme. A steady-state model for a three-substrate electrode is employed to investigate the influence of oxygen on the current response of an amperometric Enzyme electrode and concentration profiles predicted in the Enzyme Layer for the substrates. The model predicts the electrode response for different O 2 levels, and the influence of model parameters on the electrode performance is tested and discussed with the view of improved sensor design

Michael V. Pishko - One of the best experts on this subject based on the ideXlab platform.

  • characterization of oxidoreductase redox polymer electrostatic film assembly on gold by surface plasmon resonance spectroscopy and fourier transform infrared external reflection spectroscopy
    Analytica Chimica Acta, 2002
    Co-Authors: Aleksandr Simonian, Jerry Elkind, Alexander Revzin, James R Wild, Michael V. Pishko
    Abstract:

    The electrostatic assembly of nanocomposite thin films consisting of alternating Layers of an organometallic redox polymer (RP) and oxidoreductase Enzymes, glucose oxidase (GOX), lactate oxidase (LOX) and pyruvate oxidase (PYX), was investigated. MultiLayer nanostructures were fabricated on gold surfaces by the deposition of an anionic self-assembled monoLayer of 11-mercaptoundecanoic acid, followed by the electrostatic attachment of a cationic RP, poly(vinylpyridine Os(bis-bipyridine)2Cl-co-allylamine) (PVP-Os-AA), and anionic oxidoreductase Enzymes. Surface plasmon resonance (SPR) spectroscopy, Fourier transform infrared external reflection spectroscopy (FT-IR–ERS) and electrochemistry were employed to characterize the assembly of these nanocomposite films. The surface concentration of GOX was found to be 2.4 ng/mm 2 for the first Enzyme Layer and 1.96 ng/mm 2 for the second Enzyme Layer, while values of 10.7 and 1.3 ng/mm 2 were obtained for PYX and LOX, respectively. The apparent affinity constant for GOX adsorption was found to be 8 × 10 7 M −1 . FT-IR–ERS was used to verify the incorporation of GOX and its conformational stability inside of these nanocomposite thin films. An SPR instrument with a flow-through cell was modified by additions of Ag/AgCl reference and Pt counter electrodes, with the gold-coated SPR surface film serving as the working electrode. This enabled real-time observation of the assembly of sensing components and immediate, in situ electrochemical verification of substrate-dependent current upon the addition of Enzyme to the multiLayer structure. A glucose-dependant amperometric response with sensitivity of 0.197 A/cm 2 /mM for a linear range of 1–10 mM of glucose was obtained. The SPR and FT-IR–ERS studies also showed no desorption of polymer or Enzyme from the nanocomposite RP–GOX structure when stored in aqueous environment occurred over the period of 3 weeks, suggesting that decreasing substrate sensitivity with time was due to loss of enzymatic activity rather than loss of film compounds from the nanostructure. © 2002 Elsevier Science B.V. All rights reserved.