Browsing by Author "Law, Karen A."

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    Electrochromic effects from a simple commercial polymer membrane.
    (Elsevier Science B.V., Amsterdam., 2007-08-01T00:00:00Z) Davis, Frank; Law, Karen A.; Bridge, Kerry; Higson, Seamus P. J.
    A simple commercial polyester polymer membrane has been found to exhibit an intense electrochromic effect. Most polymers which undergo electrochromic effects contain either transition metals or extensive conjugated systems. We have found that a simple commercial polyester membrane when coated with gold and polarised to −4 V (versus Ag) in aprotic organic solvents displays an electrochromic colour change from a colourless to an intense red stat
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    Labeless and reversible immunosensor assay based upon an electrochemical current-transient protocol
    (Elsevier Science B.V., Amsterdam., 2003-10-24T00:00:00Z) Grant, Sarah; Davis, Frank; Pritchard, Jeanette A.; Law, Karen A.; Higson, Seamus P. J.; Gibson, Timothy D.
    A novel labeless and reversible immunoassay based upon an electrochemical current-transient protocol is reported which offers many advantages in comparison to classical immuno-biochemical analyses in terms of simplicity, speed of response, reusability and possibility of multiple determinations. Conducting polypyrrole films containing antibodies against 1) Bovine Serum Albumin (BSA) and 2) Digoxin were deposited on the surface of platinum electrodes to produce conductive affinity matrices having clearly defined binding characteristics. The deposition process has been investigated using 125I labelled anti-digoxin to determine optimal fabrication protocols. Antibody integrity and activity, together with non-specific binding of antigen on the conducting matrix have also been investigated using tritiated digoxin to probe polypyrrole/anti-digoxin films. Amperometric responses to digoxin were recorded in flow conditions using these films, but the technique was limited in use mainly due to baseline instability. Anti-BSA - polypyrrole matrices were investigated in more detail in both flow and quiescent conditions. No observable response was found in flow conditions, however under quiescent conditions (in non-stirred batch cell), anti-BSA – polypyrrole films have been demonstrated to function as novel quantitative chronoamperometric immuno-biosensors when interrogated using a pulsed potential waveform. The behaviour of the electrodes showed that the antibody/antigen binding and/or interaction process underlying the response observed was reversible in nature, indicating that the electrodes could be used for multiple sensing protocols. Calibration profiles for BSA demonstrated linearity for a concentration range of 0-50 ppm but tended towards a plateau at higher concentrations. Factors relating to replicate sensor production, sample measurement and reproducibility are discusse
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    New Techniques in Monitoring Water Pollution - Development of Sonochemically Fabricated Microarrays for the Determination of Pollutants.
    (Teknoscienze Srl, 2007-01-01T00:00:00Z) Davis, Frank; Collyer, Stuart D.; Gornall, Davinia D.; Law, Karen A.; Mills, Daniel W.; Higson, Seamus P. J.
    The focus of this article is to describe a simple-to-use, disposable sensor suitable for the rapid determination of pollutants in aqueous media, utilising a novel sonochemical microelectrode fabrication technique. The use of screen- printing, electrochemical and sonochemical methods allows the production of microelectrode arrays capable of stir-independent determination of chlorine in water. These arrays permit the simultaneous measurement of free and total chlorine at concentrations between 0-20 ppm. Developments leading to production on a mass scale will be briefly discussed. A further system incorporating enzyme containing conductive polymers to give microelectrode arrays capable of detection of ultra-low levels of organophosphate pesticides will also be described. Acetylcholine esterase could be entrapped within conductive polyaniline protrusions and the effects of pesticides on its activity determined. Ultra low concentrations of pesticide were found to reduce the enzymes activity as measured electrochemically. These systems allow the detection of organophosphates at concentrations as low as (10-17 M).
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    Procedure 24 : Construction of an enzyme-containing microelectrode array and use for detection of low levels of pesticides
    (2007-01-01T00:00:00Z) Davis, Frank; Law, Karen A.; Turner, Anthony P. F.; Higson, Seamus P. J.
    Objectives (a) To construct a microelectrode array based on a screen printed substrate. (b) To utilise the microelectrode array to form an array of enzyme- containing electrodes (c) To test the electrode response to thiocholine (d) To expose the array to low levels of pesticide and measure the relative response to thiocholine following inhibition.
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    Sonochemically fabricated microelectrode arrays for biosensors offering widespread applicability. Part I
    (Elsevier Science B.V., Amsterdam., 2004-09-15T00:00:00Z) Barton, Andrew C.; Collyer, Stuart D.; Davis, Frank; Gornall, Davinia D.; Law, Karen A.; Lawrence, Emma C. D.; Mills, Daniel W.; Myler, Suzy; Pritchard, Jeanette A.; Thompson, Mark; Higson, Seamus P. J.
    A novel and patented procedure is described for the sonochemical fabrication of a new class of microelectrode array based sensor with electrode element populations of up to 2 x 105 cm-2. For some years it has been accepted that microelectrode arrays offer an attractive route for lowering minimum limits of detection and imparting stir (convectional mass transport) independence to sensor responses; despite this no commercial biosensors, to date, have employed microelectrode arrays, largely due to the cost of conventional fabrication routes that have not proved commercially viable for disposable devices. Biosensors formed by our sonochemical approach offer unrivalled sensitivity and impart stir independence to sensor responses. This format lends itself for mass fabrication due to the simplicity and inexpensiveness of the approach; in the first instance impedimetric and amperometric sensors are reported for glucose as model systems. Sensors already developed for ethanol, oxalate and a number of pesticide determinations will be reported in subsequent publications.
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    Ultra-Sensitive determination of pesticides via cholinesterase-based sensors for environmental analysis.
    (Elsevier, 2007) Davis, Frank; Law, Karen A.; Chaniotakis, Nikos A.; Fournier, Didier; Gibson, Timothy D.; Millner, Paul A.; Marty, Jean-Louis; Sheehan, Michelle A.; Ogurtsov, Vladimir I.; Johnson, Graham; Griffiths, John; Turner, Anthony P. F.; Higson, Seamus P. J.
    This review is focussed towards the development of acetylcholinesterase enzymatic based biosensors for the quantification of trace concentrations of highly toxic pesticides via their inhibitory effect on the enzyme. Initial results were obtained using wild-type enzymes which have a broad spectrum of susceptibility to a variety of pesticides. The sensitivity and selectivity of the enzyme activity was improved by development and screening of a wide range of mutant enzymes. Optimal enzymes were then exploited within a range of sensor formats. A range of immobilisation techniques including adsorption based approaches, binding via proteins and entrapment within conducting polymers were all studied. The incorporation of stabilisers and co-factors were utilised to optimise electrode performance and stability - with both planar and microelectrode geometries being developed. Reproducible quantification of pesticides could be obtained at concentrations down to 10-17 M, representing a detection limit hitherto unavailable.