Browsing by Author "Gibson, Timothy D."

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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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    Labeless Immunosensor Assay for Fluoroquinolone Antibiotics Based Upon an AC Impedance Protocol.
    (Taylor & Francis, 2007-01-01T00:00:00Z) Garifallou, Goulielmos-Zois; Tsekenis, Georgios; Davis, Frank; Higson, Seamus P. J.; Millner, Paul A.; Pinacho, Daniel G.; Sanchez-Baeza, Francisco; Marco, M-Pilar; Gibson, Timothy D.
    This paper describes the construction of a labeless immunosensor for the antibiotic ciprofloxacin and its interrogation using an AC impedance protocol. Commercial screen-printed carbon electrodes were used as the basis for the sensor. Polyaniline was electrodeposited onto the sensors and then utilized to immobilize a biotinylated antibody for ciprofloxacin using classical avidin- biotin interactions. Electrodes containing the antibodies were exposed to solutions of antigen and interrogated using an AC impedance protocol. The faradaic component of the impedance of the electrodes was found to increase with increasing concentration of antigen. Control samples containing a non-specific IgG antibody were also studied and calibration curves obtained by subtraction of the responses for specific and non-specific antibody-based sensors, thereby eliminating the effects of non-specific adsorption of antigen.
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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.