Browsing by Author "Tsekenis, Georgios"

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    Labeless AC impedimetric antibody-based sensors with pg ml-1 sensitivities for point-of-care biomedical applications.
    (Elsevier Science B.V., Amsterdam., 2009-01-01T00:00:00Z) Barton, Andrew C.; Collyer, Stuart D.; Davis, Frank; Garifallou, Goulielmos-Zois; Tsekenis, Georgios; Tully, Elizabeth; O'Kennedy, Richard; Gibson, Tim; Millner, Paul A.; Higson, Seamus P. J.
    This paper describes the development and characterisation of labeless immunosensors for (a) the cardiac drug digoxin and (b) bovine serum albumin (BSA). Commercial screen-printed carbon electrodes were used as the basis for the sensors. Two methods were used to immobilise antibodies at the electrode surface. Aniline was electropolymerised onto these electrodes to form a thin planar film of conductive polyaniline; the polyaniline film was then utilised as a substrate to immobilise biotinylated anti-digoxin using a classical avidin- biotin affinity approach. As an alternative approach, poly(1,2-diaminobenzene) was electrodeposited onto the carbon electrodes and this modified surface was then sonochemically ablated to form an array of micropores. A second electropolymerisation step was then used to co-deposit conductive polyaniline along with antibodies for BSA within these pores to produce a microarray of polyaniline protrusions with diameters of several μm, containing entrapped anti- BSA
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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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    Studies towards the development of label-free AC impedimetric immunosensors for healthcare and food quality control
    (Cranfield University, 2008-03) Tsekenis, Georgios; Higson, Seamus P. J.
    This thesis describes work focused towards the fabrication and characterisation of immunosensor platforms for the label-free detection of analytes of importance in the health and food industries. Due to their low unit cost and ease of fabrication, the immunosensor market has significantly increased recently, resulting in a constant demand for new immunosensor applications. Within this thesis, therefore, a novel fabrication protocol is reported towards the production of immunosensor platforms for the detection of the antibiotic, ciprofloxacin, the stroke and multiple sclerosis marker, Myelin Basic Protein (MBP) and the ovarian cancer marker CA-125. Initial investigations were aimed towards the electrochemical characterization of the available electrode substrates at the onset of this research project namely, gold sputter coated, screen-printed gold and carbon electrodes. They showed that only carbon electrodes provide sufficiently reproducible results and thus these electrodes have been employed for immunosensor fabrication. Due to the advantages of microelectrodes over planar electrodes, attempts to fabricate microelectrode arrays were also made via the ultrasonic ablation of passivated electrode assemblies. For the site-specific immobilisation of antibodies on polymer modified surfaces biotin-neutravidin affinity technologies were used. The fabricated immunosensors were then interrogated upon exposure to antigen solutions utilising the technique of electrochemical impedance spectroscopy (EIS). Changes in the obtained impedance spectra were used to plot calibration profiles for the detection of ciprofloxacin in buffer and in milk. Similar profiles have been plotted for Myelin Basic Protein (MBP) and the ovarian cancer marker CA-125.