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ABSTRACT: Overoxidized polypyrrole (OvoxPpy) doped with gold-nanoparticles (GNP) on a glassy carbon electrode (GCE) was used as a platform to construct a novel label-free impedimetric immunosensor for anti-transglutaminase (anti-tTG). Field emission scanning electron microscopy results confirmed the deposition of GNP with good surface coverage across the OvoxPpy substrate. The average diameter of the nanocomposite was 100 nm. The platform (GNP|OvoxPpy||GCE) was conductive and exhibited reversible electrochemistry (E°’ = 395 mV) in (pH 7.4) PBS. The electrochemical characterization of the platform was studied by cyclic voltammetry (CV) and square wave voltammetry (SWV). OvoxPpy||GCE had a peak separation, ΔE p , value of −80 mV. The GNP|OvoxPpy||GCE showed enhanced interfacial charge transfer with ΔE p , being −30 mV. The SWV results corroborated CV findings which show enhanced peak current through GNP. The immunosensor was prepared by immobilizing 40 μL tTG (0.3 mg mL−1) onto the platform by drop coating. Electrochemical impedance spectroscopy (EIS) measurements indicated that the immunosensor system (BSA|tTG|GNP|OvoxPpy||GCE) markedly improved the conductivity and response of the anti-tTG immunosensor. The impedimetric immunosensor exhibited a charge transfer resistance (Rct)-dependent dynamic linearity of 10−6 to 10−4 M for target anti-tTG (r = 0.9808), and detection limit of 5.22 × 10−6 M.
Analytical Letters 07/2011; 44(11):1956-1966. · 1.02 Impact Factor
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International Journal of Electrochemical Science. 01/2011; 6:1855-1870.
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International Journal of electrochemical Science. 01/2011; 6:1820-1834.
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01/2009; , ISBN: 978-1-60741-7
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ABSTRACT: An aflatoxin B1 (AFB1) electrochemical immunosensor was developed by the immobilisation of aflatoxin B1-bovine serum albumin (AFB1-BSA) conjugate on a polythionine (PTH)/gold nanoparticles (AuNP)-modified glassy carbon electrode (GCE). The surface of the AFB1-BSA conjugate was covered with horseradish peroxidase (HRP), in order to prevent non-specific binding of the immunosensors with ions in the test solution. The AFB1 immunosensor exhibited a quasi-reversible electrochemistry as indicated by a cyclic voltammetric (CV) peak separation (ΔEp) value of 62 mV. The experimental procedure for the detection of AFB1 involved the setting up of a competition between free AFB1 and the immobilised AFB1-BSA conjugate for the binding sites of free anti-aflatoxin B1 (anti-AFB1) antibody. The immunosensor’s differential pulse voltammetry (DPV) responses (peak currents) decreased as the concentration of free AFB1 increased within a dynamic linear range (DLR) of 0.6 - 2.4 ng/mL AFB1 and a limit of detection (LOD) of 0.07 ng/mL AFB1. This immunosensing procedure eliminates the need for enzyme-labeled secondary antibodies normally used in conventional ELISA–based immunosensors.
Sensors. 01/2008;
