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A Reusable Impedimetric Aptasensor for Detection of Thrombin Employing a Graphite-Epoxy Composite Electrode

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Author(s): Cristina Ocaña | Mercè Pacios | Manel del Valle

Journal: Sensors
ISSN 1424-8220

Volume: 12;
Issue: 3;
Start page: 3037;
Date: 2012;
Original page

Keywords: aptamer | thrombin | electrochemical impedance spectroscopy | labeless | adsorption

ABSTRACT
Here, we report the application of a label-free electrochemical aptasensor based on a graphite-epoxy composite electrode for the detection of thrombin; in this work, aptamers were immobilized onto the electrodes surface using wet physical adsorption. The detection principle is based on the changes of the interfacial properties of the electrode; these were probed in the presence of the reversible redox couple [Fe(CN)6]3−/[Fe(CN)6]4− using impedance measurements. The electrode surface was partially blocked due to formation of aptamer-thrombin complex, resulting in an increase of the interfacial electron-transfer resistance detected by Electrochemical Impedance Spectroscopy (EIS). The aptasensor showed a linear response for thrombin in the range of 7.5 pM to 75 pM and a detection limit of 4.5 pM. The aptasensor was regenerated by breaking the complex formed between the aptamer and thrombin using 2.0 M NaCl solution at 42 °C, showing its operation for different cycles. The interference response caused by main proteins in serum has been characterized.
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