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• Ocaña, C
• Pacios, M
• del Valle, M
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• Pacios, M
• del Valle, M
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• Ocaña, C
• Pacios, M
• del Valle, M

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Sensors 2012, 12(3), 3037-3048; doi:10.3390/s120303037

Article

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

Cristina Ocaña, Mercè Pacios and Manel del Valle*

Sensors and Biosensors Group, Department of Chemistry, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain

* Author to whom correspondence should be addressed.

Received: 13 January 2012; in revised form: 15 February 2012 / Accepted: 23 February 2012 / Published: 6 March 2012

(This article belongs to the Special Issue Sensors and Biosensors Using Label Free Chemistries)

Download PDF Full-Text [412 KB, uploaded 6 March 2012 11:47 CET]

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.

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

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