Reusable Impedimetric Aptasensor

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Abstract
A novel impedimetric aptasensor using a mixed self-assembled monolayer composed of thiol-modified thrombin binding aptamer and 2-mercaptoethanol on a gold electrode is reported. The changes of interfacial features of the electrode were probed in the presence of the reversible redox couple, Fe(CN)63-/4-, using impedance measurements. The electrode surface was partially blocked due to the self-assembly of aptamer or the formation of the aptamer−thrombin complex, resulting in an increase of the interfacial electron-transfer resistance detected by electrochemical impedance spectroscopy or cyclic voltammetry. The aptasensor was regenerated by breaking the complex formed between the aptamer and thrombin using 2.0 M NaCl solution, and the immobilized aptamer subsequently was used for repeated detection of thrombin. The aptamer-functionalized electrode showed a linear response of the charge-transfer resistance to the increase of thrombin concentration in the range of 5.0−35.0 nM and the thrombin was easily detectable to a concentration of 2.0 nM.

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