Aptamer-based electrochemical biosensor for label-free voltammetric detection of thrombin and adenosine

A bifunctional aptamer-based electrochemical biosensor for label-free detection of thrombin and adenosine has been developed. It was based on the principle of switching structures of aptamers from DNA/DNA duplex to DNA/target complex upon target addition. Thrombin aptamer was firstly immobilized on gold electrode surface by self-assembly, and then it was hybridized with adenosine aptamer. Methylene blue (MB), as an electrochemical indicator, was abundantly adsorbed on the aptamers via specific interaction of MB with guanine base. In the presence of thrombin or adenosine, the aptamer part could bind with thrombin or adenosine instead of MB. The decreased peak current of MB was intimately related to the concentration of thrombin or adenosine. In present work, the assay was linear in the ranges from 6 to 60 nM for thrombin and from 10 to 1000 nM for adenosine. Detection limits were determined to be 3 nM for thrombin and 10 nM for adenosine, respectively. Moreover, bovine plasma albumin (BSA) and lysozyme, or uridine and guanosine, did not influence performance of the biosensor, indicating good selectivity of this sensor for thrombin or adenosine detection. Finally, this sensor was successfully applied to thrombin and adenosine analysis in human plasma samples. (C) 2011 Elsevier B.V. All rights reserved.