A solid-state electrochemiluminescence biosensing switch for detection of thrombin based on ferrocene-labeled molecular beacon aptamer

A solid-state electrochemiluminescence (ECL) biosensing switch system based on special ferrocene-labeled molecular beacon aptamer (Fc-MBA) has been developed successfully for thrombin detections. Such special switch system includes two main parts, an ECL substrate and an ECL intensity switch. The ECL substrate was made by modifying the complex of Au nanoparticle and Ruthenium (II) tris-(bipyridine) (Ru(bpy)(3)(2+)-AuNPs) onto Au electrode. A molecular beacon aptamer labeled by ferrocene acted as the ECL intensity switch. The loop bases of the ECL intensity switch are designed with special anti-thrombin aptamer sequence which could be combined with its target protein via the reaction between aptamer and thrombin. During the reactions, the molecular beacon aptamer opened its stem-loop, and the labeled Fc was consequently kept away from the ECL substrate. Such structural change resulted in an obvious ECL intensity increment due to the decreased quenching effect of Fc to the ECL substrate. The analytic results are sensitive and specific. (C) 2009 Elsevier B.V. All rights reserved.