An ultrasensitive signal-on electrochemical aptasensor via target-induced conjunction of split aptamer fragments

In this paper, we introduced a signal-on electrochemical sensor based on target-induced split aptamer fragments conjunction. To construct the aptasensor, the sequence of the 15-base anti-thrombin DNA aptamer was split into two fragments. one of which was attached to a gold electrode via thiol self-assembled monolayer chemistry and the second of which was modified with the redox moiety ferrocene. Thrombin-induced association of the two fragments thus increased the concentration of ferrocene at the electrode surface, which could be readily monitored via voltammetry. The sensitivity of the proposed electrochemical aptasensor was investigated by differential pulse voltammogram. The results indicated that, in pH 7.1 Tris-HCl buffer solution, the peak current was linear with the concentration of thrombin in the range of 0.8-15 nM with a detection limit of 0.2 nM. The proposed aptasensor has the advantages of higher sensitivity and lower background current. Given the simplicity in design of the proposed electrochemical aptasensor, it is fairly easy to generalize this strategy to detect a spectrum of targets by splitting the aptamers into two suitable segments. Furthermore, this design could be also used to construct novel optical aptasensors. (C) 2009 Elsevier B.V. All rights reserved.