A novel electrochemical aptasensor based on H-shape structure of aptamer-complimentary strands conjugate for ultrasensitive detection of cocaine

Cocaine is one of the most commonly abused stimulant which could affect the central nervous system. In this work, an electrochemical aptasensor was designed for sensitive and selective detection of cocaine, based on complimentary strands of aptamer (CSs), H-shape structure of Aptamer (Apt)-CSs conjugate and gold electrode. This aptasensor inherits properties of gold such as high electrochemical conductivity and large surface area, as well as high selectivity and sensitivity of aptamer toward its target and property of H-shape structure of Apt-CSs conjugate to act as a gate for the access of redox probe to the surface of electrode. In the absence of cocaine, the gate is closed, so that the electrochemical signal is weak. In the presence of cocaine, aptamer binds to target, leaves the surface of electrode and the gate is opened, leading to a strong electrochemical signal. The fabricated electrochemical aptasensor exhibited good selectivity toward cocaine with a limit of detection (LOD) as low as 0.228 nM. Furthermore, the designed aptasensor was successfully used to detect cocaine in serum with a LOD as low as 0.273 nM. (C) 2015 Elsevier B.V. All rights reserved.