A label-free photoelectrochemical cocaine aptasensor based on an electropolymerized ruthenium-intercalator complex

A photoelectrode was designed by electrodeposition of a pyrrole monomer modified with a polypyridyl Ru(II) complex bearing benzo[i] dipyrido-[3,2-a:2'.3'-c] phenazine (dppn) ligand. Owing to the intercalating properties of these immobilized complexes towards DNA double helix, cocaine aptamer was immobilized on the modified electrodes thanks to its stem-loop configuration in order to design a photoelectrochemical cocaine aptasensor. Especially using a double-fragment aptamer strategy, the binding of cocaine and the formation of the aptamer/cocaine complex was successfully observed and modeled by a Langmuir-Freundlich isotherm, giving access to an apparent dissociation constant K-d of 3.8 mmol L-1. The photoelectrochemical aptasensor exhibits a LOD of 10 nmol L-1 and linear range of 1 10(-8)-5 10(-4) mol L-1. (C) 2016 Elsevier Ltd. All rights reserved.