A label-free electrochemical aptasensor for the determination of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) was described here, This method was based on the conformational change of 8-OH-dG-aptamer (Apt) in the presence of 8-OH-dG. The G-rich Apt was self-assembled on the surface of gold electrode by Au-S bond. The assembly process of the aptasensor was characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The conformation of Apt changed from flexible single stranded structures to compact G-quadruplex in the presence of 8-OH-dG, which hindered the negatively charged [Fe(CN)(6)](4-) approach to the electrode. The switchable surface provided a sensing platform for the free-label detection of 8-OH-dG. Upon 8-OH-dG binding to the immobilized Apt, a significant decrease in the oxidation current of [Fe(CN)(6)](4-) was observed due to the Apt conformational change. The aptasensor showed a detection limit of 0315 nM and a wide linear range between 1.75 nM and 3.675 mu M for 8-OH-dG. The aptasensor displayed high stability as well as high specificity against uric acid, a strong interferent for the detection of 8-OH-dG. (C) 2015 Elsevier B.V. All rights reserved.