The graphene oxide (GO) modified pencil graphite electrodes (PGEs) were utilized for electrochemical monitoring of microRNA-34a (miRNA-34a) in this study. The GO concentration was firstly optimized after its modification onto the surface of disposable PGE by passive adsorption. The electrochemical behaviour of GO-PGEs was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) as well as microscopic characterization by using scanning electron microscopy (SEM). The impedimetric detection of hybridization between miRNA-34a target and its complementary DNA probe was recognized under the optimum conditions. The selectivity of the impedimetric genosensor was furtherly studied against to other miRNA sequences; such as; miRNA-15a, miRNA-155 and miRNA-660 in PBS (pH 7.40) or fetal bovine serum (FBS): PBS (1:1) diluted solution. (C) 2015 Elsevier Ltd. All rights reserved.