Single-walled carbon nanotubes (SWCNT)-poly(vinylferrocenium)(PVF+) modified pencil graphite electrodes (PGEs) were developed in our study for the electrochemical monitoring of a sequence-selective DNA hybridization event. Firstly, SWCNT-PVr modified PGE, PVF+ modified PGE and unmodified PGE were characterized using scanning electron microscopy (SEM). The electrochemical behavior of these electrodes was then investigated using electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The SWCNT-PVF+ modified PGEs were optimized for improved DNA sensing ability by measuring the guanine oxidation signal. In order to obtain the full coverage immobilization of the DNA probe following the optimum working conditions, the effect of amino-linked, thiol-linked and, bare oligonucleotides (ODNs), and the concentration of the DNA probe on the response of the modified electrode were examined. After optimization studies, the sequence-selective DNA hybridization was evaluated in the case of hybridization between an amino-linked probe and its complementary (target), a noncomplementary (NC) sequence, calf thymus double stranded DNA (dsDNA), and target/mismatch (MM) mixtures in the ratio of 1:1. SWCNT-PVF+ modified PGEs presented very effective discrimination of DNA hybridization owing to their superior selectivity and sensitivity. (C) 2011 Elsevier BM. All rights reserved.