In this study, we developed a superoxide anion biosensor based on Pt nanoparticles covalently bonded to the multi-walled carbon nanotubes (MWCNTs-Pt) and poly-diallyldimethylammonium chloride (PDDA) on a glassy carbon electrode (GCE) without enzyme. The MWCNTs-Pt film was characterized with transmission electron microscopy and X-ray photoelectron spectroscopy. The mechanism of the reduction of superoxide anion at PDDA/MWCNTs-Pt/GCE was determined to be an irreversible diffusion-controlled electrode process. The electrocatalytic properties of the MWCNTs-Pt catalyst for superoxide anion reduction were investigated by cyclic voltammetry and chronoamperometry. Good sensitivity, wide linear range, low detection limit, good reproducibility and excellent storage stability were obtained by using the amperometric response. In the study results, the proposed electrode displayed better electrocatalytic activity than the previously reported electrodes toward the dismutation of superoxide. (c) 2012 Elsevier Ltd. All rights reserved.