A new type of poly(toluidine blue O)/multiwall carbon nanotube (PTBO/MWNTs) composite nanowires was fabricated by two steps: first, the TBO monomer was assembled onto multiwall carbon nanotubes (MWNTs) to form TBO/MWNTs adduct. Then, the obtained TBO/MWNTs adduct was electropolymerized on a glassy carbon electrode (GCE) surface by cyclic voltammetry. The nanowires modified GCE was characterized with scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The PTBO/MWNTs composite nanowires modified electrode was applied to determinate NADH. Compared with bare GCE and MWNTs modified GCE, the PTBO/MWNTs composite nanowires modified GCE decreased the NADH oxidization overpotential by about 650 mV and 260 mV, respectively, with a much low peak potential at about 0.0 V (vs. SCE). The peak current response at PTBO/MWNTs composite nanowires modified GCE was about 4.5 times higher than that of ultrathin PTBO modified GCE, at the same peak potential. A linear range from 2.0 mu M to 4.5 mM was observed with fast response (within 5 s) and a low detection limit of 0.5 mu M (based on S/N= 3). The current diminution to 1.0 mM NADH is lower than 10% in a period over 70 min shows that the PTBO/MWNTs composite nanowires modified GCE is quite stable. The better electrocatalytic behavior toward NADH oxidation at PTBO/MWNTs composite nanowires modified GCE suggests that the composite nanowires is an excellent platform for electrochemical sensing and biosensing. (c) 2006 Elsevier B.V. All rights reserved.