A novel DNA biosensor was fabricated by modified multilayer of ssDNA, cytochrome C, L-cysteine, metal gold nanoparticles and Chitosan (denoted as ssDNA/Cyt c/L-Cys/GNPs/Chits/GCE). The behavior of the DNA biosensor was then investigated by voltammetry, impedance spectrum and atomic force microscope (AFM), and the morphologic differences among each layer of the DNA biosensor were also observed. Results revealed that two well-defined redox peaks exhibited at 0.120V and 0.362V, and the amount of adsorbed DNA was 1.672 x 10(-10) mol cm(-2). We concluded that the modified electrode could be used to detect DNA with the indicator daunomycin. (C) 2008 Elsevier Ltd. All rights reserved.