▎ 摘　　要

Here, we developed a new, sensitive electrochemical deoxyribonucleic acid (DNA) biosensor to detect specific target sequences. The biosensor was constructed using a modified nanocomposite consisting of three-dimensional (3D) nitrogen-doped graphene (NG) and Fe3O4 nanoparticles. These 3D NG-Fe3O4 nanoparticles formed a unique sensing film with strong synergistic effects; the highly porous 3D NG provided a large surface area, whereas Fe3O4 was uniformly deposited on the 3D graphene hydrogel (GH), facilitating electron transfer for sensitive detection of DNA with excellent selectivity, fast responses, and a low detection limit. Immobilization of the probe ssDNA sequences on the electrode was greatly improved owing to the unique synergistic effects of 3D NG and Fe3O4. Differential pulse voltammetry (DPV) was used to survey the DNA hybridization event with methylene blue (MB) as an electrochemical indicator. Under optimal conditions, the proposed biosensor could detect target DNA concentrations down to 3.63 x 10(-15) M (signal/noise ratio of 3) with a linear range from 1.0 x 10(-14) to 1.0 x 10(-6) M, showing high sensitivity. The detection capability of this DNA biosensor in complicated serum samples was also studied. Thus, our biosensor presented a sensitive, simple, and rapid platform for DNA detection and may provide a powerful and versatile tool for medical diagnosis of genetic diseases and mutations. (C) 2016 Published by Elsevier B.V.