▎ 摘　　要

A label-free electrochemical DNA sensor was fabricated by deposition of polyaniline and pristine graphene nanosheet (P/Gratios) composites in different mass ratios, DNA probe and bovine serum albumin (BSA) layer by layer on the surface of a glassy carbon electrode (GCE). Electrochemical impedance spectroscopy (EIS) was employed to monitor every step of fabrication of P/Gratio-based DNA sensors and to evaluate the detection results in terms of the hybridization of complementary DNA, mutant DNA and non-complementary DNA. The results illustrate that the P/Gratio-based DNA sensor could highly efficiently detect complementary DNA from 0.01 pm to 1 mu m and discriminate single-nucleotide polymorphisms (SNPs). In the process of detection, double-stranded DNA (dsDNA), resulting from hybridization of a DNA probe, escaping from or remaining on the sensor surface, was monitored by changing the ratio of polyaniline (PANI) to graphene, which was decided by the competition between the electrostatic interaction and Brownian motion.