A composite film has been prepared by electropolymerization of 2,6-pyridinedicarboxylic acid (PDC) on the platinum electrode and combined with G5.0 poly(amidoamine) dendrimer (PAMAM). Then, a new DNA electrochemical biosensor was developed by immobilizing probe ssDNA on the composite film electrode. The immobilization and hybridization of probe ssDNA were studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry using [Fe(CN)6]3－/4－ as the redox indicator. The experimental results showed that the electron transfer resistance (Ret) of the electrode surface increased after the immobilization of probe ssDNA on the composite film and rose further after the hybridization of the probe ssDNA with its complementary sequence. The remarkable difference between the Ret value at the probe DNA-immobilized electrode and that at the hybridized electrode could be used for label-free EIS detection of the target DNA. The avian virus gene sequences were detected by this DNA electrochemical biosensor. Under optimal conditions, the detection range of the biosensor to avian virus gene target sequences was from 2.0×10－11 to 1.0×10－8 mol•L－1 with the detection limit of 3.6×10−12 mol•L－1, suggesting that the biosensor provides a perfect platform for the sensitive detection of virus gene sequences.

Key words: DNA electrochemical biosensor, impedance spectroscopy, 2,6-pyridinedicarboxylic acid, poly(amidoamine) dendrimer (PAMAM), avian virus gene