A DNA electrochemical sensor based on nanogold-modified poly-2,6-pyridinedicarboxylic acid film and detection of PAT gene fragment.

A new DNA electrochemical biosensor is described for electrochemical impedance spectroscopy (EIS) detection of the sequence-specific DNA related to PAT transgene in the transgenic plants. Poly-2,6-pyridinedicarboxylic acid film (PDC) was fabricated by electropolymerizing 2,6-pyridinedicarboxylic acid on the glassy carbon electrode (GCE). The gold nanoparticles (NG) were modified on the PDC/GCE to prepare NG/PDC/GCE, and then DNA probe (ssDNA) was immobilized on the NG/PDC/GCE by the interaction of NG with DNA. The immobilization of NG and the immobilization and hybridization of DNA probe were characterized with differential pulse voltammetry (DPV) and cyclic voltammetry (CV) using methylene blue (MB) as indicator and EIS. MB had a couple of well-defined CV peaks at the NG/PDC/GCE, and these redox peak currents increased after the immobilization of the DNA probe. After the hybridization of the DNA probe with the complementary single-stranded DNA (cDNA), the redox peak currents of MB decreased greatly. The electron transfer resistance (R(et)) of the electrode surface in EIS in Fe(CN)(6) solution increased after the immobilization of the DNA probe on the NG/PDC/GCE. The hybridization of the DNA probe with cDNA made R(et) increase further. EIS was used for the label-free detection of the target DNA. The NG modified on the PDC dramatically enhanced the immobilization amount of the DNA probe and greatly improved the sensitivity of DNA detection. The difference between the R(et) value at the ssDNA/NG/PDC/GCE and that at hybridization DNA-modified electrode (dsDNA/NG/PDC/GCE) was used as the signal for detecting the PAT gene fragment with the dynamic range from 1.0x10(-10) to 1.0x10(-5)mol/L. A detection limit of 2.4x10(-11)mol/L could be estimated.