Highly sensitive electrochemical impedance spectroscopic detection of DNA hybridization based on Au nano–CNT/PAN nano films

Abstract

A polyaniline nanofibers (PAN nano)/carbon paste electrode (CPE) was prepared via dopping PAN nano in the carbon paste. The nanogold (Au nano) and carbon nanotubes (CNT) composite nanoparticles were bound on the surface of the PAN nano/CPE. The immobilization and hybridization of the DNA probe on the Au nano–CNT/PAN nano films were investigated with differential pulse voltammetry (DPV) and cyclic voltammetry (CV) using methylene blue (MB) as indicator, and electrochemical impedance spectroscopy (EIS) using [Fe(CN) 6] 3−/4− as redox probe. The voltammetric peak currents of MB increased dramatically owing to the immobilization of the probe DNA on the Au nano–CNT/PAN nano films, and then decreased obviously owing to the hybridization of the DNA probe with the complementary single-stranded DNA (cDNA). The electron transfer resistance ( R et) of the electrode surface increased after the immobilization of the probe DNA on the Au nano–CNT/PAN nano films and rose further after the hybridization of the probe DNA. The remarkable difference between the R et value at the DNA-immobilized electrode and that at the hybridized electrode could be used for the label-free EIS detection of the target DNA. The loading of the DNA probe on Au nano–CNT/PAN nano films was greatly enhanced and the sensitivity for the target DNA detection was markedly improved. The sequence-specific DNA of phosphinothricin acetyltransferase (PAT) gene and the polymerase chain reaction (PCR) amplification of nopaline synthase (NOS) gene from transgenically modified beans were determined with this label-free EIS DNA detection method. The dynamic range for detecting the PAT gene sequence was from 1.0 × 10 −12 mol/L to 1.0 × 10 −6 mol/L with a detection limit of 5.6 × 10 −13 mol/L.