Synergistically improved sensitivity for the detection of specific DNA sequences using polyaniline nanofibers and multi-walled carbon nanotubes composites.

A sensitive electrochemical DNA biosensor was successfully realized on polyaniline nanofibers (PANI), multi-walled carbon nanotubes (MWNT) and chitosan (CHIT) modified carbon paste electrode (CPE) based on the synergistic effect between PANI and MWNT nanoparticles in chitosan film. PANI and MWNT nanocomposites resulted in highly enhanced electron conductive and biocompatible nanostructured film, which was examined by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The immobilization of the probe DNA on the surface of electrode was largely improved due to the unique synergistic effect of PANI and MWNT. The DNA hybridization events were monitored with an EIS label-free detection strategy. Under the optimal conditions, the dynamic detection range of this DNA electrochemical biosensor was from 1.0 x 10(-13) to 1.0 x 10(-7)mol/L and a detection limit of 2.7 x 10(-14)mol/L for the detection of DNA specific sequence of the phosphinothricin acetyltransferase gene (PAT, one of the important screening detection genes for the transgenic plants). Simultaneously, the polymerase chain reaction (PCR) amplification of the terminator of nopaline synthase gene (NOS) from the sample of one kind of genetically modified soybean was also detected satisfactorily.