Freely switchable impedimetric detection of target gene sequence based on synergistic effect of ERGNO/PANI nanocomposites.

An impedimetric and freely switchable DNA sensor based on electrochemically reduced graphene oxide (ERGNO) and polyaniline (PANI) film was presented, where ERGNO was prepared on PANI modified glassy carbon electrode (GCE). When the probe DNA was noncovalently assembled on the surface of electrode through π-π* stacking between the ring of nucleobases and the rich-conjugated structure of the nanocomposite, the electron transfer resistance value of [Fe(CN)₆]³⁻/⁴⁻ increased. The negative ssDNA and the steric hindrance blocked the effective electron transfer channel of the [Fe(CN)₆]³⁻/⁴⁻. After hybridization with the complementary DNA, the formation of helix induced dsDNA to release from the surface of conjugated nanocomposite, accompanied with the curtailment of the impedimetric value. The selectivity and sensitivity of this DNA sensing platform were characterized using electrochemical impedance spectroscopy in detail. The fabricated biosensor exhibited excellent performance for the detection of specific DNA sequence with a wide linear range (1.0×10⁻¹⁵ to 1.0×10⁻⁸ mol/L) and a low detection limit of 2.5×10⁻¹⁶ mol/L due to the synergistic effect of ERGNO/PANI nanocomposites. The hosphinothricin acetyltransferase gene (PAT) was also detected to show the switchable ability of ERGNO/PANI.