In this paper, a type of direct
DNA impedance detection using the self-redox signal change of sulfonated
polyaniline (SPAN) enhanced by
graphene oxide (GNO) was reported, here SPAN is a copolymer obtained from
aniline and m-aminobenzenesulfonic
acid. The resulting nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The π-π planar structure of GNO and the carboxyl groups on the surface of GNO ensured it could act as an excellent substrate for adsorption and polymerization of
aniline monomer. Because of the existence of GNO, the electrochemical activities of SPAN were enhanced obviously. Because of abundant
sulfonic acid groups, the resulting nanocomposite showed obvious self-redox signal even at physiological pH, which is beneficial for biosensing field.
DNA probes with
amine groups could be covalently attached to the modified
electrode surface through the acyl
chloride cross-linking reaction of sulfonic groups and
amines. When the flexible
probe DNA was successfully grafted, the
electrode was coated and electron transfer between
electrode and
buffer was restrained. Thus, the inner impedance value of SPAN (rather than using outer classic EIS probe, [Fe(CN)6](3-/4-)) increased significantly. After hybridization, the rigid helix opened the electron channel, which induced impedance value decreased dramatically. As an initial application of this system, the PML/RARA fusion gene sequence formed from promyelocytic
leukemia (PML) and
retinoic acid receptor alpha (RARA) was successfully detected.