Conductive architecture of Fe2O3 microspheres/self-doped polyaniline nanofibers on carbon ionic liquid electrode for impedance sensing of DNA hybridization

A novel architecture was designed by combining the strong adsorption ability of Fe2O3 microspheres to the DNA probes and excellent conductivity of self-doped polyaniline (SPAN) nanofibers; (copolymer of aniline and m-aminobenzenesulfonic acid) on carbon ionic liquid electrode (CILE) for electrochemical impedance sensing of the immobilization and hybridization of DNA. The formed conductive Fe2O3/SPAN membrane on the CILE was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using [Fe(CN)(6)](3-/4-) as the indicator. The immobilization of the probe DNA on the surface of electrode and the sensitivity of DNA hybridization recognition were dramatically enhanced due to the unique synergistic effect of Fe2O3 microspheres, SPAN nanofibers and ionic liquid. The DNA hybridization events were monitored with a label-free EIS strategy. Under optimal conditions, the dynamic range of this DNA biosensor for detecting the sequence-specific DNA of phosphoenolpyruvate carboxylase (PEP-Case) gene from transgenically modified rape was from 1.0 x 10(-13) to 1.0 x 10(-7) mol/L, and the detection limit was 2.1 x 10(-14) mol/L. This work suggested a simple strategy to prepare a conductive interface for electrochemical detection of DNA hybridization and opened a way for the application of Fe2O3 in DNA electrochemical biosensing. (C) 2009 Elsevier B.V. All rights reserved.