An ionic liquid supported CeO2 nanoshuttles-carbon nanotubes composite as a platform for impedance DNA hybridization sensing

A novel nanocomposite membrane, comprising of nanosized shuttle-shaped cerium oxide (CeO2), single-walled carbon nanotubes (SWNTs) and hydrophobic room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), was developed on the glassy carbon electrode (GCE) for electrochemical sensing of the immobilization and hybridization of DNA. The properties of the CeO2-SWNTs-BMIMPF6/GCE, the characteristics of the immobilization and hybridization of DNA were studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) using [Fe(CN)(6)](3-/4-) as the redox indicator. The synergistic effect of nano-CeO2, SWNTs and RTIL could dramatically enhance the sensitivity of DNA hybridization recognition. The electron transfer resistance (R-et) of the electrode surface increased after the immobilization of probe ssDNA on the CeO2-SWNTs-BMIMPF6 membrane and rose further after the hybridization of the probe ssDNA with its complementary sequence. The remarkable difference between the R-et value at the probe DNA-immobilized electrode and that at the hybridized electrode could be used for label-free EIS detection of the target DNA. The sequence-specific DNA of phosphoenolpyruvate carboxylase (PEPCase) gene from transgenically modified rape was detected by this DNA electrochemical biosensor. Under optimal conditions, the dynamic range for detecting the sequence-specific DNA of the PEPCase gene was from 1.0 x 10(-12) mol/L to 1.0 x 10(-7) mol/L, and the detection limit was 2.3 x 10(-13) mol/L, suggesting that the CeO2-SWNTs-BMIMPF6 nanocomposite hold great promises for the applications in sensitive electrochemical biosensor. (C) 2008 Elsevier B.V. All rights reserved.