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 (Ret) 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 Ret 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 × 10−12 mol/L to 1.0 × 10−7 mol/L, and the detection limit was 2.3 × 10−13 mol/L, suggesting that the CeO2–SWNTs–BMIMPF6 nanocomposite hold great promises for the applications in sensitive electrochemical biosensor.