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Abstract
A novel nanocomposite membrane, comprising of nanosized shuttle-shaped cerium oxide
(CeO(2)), single-walled carbon nanotubes (SWNTs) and hydrophobic room temperature
ionic liquid (RTIL) 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF(6)), was
developed on the glassy carbon electrode (GCE) for electrochemical sensing of the
immobilization and hybridization of DNA. The properties of the CeO(2)-SWNTs-BMIMPF(6)/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-CeO(2), 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 CeO(2)-SWNTs-BMIMPF(6) 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 1.0x10(-12) mol/L to 1.0x10(-7) mol/L, and the detection limit was 2.3x10(-13)
mol/L, suggesting that the CeO(2)-SWNTs-BMIMPF(6) nanocomposite hold great promises
for the applications in sensitive electrochemical biosensor.