Electrochemical DNA biosensor based on IL-modified MWNTs electrode prepared by radiation-induced graft polymerization

Electrochemical DNA (E-DNA) biosensors were fabricated by the physical immobilization of probe DNA, 5'-GGA GCT GCT GGC ATT ATT GAA-3', on ionic-liquid-multiwalled carbon nanotubes (IL-MWNTs) modified with indium tin oxide (ITO) electrodes to detect Salmonella typhi (S. typhi). IL-MWNTs were prepared by the introduction of 1-butylimidazole bromide onto an epoxy group on poly(GMA)-grafted MWNTs, which were synthesized by radiation-induced graft polymerization of glycidyl methacrylate (GMA) onto MWNTs in aqueous solution. Subsequently, IL-MWNTs were coated onto the ITO electrode surface, and then the physical immobilization of the probe DNA performed in probe DNA solution at room temperature for 1 h. The IL-MWNTs were characterized by elemental analysis, XPS, and TGA. The electron transfer resistance (Ret) of the E-DNA biosensor was evaluated after hybridization of the probe DNA and target DNA using electrochemical impedance spectroscopy. The Ret increased after the hybridization of probe DNA and target DNA. The DNA used was complementary DNA: 5'-TTC AAT AAT GCC AGC AGC TCC-3', single-base mismatch DNA: 5'-TTC AAT AAT GGC AGC AGC TCC-3' and three-base mismatch DNA: 5'-TTC ATT AAT GGC AGC ACG TCC-3'. The dynamic detection range for the sequence-specific DNA of target DNA was from 1.0 x 10-13 to 1.0 x 10-10 mol L-1 with a regression equation Ret (O) = 18.6 C + 128 and regression coefficient (?) of 0.996. The detection limit was determined to be 3.1 x 10-14 mol L-1. The results demonstrated that the sensitivity of this impedance-based DNA sensor was sufficient for the target DNA sequence detection. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012