Comparison of impedimetric detection of DNA hybridization on chemically and electrochemically functionalized multi-wall carbon nanotubes modified electrode

A label-free DNA biosensor was constructed on the base of multi-walled carbon nanotube (MWCNTs) modified electrode. This paper compares the detection of Amylogenin DNA using a glassy carbon electrode (GCE) modified with chemically and electrochemically functionalized MWCNTs. Functionalized MWCNTs were used to improve the sensitivity of the detection. The structure of functionalized MWCNTs was characterized by UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The optimum conditions were found for the immobilization of probe onto surface electrode and its hybridization with the target DNA in both methods. The surface of the modified electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Hybridization with the corresponding complementary ssDNA is monitored by changes in the charge transfer resistance (R-ct). This DNA biosensor also shows a good linear relationship between R-ct and the logarithm of the complementary target DNA concentration ranging from 1.0 x 10(-17) M to 1.0 x 10(-12) M with a correlation coefficient of 0.9961 for chemically functionalized MWCNTs and from 1.0 x 10(-18) M to 1.0 x 10(-13) M with a correlation coefficient of 0.9994 for electrochemically functionalized MWCNTs. The results show that the electrochemical method is better for MWCNTs functionalization than the chemical method. In addition two methods were satisfactorily applied for detection of the target sequence in real sample of Amylogenin DNA. (C) 2014 Elsevier B.V. All rights reserved.