A biosensor monitoring DNA hybridization based on polyaniline intercalated graphite oxide nanocomposite

Polyaniline intercalated graphite oxide nanocomposite (PAI/GO) was synthesized. The microstructure of PAI/GO were investigated using Fourier transform infrared spectrometer (FT-IR), X-ray diffractometer (XRD), transmission electron microscope (TEM) and atomic force microscope (AFM). The results show that polyaniline intercalated between interlayers of GO, changes the structure of GO greatly forming nanograins in the chain and helix-like form. The resulting nanocomposite enveloped in carbon paste electrode displays electrochemical activity and two sharp peak potentials of square wave voltammometry (SWV) are at 668 and 207 mV. Such characteristics of PAI/GO have been employed to investigate the interaction between DNA and PAI/GO. The results indicate that single-strand DNA (ssDNA) and double-strand DNA (dsDNA) can change redox characteristics of PAI/GO on the PAI/GO modified carbon paste electrode (CPE) and the modified electrode has strong electrochemical effect on the redox of ssDNA and dsDNA. The SWV redox potentials in ssDNA and dsDNA solution are 90.99 and 18 mV, respectively. The PAI/GO-modified electrode immobilized with ssDNA can be utilized to monitor hybridization of complementary ssDNA with hybridization peak at -270 mV. The influence of various experimental parameters on PAI/GO-modified CPE in ssDNA solution (i.e. frequency and amplitude of SWV, pH and incubation time) was investigated. Under optimization of experimental variables, a linear relationship between the peak current (E-p is around 90.99 mV) recorded with the electrode not immobilized by ssDNA and the ssDNA concentration in solution was obtained covering range from 34 to 241 mug/mL. And the modified electrode immobilized by ssDNA can be utilized to monitor the hybridization and detect complementary ssDNA, covering linear range from 275 to 551 mug/mL. The PAI/GO-modified CPE exhibited a good stability and reproducibility for detecting ssDNA. (C) 2004 Elsevier B.V. All rights reserved.