Recognition and detection of dsDNA at a thionalid self-assembled monolayer modified gold electrode

A novel method for the recognition and detection of dsDNA has been developed at a thionalid self-assembled monolayer modified gold electrode (TNL/Au SAMs). This method is based on thionalid at a gold electrode intercalating dsDNA. Attenuated total reflection-Fourier transform infrared (ATR-FTIR), cyclic voltammetry (CV) and ac impedance method are used to characterize the thionalid self-assembled monolayer modified gold electrode. Electrochemical method is adopted to investigate the interaction of thionalid and dsDNA, and fluorimetry proves further the interaction. Only dsDNA can interact with thionalid, we deduce that plane thionalid molecule insert base pairs of dsDNA forming a channel of electron transfer (ET), which is benefit to the ET of redox of gold. There are definite relations between the reductive peak value of Au and the concentration of dsDNA. A linear dependence of the reductive peak currents on the concentration of dsDNA is observed in the range 2.5×10−5 to 2.0×10−4 g L−1, with a detection upper limit of 2×10−4 g L−1. Another linear dependence of the peak currents on the logarithm value of the concentration is in the range 1.0×10−8 to 1.0×10−5 g L−1, with a detection limit of 1.0×10−9 g L−1. Their correlation coefficients are 0.9990 and 0.9962, respectively. For this reason, this modified electrode can be applied to quantitative analysis of dsDNA, recognize dsDNA, label degree of dsDNA hybridization and instruct design of new anticancer drug molecules.