Voltammetric detection of the DNA interaction with toluidine blue

Binding reactions of toluidine blue (TB) with herring fish DNA in pH 6.0 Britton-Robinson (B-R) buffer solution have been investigated by cyclic voltarnmetry and linear-sweep voltammetry at a glassy carbon electrode. TB has a couple of well-defined redox peaks. The addition of DNA into the TB solution resulted in the decrease of the redox-peak currents and the shift negatively of the anodic peak potential. The values of the electrochemical parameters such as the electron number of the electrochemical reaction, the electron transfer coefficient and the electrochemical reaction standard rate constant in the absence and presence of DNA, as well as the values of binding constant and binding ratio of DNA with TB were obtained. Almost unchanged values of the electrochemical parameters in the absence and presence of DNA show that nonelectroactive complexes were formed when TB interacted with DNA. DNA concentration can be determined by the decrease of the peak current of TB. The binding mode of TB with DNA was discussed.