In this study, we prepared a DNA-based biosensor for the determination of chrysoidine and investigation of anti-cancerous features of vitamin K3 in the presence of various reducing agents. A pre-treated pencil graphite electrode (PGE) was modified using multi wall carbon nanotubes (MWCNTs), poly(diallydimethylammonium chloride), PDDA, and then decoration with a DNA. Multi wall carbon nanotubes were used in the fabrication of biosensors because of their high electrical conductivities, high chemical stabilities, and extremely high mechanical strengths. Moreover, MWCNTs modified the surface of PGE for stabilizing of a thin layer of DNA on the substrate. This simple and inexpensive biosensor operated through interaction of chrysoidine and free radicals with DNA.

The first part explains the use of DNA-based biosensor for the determination of trace amount of chrysoidine, known as a cancerous azo dye. First, the interaction of the DNA with chrysoidine was studied at pH 7.0. Differential pulse voltammetry (DPV) method was then applied at pH 4.8 (acetate buffer) to measure the adenine, guanine, and chrysoidine signals. The outputs signals indicated that the signals of adenine and guanine after interaction of the biosensor with chrysoidine were decreased. Under the optimum conditions, a linear dependence of the guanine and adenine oxidation signals was observed for the chrysoidine concentration in the range of 0.05­- 0.80 and 1.50­-­20.00 µg mL^-1 with a detection limit of 0.037 µg mL⁻¹. This sensor was successfully used to measure the pigment in things such as tomato powder, fish, tomato sauce and industrial water.

The second part of this study have been investigation of toxicity, behavior mechanism of vitamin K3 (menadione) as anti-cancer material by Differential pulse voltammetry and electrochemical impedance spectroscopy method in the presence of NADH and vitamin C in various conditions. The decomposition of DNA mechanism of menadione as a generating free radicals and anti-cancer material was investigated and successfully proved. It is concluded that DPV and Impedance Spectra can be used as appropriate techniques for quantitative and qualitative comparison of different reagent for DNA damage mechanism investigations.

Keywords: DNA-based biosensor, Multiwall carbon nanotubes, Chrysoidine, Menadione, Differential pulse voltammetry.