Electrochemical oxidation of the antitumor antibiotic mitomycin C and in situ evaluation of its interaction with DNA using a DNA-electrochemical biosensor

The electrochemical behaviour of the antitumor drug mitomycin C (MMC) was investigated on carbon paste electrode over a wide pH range and using voltammetric techniques. The MMC undergoes diffusion-controlled irreversible oxidation in two different processes, one pH-independent for 2.2 ˂ pH ˂ 4.5 and one pH-dependent for 4.5 ˂ pH ˂ 12.0, and does not involve the formation of any electroactive oxidation product. Upon incubation in different pH electrolytes, chemical degradation of MMC was electrochemically detected by the appearance of a new oxidation peak at a lower potential. The chemically degraded MMC undergoes an irreversible, pH-dependent oxidation for 3.4 ˂ pH ˂ 5.4, and its redox products are reversibly oxidised. The spontaneous degradation of MMC in aqueous solution was confirmed by UV-Vis spectrophotometry. Moreover, a multilayer dsDNA-electrochemical biosensor was used to evaluate the interaction between MMC and DNA. The results have clearly proven that MMC interacts and binds to dsDNA strands immobilized onto a glassy carbon electrode surface and its metabolite(s) cause oxidative damage to DNA.