Electrochemical sensing of the interaction of the anti-infective agent pentamidine with DNA

The electrochemical oxidation of pentamidine drug was first investigated in aqueous buffered solutions by cyclic voltammetry using a glassy carbon electrode. Pentamidine exhibited pH dependent irreversible oxidation peaks at high anodic potentials through a diffusion-controlled process as the benzamidine moieties of pentamidine are oxidized to benzamidoxime. Thereafter, the pentamidine-dsDNA interaction was investigated in solution and at dsDNA-sensor surface. The change in the oxidation signals intensity of guanine and adenine before and after interaction with pentamidine was monitored by the differential pulse voltammetry. The decrease in the peak current of their signals was used as an indication for the interaction event. After that, the diazonium chemistry was applied for the immobilization of ds-DNA on glassy carbon electrode surface. The interaction between pentamidine and immobilized DNA were determined by the changes in the voltammetric peak of crystal violet redox probe. The peak currents of the crystal violet decreased after pentamidine interaction with immobilized DNA. Finally, the pentamidine-dsDNA interaction was further assessed by the Faradaic electrochemical impedance spectroscopy, following the changes in charge transfer resistance after immersion of the DNA biosensor in pentamidine solution.