Electrocatalytic Oxidation of Nucleic Acids at Electrodes Modified with Nylon and Nitrocellulose Membranes

Abstract

Electrocatalytic oxidation of guanine in DNA was detected at tin-doped indium oxide electrodes modified with nylon and nitrocellulose polymers. The catalytic oxidation occurs via oxidation at the electrode of the complex Ru(bpy) ²⁺₃ to the 3+ state, which is then reduced back to the 2+ state by guanine in DNA (bpy = 2,2′-bipyridine). Catalysis is observed as a current enhancement in the cyclic voltammogram of Ru(bpy) ²⁺₃ when DNA is immobilized in the film. As seen in solution, the catalytic enhancement in the nitrocellulose film is lower at 800 mM NaCl than without added salt because electrostatic binding of the Ru(bpy) ²⁺₃ to the DNA at low salt increases the catalytic rate constant. The cyclic voltammogram of Os(bpy) ²⁺₃ , which does not oxidize guanine, exhibits less current in the presence of DNA because binding to the immobilized DNA precludes communication of the metal complex with the electrode. Electrodes modified with poly[C] gave no enhancement; however, catalytic current was observed upon hybridization to poly[G]. Exposure of the poly[C] electrode to random single-stranded DNA gave no catalytic current. Glassy carbon electrodes modified with the membranes behaved in a manner similar to that of the metal oxide electrodes.