After the modification of CP,the peak current decreased (curve b) which was attributed to the electrostatic repulsion between the DNA phosphoric acid skele-ton structure and negative charged electroactive probes. When thegold electrode was treated with MCH, the peak current was fur-ther decreased (curve c) which is ascribed to the electron inertfeature of MCH which partially blocks the electron transfer andmass transfer of Fe(CN)63−/4−ions on the surface of gold electrode.