Influence of several factors on potential-modulated DNA cleavage by the Cu(en)22+ and Cu(EDTA)2− complexes

Potential-modulated DNA cleavage in the presence of copper–ethylenediamine (en) and –ethylenediamine tetraacetic acid (EDTA) complexes was investigated at a gold electrode in a thin layer cell. DNA can be efficiently cleaved through production of active oxygen species at −0.50 V (vs. Ag/AgCl/KCl(sat)) by reducing Cu(en)22+ to Cu(en)2+ or Cu(EDTA)2− to Cu(EDTA)3−. The extent of DNA cleavage increased as the working potential was shifted more negative and the electrolysis time was increased in air-saturated solution. When a small flow of O2 was passed through the solution during electrolysis, the extent of DNA cleavage was dramatically enhanced. In the absence of Cu(en)22+ or Cu(EDTA)2− complex, slight DNA cleavage was observed at a more negative working potential due to the reduction of oxygen at the electrode. This observation suggests that potential-modulated DNA cleavage was caused mainly by electrochemical reduction of the Cu(en)22+ or Cu(EDTA)2− complex in the presence of oxygen. The cleaved DNA fragments were separated by high performance liquid chromatography (HPLC). The experimental results proved that this method of potential-modulated DNA cleavage by Cu(en)22+ and Cu(EDTA)2− complexes is simple, mild and highly efficient.