Binding reactions of copper(II) complexes of 1,10-phenanthroline (phen) and tetraaza macrocyclic ligand TAAB with calf thymus DNA have been investigated voltammetrically at bare and DNA modified glassy carbon electrodes. The values of binding constant, binding site size, ratio of binding constants for the reduced and oxidized copper complex forms as well as information on the electrostatic and intercalative binding modes were obtained by solution and surface-based methods. The Cu(phen)²₂+complex mediates the dsDNA cleavage to a higher degree than Cu(TAAB)²+as indicated by the redox marker Co(phen)³₃+and the anodic signal of the DNA base. A procedure for the damage to DNA detection using dsDNA/GCE biosensor is proposed.