This result may be due to the fact that the negatively charged phosphate backbone of double stranded DNA prevented redox couple, from reaching the electrode surface. The Rct value 0.34 times decreased after the interaction process. The intercalation of TPT into dsDNA resulted by the damage of double helix form of DNA, and consequently the decrease was recorded at Rct. According, these impedimetric results were consistant with voltammmetric results and paralled with the other studies performed by using CNT modified electrodes