The interaction of an anticancer drug, TPT and dsDNA was investigate at the surface of pretreated PGEs, unmodified PGEs and SWCNT modified PGEs by using electrochemical techniques for the first time in the literature. The oxidation signals of TPT and guanine were measured before/after each modification/interaction step and the changes at the signals of TPT and guanine were evaluated by means of interaction process. Since SWCNTs provided a large surface area for immobilization of DNA and drug molecules, an enhanced sensor respone was obtained after SWCNT modification onto the surface of disposable PGEs comparison to unmodified ones.