The study of small drug molecules interacting with nucleic acids is an area of intense research that has particular relevance in our understanding of relative mechanism in chemotherapeutic applications and the association between genetics (including sequence variation) and drug response. In this contribution, we demonstrate how the sequence-specific binding of an anticancer drug Dacarbazine (DTIC) to single base (A-G) mismatch could be sensitively detected by combining electrochemical detection with biosensing surface based on gold nanoparticles.