Detection of DNA damage is significant to evaluate genotoxicity of new chemicals in the early stages of its development. In this work, we described an electrochemical biosensor for simple, rapid and sensitive detection of specific sequences of DNA. Ferrocene (Fc)-labeled probe DNA first hybridized with capture DNA 1 to form double strands in the hybridization solution. In the presence of target DNA, the Fc-labeled probe DNA will be released by the digestions of exonuclease III and further hybridize with the capture DNA 2 immobilized on a gold electrode, producing strong electrochemical signals. On the other hand, Exonuclease Ill (Exo III) leaded to recycling and reuse of the target DNA, which also resulted in signal amplification. The present method can discriminate single base mismatched DNA from complementary DNA and has been successfully applied to detect DNA damage induced by chemical reagents and UV radiation. (C) 2013 Elsevier B.V. All rights reserved.