Electrochemical biosensors based on DNA strand exchange

Electrochemical biosensors for the detection of specific DNA sequences have been described. The redox-modified DNA sequences were hybridized with the 3′-thiol-modified DNA sequences as capture DNA strand. The resulting duplexes were assembled on a gold electrode surface to make DNA chip. Upon addition of fully complementary DNA or mismatchcontaining DNA, the time-dependent changes in redox signal were monitored. Mismatched DNA gave less than 20% change when compared with fully matched DNA under the same conditions. The present assay format is thus applicable in discrimination of mutated DNA from fully matched DNA.