The detection of biological analytes or of biochemical processes by electrochemical methods requires in many cases the presence of a redox-active probe as part of the detection system. The focus of this presentation is on the use of electrochemical methods to probe nucleic acids without the need to label DNA targets.

My research group has developed an impedance-based assay that allows the detection of single nucleotide mismatches. This assay does not require any labeling of the target strand and relies on monitoring changes in charge transfer resistance of an external anionic redox probe as a function of basepair mismatch. The effect is caused by differences in the ability of the redox probe to diffuse into a DNA film.

Furthermore, the use of scanning electrochemical microscopy (SECM) for the study of nucleobase mismatches will be discussed. SECM is ideal to study these effects since the currents are limited by the re-generation of the redox mediator at the modified electrode surface. Here we report that we can unequivocally identify the presence and position of single nucleotide basepair mismatches using ferricyanide as a solution-based redox mediator. Our results show that the presence of metal ions enhances the detection by SECM significantly.