Most of the electrochemical techniques mentioned so far demand an electro-active compound in order to be oxidized or reduced and the current or voltage is recorded. Labelling DNA with a reversible redox-system complicated the situation. In addition the background of the sample should not interfere in this electrochemical process. This favors EIS. However the double layer capacitance is also influenced by other parameters (e.g., ionic strength, unspecific adsorption, etc.) which renders this technique into a method with interferences as long as those are not very well controlled before the analytical measurement. I would suggest a more reliable method working like a molecular switch: allowing the electrochemical reaction of an added redox-couple at a micro-electrode if no hybridization is occurring and stopping this reaction (current decrease) when the latter occurs. The electrochemical switch is based on available nano-magnetical beads. See last chapters of the publication below.