The Impact of the Position of the Redox Label on Charge Transfer and Hybridization Efficiency at DNA Interfaces

Abstract A common electrode construct for electrochemical DNA biosensors consists of tethering a redox‐label‐modified single stranded DNA to the electrode and comparing the electrochemical response of a redox probe before and after hybridization. Despite the analytical advantages of this construct, contradictory results are found in the literature regarding to the effect of redox‐labeling position on the charge transfer process happening at a DNA interface. Herein a contribution to this discussion is made by investigating how a methylene blue redox label placed at different positions along a probe strand of DNA affects the DNA hybridization efficiency. For that, a second redox label, a ferrocene molecule, was attached to the target DNA at a fixed position such that upon hybridization it is positioned at the distal end of the DNA monolayer. The dual label strategy allowed us to explore, for each methylene blue labeling position, how the binding‐induced diminution in the methylene blue signaling is associated with the appearance of the ferrocene signaling after hybridization. It was found that the location of the methylene blue redox label in the DNA interface can affect the hybridization efficiency.