Anomalous Charge Transfer Enhancement by Ru Complex Ions and Its Application

[Ru(bpy)
2
DPPZl
²⁺
(bpy: 2,2’-bipyridine, DPPZ: dipyrido[3,2-a:2’,3’-c]phenazine), a DNA intercalator, was found to abnormally enhance charge transfer between a carbonaceous electrode and redox mediators, hexacyanoferrates, in electrochemical impedance spectroscopy (EIS). The effect appeared with a very small amount and was independent of other electrolyte and buffer components. Since [Ru(bpy)
2
DPPZ]
²⁺
can intercalate with dsDNA, the effect applies to detecting dsDNA in the solution. Real-time monitoring of PCR using this effect was successfully demonstrated by the change in Rct. Further development of this method is expected to enable EIS sensors that do not require electrode modification.