Electrochemical sensing of avidin-biotin interaction using redox markers

The interaction between avidin and biotin immobilized in self-assembled monolayer (SAM) on a gold electrode surface was electrochemically evaluated by monitoring the changes in the electrode response of three hydrophilic redox markers. The introduction of avidin membrane onto the biotin-SAM electrode surface caused the large changes in the electrode response of the redox marker. By using NutrAvidin instead of avidin, it was clarified that the changes of the electrode response were ascribed to the permeability of the marker through the avidin membrane on the electrode surface. At a lower pH than the isoelectric point of avidin, the electrode response of ferrocyanide ions as an anionic redox marker ions increased linearly over the range of 1.25 x 10^-9-1.25 x 10^-8 M avidin. The relative standard deviation at 2.25 x 10^-9 M avidin was about 3.9% (n = 5). On the other hand, the defection of biotin was performed using a competitive reaction between biotin in the solution and biotin in SAM on the electrode surface for avidin.