Electrochemical evaluation of the interaction between avidin and biotin at biotinylated polypyrrole electrode using a redox marker

The interaction between avidin and biotin was evaluated electrochemically by monitoring the change in the electrode response of redox markers. Biotin was immobilized on the electrode surface by means of the electrochemical polymerization of biotinylated pyrrole and pyrrole. When avidin was introduced onto the biotinylated polypyrrole electrode surface, the large change in the electrode response of the redox marker was detected. The fact that the change in the electrode response of a marker ion could be attributed to the electrostatic interaction between avidin on the electrode surface and the redox marker ion present in a solution was verified by replacing avidin with NutrAvidin. At a pH lower than the isoelectric point of avidin, the electrode response of ferrocyanide as an anionic marker ion increased linearly within the range of 5.0 × 10^-9 -3.0 × 10^-8 M avidin. The relative standard deviation at 1.5 × 10^-8 M avidin was about 5.4% (n = 5). The detection of biotin was also performed using a competitive reaction between biotin in solution and biotin that had been immobilized on the electrode surface in the form of the biotinylated polypyrrole.