Electrochemical Detection of the Interaction Between Avidin and Biotin Based on the Change of Electrode Response of Copper Enhanced by Biotin Labeled with Thiourea

A new avidin-biotin assay based on monitoring the change in the electrode response of the copper enhanced by the labeled biotin was investigated. The biotin labeled with thiourea was prepared as a bifunctional compound. The labeled biotin exhibited a high enhancement effect toward the anodic stripping wave of copper as well as a specifical binding with avidin. The anodic stripping wave of copper decreased when the labeled biotin bound with avidin. The calibration plot for avidin was linear between 1.0×10–8 mol/L and 1.0×10–7 mol/L. The relative standard deviation at 4.0×10–8 mol/L avidin was 7.7 % (n=5). The detection of biotin was performed by the competitive reaction between the labeled biotin and unlabeled biotin for the limited binding sites of avidin. The relative standard deviation at 1.0×10–7 mol/L biotin was 9.6 % (n=5) with a detection limit of 2.9×10–8 mol/L. The presence of ascorbic acid more than 2000 times toward the concentration of biotin did not interfere with the detection of 1.0×10–7 mol/L biotin.