Electrochemical detection of the interaction between avidin and biotin based on the change of electrode response of copper enhanced by biotin labeledwith thiourea

A new avidin-biotin assay based on monitoring the change in the electrode r esponse of the copper enhanced by the labeled biotin was investigated. The biotin labeled with thiourea was prepared as a bifunctional compound. The l abeled biotin exhibited a high enhancement effect toward the anodic strippi ng wave of copper as well as a specifical binding with avidin. The anodic s tripping wave of copper decreased when the labeled biotin bound with avidin . The calibration plot for avidin was linear between 1.0 x 10(-8) mol/L and 1.0 x 10(-7) mol/L. The relative standard deviation at 4.0 x 10(-8) mol/L avidin was 7.7 % (n = 5). The detection of biotin was performed by the comp etitive reaction between the labeled biotin and unlabeled biotin for the li mited binding sites of avidin. The relative standard deviation at 1.0 x 10( -7) mol/L biotin was 9.6 % (n = 5) with a detection limit of 2.9 x 10(-8) m ol/L. The presence of ascorbic acid more than 2000 times toward the concent ration of biotin did not interfere with the detection of 1.0 x 10(-7) mol/L biotin.