Electrochemical Detection of Biotin Using an Interaction between Avidin and Biotin Labeled with Ferrocene at a Perfluorosulfonated Ionomer Modified Electrode

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The electrochemical behavior of biotin labeled with ferrocene was investigated at a perfluorosulfonated ionomer (Nafion^®) film-coated glassy carbon electrode (GCE). The electrode response of the labeled biotin (LB) was improved by about fifty-fold in sensitivity by using a Nafion^®-coated GCE, compared with a plain GCE. It was found by a solid-phase avidin-biotin binding assay that the labeling with ferrocene hardly affected the affinity of a biotin moiety in the labeled biotin to avidin. The avidin-biotin interaction was estimated from the change of the electrode response caused by the formation of a complex with avidin and the labeled biotin. Furthermore, the detection of biotin was performed by a competitive reaction between the labeled biotin and unlabeled biotin for the limited binding sites of avidin.