Amperometric biosensor for polyphenol based on horseradish peroxidase immobilized on gold electrodes

Horseradish peroxidase (HRP) is covalently immobilized on a self-assembled monolayer of mercaptopropionic acid on vapor-deposited gold electrode. The electrode allows the polyphenol detection down to 2 μM with a linear relationship up to 25 μM. The reduction current of oxidized polyphenols, formed during the enzymatic oxidation of polyphenolic compounds in the presence of H₂O₂, is proportional to their concentration. The sensitivity of the detection of various polyphenols by the present method depends on both the electron-donating properties of polyphenols and the electron-accepting properties of oxidized polyphenols. The total amounts of polyphenols in several wine and tea samples detected by the present method are well correlated with those determined by the Folin-Ciocalteu method. In addition, this method has several advantages over the Folin-Ciocalteu method: shorter detection time, smaller sample volume, and more torelant to interference substances.