Strategy for low background-current levels in the electrochemical biosensors using horse-radish peroxidase labels

This article describes an electrochemical strategy to achieve low background-current levels in horse-radish peroxidase (HRP)-based electrochemical immunosensors. The strategy consists of (i) the use of an HRP substrate/product redox couple whose formal potential is high and (ii) the use of an electrode that shows moderate electrocatalytic activity for the redox couple. The strategy is proved by a model biosensor using a catechol/o-benzoquinone redox couple and an indium tin oxide (ITO) electrode. The combined effect of high formal potential and moderate electrocatalytic activity allows o-benzoquinone electroreduction with minimal catechol electrooxidation and H₂O₂ electroreduction. The detection limit for mouse-IgG is 100 pg/mL.