Direct electron transfer biosensor for hydrogen peroxide carrying nanocomplex composed of horseradish peroxidase and Au-nanoparticle – Characterization and application to bienzyme systems

•Formation of nanocomplex composed of Au-nanoparticle and horseradish peroxidase was studied.•The nanocomplex as the functional unit was immobilized on an ITO electrode giving a direct electron transfer biosensor without any soluble mediator.•The sensor exhibited high sensitivity to hydrogen peroxide at a very mild potential of +0.15 V vs. Ag/AgCl, indicating that the reaction scheme is similar to the native process of the enzyme.•The electrode was applied oxidase-based biosensors for glucose and uric acid.

A reagentless electrochemical biosensor for hydrogen peroxide was fabricated. The sensor carries a monolayer of nanocomplex composed of horseradish peroxidase and Au-nanoparticle, and responds to hydrogen peroxide through the highly efficient direct electron transfer at a mild electrode potential without any soluble mediator. Formation of the nanocomplex was studied with visible spectroscopy and size exclusion chromatography. The sensor performance was analyzed based on a hydrodynamic electrochemical technique and enzyme kinetics. The sensor was applied to fabrication of sensors for glucose and uric acid through further modification of the nanocomplex-carrying electrode with the corresponding hydrogen peroxide-generating oxidases, glucose oxidase and urate oxidase, respectively.

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