Wiring Xanthine Oxidase Using an Osmium‐Complex‐Modified Polymer for Application in Biosensing.

Abstract

Dedicated to Prof. Dr. Wolfgang Schuhmann on the occasion his 65 th birthdayXanthine is a metabolite of interest as a medical and food freshness biomarker. We modified a screen-printed electrode to detect this analyte by co-entrapping xanthine oxidase (XOD) and an Os-complex redox polymer over carbon nanotubes. In nature, XOD transfers its electrons to oxygen in solution. We demonstrate that the introduction of the redox polymer allows routing the electrons efficiently to the electrode surface, even under air-saturated conditions, enabling superior catalytic current and sensing performance. The bioanode was optimized by adjusting the electrode materials and the ratio of enzyme to redox polymer. The impacts of pH and ionic strength of the electrolyte on the sensor performance were also studied. We found that these variables can affect the electrostatic interaction between the enzyme and the redox polymer, and therefore impact the catalytic current extracted from xanthine oxidation. The XOD-bioanode design was combined with a bienzymatic cathode operating on glucose to demonstrate a biofuel cell (BFC). The resulting device could generate a power output of 16.56 μW cm À 2 at 0.25 V and an open-circuit voltage (OCV) of 0.50 V using 500 μM xanthine as biofuel. The proposed xanthine/glucose BFC showed promising features for application as a self-powered xanthine biosensor.

In Vivo Electrochemical Measurement of Glucose Variation in the Brain of Early Diabetic Mice

“…Figure a displays the cyclic voltammograms (CVs) obtained in aCSF containing different concentrations of glucose. Typical redox current peaks associated with Os 2+ /Os 3+ transition are observed at +0.25 V . Glucose can react with the redox mediator Os 3+ under the catalysis of GOx (eqs –)­ …”

“…Figure a displays the cyclic voltammograms (CVs) obtained in aCSF containing different concentrations of glucose. Typical redox current peaks associated with Os 2+ /Os 3+ transition are observed at +0.25 V . Glucose can react with the redox mediator Os 3+ under the catalysis of GOx (eqs –) normalg normall normalu normalc normalo normals normale + normalG normalO normalx ( F A D ) → normalg normall normalu normalc normalo normaln normalo normall normala normalc normalt normalo normaln normale + normalG normalO normalx ( F A D H 2 ) G O x ( F A D H 2 ) + 2 O s 3 + → normalG normalO normalx ( F A D ) + 2 normalO normals 2 + normalO normals 2 + → normalO normals 3 + + e − …”

Electrodeposition of Cobalt Oxides on Carbon Nanotubes for Sensitive Bromhexine Sensing

“…These methods require sophisticated and expensive instruments, which are often not available in low-resource areas. The electrochemical analysis of BHC seems like a promising alternative, as it could enable portable instruments with reasonable sensitivity [9]. The electrochemical oxidation mechanism of BHC has been elucidated [10], and it seems suitable for the development of an electrochemical sensor.…”