Since its discovery in 1928, glucose oxidase (GOx) is still one of the most studied enzymes worldwide because of its various industrial applications: textile bleaching, food and baking industry or for the production of gluconic acid, but the most well-known application of glucose oxidase is its use in daily and continuous glucose sensors for diabetes management [1]. GOx may also find applications in glucose/O2 biofuel cell or self-power sensors [2]. The greatest benefits of glucose oxidase over other sugars enzymes for bioelectrochemical applications are its high specificity for glucose, low redox potential ($\sim$ -0.42V vs. Ag/AgCl at pH 7.4) and good thermostability [3]. These properties allow scanning electrochemical microscopy (SECM) to efficiently exploit the unique properties of such enzymes using probes. SECM employs ultramicroelectrodes (UMEs) that can be moved in the proximity of a surface while recording a faradaic current, which depends on both the topography and the electrochemical activity of the surface itself [4].
The aim of this study was to determine GOx activity with different K3[Fe(CN)6] concentrations (0.5, 0.75, 1.0, 1.5, 2.0 mM) using tip generation – substrate collection mode scanning electrochemical microscopy of oxygen reduction electrocatalysts. Glucose concentration was 10 mM and Au UME (5 μM) was used as a probe for SECM measurements.