Imaging Glucose Oxidase by Scanning Electrochemical Microscopy

Abstract

Scanning Electrochemical Microscopy is a tool for imaging and investigate surfaces by meaning of chemical reactivity, electric conductivity, and enzymatic activity. This technique is typical electrochemical cell plus three axis positioner. Positioner allows to measure typical electrochemical measurements, like Cyclic Voltammetry, Chronoamperometry, Impedance Spectroscopy, etc. in the vicinity of substrate and in the chosen position of working electrode. Moreover, this technique can be used as biosensor, e.g. measuring glucose concentration or other parameters, such as lactate and oxygen detection in living and unhealthy cells. In this paper, we present imaging of glucose oxidase by Scanning Electrochemical Microscopy in feedback mode. For experiments, glucose oxidase on the plastic surface was used as well-known enzyme. Imaging of glucose oxidase was performed in buffer with different glucose concentrations and with different redox mediator concentrations. Measurements showed that for higher image resolution glucose concentration has to be about 15-20 mmol•L-1 and redox mediator concentration needs to be lower than 0.2 mmol•L-1. For image processing, Matlab programme was used. Another part of measurements was approaching the ultramicroelectrode to the surface and the current dependence on distance is shown in different concentrations of redox mediator and glucose.