Glucose Microsensor with Covalently Immobilized Glucose Oxidase for Probing Bacterial Glucose Uptake by Scanning Electrochemical Microscopy

We have developed a new dual tip glucose sensing scanning electrochemical microcopy (SECM) probe by covalently immobilizing the glucose oxidase (GOD) enzyme onto an ultra-micro electrode (UME), to measure the local glucose consumption of Streptococcus mutans (S. mutans) biofilms. GOD enzyme was immobilized on a novel enzyme immobilization matrix of functionalized multiwalled carbon nano tubes (f-MWCNT) and 1-butyl-4-methylpyridinium hexafluorophosphate (ionic liquid/IL) packed into the etched Pt UME. The highly selective GOD enzyme based SECM tip showed a high current density of 94.44 (±18.55) µA. mM-1.cm-2 from 0.1 mM to 1.0 mM at 37○C due to synergetic effects of f-MWCNT and ionic liquid. The detection limit of new 25 µm diameter glucose sensor is 10.0 µM and has a linear range up to 4.0 mM. New glucose sensor was used successfully to quantify the rate of glucose consumption of S. mutans biofilms in the presence of sucrose. S mutans catabolizes both glucose and sucrose producing lactic acid dropping the...