Enhanced Glucose Sensing Via Metal-Phenolic Networks Modified Gold Leaf Electrode: A Novel Approach for Improved Hydrogen Peroxide Oxidation and Detection

In 2021, 38.4 million people in the U.S. alone had diabetes, a chronic disease caused by an inability in regulating blood glucose. Glucose monitoring is crucial for them to avoid complications and prevent disease progression. Though glucose monitoring is well-established, there is always the need for improved sensing. To that end, we have developed a gold leaf electrode that possesses increased glucose detection sensitivity through surface modification with metal-phenolic-networks (MPNs). MPNs are simple, inexpensive, and sustainably-made, and they have the ability to serve as electrocatalysts for hydrogen peroxide (H₂O₂) oxidation. The gold leaf glucose sensor involves a coupled reaction between glucose and H₂O₂ oxidation. Glucose is oxidized by a glucose oxidase coating on the electrode, generating H₂O₂, which is then oxidized through the functional electrode. The current produced by H₂O₂ oxidation is proportional to glucose levels, enabling quantification. After simple, manual electrode fabrication, the system sensitivity was evaluated through titration of H₂O₂ solutions onto the surface. However, the gold leaf electrode was insufficient for quantitative peroxide oxidation. We therefore incorporated an electropolymerized MPN layer on the electrode, yielded currents proportional to peroxide concentration, based on catalysis at the MPN metal centers. To stabilize the MPN and increase the difference in electrochemical current between each H₂O₂ concentration, chitosan was drop coated onto the working electrode. The gold leaf electrode, modified with MPNs and chitosan, showed significant improvement in the sensitivity of glucose sensing, and future tests with urine and serum will be conducted to validate its performance in more complex biological environments.