Electrochemical Response of Glucose Oxidase Adsorbed on Laser-Induced Graphene

Carbon-based electrodes have demonstrated great promise as electrochemical transducers in the development of biosensors. More recently, laser-induced graphene (LIG), a graphene derivative, appears as a great candidate due to its superior electron transfer characteristics, high surface area and simplicity in its synthesis. The continuous interest in the development of cost-effective, more stable and reliable biosensors for glucose detection make them the most studied and explored within the academic and industry community. In this work, the electrochemistry of glucose oxidase (GOx) adsorbed on LIG electrodes is studied in detail. In addition to the well-known electroactivity of free flavin adenine dinucleotide (FAD), the cofactor of GOx, at the expected half-wave potential of -0.490 V vs. Ag/AgCl (1 M KCl), a new well-defined redox pair at 0.155 V is observed and shown to be related to LIG/GOx interaction. A systematic study was undertaken in order to understand the origin of this activity, including scan rate and pH dependence, along with glucose detection tests. Two protons and two electrons are involved in this reaction, which is shown to be sensitive to the concentration of glucose, restraining its origin to the electron transfer from FAD in the active site of GOx to the electrode via direct or mediated by quinone derivatives acting as mediators.