Electrochemical Characterization of Glucose Oxidase Immobilized in Intrinsically Conducting Polymers: Polyaniline vs. Self-Doped and Substituted Polyaniline

This study investigates the electrochemical behaviour of glucose oxidase (GOx) immobilized in: polyaniline (PANI), self-doped polyaniline (SD-PANI), and poly(o-toluidine) (POT), a substituted aniline derivative. All polymeric materials were synthesized electrochemically via galvanostatic polymerization on graphite electrodes. SD-PANI was obtained by copolymerizing aniline with metaaminobenzoic acid, introducing internal proton-donating groups to enhance conductivity and enzyme compatibility. The presence of –OH groups increases the hydrophilicity of the polymer, facilitating interactions with aqueous solutions and biological molecules such as enzymes, thereby improving immobilization efficiency. GOx was immobilized by cross-linking via glutaraldehyde. Amperometric measurements in the presence of glucose were used to evaluate the bioelectrocatalytic response. Michaelis-Menten kinetic parameters — the apparent Michaelis constant (Km) and maximum current response (Imax) — were extracted from steady-state current responses using the Lineweaver-Burk method. Although the most favorable kinetic parameters were obtained for PANI, followed by POT and SD-PANI, the highest storage stability of GOx was observed with SD-PANI due to its conductivity in neutral media. These findings highlight the influence of polymer structure and functionalization on enzymatic activity and biosensor efficiency.