Low-Potential Osmium-Based PVI redox polymer mediators for Diffusion-Controlled electrochemical glucose...

Osmium-based redox polymer mediators are attractive candidates for low-potential electrochemical biosensing, but a systematic evaluation of polymer-ligand coordination effects under identical electrode configurations is limited. In this study, an osmium-based polymer redox mediator, PVI-Os(dma-bpy)₂Cl, was synthesized, and its quantitative electrochemical performance for glucose detection was evaluated on an identical electrode platform. The formation of the polymer-metal complex and its physicochemical properties were confirmed by UV-Vis spectrophotometer, Fourier transform infrared spectroscopy, ¹H-nuclear magnetic resonance spectroscopy, and zeta potential analyses, indicating strong positive surface charge and good aqueous dispersibility. Electrochemical characterization using cyclic voltammetry and scan rate analysis showed diffusion-controlled redox behavior on carbon screen-printed electrodes immobilized with FAD-dependent glucose dehydrogenase (FAD-GDH), indicating efficient charge transport within the polymer network. The measurement conditions were optimized with respect to pH and enzyme loading, and the highest sensitivity and signal stability were obtained in phosphate-buffered saline (PBS, pH 7.4) with an enzyme concentration of 40 mg mL^-1. Under multi-potential step (MPS) conditions, the PVI-Os(dma-bpy)₂Cl-modified electrode exhibited stable and stepwise current responses to increasing glucose concentrations. Quantitative analysis revealed a wide linear range from 1 to 20 mM glucose with a sensitivity of 7.4190 µA cm^-2 mM^-1 at a low operating potential of 0.3 V and excellent linearity (R² = 0.99643). Negligible current responses were observed in the presence of common electroactive interferents, including ascorbic acid, dopamine, and uric acid, confirming the high selectivity under the applied conditions. Overall, this study presents a systematic evaluation of osmium-based polymer redox mediators and shows that ligand-tuned PVI-Os systems allow stable, low-potential, and interference-resistant electrochemical glucose detection. The proposed mediator platform is suitable for integration into electrochemical glucose sensors and enzymatic biofuel cell systems.