Redox-Active Polyindole-Modified Electrode for Electrochemical Uric Acid Determination

Uric acid (UA) is an important clinical biomarker whose reliable determination in complex biological media is often hampered by coexisting electroactive interferents. Intrinsically conducting polymers are versatile materials for electrochemical sensing, yet polyindole (PIn) has remained largely unexplored for this purpose. Here, we report a PIn-modified glassy carbon electrode for the nonenzymatic determination of UA in neutral phosphate buffer. PIn was synthesized by chemical oxidative polymerization in the presence of sulfonate dopants and deposited as a thin film on glassy carbon; physicochemical characterization confirmed a doped, conjugated, and nanostructured coating with a high effective surface area. The electrode showed a well-defined UA oxidation signal and, by chronoamperometry, a linear response over 0.01-0.10 mM with a sensitivity of 4.53 μA cm^-2 mM^-1 and a limit of detection of 4.0 μM. Under the applied conditions, ascorbic acid, dopamine, glucose, and sodium chloride contributed only marginally to the response, and the sensor performed reliably in diluted human serum, with recoveries of 99.7-99.9% and relative standard deviations below 5%. These findings identify polyindole as a promising, still underexplored intrinsically conducting polymer for electrochemical biosensing.