Paddy Stem–Derived Activated Carbon-Based Uricase Biosensor for Highly Sensitive Electrochemical Detection of Uric Acid

For the diagnosis and management of metabolic diseases, such as gout, hyperuricemia, hypertension, and diabetes, accurate and timely measurement of uric acid (UA) is essential. This article presents the design of low-cost and eco-friendly enzymatic electrochemical biosensors to detect UA through the use of porous activated carbon nanomaterial (PSAC) obtained from paddy stem as the electrode modifier. Acid treatment, carbonization, and KOH activation were used to create PSAC, a high-surface-area, porous, and electrically conductive carbon nanomaterial that can be used to immobilize enzymes. XRD, FE-SEM, HR-TEM, and XPS analytical techniques were used for structural and morphological characterizations. These techniques further validated the amorphous turbostratic carbon framework with a large number of functional groups and porosity. To improve enzyme stability and reduce interference, uricase (UOx) was mounted onto the PSAC-modified glassy carbon electrode (GCE) and then coated with Nafion. When compared to unmodified electrodes, electrochemical experiments showed that the UOx/PSAC@GCE electrode demonstrated higher catalytic activity toward UA oxidation, with a notable increase in peak current and a lower oxidation potential. With a low limit of detection (LOD = 0.0715 nM) and limit of quantification (LOQ ≈ 0.215 nM), differential pulse voltammetry (DPV) displayed a linear response over the concentration range of 10–1000 nM and achieved great sensitivity (2.2588 μA/nM). The biosensor was successfully used to detect UA in actual urine samples and has given outstanding selectivity, repeatability, and stability. This study signifies the potential of carbon nanomaterials produced from agricultural waste for high-performance, sustainable biosensing platforms in clinical diagnostics.