Screen-Printed Electrode Modified with Silver Nanoparticles (AgNP)─Polydopamine (PDA)─Reduced Graphene Oxide (RGO) Nanocomposite as a Sensor for Uric Acid

A uric acid (UA) sensor was developed through the modification of carbon screen-printed electrodes (SPE) with a nanocomposite of silver nanoparticles (AgNP), polydopamine (PDA), and reduced graphene oxide (RGO). The AgNP-PDA-RGO nanocomposite was characterized by ATR-FTIR, UV-vis, Raman, and SEM-EDX to confirm the synthesis of the nanocomposite. Electrocatalytic activity was investigated by measuring specific capacitance and peak current using cyclic voltammetry using a Fe-(CN)₆ ^-3/-4 probe. Analytical performance of the AgNP-PDA-RGO modified SPE for UA was investigated by using differential pulse voltammetry in acetate buffer (pH 4.5). Two linear ranges from 20-100 μM and 200-1000 μM were established with a limit of detection of 1.23 μM. The UA signal was repeatable (relative standard deviation (RSD) = 5.00%, <i>n</i> = 10) on a single modified electrode and reproducible across multiple electrodes (RSD = 0.95%, <i>n</i> = 3), and the signal was stable after 28 days (only 0.41% change from initial signal, <i>n</i> = 3). The AgNP-PDA-RGO sensor was also used for the measurement of UA in lab-prepared urine samples and tested in the presence of organic interferents such as ascorbic acid, dopamine, and glucose.