A Cost-Effective Hydrogel-Based Electrochemical Platform for Uric Acid Detection in Synthetic Urine

This study introduces, for the first time, a novel voltammetric strategy based on integrating a stencil-printed electrode (StPE) with a hydrogel (HG) serving as the electrolytic medium. The electrode was fabricated using a laboratory-made conductive ink composed of graphite (as the conductive material), glass varnish (as the polymeric binder), and an acetate sheet (as the substrate). The HG selected for this study consisted of sodium polyacrylate, a polymer commonly used for plant irrigation and decorative purposes due to its high water-retention capacity. The StPE sensors were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), while the HG was thoroughly characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDX). Additionally, the kinetic parameters of HG absorption were evaluated by fixing the hydration time at 6 h. As a proof of concept, uric acid (UA), a clinically relevant biomarker, was selected as the model analyte. A differential pulse voltammetry (DPV) method was developed to monitor UA in synthetic urine samples. The sensor exhibited a linear response in the concentration range of 2.0–10.0 µmol L⁻¹, with excellent detectability (limit of detection = 0.146 µmol L⁻¹). The method also demonstrated good precision (RSD < 4.4%) and accuracy, with recovery rates ranging from 94% to 105% in spiked samples. The sustainable characteristics of the StPE sensor, combined with its effective performance in the HG medium, highlight the potential of this platform for electrochemical analysis of other clinically, environmentally, and forensically relevant analytes, offering broad opportunities for future innovations.