Sustainable Xanthine-Grafted Alginate Biosensing Platform for Metabolic Disorder Diagnostics

This work describes the development of an efficient, durable, and highly sustainable electrochemical biosensing platform for the detection of uric acid (UA), sodium alginate (Alg), which is functionalized with an allyl derivative of xanthine to yield AlgX. The entire synthesis process is notably eco-biocompatible, utilizing water as the solvent and green reagents, such as H₂O₂ and ascorbic acid. AlgX was subsequently complexed with Cu²⁺ ions to form AlgXCu, resulting in an active material with a very low metal content, calculated to be only 4.8% through inductively coupled plasma mass spectrometry. Electrochemical characterization of the AlgXCu/SPCE (screen-printed carbon electrode) sensor demonstrated good performance for UA detection. Differential pulse voltammetry results show a high sensitivity of 14.28 μA μM^-1 cm^-2 and a remarkably low limit of detection (LOD) of 0.025 μM. This LOD is a good value for copper-based sensors, even compared to those with a higher copper content. Furthermore, the sensor exhibited very good selectivity and the capability to detect UA and dopamine (DA) simultaneously. Its applicability was validated in synthetic saliva and urine samples, demonstrating high accuracy and recovery rates (recovery between 97.9 and 105%) and excellent reproducibility (RSD ≤ 2.4%).