Non-enzymatic electrochemical determination of the food-related biogenic amine serotonin using a reduced graphene oxide/organic-inorganic Copper(I) phosphate composite

Abstract

Sensitive and reliable determination of serotonin (5-hydroxytryptamine, SER) in complex biological fluids remains a critical challenge for clinical diagnostics and neurochemical monitoring. Variations in serotonin levels reflect alterations in Tryptophan metabolism and gastrointestinal activity, which may be influenced by dietary factors. Herein, we report a high-performance, non-enzymatic electrochemical sensing platform based on a reduced graphene oxide-integrated organic-inorganic copper(I) phosphate composite (NTOU10@RGO). The NTOU10@RGO hybrid was fabricated via a facile one-step ultrasonication strategy, enabling intimate interfacial coupling between the redox-active copper phosphate framework and the highly conductive reduced graphene oxide (RGO) network. Owing to this synergistic architecture, the NTOU10@RGO-modified electrode exhibits markedly enhanced electron-transfer kinetics and electrocatalytic activity toward SER oxidation. The resulting sensor demonstrates a wide linear detection range from 0.05 to 100 mu M, an ultralow detection limit of 3.3 nM (S/ N=3), and excellent selectivity against common electroactive interferents. Notably, the sensor maintains high reproducibility, long-term operational stability, and robust performance under physiological pH conditions. Practical applicability is validated through accurate SER determination in human saliva, urine, and blood plasma, with satisfactory recoveries, highlighting the sensor's capability for real-sample analysis. This work introduces a versatile organic-inorganic hybrid sensing strategy that combines structural robustness with superior electrochemical activity, offering a promising route toward cost-effective and enzyme-free neurotransmitter sensing platforms for biomedical diagnostics.