Electrocatalytic Effect of Graphitic Carbon Nitride, MWCNTs, and Au Nanoparticle Composite on the Electroanalysis of Sleep Hormone, Melatonin in the Presence of its Precursors in Body Fluids

Abstract

Electroanalysis of melatonin, known as the sleep hormone, in the presence of its precursors, L‐tryptophan and 5‐hydroxy tryptophan in biological matrixes is an attractive research topic. The interference of voltammetric oxidation signals of these compounds, which have similar chemical structures, causes their determination to be challenging. This project aims to conduct a real‐time electroanalysis of melatonin and its precursors in biological samples using a novel nanocomposite platform. The new platform incorporates multi‐walled carbon nanotubes (MWCNTs), gold nanoparticles (GNPs), and graphitic carbon nitrides (g‐C₃N₄) placed on a glassy carbon electrode surface. The voltammetric oxidation peak of melatonin can be effectively separated from other precursors on this new surface. Thus, melatonin can be easily determined electrochemically in the presence of its precursors. In optimized conditions, this electroanalytical method displayed a linear response range between 5.0 × 10⁻⁷to 1.0 × 10⁻⁵ mol/L for both melatonin and 5‐hydroxy tryptophan and 5.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol/L for L‐tryptophan. Furthermore, the proposed modified electrode was successfully applied to determine melatonin and its precursors in various real samples such as human plasma, urine, and pharmaceutical formulations. The new sensor revealed excellent precision, remarkable simplicity, acceptable selectivity, good reproducibility, long‐term stability, and a rapid response toward melatonin, L‐tryptophan, and 5‐hydroxy tryptophan in biological matrixes.