Hierarchical porous GO-MONs-NH2 composite for efficient solid-phase extraction of aromatic amino acids: A novel approach to biomarker detection in depression.

Aromatic amino acids (AAAs) play a critical role in neurotransmitter synthesis and are implicated in the pathogenesis of depression. However, their trace concentrations in biological samples pose significant challenges for detection. In this study, we present a novel approach for the sensitive and precise detection of AAAs in human urine. A composite material, GO-MONs-NH2, was synthesized by in situ growing amino-functionalized microporous organic networks (MONs-NH2) on the surface of graphene oxide (GO) via a solvothermal method. The resulting GO-MONs-NH2 material, with a hierarchical porous structure, combines the mechanical stability of GO and the high adsorption capacity of MONs-NH2. It efficiently extracts AAAs through multiple adsorption mechanisms, including hydrogen bonding, π-π interactions, and electrostatic forces, exhibiting rapid mass transfer and high affinity for tyrosine, phenylalanine, and tryptophan. The GO-MONs-NH2 solid-phase extraction (SPE) technique, coupled with high-performance liquid chromatography-diode array detection (HPLC-DAD), enables simultaneous detection of the three AAAs in urine samples without the need for mass spectrometry. The developed method demonstrates a wide linear range (0.05-50 μg/mL), low limits of detection (3.96-7.13 ng/mL), high accuracy (recoveries: 90.8 %-107.5 %), and good precision (RSDs ≤ 6.4 %). This method offers a reliable, cost-effective, and non-invasive tool for early screening and monitoring of depression.