Sensitive detection of amantadine in food matrices using DTT-functionalized gold nanoparticles

Detecting amantadine (AMD) residues in food is essential due to its illegal use in livestock for disease prevention and growth promotion, practices that can lead to harmful drug residues in meat, eggs, and milk. Such residues pose significant public health concerns, including the development of drug-resistant pathogens. In this study, a highly sensitive and selective fluorometric method is presented for detecting AMD in food matrices. The assay is based on the formation of a fluorescent isoindole derivative <i>via</i> a ternary reaction between <i>o</i>-phthalaldehyde (OPA), the primary amine group of AMD, and dithiothreitol (DTT) on citrate-stabilized gold nanoparticles (C-AuNPs) functionalized with DTT (DTT@C-AuNPs) under alkaline conditions. DTT acts as a bifunctional linker, anchoring to the nanoparticle surface through one SH group, while the second SH remains available to participate in isoindole formation. This configuration results in a turn-on fluorescence system, with emission observed at <i>λ</i> _ex = 330 nm and <i>λ</i> _em = 460 nm, overcoming the typical quenching associated with AuNPs-based sensors. The method demonstrated LOD of 20 nM and high anti-interference/selectivity toward AMD, with minimal interference from matrix components. Validation through standard addition recovery experiments in AMD-spiked food samples confirmed the assay's accuracy and precision. Overall, this fluorometric platform offers a rapid, reliable, and cost-effective approach for AMD monitoring, supporting its practical application in food quality control and regulatory surveillance programs.