Fe ₃ O ₄ Composite Nanostructures-Enabled Fluorescence Quenching Lateral Flow Immunoassay for Sensitive Detection of Albendazole Residues In Agri-Food Products

This study successfully synthesized Fe₃O₄@Au, Fe₃O₄@Se, and Fe₃O₄@MnO₂ nanostructures with inherent oxidation properties of Fe₃O₄ nanoparticles. These nanostructures exhibited plasmonic properties, facilitating visible light absorption and spectral overlap with quantum dots fluorescent microspheres (QD-FMs) for quenching QD-FMs via an inner filter effect. Based on the composite nanostructures, we developed dual-mode (colorimetric, CM, "turn off" mode; fluorescence quenching, FQ, "turn on" model) LFIA platforms. Among them, the Fe₃O₄@Au-based FQ-LFIA demonstrated superior sensitivity for albendazole (ABZ) which is a veterinary with a detection limit of 0.072 ng mL⁻¹, 69.4-fold lower than Fe₃O₄@Au-CM-LFIA (5 ng mL⁻¹). The result is attributed to the high molar extinction coefficient (8.877 × 10¹¹ M⁻¹ cm⁻¹), strong quenching efficiency (η = 92.2%), and high quenching constants (Kn = 67.236) of Fe₃O₄@Au. The assay also demonstrated satisfactory recovery (80.4-108.6%) and precision (CV < 13%) for the detection of ABZ in actual samples. The developed Fe₃O₄@Au-FQ-LFIA is effective for detecting ABZ in agri-food products.