Magnetic-plasmonic blackbody enhanced lateral flow immunoassay of staphylococcal enterotoxin B

Staphylococcal enterotoxin B (SEB) in food is a serious health risk, making rapid and accurate detection methods essential. Herein, we synthesized a magnetic plasmonic blackbody, Fe₃O₄@Au/PDA, by coating a gold/polydopamine (Au/PDA) layer onto an Fe₃O₄ core. This Fe₃O₄@Au/PDA exhibits broadband absorption, excellent stability, and rapid magnetic response, making it ideal for use as a magnetic separation tool and colorimetric signal amplifier. We integrated Fe₃O₄@Au/PDA into a lateral flow immunoassay (LFIA) for ultrasensitive SEB detection, combining magnetic enrichment with enhanced colorimetric signal output. The Fe₃O₄@Au/PDA-based LFIA achieved a detection limit of 0.19 ng/mL, approximately 41 times lower than traditional gold nanoparticle-based LFIA. Its real-world applicability was tested in various food samples (milk, milk powder, apple juice, and lettuce) with recoveries between 82.4 % and 111.2 % and a coefficient of variation below 12.6 %. Collectively, the designed Fe₃O₄@Au/PDA shows great promise as a novel multifunctional signal amplification label, advancing the design and development of ultrasensitive LFIA for various fields, such as food safety detection.