Lychee-shaped magneto-gold nanohybrid with highly retained magnetic-plasmonic activity for ultrasensitive and multiplex immunochromatographic assay

Utilizing nanomaterials with magnetic and plasmonic properties can significantly enhance the sensitivity of immunochromatographic assay (ICA) through magnetic enrichment, and signal amplification. Herein, we successfully synthesized a lychee-shaped magneto-gold nanohybrid (designated as MSiAuTA). This nanohybrid comprises a magnetic nanoparticle core, a flesh-fiber-like mesoporous silica template hosting numerous gold nanoparticles (AuNPs), and a lychee-exocarp-like tannic acid layer. The resultant MSiAuTA exhibits rapid magnetic response, strong plasmonic activity, and excellent biocompatibility. We further developed a multiplex ICA (mICA) platform utilizing MSiAuTA as labels for target enrichment and colorimetric signal amplification. This platform enables simultaneous and quantitative detection of Escherichia coli O157:H7 and Salmonella typhimurium . The MSiAuTA-mICA supports portable strip reader and smartphone readout and demonstrates exceptional sensitivity, achieving detection limits of 9.8 × 10 2 CFU/mL for E. coli O157:H7 and 4.9 × 10 2 CFU/mL for S. typhimurium . Additionally, we validated the accuracy, robustness, and practicality of MSiAuTA-mICA in detecting both spiked and naturally contaminated samples, including water, lettuce, chicken, apple juice, and milk. In conclusion, the lychee-shaped MSiAuTA nanohybrid shows significant promise as a versatile label for enhancing ICA’s detection capabilities in complex sample matrices.