Rambutan-Like Magnetic Nanozyme Modified with Wheat Germ Agglutinin Enhances Lateral Flow Immunoassay for Ultrasensitive and Broad-Spectrum Detection of Respiratory Microorganisms

Detecting respiratory bacteria and viruses quickly and accurately under field conditions still faces huge challenges. Here, we developed a rambutan-like magnetic nanozyme (Fe-DAu@Ir-WGA) by coating Fe₃O₄ particles with multiple layers of 5 nm Au@Ir nanoparticles (NPs) to provide magnetic enrichment capability and numerous three-dimensional catalytic sites while applying wheat germ agglutinin (WGA) on the outer layer as a broad-spectrum recognition molecule for glycoproteins from respiratory microorganisms. The Fe-DAu@Ir-WGA probe exhibits highly efficient universal enrichment capability for bacteria and viruses (capture efficiency >90%), while effectively eliminating various matrix interferences in complex samples, thereby improving the sensitivity, reliability, and universality of the current nanozyme lateral flow immunoassay (LFA). The developed Fe-DAu@Ir-WGA-LFA can simultaneously detect respiratory bacteria (Streptococcus pneumoniae and Legionella pneumophila) and respiratory virus (SARS-CoV-2) within 38 min, achieving limits of detection of 4 cells/mL for bacteria and 1.8 pg/mL for virus. This represents at least a 555-fold increase in sensitivity compared to traditional AuNP-based LFA and approximately a 116-fold increase compared to an enzyme-linked immunosorbent assay. The practicality of the proposed assay was validated by testing various complex real-world samples and 32 clinical respiratory samples, showcasing its significant potential for broad-spectrum detection of pathogens in clinical and field settings.