Fishnet-like 2D magnetic nanozyme probe enables ultrasensitive bedside immunodiagnosis of bone infection pathogens

Rapid, early, and accurate bedside diagnosis of bone infections is an urgent clinical need that remains unmet. Here, we present a fishnet-like two-dimensional magnetic nanozyme (FGDAI) that integrates three functional modules: a monolayer graphene oxide substrate providing a large reaction interface; an Fe₃O₄ interlayer conferring efficient magnetic enrichment; and two dense layers of Au@Ir nanoparticles furnishing abundant catalytic sites that act synergistically with the Fe₃O₄ to enable catalytic enhancement. This architecture delivers multiple signal amplification-"large reaction interface, magnetic enrichment, synergistic enhancement"-within an immunochromatographic assay (ICA), effectively overcoming the sensitivity and robustness limitations of traditional colorimetric ICAs when challenged by complex clinical matrices. In addition, wheat germ agglutinin (WGA) was immobilized on the 2D FGDAI surface via lyophilization as a universal peptidoglycan recognition molecule, enabling efficient, broad-spectrum bacterial binding and thereby mediating ultrasensitive, simultaneous ICA detection of two important bone-infection pathogens (<i>Staphylococcus aureus</i> and <i>Pseudomonas aeruginosa</i>). FGDAI-WGA-ICA completes testing in under 25 min with a visual limit of detection of 10 cells/mL, exhibiting high sensitivity and specificity for the target pathogens. Moreover, validation in a cohort of 83 synovial fluid samples showed high concordance with clinical reference methods, supporting its potential for real-time, bedside diagnosis of bone infections.