A “three-in-one” multifunctional palladium/platinum nanoparticles-driven multimodal lateral flow immunoassays for point-of-care testing of Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a prevalent bacterium that affects patient recovery post-surgery and can cause postoperative complications. Consequently, detecting S. aureus in clinical settings is critical for ensuring patient well-being. In our work, a "visual-colorimetric-photothermal" three-in-one multimodal lateral flow immunoassays (LFIA) was developed for S. aureus detection to meet the growing demand for point-of-care testing (POCT) of bacteria in the field. The sensors relied on Pd/Pt@Ab1 NPs nanoprobes, created by decorating the surface of bimetallic nanoprobes (Pd/Pt NPs) with S. aureus antibodies (Ab1). A visual detection mode was realized by the Pd/Pt@Ab1 NPs being captured on the surface of test line (T line) using the sandwich method, offering a limit of detection (LOD) of 103 CFU/mL. Subsequently, Pd/Pt@Ab1 NPs catalyzed the TMB system into oxTMB to achieve colorimetric analysis, covering a detection range from 102-107 CFU/mL. Remarkably, the oxTMB exhibited the photothermal conversion efficiency under near-infrared (NIR) light, leading to temperature variations under 808 nm irradiation, correlating with different bacteria concentrations, with an LOD as low as 4 CFU/mL. The methodology enabled quantitative analysis of bacteria in clinical samples with satisfactory results. The diversity, complementarity, and synergy of the integrated output signals in this multimode LFIA improved the flexibility, utility, and accuracy of the assay, performing well as a POCT platform for various application scenarios.