Nature-Derived Hollow Micron-Tubular Signal Tracers Conquering the Size Limitations for Multimodal Immunochromatographic Detection of Antibiotics

Developing signal tracers (STAs) with large size, multifunctionality, and high retention bioaffinity is believed to be a potential solution for achieving high-performance immunochromatographic assays (ICAs). However, the size limitations of STAs on strips are always a challenge because of the serious steric hindrance. Here, based on metal-quinone coordination and further metal etching, hollow micron-tubular STAs formed by natural alizarin and Fe3+ ions (named ALIFe) are produced to break through size limitations, provide more active sites, and achieve three-mode ICAs (ALIFe STAs-ICAs). Thanks to the special tubular morphology, ALIFe can successfully pass through the strip and provide an ideal signal intensity within 7 min at low mAb and probe dosages to achieve stable ICA analysis. Importantly, ALIFe shows excellent antibody enrichment and bioaffinity retention capability. With a proof-of-concept for streptomycin, the ALIFe STAs-ICAs showed the limit of detection (LOD) at 0.39 ng mL–1 for colorimetric mode, 0.32 ng mL–1 for catalytic mode, and 0.016 ng mL–1 for photothermal mode with total recoveries ranging from 80.46 to 121.59% in mike and honey samples. We anticipate that our study will help expand the ideas for the design of high-performance STAs with large size and broaden the practical application of ICA.