Mussel-inspired Fe-based Tannic acid Nanozyme: A renewable bioresource-derived high-affinity signal tag for dual-readout multiplex lateral flow immunoassay

Lateral flow immunoassay (LFIA) is a paper-based point-of-care (POC) diagnostic tool for widespread applications. Nonetheless, the lack of multi-target monitor capability, high-affinity between signal tag and antibody, and multi-signal readout capability still remain challenges. Herein, a mussel-inspired Fe-based Tannic acid (TA) Nanozyme (FTAN) mediated dual-readout and dual-semiquantitative multiplex lateral flow immunoassay (MLFIA) was strategically fabricated by employing ractopamine (RAC) and clenbuterol (CLE) as proof-ofconcept. Avail of the environment-friendly, cost-effective, darker original color, and dual-signal readout capacity, FTAN was innovatively designed by chelating renewable bioresource TA as coupling element and Fe as active center to manufacture a multi-functional signal tag for the first time. Benefiting from the preferential protein adsorption ability of TA-Fe, the mussel-inspired nanozyme achieves satisfactory coupling efficiency and stability with antibodies. Importantly, the whole detection range was divided into several monitoring sections owing to the defined multiple detection limits (originated from on-demand outputs of colorimetric and catalytic signal) and broadened detection range, which contribute to satisfies dual-semiquantitative rapid on-site detection and various limit standards of same target in different regions. This research may contribute to the rational design of high-affinity nanozyme-based signal tags in LFIAs, the exploration of more renewable bioresourcederived nanozymes, and the extension of their applications in relevant sectors.