Two birds with one stone: Gold “bridging” both nanozyme and immunosensor for sensitive double-response detection of T-2 toxin

Developing immunosensors with nanozymes as signal labels has made a great deal of progress and is no longer a novel concept. But even then, several research obstacles, e.g., suboptimal activity, uncertain antibody coupling, and redundant processes, still remain and must be tackled in this frontier. In this study, we constructed a colorimetric and fluorescent double-response enzyme-linked immunosorbent assay using CeO2@Au heterojunctions as signal labels (CeO2@Au-TFNLISA) for sensitive detection of T-2 toxin. Gold nanoparticles (AuNPs) acting as a bridge for CeO2 can connect and realize the bidirectional improvement of CeO2@Au heterojunctions: (1) enhancing the nanozyme activity significantly by multiple effects (charge transfer, AuNPs assistance, substrate affinity, and oxygen vacancy, etc.); (2) improving the affinity between antibodies and labels through electrostatic incorporation. Meanwhile, in this system, nanozyme catalysis generates the first signal, and fluorescence quenching forms the second signal via the inner-filter effect (IFE) to avoid the inaccuracy result brought on by the off-laboratory environment. The CeO2@Au-TFNLISA has increased the sensitivity by 42 and 18 times in colorimetric (TNLISA) and fluorescent modes (FNLISA) compared with traditional ELISA (0.00852 ng/mL for TNLISA, 0.02011 ng/mL for FNLISA, 0.36492 ng/mL for traditional ELISA), respectively, and saved half of the detection time (from 135 min to 50 min) due to the weakened non-specific adsorption. As a result, the CeO2@Au-TFNLISA method is expected to gain strong momentum to advance the rapid and precise detection of T-2 in food.