Dual‐Spectrum Fluorescence Quenching of Aggregation‐Induced Emission Nanoparticles for Dual‐Signal Lateral Flow Immunoassay of Danofloxacin in Meat Samples

The conventional gold nanoparticle‐based lateral flow immunoassay (AuNPs‐LFIA) is hampered by single colorimetric signal readout and insufficient sensitivity, restricting its broad application in trace detection for food safety. Herein, an AuNPs‐triggered dual‐spectrum fluorescence quenching LFIA (DSFQ‐LFIA) was constructed for colorimetric and fluorescent detection of danofloxacin (DAN) in meat samples. Aggregation‐induced emission nanoparticles (AIENPs) were synthesized using tetramethyl 4′,4‴,4‴″,4‴″″‐(ethene‐1,1,2,2‐tetrayl)tetrakis([1,1′‐biphenyl]‐4‐carbomethoxy) (TCBPE) as an AIE luminogen (AIEgen). The engineered TCBPE molecules with a low highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap were featured for the notable AIE effect, conferring AIENPs with a high quantum yield (67.2%). AuNPs acted as an efficient fluorescence quencher owing to the substantial dual‐spectrum overlap between the absorption band of AuNPs and excitation/emission spectra of AIENPs. In the absence of DAN, antibody‐labeled AuNPs (AuNPs‐Ab) were bound to the test (T) line, causing the notable fluorescence quenching of AIENPs. Conversely, the presence of DAN left AIENPs largely unquenched. The limits of detection (LODs) of DSFQ‐LFIA were 0.012 ng mL −1 (fluorescence mode) and 0.032 ng mL −1 (colorimetric mode). It presents a rapid and sensitive approach for detecting trace contaminants in food matrices.