Dual-mode immunochromatographic assay based on dendritic gold nanoparticles with superior fluorescence quenching for ultrasensitive detection of E. coli O157:H7

•The dendritic PDA-AuNPs display remarkable broadband absorption characteristics.•PDA-AuNPs with varying core sizes have impact on their ICA performance.•Absorption spectra of PDA-AuNPs overlap the excitation and emission spectra of QDs.•The colorimetric/fluorescent dual-mode immunoassay was established. We presented a colorimetric/fluorescent dual-mode immunochromatographic assay (ICA) for the sensitive detection of Escherichia coli O157:H7. The use of polydopamine (PDA)-modified gold nanoparticles (AuNPs) with broadband absorption allowed for excellent colorimetry signals for the ICA detection. Moreover, the absorption spectrum of PDA-AuNPs significantly overlaps with the excitation and emission spectra of ZnCdSe/ZnS quantum dots (QDs), resulting in effective quenching of the QDs fluorescence due to the inner filter effect. The fluorescence intensity changes induced by PDA-AuNPs were utilized for the sensitive detection of E. coli O157:H7, achieving a detection limit of 9.06 × 101 CFU/mL, which was 46-fold lower than that of traditional AuNPs-based immunoassay. The proposed immunosensor exhibited the recovery rate between 80.12% and 114.69% in detecting actual samples, indicating its reliability and satisfactory accuracy. This study provides insights into dual-mode signal outputs and the ICA development for food safety applications.