"Three-in-One" MIL@PDA-UiOL@AIEgens driven lateral flow immunosensor for multimodal detection of aflatoxin B₁

The multi-modal lateral flow immunosensor (LFIS) with integrated advantages and mutual built-in calibration ability could avoid the limitations of traditional single-signal output mode to meet the growing demands for trace contaminants. In this study, an innovative "three-in-one" LFIS platform was developed for colorimetric, grayscale, and fluorescent detection of aflatoxin B₁ (AFB₁). It integrated polydopamine (PDA)-coated ferric metal-organic framework (MOF) (MIL@PDA) and the functionalized zirconium MOF of a UiO linker enriched with abundant AIEgens (UiOL@AIEgens) as signal probes. The synthesized MIL and UiOL with large surface area and high porosity could enrich numerous PDA and AIEgens probes, respectively, for signal amplification, not only significantly enhancing the colorimetric signal outputs, and grayscale and fluorescence responses, but also largely improving the detection sensitivity and analytical accuracy. The MIL@PDA-monoclonal antibodies (mAbs) probes could specifically identify AFB₁ antigens on the test (T) line to produce a visible dark-grey band for qualitative colorimetric detection, and the grayscale intensities were monitored for the quantitation of AFB₁ via a portable device. The fluorescence mode was realized through the MIL@PDA-mAbs probes quenching the fluorescence of UiOL@AIEgens on the T line, and the fluorescence intensities were recorded by using a smartphone for accurate quantitation. Under optimal conditions, this MIL@PDA-UiOL@AIEgens driven three-modal LFIS platform allowed for AFB₁ detection in a wide range of 0.01-5 ng/mL with a low limit of detection of 0.01 ng/mL that was more than 59-fold lower than the traditional AuNPs-based LFIS. The feasibility and practicability of this LFIS platform was verified for AFB₁ detection in lotus seeds. This study opened up a new avenue for developing high-performance LFIS platforms for the trace detection more harmful analytes in complex matrices.