High-Density Au Anchored to Ti3C2-Based Colorimetric-Fluorescence Dual-Mode Lateral Flow Immunoassay for All-Domain-Enhanced Performance and Signal Intercalibration

In this work, a novel MXene-Au nanoparticle (Ti3C2@Au) was synthesized with a high molar extinction coefficient, strong fluorescence quenching ability, ultrahigh antibody affinity, high stability, and good dispersibility, and it was used to develop a colorimetric-fluorescence dual-mode lateral flow immunoassay (LFIA). The detection limits of this method for the detection of dexamethasone in milk, beef, and pork were 0.0018, 0.12, and 0.084 μg/kg in the “turn-off” mode (colorimetric signal), and 0.0013, 0.080, and 0.070 μg/kg in the “turn-on” mode (fluorescent signal), respectively, which was up to 231-fold more sensitive compared with that of the reported LFIAs. The recovery rates ranged from 81.1–113.7%, and 89.2–115.4%, with the coefficients of variation ranging from 1.4–15.0%, and 1.9–14.8%, respectively. The results of the LC-MS/MS confirmation test on 30 real samples had a good correlation with that of our established method (R2 > 0.97). This work not only developed novel nanocarriers for antibody-based LFIA but also ensured high-performance detection.