Lateral flow immunoassay based on polydopamine-coated metal–organic framework for the visual detection of enrofloxacin in milk

Herein, we report a new polydopamine (PDA)-coated metal–organic framework (MOF) as a label to improve the sensitivity of lateral flow immunoassay (LFIA). The MOF, UiO-66-NH 2 , was synthesized via the hydrothermal method, and it exhibited the advantageous features of ordered pore structure, strong absorbance, and high specific surface area. Subsequently, UiO-66-NH 2 was coated with PDA to improve the antibody coupling effectivity and light absorption ability. The optical intensity and antibody coupling efficiency of UiO-66@PDA were superior to those of gold nanoparticles (AuNPs). Under the optimum condition, the limit of detection and cutoff value of UiO-66@PDA-LFIA in detecting enrofloxacin were 0.045 and 1.0 ng/mL, respectively, which were lower than those of AuNPs-LFIA (0.095 and 5 ng/mL). The recoveries of UiO-66@PDA-LFIA in low-fat milk and whole milk were 85.6–107.4% and 79.3–115.5%, respectively, with coefficients of variation of 2.91–9.59% and 3.91–11.8%, respectively, as further confirmed by liquid chromatography–tandem mass spectrometry. These results indicate that UiO-66@PDA can be used as a novel probe for LFIA development and applications. Graphical abstract