Highly Sensitive and Ultrastable Lateral Flow Immunoassay Based on Polydopamine-Coated Aggregation-Induced Emission Fluorescent Microspheres with Excellent Fluorescence Performance and Biofriendly Coupling Strategy

Conventional fluorescent microspheres (CFMs) have the disadvantages of low photoluminescence intensity (aggregation-caused quenching) and poor antibody conjugation. Herein, we achieved the improved performance of lateral flow immunoassay (LFIA) based on the high-fluorescent property of aggregation-induced emission fluorescent microspheres (AIEFMs) and biofriendly antibody coupling strategy of the polydopamine (PDA) layer. Although the PDA layer quenches the fluorescence intensity of AIEFM by Förster resonance energy transfer (FRET), quenching can be effectively controlled by ingenious adjusting of the thickness of the PDA. The PDA-coated AIEFM (AIEFM@PDA), which not only retained the strong fluorescence of AIEFM but also improved the antibody coupling efficiency and reproducibility of LFIAs, was successfully applied in sandwich and competitive LFIAs for the highly sensitive detection of pathogenic bacteria (Escherichia coli O157:H7) and antibiotics (enrofloxacin). In comparison with the CFM method, the proposed AIEFM@PDA-LFIA for the detection of E. coli O157:H7 and enrofloxacin could enhance the sensitivity by 40 times and 20 times, respectively. In addition, AIEFM@PDA-LFIA was further used for the detection of E. coli O157:H7 in river water, apple juice, and milk with satisfactory recoveries from 82.24 to 123.02% and enrofloxacin in pork, chicken, fish, and beef with satisfactory recoveries from 75.67 to 120.89%. The proposed AIEFM@PDA-LFIA showed excellent potential in rapid detection applications.