‘Three-to-one’ Multi-Functional Nanocomposite-Based Lateral Flow Immunoassay for Label-Free and Dual-Readout Detection of Pathogenic Bacteria

Sandwich lateral flow immunoassays (LFIAs) based on paired antibodies are the most frequently used platform for food-borne pathogen detection. Although label-free strategies are used in LFIAs to avoid the utilization of paired antibodies, challenges of probe design and detection reliability still remain. Here, we report a new label free and dual-readout LFIA (LD-LFIA) mediated by a 'Three-To-One' multi-functional nanocomposite with a unique combination of magnetic-adhesion-color-nanozyme properties. The strengths of the new designed nanocomposite are: (i) the Fe3O4 magnetic core simplifies the separation processes; (ii) surface adherent poly dopamine (PDA) films exhibit a strong adhesion to pathogenic bacteria and provide colorimetric detection signal; and (iii) the deposited platinum nanoparticles (Pt NPs) can function as nanozymes to generate an extra catalytic signal for constructing a dual-readout mode to improve the detection accuracy. The resulting Fe3O4@PDA@Pt nanocomposite-based LD-LFIA can detect highly pathogenic Escherichia coli O157:H7 with limits of detection of 102 and 10 CFU mL(-1) for colorimetric and catalytic quantitative analyses, respectively. Systematic results also reveal that the proposed method exhibited high specificity and applicability for drinking water and chicken samples, serving as a promising tool for real bacterial sample testing. The multi-functional Fe3O4@PDA@Pt nanocomposite-based LD-LFIA can provide new ideas for designing new multi-functional probes for improving detection performance of conventional label-free LFIA and constructing more accurate and sensitive detection systems.