“Lighting-up” methylene blue-embedded zirconium based organic framework triggered by Al3+ for advancing the sensitivity of E. coli O157:H7 analysis in dual-signal lateral flow immunochromatographic assay

The sensitive detection of foodborne pathogens is of great significance for ensuring food safety and quality. Herein, on the basis of methylene blue-embedded zirconium based organic framework ( [email protected] ) as the remarkable capture carrier and signal indicator, with the Al 3+ -assisted the fluorescent signal response, we developed a label-free and dual-signal lateral flow immunochromatographic assay (LDLFIA) for sensitive detection of Escherichia coli ( E. coli ) O157:H7. The [email protected] sensing carrier without monoclonal antibodies (mAbs) was manufactured, which adhered to bacteria to form the [email protected] E. coli O157:H7 conjugate, resulting in visible blue band. Then the fluorescent response of the OH-rich [email protected] was excited by introducing Al 3+ , arising from capturing of Al 3+ by -OH through coordination and electrostatic affinity, thus generating a green fluorescent band. Impressively, a smartphone-based portable reading system was developed that can reflect the test results of [email protected] immediately. Under optimum conditions, [email protected] can complete colorimetric and fluorescent mode detection within 90 min, with a detection sensitivity of 10 3 CFU/mL, which were 100 times lower than traditional gold nanoparticles-based LFIA and polymerase chain reaction (PCR). Moreover, the feasibility of the method was further evaluated by the determination of E. coli O157: H7 in drinking water and cabbage with average recoveries of 85.1-123.0%.