Ultrasensitive and Specific Phage@DNAzyme Probe-Triggered Fluorescent Click Chemistry for On-Site Detection of Foodborne Pathogens Using a Smartphone

Rapid, specific, and on-site detection of virulent foodbornepathogenicstrains plays a key role in controlling food safety. In this work,an ultrasensitive and specific Phage@DNAzyme signal probe was designedto detect foodborne pathogens. The proposed sensing probe was composedof the selected phage and functionalized DNAzyme, which realized thespecific recognition of target foodborne pathogens at the strain leveland the efficient catalysis of copper(II) based azide-alkyne cycloaddition(CuAAC) click reaction with fluorescent signal, respectively. As aproof of concept, the virulent Escherichia coli O157:H7 (E. coli O157:H7) as therepresentative analyte was first enriched and purified from the complexfood samples by a 4-mercaptophenylboronic acid-modified gold slide.Following, the Phage@DNAzyme probes were specifically combined withthe captured E. coli O157: H7 and catalyzedthe click reaction between 3-azido-7-hydroxycoumarin and 3-butyn-1-olwith the assistance of Cu(II) to generate a visual fluorescent signal.Finally, the corresponding fluorescent signals were measured by asmartphone to quantify the target concentrations. Under optimizedconditions, the bioassay exhibited a wide linear range from 10(2) to 10(8) CFU/mL and the detection limit was 50 CFU/mL(S/N = 3). It was further extendedto the detection of another foodborne pathogen Salmonellatyphimurium with satisfying sensing performances.This work gives a new path for developing rapid, specific, and on-sitedetection methods for trace levels of pathogenic strains in foods.