A Visual and Sensitive Detection of Escherichia coli Based on Aptamer and Peroxidase-like Mimics of Copper-Metal Organic Framework Nanoparticles

In order to monitor and respond rapidly to outbreaks of food-borne pathogens, establishing rapid and sensitive detection methods is becoming increasingly urgent. In this work, through the synthesis of copper-based metal-organic framework nanoparticles (Cu-MOF NPs) and functionalized with aptamers, we developed a colorimetric protocol to detect Escherichia coli. In a typical experimental procedure, aptamer 1 was immobilized onto microplate to act as capture probes. Cu-MOF NPs were synthesized and functionalized with streptavidin and biotinylated aptamer 2 to form the signal probes. In the presence of E. coli, aptamers on both capture and signal probes bind with E. coli and form a sandwich-type complex. The Cu-MOF NPs enable to catalyze the colorless peroxidase substrate to yield a colorimetric output signal. This peroxidase-like mimics-based colorimetric aptasensor showed a rapid and sensitive quantification of E. coli in the concentration range of 16~1.6 × 106 cfu/mL with a limit of quantitation (LOQ) of 16 cfu/mL and limit of detection (LOD) of 2 cfu/mL. The application of the developed assay for colorimetric measuring of milk samples was evaluated with satisfactory results. The developed Cu-MOF NPs-assisted visual method can be expected as a powerful alternative and promising tool for foodborne pathogen detection and control.