PH-responsive nanoparticles and automated detection apparatus for dual detection of pathogenic bacteria

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Escherichia coli (E. coli) and Salmonella typhimurium (S. T) are the two most widely polluted pathogenic bacteria, which seriously threat human food safety, so the dual prevention and monitoring of pathogenic bacteria is of great research significance. In this paper, two types of pH-responsive nanoparticles (NPs) were prepared, using aptamers as recognition molecule, pH indicators as carrier, which can quickly respond to pathogenic bacteria and exhibit different color variations. A colorimetric sensor was constructed with 96-well plates, and the signal amplification was realized by sandwich method. Importantly, we have developed an automatic device for dual detection of pathogenic bacteria, which can control the mechanical arm through NEMO software to complete the experimental operations such as sample absorption, incubation and elution, the whole detection process realizes one-button operation. The automatic device and colorimetric sensor were used to detect E. coli and S. T, and the low detection limit was achieved as low as 1 CFU/mL. The spiked samples were detected in order to further evaluate the feasibility of the method and equipment, and the recoveries were in the range of 90.8–101.256%. This work effectively improves the efficiency of pathogen detection, completely gets rid of the dependence on professionals, and is conducive to promoting the development of the detection industry in the direction of automation, convenience and high-throughput, with a wide range of application scenarios.