DNAzyme-powered AuNR-DNA walker for visual detection of Escherichia coli

Abstract

Escherichia coli (E. coli) is a common Gram-negative bacterium that is widely distributed in nature and is susceptible to natural and random genetic factors. It is a pathogenic factor for many diseases. Sensitive and specific detection of E. coli is an important means to ensure food safety and prevent foodborne disease outbreaks. Ultrasensitive and specific detection of E. coli is still an urgent problem that needs to be solved. An intuitive and convenient colorimetric assay method with high sensitivity based on a DNAzyme-powered AuNR-DNA walker is proposed here for detection of E. coli. The strategy, dependent on the targeted activation of Mg²⁺-DNAzyme, starts an efficient DNA walking machine, induces the formation of countless peroxidase-mimicking enzymes, and produces a color change via a chromogenic reaction for visual detection of E. coli. This strategy features several aspects. First, this is the first time that an AuNR-based DNA walker is integrated with a colorimetric assay of E. coli. By combining the DNAzyme-powered AuNR-DNA walker and visual detection via the peroxidase-mimicking enzyme, the detection sensitivity is significantly improved compared to those of previously reported colorimetric-based methods, which provides a paradigm for the development of highly sensitive colorimetric assay methods. Second, an activity-controlled nano-DNAzyme is constructed via target-triggered formation of G-quadruplex DNAzyme to achieve low background and high signal-to-noise detection. In addition, this strategy has the advantages of simple operation, short analysis time, low cost, and easy on-site detection. Therefore, the proposed strategy has the potential for application in the detection of E. coli and related food safety analysis and clinical diagnosis.