G-quadruplex-based assay combined with aptamer and gold nanoparticles for Escherichia coli K88 determination
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ORIGINAL PAPER
G-quadruplex-based assay combined with aptamer and gold nanoparticles for Escherichia coli K88 determination Zefeng Wang 1 & Qiujun Lu 1,2 & Tao Xu 1 & Feiying Wang 1 & Fangfang Huang 1 & Yanling Peng 1 & Le Deng 1 Received: 5 November 2019 / Accepted: 22 April 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract A colorimetric method was developed using G-quadruplex and gold nanoparticles (AuNPs) for determination of Escherichia coli K88 (ETEC K88). It was composed of two modules: (1) an aptamer as biorecognizing element and (2) a capturing DNA (modified with AuNPs at 5′) as a transducer. In the absence of target bacteria, the aptamer can form stable double strands with capturing DNA, preventing the binding of capturing DNA to the G-quadruplex. However, the double strands of capturing DNA and aptamer are untied due to the stronger binding of aptamers to bacteria in the presence of target bacteria. As a result, the Gquadruplex binds to capture DNA and leads to the aggregation and color change of AuNPs, which can be monitored by a spectrophotometer or visualization. The quantitative determination was achieved by monitoring the optical density change of AuNPs solution at 524 nm after target addition. Under optimal conditions, the method has a low detection limit (1.35 × 102 CFU mL−1) and a linear response in the range 102 to 106 CFU mL−1. Keywords Intermolecular G-quadruplex . Visualization . Aptamer . Colorimetric method . Bacteria
Introduction Food-borne diseases caused by pathogenic microorganisms are one of most important reasons affecting human health, in which diarrheal disease kills about 2.2 million people each year and most of them are children [1]. The bacterial infections can lead to diseases such as diarrhea, and all kinds of food and water are the main carriers of transmission [2]. ETEC K88 is one of the most common intestinal pathogens, which can produce enterotoxins and lead to intestinal electrolyte imbalance, diarrhea, and even death. Therefore, rapid and sensitive determination of ETEC K88 is essential to ensure the Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00604-020-04291-x) contains supplementary material, which is available to authorized users. * Le Deng [email protected] 1
State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha 410081, Hunan, People’s Republic of China
2
Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, People’s Republic of China
safety of food and water, as well as timely and accurate disease diagnosis and treatment [3]. The traditional determination methods for it are usually dyeing, culture, biochemical identification, and so on [4]. Although having the advantages of high accuracy, simple operation, and no need for large instruments, they usually take a long time (from a f
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