title: A label-free ultrasensitive fluorescence detection of viable Salmonella enteritidis using enzyme-induced cascade two-stage toehold strand-displacement-driven assembly of G-quadruplex DNA.
abstract: The harm of Salmonella enteritidis (S. enteritidis ) to public health mainly by contaminating fresh food and water emphasizes the urgent need for rapid detection techniques to help control the spread of the pathogen. In this assay, an newly designed capture probe complex that contained specific S. enteritidis-aptamer and hybridized signal target sequence was used for viable S. enteritidis recognition directly. In the presence of the target S. enteritidis, single-stranded target sequences were liberated and initiated the replication-cleavage reaction, producing numerous G-quadruplex structures with a linker on the 3'-end. And then, the sensing system took innovative advantage of quadratic linker-induced strand-displacement for the first time to release target sequence in succession, leading to the cyclic reuse of the target sequences and cascade signal amplification, thereby achieving the successive production of G-quadruplex structures. The fluorescent dye, N-Methyl mesoporphyrin IX, binded to these G-quadruplex structures and generated significantly enhanced fluorescent signals to achieve highly sensitive detection of S. enteritidis down to 60 CFU/mL with a linear range from 10(2) to 10(7)CFU/mL. By coupling the cascade two-stage target sequences-recyclable toehold strand-displacement with aptamer-based target recognition successfully, it is the first report on a novel non-label, modification-free and DNA extraction-free ultrasensitive fluorescence biosensor for detecting viable S. enteritidis directly, which can discriminate from dead S. enteritidis.
authors.affiliation: College of Life Sciences, Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Sichuan University, Chengdu 610065, China; Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, Chengdu 610065, China; "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.affiliation: College of Life Sciences, Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Sichuan University, Chengdu 610065, China; Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, Chengdu 610065, China; "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.affiliation: College of Life Sciences, Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Sichuan University, Chengdu 610065, China; Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, Chengdu 610065, China; "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, China.
authors.forename: Suzhen
authors.initials: S
authors.lastname: Ma
authors.affiliation: College of Life Sciences, Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Sichuan University, Chengdu 610065, China; Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, Chengdu 610065, China; "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Men
authors.affiliation: College of Life Sciences, Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Sichuan University, Chengdu 610065, China; Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, Chengdu 610065, China; "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, China.
authors.forename: Qingzhou
authors.initials: Q
authors.lastname: Li
authors.affiliation: College of Life Sciences, Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Sichuan University, Chengdu 610065, China; Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, Chengdu 610065, China; "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Yang
authors.affiliation: College of Life Sciences, Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Sichuan University, Chengdu 610065, China; Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, Chengdu 610065, China; "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, China. Electronic address: whongning@163.com.
authors.forename: Hongning
authors.initials: H
authors.lastname: Wang
authors.affiliation: College of Life Sciences, Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Sichuan University, Chengdu 610065, China; Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, Chengdu 610065, China; "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, China.
authors.forename: Anyun
authors.initials: A
authors.lastname: Zhang
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry; D015374:Biosensing Techniques; D005456:Fluorescent Dyes / Q000737:chemistry; D054856:G-Quadruplexes; D006801:Humans; D008652:Mesoporphyrins / Q000737:chemistry; D021141:Nucleic Acid Amplification Techniques; D012480:Salmonella Infections / Q000175:diagnosis* / Q000382:microbiology; D012477:Salmonella enteritidis / Q000302:isolation & purification*
chemical_list: D052157:Aptamers, Nucleotide; D005456:Fluorescent Dyes; D008652:Mesoporphyrins; C031468:mesoporphyrin IX
keywords: Aptamer; Fluorescence biosensor; G-quadruplex; Label-free; Salmonella enteritidis; Toehold strand-displacement