title: A label-free fluorescent direct detection of live Salmonella typhimurium using cascade triple trigger sequences-regenerated strand displacement amplification and hairpin template-generated-scaffolded silver nanoclusters.
abstract: The harm of Salmonella typhimurium (S. typhimurium) to public health mainly by the consumption of contaminated agricultural products or water stresses an urgent need for rapid detection methods to help control the spread of S. typhimurium. In this work, an intelligently designed sensor system took creative advantage of triple trigger sequences-regenerated strand displacement amplification and self-protective hairpin template-generated-scaffolded silver nanoclusters (AgNCs) for the first time. In the presence of live S. typhimurium, single-stranded trigger sequences were released from aptamer-trigger sequences complex, initiating a branch migration to open the hairpin template I containing complementary scaffolds of AgNCs. Then the first strand displacement amplification was induced to produce numerous scaffolds of AgNCs and reporter strands which initiated a branch migration to open the hairpin template II containing complementary scaffolds of AgNCs. Then the second strand displacement amplification was induced to generate numerous scaffolds of AgNCs and trigger sequences which initiated the third branch migration and strand displacement amplification to produce numerous scaffolds of AgNCs and reporter strands in succession. Cyclically, the reproduction of the trigger sequences and cascade successive production of scaffolds were achieved successfully, forming highly fluorescent AgNCs, thus providing significantly enhanced fluorescent signals to achieve ultrasensitive detection of live S. typhimurium down to 50 CFU/mL with a linear range from 102to 107CFU/mL. It is the first report on a fluorescent biosensor for detecting viable S. typhimurium directly, which can distinguish from heat denatured S. typhimurium. And it develops a new strategy to generate the DNA-scaffolds for forming AgNCs.
authors.affiliation: School of Life Science, Sichuan University, Chengdu 610065, PR China; Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, PR China.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.affiliation: School of Life Science, Sichuan University, Chengdu 610065, PR China; Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, PR China.
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.affiliation: School of Life Science, Sichuan University, Chengdu 610065, PR China; Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, PR China; Sichuan Academy of Animal Sciences, Chengdu 610066, PR China.
authors.forename: Xiaocheng
authors.initials: X
authors.lastname: Li
authors.affiliation: School of Life Science, Sichuan University, Chengdu 610065, PR China; Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, PR China.
authors.forename: Suzhen
authors.initials: S
authors.lastname: Ma
authors.affiliation: School of Life Science, Sichuan University, Chengdu 610065, PR China; Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, PR China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Men
authors.affiliation: School of Life Science, Sichuan University, Chengdu 610065, PR China.
authors.forename: Heng
authors.initials: H
authors.lastname: Wei
authors.affiliation: School of Life Science, Sichuan University, Chengdu 610065, PR China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Cui
authors.affiliation: School of Life Science, Sichuan University, Chengdu 610065, PR China; Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, "985 Project" Science Innovative Platform for Resource and Environment Protection of Southwestern, Chengdu 610065, PR China. Electronic address: whongning@163.com.
authors.forename: Hongning
authors.initials: H
authors.lastname: Wang
mesh_terms: D000818:Animals; D052157:Aptamers, Nucleotide / Q000737:chemistry; D015374:Biosensing Techniques / Q000379:methods*; D002645:Chickens / Q000382:microbiology; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D011200:Poultry / Q000382:microbiology*; D012480:Salmonella Infections / Q000382:microbiology; D012486:Salmonella typhimurium / Q000302:isolation & purification*; D012834:Silver / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D052157:Aptamers, Nucleotide; D005456:Fluorescent Dyes; D012834:Silver
keywords: Aptamer; Fluorescence biosensor; Label-free; Salmonella typhimurium; Silver nanocluster; Strand displacement amplification