title: A centrifugal direct recombinase polymerase amplification (direct-RPA) microdevice for multiplex and real-time identification of food poisoning bacteria.
abstract: In this study, we developed a centrifugal direct recombinase polymerase amplification (direct-RPA) microdevice for multiplex and real-time identification of food poisoning bacteria contaminated milk samples. The microdevice was designed to contain identical triplicate functional units and each unit has four reaction chambers, thereby making it possible to perform twelve direct-RPA reactions simultaneously. The integrated microdevice consisted of two layers: RPA reagents were injected in the top layer, while spiked milk samples with food poisoning bacteria were loaded into sample reservoirs in the bottom layer. For multiplex bacterial detection, the target gene-specific primers and probes were dried in each reaction chamber. The introduced samples and reagents could be equally aliquoted and dispensed into each reaction chamber by centrifugal force, and then the multiplex direct-RPA reaction was executed. The target genes of bacteria spiked in milk could be amplified at 39 °C without a DNA extraction step by using the direct-RPA cocktails, which were a combination of a direct PCR buffer and RPA enzymes. As the target gene amplification proceeded, the increased fluorescence signals coming from the reaction chambers were recorded in real-time at an interval of 2 min. The entire process, including the sample distribution, the direct-RPA reaction, and the real-time analysis, was accomplished with a custom-made portable genetic analyzer and a miniaturized optical detector. Monoplex, duplex, and triplex food poisoning bacteria (Salmonella enterica, Escherichia coli O157:H7, and Vibrio parahaemolyticus) detection was successfully performed with a detection sensitivity of 4 cells per 3.2 μL of milk samples within 30 min. By implementing the direct-PRA on the miniaturized centrifugal microsystem, the on-site food poisoning bacteria analysis would be feasible with high speed, sensitivity, and multiplicity.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea. seots@kaist.ac.kr.
authors.forename: Goro
authors.initials: G
authors.lastname: Choi
authors.forename: Jae Hwan
authors.initials: JH
authors.lastname: Jung
authors.forename: Byung Hyun
authors.initials: BH
authors.lastname: Park
authors.forename: Seung Jun
authors.initials: SJ
authors.lastname: Oh
authors.forename: Ji Hyun
authors.initials: JH
authors.lastname: Seo
authors.forename: Jong Seob
authors.initials: JS
authors.lastname: Choi
authors.forename: Do Hyun
authors.initials: do H
authors.lastname: Kim
authors.forename: Tae Seok
authors.initials: TS
authors.lastname: Seo
mesh_terms: D000818:Animals; D002498:Centrifugation; D004867:Equipment Design / Q000379:methods; D019453:Escherichia coli O157 / Q000235:genetics / Q000472:pathogenicity; D005506:Food Contamination / Q000032:analysis*; D005517:Foodborne Diseases / Q000382:microbiology*; D005798:Genes, Bacterial; D056656:Lab-On-A-Chip Devices; D008892:Milk / Q000382:microbiology*; D021141:Nucleic Acid Amplification Techniques / Q000295:instrumentation* / Q000379:methods; D016133:Polymerase Chain Reaction / Q000295:instrumentation / Q000379:methods; D045522:Recombinases / Q000235:genetics; D019779:Salmonella enterica / Q000235:genetics / Q000472:pathogenicity; D014736:Vibrio parahaemolyticus / Q000235:genetics / Q000472:pathogenicity
chemical_list: D045522:Recombinases