title: Enzyme-Free Amplification by Nano Sticky Balls for Visual Detection of ssDNA/RNA Oligonucleotides.
abstract: Visual detection of nucleic acids provides simple and rapid screening for infectious diseases or environmental pathogens. However, sensitivity is the current bottleneck, which may require enzymatic amplification for targets in low abundance and make them incompatible with detection at resource-limited sites. Here we report an enzyme-free amplification that provides a sensitive visual detection of ssDNA/RNA oligonucleotides on the basis of nano "sticky balls". When target oligonucleotides are present, magnetic microparticles (MMPs) and gold nanoparticles (AuNPs) were linked together, allowing the collection of AuNPs after magnetic attraction. Subsequently, the collected AuNPs, which carry many oligonucleotides, were used as the sticky balls to link a second pair of MMPs and polymer microparticles (PMPs). Thus, because the magnetic field can attract the MMPs as well as the linked PMPs to the sidewall, the reduction of suspended PMPs yields a change of light transmission visible by the naked eye. Our results demonstrate that the limit of detection is 10 amol for ssDNAs (228 fM in 45 μL) and 75 amol for ssRNAs (1.67 pM in 45 μL). This method is also compatible with the serum environment and detection of a microRNA, miR-155, derived from human breast cancer cells. With significantly improved sensitivity for visual detection, it provides great potential for point-of-care applications at resource-limited sites.
authors.affiliation: Department of Mechanical and Biomedical Engineering, ‡Department of Biology and Chemistry, §School of Creative Media, and ∥Centre for Robotics and Automation, City University of Hong Kong , Hong Kong Special Administrative Region, China.
authors.forename: Shan
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Mechanical and Biomedical Engineering, ‡Department of Biology and Chemistry, §School of Creative Media, and ∥Centre for Robotics and Automation, City University of Hong Kong , Hong Kong Special Administrative Region, China.
authors.forename: Lok Ting
authors.initials: LT
authors.lastname: Chu
authors.affiliation: Department of Mechanical and Biomedical Engineering, ‡Department of Biology and Chemistry, §School of Creative Media, and ∥Centre for Robotics and Automation, City University of Hong Kong , Hong Kong Special Administrative Region, China.
authors.forename: Pak Piu
authors.initials: PP
authors.lastname: Yeung
authors.affiliation: Department of Mechanical and Biomedical Engineering, ‡Department of Biology and Chemistry, §School of Creative Media, and ∥Centre for Robotics and Automation, City University of Hong Kong , Hong Kong Special Administrative Region, China.
authors.forename: Zichen
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Department of Mechanical and Biomedical Engineering, ‡Department of Biology and Chemistry, §School of Creative Media, and ∥Centre for Robotics and Automation, City University of Hong Kong , Hong Kong Special Administrative Region, China.
authors.forename: Yuanye
authors.initials: Y
authors.lastname: Bao
authors.affiliation: Department of Mechanical and Biomedical Engineering, ‡Department of Biology and Chemistry, §School of Creative Media, and ∥Centre for Robotics and Automation, City University of Hong Kong , Hong Kong Special Administrative Region, China.
authors.forename: Miu Shan
authors.initials: MS
authors.lastname: Chan
authors.affiliation: Department of Mechanical and Biomedical Engineering, ‡Department of Biology and Chemistry, §School of Creative Media, and ∥Centre for Robotics and Automation, City University of Hong Kong , Hong Kong Special Administrative Region, China.
authors.forename: Pik Kwan
authors.initials: PK
authors.lastname: Lo
authors.affiliation: Department of Mechanical and Biomedical Engineering, ‡Department of Biology and Chemistry, §School of Creative Media, and ∥Centre for Robotics and Automation, City University of Hong Kong , Hong Kong Special Administrative Region, China.
authors.forename: Ting-Hsuan
authors.initials: TH
authors.lastname: Chen
mesh_terms: D004277:DNA, Single-Stranded / Q000032:analysis*; D004798:Enzymes / Q000378:metabolism*; D017276:Friction; D021621:Imaging, Three-Dimensional; D053768:Metal Nanoparticles / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D009841:Oligonucleotides / Q000032:analysis*; D010316:Particle Size; D012313:RNA / Q000032:analysis*; D013696:Temperature
chemical_list: D004277:DNA, Single-Stranded; D004798:Enzymes; D009841:Oligonucleotides; D012313:RNA
keywords: gold nanoparticles; magnetophoretic effect; microRNAs; nucleic acids; visual detection