title: Precipitation of PEG/Carboxyl-Modified Gold Nanoparticles with Magnesium Pyrophosphate: A New Platform for Real-Time Monitoring of Loop-Mediated Isothermal Amplification.
abstract: Gold nanoparticles have proven to be promising for decentralized nucleic acid testing by virtue of their simple visual readout and absorbance-based quantification. A major challenge toward their practical application is to achieve ultrasensitive detection without compromising simplicity. The conventional strategy of thermocycling amplification is unfavorable (because of both instrumentation and preparation of thermostable oligonucleotide-modified gold nanoparticle probes). Herein, on the basis of a previously unreported co-precipitation phenomenon between thiolated poly(ethylene glycol)/11-mercaptoundecanoic acid co-modified gold nanoparticles and magnesium pyrophosphate crystals (an isothermal DNA amplification reaction byproduct), a new ultrasensitive and simple DNA assay platform is developed. The binding mechanism underlying the co-precipitation phenomenon is found to be caused by the complexation of carboxyl and pyrophosphate with free magnesium ions. Remarkably, poly(ethylene glycol) does not hinder the binding and effectively stabilizes gold nanoparticles against magnesium ion-induced aggregation (without pyrophosphate). In fact, a similar phenomenon is observed in other poly(ethylene glycol)- and carboxyl-containing nanomaterials. When the gold nanoparticle probe is incorporated into a loop-mediated isothermal amplification reaction, it remains as a red dispersion for a negative sample (in the absence of a target DNA sequence) but appears as a red precipitate for a positive sample (in the presence of a target). This results in a first-of-its-kind gold nanoparticle-based DNA assay platform with isothermal amplification and real-time monitoring capabilities.
authors.affiliation: Interdisciplinary Division of Biomedical Engineering, ‡Department of Health Technology and Informatics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Ailin
authors.initials: A
authors.lastname: Qin
authors.affiliation: Interdisciplinary Division of Biomedical Engineering, ‡Department of Health Technology and Informatics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Lok Tin
authors.initials: LT
authors.lastname: Fu
authors.affiliation: Interdisciplinary Division of Biomedical Engineering, ‡Department of Health Technology and Informatics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Jacky K F
authors.initials: JK
authors.lastname: Wong
authors.affiliation: Interdisciplinary Division of Biomedical Engineering, ‡Department of Health Technology and Informatics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Li Yin
authors.initials: LY
authors.lastname: Chau
authors.affiliation: Interdisciplinary Division of Biomedical Engineering, ‡Department of Health Technology and Informatics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Shea Ping
authors.initials: SP
authors.lastname: Yip
authors.affiliation: Interdisciplinary Division of Biomedical Engineering, ‡Department of Health Technology and Informatics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Thomas M H
authors.identifier: http://orcid.org/0000-0003-3950-0232
authors.initials: TM
authors.lastname: Lee
mesh_terms: D011756:Diphosphates / Q000737:chemistry*; D006046:Gold; D017616:Magnesium Compounds / Q000737:chemistry*; D053768:Metal Nanoparticles; D021141:Nucleic Acid Amplification Techniques; D011092:Polyethylene Glycols
chemical_list: D011756:Diphosphates; D017616:Magnesium Compounds; D011092:Polyethylene Glycols; D006046:Gold; C034732:magnesium pyrophosphate
keywords: DNA detection; gold nanoparticles; isothermal amplification; magnesium pyrophosphate; point-of-care nucleic acid testing; precipitation-based readout; real-time LAMP