title: Colorimetric detection of mercury ion based on unmodified gold nanoparticles and target-triggered hybridization chain reaction amplification.
abstract: A novel unmodified gold nanoparticles (AuNPs)-based colorimetric strategy for label-free, specific and sensitive mercury ion (Hg(2+)) detection was demonstrated by using thymine-Hg(2)(+)-thymine (T-Hg(2)(+)-T) recognition mechanism and hybridization chain reaction (HCR) amplification strategy. In this protocol, a structure-switching probe (H0) was designed to recognize Hg(2+) and then propagated a chain reaction of hybridization events between two other hairpin probes (H1 and H2). In the absence of Hg(2+), all hairpin probes could stably coexist in solution, the exposed sticky ends of hairpin probes were capable of stabilizing AuNPs. As a result, salt-induced AuNPs aggregation could be effectively prevented. In the presence of Hg(2+), thymine bases of H0 could specifically interact with Hg(2+) to form stable T-Hg(2)(+)-T complex. Consequently, the hairpin structure of H0 probe was changed. As H1/H2 probes were added, the HCR process could be triggered and nicked double-helixes were formed. Since it was difficult for the formed nicked double-helixes to inhibit salt-induced AuNPs aggregation, a red-to-blue color change was observed in the colloid solution as the salt concentration increased. With the elegant amplification effect of HCR, a detection limit of around 30 nM was achieved (S/N=3), which was about 1-2 orders of magnitudes lower than that of previous unmodified AuNPs-based colorimetric methods. By using the T-Hg(2)(+)-T recognition mechanism, high selectivity was also obtained. As an unmodified AuNPs-based colorimetric strategy, the system was simple in design, convenient in operation, and eliminated the requirements of separation processes, chemical modifications, and sophisticated instrumentations.
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry & Chemical Engineering, Key Laboratory for Bio-Nanotechnology and Molecular Engineering of Hunan Province, Hunan University, Changsha 410082, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry & Chemical Engineering, Key Laboratory for Bio-Nanotechnology and Molecular Engineering of Hunan Province, Hunan University, Changsha 410082, China.
authors.forename: Xiaohan
authors.initials: X
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry & Chemical Engineering, Key Laboratory for Bio-Nanotechnology and Molecular Engineering of Hunan Province, Hunan University, Changsha 410082, China.
authors.forename: Xiaohai
authors.initials: X
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry & Chemical Engineering, Key Laboratory for Bio-Nanotechnology and Molecular Engineering of Hunan Province, Hunan University, Changsha 410082, China.
authors.forename: Pei
authors.initials: P
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry & Chemical Engineering, Key Laboratory for Bio-Nanotechnology and Molecular Engineering of Hunan Province, Hunan University, Changsha 410082, China. Electronic address: kmwang@hnu.edu.cn.
authors.forename: Kemin
authors.initials: K
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry & Chemical Engineering, Key Laboratory for Bio-Nanotechnology and Molecular Engineering of Hunan Province, Hunan University, Changsha 410082, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry & Chemical Engineering, Key Laboratory for Bio-Nanotechnology and Molecular Engineering of Hunan Province, Hunan University, Changsha 410082, China.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry & Chemical Engineering, Key Laboratory for Bio-Nanotechnology and Molecular Engineering of Hunan Province, Hunan University, Changsha 410082, China.
authors.forename: Chunxia
authors.initials: C
authors.lastname: Song
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry & Chemical Engineering, Key Laboratory for Bio-Nanotechnology and Molecular Engineering of Hunan Province, Hunan University, Changsha 410082, China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Wang
mesh_terms: D001483:Base Sequence; D002681:China; D003124:Colorimetry / Q000379:methods*; D004587:Electrophoresis, Agar Gel; D006046:Gold / Q000737:chemistry*; D007477:Ions; D008628:Mercury / Q000032:analysis*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization / Q000379:methods*; D045483:Rivers / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D007477:Ions; D014874:Water Pollutants, Chemical; D006046:Gold; D008628:Mercury
keywords: Gold nanoparticles; Hybridization chain reaction; Mercury ion