title: Label-free colorimetric detection of Hg²⁺ based on Hg²⁺-triggered exonuclease III-assisted target recycling and DNAzyme amplification.
abstract: This work reported a label-free colorimetric assay for sensitive detection of Hg(2+) based on Hg(2+)-triggered hairpin DNA probe (H-DNA) termini-binding and exonuclease Ш (Exo Ш)-assisted target recycling, as well as hemin/G-quadruplex (DNAzyme) signal amplification. The specific binding of free Hg(2+) with the thymine-thymine (T-T) mismatches termini of H-DNA could immediately trigger the Exo Ш digestion, and then set free G-quadruplex segments and Hg(2+). The Exo Ш impellent recycling of ultratrace Hg(2+) produced numerous G-quadruplexes. The corresponding DNAzymes catalyzed efficiently the H2O2-mediated oxidation of the ABTS(2-) to the colored product in the presence of hemin. Using the color change as the output signal, and the Exo Ш-aided Hg(2+) recycling and DNAzyme as the signal amplifier, the ultrasensitive assay system successfully achieved visual detection of Hg(2+) as low as 1.0 nM by the naked eye, and was suitable for field monitoring. The calibration curve was linear in the range of 50.0 pM to 20.0 nM for Hg(2+) (R=0.9962) with a detection limit of 10.0 pM. Moreover, this proposed strategy showed excellent selectivity, portability and low-cost, and was successfully applied to colorimetric detection of Hg(2+) in laboratory tap water and Jialing river water samples.
authors.affiliation: Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China; College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, Zigong 643000, PR China.
authors.forename: Wang
authors.initials: W
authors.lastname: Ren
authors.affiliation: Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China; College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, Zigong 643000, PR China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China.
authors.forename: Wei Tao
authors.initials: WT
authors.lastname: Huang
authors.affiliation: Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China. Electronic address: linb@swu.edu.cn.
authors.forename: Nian Bing
authors.initials: NB
authors.lastname: Li
authors.affiliation: Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China. Electronic address: luohq@swu.edu.cn.
authors.forename: Hong Qun
authors.initials: HQ
authors.lastname: Luo
mesh_terms: D015374:Biosensing Techniques; D003124:Colorimetry; D015342:DNA Probes / Q000737:chemistry; D005090:Exodeoxyribonucleases / Q000737:chemistry; D054856:G-Quadruplexes; D006861:Hydrogen Peroxide / Q000737:chemistry; D057230:Limit of Detection; D008628:Mercury / Q000737:chemistry / Q000302:isolation & purification*; D021141:Nucleic Acid Amplification Techniques
chemical_list: D015342:DNA Probes; D006861:Hydrogen Peroxide; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III; D008628:Mercury
keywords: Colorimetric assay; DNAzyme; Exonuclease Ш; Hg(2+); T–Hg(2+)–T