title: An ultra-sensitive colorimetric Hg(2+)-sensing assay based on DNAzyme-modified Au NP aggregation, MNPs and an endonuclease.
abstract: This paper reports the development of an ultra-sensitive colorimetric method for the detection of trace mercury ions involving DNAzymes, Au nanoparticle aggregation, magnetic nanoparticles and an endonuclease. DNAzyme-sensing elements are conjugated to the surface of Au nanoparticle-2, which can crosslink with the T-rich strands coated on Au nanoparticle-1 to form Au nanoparticle aggregation. Other T-rich stands are immobilized on the surface of MNPs. The specific hybridization of these two T-rich strands depends on the presence of Hg(2+), resulting in the formation of a T-Hg(2+)-T structure. Added endonuclease then digests the hybridized strands, and DNAzyme-modified Au NP aggregation is released, catalysing the conversion of the colourless ABTS into a blue-green product by H2O2-mediated oxidation. The increase in the adsorption spectrum of ABTS(+) at 421 nm is related to the concentration of Hg(2+). This assay was validated by detecting mercury ion concentrations in river water. The colorimetric responses were not significantly altered in the presence of 100-fold excesses of other metal ions such as Zn(2+), Pb(2+), Cd(2+), Mn(2+), Ca(2+) and Ni(2+). The inclusion of both Au NP aggregation and an endonuclease enables the assay to eliminate interference from the magnetic nanoparticles with colorimetric detection, decrease the background and improve the detection sensitivity. The calibration curve of the assay was linear over the range of Hg(2+) concentrations from 1 to 30 nM, and the detection limit was 0.8 nM, which is far lower than the 10 nM US EPA limit for drinking water.
authors.affiliation: Department of Chemistry, East China Normal University, Shanghai 200241, PR China.
authors.forename: Chao
authors.initials: C
authors.lastname: Li
authors.affiliation: Department of Chemistry, East China Normal University, Shanghai 200241, PR China.
authors.forename: Peiqing
authors.initials: P
authors.lastname: Dai
authors.affiliation: Department of Chemistry, East China Normal University, Shanghai 200241, PR China.
authors.forename: Xinyi
authors.initials: X
authors.lastname: Rao
authors.affiliation: Department of Chemistry, East China Normal University, Shanghai 200241, PR China.
authors.forename: Lin
authors.initials: L
authors.lastname: Shao
authors.affiliation: Department of Chemistry, East China Normal University, Shanghai 200241, PR China. Electronic address: gfcheng@chem.ecnu.edu.cn.
authors.forename: Guifang
authors.initials: G
authors.lastname: Cheng
authors.affiliation: Department of Chemistry, East China Normal University, Shanghai 200241, PR China.
authors.forename: Pingang
authors.initials: P
authors.lastname: He
authors.affiliation: Department of Chemistry, East China Normal University, Shanghai 200241, PR China.
authors.forename: Yuzhi
authors.initials: Y
authors.lastname: Fang
mesh_terms: D052160:Benzothiazoles / Q000737:chemistry; D002138:Calibration; D002413:Cations, Divalent; D003124:Colorimetry / Q000379:methods*; D021881:DNA, Catalytic / Q000737:chemistry*; D060766:Drinking Water / Q000737:chemistry; D004720:Endonucleases / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry; D005618:Fresh Water / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D006427:Hemin / Q000737:chemistry; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D057230:Limit of Detection; D008628:Mercury / Q000032:analysis*; D053768:Metal Nanoparticles / Q000737:chemistry*; D013451:Sulfonic Acids / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D052160:Benzothiazoles; D002413:Cations, Divalent; D021881:DNA, Catalytic; D060766:Drinking Water; D005456:Fluorescent Dyes; D013451:Sulfonic Acids; D014874:Water Pollutants, Chemical; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D006427:Hemin; D006046:Gold; D006861:Hydrogen Peroxide; D004720:Endonucleases; D008628:Mercury
keywords: Au nanoparticle aggregation; DNAzyme; Endonuclease; Magnetic nanoparticles; Mercury ions