title: Enzyme-triggered formation of enzyme-tyramine concatamers on nanogold-functionalized dendrimer for impedimetric detection of Hg(II) with sensitivity enhancement.
abstract: A new impedimetric sensing strategy based on enzyme-triggered formation of enzyme-tyramine concatamers on the nanogold-functionalized poly(amidoamine) (PAMAM) dendrimer was designed for sensitive detection of mercury(II) (Hg(2+)) ion, coupling with enzymatic biocatalytic precipitation towards 4-choloro-1-naphthol (4-CN) on thymine (T)-rich single-stranded DNA1-modified electrode. Initially, nanogold-decorated PAMAM dendrimer (AuNP-PAMAM) was synthesized by the in-situ reduction method, and then functionalized with horseradish peroxidase (HRP) and another T-rich oligomer (DNA2). Upon target Hg(2+) introduction, probe DNA2 on the AuNP-PAMAM bound to the DNA1 on the electrode owing to the T-Hg(2+)-T coordination chemistry between the two DNA strands. Accompanying the AuNP-PAMAM, the carried HRP could trigger the formation of HRP-tyramine concatamer via the classical tyramine signal amplification strategy in the presence of HRP-tyramine conjugates and hydrogen peroxide. The concatenated HRP molecules in the concatamer catalyzed the 4-CN oxidation to produce an insoluble precipitation on the electrode, thereby resulting in the local alteration in the conductivity. Under optimal conditions, two signal-generation tags including HRP-AuNP-DNA2 and HRP-AuNP-PAMAM-DNA2 with or without tyramine signal amplification strategy (i.e., four schemes) were used for impedimetric detection of target Hg(2+) on the basis of the same assay format. A low detection limit (LOD) of 0.4pM and a wide dynamic working range of 0.001-100nM Hg(2+) by using HRP-AuNP-PAMAM-DNA2 with tyramine signal amplification strategy were obtained in comparison with those of other strategies. The assay had a good repeatability and showed an intermediate precision of down to 9.6%. In addition, the methodology also exhibited high specificity and selectivity towards target Hg(2+) against other metal ions, and was applicable for monitoring Hg(2+) in the spiked drinking water samples.
authors: Key Laboratory of Analysis and Detection for Food Safety (MOE & Fujian Province), Institute of Nanomedicine and Nanobiosensing, Department of Chemistry, Fuzhou University, Fuzhou 350108, PR China.
authors: Zhenli
authors: Z
authors: Qiu
authors: Key Laboratory of Analysis and Detection for Food Safety (MOE & Fujian Province), Institute of Nanomedicine and Nanobiosensing, Department of Chemistry, Fuzhou University, Fuzhou 350108, PR China; Chongqing Key Laboratory of Environmental Materials & Remediation Technologies, Chongqing University of Arts and Sciences, Chongqing 402160, PR China.
authors: Dianyong
authors: D
authors: Tang
authors: Key Laboratory of Analysis and Detection for Food Safety (MOE & Fujian Province), Institute of Nanomedicine and Nanobiosensing, Department of Chemistry, Fuzhou University, Fuzhou 350108, PR China.
authors: Jian
authors: J
authors: Shu
authors: Key Laboratory of Analysis and Detection for Food Safety (MOE & Fujian Province), Institute of Nanomedicine and Nanobiosensing, Department of Chemistry, Fuzhou University, Fuzhou 350108, PR China.
authors: Guonan
authors: G
authors: Chen
authors: Chongqing Key Laboratory of Environmental Materials & Remediation Technologies, Chongqing University of Arts and Sciences, Chongqing 402160, PR China. Electronic address: dianping.tang@fzu.edu.cn.
authors: Dianping
authors: D
authors: Tang
mesh_terms: D015374:Biosensing Techniques; D004247:DNA / Q000737:chemistry; D050091:Dendrimers / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry; D057230:Limit of Detection; D008628:Mercury / Q000737:chemistry / Q000302:isolation & purification*; D053768:Metal Nanoparticles / Q000737:chemistry*; D014439:Tyramine / Q000737:chemistry*
chemical_list: D050091:Dendrimers; C104700:PAMAM Starburst; D006046:Gold; D004247:DNA; D006735:Horseradish Peroxidase; D008628:Mercury; D014439:Tyramine
keywords: Enzymatic catalytic precipitation; Enzyme-tyramine concatamer; Impedimetric sensor; Mercury ion; Nanogold–decorated poly(amidoamine) dendrimer; Tyramine signal amplification