title: Highly sensitive electrochemical sensor for mercury(II) ions by using a mercury-specific oligonucleotide probe and gold nanoparticle-based amplification.
abstract: We report a highly sensitive electrochemical sensor for the detection of Hg(2+) ions in aqueous solution by using a thymine (T)-rich, mercury-specific oligonucleotide (MSO) probe and gold nanoparticles (Au NPs)-based signal amplification. The MSO probe contains seven thymine bases at both ends and a "mute" spacer in the middle, which, in the presence of Hg(2+), forms a hairpin structure via the Hg(2+)-mediated coordination of T-Hg(2+)-T base pairs. The thiolated MSO probe is immobilized on Au electrodes to capture free Hg(2+) in aqueous media, and the MSO-bound Hg(2+) can be electrochemically reduced to Hg(+), which provides a readout signal for quantitative detection of Hg(2+). This direct immobilization strategy leads to a detection limit of 1 microM. In order to improve the sensitivity, MSO probe-modified Au NPs are employed to amplify the electrochemical signals. Au NPs are comodified with the MSO probe and a linking probe that is complementary to a capture DNA probe immobilized on gold electrodes. We demonstrated that this Au NPs-based sensing strategy brings about an amplification factor of more than 3 orders of magnitude, leading to a limit of detection of 0.5 nM (100 ppt), which satisfactorily meets the sensitivity requirement of U.S. Environmental Protection Agency (EPA). This Au NPs-based Hg(2+) sensor also exhibits excellent selectivity over a spectrum of interference metal ions. Considering the high sensitivity and selectivity of this sensor, as well as the cost-effective and portable features of electrochemical techniques, we expect this Au NPs amplified electrochemical sensor will be a promising candidate for field detection of environmentally toxic mercury.
authors.affiliation: Department of Biochemistry and National Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Zhu
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Su
authors.forename: Jiang
authors.initials: J
authors.lastname: Li
authors.forename: Di
authors.initials: D
authors.lastname: Li
authors.forename: Jiong
authors.initials: J
authors.lastname: Zhang
authors.forename: Shiping
authors.initials: S
authors.lastname: Song
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhao
authors.forename: Genxi
authors.initials: G
authors.lastname: Li
authors.forename: Chunhai
authors.initials: C
authors.lastname: Fan
mesh_terms: D055664:Electrochemical Techniques / Q000379:methods*; D006046:Gold / Q000737:chemistry*; D008628:Mercury / Q000032:analysis*; D053768:Metal Nanoparticles / Q000737:chemistry*; D015345:Oligonucleotide Probes / Q000737:chemistry*
chemical_list: D015345:Oligonucleotide Probes; D006046:Gold; D008628:Mercury