title: Electrochemical DNAzyme sensor for lead based on amplification of DNA-Au bio-bar codes.
abstract: An electrochemical DNAzyme sensor for sensitive and selective detection of lead ion (Pb(2+)) has been developed, taking advantage of catalytic reactions of a DNAzyme upon its binding to Pb(2+) and the use of DNA-Au bio-bar codes to achieve signal enhancement. A specific DNAzyme for Pb(2+) is immobilized onto an Au electrode surface via a thiol-Au interaction. The DNAzyme hybridizes to a specially designed complementary substrate strand that has an overhang, which in turn hybridizes to the DNA-Au bio-bar code (short oligonucleotides attached to 13 nm gold nanoparticles). A redox mediator, Ru(NH3)6(3+), which can bind to the anionic phosphate of DNA through electrostatic interactions, serves as the electrochemical signal transducer. Upon binding of Pb(2+) to the DNAzyme, the DNAzyme catalyzes the hydrolytic cleavage of the substrate, resulting in the removal of the substrate strand along with the DNA bio-bar code and the bound Ru(NH3)6(3+) from the Au electrode surface. The release of Ru(NH3)6(3+) results in lower electrochemical signal of Ru(NH3)6(3+) confined on the electrode surface. Differential pulse voltammetry (DPV) signals of Ru(NH3)6(3+) provides quantitative measures of the concentrations of Pb(2+), with a linear calibration ranging from 5 nM to 0.1 microM. Because each nanoparticle carries a large number of DNA strands that bind to the signal transducer molecule Ru(NH3)6(3+), the use of DNA-Au bio-bar codes enhances the detection sensitivity by five times, enabling the detection of Pb(2+) at a very low level (1 nM). The DPV signal response of the DNAzyme sensor is negligible for other divalent metal ions, indicating that the sensor is highly selective for Pb(2+). Although this DNAzyme sensor is demonstrated for the detection of Pb(2+), it has the potential to serve as a general platform for design sensors for other small molecules and heavy metal ions.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
authors.forename: Li
authors.initials: L
authors.lastname: Shen
authors.forename: Zhong
authors.initials: Z
authors.lastname: Chen
authors.forename: Yihan
authors.initials: Y
authors.lastname: Li
authors.forename: Shali
authors.initials: S
authors.lastname: He
authors.forename: Shubao
authors.initials: S
authors.lastname: Xie
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Xu
authors.forename: Zhongwei
authors.initials: Z
authors.lastname: Liang
authors.forename: Xin
authors.initials: X
authors.lastname: Meng
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Zhu
authors.forename: Meixian
authors.initials: M
authors.lastname: Li
authors.forename: X Chris
authors.initials: XC
authors.lastname: Le
authors.forename: Yuanhua
authors.initials: Y
authors.lastname: Shao
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D004247:DNA / Q000737:chemistry; D021881:DNA, Catalytic / Q000737:chemistry*; D004563:Electrochemistry; D004800:Enzymes, Immobilized / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D007854:Lead / Q000032:analysis*; D036103:Nanotechnology / Q000379:methods*; D012680:Sensitivity and Specificity
chemical_list: D021881:DNA, Catalytic; D004800:Enzymes, Immobilized; D007854:Lead; D006046:Gold; D004247:DNA