1. Electrochemical DNAzyme sensor for lead based on amplification of DNA--Au bio-bar codes
- Author
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Shen, Li, Chen, Zhong, Li, Yihan, He, Shali, Xie, Shubao, Xu, Xiaodong, Liang, Zhongwei, Meng, Xin, Li, Qing, Zhu, Zhiwei, Li, Meixian, Le, X. Chris, and Shao, Yuanhua
- Subjects
Biosensors -- Research ,DNA -- Electric properties ,DNA -- Chemical properties ,Enzymes -- Electric properties ,Enzymes -- Chemical properties ,Bar codes -- Research ,Lead -- Properties ,Chemical detectors -- Research ,Chemistry - Abstract
An electrochemical DNAzyme sensor for sensitive and selective detection of lead ion ([Pb.sup.2+]) has been developed, taking advantage of catalytic reactions of a DNAzyme upon its binding to [Pb.sup.2+]and the use of DNA--Au bio-bar codes to achieve signal enhancement. A specific DNAzyme for [Pb.sup.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 biobar code (short oligonucleotides attached to 13 nm gold nanoparticles). A redox mediator, Ru[(N[H.sub.3]).sub.6.sup.3+], which can bind to the anionic phosphate of DNA through electrostatic interactions, serves as the electrochemical signal transducer. Upon binding of [Pb.sup.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[(N[H.sub.3]).sub.6.sup.3+] from the Au electrode surface. The release of Ru[(N[H.sub.3]).sub.6.sup.3+] results in lower electrochemical signal of Ru[(N[H.sub.3]).sub.6.sup.3+] confined on the electrode surface. Differential pulse voltammetry (DPV) signals of Ru[(N[H.sub.3]).sub.6.sup.3+] provides quantitative measures of the concentrations of [Pb.sup.2+], with a linear calibration ranging from 5 nM to 0.1 [micro]M. Because each nanoparticle carries a large number of DNA strands that bind to the signal transducer molecule Ru[(N[H.sub.3]).sub.6.sup.3+], the use of DNA-Au bio-bar codes enhances the detection sensitivity by five times, enabling the detection of [Pb.sup.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.sup.2+]. Although this DNAzyme sensor is demonstrated for the detection of [Pb.sup.2+], it has the potential to serve as a general platform for design sensors for other small molecules and heavy metal ions.
- Published
- 2008