Ultrasensitive impedimetric mercury-thymine interaction and subsequent disintegration of multiple sandwich-structured DNA chains

• Published in: Mikrochimica acta (1966) 2018-12, Vol.185 (12)
• Main Authors: Gao, Feng, Zhang, Taoshun, Chu, Yaru, Wang, Qingxiang, Song, Juan, Qiu, Weiwei, Lin, Zhenyu
• Format: Article
• Language: English
• Subjects: DNA; Electric properties; Electrolytes; Pyrimidines; Sensors
• ISSN: 0026-3672
• DOI: 10.1007/s00604-018-3097-7

An impedimetric method is described for ultrasensitive analysis of mercury(II). It is based on thymine-Hg(II)-thymine interaction which causes the disintegration of multiple-sandwich structured DNA chains. DNA strands were selected that are partially complementary to the T-rich Hg(II)-specific oligonucleotides (MSO). They were immobilized on a gold electrode via Au-S interaction. Next, the MSO and the bridging strands (BS) that can connect adjacent MSOs were alternately attached through layer-by-layer hybridization. Thus, a multiple-sandwich structured interface in created that carries numerous MSOs. This leads to a change-transfer resistance (R.sub.ct) values of the electrode-electrolyte interface at faradic electrochemical impedance spectroscopy measurements in the presence of the hexacyanoferrate(II)/(III) redox probe at 0.2 V (vs. Ag/AgCl). If Hg(II) is added to the solution, the MSOs selectively interact with Hg(II) to produce T-Hg(II)-T structures. Hence, the multiple-sandwich hybridization chains become disintegrated, and this causes a decrease in resistivity. The effect can be used to quantify Hg(II) over an analytical range that extends over four orders of magnitude (1 fM to 10 pM), and it has a 0.16 fM limit of detection under optimal conditions.