An exonuclease-assisted amplification electrochemical aptasensor for Hg2+ detection based on hybridization chain reaction

• Published in: Biosensors & bioelectronics Vol. 70; pp. 318 - 323
• Main Authors: Bao, Ting, Wen, Wei, Zhang, Xiuhua, Xia, Qinghua, Wang, Shengfu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2015
• Subjects: Amplification; Biotechnology; Chain reactions; Deoxyribonucleic acid; Digestion; Electrochemical aptasensor; Exonuclease III; Hg2; Hybridization chain reaction; Recycling; Strands; Strategy; Target recycling; Hg2; Exonuclease III; Hybridization chain reaction; Electrochemical aptasensor; Target recycling
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2015.03.065

In this work, a novel electrochemical aptasensor was developed for Hg2+ detection based on exonuclease-assisted target recycling and hybridization chain reaction (HCR) dual signal amplification strategy. The presence of Hg2+ induced the T-rich DNA partly folded into duplex-like structure via the Hg2+ mediated T–Hg2+–T base pairs, which triggered the activity of exonuclease III (Exo III). Exo III selectively digested the double-strand DNA containing multiple T–Hg2+–T base pairs from its 3'-end, the released Hg2+ participated analyte recycle. With each digestion cycle, a digestion product named as help DNA was obtained, which acted as a linkage between the capture DNA and auxiliary DNA. The presence of help DNA and two auxiliary DNA collectively facilitated successful HCR process and formed long double-stranded DNA. [Ru(NH3)6]3+ was used as redox indicator, which electrostatically bound to the double strands and produced an electrochemical signal. Exo III-assisted target recycling and HCR dual amplification significantly improved the sensitivity for Hg2+ with a detection limit of 0.12pM (S/N=3). Furthermore, the proposed aptasensor had a promising potential for the application of Hg2+ detection in real aquatic sample analysis. [Display omitted] •Lable free: Ru(NH3)6Cl3 electrostatically adsorbed on dsDNA to produce signal.•Exonuclease-assisted target recycling amplified signal obviously.•Hybridization chain reaction was performed for signal amplification.•Dual amplification strategy significantly improved sensitivity of the aptasensor.