An exonuclease-assisted amplification electrochemical aptasensor for Hg2+ detection based on hybridization chain reactionby Ting Bao, Wei Wen, Xiuhua Zhang, Qinghua Xia, Shengfu Wang

Biosensors and Bioelectronics


Electrochemistry / Biophysics / Biotechnology / Biomedical Engineering


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le ch e ry o


Electrochemical aptasensor

Target recycling

Hybridization chain reaction troc ling uce air

DN ecy 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 doublepollut 2004; tamina in and stems et al., 2014) and atomic emission spectrum (AES) (Shoaee et al., 2012; these detection methods are rather limited by some deficiencies such scence (Li et al., ctrochemical apn, 2015). Among sitivity, low cost, mical aptasensor sed in sensitive

Enzyme catalytic reaction (Huang et al., 2014a, 2014b; Hu et al., clease/endonuclease)-assisted target recycling (Tang et al., 2012;

Contents lists available at ScienceDirect .e

Biosensors and

Biosensors and Bioelectronics 70 (2015) 318–323 expensive apparatus and complex sample pretreatment. Liu et al., 2013; Hu et al., 2014a, 2014b) and hybridization chain reaction (HCR) (Chen et al., 2012; Choi et al., 2014) have been used for signal amplification. Thereinto, exonuclease is a powerful catalytic tool and HCR is a simple and effective method for signal 0956-5663/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. Fax: þ86 27 88663043.

E-mail address: (S. Wang).Yuan et al., 2014) have been used for the detection of Hg2þ . However, 2014a, 2014b), graphene (Xu, et al., 2011; Wen et al., 2014), gold nanoparticle (Wu et al., 2013; Shu et al., 2013), nuclease (exonu-toxicity to human beings (Hoffmeyer et al., 2006). The maximum allowable concentration of Hg2þ in drinking water is 10 nM, defined by United States Environmental Protection Agency. Therefore, it is of great importance for sensitive and selective detection of Hg2þ . Traditional methods, such as fluorescence spectrometry (Maiti et al., 2014; Srivastava et al., 2014), inductively coupled plasma mass spectrometry (ICP-MS) (Long and Kelly, 2002; Chen, et al., 2013), high performance liquid chromatography (HPLC) (Gao and Ma, 2011; Zhou et al., 2015), photoelectrochemistry (Zhang and G et al., 2014a, 2014b, 2014c), electrochemilumine 2010; Wang et al., 2014a, 2014b, 2014c) and ele tasensor (Zhang and Yan, 2014; Chen and Che them, due to the advantage of simplicity and sen fast response and in vivo detection, electroche has received increasing attention and widely u detection of Hg2þ (Hocek and Fojta, 2011).(Sekowski et al., 1997; Nolan and Lippard, 2008; Zheng et al., 2003;

Harris et al., 2003). Even low concentration of Hg2þ has strong

T–Hg –T interaction, such as colorimetry (Wang et al., 2010.

Duan et al., 2014), fluorescence (Huang et al., 2014a, 2014b; Zhang uo, 2012; Wang1. Introduction

Mercuric ion (Hg2þ) is worldwide water and soil widely (Wang et al., highly toxic and bioaccumulative con damage to human organs such as bra severely affects central nervous systranded DNA. [Ru(NH3)6] 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 Hg2þ with a detection limit of 0.12 pM (S/N¼3). Furthermore, the proposed aptasensor had a promising potential for the application of Hg2þ detection in real aquatic sample analysis. & 2015 Elsevier B.V. All rights reserved. ant that widely exists in

Miller et al., 1996). It is nt which causes serious kidney. Furthermore, it and digestive systems

Thymine bases rich (T-rich) DNA can specifically capture Hg2þ through T–T mismatches to form T–Hg2þ–T base pairs. The

T–Hg2þ–T interaction induces T-rich DNA to convert into double helix structure and the binding force of T–Hg2þ–T is much higher than that of adenine-thymine (A–T) base pair (Ono and Togashi, 2004; Katz, 1962; Miyake et al., 2006). Lots of detection methods have been used for the detection of Hg2þ based on specific 2þHg2þ

Exonuclease III 3þAn exonuclease-assisted amplification e

Hg2þ detection based on hybridization

Ting Bao, Wei Wen, Xiuhua Zhang, Qinghua Xia, Sh

Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Minist

Organic Functional Molecules & College of Chemistry and Chemical Engineering, Hubei a r t i c l e i n f o

Article history:

Received 13 January 2015

Received in revised form 24 March 2015

Accepted 25 March 2015

Available online 26 March 2015

Keywords: a b s t r a c t

In this work, a novel elec clease-assisted target recyc

The presence of Hg2þ ind mediated T–Hg2þ–T base p digested the double-strand

Hg2þ participated analyte r journal homepage: wwwctrochemical aptasensor for ain reaction ngfu Wang n f Education Key Laboratory for the Synthesis and Application of versity, Wuhan 430062, PR China hemical aptasensor was developed for Hg2þ detection based on exonuand hybridization chain reaction (HCR) dual signal amplification strategy. d the T-rich DNA partly folded into duplex-like structure via the Hg2þ s, which triggered the activity of exonuclease III (Exo III). Exo III selectively

A containing multiple T–Hg2þ–T base pairs from its 3'-end, the released cle. With each digestion cycle, a digestion product named as help DNAwas

Bioelectronics tion cycle, an important digestion product named as help DNAwas [Ru(NH3)6] for 2 h. After each step, the electrode was rinsed with Tris–HCl (pH 7.4) to remove the nonspecific adsorption on

T. Bao et al. / Biosensors and Bioelectronics 70 (2015) 318–323 319obtained. The help DNA had partially complementary segments with capture probe and auxiliary DNA 1. The presence of help DNA led to alternatively hybridization of auxiliary DNA 1 and auxiliary

DNA 2 on the gold electrode (GE), the successful HCR process created adsorption sites for [Ru(NH3)6]3þ . Exo III-assisted target recycling and HCR dual amplification strategy amplified signal significantly which realized highly sensitive and selective detection of Hg2þ . 2. Experimental 2.1. Materials and reagents