A novel acetylcholinesterase biosensor based on ionic liquids-AuNPs-porous carbon composite matrix for detection of organophosphate pesticidesby Min Wei, Jingjing Wang

Sensors and Actuators B: Chemical

Text

Accepted Manuscript

Title: A novel acetylcholinesterase biosensor based on ionic liquids-AuNPs-porous carbon composite matrix for detection of organophosphate pesticides

Author: Min Wei Jingjing Wang

PII: S0925-4005(15)00139-2

DOI: http://dx.doi.org/doi:10.1016/j.snb.2015.01.112

Reference: SNB 18039

To appear in: Sensors and Actuators B

Received date: 31-10-2014

Revised date: 27-1-2015

Accepted date: 28-1-2015

Please cite this article as: M. Wei, J. Wang, A novel acetylcholinesterase biosensor based on ionic liquids-AuNPs-porous carbon composite matrix for detection of organophosphate pesticides, Sensors and Actuators B: Chemical (2015), http://dx.doi.org/10.1016/j.snb.2015.01.112

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Highlights ► The [BSmim]HSO4-AuNPs-porous carbon was firstly prepared to develop AChE biosensor. ► The lower Rct of the [BSmim]HSO4-AuNPs-porous carbon/BDD than that of the bare BDD. ► The AChE/[BSmim]HSO4-AuNPs-porous carbon/BDD biosensor showed higher sensitivity for thiocholine oxidation. ►The AChE/[BSmim]HSO4-AuNPs-porous carbon/BDD biosensor showed lower detection limit toward dichlorvos detection. ► The AChE/[BSmim]HSO4-AuNPs-porous carbon/BDD biosensor showed good repeatability and favorable stability.

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A novel acetylcholinesterase biosensor based on ionic liquids-AuNPs-porous carbon composite matrix for detection of organophosphate pesticides

Min Wei*, Jingjing Wang

College of Food Science and Technology, Henan University of Technology,

Zhengzhou 450001, PR China * Corresponding author. Tel.: +86 37167758022. E-mail address: wei_min80@163.com

Abstract

A novel acetylcholinesterase (AChE) biosensor, based on honeycomb-like hierarchically ion liquids ([BSmim]HSO4)-AuNPs-porous carbon composite modified boron-doped diamond (BDD) electrode, was developed for the detection of organophosphate pesticides. The surface morphology of the prepared [BSmim]HSO4-AuNPs-porous carbon composite was characterized by scanning electron microscopy and transmission electron microscopy. The [BSmim]HSO4-AuNPs-porous carbon modified BDD electrode was confirmed by cyclic voltammogram and electrochemical impedance spectroscopy. For the oxidation of thiocholine, hydrolysis product of acetylthiocholine, the peak current at

AChE/[BSmim]HSO4-AuNPs-porous carbon/BDD electrode is more than 4.5 times that at AChE/BDD electrode. The inhibition of dichlorvos is linearly proportional to its concentration in the range of 10−10 - 10−6 g/L (4.5×10−13 - 4.5×10−9 M), with the

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Ac ce pte d M an us cri pt 3 detection limit of 6.61×10−11 g/L (2.99×10−13 M ) (calculated for 10 % inhibition).

The proposed biosensor provided an efficient and promising platform for the immobilization of AChE and exhibited higher sensitivity and acceptable stability for the detection of organophosphate pesticides.

Keywords: [BSmim]HSO4-AuNPs-porous carbon composite, AChE biosensor, BDD electrode, dichlorvos 1. Introduction

Organophosphate pesticides (OPs) play an important role in increasing agricultural productivity due to their high insecticidal activity [1-3]. Unfortunately, owing to their high acute toxicity and bioaccumulation effect, the residue in the environment can cause long-term damage to human health [4]. Therefore, the detection of OPs has become increasingly necessary. Among the different techniques, biosensors based on acetylcholinesterase (AChE) have attracted much more attention in recent years due to their advantages in terms of rapid response, simple operation, decreasing analysis time, low cost and field deployability [5-7]. The detection mechanism for OPs is as follows: AChE can catalyze hydrolysis of acetylthiocholine (ATCl), and the enzymatic reaction product is electro-active thiocholine, which can produce an irreversible oxidation peak. OPs can inhibit the activity of AChE, and then decrease the oxidation of thiocholine. The oxidation peak current of thiocholine is inversely proportional to the concentration of OPs. By monitoring the oxidation peak current of thiocholine before and after inhibition, the OPs concentration can be determined [8]. For the fabrication of AChE biosensor, effective immobilization of

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AChE onto the electrode surface still faces some challenges. For example, the immobilization of AChE needs reinforce adsorption between the enzyme and the substrate material, retain enzyme stability without the loss of bioactivity, and facilitate the electron transfer between the biosensor and the electrode surface [9]. In addition, the detection limit of AChE biosensor cannot reach the detection level of those conventional analysis methods such as GC, HPLC etc. [5].

Recently, with the rapid development of nanotechnology, various novel nanomaterials have been applied in different strategies including adsorption, entrapment and covalent coupling for the effective fabrication of AChE biosensor [10-16] and other biosensors [17, 18]. Moreover, the utilization of different immobilization approaches has shown synergic effect to improve the biosensor performance [9, 19, 20]. Herein, our research purpose is to develop a highly sensitive and stable AChE biosensor by synergic effect to improve AChE adsorption, retain enzyme activity, and enhance the sensitivity of response for the detection of OPs.

In recent years, macro-/meso-/porous carbon materials have attracted enormous attention due to their remarkable properties including open pore structure, high specific surface area, large pore volume, efficient mass transportation, high conductivity and good chemical stability [21]. These advantages lead to their wide variety of applications as catalyst supports [22], electrode materials for batteries [23], fuel cells [24] and supercapacitors [25], and substrate materials for sensors [26].