Int J Pharm Pharm Sci, Vol 7, Issue 2, 17-24Review Article



1Department of Bio & Nano Technology, Guru Jambheshwar University of Science & Technology, Hisar 125001, India, 2Centre for Biotechnology, Maharshi Dayanand University, Rohtak 124001, India.

Received: 01 Nov 2014 Revised and Accepted: 25 Dec 2014


Due to intense pressure on agriculture for supporting exponentially growing population pesticides are used on an alarming scale. As these pesticides contain Organophosphorus (OP) compounds which are highly toxic and interfere with functioning of enzyme Acetylcholinestrase (AChE) and finally affecting Central Nervous System (CNS). So, there is an urgent need to monitor OP compounds concentration regularly in the marketed food products and even in the environment (water, soil). Here we focus on the different nanomaterials used for the fabrication of the AChE biosensors for detection of OP compounds which is based on inhibition of AChE. The merits and demerits of the different nanomaterials which are being used as supports are also discussed. The mode of detection, detection limit, linearity range, time of incubation, storage stability of the biosensors is also reviewed. Nanomaterial as an important class of supports used for the AChE biosensors due to their valuable properties. Among all the nanomaterials used Gold nanoparticles (AuNPs) have gained an advantage as they are explored with time.

Keywords: Pesticides, Acetylcholinesterase, Acetylcholinestrase Biosensor, Immobilization support, Detection Limit.


Pesticides are a key part of agriculture which is in regular use worldwide for enhancing productivity to meet the demands of remarkably growing population. These have insecticidal property due to which they are excessive use [1, 2]. But their regular use is harmful for human health and the surroundings due to presence of organophosphorus (OP) compounds. These OP compounds accumulate in fruits, vegetables, grains and contaminate water [3, 4]. Their concentration is increasing in an environment with the high rate. Organophosphorus (OP) constitute an important classes of toxic compounds that lead to irritation in eyes, abdominal pain, convulsions, respiratory system failure and other neurological disorders [5-10]. As per Environmental Protection Agency (EPA) organophosphates are highly toxic to wildlife and humans [1].

The OP pesticides are irreversible inhibitors of enzyme AChE by attachment of hydroxyl group on active site with serine of enzyme acetylcholinestrase (AChE, EC which is a key enzyme for proper functioning of central nervous system (CNS) of the humans. This inhibition of AChE enzyme, results in accumulation of acetylcholine (ACh) neurotransmitter in body which further interferes with response of muscles resulting in respiratory related problems, myocardial malfunctioning and finally death [11,12]. The toxicology of these OP pesticides depends on their chemical structure [12, 13]. Regulatory aspects and the guideline levels are there for permissible residues in drinking water [14]. There is a need to develop new protocols for detection of OP compounds in various samples which are selective and sensitive [15].

Analytical methods are there for monitoring the concentration of these toxic compounds in fruits, vegetables etc. The analytical methods used for this purpose include capillary electrophoresis [16], colorimetry [17], gas chromatography (GC) [18], mass spectrometry (MS) [19], thin layer chromatography [20, 21] and high performance liquid chromatography (HPLC) [22]. Immuno-assays are also effective as they are highly selectivity, sensitivity and reproducibility, but suffer from the drawback as they require corresponding antibodies [23, 24]. Sample preparation is also required which is a complex process, time consuming, requires expensive equipments which is not present in all laboratories. Biosensor overcomes the problems associated with analytical methods. Biosensors are fast, sensitive, and reliable for detection of traces of OP compounds.

In this present article, the nanomaterials based biosensors which work on the inhibition principle of enzyme AChE are reviewed in order to monitor the presence of these toxic compounds in different samples.

Nano structured materials for the biosensing

Nanostructured materials are basically known for their fundamental property of being quantum sized and having the large surface area. These properties of nanomaterials make them more advantageous than that of other bulky materials which are being used as a support for immobilization of enzymes. The nanostructures are characterized as Zero Dimensional (0D) which includes nanoparticles and quantum dots, 1 Dimensional (1D) such as carbon nanotubes (SWCNTs/MWCNTs) and nanowires & finally 2 Dimensional (2D) having graphene sheets and metallic platelets in this orientation category [25] (fig. 1). These nanostructures are explored more and more because of their characteristics to improve biosensors with respect to their electrical conductivity, surface area, detection limit, easy to synthesize in laboratory, controlling & maintain their size etc.

Fig. 1: Characterization of Nanomaterials

Nanostructured materials for OP compound sensing

The nanomaterial biosensors are based on the catalysis by organophosphorus hydrolase (OPH) on OP compounds (fig. 2) and on the other hand inhibition effects of OPs on activity of AChE. When inhibitor (OP) is not present the substrate acetylthiocholine is converted into thiocholine and acetic acid (fig. 3). The catalytic activity of AChE for the hydrolysis reaction of acetylcholine to thiocholine is drastically inhibited by trace amounts of OPs present in the environment (fig. 4). Nanomaterial-based AChE electrochemical sensors have been extensively applied for AChE activity assay and OPs screening by using different supports and transducer material [26], surface plasmon resonance (SPR) [27], absorption [28] and fluorescence spectroscopy [29,30]. By using nanomaterials such as carbon nanotubes, Au nanoparticles (AuNPs), ZrO2 nanoparticles, quantum dots (QDs) as immobilization support matrices, there is a dramatic increase in the electrocatalytic activity with very high sensitivity, selectivity and accuracy for detection of OP compounds [31]. The localized SPR (LSPR) property of AuNPs covalently coupled with AChE has been exploited for OPs determination [27]. Layer-by-Layer (LBL) method has been used for integrating CdTe QDs with AChE which resulted in a highly sensitive fluorescence biosensor for detection of OPs in vegetables and fruits based on enzyme inhibition mechanism [29]. Large variety of OP compounds has been hydrolysed by OPH which produce less toxic products such as p-nitrophenol and diethyl phosphate. Several types of OPH-based nano-biosensors have been introduced recently, including fluorescence [32-35] and amperometric biosensors [36].

Fig. 2: Basic reaction involved in OPH biosensors

Fig. 3: Reaction in absence of inhibitor (OP Compound)

Fig. 4: Reaction in presence of inhibitor

Nanomaterial based OPH biosensor

The OPH biosensors are used for the detection of paraoxon, methyl parathion, parathion, coumaphos etc. OPH hydrolyse the OP compounds resulting in change of pH of the solution which can be measured. Basic scheme involved showing in fig. 2. This change in pH is due to the breaking of the bonds such as P-CN, P-O, P-S [37] etc. Nanoparticles are proving to be a boom in the field of biosensing due to their invaluable properties such as large surface area, are highly conductive, good catalytic property etc. the rate of electron transfer is enhanced to a great extent and also the nanomaterial possesses high affinity towards the enzyme OPH. They can be synthesized in the laboratory and even their particle size can be adjusted according to the need. OPH based biosensors are developed using SWCNTs [38-39], MWCNTs [40,41], AuNPs [42].

Nanoparticles based Ach E biosensors

Metallic nanoparticles are unique with respect to their electronic and electrocatalytic properties which depend upon the size and morphological structure [43, 44]. These metallic nanoparticles possess high mechanical strength; they are biocompatible, for conducting oxygen ion and retaining biological activity [45]. Nanoparticle (NP)-based Ach E biosensors have many advantages both in terms of stability and in terms of enhancing the catalytic reduction of redox species. A variety of nanoparticles including silver, platinum, palladium, cooper, cobalt and others have been explored for fabrication of the working electrode in biosensor development [46-50]. But, gold nanoparticles (AuNPs) are explored and exploited to a greater extent as a fabrication material for biosensors development because of its valuable capability to enhance electronic signal when biological components are in contact with working electrode fabricated with nanoparticles Organic stabilizers are also in use to synthesize nanomaterials of different morphologies depending upon the need.

Dendrimers are tridimensional organic macromolecules with highly defined functional structure [51]. These dendrimeric structures stabilize and maintain the integrity of metallic nanoparticles that was reported by Crooks and co-workers [52]. As an example, polyamidoamine dendrimers (PAMAM) were used as template for nanoparticles synthesis or for nanoparticles nucleation in nano reactors. Functional groups are also present on dendrimers is also an important subject of studies in the field of nanostructured thin films fabrication and also, in development of hybrids with metallic nanoparticles.

One such approach was reported recently in which hybrids of PAMAM-AuNPs in multilayer thin films based on LBL technique were used to enhance the charge transfer in modified working electrodes leading to electroactive nanostructured membranes (ENM) concept [53]. Different supports used for immobilization of enzyme (Table 1): PAN/gold nanoparticles (AuNPs) onto Pt electrode [54], GnPs/Chitosan/GCE [55], AuNPs–CaCO3 bioconjugate/Au electrode,

Table 1: Nanoparticles based supports used for Ach E immobilization.

Mode of detection Transducer Enzyme immobilization method Minimum detection limit linearity Substrate/enzyme inhibitor

Time of incubation


Storage stability


Amperometric PAN/AuNPs/Pt electrode Covalent 0.026×10-5 µM 3.6×10-7-3.6×10-4 µM Paraoxon 20 30 54
Voltammetric GnPs/Chitosan/GCE Covalent bonding 1.58×10−10 M NR Cholropyrifos 10 10 55
Amperometric AuNPs/PB/GCE Adsorption 3.5×10-9 µM



4.48× 10-2 µM

Monocrotophos 10 30 56
Amperometric ZrO2/CHIT composite film/GCE Adsorption


5.0×10-3 and 1.7 µM


0.01-0.59 and

8.6-520 µM

Phoxin, Malathion and imethoate 15 30 57
Amperometric Gold-platinum bimetallic NPs/GCE Crosslinking with glutaraldehyde


40×10-3 and 40 µM



and 40-60 µM

Paraoxon ethyl, sarin and aldicarb 25 NR 58
Amperometric AuNPs/GCE Adsorption 7.0×10-3 µM 28×10-3-170×10-3 µM Methamidophos 10 7 59
Amperometric PB and CHIT/GCE Glutaraldehyde crosslinking





0.3310-4 µM



0.116×10-3-0.0194 and 0.167×10-3-0.0335 µM

Paraoxon and chlorpyrifos-ethyl oxon 10 NR 60
Fourier transform continuous cylclic voltammetry MWCNTs/AuNPs-CHIT/GCE Adsorption 0.01 µM 0.1-10 µM Monocrotophos NR 50 61
Amperometric CdS-decorated garphene nanocomposite Adsorption 3.4×10-3 µM 9.9×10-3-9.93 µM Carbaryl 2 20 62
Amperometric CHIT-GNPs/Au electrode Chemisorption/esorption 0.1×10-3 µM 0.3×10-3-60.5×10-3 µM Malathion 15 NR 63
Amperometric AuNPs/Au electrode Adsorption 33×10-3 µM 10×10-3-135×10-3 µM Carbofuran 20 7 64
Amperometric/Flow injection analysis system PbO2/TiO2/Ti Adsorption 0.1×10-3 µM 0.01-20 µM Trichlorfon 10 5 65
Amperometric PB-CHIT/GCE Covalent 3.0×10-3 µM 0.01-0.4 and 1.0-5.0 µM Carbaryl 10 30 66
Amperometric Er-GRO/Nafion Adsorption 2.0 ng mL−1 5.0-100 ng mL−1 and 1.0-20 ng mL−1 Dicholrvos 10 28 67
Amperometric Au–PtNPs/3-APTES/GC electrode. Cross linking 150–200 nM, 40–50 nM, and 40–60µM for Paraoxon ethyl, sarin, and aldicarb NR Paraoxon ethyl, sarin, and aldicarb 10 NR 68
Amperometric PAN-AuNPs Covalent immobilisation 7.39×10−11 g L−1 10−10-10−7 g L−1 paraoxon NR 20 69
Voltammetric CdTe-GNPs film. Covalent binding 0.3 ngmL−1 1-1000 ngmL−1 and 2-15ngmL−1 monocrotophos 8 30 70
Amperometric SiSG-AuNPs Surface adsorption 0.6 ng/ml 0.001-1 µg/ml and 2-15 µg/ml monocrotophos 10 30 71

AuNPs/PB/GCE [56], ZrO2/CHIT composite film/GCE [57], gold–platinum bimetallic NPs/GCE [58], AuNPs/GCE [59], PB and CHIT/GCE [60], calcium carbonate–CHIT composite film/GCE [61], CdS-decorated graphene nanocomposite [62], CHIT–GNPs/Au electrode [63], AuNPs/gold electrode [64], PbO2/TiO2/Ti [65], PB–CHIT/GCE [66], Er-GRO/Nafion [67], Au-PtNPs/3-APTEs/GCE [68],, PAN-AuNPs [69], CdTe AuNPs Film [70], SiSG-AuNPs [71].

Quantum dot as immobilization support for Ach E

Quantum dots are the luminescent fluorophores. These are semiconductor particles having dimensions confined to the nanometre scale [72]. They are very important candidate for the fabrication of variety of biosensors as they possess size dependent properties and are dimensionally similar to biological molecules [73-74]. Sensitive sensors have been developed as QDs can be coupled with the variety of biological molecules. They suffer from demerits such as large size (10 to 30 nm), blinking behaviour.

The supports which are used for the immobilization of the enzymes are (Table 2): Supports used for immobilization of enzyme: CdTe QDs/AuNPs/chitosan (CHIT)/GCE [75], CdTe QDs/Au electrode [76], and poly-(allylamine hydrochloride)/CdTe QDs/glass [77], Mn: ZnSe d dots [78], CdTE QDs/Au electrode [79].

Table 2: Quantum dots used as support for Ach E immobilization

Mode of detection Transducer Enzyme immobilization method Minimum detection limit linearity Substrate/enzyme inhibitor Time of incubation (min) Storage stability(days) Reference
Electrochemical AuNPs-SiSG/GCE Hydrogen bonds 0.44 µM NR Monocrotophos 10 30 75
Amperometric CdTe QDs/AuNPs/CHIT/GCE covalent 1.34 µM 4.4×10-3-4.48 and 8.96-67.20 µM Monocrotophos 8 30 76
Optical Poly(allylamine hydrochloride)CdTe QDs/glass Electrostatic interaction

1.05×10-5 an

d4.47×10-6 µM

1.0×10-6-1.0 and 1.0-0.1 µM



15 35 77
Fluorescence quenching Mn: ZnSe d-dots NR 1.31_10_11 mol/ 4. to.84x10_11 to 4.84x10_6 mol/L paraoxon 10 NR 78
Amperometric CdTE QDs/Au electrode covalent 2.98×10-3 µM 4.96×10-3-2.48 µM Carbyl 10 30 79

CNTs and Nanowires based Ach E biosensors

Carbon nanotubes (CNTs) are the one dimensional (1D) nanomaterials which are known for their wide application in chemical and biological sensing of different analytes in variety of samples. CNTs have hollow graphitic structure of cylindrical shape having fast electron transfer rate and blessed with good electrocatalytic effect [80-82]. These magnetic nanomaterials used in the conjugation with biological material are the basis of electrochemical biosensing. The CNTs possess unique properties related to surface area, conformation stability, high bioactivity and substrate biocatalyst interaction [83, 84]. The carbon-based electrodes such as carbon pellet [85], carbon fibers [86], carbon felt [87], carbon black slurry [88], glassy carbon [89], graphite particles and graphite [90] have been replaced by CNTs.

Different supports used are (Table.3): Multiwalled carbon nanotubes (MWCNTs)/PAN membrane onto Pt electrode [91], polyamidoamine (PAMAM)–gold/carbon nanotubes (CNTs)/GCE [92], AuNP–polypyrrole (PPy) nanowire composite film modified GCE [93], PPy and PANI copolymer doped with MWCNTs/GCE [94], SWCNT–CoPC/SPE [95], MWCNTs–gold nanocomposites/GCE [96], AuNPs–MWCNTs/GCE [97], MWCNTs–CHIT composite/GCE [98], SWCNT modified FGE [99], CNT web modified GCE [100]. Nanowire is the well-ordered polymer chain structure having small cross dimensions and with the high surface to volume ratio. PPy nanowires are one of the nanowires which have been used for the fabrication of biosensors [101]. The PPy nanowires are conducting polymers which are organic in nature. These conducting polymers act as enzyme immobilization matrix in which enzyme can be entrapped or covalently attached. As these are conducting in nature they can allow the transfer of charge through them, can be easily prepared, and are stable also [102-104]. The nanowires can be used in conjugation with the nanoparticles for the fabrication of working electrode. AuNPs and PPy were used together as an immobilization matrix for AChE in detection of OP compounds. AuNPs was electrodeposited onto the PPy nanowires for the stable immobilization of AChE enzyme leading to the development of OP biosensor for detection of methyl parathion105. Due to the combination of nanoparticles and nanowires the porosity of the matrix is increased as a result of which large effective surface area for enzyme immobilization is available, good conductivity and high catalytic activity can be achieved.

Table 3: CNTS and Nanowires as support for AChE immobilization

Mode of detection Transducer Enzyme immobilization method Minimum detection limit linearity Substrate/enzyme inhibitor

Time of incubation


Storage stability


Amperometric MWCNTs/PAN membrane/Pt electrode Affinity bonds using concanavalin A 5.0×10-9 µM 3.6×10-8-3.6×10-5 µM Paraoxon 20 120 91
Amperometric PAMAM-gold/CNTs/GCE



4.0×10-3 µM 4.8×10-3-9.0×10-2 µM Carbofuran 9 21 92
Electrochemical AuNPs-PPy nanowires composite film modified GCE Entrapment 7.5×10-3 µM 0.018-0.45 and 1.89-17.0 µM Methyl parathion 12 30 93
Amperometric PPY and PANI copolymer doped with MWCNTs/GCE Adsorption 3.02×10-3 µM 0.030-1.51 and 3.027-75.67 µM Malathion 15 30 94
Amperometric Single-walled CNTs-CoPC/SPE Covalent 0.01 and 6.3×10-3 µM 0.018-0.181 and 6.36×10-3-0.159 µM Paraoxon and malaoxon 15 3 95
Amperometric MWCNTs-Au nanocomposite/GCE Hydrophilic surfacefor biomolecule adhesion 1.81×10-3 µM 3.0×10-3-3.027 µM Malathion 8 30 96
AuNPs-MWCNTs/GCE Adsorption 1.0×10-3 µM


7.0×10-3 µM

NR 30 NR 97
Amperometric MWCNTs-CHIT composite/GCE Covalent NR NR Carbaryl, Malathion, dimethoate and monocrotophos 8 30 98
Potentiometric SWCNT modified FGE Cross linking 25–35 nM and 15–20nM for Sarin and DFP respectively 20–60 nM and 20–80 nM for sarin and DFP respectively Sarin and DFP 5 30 99
Amperometric CNT-Web modified glassy carbon electrode Adsorption 1nM 20–1000 nM methyl parathion 20 NR 100

Graphene sheets and metallic platelets based Ach E biosensors

Graphene nanosheet was experimentally synthesized in 2004 in which the sp2 hybridized carbon atoms were packed like honeycomb two dimensional sheets [106-108]. Graphene is a two dimensional carbon based nanomaterial with valuable physical, chemical and excellent electrocatalytic properties [109,110]. Nanocomposites, nanoelectronics, electrochemical resonators and ultra sensitive sensors can be synthesized using graphene nanosheet [111-114]. The high surface area of graphene sheet is favourable for immobilization of enzyme and have small band gap which is responsible for conducting the electrons with high efficiency [110], graphene based hybrid nanocomposites are also prepared; as these nanocomposites materials are functionalized they may enhance the sensing performance of the biosensor [115]. The planer geometry of graphene nanosheet makes it more advantageous over the carbon nanotubes [116]. With this, the graphene nanosheet is in more close contact with the surrounding medium rather than that of tube shaped carbon nanotubes. Graphene based chemical sensors have low electronic noise from the thermal effect which is due to high temperature of the solution or the reaction mixture provides higher sensitivity [117]. Interlocking is also shown by graphene nanosheet with the adsorbed target or the analyte [118].

The exfoliated graphite nanoplatelets (xGnPs) have emerged as a substitute of carbon nanotubes [119]. These xGnPs possess structural, electrical, mechanical and thermal properties imparted by graphite. Both graphite and carbon nanotubes are well known for their property of surface adsorption [120]. Adsorption is more in case of metallic platelets as they are arranged in sheets due to which it has the high surface area as compared to that of the hollow structure of carbon nanotubes. Presence of xGnPs on the surface of working electrode enhances the electrical conductivity and on the other hand reduces electrode fouling [121]. Some of the supports used (Table 4) are graphite–epoxy composite/SPE [122], TCNQ modified graphite [123], TiO2-decorated grapheme/GCE [124], graphite, nanoplatelet–CHIT composite/GCE [125], CdS-decorated grapheme nano composite [126].

Table 4: Graphene and Nanoplatelets used as support foe Ach E immobilization

Mode of detection Transducer Enzyme immobilization method Minimum detection limit linearity Substrate/enzyme inhibitor

Time of incubation


Storage stability


Amperometric Graphite-epoxy composite/SPE Crosslinking 1.0×10-4 and 1.0×10-5 µM NR Paraoxon and carbofuran 15 5 122
Amperometric TCNQ modified-Graphite Screen Printing 1 ppb 0-5 x 10-3M Methamidophos 10 NR 123
Amperometric TiO2-decorated grapheme/GCE Adsorption 1.4×10-3 µM 4.9-74.5 and 74.5-9.9×103 µM Carbyl 3 20 124
Voltammetric Graphitenanoplatelet-CHIT composite film/GCE Covalent 1.58×10-4 µM 1×10-4-1.0 µM Chloropyrifos 10 10 125
Amperometric CdS-decorated garphene nanocomposite Adsorption 3.4×10-3 µM 9.9×10-3-9.93 µM Carbaryl 2 20 126

Table 5: Merits &Demerits of different supports

AChE Immobilization Supports Examples Merits Demerits
Membrane Based Nylon and cellulose nitrate, hybrid mesoporous silica, poly-(acrylonitrile-methylmethacrylate-sodium vinylsulfonate) (PAN), cellophane, polyacrylamide, Biodyne and Immunodyne, Hybond N+. Artificial membranes have high selectivity for bio-elements; possess higher degree of flexibility, mechanical durability, wider pH range for use, and higher specific activity. Membrane fouling. The pores of semipermeable membrane are blocked leading to hindrance in the passage of solute.
Non Conducting Polymer Matrices PVA–SbQ polymer onto screen-printed electrode (SPE), PVA–SbQ membrane/Pt electrode, and polyamidoamine (PAMAM)–gold/carbon nanotubes (CNTs)/GCE, MSF/PVA/GCE, Nylon net, PVA/AWP, CoPC modified PVA-AWP electrode. Easily prepared in the lab. Variety of the functional groups can be generated on supports by chemical treatment. Provides microenvironment to enzyme which increases storage stability. Acts as barrier between electron and transducer which influence sensitivity of electrode Finally working of biosensor affected.
Conducting Polymer Matrices Mercaptobenzothiazole/polyaniline(PANI)/Au electrode, PANI/CNTs wrapped with single stranded DNA (ssDNA)/Au electrode, Silk fibronin matrix, CS/ALB/GCE, PB/GCE, GnPs/Chitosan/GCE. Thickness of film, functionalization, conductivity etc. can be adjusted. Can also be used for the enzyme entrapment during electropolymerization and used in the uniform covering of the help of the polymer film High cost, difficult in processing, lack of mechanical stability after doping, difficult to fabricate, short life span.
Sol Gel Sol–gel crystals derived from tetramethyl orthosilicate (TMOS), sol–gel film on a glass cap, TMOS sol–gel film, chromoionophore (ETH5294) doped sol–gel film, Al2O3 sol–gel matrix, sol–gel matrix on 7,7,8,8-tetracyanoquinodimethane (TCNQ), AuNPs–SiSG, alumina sol–gel, bromothymol blue doped sol–gel film, zinc oxide sol–gel, and silica sol–gel film, Sol-gel/Carbon electrode. The first and the foremost important property of the sol gel support is that the pore size can be adjusted according to the need. They are also chemically inert, do not show swelling in the aqueous medium, have photo-chemical and thermal stability. The antibodies and the enzymes can specially be immobilized. Do not allow the leakage of the enzyme in the medium. Some of the accountable demerits includes denaturation of biomolecules take place at high acidic condition and/or high alcohol concentration, the protocols used for the sol gel film formation are not amenable for coating the curved surfaces of substrates such as optical fibers, sufficient signals require high level of biomolecules in sol gel thin films but it is not possible in case of proteins that are insoluble or aggregate in the alkoxy silane solution.
Screen Printing TMOS sol–gel film/SPE, Al2O3 sol–gel matrix SPE, SPE (TCNQ mediator [7,7,8,8-tetracyanoquinonedimethane] in the graphite electrode), Prussian blue (PB) modified SPE, cobalt(II) phthalocyanine (CoPC)/SPE, o-phenylenediamine onto carbon/CoPC SPE, graphite–epoxy composite/SPE, SWCNT–CoPC/SPE, PET chip SPE. Screen printing involves immobilization of the biological molecules or the biological receptor in their active form. Screen printing is instable, high cross-sensitivity towards anion, limited life span.
Quantum Dots CdTe QDs/AuNPs/chitosan (CHIT)/GCE, CdTe QDs/Au electrode, and poly(allylamine hydrochloride)/CdTe QDs/glass, Mn: ZnSe d dots, CdTE QDs/Au electrode. Highly luminescent photostable fluorophore, semiconductor particles of nanometre scale, having great size dependent properties and are dimensionally similar with the biological molecules. They suffer from demerits such as large size (10 to 30 nm), blinking behaviour if no emission interrupt longer periods of fluorescence.


Nanomaterials based biosensors have found wide range of applications for the detection of OP compounds in water, soil, food samples etc. Different fabrication strategies have been applied for the development of nano based biosensors. They provide real-time qualitative and quantative information related to the composition of samples. Sample preparation for these nano fabricated sensors is also limited. Nano sensors must be validated for their analytical performance in detection of the wide range of the toxic nerve agents present in different samples.

All the nanomaterials used have their own merits and demerits according to their utility (Table 5). AChE nano sensors fabricated with AuNPs have advantage over the other nanomaterials such as CNTs/Nanorods/Nanowires/QDs based AChE sensors. The Au nanoparticles can easily be synthesized in the laboratory and their size can be adjusted according to our need. They are highly conducting and can be used as transducer material in working electrode fabrication. It has been reported that AuNPs based sensors detect the OP compounds ranging from nM-pM concentration. The sensitivity, selectivity & reusability must be enhanced by exploring the properties of gold nanoparticles. The validation of these sensors must be done for the in vitro detection of human samples such as blood, urine etc.


The authors thank the financial support from the Department of Science & Technology, New Delhi, for providing INSPIRE fellowship as SRF-P (IF110655) and to carry out research work.


The authors have no conflict of interest in publication of this article.


  1. Arduini F, Ricci F, Tuta CS, Moscone D, Amine A, Palleschi G. Detection of carbamic and organophosphorus pesticides in water samples using a cholinesterase biosensor based on Prussian blue-modified screen-printed electrode. Anal Chim Acta 2006;580:155-62.
  2. Li BX, He YZ, Xu CL. Simultaneous determination of three organophosphorus pesticide residues in vegetables using continuous-flow chemiluminescence with artificial neural network calibration. Talanta 2007;72:223-30.
  3. FAO, Proceedings of the C 93/94 Document of 27th Session of the FAO Conference, Rome, Italy; 1993.
  4. L Aspelin, US Environmental Protection Agency: Washington, DC; 1994.
  5. Minh CT, Pandey PC, Kumaran S. Studies on acetylcholine sensor and its analytical application based on the inhibition of cholinesterase. Biosens Bioelectron 1990;5:461-71.
  6. Cremisini C, Sario SD, Mela J, Pilloton R, Palleschi G. Evaluation of the use of free and immobilized acetylcholinestrase for paraoxon detection with an amperometric choline oxidase based biosensor. Anal Chim Acta 1995;311:273–80.
  7. Eyer H, Moran DPJ, Rajah KK. Fats in food products. Food Sci Technol 1995;28:162.
  8. Steenland K. Chronic neurological effects of organophosphate pesticides subclinical damage does occur, but longer follow up studies are needed. Br Med J 1996;312:1312–3.
  9. Jamal GA. Neurological syndromes of organophosphorus compounds. Toxol Rev 1997;16:133-70.
  10. Ray DE. Chronic effects of low level exposure to anticholinesterases a mechanistic review. Toxicol Lett 1998;102:527-33.
  11. Donarski WJ, Dumas DP, Heitmeyer DP, Lewis VE, Raushel FM. Structure–activity relationships in the hydrolysis of substrates by the phosphotriesterase from Pseudomonas diminuta. Biochem 1989;28:4650-5.
  12. Chapalamadugu S, Chaudhry GR. Microbiological and biotechnological aspects of metabolism of carbamates and organophosphates. Crit Rev Biotechnol 1992;12:357-89.
  13. Dikshith TSS. Toxicology of Pesticides inAnimals. CRC Press, Boston; 1991. p. 1.
  14. Vreuls JJ, Swen RJ, Goudriaan VP, Kerkhoff MA, Jongenotter GA, Brinkman UA. Automated on-line gel permeation chromatography–gas chromatography for the determination of organophosphorus pesticides in olive oil. J Chromatogra A 1996;750:275-86.
  15. Zhang J, Luo A, Liu P, Wwl S, Wang G, Wei S. Detection of Organophosphorus pesticides using potentiometric enzymatic membrane biosensor based on methylcellulose immobilization. Anal Sci 2009;25:511-5.
  16. Lu WJ, Chen YL, Zhu JH, Chen XG. The combination of flow injection with electrophoresis using capillaries and chips. Electrophor 2009;30:83-91.
  17. Ellman GL, Courtney KD, Andres V, Featherstone RM. A new and rapid colorimetric determination of acetylcholinesterase activity. Biochem Pharmacol 1961;7:88-95.
  18. Hoff GR, Zoonen PV. Trace analysis of pesticides by gas chromatography. J Chromatogra A 1999;843:301-22.
  19. Hernandez F, Sancho JV, Pozo O, Lara A, Pitarch E. Rapid direct determination of pesticides and metabolites in environmental water samples at sub-mg/L level by on-line solid-phase extraction–liquid chromatography–electrospray tandem mass spectrometry. J Chromatogra A 2001;939:1-11.
  20. Sherma J. Thin-layer chromatography of pesticides: a review of applications for 2002–2004. Acta Chromatogra 2005;15:5-30.
  21. Sutherland TD, Horne I, Russell RJ, Oakeshott JG. Gene cloning and molecular characterization of a two-enzyme system catalyzing the oxidative detoxification of b endosulfan. Appl Environ Microbiol 2002;68:6237-45.
  22. Mitobe H, Ibaraki T, Tanabe A, Kawata K, Yasuhara A. High performance liquid chromatographic determination of pesticides in soluble phase and suspended phase in river water. Toxicol Environ Chem 2001;81:97-110.
  23. Wang C, Li XB, Liu YH, Guo YR, Xie R, Gui WJ, et al. Development of a Mab-based heterologous immunoassay for the broad-selective determination of organophosphorus pesticides. J Agric Food Chem 2010;58:5658-63.
  24. Mauriz E, Calle A, Montoya A, Lechuga LM. Determination of environmental organic pollutants with a portable optical immunosensor. Talanta 2006;69:359-64.
  25. Crespilho FN, Luz RAS, Lost RM. Nanomaterials for biosensors and Implantable devices. Nanobioelectrochem 2013;2:27-48.
  26. Periasamy AP, Umasankar Y, Chen SM. Nanomaterials-acetylcholinesterase enzyme matrices for organophosphorus pesticides electrochemical sensors: a review. Sensor 2009;9:4034-55.
  27. Lin TJ, Huang KT, Liu CY. Determination of organophosphorous pesticides by a novel biosensor based on localized surface plasmon resonance. Biosens Bioelectron 2006;22:513-8.
  28. Wang M, Gu XG, Zhang GX, Zhang DQ, Zhu DB. Continuous colorimetric assay for acetylcholinesterase and inhibitor screening with gold nanoparticles. Langmuir 2009;25:2504-07.
  29. Zheng ZZ, Zhou YL, Li XY, Liua SQ, Tang ZY. Highly-sensitive organophosphorous pesticide biosensors based on nanostructured films of acetylcholinesterase and CdTe quantum dots. Biosens Bioelectron 2011;26:3081-5.
  30. Yu T, Shen JS, Bai HH, Guo L, Tang JJ, Jiang YB, et al. A photoluminescent nanocrystalbasedsignaling protocol highly sensitive to nerve agents and highly toxic organophosphate pesticides. Anal 2009;134:2153-7.
  31. Dhull V, Gahlaut A, Dilbaghi N, Hooda V. Acetylcholinesterase biosensors for electrochemical detection of organophosphorus compounds: a review. Biochem Res Int 2013;18:1.
  32. Constantine CA, Gattas-Asfura KM, Mello SV, Crespo G, Rastogi V, Cheng TC, et al. Layer-by-layer films of chitosan, organophosphorus hydrolase and thioglycolic acid-capped cdse quantum dots for the detection of paraoxon. J Phys Chem B 2003;107:13762-4.
  33. Ji XJ, Zheng JY, Xu JM, Rastogi VK, Cheng TC, DeFrank JJ, et al. (CdSe) ZnS quantum dots and organophosphorus hydrolase bioconjugate as biosensors for detection of paraoxon. J Phys Chem B 2005;109:3793-9.
  34. Simonian AL, Good TA, Wang SS, Wild JR. Nanoparticle based optical biosensors for the direct detection of organophosphate chemical warfare agent and pesticides. Anal Chim Acta 2005;534:69-77.
  35. Constantine CA, Asfura KMG, Mello SV, Crespo G, Rastogi V, Cheng TC, et al. Layer-by-layer biosensor assembly incorporating functionalized quantum dots. Langmuir 2003;19:9863-7.
  36. Du D, Chen WJ, Zhang WY, Liu DJ, Li HB, Lin YH. Covalent coupling of organophosphorus hydrolase loaded quantum dots to carbon nanotube/Au nanocomposite for enhanced detection of methyl parathion. Biosens Bioelectron 2010;25:1370-5.
  37. Zhang W, Asiri AM, Liu D, Du D, Lin Y. Nanomaterial-based biosensors for environmental and biological monitoring of organophosphorus pesticides and nerve agents. Trends Anal Chem 2014;54:1.
  38. Pedrosa VA, Paliwal S, Balasubramanian S, Nepal, Davis V, Wild J, et al. Enhanced stability of enzyme organophosphate hy-drolase interfaced on the carbon nanotubes. Colloids Surf B Biointerfa 2010;77:69-74.
  39. Chough SH, Mulchandani A, Mulchandani P, Chen W, Wang J, Rogers KR. Organophosphorus hy-drolase-based amperometric sensor: modulation of sen-sitivity and substrate selectivity. Electroanal 2002;14:273-6.
  40. Deo RP, Wang J, Block I, Mulchandani A, Joshi KA, Trojanowicz M, et al. Determination of organophosphate pesticides at a car-bon nanotube/organophosphorus hydrolase electrochemical biosensor. Anal Chim Acta 2005;530:185-9.
  41. Laothanachareon T, Champreda V, Sritongkham P, Somasundrum M, Surareungchai W. Cross-linked enzyme crystals of organophosphate hydrolase for electrochemical detection of organophosphorus compounds. World J Microbiol Biotechnol 2008;24:3049-55.
  42. Du D, Chen W, Zhang W, Liu D, Li H, Lin Y. Covalent coupling of organophosphorus hydrolase loaded quantum dots to carbon nanotube. au nano-composite for enhanced detection of methyl parathion. Biosens Bioelectron 2010;25:1370-5.
  43. Park KW. Chemical and electronic effects of Ni in Pt/Ni and Pt/Ru/Ni alloy nanoparticles in methanol electrooxidation. J Phys Chem B 2002;106:1869-77.
  44. Deab EI, Ohsaka MS. An extraordinary electrocatalytic reduction of oxygen on gold nanoparticles-electrodeposited gold electrodes. Electrochem Commun 2002;4:288-92.
  45. Upadhyay S, Rao GR, Sharma MK, Bhattacharya BK, Rao VK, Vijayaraghavan R. Immobilization of acetylcholinesterase–choline oxidase on a gold–platinum bimetallic nanoparticles modified glassy carbon electrode for the sensitive detection of organophosphate pesticides, carbamates, and nerve agents. Biosens Bioelectron 2009;25:832-8.
  46. Hrapovic S. Electrochemical biosensing platforms using platinum nanoparticles and carbon nanotubes. Anal Chem 2004;76:1083-8.
  47. Liu CY, Hu JM. Hydrogen peroxide biosensor based on the direct electrochemistry of myoglobin immobilized on silver nanoparticles doped carbon nanotubes film. Biosens Bioelectron 2009;24:2149-54.
  48. Li Z, Wnag X, Wen G, Shuang S, Dong C, Paau MC, et al. Application of hydrophobic palladium nanoparticles for the development of electrochemical glucose biosensor. Biosens Bioelectron 2011;26:4619.
  49. Baioni AP. Copper hexacyanoferrate nanoparticles modified electrodes: a versatile tool for biosensors. J Electroanal Chem 2008;622:219-24.
  50. Salimi A, Hallaj R, Soltanian S. Fabrication of a sensitive cholesterol biosensor based on cobalt oxide nanostructures electrodeposited onto glassy carbon electrode. Electroanalysis 2009;21:2693-700.
  51. Astruc D, Chardac F. Dendritic catalysts and dendrimers in catalysis. Chem Rev 2001;101:2991-3024.
  52. Crooks RM. Dendrimer-encapsulated metal nanoparticles: synthesis, characterization, and applications to catalysis. Acc Chem Res 2001;34:181-90.
  53. Siqueira JR. Bifunctional electroactive nanostructured membranes. Electrochem Commun 2007;9:2676-80.
  54. Viswanathan S, Radecka H, Radecki J. Electrochemical biosensor for pesticides based on acetylcholinesterase immobilized on polyaniline deposited on vertically assembled carbon nanotubes wrapped with ssDNA. Biosens Bioelectron 2009;24:2772-7.
  55. Bucur B, Fournier D, Danet A, Marty JL. Biosensors based on highly sensitive acetylcholinesterases for enhanced carbamate insecticides detection. Anal Chim Acta 2006;562:115-21.
  56. Shulga O, Kirchhoff JR. An acetylcholinesterase enzyme electrode stabilized by an electrodeposited gold nanoparticle layer. Electrochem Commun 2007;9:935-40.
  57. Song Y, Zhang M, Wang L. A novel biosensor based on acetylecholinesterase/prussian blue-chitosan modified electrode for detection of carbaryl pesticides. Electrochim Acta 2011;56:7267-71.
  58. Andreescu S, Noguer T, Magearu V, Marty JL. Screenprinted electrode based on ache for the detection of pesticides in presence of organic solvents. Talanta 2002;57:169-76.
  59. Wu S, Huang F, Lan X, Wang X, Wang J, Meng C. Electrochemically reduced graphene oxide and Nafion nanocomposite for ultralow potential detection of organophosphate pesticide. Sens Actuators B 2013;177:724-9.
  60. Upadhyay S, Rao GR, Sharma MK, Bhattacharya BK, Rao VK, Vijayaraghavan R. Immobilization of acetylcholineesterase-choline oxidase on a gold-platinum bimetallic nanoparticles modified glassy carbon electrode for the sensitive detection of organophosphate pesticides, carbamates and nerve agents. Biosens Bioelectro 2009;25:832-8.
  61. Dyk JSV, Pletschke B. Review on the use of enzymes for the detection of organochlorine, organophosphate and carbamate pesticides in the environment. Chemosphere 2011;82:291-307.
  62. Du D, Chen S, Cai J, Zhang A. Immobilization of acetylcholinesterase on gold nanoparticles embedded in solgel film for amperometric detection of organophosphorous insecticide. Biosens Bioelectron 2007;23:130-4.
  63. Wink T, Zuilen SJV, Bult A, Bennekom WPV. Selfassembled monolayers for biosensors. Analyst 1997;122:43R-50R.
  64. Campas M, Simon BP, Marty JL. A review of the use of genetically engineered enzymes in electrochemical biosensors. Semin Cell Dev Biol 2009;20:3-9.
  65. Adhikari B, Majumdar S. Polymers in sensor applications. Prog Polym Sci (Oxford) 2004;29:699-766.
  66. Dhawan G, Sumana G, Malhotra BD. Recent developments in urea biosensors. Biochem Eng J 2009;44:42-52.
  67. Alonso GA, Istamboulie G, Noguer T, Marty JL, Munoz R. Rapid determination of pesticide mixtures using disposable biosensors based on genetically modified enzymes and artificial neural networks. Sens Actuators B 2012;164:22-8.
  68. Guerente LC, Cosnier S, Innocent C, Mailley P. Development of amperometric biosensors based on the immobilization of enzymes in polymer films electrogenerated from a series of amphiphilic pyrrole derivatives. Anal Chim Acta 1995;311:23-30.
  69. Jie G, Liu B, Pan H, Zhu JJ, Chen HY. CdS nanocrystal-based electrochemiluminescence biosensor for the detection of low-density lipoprotein by increasing sensitivity with gold nanoparticle amplification. Anal Chem 2007;79:5574-81.
  70. Wang D, Rogach AL, Caruso F. Semiconductor quantum dot-labeled microsphere bioconjugates prepared by stepwise self-assembly. Nano Lett 2002;2:857-61.
  71. Pundir CS, Chauhan N. Acetylcholinesterase inhibition based biosensors for pesticide determination: a review. Anal Biochem 2012;429:19-31.
  72. Sun X, Wang X. Acetylcholinesterase biosensor based on prussian blue-modified electrode for detecting organophosphorous pesticides. Biosens Bioelectron 2010;25:2611-4.
  73. Wang K, Li HN, Wu J. TiO2-decorated graphene nanohybrids for fabricating an amperometric acetylcholinesterase biosensor. Analyst 2011;136:3349-54.
  74. Ion AC, Ion I, Culetu A. Acetylcholinesterase voltammetric biosensors based on carbon nanostructure-chitosan composite material for organophosphate pesticides. Mater Sci Eng C 2010;30:817-21.
  75. Ivanov AN, Younusov RR, Evtugyn GA, Arduini F, Moscone D, Palleschi G. Acetylcholinesterase biosensor based on single-walled carbon nanotubes—co phthalocyanine for organophosphorus pesticides detection. Talanta 2011;85:216-21.
  76. Norouzi P, Hamedani MP, Ganjali MR, Faridbod F. A novel acetylcholinesterase biosensor based on chitosan-gold nanoparticles film for determination of monocrotophos using FFT continuous cyclic voltammetry. Int J Electrochem Sci 2010;5:1434-46.
  77. Wang K, Liu Q, Dai L. A highly sensitive and rapid organophosphate biosensor based on enhancement of CdS decorated graphene nanocomposite. Anal Chim Acta 2011;695:84-8.
  78. Du D, Huang X, Cai J, Zhang A. Comparison of pesticide sensitivity by electrochemical test based on acetylcholinesterase biosensor. Biosens Bioelectron 2007;23:285-9.
  79. Wink T, Zuilen SJV, Bult A, Bennekom WPV. Self assembled monolayers for biosensors. Analyst 1997;122:43R-50R.
  80. Zheng M, Jagota A, Strano MS, Santos AP, Barone P, Chou SG, et al. Structure-based carbon nanotube sorting by sequence-dependent DNA assembly. Sci 2003;302:1545-8.
  81. Viswanathan S, Wu LC, Huang MR, Ho JAA. Electrochemical immunosensor for cholera toxin using liposomes and poly(3,4-ethylenedioxythiophene)-coated carbon nanotubes. Anal Chem 2006;78:1115-21.
  82. Viswanathan S, Radecki J. Nanomaterials in electrochemical biosensors for food analysis–A Review. Pol J Food Nutr Sci 2008;58:157-64.
  83. Katz E, Willner I, Wang J. Electroanalytical and bioelectroanalytical systems based on metal and semiconductor nanoparticles. Electroanalysis 2004;16:19-44.
  84. Renault NJ, Martelet C, Chevolot Y, Cloarec JP. Biosensors and bio-bar code assays based on biofunctionalized magnetic microbeads. Sensors 2007;7:589-614.
  85. Kandimalla V, Ju H. Binding of acetylcholinesterase to multi-wall carbon nanotube-cross-linked chitosan composite for flow-injection amperometric detection of an organophosphorous insecticide. Chem Eur J 2006;12:1074-80.
  86. Quezada BC, Delia ML, Bergel A. Electrochemical microstructuring of graphite felt electrodes for accelerated formation of electroactive biofilms on microbial anodes. Electrochem Commun 2011;101:2748-54.
  87. Deo RP, Wang J, Block I, Mulchandani A, Joshi KA, Trojanowicz M, et al. Determination of organophosphate pesticides at a carbon nanotube/organophosphorus hydrolase electrochemical biosensor. Anal Chimi Acta 2005;530:185-9.
  88. Banks EC, Compton RG. New electrodes for old: from carbon nanotubes to edge plane pyrolytic graphite. Analyst 2006;131:15-21.
  89. Giordano N, Antonucci PL, Passalacqua E, Pino L, Arico AS, Kinoshita K. Relationships between physicochemical properties and electrooxidation behaviour of carbon materials. Electrochimi Acta 1991;36:1931-5.
  90. Boudenne JL, Cerclier O, Galea J, Vlist EV. Electrochemical oxidation of aqueous phenol at a carbon black slurry electrode. Appl Catal 1996;143:185-202.
  91. Somerset VS, Klink MJ, Baker PGL, Iwuoha EI. Acetylcholinesterase-polyaniline biosensor investigation of organophosphate pesticides in selected organic solvents. J Environ Sci Health B 2007;42:297-304.
  92. Palchetti I, Cagnini A, Carlo MD, Coppi C, Mascini M, Turner APF. Determination of anticholinesterase pesticides in real samples using a disposable biosensor. Anal Chimi Acta 1997;337:315-21.
  93. Andreescu S, Barthelmebs L, Marty JL. Immobilization of acetylcholinesterase on screen-printed electrodes: comparative study between three immobilization methods and applications to the detection of organophosphorus insecticides. Anal Chimi Acta 2002;464:171-80.
  94. Sotiropoulou S, Chaniotakis NA. Tuning the solgel microenvironment for acetylcholinesterase encapsulation. Biomaterial 2005;26:6771-9.
  95. Du D, Wang M, Cai J, Qin Y, Zhang A. One-step synthesis of multiwalled carbon nanotubes-gold nanocomposites for fabricating amperometric acetylcholinesterase biosensor. Sens Actuators B 2010;143:524-9.
  96. Wei Y, Li Y, Qu Y, Xiao F, Shi G, Jin L. A novel biosensor based on photoelectro-synergistic catalysis for flow-injection analysis system/amperometric detection of organophosphorous pesticides. Anal Chimi Acta 2009;643:13-8.
  97. Sharma SP, Tomar LNS, Acharya J, Chaturvedi A, Suryanarayan MVS, Jain R. Acetylcholinesterase inhibition based biosensor for amperometric detection of Sarin using single-walled carbon nanotube-modified ferrule graphite electrode. Sens Actuators B 2012;166-167:616-23.
  98. Gooding JJ, Hibbert DB. The application of alkanethiols self-assembled monolayers to enzyme electrodes. Trends Anal Chem 1999;18:525-33.
  99. Kaku T, Karan HI, Okamoto Y. Amperometric glucose sensors based on immobilized glucose oxidase-polyquinone system. Anal Chem 1994;66:1231-5.
  100. Alivisatos AP. Semiconductor clusters, nanocrystals, and quantum dots. Sci 1996;271:933-7.
  101. Li J, Lin XQ. Glucose biosensor based on immobilization of glucose oxidase in poly(o-aminophenol) film on polypyrrole-Pt nanocomposite modified glassy carbon electrode. Biosens Bioelectron 2007;22:2898-905.
  102. Cosnier S, Senillou A, Gratzel M, Comte P, Vlachopoulos N, Rnault NJ, et al. A glucose biosensor based on enzyme entrapment within polypyrrole films electrodeposited on mesoporous titanium dioxide. J Electroanal Chem 1999;469:176-81.
  103. Retama JR, Cabarcos EL, Mecerreyes D, Ruiz BL. Design of an amperometric biosensor using polypyrrole-micro gel composites containing glucose oxidase. Biosens Bioelectron 2004;20:1111-7.
  104. Njagi J, Andreescu S. Stable enzyme biosensors based on chemically synthesized Au– polypyrrole nanocomposites. Biosens Bioelectron 2007;23:168-75.
  105. Gong J, Wang L, Zhang L. Electrochemical biosensing of methyl parathion pesticide based on acetylcholinesterase immobilized onto Au-polypyrrole interlaced network-like nanocomposite. Biosens Bioelectron 2009;24:2285-8.
  106. Allen MJ, Tun VC, Kaner RB. Honeycomb Carbon: a review of graphene. Chem Rev 2010;110:132-45.
  107. Novoselov KS, Geim AK, Morozov SV, Jiang D, Zhang Y, Dubonos SV. Electric field effect in atomically thin carbon films. Sci 2004;306:666-9.
  108. Li D, Muller MB, Gilje S, Kaner RB, Wallace GG. Processable aqueous dispersions of graphene nanosheets. Nat Nanotechnol 2008;3:101-5.
  109. Allen MJ, Tun VC, Kaner RB. Honeycomb Carbon: a review of graphene. Chem Rev 2010;110:132-45.
  110. Stankovich S, Dikin DA, Dommett GHB, Kohlhaas KM, Zimney EJ, Stach EA, et al. Graphene-based composite materials. Nature 2006;442:282-6.
  111. Fowler JD, Allen JM, Tung VC, Yang Y, Weiller BH. Practical chemical sensors from chemically derived graphene. ACS Nano 2009;3:301-06.
  112. Robinson JT, Perkins FK, Snow ES, Wei ZQ, Sheehan PE. Reduced graphene oxide molecular sensors. Nano Lett 2008;8:3137-40.
  113. Mohanty N, Berry V. Graphene-based single-bacterium resolution biodevice and dna transistor: interfacing graphene derivatives with nanoscale and microscale biocomponents. Nano Lett 2008;8:4469-76.
  114. Wang Y, Shao YY, Matson DW, Li JH, Lin YH. Nitrogen-doped graphene and its application in electrochemical biosensing. ACS Nano 2010;4:1790-8.
  115. Wu H, Wang J, Kang XH, Wang CM, Wang DH, Liu J, et al. Glucose biosensor based on immobilization of glucose oxidase in platinum nanoparticles/graphene/chitosan nanocomposite film. Talanta 2009;80:403-6.
  116. Rafiee MA, Rafiee J, Wang Z, Song H, Yu ZZ, Koratkar N. Enhanced mechanical properties of nanocomposites at low graphene content. ACS Nano 2009;3:3884-90.
  117. Ao ZM, Yang J, Li S, Jiang Q, Ao ZM, Yang J, et al. Enhancement of CO detection in Al doped graphene Chem Phys Lett 2008;461:276-9.
  118. Rafiee MA, Rafiee J, Srivastava I, Wang Z, Song H, Yu Z, et al. Fracture and fatigue in graphene nanocomposites. Small 2010;6:179-83.
  119. Ion AC, Ion I, Culetu A, Ghuase D, Moldovan CA, Iosub R, et al. Acetylcholinesterase voltammetric biosensors based on carbon nanostructure chitosan composite material for organophosphate pesticides. Mater Sci Eng C 2010;30:817-21.
  120. Valcarcel M, Cardenas S, Simonet BM, Martinez YM, Lucena R. Carbon nanostructures as sorbent materials in analytical processes. Trends Anal Chem 2008;27:34-43.
  121. Kachoosangi RT, Musameh MM, Yousef IA, Yousef JM, Kanan SM, Xiao L, et al. Carbon nanotubeionic liquid composite sensors and biosensors. Anal Chem 2009;81:435-42.
  122. Sirvent MA, Merkoci A, Alegret S. Pesticide determination in tap water and juice samples using disposable amperometric biosensors made using thick-film technology. Anal Chim Acta 2001;442:35-44.
  123. Marques PRB, Nunes GS, Santos TCR, Andreescu S, Marty JL. Comparative investigation between acetylcholinesterase obtained from commercial sources and genetically modified Drosophila melanogaster: application in amperometric biosensors for methamidophos pesticide detection. Biosens Bioelectron 2004;20:825-32.
  124. Wang K, Li HN, Wu J, Ju C, Yan JJ, Liu Q, et al. TiO2-decorated graphene nanohybrids for fabricating an amperometric acetylcholinesterase biosensor. Analyst 2011;136:3349-54.
  125. Ion AC, Ion I, Culetu A, Ghuase D, Moldovan CA, Iosub R, Dinescu A. Acetylcholinesterase voltammetric biosensors based on carbon nanostructure chitosan composite material for organophosphate pesticides. Mater Sci Eng C 2010;30:817-21.
  126. Wang K, Liu Q, Dai L, Yan J, Ju C, Qiu B, et al. A highly sensitive and rapid organophosphate biosensor based on enhancement of CdS-decorated graphene nanocomposite. Anal Chimi Acta 2011;695:84-8.