Acetylcholinesterase based biosensor for monitoring of Malathion and Acephate in food samples: A voltammetric study

Single-atom Zr-doped CoOOH with enhanced electrical conductivity as a signal amplifier and detection probe for the indirect non-enzymatic electrochemical determination of malathion in foods

Herein, a novel electrochemical sensor based on zirconium-doped cobalt oxyhydroxide (ZrCoOOH) was proposed for highly sensitive non-enzymatic determination of malathion (MAL). The doping of Zr can improve the electrical conductivity of CoOOH, of which the transfer resistance was reduced from 241.1 Ω to 140.2 Ω. Furthermore, the X-ray photoelectron spectroscopy confirmed that part of Co2+ was converted to Co3+ due to the introduction of Zr. The Co3+ in ZrCoOOH could react with MAL to form Co2+, which enhanced the electrooxidation current of Co2+. Therefore, the peak current of Co2+ was served as detection probe for MAL. Under optimal conditions, the developed sensor established the linear relationship for MAL in the concentration range of 0.001-10.0 μM with a low limit of detection (0.64 nM). The constructed sensor was employed to detect MAL in food samples (peach, kiwi fruit, spinach and tomato), verifying the accuracy and practicability of the sensor.

Bio-inspired aptamers decorated gold nanoparticles enable visualized detection of malathion

Biosensors always respond to the targets of interest in a specific manner, employing biological or bio-mimic recognition elements such as antibodies and aptamers. Inspired by target recognition in nature, an aptamer-mediated, gold nanoparticle-based sensing approach is developed in this work for effective determination of malathion. The sensing system consists of negatively charged aptamer probes, and polycationic proteins, protamine, as well as exceptional colorimetric nanoprobes, barely gold nanoparticles (AuNPs). Protamine molecules bound to aptamer probes hinder the aggregation of AuNPs, while no such inhibition is maintained when aptamer-specific malathion is introduced into the solution, thus leading to the solution colour change from red to blue observable by the naked eye. The assay is accomplished via a mix-and-measure step within 40 min with a detection limit as low as 1.48 μg/L (3σ/s rule). The assay method also exhibits high selectivity and good applicability for the quantification of malathion in tap water with recovery rates of 98.9%-109.4%. Additionally, the good detection accuracy is also confirmed by the high-performance liquid chromatography method. Therefore, the non-enzymatic, label- and device-free characteristics make it a robust tool for malathion assay in agricultural, environmental, and medical fields.

Recent Advances on Detection of Insecticides Using Optical Sensors

Insecticides are enormously important to industry requirements and market demands in agriculture. Despite their usefulness, these insecticides can pose a dangerous risk to the safety of food, environment and all living things through various mechanisms of action. Concern about the environmental impact of repeated use of insecticides has prompted many researchers to develop rapid, economical, uncomplicated and user-friendly analytical method for the detection of insecticides. In this regards, optical sensors are considered as favorable methods for insecticides analysis because of their special features including rapid detection time, low cost, easy to use and high selectivity and sensitivity. In this review, current progresses of incorporation between recognition elements and optical sensors for insecticide detection are discussed and evaluated well, by categorizing it based on insecticide chemical classes, including the range of detection and limit of detection. Additionally, this review aims to provide powerful insights to researchers for the future development of optical sensors in the detection of insecticides.

An efficient LSPR method to quantitatively detect dimethoate: Development, characterization and evaluation

In recent years, there has been growing concern among consumers about pesticide contamination in fruits. Therefore, rapid, reliable, and consistent detection methods for OPPs, especially dimethoate, are crucially needed. The existing quantitative methods for detecting dimethoate are not suitable for rapid measuring system such as the dimethoate samples from two channels. Hence this paper examines the utilization of a dual-channel system for utilize the absorption variations of the Localized Surface Plasmon Resonance (LSPR) bands of gold nanoparticles (AuNPs) were investigate for detection of dimethoate. Under optimized conditions, the relationship between concentrations of dimethoate and absorbance ratios (A(520)/A(640)) was linearly found in the concentration range of 10–100 nM. Result from the experiment shows that both channels exhibit a linear correlation coefficient as high as 0.97 and a limit of detection (LOD) as low as 5.5 nM. This LSPR detection system was characterized by testing the dimethoate in apple samples and the recovery rates were found to be in the range of 85.90% to 107.37%. The proposed dual-channel LSPR system for detecting dimethoate creating a new approach for detecting organophosphate insecticide in agricultural fields. It could lay the foundation for designing a high-throughput analysis of the insecticides using a wavelength division multiplexing switch (WDMS).

An Overview on the Mechanisms and Applications of Enzyme Inhibition-Based Methods for Determination of Organophosphate and Carbamate Pesticides

Acetylcholinesterase inactivating compounds, such as organophosphate (OP) and carbamate (CM) pesticides, are widely used in agriculture to ensure sustainable production of food and feed. As a consequence of their applications, they would result in neurotoxicity, even death. In this essence, the development of enzyme inhibition methods still shows great significance as rapid detection techniques for on-site large-scale screening of OPs and CMs. Initially, mechanisms and applications of various enzyme-inhibition-based methods and devices, including optical colorimetric assay, fluorometric assays, electrochemical biosensors, rapid test card, and microfluidic device, are highlighted in the present overview. Further, to enhance the enzyme sensitivity for detection; alternative enzyme sources or high yield enrichment methods (such as abzyme, artificial enzyme, and recombinant enzyme), as well as enzyme reactivation and identification, are also addressed in this comprehensive overview.

Easy-to-use and reliable absorbance-based MPH-GST biosensor for the detection of methyl parathion pesticide

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Simple, inexpensive, high-efficiency absorbance-based OP biosensor was fabricated.

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Covalently immobilized methyl parathion hydrolase was used as a biomolecule.

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The biosensor can be used at room temperature for 100 rounds repetitively.

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The biosensor could detect MP with the detection limit of 0.1 μM.

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The biosensor showed high reliability for detecting MP in real samples.

Due to high contamination of organophosphate (OP) insecticides in agricultural products and the environment, efficient and convenient devices for their monitoring are necessary. Here, a simple, inexpensive, efficient, and easy-to-use absorbance-based biosensor was fabricated utilizing recombinant methyl parathion hydrolase fused with glutathione-S-transferase (MPH-GST), covalently immobilized onto a chitosan film-coated polystyrene microplate, for the detection of methyl parathion (MP) as a representative of OPs. Having been connected to the transducer system designed to work through an Arduino microcontroller, the biosensor could detect MP as efficiently as the conventional methods, with the detection limit of 0.1 μM, the lowest value ever reported for this method. It was stable at 25 °C for 30 days, could function 100 rounds repetitively, and yielded high recovery with real samples. Hence, this simply designed MPH-GST biosensor could be an easy and inexpensive alternative for efficient OP screening at site to help control its contamination.

Simulated revelation of the adsorption behaviours of acetylcholinesterase on charged self-assembled monolayers

An acetylcholinesterase (AChE)-based electrochemical biosensor, as a promising alternative to detect organophosphates (OPs) and carbamate pesticides, has gained considerable attention in recent years, due to the advantages of simplicity, rapidity, reliability and low cost. The bio-activity of AChE immobilized on the surface and the direct electron transfer (DET) rate between an enzyme and an electrode directly determined the analytical performances of the AChE-based biosensor, and experimental studies have shown that the charged surfaces have a strong impact on the detectability of the AChE-based biosensor. Therefore, it is very important to reveal the behaviour of AChE in bulk solution and on charged surfaces at the molecular level. In this work, the adsorption orientation and conformation of AChE from Torpedo californica (TcAChE) on oppositely charged self-assembled monolayers (SAMs), COOH-SAM and NH₂-SAM with different surface charge densities, were investigated by parallel tempering Monte Carlo (PTMC) and all-atom molecular dynamics simulations (AAMD). Simulation results show that TcAChE could spontaneously and stably adsorb on two oppositely charged surfaces by the synergy of an electric dipole and charged residue patch, and opposite orientations were observed. The active-site gorge of TcAChE is oriented toward the surface with the "end-on" orientation and the active sites are close to the surface when it is adsorbed on the positively charged surface and the tunnel cost for the substrate is lower than that on the negatively charged surface and in bulk solution, while for TcAChE adsorbed on the negatively charged surface, the active site of TcAChE is far away from the surface and the active-site gorge is oriented toward the solution with a "back-on" orientation. It suggests that the positively charged surface could provide a better microenvironment for the efficient bio-catalytic reaction and quick DET between TcAChE and the electrode surface. Moreover, the RMSD, RMSF, dipole moment, gyration radius, eccentricity and superimposed structures show that only a slight conformational change occurred on the relatively flexible structure of TcAChE during simulations, and the native conformation is well preserved after adsorption. This work helps us better comprehend the adsorption mechanism of TcAChE on charged surfaces and might provide some guidelines for the development of new TcAChE-based amperometric biosensors for the detection of organophosphorus pesticides.

Toxic effects and possible mechanisms following malathion exposure in porcine granulosa cells

Malathion is a wide spectrum organophosphorothionate insecticide that is frequently found in drinking water, food and foodstuffs. Ovarian granulosa cells modulate oogenesis by providing metabolic nutrients to oocytes. They can decide the fate of folliculogenesis and oocyte maturation by supplying regulatory cues that help in reproduction. However, little is known about the underlying mechanisms of malathion as a reproductive toxicant in porcine granulosa cells. In the present study, we found that malathion has obvious toxic effects on cultured porcine granulosa cells in a dose-dependent manner. Malathion exposure resulted in significantly increased oxidative stress levels and DNA damage response, which was measured by the mRNA expression levels of homologous recombination (HR) pathway and non-homologous end-joining (NHEJ) pathway-related genes. Subsequently, it was found that malathion exposure could induce apoptosis and autophagy by qRT-PCR and fluorescence intensity analysis. In conclusion, malathion is a reproductive toxicant by inhibiting granulosa cell proliferation by multiple pathways connected to oxidative stress, DNA damage, apoptosis and autophagy.

Non-Enzymatic Electrochemical Sensing of Malathion Pesticide in Tomato and Apple Samples Based on Gold Nanoparticles-Chitosan-Ionic Liquid Hybrid Nanocomposite

Malathion (MLT) is an organophosphorous type pesticide and having seriously high toxicity and electrochemical platforms for rapid, simple, inexpensive and sensitive determination of pesticides is still a special concern. This paper describes a simple preparation of a composite film consisting of ionic liquid (IL), chitosan (CS) and electrochemically synthesized gold nanoparticles (AuNPs) on single use pencil graphite electrodes (PGEs). The microscopic and electrochemical characterization of AuNP-CS-IL/PGE was studied using scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. This fabricated surface was then explored for the first time as a sensing matrix for the non-enzymatic electrochemical sensing of malathion by cyclic voltammetry and square wave voltammetry measurements. The proposed AuNP-CS-IL/PGE showed excellent characteristics and possessed remarkable affinity for malathion. The voltammetric current response exhibited two linear dynamic ranges, 0.89–5.94 nM and 5.94–44.6 nM reflecting two binding sites, with a detection limit of 0.68 nM. The method was applied in real sample analysis of apple and tomato. The results demonstrate the feasibility of AuNP-CS-IL-modified electrodes for simple, fast, ultrasensitive and inexpensive detection of MLT.

The mechanisms and process of acephate degradation by hydroxyl radical and hydrated electron

The degradation process of acephate in aqueous solution with ^•OH and eaq− produced by ⁶⁰Co-γ irradiation and electron pulse radiolysis was studied in the present paper. In the aqueous solution, acephate reacted with eaq− and transformed to transient species which can absorb weakly in the wavelength range of 300–400 nm and decay very fast. According to the decay of hydrated electron, the reaction rate constant of eaq− and acephate is (3.51 ± 0.076) × 10⁹ dm³·mol⁻¹·s⁻¹. The transient species produced in the reaction of ^•OH and acephate do not distinctly absorb the light in the wavelength range of 300–700 nm, so the decay and kinetics of the transient species cannot determinedirectly. The competing reaction of KSCN oracephate with ^•OH were studied to obtain the reaction rate constant of ^•OH and acephate, which is (9.1 ± 0.11) × 10⁸ dm³·mol⁻¹·s⁻¹. Although acetylamide and inorganic ions were determined in the products of the reaction of acephate with ^•OH or eaq−, the concentration of inorganic ions in the products of the reaction of acephate with ^•OH is higher than that in the product of the reaction of acephate with eaq−. Moreover, there were sulfide in the products of the reaction of acephatewith eaq−. The degradation pathways of acephate by ^•OH and eaq− were also proposed based on the products from GC-MS.

The Use of Electrochemical Biosensors in Food Analysis

Rapid and accurate analysis of food produce is essential to screen for species that may cause significant health risks like bacteria, pesticides and other toxins. Considerable developments in analytical techniques and instrumentation, for example chromatography, have enabled the analyses and quantitation of these contaminants. However, these traditional technologies are constrained by high cost, delayed analysis times, expensive and laborious sample preparation stages and the need for highly-trained personnel. Therefore, emerging, alternative technologies, for example biosensors may provide viable alternatives. Rapid advances in electrochemical biosensors have enabled significant gains in quantitative detection and screening and show incredible potential as a means of countering such limitations. Apart from demonstrating high specificity towards the analyte, these biosensors also address the challenge of the multifactorial food industry of providing high analytical accuracy amidst complex food matrices, while also overcoming differing densities, pH and temperatures. This (public and Industry) demand for faster, reliable and cost-efficient analysis of food samples, has driven investment into biosensor design. Here, we discuss some of the recent work in this area and critique the role and contributions biosensors play in the food industry. We also appraise the challenges we believe biosensors need to overcome to become the industry standard.

Chitosan-iron oxide nanocomposite based electrochemical aptasensor for determination of malathion

An electrochemical aptasensor based on chitosan-iron oxide nanocomposite (CHIT-IO) film deposited on fluorine tin Oxide (FTO) was developed for the detection of malathion. Iron oxide nanoparticles were prepared by co-precipitation method and characterized by Transmission electron microscopy and UV-Visible spectroscopy. The biotinylated DNA aptamer sequence specific to the malathion was immobilized onto the iron oxide doped-chitosan/FTO electrode by using streptavidin as linking molecule. Various characterization studies like Field Emission-Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Electrochemical studies were performed to attest the successful fabrication of bioelectrodes. Experimental parameters like aptamer concentration, response time, stability of electrode and reusability studies were optimized. Aptamer immobilized chitosan-iron oxide nanocomposite (APT/SA/CHIT-IO/FTO) bioelectrodes exhibited LOD of about 0.001 ng/mL within 15 min and spike-in studies revealed about 80-92% recovery of malathion from the lettuce leaves and soil sample.

Preparation of malathion MIP-SPE and its application in environmental analysis

Malathion is an organophosphorous insecticide for controlling insects on fruits and vegetables, miscellaneous household insects, and animal parasites. It is important to develop highly efficient and selective pre-treatment method for analyzing malathion residues in environment and samples from agricultural products based on the molecularly imprinted polymers (MIPs). In this study, we developed a tailor-made MIP method with highly specific recognization to the template. The MIPs were prepared using malathion as a template, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, azodiisobutyronitrile (AIBN) as an initiator, and the acetonitrile-chloroform (1:1, v/v) as a porogen. The molecular recognization mechanism of malathion and MAA was evaluated by molecular simulation, ultraviolet spectrometry (UV), and (1)H-nuclear magnetic resonance ((1)H-NMR). MAA interacted specifically with malathion by hydrogen bond with a ratio of 2:1. The MIPs exhibit a high affinity, recognition specificity, and efficient adsorption performance for malathion. The Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), surface area and porosimeter analyzer, thermogravimetric/differential thermal analyzer (TG/DTA) were used to characterize the properties of MIP. The malathion residues in soil, tap water, and cabbage were cleaned up by MIP-SPE, detected quantitatively using GC-FPD, and confirmed by GC-MS/MS. The limits of tap water, soil, and cabbage were confined to 0.001 mg L(-1), 0.004 and 0.004 mg kg(-1), respectively. The spiked recoveries of malathion were 96.06-111.49% (with RSD being 5.7-9.2%), 98.13-103.83% (RSD, 3.5-8.7%), and 84.94-93.69% (RSD, 4.7-5.8%) for tap water, soil, and cabbage samples, respectively. Thus, the method developed here can be used effectively in assessing malathion residues in multiple environmental samples. The aim of the study was to provide an efficient, selective, and accurate method for analyzing malathion at trace levels in multiple media.

Preparation of yolk-shell structured copper oxide@silica oxide spheres and their application in high performance electrochemical sensing of Formoterol fumarate residues in swine feed and tissues

In this paper, we report a facile route to synthesize yolk-shell structured copper oxide@silica oxide (CuO@SiO2) spheres and their application to construct an electrochemical Formoterol fumarate (FF) sensor. The CuO@SiO2 was characterized by means of Fourier transform infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Further, FF was electrocatalytically oxidized at the CuO@SiO2 film modified glassy carbon electrode (GCE), which led to a sensitive determination of FF. The oxidation current of FF was linear with concentration in the range of 0.030-10 μM and the detection limit was found to be 5.0 nM (S/N = 3). The observed analytical parameters such as wide linear range, low detection limit and short response time were superior to previously reported FF sensors. Finally, it was demonstrated that the proposed sensor could be used for the selective determination of FF present in swine feed and tissues.

A sensitive amperometric acetylcholine biosensor based on carbon nanosphere and acetylcholinesterase modified electrode for detection of pesticide residues

A sensitive biosensor based on acetylcholinesterase (AChE) and carbon nanosphere (CNS) immobilized on a glassy carbon electrode was developed for the detection of pesticides by the inhibition of AChE activity. The inhibition effect of the pesticides resulted in a decrease of current response of the acetylthiocholine chloride that was used as a substrate to obtain an electrochemical signal. When applied to the pesticides carbofuran and fenitrothion, the designed biosensor exhibited high sensitivity and low detection limits. The inhibition ratio of carbofuran and fenitrothion were linearly proportional to their concentrations ranging from 0.40 to 4.79 and 6.26 to 125.31 μg/L, respectively. The theoretical detection limits were found to be 0.082 μg/L for carbofuran and 2.61 μg/L for fenitrothion. Furthermore, as the biosensor offers good reproducibility and stability, it could be used for trace detection of pesticides in real samples. Compared with other AChE biosensors, the proposed biosensor was convenient and it exhibited extreme sensitivity to pesticides.

Borinic acid block copolymers: new building blocks for supramolecular assembly and sensory applications

Borinic acid functional groups were incorporated into block copolymers via RAFT polymerization and their supramolecular assembly and sensor applications were investigated.

In situ growth of metallic silver on glucose oxidase for a highly sensitive glucose sensor

A bio-composite was assembled by in situ reducing Ag⁺ to Ag in glucose oxidase solution and used to detect glucose.

Biosensors containing acetylcholinesterase and butyrylcholinesterase as recognition tools for detection of various compounds

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are enzymes expressed in the human body under physiological conditions. AChE is an important part of the cholinergic nerves where it hydrolyses neurotransmitter acetylcholine. Both cholinesterases are sensitive to inhibitors acting as neurotoxic compounds. In analytical applications, the enzymes can serve as a biorecognition element in biosensors as well as simple disposable sensors (dipsticks) and be used for assaying the neurotoxic compounds. In the present review, the mechanism of AChE and BChE inhibition by disparate compounds is explained and methods for assaying the enzymes activity are shown. Optical, electrochemical, and piezoelectric biosensors are described. Attention is also given to the application of sol-gel techniques and quantum dots in the biosensors’ construction. Examples of the biosensors are provided and the pros and cons are discussed.

Inhibitors of acetylcholinesterase and butyrylcholinesterase meet immunity

Acetylcholinesterase (AChE) inhibitors are widely used for the symptomatic treatment of Alzheimer’s disease and other dementias. More recent use is for myasthenia gravis. Many of these inhibitors interact with the second known cholinesterase, butyrylcholinesterase (BChE). Further, evidence shows that acetylcholine plays a role in suppression of cytokine release through a “cholinergic anti-inflammatory pathway” which raises questions about the role of these inhibitors in the immune system. This review covers research and discussion of the role of the inhibitors in modulating the immune response using as examples the commonly available drugs, donepezil, galantamine, huperzine, neostigmine and pyridostigmine. Major attention is given to the cholinergic anti-inflammatory pathway, a well-described link between the central nervous system and terminal effector cells in the immune system.

Preparation, characterization and analytical application of an electrochemical laccase biosensor towards low level determination of isoprenaline in human serum samples

A novel electrochemical biosensor has been developed based on the immobilization of multiwalled carbon nanotubes (MWCNT) followed by sol–gel entrapment of laccase (Lac) enzyme on to the GCE.