Screening of Carbamate and Organophosphate Pesticides in Food Matrices Using an Affordable and Simple Spectrophotometric Acetylcholinesterase Assay

Aptamer-modified paper-based analytical devices for the detection of food hazards: Emerging applications and future perspective

Food analysis plays a critical role in assessing human health risks and monitoring food quality and safety. Currently, there is a pressing need for a reliable, portable, and quick recognition element for point-of-care testing (POCT) to better serve the demands of on-site food analysis. Aptamer-modified paper-based analytical devices (Apt-PADs) have excellent characteristics of high portability, high sensitivity, high specificity, and on-site detection, which have been widely used and concerned in the field of food safety. The article reviews the basic components and working principles of Apt-PADs, and introduces their representative applications detecting food hazards. Finally, the advantages, challenges, and future directions of Apt-PADs-based sensing performance are discussed, to provide new directions and insights for researchers to select appropriate Apt-PADs according to specific applications.

Pesticide Identification Using Surface-Enhanced Raman Spectroscopy and Density Functional Theory Calculations: From Structural Insights to On-Site Detection

Pesticides play an important role in conventional agriculture. Yet, their harmful effects on the environment are becoming increasingly apparent. The occurrence of pesticides is hence being monitored worldwide. For fast, easy, yet sensitive identification, surface-enhanced Raman spectroscopy (SERS) is a powerful tool. In this study, a method is introduced that may be amended to in-field detection of pesticides. Gold and silver nanoparticles were synthesized, size-tailored, and characterized. The herbicide paraquat and the fungicide thiram served as model compounds. The preparation yielded reproducible SERS spectra. Using quantum chemical computation, Raman and SERS spectra were calculated and analyzed. The interpretation of vibrational modes in combination with SERS enhancement and attenuation allowed us to identify compound-specific bands. The assignment was interpreted in terms of the orientation of paraquat and thiram on the gold and silver nanoparticle surfaces. Paraquat preferred a co-planar arrangement parallel to the gold nanoparticle surface and a head-on orientation on the silver nanoparticle. For thiram, breaking of the disulfide bond was recognized, such that interaction with the surface occurred via the sulfur atoms. Successful detection of the pesticides after recollection from vegetable leaves demonstrated the method's applicability for pesticide identification.

Ameliorative effect of Nyctanthes arbor-tristis L. by suppression of pentylenetetrazole-induced kindling in mice: An insight from EEG, neurobehavioral and in-silico studies

Epilepsy is an abiding condition associated with recurrent seizure attacks along with associated neurological and psychological emanation owing to disparity of excitatory and inhibitory neurotransmission. The current study encompasses the assessment of the Nyctanthes arbor-tristis L. methanolic extract (Na.Cr) in the management of convulsive state and concomitant conditions owing to epilepsy. The latency of seizure incidence was assessed using pentylenetetrazol (PTZ) kindling models along with EEG in Na.Cr pretreated mice, trailed by behavior assessment (anxiety and memory), biochemical assay, histopathological alterations, chemical profiling through GCMS, and molecular docking. The chronic assessment of PTZ-induced kindled mice depicted salvation in a dose-related pattern and outcomes were noticeable with extract at 400 mg/kg. The extract at 400 mg/kg defends the progress of kindling seizures and associated EEG. Co-morbid conditions in mice emanating owing to epileptic outbreaks were validated by behavioral testing and the outcome depicted a noticeable defense related to anxiety (P<0.001) and cognitive deficit (P<0.001) at 400 mg/kg. The isolated brains were evaluated for oxidative stress and the outcome demonstrated a noticeable effect in a dose-dependent pattern. Treatment with Na.Cr. also preserved the brain from PTZ induced neuronal damage as indicated by histopathological analysis. Furthermore, the GCMS outcome predicted 28 compounds abundantly found in the plant. The results congregated in the current experiments deliver valued evidence about the defensive response apportioned by Na.Cr which might be due to decline in oxidative stress, AChE level, and GABAergic modulation. These activities may contribute to fundamental pharmacology and elucidate some mechanisms behind the activities of Nyctanthes arbor-tristis.

Eucalyptus globulus leaf-isolated isorhapontin serves as a natural insecticide via acetylcholinesterase inhibition

Acetylcholinesterase (AChE) inhibitors cause insect death by preventing the hydrolysis of the neurotransmitter acetylcholine, which overstimulates the nervous system. In this study, isorhapontin, isolated from E. globulus leaves, was evaluated as a natural insecticide with AChE inhibition at 12.5 μM. Using kinetic analyses, we found that isorhapontin acted as a competitive inhibitor that binds to the active site of AChE. The inhibition constant (Ki) was 6.1 μM. Furthermore, isorhapontin and resveratrol, which have basic skeletons, were predicted to bind to the active site of AChE via molecular docking. A comparison of the hydrogen bonding between the two stilbenes revealed characteristic differences in their interactions with amino acids. In isorhapontin, Trp83, Gly149, Tyr162, Tyr324, and Tyr370 interacted with the sugar moiety. These results suggest that with further development, isorhapontin can be used as an insecticide alternative.

Determination of carboxylesterase by fluorescence probe to guide detection of carbamate pesticide

A carboxylesterase fluorescent probe (Probe 1) was developed for determination of carboxylesterase to guide detection of carbamate pesticide. The probe uses benzothiazole as fluorescence group and phenyldimethyl carbamate as recognition group. The solution of the fluorescent probe gradually changes from light blue to dark blue as the concentration of carbamate pesticides increases. The concentration of carbamate pesticides can be quickly calculated according to the colour of the probe solution through Get Color software on a smartphone. It showed that Probe 1 can be used as a rapid detection tool to achieve rapid detection of carbamate pesticides in juice samples without professional personnel and equipment. Furthermore, the probe has been successfully used to detect carbamate pesticides in fruit juice and vegetable juice.

Organophosphorus and carbamate pesticides: Molecular toxicology and laboratory testing

Population and food requirements are increasing daily throughout the world. To fulfil these requirements application of pesticides is also increasing. Organophosphorous (OP) and Organocarbamate (OC) compounds are widely used pesticides. These pesticides are used for suicidal purposes too. Both inhibit Acetylcholinesterase (AChE) and cholinergic symptoms are mainly used for the diagnosis of pesticide poisoning. Although the symptoms of the intoxication of OP and OC are similar, recent research has described different targets for OP and OC pesticides. Researchers believe the distinction of OP/OC poisoning will be beneficial for the management of pesticide exposure. OP compounds produce adducts with several proteins. There is a new generation of OP compounds like glyphosate that do not inhibit AChE. Therefore, it's high time to develop biomarkers that can distinguish OP poisoning from OC poisoning.

Green magnetic snail shell hydroxyapatite sorbent for reliable solid-phase extraction of pesticides from water samples

To address sustainability issues, the green synthesis of nanomaterials has recently received considerable attention. This article addresses a novel and cost-effective adsorbent for the extraction of eight phenyl-N-methylcarbamate insecticides from water samples. We first synthesized a magnetite/hydroxyapatite nanocomposite using snail shell powder via an environmental friendly approach. The morphology and physicochemical properties of magnetic hydroxyapatite were characterized by Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. Magnetic extraction parameters were optimized using a Doehlert matrix. Under optimum conditions, the magnetic extraction coupled with a LC-MS method shows good linearity with R2 ≥ 0.9982, suitable intra- and interday precision, and limits of detection and quantification in the range of 0.052-0.093 μg/L and 0.11-0.31 μg/L, respectively. Satisfactory relative recoveries of all carbamates were achieved from fortified water samples in the range of 93.89-101.01%.

Smartphone-assisted detection of monocrotophos pesticide using a portable nano-enabled chromagrid-lightbox system towards point-of-care application

With the aim of monocrotophos pesticides detection in environmental and food samples at point-of-care (PoC) application, this research, for the first time, explores silica alcogel as an immobilization matrix to support the development of in-house customized nano-enabled "chromagrid-lighbox" as a sensing system. This system is fabricated using laboratory waste materials and demonstrates the detection of highly hazardous monocrotophos pesticide using a smartphone. Nano-enabled chromagrid is a chip-like assembly filled with silica alcogel -a nanomaterial (hence the name "nano-enabled" chromagrid), and "chromogenic reagents" which is required for the enzymatic detection of monocrotophos. Lightbox is the imaging station fabricated to provide constant lighting conditions to the chromagrid to capture accurate colorimetric data. The silica alcogel used in this system was synthesized from Tetraethyl orthosilicate (TEOS) via a sol-gel method and characterized using advanced analytical techniques. Further, three chromagrid assays were developed for the optical detection of monocrotophos with a low detection limit (LOD) at 0.421 ng ml^-1 (by α-NAc chromagrid assay), 0.493 ng ml^-1 (by DTNB chromagrid assay) and 0.811 ng ml^-1 (by IDA chromagrid assay). The developed novel PoC chromagrid-lightbox system is capable of on-site detection of monocrotophos in environmental as well as food samples. This system is able to be manufacture prudently using recyclable waste plastic. Overall, such developed eco-friendly PoC testing system will surely manage rapid detection of monocrotophos pesticide needed for environmental and sustainable agricultural management.

Two Fe(III)/Eu(III) Salophen complex-based optical sensors for determination of organophosphorus pesticide monocrotophos

Monocrotophos (MP), an organophosphorus pesticide, poses a serious threat to human health, so a rapid and simple technique is needed to detect it. In this study, two novel optical sensors for MP detection were created using the Fe(III) Salophen complex and Eu(III) Salophen complex, respectively. One sensor is an Fe(III) Salophen complex (I-N-Sal), which can bind MP selectively and form a supramolecule, resulting in a strong resonance light scattering (RLS) signal at 300 nm. Under the optimum conditions, the detection limit was 30 nM, the linear range was 0.1-1.1 μM, the correlation coefficient R² = 0.9919, and the recovery rate range was 97.0-103.1%. Interaction properties between the sensor I-N-Sal and MP and the RLS mechanism were investigated using density functional theory (DFT). And another sensor is based on the Eu(III) Salophen complex and 5-aminofluorescein derivatives. The Eu(III) Salophen complex was immobilized on the surface of amino-silica gel (Sigel-NH₂) particles as the solid phase receptor (ESS) of MP and 5-aminofluorescein derivatives as the fluorescent (FL)-labeled receptor (N-5-AF) of MP, which can selectively bind the MP and form a sandwich-type supramolecule. Under the optimum conditions, the detection limit was 0.4 μM, the linear range was 1.3-7.0 μM, the correlation coefficient R² = 0.9983, and the recovery rate range was 96.6-101.1%. Interaction properties between the sensor and MP were investigated by UV-vis, FT-IR, and XRD. Both sensors were successfully applied to the determination of MP content in tap water and camellia.

Structural and Optical Properties of Graphene Quantum Dots-Polyvinyl Alcohol Composite Thin Film and Its Potential in Plasmonic Sensing of Carbaryl

In this study, graphene quantum dots (GQDs) and polyvinyl alcohol (PVA) composite was prepared and then coated on the surface of gold thin film via the spin coating technique. Subsequently, Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and ultraviolet-visible spectroscopy (UV-Vis) were adopted to understand the structure, surface morphology, and optical properties of the prepared samples. The FT-IR spectral analysis revealed important bands, such as O-H stretching, C=O stretching, C-H stretching, and O=C=O stretching vibrations. The surface roughness of the GQDs-PVA composite thin film was found to be increased after exposure to carbaryl. On the other hand, the optical absorbance of the GQDs-PVA thin film was obtained and further analysis was conducted, revealing a band gap E_g value of 4.090 eV. The sensing potential of the thin film was analyzed using surface plasmon resonance (SPR) spectroscopy. The findings demonstrated that the developed sensor's lowest detection limit for carbaryl was 0.001 ppb, which was lower than that previously reported, i.e., 0.007 ppb. Moreover, other sensing performance parameters, such as full width at half maximum, detection accuracy, and signal-to-noise ratio, were also investigated to evaluate the sensor's efficiency.

Ternary water-organic solvent mixtures used for insecticide SPE extraction and analysis with acetylcholinesterase biosensor

Few biosensors are reported for usage in combination with the organic solvent due to their negative impact on the enzymes. The usage of ternary water-organic solvent mixtures in combination with acetylcholinesterase biosensors allows to increase the useable total content of organic solvents with minimum negative effects to a higher content in comparison with a single organic solvent in water. The combination of acetonitrile/ethanol/water has a smaller negative effect on both enzyme activity and inhibition by insecticides in comparison with acetonitrile/methanol/water mixtures. The insecticides were eluted from solid-phase extraction (SPE) columns with a binary mixture of organic solvents acetonitrile/ethanol in 1/3 ratio and subsequently analysed with an acetylcholinesterase biosensor and the optimum total content of organic solvents of 12%. The analytical method allows the analysis of complex samples with improved selectivity and at improved limits of detection for chlorpyrifos-oxon and carbofuran analysis in river waters and soil samples. The usage of mixtures of organic solvents in combination with enzymes is an interesting approach that allows working with a higher total content of organic solvents than each individual solvent.

Evaluation of Structural and Optical Properties of Graphene Oxide-Polyvinyl Alcohol Thin Film and Its Potential for Pesticide Detection Using an Optical Method

In the present work, graphene oxide (GO)–polyvinyl alcohol (PVA) composites thin film has been successfully synthesized and prepared by spin coating techniques. Then, the properties and morphology of the samples were characterized using Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), and atomic force microscopy (AFM). Experimental FTIR results for GO–PVA thin film demonstrated the existence of important functional groups such as -CH2 stretching, C=O stretching, and O–H stretching. Furthermore, UV-Vis analysis indicated that the GO–PVA thin film had the highest absorbance that can be observed at wavelengths ranging from 200 to 500 nm with a band gap of 4.082 eV. The surface morphology of the GO–PVA thin film indicated the thickness increased when in contact with carbaryl. The incorporation of the GO–PVA thin film with an optical method based on the surface plasmon resonance (SPR) phenomenon demonstrated a positive response for the detection of carbaryl pesticide as low as 0.02 ppb. This study has successfully proposed that the GO–PVA thin film has high potential as a polymer nanomaterial-based SPR sensor for pesticide detection.

A critical comparison between an ultra-high-performance liquid chromatography triple quadrupole mass spectrometry (UHPLC-QqQ-MS) method and an enzyme assay for anti-cholinesterase pesticide residue detection in cereal matrices

Analytical method development for the control of pesticide residues occurring in significant dietary foodstuffs is of utmost importance considering their potential impact on consumer health and food market sustainability. Depending on the purpose, either instrumental analysis, mainly chromatographic methods, or screening assays, mostly using biorecognition affinity, are commonly used, featuring different advantages and drawbacks. To practically compare these two different types of analytical strategies, we applied them for the detection of (i) 97 organophosphate (OP) and carbamate (CM) pesticide residues in wheat flour and (ii) carbofuran (a carbamate insecticide) in wheat, rye and maize flour samples. Regarding high-end analysis, an ultra-high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC-QqQ-MS) method was developed and validated achieving low limits of quantification (LOQs, from 0.002 to 0.040 mg kg^-1) and a short chromatographic run (12 min). In terms of bioanalytical methods, a fast (17 min) and cost-efficient (∼0.01€ per sample) acetylcholinesterase (AChE) microplate assay for carbofuran screening was utilized. Importantly, carbofuran was the strongest of the 11 OP and CM tested pesticides achieving a half maximal inhibitory concentration (IC₅₀) of 0.021 μM whilst the assay detectability was at the parts per billion level in all three cereal matrices. Based on the attained results, a critical discussion is presented providing the analytical merits and bottlenecks for each case and a wider outlook related to the application of analytical methods in the food safety control analytical scheme.

A sensitive approach for screening acetylcholinesterase inhibition of water samples using ultra-performance liquid chromatography-tandem mass spectrometry

A sensitive assay was developed to evaluate inhibitory effects of aqueous solution on acetylcholinesterase (AChE) activity via measuring hydrolysis rates of acetylcholine (ACh) based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Upon having identified precursor ions and product ions of the ACh and its hydrolysis products choline (Ch), the separation chromatogram for these two analytes has been established using a 50 mm reverse-phase BEH Shield RP18 column. The total chromatographic separation time is 7 min; limits of detection (LODs) for ACh and Ch are 0.14 µg L^-1 and 0.12 µg L^-1, respectively. A simple method for inactivation of AChE and optimization of operational parameters were then sequentially performed. It was found that adjusting solution pH to 2.5 not only can terminate the enzymatic reaction but also solve band shifting and broadening caused by aqueous matrices in chromatographic separation during UPLC-MS/MS detection. Under conditions of 0.00075 U mL^-1 AChE, initial concentration of ACh at 100 µg L^-1 and 20 min observation time, IC₅₀ values of the proposed assay for chlorpyrifos-oxon, diazoxon, malaoxon, methidathion oxon, omethoate and paraoxon were 3.5 nM, 16.8 nM, 2.4 nM, 6.8 nM, 270 nM and 36.9 nM, respectively. They are 4.5-51.9 times smaller than those reported in a LC-MS based method, and >120 times lower than those obtained by the traditional Ellman method. The results suggested that, the proposed assay significantly increases the sensitivity of commercial AChE. In addition, inhibition efficiencies of three surface waters, a groundwater and four commercial brands of bottled drinking water samples on AChE activity were firstly measured using this UPLC-MS/MS based method. These water samples were proved to have different inhibitory effects on AChE activity, and the inhibition efficiencies dependent on concentrations of dissolved organic carbon (DOC) but are independent of UV absorbance at 254 nm (UV₂₅₄) values. These results indicate that the proposed method has advantages of high sensitivity over all other conventional methods. It may become a promising AChE inhibition assay for assessing toxicity of aqueous solution containing neurotoxicity contaminants such as organophosphorus pesticides (OPPs) at low levels, or used to evaluate potential inhibition effects of natural waters on AChE activity.

ASSURED Point-of-Need Food Safety Screening: A Critical Assessment of Portable Food Analyzers

Standard methods for chemical food safety testing in official laboratories rely largely on liquid or gas chromatography coupled with mass spectrometry. Although these methods are considered the gold standard for quantitative confirmatory analysis, they require sampling, transferring the samples to a central laboratory to be tested by highly trained personnel, and the use of expensive equipment. Therefore, there is an increasing demand for portable and handheld devices to provide rapid, efficient, and on-site screening of food contaminants. Recent technological advancements in the field include smartphone-based, microfluidic chip-based, and paper-based devices integrated with electrochemical and optical biosensing platforms. Furthermore, the potential application of portable mass spectrometers in food testing might bring the confirmatory analysis from the laboratory to the field in the future. Although such systems open new promising possibilities for portable food testing, few of these devices are commercially available. To understand why barriers remain, portable food analyzers reported in the literature over the last ten years were reviewed. To this end, the analytical performance of these devices and the extent they match the World Health Organization benchmark for diagnostic tests, i.e., the Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Deliverable to end-users (ASSURED) criteria, was evaluated critically. A five-star scoring system was used to assess their potential to be implemented as food safety testing systems. The main findings highlight the need for concentrated efforts towards combining the best features of different technologies, to bridge technological gaps and meet commercialization requirements.

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.

Optical Screening Methods for Pesticide Residue Detection in Food Matrices: Advances and Emerging Analytical Trends

Pesticides have been extensively used in agriculture to protect crops and enhance their yields, indicating the need to monitor for their toxic residues in foodstuff. To achieve that, chromatographic methods coupled to mass spectrometry is the common analytical approach, combining low limits of detection, wide linear ranges, and high accuracy. However, these methods are also quite expensive, time-consuming, and require highly skilled personnel, indicating the need to seek for alternatives providing simple, low-cost, rapid, and on-site results. In this study, we critically review the available screening methods for pesticide residues on the basis of optical detection during the period 2016-2020. Optical biosensors are commonly miniaturized analytical platforms introducing the point-of-care (POC) era in the field. Various optical detection principles have been utilized, namely, colorimetry, fluorescence (FL), surface plasmon resonance (SPR), and surface enhanced Raman spectroscopy (SERS). Nanomaterials can significantly enhance optical detection performance and handheld platforms, for example, handheld SERS devices can revolutionize testing. The hyphenation of optical assays to smartphones is also underlined as it enables unprecedented features such as one-click results using smartphone apps or online result communication. All in all, despite being in an early stage facing several challenges, i.e., long sample preparation protocols or interphone variation results, such POC diagnostics pave a new road into the food safety field in which analysis cost will be reduced and a more intensive testing will be achieved.

Rapid Multi-Residue Detection Methods for Pesticides and Veterinary Drugs

The excessive use or abuse of pesticides and veterinary drugs leads to residues in food, which can threaten human health. Therefore, there is an extremely urgent need for multi-analyte analysis techniques for the detection of pesticide and veterinary drug residues, which can be applied as screening techniques for food safety monitoring and detection. Recent developments related to rapid multi-residue detection methods for pesticide and veterinary drug residues are reviewed herein. Methods based on different recognition elements or the inherent characteristics of pesticides and veterinary drugs are described in detail. The preparation and application of three broadly specific recognition elements-antibodies, aptamers, and molecular imprinted polymers-are summarized. Furthermore, enzymatic inhibition-based sensors, near-infrared spectroscopy, and SERS spectroscopy based on the inherent characteristics are also discussed. The aim of this review is to provide a useful reference for the further development of rapid multi-analyte analysis of pesticide and veterinary drug residues.

Smartphone-based optical assays in the food safety field

Smartphone based devices (SBDs) have the potential to revolutionize food safety control by empowering citizens to perform screening tests. To achieve this, it is of paramount importance to understand current research efforts and identify key technology gaps. Therefore, a systematic review of optical SBDs in the food safety sector was performed. An overview of reviewed SBDs is given focusing on performance characteristics as well as image analysis procedures. The state-of-the-art on commercially available SBDs is also provided. This analysis revealed several important technology gaps, the most prominent of which are: (i) the need to reach a consensus regarding optimal image analysis, (ii) the need to assess the effect of measurement variation caused by using different smartphones and (iii) the need to standardize validation procedures to obtain robust data. Addressing these issues will drive the development of SBDs and potentially unlock their massive potential for citizen-based food control.

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Optical smartphone based sensors in the food safety field are systematically reviewed.

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Recommendations on image analysis optimization are given.

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The analytical performance of smartphone based sensors is discussed.

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Available commercial devises are critically compared.