Detection Of Organophosphate Pesticides Research Articles

Synthesis of pyrochlore-type La2Sn2O7@GO for the in-situ profiling of organophosphate pesticides paraoxon ethyl in environmental samples

The detection and monitoring of organophosphate pesticides in environmental samples are of paramount importance due to their potentially harmful effects on human health and ecosystems. In this study, we present the detection of paraoxon ethyl (POE), a widely used organophosphate pesticide, utilizing an electrochemical method. We synthesized graphene oxide-incorporated pyrochlore-type lanthanum stannate (La2Sn2O7@GO) as a sensing material for enhanced detection sensitivity and selectivity. The electrochemical detection of POE was performed using a glassy carbon electrode modified with the synthesized nanocomposite. The modified electrode La2Sn2O7@GO/GCE exhibited a remarkable electrochemical response towards POE, showing a significant reduction potential and an increase in the peak current compared to the bare and other modified electrodes. The proposed electrochemical method showed excellent detection sensitivity and selectivity for POE, with a linear response range of concentrations from 0.01 to 360 μM and a low detection limit (LDL) of 2.73 nM. The sensor also exhibited good stability and reproducibility, making it a promising tool for practical pesticide detection applications. The developed sensor offers a cost-effective, sensitive, and reliable platform for the rapid monitoring of organophosphate pesticides in environmental samples, contributing to the advancement of pesticide detection technologies and environmental protection efforts.

(Invited) F-ALDH, a New Catalyst for Enzyme and Aptamer- Based Electrochemical Biosensors

The selectivity, affinity and catalytic activity are key characteristics which recommend enzymes as components of biosensors, whether for use as main recognition element or for signal amplification. Additionally, the enzyme inhibition by various molecules can be exploited for analytical purposes. In the search for new enzymes with good stability and catalytic properties, a recombinant psychrophilic aldehyde dehydrogenase from the Antarctic Flavobacterium PL002 was recently characterized and shown to have potential in biosensing [1-5].The enzyme is active in a wide temperature range up to 60º C and has high catalytic activity [1,2]. It accepts various aldehydes substrates with Michaelis Menten constants of e.g., Km = 0. 137 ± 0.016 mmol L−1 for benzaldehyde. The enzyme may use both nicotinamide adenin dinucleotide (NAD+) and nicotinamide adenin dinucleotide phosphate (NADP+) as cofactors and has higher affinity for NAD+ ( Km=0.033mmol L−1 and 0.431 mmol L−1 for NAD+ and NADP+, respectively [2]). As for other aldehyde dehydrogenases, the enzyme is inhibited by heavy metals and dithiocarbamate fungicides [2,3].To explore its potential as recognition element in biosensors, enzymatic tests and electrochemical biosensors exploiting the catalytic activity of F-ALDH or its inhibition were first developed [4,5]. In biosensors, the enzyme was immobilized by cross linking in a matrix of bovine serum albumin [5] or by nickel-histidine affinity. Enzymatic inks with a stability of several months at 4º C were obtained by immobilizing the enzyme on magnetic particles functionalized with a complex of nickel-nitrilotriacetic acid (Ni-NTA) followed by mixing with different additives. Practical applications for the specific detection of (i) benzaldehyde in a pharmaceutical ingredient [5] and (ii) acetaldehyde in wines were demonstrated. In wines, acetaldehyde is present in a free form or bound to sulphur dioxide or phenolic compounds. Both free and bound acetaldehyde are relevant for wine quality and its evolution. The F-ALDH enzyme enables testing of both forms in cellar like conditions. Moreover, the detection of free acetaldehyde serves as example for aldehydes detection in vapor phase, opening the way for other similar applications.A separate line of research explored the potential of F-ALDH for the quantitative determination of enzyme’s inhibitors. Spectrophotometry measurements emphasized a 15% reduction of enzyme’s activity in the presence of either 28 ppb thiram or 0.5 ppb mercury chloride. The solution advanced for overcoming the selectivity issues in the detection of thiram is to couple the electrochemical biosensor measuring the F-ALDH inhibition with SERS measurements of the dithiocarbamate fungicide [6].Finally, the F-ALDH enzyme may serve as label in electrochemical aptasensors. The enzyme was attached to an aptamer for lysozyme via Ni-histidine affinity and preserved good catalytic activity for the conversion of acetaldehyde. Preliminary studies were focused on investigating the affinity of the enzyme-labeled aptamer for lysozyme in relation to the linker length.Based on the demonstrated catalytic activity of the enzyme and its preservation upon immobilization on different supports or by linking to an aptamer, various sensing configurations can be envisaged that will exploit the potential of the new enzyme. Acknowledgements: This work was financially supported by the UEFISCDI projects ERANET-M-ENZ4IFACES, contract 166/01.05.2020 (for AV, GNP and CP) and PN-III-P4-ID-PCE-2020-2297 E-MAP, contract 84/9.02.2021 (for RMB and AF). References Necula-Petrareanu G, Lavin P, Vasilescu A, Purcarea C (2018) Antarctic Flavobacterium aldehyde dehydrogenase – a cold adapted catalyst for biosensing. J Biotechnol 280:S18. https://doi. org/10.1016/j.jbiotec.2018.06.054Necula-Petrareanu, G.; Lavin, P.; Paun, V.I.; Gheorghita, G.R.; Vasilescu, A.; Purcarea, C. Highly stable cold-active aldehyde dehydrogenase from the marine Antarctic Flavobacterium sp. PL002. Fermentation. 2022 8(1):7-24 https:// doi.org/10.3390/fermentation8010007Vasilescu A, Titoiu A.M, Purcarea C, Necula Petrareanu G, Method for determining thiram fungicide based on enzymatic inhibition and electrochemical sensor, Romanian patent application, OSIM RO133890A2 /13.08.2018Titoiu AM, Lapauw M, Necula-Petrareanu G, Purcarea C, FanjulBolado P, Marty J-L, Vasilescu A (2018) Carbon nanofiber and Meldola Blue based electrochemical sensor for NADH: application to the detection of benzaldehyde. Electroanalysis 30(11):2676– 2688. https://doi.org/10.1002/elan.201800472Titoiu, A. M., Necula-Petrareanu, G., Visinescu, D., Dinca, V., Bonciu, A., Mihailescu, C. N., ... Vasilescu, A. (2020). Flow injection enzymatic biosensor for aldehydes based on a Meldola Blue-Ni complex electrochemical mediator. Microchimica Acta, 187(10).doi:10.1007/s00604-020-04477-3Ibáñez D, González-García MB, Hernández-Santos D, Fanjul-Bolado P. Detection of dithiocarbamate, chloronicotinyl and organophosphate pesticides by electrochemical activation of SERS features of screen-printed electrodes. Spectrochim Acta A Mol Biomol Spectrosc. 2021 Mar 5;248:119174. doi: 10.1016/j.saa.2020.119174

Core-shell ZnO@CoO nitrogen doped nano-composites as highly sensitive electrochemical sensor for organophosphate pesticides detection

Core-shell ZIF-8@ZIF-67 was synthesized by growing a cobalt-based ZIF-67 on a ZIF-8 seed particle. Herein, through selective etching of the ZIF-8@ZIF-67 core and subsequent direct carbonization, core-shell hollow ZnO@CoO nitrogen-doped nanoporous carbon (HZnO@CoO-NPC) nanocomposites were prepared. HZnO@CoO–NPCs possessed a high nitrogen content, large surface area, high degree of graphitization and excellent electrical conductivity, all of which were attributed to successfully integrating the unique advantages of ZIF-8 and ZIF-67. HZnO@CoO–NPCs were used to assemble acetylcholinesterase (AChE) biosensors for organophosphorus pesticides (OPs) detection. The low detection limit of 2.74 × 10−13 M for chlorpyrifos and 7.6 × 10−15 M for parathion-methyl demonstrated the superior sensing performance. The results showed that the electrochemical biosensor constructed by HZnO@CoO-NPC provided a sensitive and efficient electrochemical strategy for OPs detection.

CdS/g-C3N4/Sm-BDC MOF nanocomposite modified glassy carbon electrodes as a highly sensitive electrochemical sensor for malathion

Malathion is an organophosphate pesticide widely used in agriculture, whose elimination is highly demanded by society. This work faces this challenge by the development of a novel electrochemical sensor via modifying a glassy carbon electrode (GCE) with sustainable Sm-BDC MOFs and their corresponding novel binary and ternary composites combined with CdS and g-C3N4 for the detection of malathion. Different characterization techniques indicate the successful synthesis of desired composite materials, with notable interaction between the individual components. CdS-Sm-BDC-g-C3N4-5 wt% modified electrode exhibited higher peak current than the bare GCE, with excellent electrocatalytic ability to oxidize malathion, due to its higher conductivity, catalytic effect and synergistic effects between CdS, g-C3N4 and Sm-BDC. Under optimized condition, differential pulse voltammograms (DPV) demonstrate that the oxidation peak current was proportional to its concentration in the range of 3.0·10−8–15.0·10−8 M (R2 = 0.996), with high sensitivity (25 μAμM−1) and low detection limit (7.4·10−9 M or 7.4 μmM). In addition, the modified electrode affirms good stability and reproducibility, making it simple, cost effective with high sensitivity and selectivity. The results confirmed that making a composite is a key strategy for improving the physicochemical properties of MOFs and that modifying electrode surfaces with novel composites can enhance the detection of organophosphate pesticide.

Competitive Assay for the Ultrasensitive Detection of Organophosphate Pesticides Based on a Fiber-Optic Particle Plasmon Resonance Biosensor and an Acetylcholinesterase Binding Peptide.

An acetylcholinesterase (AChE) binding-based biosensor was developed for the ultrasensitive detection of organophosphate (OP) pesticides. The biosensor integrates the technique based on fiber-optic particle plasmon resonance detection and a synthetic AChE binding peptide conjugated with gold nanoparticles on the optical fiber surface via an AChE competitive binding assay. The OP pesticides present in the solution hinder the binding of AChE to the peptide on the biosensor by competing for the binding sites present in AChE. The limit of detection obtained for parathion using this method was observed to be 0.66 ppt (2.3 pM). This method shows a wide linear dynamic range of 6 orders. Furthermore, the use of the AChE binding peptide in the biosensor can better discriminate OPs against carbamates by using only a single biosensor. The practical application of this method was tested using spiked samples, which yielded good recovery and reproducibility. The spiked sample required minimal pretreatment before analysis; hence, this biosensor may also be used in the field.

An Amperometric Acetylcholinesterase Biosensor Based on Polyvinyl‐Alcohol‐Capped Silver Nanoparticles (AgNPs@PVA) for Detection of Organophosphate Pesticides

AbstractIn the present study polyvinyl alcohol (PVA) capped AgNPs (AgNPs@PVA) were used as nanocarrier for fabrication of an acetylcholinesterase (AChE) biosensor for organophosphate (OP) pesticide detection. AChE enzyme was immobilized via glutaraldehyde on drop casted AgNPs@PVA layer on glassy carbon electrode (GCE) for fabrication of the electrochemical biosensor. Through differential pulse voltammetry (DPV) the biosensor measured peak current at 0.6 V generated by AChE mediated hydrolysis of acetylthiocholine (ATCl) to thiocholine and its subsequent oxidation to dimer. By hindering AChE hydrolysis activity of the sensor probe by a model OP pesticide, malathion, the pesticide biosensor was developed as the inhibition effect was found to be proportional to the concentration of malathion. The fabricated biosensor exhibits linearity at range of 0.01 to 1 ng/mL of malathion at optimal conditions with detection limit (LOD) of 2.6 pg/mL. The fabricated AChE biosensor showed good selectivity for OP pesticides and exhibited good efficiency in real sample analysis.

Nanozymes paper−based analytical device for the detection of organophosphate pesticides in fruits and vegetables

In this work, copper oxide nanoparticles (CuONPs) nanozymes paper-based analytical device was designed for the rapid detection of organophosphate pesticides in fruits and vegetables. The paper-based analytical device was modified with silica oxide nanoparticles to enhance the assay sensitivity. CuO nanozymes displayed peroxidase-like activity and catalyzed the oxidation of o-dianisidine in the presence of H2O2 from the hydrolysis of acetylthiocholine. This results in the formation of a brown−colored product. In the presence of organophosphate pesticides such as malathion, acetylcholinesterase activity was inhibited, resulting in reduced color intensity production, and which was measured with a smartphone. The proposed nanozymes paper-based analytical device exhibited a good linear detection range (0.1–5 mg L−1), a low detection limit of 0.08 mg L−1, and the analysis time was only about 10 min for malathion detection under optimal conditions. Moreover, the CuONPs had excellent catalytic activity and higher stability than peroxidase. Finally, this device can be applied to detect organophosphate pesticides in fruits and vegetables with rapidity, accuracy, portability, and ease of handling in the field.

Near-infrared-excitable acetylcholinesterase-activated fluorescent probe for sensitive and anti-interference detection of pesticides in colored food

The development of a common and anti-interference acetylcholinesterase (AChE) inhibition assay for plant-originated food samples has been of great challenge because of the prevalent and strong signal interferences from natural pigments. Plant pigments normally exhibit non-negligible absorbance in the UV-visible region. As a result, the signals of a typical near-infrared (NIR) fluorescent probe could be disturbed through primary inner filter effect if it is excited by UV-visible light during plant sample analysis. In this work, an NIR-excitable AChE-activated fluorescent probe was biomimetically designed and synthesized. And the NIR-excitation strategy was utilized for the anti-interference detection of organophosphate and carbamate pesticides in colored samples with this probe. Sensitive and rapid response to AChE and pesticides was achieved due to the high affinity of the biomimetic recognition unit in the probe. The limits of detection for four representative pesticides including dichlorvos, carbofuran, chlorpyrifos and methamidophos reached 0.0186 μg/L, 2.20 μg/L, 12.3 μg/L and 13.6 μg/L, respectively. Most importantly, fluorescent response to pesticide contents could be accurately measured in the coexistence of different plant pigments by this probe, and the measured results showed completely irrelevance to the plant pigments and their colors. Taking advantage of such probe, the new developed AChE inhibition assay showed good sensitivity and anti-interference ability in the detection of organophosphate and carbamate pesticides in real samples.

In-field deployable and facile nanosensor for the detection of pesticides residues

Local air and water should be first priority to understand the environment of any area. Different categories of contaminants behave like bottleneck situation in collection and analysis of data about abiotic factors for the understanding and resolving the environmental issues. In digital age the emerging nano technology enroll its role to meet the needs of hour. Due to increase in pesticides residues, the global health threats are on bloom because it inhibits the functionality of acetylcholinesterase (AChE) enzyme. Smart nanotechnology based system can tackle this issue and sense the pesticides residues in environment and vegetables as well. Here Au@ZnWO4 composite is reported, for accurate detection of pesticides residues in biological food and environmental samples. The fabricated unique nanocomposite was characterized by SEM, FTIR, XRD and EDX. The characterized material used for the electrochemical detection of organophosphate pesticide (chlorpyrifos), with 1 pM LoD at a signal to noise ratio of 3. The main concern of study is to help out in disease prevention, food safety and ecosystem protection.

Metal Coordination-Driven Supramolecular Nanozyme as an Effective Colorimetric Biosensor for Neurotransmitters and Organophosphorus Pesticides.

Analytical methods for detecting neurotransmitters (NTs) and organophosphorus (OP) pesticides with high sensitivity are vitally necessary for the rapid identification of physical, mental, and neurological illnesses, as well as to ensure food safety and safeguard ecosystems. In this work, we developed a supramolecular self-assembled system (SupraZyme) that exhibits multi-enzymatic activity. SupraZyme possesses the ability to show both oxidase and peroxidase-like activity, which has been employed for biosensing. The peroxidase-like activity was used for the detection of catecholamine NTs, epinephrine (EP), and norepinephrine (NE) with a detection limit of 6.3 µM and 1.8 µM, respectively, while the oxidase-like activity was utilized for the detection of organophosphate pesticides. The detection strategy for OP chemicals was based on the inhibition of acetylcholine esterase (AChE) activity: a key enzyme that is responsible for the hydrolysis of acetylthiocholine (ATCh). The corresponding limit of detection of paraoxon-methyl (POM) and methamidophos (MAP) was measured to be 0.48 ppb and 15.8 ppb, respectively. Overall, we report an efficient supramolecular system with multiple enzyme-like activities that provide a versatile toolbox for the construction of sensing platforms for the colorimetric point-of-care detection of both NTs and OP pesticides.

Competitive fluorescent immunosensor based on catalytic hairpin self-assembly for multiresidue detection of organophosphate pesticides in agricultural products

Simple and rapid multiresidue trace detection of organophosphate pesticides (OPs) is extremely important for various reasons, including food safety, environmental monitoring, and national health. Here, a catalytic hairpin self-assembly (CHA)-based competitive fluorescent immunosensor was developed to detect OPs in agricultural products, involving enabled dual signal amplification followed by a CHA reaction. The developed method could detect 0.01–50 ng/mL triazophos, parathion, and chlorpyrifos, with limits of detection (LODs) of 0.012, 0.0057, and 0.0074 ng/mL, respectively. The spiked recoveries of samples measured using this assay ranged from 82.8 % to 110.6 %, with CV values ranging between 5.5 % and 18.5 %. This finding suggests that the CHA-based competitive fluorescent immunosensor is a reliable and accurate method for detecting OPs in agricultural products. The results correlated well with those obtained from the liquid chromatography-tandem mass spectrometry (LC–MS/MS) method, indicating that the CHA-based biosensor is able to accurately detect OPs and can be used as a reliable alternative to the LC–MS/MS method. Additionally, the CHA-based biosensor is simpler and faster than LC–MS/MS, which makes it a more practical and cost-effective option for the detection of OPs. In summary, the CHA-based competitive fluorescent immunosensor can be considered a promising approach for trace analysis and multiresidue determination of pesticides, which can open up new horizons in the fields of food safety, environmental monitoring, and national health.

Retraction Note: Attomolar SERS detection of organophosphorous pesticides using silver mirror-like micro-pyramids as active substrate.

Retraction Note: Attomolar SERS detection of organophosphorous pesticides using silver mirror-like micro-pyramids as active substrate.

Specific interaction through functional group and molecularly imprint-based QCM-D sensor for detection of phorate and malathion

The molecularly imprinted polymer (MIP) is used to detect organophosphate pesticides phorate and malathion. The sol-gel technique is used to synthesize the MIP using 3- (trimethoxysilyl) propyl methacrylate (TMSPMA) as a functional monomer. We have coated the silica crystal of the quartz crystal microbalance (QCM) sensor with the synthesized MIP to detect the pesticides. The detection is based on the specific high adsorption for template molecule from solution. The real-time adsorption studies of the pesticides on MIP surfaces show their significant binding with the respective pesticide used as a template molecule. However, the adsorbed mass of the pesticides on the MIP of the pesticides is verified by using the concentration depletion method. The concentration of the pesticides was measured using high-performance liquid chromatography. The adsorption data matches well with the data obtained using QCM. The specificity and repeatability experiments indicate that the developed MIP is highly selective for the studied pesticides. The obtained selectivity of malathion and phorate are 9.4 and 6.8, respectively, and indicative of the goodness of the developed material.

Use of biosensors for rapid and sensitive detection of pesticides in food samples for food safety chemical risk assessment.

The utility of pesticides in the agricultural field is unquestionable, but at the same time pesticide use presents serious hazards to the environment and the human health. For that reason, detection of pesticides and their biotransformation products in food is of utmost importance. According to previous studies, esterase-based biosensors have been proposed as a viable and efficient solution for the detection of organophosphate pesticides. In this project, a double mutant of the thermostable esterase-2 (EST2) from Alicyclobacillus acidocaldarius was studied as a potential biosensor, for its ability to detect residual amounts of pesticides. Initial characterisation of the enzyme was performed, that included determination of optimal pH, thermophilicity, as well as kinetic analysis. Subsequently, the enzyme was studied by enzymatic activity assays with and without the presence of various organophosphate compounds. The effect of the organophosphates on the enzymatic activity was measured and complete inhibition of the enzyme was observed after incubation with paraoxon. These experiments were followed by an additional method involving labelling of the enzyme with a fluorescent probe. In this case, the effect of different pesticides on the EST2 enzyme was monitored by measuring the fluorescence quenching upon addition to the enzyme. Fourteen compounds were screened with this method and significant fluorescence quenching was observed in the presence of paraoxon and methyl-paraoxon when used in equimolar amounts with the enzyme in the range of nanomolar. This biosensor has been also used to test the presence of pesticides in real food samples, like fruits and juices. This research represents a starting point to develop effective fluorescence-based biosensors aiming at the screening of mutants with different pesticide selectivity profiles. The use of this enzyme-based biosensor can have applications in the field of food traceability as well as environmental monitoring, to control the presence of toxic chemicals, in particular organophosphate pesticides.

Portable hydrogel test kit integrated dual-emission coordination polymer nanocomposite for on-site detection of organophosphate pesticides

It is of great significance to on-site detection of organophosphate pesticides (OPs) for pollution monitoring and poisoning estimation. Herein, we developed a portable hydrogel test kit for on-site detection of OPs, which is based on the integration of agarose hydrogel with dual-emission coordination polymers (CPs) nanocomposite comprised of Ru(bpy)32+ and zinc (II)-based CPs (ZnCPs) loaded with thioflavin T (ThT). Different from Ru(bpy)32+ with stable fluorescence in acidic environment, ThT@ZnCPs is highly sensitive to H+, which destroys the structure of ZnCPs as a host and quenches ThT@ZnCPs fluorescence. The distinct fluorescence behaviors of Ru(bpy)32+ and ThT@ZnCPs in acidic environment enable the hydrogel test kit to exhibit ratiometric fluorescence responses to acetylcholinesterase (AChE), which hydrolyzes acetylcholine to acetic acid and provides H+. On this basis, combining the inhibition effect of OPs to AChE activity, a ratiometric fluorescence method for OPs detection was established with the hydrogel test kit, and satisfactory results have been achieved in buffered aqueous solutions and apple juice samples. Attractively, by employing smartphone as a signal readout, on-site quantitation of OPs was accomplished with the features of easy to use, portability and low cost, demonstrating a great promising for point-of-care testing in food safety monitoring.

Kinetic Studies of Immobilized Wheat‐Based Alpha‐Naphthyl Acetate Esterase in the Detection of Organophosphate Pesticides

AbstractOrganophosphate pesticides could inhibit the activity of alpha‐naphthyl acetate esterase (ANAE), which could be the fundamental for biosensor applications. k‐carrageenan was used for immobilization of ANAE extracted from wheat‐based sources. The activity of ANAE was assessed for optimum activity at a range of temperature and pH. Enzyme kinetic studies were performed using Michaelis‐Menten kinetic parameters from Lineweaver‐Burk, Langmuir, and Eddie‐Hofstee. The optimization studies showed that the relative activity of the enzyme remained high, even above 50 °C. kd obtained was very low, which indicates the high sensitivity of ANAE towards pesticides. The kinetic reaction of ANAE showed the promising application of biosensors in the detection of pesticide.

Tailored architecture of molybdenum carbide/iron oxide micro flowers with graphitic carbon nitride: An electrochemical platform for nano-level detection of organophosphate pesticide in food samples

Herein we report the ternary hybrid nanocomposite of iron oxide @ molybdenum carbide micro flowers decorated graphitic-carbon nitride (Fe3O4@MoC MFs/g-CN), as a catalyst for the detection of organophosphorus pesticide, parathion (PAT), for the first time. The growth of hierarchical nanostructure from the core level will facilitate easy diffusion of analyte and interact more effectively with the reactive catalytic sites. Thus, Fe3O4 NFs architecture was hydrothermally grown over MoC flakes from the core level, which further hybridized with g-CN to ensure electrical conductivity and mechanical stability. Experimental results demonstrate that Fe3O4@MoC MFs/g-CN/GCE has superior catalytic efficacy for PAT reduction. At optimum conditions, the proposed sensor exhibits a low detection limit (7.8 nM), high sensitivity, and wide linear range (0.5–600 µM) toward PAT detection. The satisfactory test results of the food samples indicate that the Fe3O4@MoC MFs/g-CN/GCE sensor can be used as an excellent candidate for real-time PAT detection.

A highly sensitive bio-barcode immunoassay for multi-residue detection of organophosphate pesticides based on fluorescence anti-quenching

Balancing the risks and benefits of organophosphate pesticides (OPs) on human and environmental health relies partly on their accurate measurement. A highly sensitive fluorescence anti-quenching multi-residue bio-barcode immunoassay was developed to detect OPs (triazophos, parathion, and chlorpyrifos) in apples, turnips, cabbages, and rice. Gold nanoparticles were functionalized with monoclonal antibodies against the tested OPs. DNA oligonucleotides were complementarily hybridized with an RNA fluorescent label for signal amplification. The detection signals were generated by DNA-RNA hybridization and ribonuclease H dissociation of the fluorophore. The resulting fluorescence signal enables multiplexed quantification of triazophos, parathion, and chlorpyrifos residues over the concentration range of 0.01–25, 0.01–50, and 0.1–50 ng/mL with limits of detection of 0.014, 0.011, and 0.126 ng/mL, respectively. The mean recovery ranged between 80.3% and 110.8% with relative standard deviations of 7.3%–17.6%, which correlate well with results obtained by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The proposed bio-barcode immunoassay is stable, reproducible and reliable, and is able to detect low residual levels of multi-residue OPs in agricultural products.

Monitoring of pesticide amount in water and drinkable food by a fluorescence-based biosensor.

The identification of pollutants is crucial to protect water resources and ensure food safety. The available analytical methodologies allow reliable detection of organic pollutants such as pesticides; however, there is the need for faster, direct and continuous methodologies for real‐time monitoring of pesticides. Fluorescent‐based biosensors have been recently proposed as a valid alternative due to their advantage of being easy, cheap and specific. In this context, the aim of the present EU‐FORA fellowship programme was to develop and apply a fluorescence‐based biosensing device for the detection of organophosphate (OP) pesticides in water samples and drinkable food. The study was addressed using a mutant of the thermostable esterase‐2 from Alicyclobacillus acidocaldarius (EST2‐S35C) as a bioreceptor for OP pesticides. The use of EST2 involves some significant advantages including specificity and affinity towards OPs, and high stability over time in a different range of temperatures and pH. The protein was labelled to the fluorescent probe IAEDANS and fluorescence measurements of quenching in solution and in immobilised form were performed. The results showed good stability and sensitivity, reaching low limits of detection and quantification and a constant signal intensity over time. The addition of paraoxon quenched the fluorescence of the complex, reaching a plateau at 100 pmol paraoxon. The decrease of enzymatic activity of EST2‐S35C‐IAEDANS in the presence of paraoxon correlated the inhibition of the labelled enzyme with the decrease in fluorescence. The results from the application of the biosensor with real samples showed a decrease in fluorescence in surface water samples, contaminated by OPs. The use of the developed fluorescence‐based biosensor demonstrated its applicability for real samples monitoring and could ensure the production of large amounts of data in a short period of time which can be used to address environmental and food safety risk assessment.

Water-soluble non-conjugated polymer dots with strong green fluorescence for sensitive detection of organophosphate pesticides

Water-soluble non-conjugated polymer dots (PDs) have been synthesized using hyperbranched polyethyleneimine (PEI) and dihydroxybenzaldehyde (DHB) for the first time via the Schiff base reaction at room temperature. The yielded non-conjugated PDs of PEI-DHB could display the well-defined spheric structure and good water solubility. In contrast to the common PDs otherwise showing blue emission, the PEI-DHB PDs could give out strong green fluorescence in aqueous media. Especially, the fluorescence of the PEI-DHB PDs could be specifically quenched by MnO2 nanosheets through the inner filter effects and further restored by the thiocholine that could reduce MnO2 nanosheets into Mn2+. Herein, thiocholine could be produced in hydrolysis reaction of acetylthiocholine catalyzed by the acetylcholinesterase (AChE), of which the catalytic activity could be irreversibly inhibitted by the introduction of organophosphates. A highly selective fluorimetric method was thereby been developed for the detection of organophosphorus pesticides using dimethyl-dichloro-vinyl phosphate as a model. The linear concentrations ranges from 0.050 to 2.5 μM. Importantly, the non-conjugated PDs probes with strong green fluorescence and high water solubility may promise the extensive applications in the environmental, food, and clinical analysis fields.