Towards solving the reproducibility crisis in surface-enhanced Raman spectroscopy-based pesticide detection.

Growing concerns about pesticide residues in agriculture are pushing the scientific community to develop innovative and efficient methods for detecting these substances at low concentrations down to the molecular level. In this context, surface-enhanced Raman spectroscopy (SERS) is a powerful analytical method that has so far already undergone some validation for its effectiveness in pesticide detection. However, despite its great potential, SERS faces significant difficulties obtaining reproducible and accurate pesticide spectra, particularly for some of the most widely used pesticides, such as malathion, chlorpyrifos, and imidacloprid. Those inconsistencies can be attributed to several factors, such as interactions between pesticides and SERS substrates and the variety of substrates and solvents used. In addition, differences in the equipment used to obtain SERS spectra and the lack of standards for control experiments further complicate the reproducibility and reliability of SERS data. This review systematically discusses the problems mentioned above, including a comprehensive analysis of the challenges in precisely evaluating SERS spectra for pesticide detection. We not only point out the existing limitations of the method, which can be traced in previous review works, but also offer practical recommendations to improve the quality and comparability of SERS spectra, thereby expanding the potential applications of the method in such an essential field as pesticide detection.

Hydrothermal Fabrication of Efficient Binary Pd/Ag2S Heterojunction Composites: Synthesis, Characterization, and Fluorometric Selective Sensing of Organophosphate Pesticides.

Although many plasmonic nanosensors have been established for the detection of analytes, few of them are feasible for analyzing natural samples with very complex matrices because of insufficient method selectivity. To address this challenge, we propose an epitaxial and lattice-mismatch approach to the synthesis of a unique Pd/Ag2S nanostructure, which consists of a Pd segment with excellent plasmonic characteristics, and a highly stable Ag2S portion with minimum solubility product (Ksp(Ag2S) = 6.3 × 10- 50). Hence, Ag2S nanoparticles (NPs) and optimized (10.05 mmol/L) Pd/Ag2S composite were prepared using a hydrothermal method. The fabricated samples were characterized using different tools including UV-vis DRS, PL, powder XRD, TEM, and BET surface area measurements. Furthermore, the fluorometric sensing performance of the Ag2S and Pd/Ag2S samples was examined in the detection of organophosphate pesticides such as MLT, PRT, DZN, FNT, DCL, MCP, and CPS pesticides at room temperature. The quantitative detection of MLT, PRT, DZN, FNT, DCL, MCP, and CPS pesticides was achieved based on the Pd/Ag2S composite and organophosphate group-specific interaction. The optimized sensor exhibited a lower limit of detection (3.08 µM), excellent reproducibility, selectivity, and stability with an enhanced sensitivity of - 207.1 µA/µM cm2 (R2 = 0.98) in the range of 10 µM-100 µM for the detection of CPS pesticide. In addition, the fluorometric sensor has excellent selectivity, reproducibility, and stability, providing a feasible method for not only the detection of CPS pesticides but also other analytes in the future.

Introducing Mn into ZIF-8 nanozyme for enhancing its catalytic activities and adding specific recognizer for detection of organophosphorus pesticides.

In order to design and establish a highly efficient and selective nanozyme-based sensing platform for the UV-vis detection of organophosphorus pesticides (OPs), Mn was introduced into ZIF-8 nanozyme for enhancing its catalytic activities and adding specific recognizer. The Mn-doped ZIF-8 (Mn-ZIF-8) nanocomposites were synthesized with a very facile one-pot method by heating the mixture of ZnO, 2-methylimidazole (Hmin) and Mn(CH3COO)2·4H2O in a solvent-free system at 180 °C for 8 h. The Mn-ZIF-8 nanocomposite showed a higher peroxidase activity and an additional thiocholine (TCh)-degradable property compared to the pristine ZIF-8. OPs could inhibit acetylcholinesterase (AChE) to catalyze the hydrolysis of acetylthiocholine (ATCh) to produce TCh, thus blocking the degradation of Mn-ZIF-8 and protecting the catalysis of the oxidation of colorless 3,3',5,5'-tetramethylbenzydine (TMB) to blue oxidized TMB (ox-TMB). Accordingly, a detection method for OPs with high sensitivity and selectivity was designed and established on the basis of the Mn-ZIF-8 nanozyme with a linear range of 0.1-20 nM and a limit of detection (LOD) as low as 54 pM.

Broad-spectrum portable magnetic relaxation switching immunosensor with gold-functionalized magnetic nanoprobes for the sensitive detection of multiple pyrethroids.

At present, the most available pyrethroid (PYR) detection methods still suffer from a narrow detection spectrum, low sensitivity, and less portability. Herein, a novel magnetic relaxation switching (MRS) sensor was elaboratively designed to detect multiple PYRs, combining a novel broad-spectrum antibody CL-CN/1D2 and synthesized immune gold-functionalized magnetic nanoparticles, with the inherent response of the sensor. A series of antibodies and the immune gold-functionalized magnetic nanoparticles were designed and synthesized. The broad-spectrum antibody CL-CN/1D2 and high-performance gold-functionalized magnetic nanoprobe were further selected. The target analytes were effectively captured by the gold-functionalized magnetic nanoparticles in 20% (v/v) ethanol, resulting in the number increase of the signaling probes in the supernatant after magnetic separation. This sensor can detect multiple PYRs with a detection limit of 2.72 µg/L for cypermethrin, 3.58 µg/L for ß-cypermethrin, 4.07 µg/L for cyfluthrin, 3.66 µg/L for λ-cyhalothrin, 4.42 µg/L for ß-cyhalothrin, 3.51 µg/L for fenpropathrin, 4.41 µg/L for fenvalerate, and 4.12 µg/L for deltamethrin in lake water and milk within 35 min. This study not only achieves broad-spectrum PYRs detection at a trace amount but also provides an effective and universal strategy for enhancing the sensitivity and stability of the portable MRS sensor when detecting hydrophobic analytes in the environment.

ALP-Based Biosensors Employing Electrodes Modified with Carbon Nanomaterials for Pesticides Detection.

Due to the growing presence of pesticides in the environment and in food, the concern of their impact on human health is increasing. Therefore, the development of fast and reliable detection methods is needed. Enzymatic inhibition-based biosensors represent a good alternative for replacing the more complicated and time-consuming traditional methods (chromatography, spectrophotometry, etc.). This paper describes the development of an electrochemical biosensor exploiting alkaline phosphatase as the biological recognition element and a chemically modified glassy carbon electrode as the transducer. The biosensor was prepared modifying the GCE surface by a mixture of Multi-Walled-Carbon-Nanotubes (MWCNTs) and Electrochemically-Reduced-Graphene-Oxide (ERGO) followed by the immobilization of the enzyme by cross-linking with bovine serum albumin and glutaraldehyde. The inhibition of the biosensor response caused by pesticides was established using 2-phospho-L-ascorbic acid as the enzymatic substrate, whose dephosphorylation reaction produces ascorbic acid (AA). The MWCNTs/ERGO mixture shows a synergic effect in terms of increased sensitivity and decreased overpotential for AA oxidation. The response of the biosensor to the herbicide 2,4-dichloro-phenoxy-acetic-acid was evaluated and resulted in the concentration range 0.04-24 nM, with a limit of the detection of 16 pM. The determination of other pesticides was also achieved. The re-usability of the electrode was demonstrated by performing a washing procedure.

In-situ preparation of hollow CdCoS2 heterojunction with enhanced photocurrent response for highly photoelectrochemical sensing of organophosphorus pesticides.

In this study, a porous hollow CdCoS2(2) microsphere was synthesized based on the ZIF-67-S MOFs derived method of sulfurization reaction and calcination process. Under visible light irradiation, the resulting CdCoS2(2) composite showed a markedly enhanced photoelectrochemical (PEC) response. The photocurrent value of the CdCoS2(2) modified ITO electrode was 93-fold and 41-fold than that of CoS and CdS materials, respectively. Promoting the photo-absorption ability by internal multilight scattering/reflection was due to the porous and hollow nature of CdCoS2(2). Furthermore, obtained CdCoS2(2) heterostructure in-situ with a close contact interface could facilitate the separation/migration of photo-induced carriers. The CdCoS2(2) was also mixed with Ag nanoparticles (NPs) to further improve the PEC response. Acetylcholinesterase (AChE) as a bio-recognition molecule was immobilized on the glutaraldehyde-chitosan (GLD-CS) modified CdCoS2(2)@Ag electrode surface by cross-linking effect. AChE could hydrolyze the acetylcholine chloride (ATCl) to produce an electron donor of thiocholine which led to the elevated photocurrent output. When the bioactivity of AChE was inhibited by the organophosphate pesticides (chlorpyrifos as substrate), the reduced production of thiocholine resulted in a decline in photocurrent. Under optimal conditions, the structured AChE/GLD-CS/CdCoS2(2)@Ag/ITO sensing platform was successfully achieved for chlorpyrifos detection. The wide linear response range was from 0.001 to 270 µg mL-1 and with a low detection limit of 0.57 ng mL-1. The proposed PEC biosensor also exhibited excellent selectivity and good stability, demonstrating the designed porous hollow CdCoS2(2)@Ag heterostructured composite promised to be a great application in the PEC sensors.

Pesticides and Male Fertility: A Dangerous Crosstalk.

In recent decades, an increasing incidence of male infertility has been reported. Interestingly, and considering that pesticides have been used for a long time, the high incidence of this pathological state is concomitant with the increasing use of these chemicals, suggesting they are contributors for the development of human infertility. Data from literature highlight the ability of certain pesticides and/or their metabolites to persist in the environment for long periods of time, as well as to bioaccumulate in the food chain, thus contributing for their chronic exposure. Furthermore, pesticides can act as endocrine disrupting chemicals (EDCs), interfering with the normal function of natural hormones (which are responsible for the regulation of the reproductive system), or even as obesogens, promoting obesity and associated comorbidities, like infertility. Several in vitro and in vivo studies have focused on the effects and possible mechanisms of action of these pesticides on the male reproductive system that cause sundry negative effects, even though through diverse mechanisms, but all may lead to infertility. In this review, we present an up-to-date overview and discussion of the effects, and the metabolic and molecular features of pesticides on somatic cells and germinal tissues that affect germ cell differentiation.

A silver@gold nanoparticle tetrahedron biosensor for multiple pesticides detection based on surface-enhanced Raman scattering.

The detection of multiple pesticides in food and environment is of great importance for human health and safety. In this study, the DNA backbone structure and Ag@Au nanoparticles (NPs) to construct a nano-tetrahedron with the help of the surface-enhanced Raman scattering (SERS) effect by controlling the formation of SERS hotspots and subsequently realized the simultaneous detection of multiple pesticides. The DNA aptamers corresponding to the three pesticides of profenofos, acetamiprid and carbendazim were embedded into the three edges of the DNA tetrahedral skeleton, and the tetrahedral corners were connected to modify the Ag@Au NPs with different Raman signaling molecules. When aptamers recognize the related pesticides, the DNA backbone is deformed. Then Ag@Au NPs approach to each other with SERS hotspots formed and the intensity of the Raman signal increased, realizing the detection of the pesticide content. The biosensor constructed from the SERS substrate with higher sensitivity and lower detection limit (profenofos: 0.0021 ng mL-1; acetamiprid: 0.0046 ng mL-1; carbendazim: 0.0061 ng mL-1). The practicability of this proposed method was verified by adding the recovery rate detection and the accuracy of the method was examined by the analysis of the HPLC-MS method. The proposed SERS biosensor could distinguish and detect three pesticides in food and environmental samples with high sensitivity and low detection limit that can be used in practical applications.

Eco-Friendly Nanoplatforms for Crop Quality Control, Protection, and Nutrition.

Agricultural chemicals have been widely utilized to manage pests, weeds, and plant pathogens for maximizing crop yields. However, the excessive use of these organic substances to compensate their instability in the environment has caused severe environmental consequences, threatened human health, and consumed enormous economic costs. In order to improve the utilization efficiency of these agricultural chemicals, one strategy that attracted researchers is to design novel eco-friendly nanoplatforms. To date, numerous advanced nanoplatforms with functional components have been applied in the agricultural field, such as silica-based materials for pesticides delivery, metal/metal oxide nanoparticles for pesticides/mycotoxins detection, and carbon nanoparticles for fertilizers delivery. In this review, the synthesis, applications, and mechanisms of recent eco-friendly nanoplatforms in the agricultural field, including pesticides and mycotoxins on-site detection, phytopathogen inactivation, pest control, and crops growth regulation for guaranteeing food security, enhancing the utilization efficiency of agricultural chemicals and increasing crop yields are highlighted. The review also stimulates new thinking for improving the existing agricultural technologies, protecting crops from biotic and abiotic stress, alleviating the global food crisis, and ensuring food security. In addition, the challenges to overcome the constrained applications of functional nanoplatforms in the agricultural field are also discussed.

Metal Nanostructures for Environmental Pollutant Detection Based on Fluorescence.

Heavy metal ions and pesticides are extremely dangerous for human health and environment and an accurate detection is an essential step to monitor their levels in water. The standard and most used methods for detecting these pollutants are sophisticated and expensive analytical techniques. However, recent technological advancements have allowed the development of alternative techniques based on optical properties of noble metal nanomaterials, which provide many advantages such as ultrasensitive detection, fast turnover, simple protocols, in situ sampling, on-site capability and reduced cost. This paper provides a review of the most common photo-physical effects impact on the fluorescence of metal nanomaterials and how these processes can be exploited for the detection of pollutant species. The final aim is to provide readers with an updated guide on fluorescent metallic nano-systems used as optical sensors of heavy metal ions and pesticides in water.

Rapid detection of five pesticide residues using complexes of gold nanoparticle and porphyrin combined with ultraviolet visible spectrum.

BACKGROUD: Pesticides are widely used to control insect infestation and weeds in agriculture. However, concerns about the pesticide residues in agricultural products have been raised in recent years because of public interest in health and food quality and safety. Thus, rapid, convenient, and accurate analytical methods for the detection and quantification of pesticides are urgently required. RESULTS: A nanohybrid system composed of gold nanoparticles (AuNPs) and tetrakis(N-methyl-4-pyridiniumyl) porphyrin (TMPyP) was used as an optical probe for the detection and quantification of five pesticides (Paraquat, Dipterex, Dursban, methyl thiophanate and Cartap). The method is based on the aggregation effect of pesticides on the carboxyl group modified by AuNPs. Subsequently, with the help of particle swarm optimization-optimized sample weighted least squares-support vector machine (PSO-OSWLS-SVM), all the pesticides could be successfully quantified. In addition, partial least squares discriminant analysis (PLS-DA) was applied and the five pesticides were satisfactorily recognized based on data array obtained from the ultraviolet visible (UV-visible) spectra of AuNP-TMPyP complex. Furthermore, the quantitative and qualitative analysis of the five pesticides could be also achieved in the complex real samples, in which all the relative standard deviations (RSDs) were less than 0.3‰ and all the linear absolute correlation coefficients were more than 0.9990. Furthermore, recognition rate of the training set and the prediction set based on multiplicative scatter correction (MSC), or second-order derivative (2nd derivative) UV-visible spectra in PLS-DA model could reach 100%. CONCLUSION: This method was successfully applied for the rapid and accurate determination of multicomponent pesticide residues in real food samples. © 2020 Society of Chemical Industry.

Plasmon-active optical fiber functionalized by metal organic framework for pesticide detection.

Functional plasmonic fiber for detection and on-line monitoring of organophosphorus pesticides in water or model soil samples is described. The appearance of the plasmon absorption band was realized through the deposition of a thin gold layer on the naked core of multimode optical fiber. The metalorganic frameworks (MOF-5) layer was deposited on the gold surface for the introduction of a high affinity towards the target pesticides. The MOF-5 layer affords the extraction of pesticides and their concentration primarily in the "plasmon evanescent wave" space, allowing the detection by the shift of plasmon absorption band. The growth of MOF-5 layer was confirmed using the Raman, XPS and XRD measurements. The entrapping of pesticides was checked using the Raman spectroscopy and ellipsometry, which also indicate the corresponding changes of MOF-5 refractive index. The series of further experiments demonstrate the applicability of proposed fiber sensor for detection of pesticides in soil without the false signals from surrounding media. The main advantages of proposed sensor can be attributed to simplicity, high sensitivity, low cost and the absence of organic solvents for the probe treatment.

An acetylcholinesterase biosensor based on doping Au nanorod@SiO2 nanoparticles into TiO2-chitosan hydrogel for detection of organophosphate pesticides.

A stable and sensitive electrochemical acetylcholinesterase (AChE) biosensor for detection of organophosphorus pesticides (OPs) was developed by doping Au nanorods (AuNRs)@mesoporous SiO2 (MS) core-shell nanoparticles into CS/TiO2-CS (CS denotes for chitosan) immobilization matrix. AuNRs@MS core-shell nanoparticles were synthesized and characterized. The doping and the biosensor fabrication process were probed and confirmed by scanning electron microscopy and electrochemistry techniques. The doping conditions were optimized. The matrix both before and after AChE immobilization had a mesoporous nanostructure. The nanoparticles dispersed homogeneously within the matrix. The doping significantly enhanced the electro-conductivity of the TiO2-CS hydrogel, and dramatically improved the bioelectrocatalytic activity and OPs detection sensitivity of the AChE immobilized matrix. The detection linear ranges for both dichlovos (DDVP) and fenthion were from 0.018 µM (4.0 ppb) to 13.6 µM, and the limit of detection (LOD) was 5.3 nM (1.2 ppb) and 1.3 nM (0.36 ppb), respectively. The biosensor exhibited high reproducibility and accuracy in detecting OPs spiked vegetable juice samples. In addition, it exhibited very high detection stability and storage stability. The developed AChE biosensor was provided to be a promisingly applicable tool for OPs detection with high reliability, simplicity, and rapidness.

Polydopamine-Capped Bimetallic AuPt Hydrogels Enable Robust Biosensor for Organophosphorus Pesticide Detection.

Noble metal hydrogels/aerogels with macroscopic nanoassemblies characterized by ultralow density, profuse continuous porosity, and extremely large surface area have gained abundant interest due to not only their tunable physicochemical properties, but also promising applications in catalysis and sensing. Coupling the increased reaction temperature with dopamine-induced effect, herein, a one-step synthetic approach with accelerated gelation kinetics is reported for the synthesis of polydopamine-capped bimetallic AuPt hydrogels. 3D porous nanowire networks with surface functionalization of polydopamine make them a promising biocompatible microenvironment for immobilizing acetylcholinesterase (AChE) and constructing enzyme-based biosensors for sensitive detection of organophosphorus compounds. Taking advantage of their favorable structure and composition, the optimized product exhibits superior electrochemical activity toward thiocholine produced by AChE-catalyzed hydrolysis of acetylthiocholine. Based on the inhibition of organophosphorus pesticide on the enzymatic activity of AChE, the inhibition mode for the detection of paraoxon-ethyl is established, displaying linear regions over the range of 0.5-1000 ng L-1 with a low detection limit of 0.185 ng L-1 .

Identification and analysis of Triphenyltin chloride with surface enhanced Raman scattering spectroscopy.

Triphenyltin (TPhT) is a kind of organotin compounds which have been used ubiquitously as herbicide, pesticide, and fungicide in agriculture. The present study provides the possibility to detect and monitor TPhT with normal Raman spectroscopy and surface enhanced Raman scattering (SERS) spectroscopy. Firstly, the complete vibrational Raman spectra characterization of TPhT along with the IR spectroscopy were reported for the first time. Then a wide range of pH values were carried out to choose the optimal pH value in TPhT detection by using Raman spectroscopy. Afterwards, Raman spectra of various TPhT solutions were collected and analyzed. The results indicate that the optimal pH value for TPhT detection by Raman spectroscopy is 5.5, and with silver nanoparticles (Ag NPs) as SERS substrate is an effective technique for trace TPhT detection with an enhancement by 5 orders of magnitude and the detection limit can be as low as 0.6 ng/L within less than 30 s. Finally, in this study, the residual of TPhT on apple peel was investigated by casting different concentrations of TPhT on apple peel under the current optimized condition. The result demonstrates that TPhT could be detected based on its SESR spectra at 6.25 ng/cm(2) in standard solutions.

Integrated electrochemical biosensor based on algal metabolism for water toxicity analysis.

An autonomous electrochemical biosensor with three electrodes integrated on the same silicon chip dedicated to the detection of herbicides in water was fabricated by means of silicon-based microfabrication technology. Platinum (Pt), platinum black (Pt Bl), tungsten/tungsten oxide (W/WO3) and iridium oxide (Pt/IrO2) working ultramicroelectrodes were developed. Ag/AgCl and Pt electrodes were used as reference and counter-integrated electrodes respectively. Physical vapor deposition (PVD) and electrodeposition were used for thin film deposition. The ultramicroelectrodes were employed for the detection of O2, H2O2 and pH related ions H3O(+)/OH(-), species taking part in photosynthetic and metabolic activities of algae. By measuring the variations in consumption-production rates of these electroactive species by algae, the quantity of herbicides present at trace level in the solution can be estimated. Fabricated ultramicroelectrodes were electrochemically characterized and calibrated. Pt Black ultramicroelectrodes exhibited the greatest sensitivity regarding O2 and H2O2 detection while Pt/IrO2 ultramicroelectrodes were more sensitive for pH measurement compared to W/WO3 ultramicroelectrodes for pH measurement. Bioassays were then conducted to detect traces of Diuron herbicide in water samples by evaluating disturbances in photosynthetic and metabolic activities of algae caused by this herbicide.