Rapid and sensitive suspension array for multiplex detection of organophosphorus pesticides and carbamate pesticides based on silica-hydrogel hybrid microbeads

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.

In Situ Self-Assembled Formation of Nitrogen-Rich Ag@Ti3C2 Film for Sensitive Detection and Spatial Imaging of Pesticides with Laser Desorption/Ionization Mass Spectrometry (LDI-MS)

Pesticide residues are hazardous to human health; thus, developing a rapid and sensitive method for pesticide detection is an urgent need. Herein, novel nitrogen-rich Ag@Ti₃C₂ (Ag@N-Ti₃C₂) was synthesized via an ecofriendly, ultraviolet-assisted strategy, followed by in situ formation of a highly homogeneous film on target carriers via a facile water evaporation-induced self-assembly process. Ag@N-Ti₃C₂ shows greater surface area, electrical conductivity, and thermal conductivity than Ti₃C₂. This Ag@N-Ti₃C₂ film overcomes the limitations of conventional matrixes and allows laser desorption/ionization mass spectrometry (LDI-MS) to provide fast and high-throughput analysis of pesticides (e.g., carbendazim, thiamethoxam, propoxur, dimethoate, malathion, and cypermethrin) with ultrahigh sensitivity (detection limits of 0.5-200 ng/L), enhanced reproducibility, extremely low background, and good salt tolerance. Furthermore, the levels of pesticides were quantified with a linear range of 0-4 μg/L (R² > 0.99). This Ag@N-Ti₃C₂ film was used for high-throughput analysis of pesticides spiked in traditional Chinese herbs and soft drink samples. Meanwhile, high-resolution Ag@N-Ti₃C₂ film-assisted LDI-MS imaging (LDI MSI) was used to successfully explore spatial distributions of xenobiotic pesticides and other endogenous small molecules (e.g., amino acids, saccharides, hormones, and saponin) in the roots of plants. This study presents the new Ag@N-Ti₃C₂ self-assembled film equably deposits on the ITO slides and provides a dual platform for pesticide monitoring and has the advantages of high conductivity, accuracy, simplicity, rapid analysis, minimal sample volume requirement, and an imaging function.

A colorimetric smartphone-based platform for pesticides detection using Fe-N/C single-atom nanozyme as oxidase mimetics

In this study, a novel highly sensitive colorimetric platform has been designed for malathion assay based on Fe-N/C SAzyme. The as-synthesized SAzyme can directly oxidize 3,3´,5,5´-tetramethylbenzidine (TMB) to generate blue colored oxidized TMB. L-ascorbic acid-2-phosphate (AA2P), a substrate of acid phosphatase (ACP), could be hydrolyzed to AA, thereafter inhibit the oxidization reaction of TMB, leading to a conspicuous blue color fading. With the addition of malathion hindered the ACP activity and limited the AA production, resulting in the recovery of the catalytic activity of single-atom nanozyme. Under optimized operational conditions, a novel colorimetric assay has been designed for malathion detection with LOD of 0.42 nM. Besides, quantification of malathion in environmental and food samples was achieved based on the proposed strategy. In addition, the successfully integrated paper/smartphone sensor provided sensitive, and rapid, reliable detection of malathion with a LOD of 1 nM.

Computer-aided profiling of a unique broad-specific antibody and its application to an ultrasensitive fluoroimmunoassay for five N-methyl carbamate pesticides

Pollution of N-methyl carbamate (NMC) pesticides is threatening the non-target organisms' survival. Thus, broad-specific antibodies and class-selective immunoassays are demanding for multiple NMCs determination. In this study, we employed a molecular docking-based virtual screening strategy to fast profile antibody spectrum, based on a designed chemical pool containing 17 compounds. A monoclonal antibody (mAb)-6G against carbofuran was used as the objective. The recombinant full-length IgG was successfully expressed to validate the antibody sequences for homology modeling. After docking, we manually categorized the antibody-chemical binding strength into three groups. Non-competitive surface plasmon resonance (SPR) demonstrated the mAb-6G affinitive binding toward five NMCs (carbofuran, isoprocarb, propoxur, carbaryl and carbosulfan), which were classified into strong and moderate binding categories. Antibody binding properties were confirmed again by ic-ELISA and lateral flow immunochromatographic strip. Subsequently, an ultrasensitive indirect competitive fluoromicrosphere-based immunoassay (ic-FMIA) was established with the IC₅₀ (half-maximal inhibitory concentration) values of 0.08-3.37 ng/mL. This portable assay presented a 30-230-fold improved sensitivity than traditional ic-ELISA and was applied in European surface water analysis. Overall, our work provides an efficient platform integrating in-silico and experimental methodologies to accelerate the characterization of hapten-specific antibody binding properties and the development of high-sensitive immunoassays for multi-pollutants monitoring.

Freeze-thaw and solvent-exchange strategy to generate physically cross-linked organogels and hydrogels of curdlan with tunable mechanical properties

Physical gels from natural polysaccharides present the advantage of no toxic cross-linking agents and no chemical modification during preparation. Herein, novel physical gels, transparent organogels and opaque hydrogels from the microorganism-derived (1,3)-β-D-glucan of curdlan were prepared in dimethyl sulfoxide (DMSO) using the freeze-thaw technique, followed by a solvent-exchange strategy with water. The mechanical and structural properties of these gels were investigated by rheology, scanning electron microscopy, attenuated total reflection infrared spectroscopy, wide-angle X-ray diffraction and small-angle X-ray scattering. Gelation mechanisms and intermolecular interaction models have also been proposed. The good solvent DMSO serves as both a crosslinker and a pore-foaming agent in organogels. The reversible macromolecular conformation changes and phase separation of curdlan endow the gels with reversible transparency, volume change and tunable mechanical strength. The new design strategy of facile preparation and performance tuning provides a platform for developing new organogels and sterile hydrogels of curdlan.

Suspension array for multiplex immunoassay of five common endocrine disrupter chemicals

A low cost and effective indirect competitive method is reported to detect five EDCs, 17-beta-estradiol (E2), estriol (E3), bisphenol A (BPA), diethylstilbestrol (DES), and nonylphenol (NP) simultaneously, based on suspension array technology (SAT). Five kinds of complete antigens (E2-BSA, E3-BSA, BPA-BSA, DES-BPA, NP-BSA) were coupled to different encoding microspheres using purpose-made solutions in our laboratory instead of commercially available amino coupling kits; the method was further optimized for determination and reducing  the cost. Encoding and signaling fluorescence of the particles are determined at 635/532 nm emission wavelengths. High-throughput curves of five EDCs were draw and the limit of detection (LOD) were between 0.0010 ng mL^-1 ~ 0.0070 ng mL^-1. Compared with traditional ELISA methods, the SAT exhibited better specificity and sensitivity. Experiments using spiked milk and tap water samples were also carried out, and the recovery was between 85 and 110%; the results also confirmed good repeatability and reproducibility. It illustrated great potential of the present strategy in the detection of EDCs in actual samples.

Fabrication of Nano/Micro-Structured Electrospun Detection Card for the Detection of Pesticide Residues

A novel nano/micro-structured pesticide detection card was developed by combining electrospinning and hydrophilic modification, and its feasibility for detecting different pesticides was investigated. Here, the plain and hydrophilic-modified poly(ε-caprolactone) (PCL) fiber mats were used for the absorption of indolyl acetate and acetylcholinesterase (AChE), respectively. By pre-treating the fiber mat with ethanol, its surface wettability was improved, thus, promoting the hydrolysis of the PCL fiber mat. Furthermore, the absorption efficiency of AChE was improved by almost two times due to the increased hydrophilicity of the modified fiber mat. Noteworthily, this self-made detection card showed a 5-fold, 2-fold, and 1.5-fold reduction of the minimum detectable concentration for carbofuran, malathion, and trichlorfon, respectively, compared to the national standard values. Additionally, it also exhibited good stability when stored at 4 °C and room temperature. The food detection test showed that this nano/micro-based detection card had better detectability than the commercial detection card. Therefore, this study offers new insights into the design of pesticide detection cards, which also broadens the application of electrospinning technique.

The Role of Suspension Array Technology in Rapid Detection of Foodborne Pollutants: Applications and Future Challenges

Food safety is an important livelihood issue, which has always been focused attention by countries and governments all over the world. As food supply chains are becoming global, food quality control is essential for consumer protection as well as for the food industry. In recent years, a great part of food analysis is carried out using new techniques for rapid detection. As the first biochip technology that has been approved by the Food and Drug Administration (FDA), there is an increasing interest in suspension array technology (SAT) for food and environmental analysis with advantages of rapidity, high accuracy, sensitivity, and throughput. Therefore, it is important for researchers to understand the development and application of this technology in food industry. Herein, we summarized the principle and composition of SAT and its application in food safety monitoring. The utility of SAT in detection of foodborne microorganisms, residues of agricultural and veterinary drugs, genetically modified food and allergens in recent years is elaborated, and the further development direction of SAT is envisaged.

Employing a fluorescent and colorimetric picolyl-functionalized rhodamine for the detection of glyphosate pesticide

The ongoing poisoning of agricultural products has pushed the security problem to become an important issue. Among them, exceeding the standard rate of pesticide residues is the main factor influencing the quality and security of agricultural products. Monitoring pesticide residues and developing simple, yet ultrasensitive detection systems for pesticide residues are urgently needed. In this study, we successfully developed a novel rhodamine derivative as fluorescent and colorimetric chemosensor R-G for the rapid, selective and ultrasensitive detection of glyphosate pesticide residue in aqueous solution. Through a Cu²⁺-indicator displacement strategy, glyphosate can displace an indicator (R-G) from a Cu²⁺-indicator complex due to its strong affinity to bind with Cu²⁺ to give a turn-on fluorescence and distinct color change. Moreover, a test strip was also fabricated to achieve a facile detection of glyphosate pesticide. To demonstrate the possibility of practical applications, glyphosate was detected on the surface of cabbage and in a spiked soil sample. The detection limit of 4.1 nM and the response time of 2 min indicate that the method is enough sensitive and rapid to detect the glyphosate residue at or below levels that pose a health risk.

Detect, remove and re-use: Sensing and degradation pesticides via 3D tilted ZMRs/Ag arrays

The objective of this study was to design a versatile and reusable pesticide detection surface-enhanced Raman scattering (SERS) substrate in combination with SERS enhancement and self-cleaning properties. In this paper, we present an inexpensive way to synthesize three-dimensional tilted ZnO micron rods with an Ag hierarchical structure (ZMRs/Ag arrays). Although expensive materials and complex methods were not used, the detection limit of thiram residue was 10^-11 M, with a quantitative relationship (R² = 0.9929) between the thiram concentration and the intensity of the SERS peaks. Additionally, the substrates exhibited fast and efficient photocatalytic activity for the degradation of adsorbed thiram, and the degradation rate in 30 min was close 100 % under visible-light irradiation. The enhancement and photocatalytic mechanism of this substrate were meticulously analyzed in detail. Furthermore, the residues of several mixed pesticides (e.g., thiram and methamidophos compounds) in various juices (such as grape, pear, orange, apple, and cherry juices) were quickly detected using ZMRs/Ag substrates. The main advantages of this substrate are recyclability, stability, selectivity, handiness, and cost-eff ;ectiveness. The substrate can prevent single-use problems associated with conventional SERS substrates and can be applied in pesticide residue and food security.

Acetylcholinesterase-functionalized two-dimensional photonic crystal for the sensing of G-series nerve agents

G-series nerve agents, such as sarin, tabun, and soman, would cause tremendous harm in military and terrorist attacks, so it is necessary to develop a simple method for the rapid and efficient detection of these hazardous substances. We have developed a tunable acetylcholinesterase (AChE)-functionalized two-dimensional photonic crystal (2D PhC) for the detection of a real nerve agent, sarin. In accordance with the 2D PhC previously prepared by our group, the AChE-functionalized 2D PhC was optimized by adjustment of the amount of monomer in the hydrogel, which not only increased the sensitivity of the 2D PhC, with the detection limit decreasing by two orders of magnitude, but also ensured the structural color spanned the whole visible region in the detection range. A linear relationship between the logarithm of the sarin concentration and the particle spacing of the AChE-functionalized 2D PhC was observed from 7.1 × 10^-17 to 7.1 × 10^-4 mol/L. The AChE-functionalized 2D PhC also responded to mimics of G-series nerve agents, including dimethyl methylphosphonate, diisopropyl methylphosphonate, and isodipropyl methylphosphonate, to various degrees. The proposed 2D-PhC hydrogel has potential for low-cost, trace-level, and on-site monitoring of other G-series nerve agents. Graphical abstract.

Pesticide binding and urea-induced controlled release applications with calixarene naphthalimide molecules by host-guest complexation

Three novel calix[4]arene molecule-based 1,8 naphthalimide fluoroionophore for the selective determination of kesoxim-methyl were synthesized and used in pesticide binding studies. The possible interaction between pesticides and fluorescent calix[4]arene molecules was monitored by UV/Vis absorption and fluorescence spectroscopy. When compared the studied pesticides, kesoxim-methyl was strongly quenched the fluorescence intensity of upper rim-modified calix[4]arene. UV and fluorescence titration experiments were also studied to determine both the quenching mechanism and stoichiometric ratio consisted in complex formation. Furthermore, pesticide release experiments were also performed with a fertilizing agent as urea by using fluorescence spectroscopy technique.

Visual detection of 2,4,6-trinitrotolune by molecularly imprinted colloidal array photonic crystal

We developed a photonic crystal (PhC) sensor for the quantification of 2,4,6-trinitrotoluene (TNT) in solution. Monodisperse (210nm in diameter) molecularly imprinted colloidal particles (MICs) for TNT were prepared by the emulsion polymerization of methyl methacrylate and acrylamide in the presence of TNT as a template. The MICs were then self-assembled into close-packed opal PhC films. The adsorption capacity of the MICs for TNT was 64mg TNT/g. The diffraction from the PhC depended on the TNT concentration in a methanol/water (3/2, v/v) potassium dihydrogen phosphate buffer solution (pH=7.0, 30mM). The limit of detection (LOD) of the sensor was 1.03μg. The color of the molecularly imprinted colloidal array (MICA) changed from green to red with an 84nm diffraction red shift when the TNT concentration increased to 20mM. The sensor response time was 3min. The PhC sensor was selective for TNT compared to similar compounds such as 2,4,6-trinitrophenol, 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2-nitromesitylene, 4-nitrotoluene, 2-nitrotoluene, 1,3-dinitrobenzene, methylbenzene, 4-nitrophenol, 2-nitroaniline, 3-aminophenol and 3-nitroaniline. The sensor showed high stability with little response change after three years storage. This sensor technology might be useful for the visual determination of TNT.

Functionalized photonic crystal for the sensing of Sarin agents

The indiscriminate use of nerve agents by terrorist groups has attracted attention of the scientific communities toward the development of novel sensor technique for these deadly chemicals. A photonic crystal (PhC) hydrogel immobilized with butyrylcholinesterase (BuChE) was firstly prepared for the sensing of Sarin agents. Periodic polystyrene colloidal (240nm) array was embedded inside an acrylamide hydrogel, and then BuChE was immobilized inside the hydrogel matrix via condensation with 3-(diethoxyphosphoryloxy)-1,2,3-benzotriazin-4(3h)-one (DEPBT). It indicated that a total of 3.7 units of BuChE were immobilized onto the PhC hydrogel. The functionalized hydrogel recognized the Sarin agent and then shrunk, thus the diffraction of PhC hydrogel blue shifted significantly, and a limit of detection (LOD) of 10(-15)molL(-1) was achieved.

Synthesis and sensing applications of a new fluorescent derivative of cholesterol

The Hg²⁺ quenched emission of a specially designed fluorophore could be fully turned on upon the introduction of organophosphorus pesticides.

Fluorescence-based bioassays for the detection and evaluation of food materials

We summarize here the recent progress in fluorescence-based bioassays for the detection and evaluation of food materials by focusing on fluorescent dyes used in bioassays and applications of these assays for food safety, quality and efficacy. Fluorescent dyes have been used in various bioassays, such as biosensing, cell assay, energy transfer-based assay, probing, protein/immunological assay and microarray/biochip assay. Among the arrays used in microarray/biochip assay, fluorescence-based microarrays/biochips, such as antibody/protein microarrays, bead/suspension arrays, capillary/sensor arrays, DNA microarrays/polymerase chain reaction (PCR)-based arrays, glycan/lectin arrays, immunoassay/enzyme-linked immunosorbent assay (ELISA)-based arrays, microfluidic chips and tissue arrays, have been developed and used for the assessment of allergy/poisoning/toxicity, contamination and efficacy/mechanism, and quality control/safety. DNA microarray assays have been used widely for food safety and quality as well as searches for active components. DNA microarray-based gene expression profiling may be useful for such purposes due to its advantages in the evaluation of pathway-based intracellular signaling in response to food materials.