Development of aptamer surface-enhanced Raman spectroscopy sensor based on Fe3O4@Pt and Au@Ag nanoparticles for the determination of acetamiprid.

As a common chlorinated nicotinic pesticide with high insecticidal activity, acetamiprid has been widely used for pest control. However, the irrational use of acetamiprid will pollute the environment and thus affect human health. Therefore, it is crucial to develop a simple, highly sensitive, and rapid method for acetamiprid residue detection. In this study, the capture probe (Fe3O4@Pt-Aptamer) was connected with the signal probe (Au@DTNB@Ag CS-cDNA) to form an assembly with multiple SERS-enhanced effects. Combined with magnetic separation technology, a SERS sensor with high sensitivity and stability was constructed to detect acetamiprid residue. Based on the optimal conditions, the SERS intensity measured at 1333 cm-1 is in relation to the concentration of acetamiprid in the range 2.25 × 10-9-2.25 × 10-5 M, and the calculated limit of detection (LOD) was 2.87 × 10-10 M. There was no cross-reactivity with thiacloprid, clothianidin, nitenpyram, imidacloprid, and chlorpyrifos, indicating that this method has good sensitivity and specificity. Finally, the method was applied to the detection of acetamiprid in cucumber samples, and the average recoveries were 94.19-103.58%, with RSD < 2.32%. The sensor can be used to analyse real samples with fast detection speed, high sensitivity, and high selectivity.

A Simple Aptamer SERS Sensor Based on Mesoporous Silica for the Detection of Chlorpyrifos.

Chlorpyrifos is an organophosphorus insecticide, which can be used to control a variety of chewing and piercing mouthparts pests in agricultural production. It can destroy the normal nerve impulse conduction by inhibiting the activity of acetylcholinesterase or cholinesterase in the nerves, causing a series of poisoning symptoms. In order to achieve the quantitative analysis of chlorpyrifos residues in agricultural products, an aptamer-controlled signal molecule release method was developed in this study. The signal molecule 4-ATP of surface-enhanced Raman spectroscopy (SERS) was loaded into aminated mesoporous silica nanoparticles (MSNs-NH2) prepared by the one pot method, and then coated with an aptamer of chlorpyrifos through electrostatic interaction. The specific binding of the aptamer and chlorpyrifos led to the release of 4-ATP, and the amount of 4-ATP released was positively correlated with the amount of chlorpyrifos. Finally, the standard curve of chlorpyrifos quantitative detection based on SERS was established. Meanwhile, Ag-carrying mesoporous silica (Ag@MSNs) was prepared as the reinforcement substrate for SERS detection. The results showed that there was a good linear correlation between the Raman intensity and the concentration of chlorpyrifos at 25−250 ng/mL, and the limit of detection (LOD) was 19.87 ng/mL. The recoveries of chlorpyrifos in the apple and tomato samples were 90.08−102.2%, with RSD < 3.32%. This method has high sensitivity, specificity, reproducibility and stability, and can be used for the quantitative detection of chlorpyrifos in the environment and agricultural products.

A simple mesoporous silica Nanoparticle-based aptamers SERS sensor for the detection of acetamiprid.

In this study, we developed a novel, rapid, simple, and sensitive nano sensor based on the controlled release of 4-Aminothiophenol (4-ATP) signal molecules from aptamers (Apts) modified aminated mesoporous silica nanoparticles (MSNs-NH2) for the quantitative detection of acetamiprid (ACE). Firstly, we synthesized the positively charged MSNs-NH2 by one-pot method, then loaded 4-ATP signal molecules into the pore, and finally electrostatically adsorbed the Apts onto the MSNs-NH2, which acts as a gate to control the release of signal molecules. When ACE is added to the system, ACE preferentially and specifically binds to Apts, so the gate opens and 4-ATP signal molecules are released from the pore. Meanwhile, the silver-loaded mesoporous silica nanoparticles (Ag@SiO2) were prepared by one-pot method as surface-enhanced Raman spectroscopy (SERS) substrate to amplify the signal. The intensity of 4-ATP signal molecules at 1433 cm-1 position was observed to has a linear relationship with the concentration of ACE by SERS detection. Under the optimized detection conditions, a linear correlation was observed in the range of 5-60 ng/mL (R2 = 0.99749), and the limit of detection (LOD) was 2.66 ng/mL. The method has high sensitivity, good selectivity and reproducibility, and can be used for actual sample analysis with the recovery rate of 96.24-103.6 %. This study provides a reference for the rapid and convenient detection of ACE in agricultural products.

Determination of Acetamiprid Residues in Vegetables by Indirect Competitive Chemiluminescence Enzyme Immunoassay.

Acetamiprid (ACE) is widely used in various vegetables to control pests, resulting in residues and posing a threat to human health. For the rapid detection of ACE residues in vegetables, an indirect competitive chemiluminescence enzyme immunoassay (ic-CLEIA) was established. The optimized experimental parameters were as follows: the concentrations of coating antigen (ACE-BSA) and anti-ACE monoclonal antibody were 0.4 and 0.6 µg/mL, respectively; the pre-incubation time of anti-ACE monoclonal antibody and ACE (sample) solution was 30 min; the dilution ratio of goat anti-mouse-HRP antibody was 1:2500; and the reaction time of chemiluminescence was 20 min. The half-maximum inhibition concentration (IC50), the detection range (IC10-IC90), and the detection limit (LOD, IC10) of the ic-CLEIA were 10.24, 0.70-96.31, and 0.70 ng/mL, respectively. The cross-reactivity rates of four neonicotinoid structural analogues (nitenpyram, thiacloprid, thiamethoxam, and clothianidin) were all less than 10%, showing good specificity. The average recovery rates in Chinese cabbage and cucumber were 82.7-112.2%, with the coefficient of variation (CV) lower than 9.19%, which was highly correlated with the results of high-performance liquid chromatography (HPLC). The established ic-CLEIA has the advantages of simple pretreatment and detection process, good sensitivity and accuracy, and can meet the needs of rapid screening of ACE residues in vegetables.

Fluorescent aptamer-modified mesoporous silica nanoparticles for quantitative acetamiprid detection.

Acetamiprid (ACE) is widely used to control aphids, brown planthoppers, and other pests in agricultural production. However, ACE is difficult to degrade in the environment, resulting in excessive residue, which causes acute and chronic toxicity to human beings and non-target organisms. Therefore, the development of a rapid, convenient, and highly sensitive method to quantify ACE is essential. In this study, aminated mesoporous silica nanoparticles (MSNs-NH2) were synthesized by one-pot method, and 6-carboxyl fluorescein modified aptamers (FAM-Apt) of ACE were adsorbed on the surface of MSNs-NH2 by electrostatic interaction. Finally, a simple and sensitive fluorescence analysis method for the rapid detection of ACE was established. In the absence of ACE, the negatively charged FAM-Apt was electrostatically bound to the positively charged MSNs-NH2, followed by centrifugation to precipitate MSNs-NH2@FAM-Apt, and no fluorescent signal was detected in the supernatant. In the presence of ACE, the specific combination of FAM-Apt with ACE was greater than its electrostatic interaction with MSNs-NH2, so that FAM-Apt was separated from MSNs-NH2, and the supernatant had strong fluorescence signal after centrifugation. For ACE detection, the linear concentration range was 50-1100 ng/mL, and the detection limit (LOD) was 30.26 ng/mL. The method exhibited high sensitivity, selectivity and reproducibility, which is suitable for practical sample analysis and provides guidance for rapid detection of pesticide residues.

Facile pathway to construct mesoporous silica nanoparticles loaded with pyraclostrobin: Physicochemical properties, antifungal activity, and biosafety.

BACKGROUND: A controlled-release formulation based on mesoporous silica nanoparticles (MSNs) provides an effective way for reducing pesticide use and protecting the ecological environment. In this study, MSNs loaded with pyraclostrobin (PYR@MSNs) were prepared using a one-pot method. RESULTS: The characteristics of PYR@MSNs were systematically investigated, including morphology, loading content, ultraviolet (UV) resistance, release behavior, control effects against pathogens, and safety to nontarget organisms. The results show that the prepared PYR@MSNs presented characteristics of regular spherical shapes, uniform particle size (200 nm), high drug loading (38.9%), and enhanced UV resistance. Compared with traditional formulation, PYR@MSNs exhibited improved control effects against Fusarium graminearum, an extended control period, and lower toxicity to zebrafish, earthworms and BEAS-2B cells. CONCLUSIONS: This research will facilitate the development of efficient and safe pesticide delivery systems. The PYR@MSNs has showed its potential as a new controlled-release formulation with increased efficacy and is expected to benefit the sustainable development of agriculture. © 2022 Society of Chemical Industry.

Preparation of thermosensitive buprofezin-loaded mesoporous silica nanoparticles by the sol-gel method and their application in pest control.

BACKGROUND: Environmental stimuli-responsive release is one important way to reduce the dosage of pesticide, increase the usage efficiency and improve environmental compatibility. RESULTS: On this basis, we synthesized mesoporous silica nanoparticles (MSNs) and modified them to develop a thermosensitive pesticide controlled release formulation (CRF). In this study, MSNs prepared by the sol-gel method were used as the core, poly (N-IsoPropylAcrylaMide) [P (NIPAM-MAA)] was used as the shell, and buprofezin (Bup) was loaded by adsorption. The prepared Bup@MSNs@P(NIPAM-MAA) could effectively prevent the degradation of buprofezin under UV light and exhibited excellent adhesion to rice leaves. The bioassay results showed that the mortality of Nilaparvata lugens (Stål) treated by Bup@MSNs@P(NIPAM-MAA) was positively correlated with temperature, resulting mainly from the change of release amount of buprofezin caused by temperature variation. Bup@MSNs@P(NIPAM-MAA) had long duration (20 days) for controlling N. lugens, and did not hinder the growth of rice. Meanwhile, Bup@MSNs@P(NIPAM-MAA) had low toxicity to zebrafish and human pneumonocyte BEAS-2B cells. CONCLUSION: This novel thermosensitive pesticide CRF can be applied widely to other insecticides, thus greatly promoting the development of intelligent pesticide formulations. © 2021 Society of Chemical Industry.

Screening of anti-idiotypic domain antibody from phage library for development of Bt Cry1A simulants.

Anti-idiotypic antibody technique is a new approach for the rapid development of insecticidal protein. In this study, anti-Cry1A polyclonal antibodies were used as antigen to screen the anti-idiotypic antibody that can simulate Cry1A toxins from a phage display human domain antibody (DAB) library. After four rounds of panning, five positive clones that have binding activities with anti-Cry1A polyclonal antibodies were obtained. Indirect competitive ELISA (IC-ELISA) results showed that the positive clone D6 showed significant inhibition for the binding of Cry1A toxins with anti-Cry1A polyclonal antibodies, and the inhibition ratio increased with the increase of D6 content. While, B3, F4, G5, C7 and the controls showed no obvious inhibition to Cry1A toxins. The results suggest that D6 is the "ß" subtype anti-idiotypic antibody, which can simulate Cry1A toxins and competitive binding with anti-Cry1A polyclonal antibodies. Meanwhile, D6 had certain binding activity with the brush border membrane vesicles (BBMV) of p. xylostella, which was the receptor of Cry1A toxins. The results of bioassay showed that D6 had certain insecticidal activity, and the lethal concentration of 50% (LC50) was 976 ng/cm2. This study provides basic materials and experience for the development of Cry toxin simulants.

Production and characterization of a single-chain variable fragment antibody from a site-saturation mutagenesis library derived from the anti-Cry1A monoclonal antibody.

There are plenty of applications of Cry1A toxins (Cry1Aa, Cry1Ab, Cry1Ac) in genetically modified crops, and it is necessary to establish corresponding detection methods. In this study, a single-chain variable fragment (scFv) with high affinities to Cry1A toxins was produced. First, the variable regions of heavy (VH) and light chain (VL) were amplified from hybridoma cell 5B5 which secrete anti-Cry1A monoclonal antibody (mAb) and then spliced into scFv-5B5 by overlap extension polymerase chain reaction (SOE-PCR). Subsequently, site-saturation mutagenesis was performed after homology modeling and molecular docking, which showed that asparagine35, phenylalanine36, isoleucine104, tyrosine105, and serine196, respectively, located in VH complementarity-determining region (CDR1 and CDR3) and VL framework region (FR3) were key amino acid sites. Then, the mutagenesis scFv library (1.35 × 105 CFU/mL) was constructed and a mutant scFv-2G12 with equilibrium dissociation constant (KD) value of 9.819 × 10-9 M against Cry1Ab toxin, which was lower than scFv-5B5 (2.025 × 10-8 M) was obtained by biopanning. Then, enzyme-linked immunosorbent assay (ELISA) was established with limit of detection (LOD) and limit of quantitation (LOQ) of 4.6-9.2 and 11.1-17.1 ng mL-1 respectively for scFv-2G12, which were lower than scFv-5B5 (12.4-22.0 and 23.6-39.7 ng mL-1). Results indicated the promising prospect of scFv-2G12 used for the detection of Cry1A toxins.