A highly sensitive fluorescence immunochromatography strip for thiacloprid in fruits and vegetables using recombinant antibodies

A Monoclonal Antibody-Based Time-Resolved Fluorescence Microsphere Lateral Flow Immunoassay for Dinotefuran and Clothianidin Detection

Dinotefuran and clothianidin belong to the third generation of nicotinic insecticides and are widely used in crop pest control. It is necessary to detect their residues in food. The time-resolved fluorescent microspheres lateral flow immunoassay (TRFMs-LFIA) has the advantages of high sensitivity, short duration, and simple operation and is suitable for rapid field testing. In this study, two haptens (FCA-1, FCA-2) were synthesized in three steps and conjugated to the carrier proteins to obtain artificial antigens, which were subsequently used for monoclonal antibody preparation. A TRFMs-LFIA based on monoclonal antibodies was established to detect dinotefuran and clothianidin residues in food. The limit of detection (LOD) for dinotefuran was 0.045 ng/mL, with an IC50 of 0.61 ng/mL and a linear range (IC20~IC80) of 0.12~3.11 ng/mL. The LOD for clothianidin was 0.11 ng/mL, with an IC50 of 0.94 ng/mL and a linear range (IC20~IC80) of 0.24~3.65 ng/mL. Cross-reactivity rates with seven tested structural analogs were less than 1.5%. The pretreatment method was optimized for wheat, cucumber, and cabbage samples, which was time-saving (20 min) and easy to operate. The average recovery rates ranged from 88.0% to 114.8%, with the corresponding coefficients of variation appearing (CV) between 1.9% and 13.5%. The results of actual wheat, cucumber, and cabbage samples detected by the established TRFMs-LFIA were consistent with those of Ultra-Performance Liquid Chromatography coupled with Tandem Mass Spectrometry (UPLC-MS/MS). These results demonstrate that the established TRFMs-LFIA is sensitive, accurate, rapid, and suitable for real sample detection.

Bidirectionally Favorable Platform: A Dual-Targeting Probe-Encoded Maple Leaf-Type Fluorescent Lateral Flow Immunoassay for Multiple Biomarker Detection

In the traditional multiplexed lateral flow immunoassay (LFIA), different detection probes against different targets are necessary. However, the relative complexity and high cost of probe preparation, as well as the insufficient user-friendliness, limit the application of the multiplexed LFIA in disease diagnosis. Here, we reported a bidirectionally favorable LFIA (BDF-LFIA) platform to maximize convenience for both manufacturers and users. Red-emitting time-resolved fluorescent nanoparticles were coated with different antibodies to recognize multiple targets simultaneously, which greatly simplified probe preparation by the manufacturers. Ultrabright green-emitting gold nanoclusters were pre-embedded on the test line as a reference signal to achieve a target concentration-dependent maple leaf-type hue readout from green to yellow to red, which was quite user-friendly. Taking cancer biomarkers alpha-fetoprotein and carcinoembryonic antigen as examples, this assay achieved a visual detection limit of 2 ng/mL. Compared with the conventional fluorescent LFIA, the BDF-LFIA could generate a more discernible signal around the threshold concentration of the targets. Moreover, the assay successfully diagnosed 54 clinical samples. Overall, the BDF-LFIA showed bidirectional benefits for both manufacturers and users and provided a new concept for the LFIA in multiplexed detection.

A comprehensive review of recombinant technology in the food industry: Exploring expression systems, application, and future challenges

Biotechnology has significantly advanced the production of recombinant proteins (RPs). This review examines the latest advancements in protein production technologies, including CRISPR, genetic engineering, vector integration, and fermentation, and their implications for the food industry. This review delineates the merits and shortcomings of prevailing host systems for RP production, underscoring molecular and process strategies pivotal for amplifying yields and purity. It traverses the spectrum of RP applications, challenges, and burgeoning trends, highlighting the imperative of employing robust hosts and cutting-edge genetic engineering to secure high-quality, high-yield outputs while circumventing protein aggregation and ensuring correct folding for enhanced activity. Recombinant technology has paved the way for the food industry to produce alternative proteins like leghemoglobin and cytokines, along with enzyme preparations such as proteases and lipases, and to modify microbial pathways for synthesizing beneficial compounds, including pigments, terpenes, flavonoids, and functional sugars. However, scaling microbial production to industrial scales presents economic, efficiency, and environmental challenges that demand innovative solutions, including high-throughput screening and CRISPR/Cas9 systems, to bolster protein yield and quality. Although recombinant technology holds much promise, it must navigate high costs and scalability to satisfy the escalating global demand for RPs in therapeutics and food. The variability in ethical and regulatory hurdles across regions further complicates market acceptance, underscoring an urgent need for robust regulatory frameworks for genetically modified organisms. These frameworks are essential for safeguarding the production process, ensuring product safety, and upholding the efficacy of RPs in industrial applications.

Novel time-resolved fluorescent-based multiplex immunochromatography test strip for simultaneous detection of pesticides in vegetables

The presence of multiple pesticide residues in vegetables has become an increasingly critical concern. Immunochromatography has garnered significant interest for its convenience, sensitivity and speed. However, conventional immunochromatography was typically limited to single-target detection, exhibiting restricted efficiency and high costs in on-site large-scale detection scenarios. Dual-channel time-resolved fluorescent immunochromatography test strip (TRFITS) was developed for the simultaneous rapid detection of imidacloprid (IMI) and tolfenpyrad (TOL) in 15 min. Utilizing the excellent optical properties of time-resolved fluorescent microspheres, this TRFITS enabled better detection sensitivity (0.22 ng/mL for IMI, 11.85 ng/mL for TOL), which was approximately 20 times more sensitive than that of conventional immunochromatography, under optimal conditions. In addition, the TRFITS successfully detected IMI and TOL in vegetables samples with acceptable accuracy. The ability to simultaneously quantify multiple pesticide residues using a single test strip reduces material consumption and lowers operational costs, offering a practical solution for rapid on-site pesticide screening.

Dual-functional probe-based multi-signal immunosensor platform for tropane alkaloids: Verification and evaluation

This study aims to realise rapid detecting of tropane alkaloids (TAs) in food. For this purpose, a broad-spectrum single-chain fragment variable was fused with horseradish peroxidase to create an antibody-enzyme complex (AEC) with antigen recognition and catalytic activity. A multi-signal immunosensor platform based on AEC in the direct competitive reaction mode was constructed using 3,3',5,5'-tetramethylbenzidine and 10-acetyl-3,7-dihydroxyphenoxazine as substrates. The sensitivity of TAs in the immunosensor platform ranged from 0.25 μg/kg to 7912.46 μg/kg. Honey was selected as a representative food sample, and the limit of detection of TAs in honey ranged from 0.02 μg/kg to 409.11 μg/kg, with a recovery rate of 65.7 %-117.1 % and a coefficient of variation less than 21.4 %. Results showed that the immunosensor platform possesses satisfactory accuracy and precision, which highlights its potential for practical applications and its suitability as an ideal tool for rapid screening of TAs in food.

Production of a monoclonal antibody against thiacloprid, resistant to matrix interference, and its application in quantitatively immunochromatographic assay

Thiacloprid (THI) is a neonicotinoid insecticide, and its residues pose potential risks to the ecological environment and human health. In this study, computer simulation technology was applied to analyze THI haptens to ensure the similarity in spatial structure, charge properties, and potential distribution. And anti-THI monoclonal antibodies insensitive to matrix effects were prepared using sample extraction solution to simulate the matrix environment, with the half-maximal inhibitory concentration of 0.070 ng/mL in the matrix environment. Furthermore, a colloidal gold immunochromatographic assay (ICA) was established for the detection of THI residues in fruit and vegetable samples, with a quantitative detection range of 0.880-11.091 μg/kg, 1.669-14.056 μg/kg, 31.570-586.121 μg/kg, and 42.291-778.803 μg/kg in grapes, oranges, cucumbers, and tomatoes, respectively. Real sample testing indicated that this method had good consistency with LC-MS/MS. Therefore, the ICA withstood matrix interference, accurately and effectively determined THI residues in fruit and vegetable samples.

Rapid and convenient screening method based on single-chain variable fragments for the detection of restricted monensin in chicken muscle

A colloidal gold immunochromatographic assay (CGIA) based on single-chain variable fragments (scFvs) has been successfully developed for the detection of monensin (MON). Colloidal gold probes were conjugated to anti-MON scFvs through electrostatic interaction, with the conjugated objects serving as the visual signals. The detection lines were formed by capturing the antibody with MON-OVA. This assay offers a rapid detection time of 15 min, a wide linear range from 2.19 to 10.76 ng mL-1, and boasts high accuracy, precision, and an absence of cross-reactivity. By homology modeling and molecular docking, we predicted the interaction patterns between the scFv and monensin, and the amino acid residues involved in the recognition of MON by the antibody were analyzed. These key amino acid sites are presumed integral to ligand recognition per current interaction models. This hypothesis was confirmed by computer-aided alanine scanning mutation, MM/P(G)BSA molecular dynamics simulation, and in vitro binding experiments. In this study, we successfully developed the scFvs-based CGIA system for rapid and easy quantification of monensin, providing a simple, efficient routine detection of chicken muscle samples.

Establishment of a rapid and sensitive ic-ELISA for the detection of thiacloprid residues in honey and medicinal herbs using a novel highly specific monoclonal antibody

Thiacloprid is one of the first generation of neonicotinoid insecticide with a chloropyridine structure like imidacloprid and acetamiprid. Recent studies have revealed its environmental and non-target organism toxicity, leading to restrictions on its use in many countries and regions. Despite limitations, thiacloprid has been detected in various environmental samples, food sources, and biological specimens, posing a significant threat to human health, necessitating advanced detection methods for monitoring. In this study, a highly specific monoclonal antibody against thiacloprid via a multi-immunogen strategy was prepared and a rapid and sensitive enzyme-linked immunosorbent assay for the detection of thiacloprid residues in honey and medicinal herbs was established. The half maximal inhibitory concentration (IC50) of this method was 0.38 ng/mL, improving the sensitivity by 1.2-480.6 times compared to existing reports, and the limit of detection (IC20) was 0.097 ng/mL. The method was successfully applied to the determination of thiacloprid residues in honey and medicinal herbs (Crataegi fructus, Citri reticulatae pericarpium), achieving recovery rates ranging from 87.50 % to 116.11 %. The obtained results were verified using the LC-MS/MS method. The multi-immunogen strategy proposed in this study provides an approach for the preparation of highly sensitive and specific monoclonal antibodies, and immunoassay established based on it has good application prospects in complex matrices.

Comparison of single-chain variable fragments and monoclonal antibody against dihydroartemisinin

Immunoassay relies on antibodies, but traditional antibodies such as monoclonal antibody (mAb) require animal immunization and complex procedures. Single-chain variable fragment (scFv) becomes a potential alternative to mAb with advantages of the low cost, rapid and easy prepared. In the present study, we prepared scFvs against dihydroartemisinin (DHA) based on E. coli and HEK293T cell expression system, named MBP-scFv and scFv-Fc, respectively. Their properties were compared with the parent mAb. The calculated affinity constants of mAb, MBP-scFv and scFv-Fc were 2.1 × 108 L mol-1, 2.2 × 107 L mol-1 and 1.6 × 108 L mol-1, respectively. The half inhibitory concentration (IC50) of mAb, MBP-scFv and scFv-Fc were 1.16 ng mL-1, 2.15 ng mL-1 and 6.57 ng mL-1, respectively. Both the scFv showed less sensitive than the mAb based on the IC50. The cross-reactivities of MBP-scFv for artemisinin and artesunate exhibited similarities to the mAb, yet the cross-reactivities of scFv-Fc for these compounds exceeded those of the mAb significantly. The stability of the scFvs was ascertained to be maintained for over 5 days at room temperature, and for more than a month at both 4 °C and - 20 °C. After that, the indirect competitive enzyme-linked immunosorbent assays (icELISAs) based on the scFv from E. coli were used to detect the DHA content in eight drug samples, and the result was consistent with ultra-performance liquid chromatography simultaneously. Although scFv can be used for quantitative determination of drugs, but it still cannot completely replace mAb in immunoassay without evolution and modification.

A novel core-shell up-conversion nanoparticles immunochromatographic assay for the detection of deoxynivalenol in cereals

Deoxynivalenol (DON) toxin is a type B group of trichothecene mycotoxins mainly originating from specific Fusarium fungi, seriously harming human and livestock health. Herein, a novel core-shell up-conversion nanoparticles immunochromatographic assay (CS-UCNPs-ICA) was developed for deoxynivalenol based on the competitive reaction principle. By exploiting the fluorescence intensity of the T and C lines of CS-UCNPs-ICA, the concentrations of DON were obtained sensitively and precisely under optimized conditions in 5 min with a detection limit of 0.1 ng/mL. The CS-UCNPs-ICA strips only specifically detect DON and its derivatives (3-Ac-DON and 15-Ac-DON), with no cross-reaction with other mycotoxins. The low CV values illustrated a modest intra- and inter-assay variation, confirming the superior precision of this method. In the spiked experiment, the mean recoveries of corn and wheat ranged from 94.74% to 100.90% and 96.21%-104.81%, respectively. Furthermore, the approach generated results that were in good agreement with data from HPLC and ELISA analyses of naturally contaminated feed and cereals, confirming that the significant advantages of proposed strips were their high practicality, rapidness, and simplicity. Therefore, the CS-UCNPs-ICA strips platform serves as a promising candidate for developing new approaches for rapid testing or high throughput screening from DON in food products.

Surface-Enhanced Raman Spectroscopy Using a Silver Nanostar Substrate for Neonicotinoid Pesticides Detection

Surface-enhanced Raman spectroscopy (SERS) has been introduced to detect pesticides at low concentrations and in complex matrices to help developing countries monitor pesticides to keep their concentrations at safe levels in food and the environment. SERS is a surface-sensitive technique that enhances the Raman signal of molecules absorbed on metal nanostructure surfaces and provides vibrational information for sample identification and quantitation. In this work, we report the use of silver nanostars (AgNs) as SERS-active elements to detect four neonicotinoid pesticides (thiacloprid, imidacloprid, thiamethoxam and nitenpyram). The SERS substrates were prepared with multiple depositions of the nanostars using a self-assembly approach to give a dense coverage of the AgNs on a glass surface, which ultimately increased the availability of the spikes needed for SERS activity. The SERS substrates developed in this work show very high sensitivity and excellent reproducibility. Our research opens an avenue for the development of portable, field-based pesticide sensors, which will be critical for the effective monitoring of these important but potentially dangerous chemicals.

Developments in food neonicotinoids detection: novel recognition strategies, advanced chemical sensing techniques, and recent applications

Neonicotinoid insecticides (NEOs) are a new class of neurotoxic pesticides primarily used for pest control on fruits and vegetables, cereals, and other crops after organophosphorus pesticides (OPPs), carbamate pesticides (CBPs), and pyrethroid pesticides. However, chronic abuse and illegal use have led to the contamination of food and water sources as well as damage to ecological and environmental systems. Long-term exposure to NEOs may pose potential risks to animals (especially bees) and even human health. Consequently, it is necessary to develop effective, robust, and rapid methods for NEOs detection. Specific recognition-based chemical sensing has been regarded as one of the most promising detection tools for NEOs due to their excellent selectivity, sensitivity, and robust interference resistance. In this review, we introduce the novel recognition strategies-enabled chemical sensing in food neonicotinoids detection in the past years (2017-2023). The properties and advantages of molecular imprinting recognition (MIR), host-guest recognition (HGR), electron-catalyzed recognition (ECR), immune recognition (IR), aptamer recognition (AR), and enzyme inhibition recognition (EIR) in the development of NEOs sensing platforms are discussed in detail. Recent applications of chemical sensing platforms in various food products, including fruits and vegetables, cereals, teas, honey, aquatic products, and others are highlighted. In addition, the future trends of applying chemical sensing with specific recognition strategies for NEOs analysis are discussed.

High-Performance Fluorescent Microspheres Based on Fluorescence Resonance Energy Transfer Mode for Lateral Flow Immunoassays

The label with a large Stokes shift and strong fluorescence properties could improve the sensitivity of the lateral flow immunoassay (LFIA). Herein, two aggregation-induced emission (AIE) luminogens with spectral overlap were encapsulated in polymers by using the microemulsion method as a label, and the construction of a fluorescence resonance energy transfer mode was further verified via theoretical calculation and spectral analysis. Satisfactorily, the doped AIE polymer microspheres (DAIEPMs) exhibited a large Stokes shift of 285 nm and a 10.8-fold fluorescence enhancement compared to those of the AIEPMs loaded with acceptors. Benefiting from the excellent optical performance, DAIEPMs were applied to the LFIA for sensitive detection of chlorothalonil, which is an organochlorine pesticide. The limit of detection of the proposed DAIEPMs-LFIA was 1.2 pg/mL, which was 4.8-fold and 11.6-fold lower than those of quantum dot bead LFIA and gold nanoparticle LFIA, respectively. This work provides a new strategy to improve the optical properties of fluorescent materials and construct a sensitive and reliable detection platform.

Generation of broad-spectrum recombinant antibody and construction of colorimetric immunoassay for tropane alkaloids: Recognition mechanism and application

Tropane alkaloids (TAs) have emerged as plant toxins, related to poisoning events. The development of stable antibodies is crucial to ensure the effectiveness of immunological methods in quickly and accurately monitoring these alkaloids. In this study, based on hybridoma, the variable region gene of monoclonal antibody (mAb) was amplified, and the recombinant antibody (rAb) gene sequence (VH-Linker-VL) was successfully constructed and expressed in HEK293F. The obtained rAb has kept the same performance as mAb, and the IC50 of 29 TAs ranged from 0.12 to 2642.78 ng/mL. In the recognition mechanism, the docking and dynamics model identified hydrophobic interaction as the most critical force. Substituent will impact recognition by influencing the spatial structure and hydrophobic properties. Then, a colorimetric immunoassay based on rAb was established, five types of water and thirty-nine nectars of honey were tested. The results demonstrated the absence of TAs in environmental water, whereas atropine was detected in more than 13.47% of honey samples at concentrations exceeding 1 μg/kg. The results show a good correlation with UHPLC-MS/MS, suggesting that the immunoassay has excellent screening ability. The data on TAs in honey and water could serve as a foundation for developing relevant policies.

Screening and identification of a DNA aptamer to construct the label-free fluorescent aptasensor for ultrasensitive and selective detection of clothianidin residue in agricultural products

Clothianidin pesticide not only pollutes the ecological environment, but also poses a potential threat to human health. Thus, it is of great importance to develop efficient and accurate methods to recognize and detect clothianidin residues in agricultural products. Aptamer has the advantages of easy modification, high affinity and good stability, which is particularly suitable as a recognition biomolecule for pesticide detection. However, the aptamer against clothianidin has not been reported. Herein, the aptamer (named CLO-1) had good selectivity and strong affinity (K_d = 40.66 ± 3.47 nM) to clothianidin pesticide, which was screened for the first time by Capture-SELEX strategy. The binding effect of CLO-1 aptamer to clothianidin was further studied by circular dichroism (CD) spectroscopy and molecular docking technique. Finally, the CLO-1 aptamer was used as the recognition molecule to construct a label-free fluorescent aptasensor using GeneGreen dye as sensing signal for the highly sensitive detection of clothianidin pesticide. The constructed fluorescent aptasensor had the limit of detection (LOD) as low as 5.527 μg L^-1 for clothianidin, and displayed good selectivity against other competitive pesticides. The aptasensor was applied to detect the clothianidin spiked in tomatoes, pears and cabbages, and the recovery rate was good in the range of 81.99%-106.64%. This study provides a good application prospect for the recognition and detection of clothianidin.

Chronic larval exposure to thiacloprid impairs honeybee antennal selectivity, learning and memory performances

The use of agricultural neonicotinoid insecticides has sub-lethal chronic effects on bees that are more prevalent than acute toxicity. Among these insecticides, thiacloprid, a commonly used compound with low toxicity, has attracted significant attention due to its potential impact on the olfactory and learning abilities of honeybees. The effect of sub-lethal larval exposure to thiacloprid on the antennal activity of adult honeybees (Apis mellifera L.) is not yet fully understood. To address this knowledge gap, laboratory-based experiments were conducted in which honeybee larvae were administered thiacloprid (0.5 mg/L and 1.0 mg/L). Using electroantennography (EAG), the impacts of thiacloprid exposure on the antennal selectivity to common floral volatiles were evaluated. Additionally, the effects of sub-lethal exposure on odor-related learning and memory were also assessed. The results of this study reveal, for the first time, that sub-lethal larval exposure to thiacloprid decreased honeybee antenna EAG responses to floral scents, leading to increased olfactory selectivity in the high-dose (1.0 mg/L) group compared to the control group (0 mg/L vs. 1.0 mg/L: p = 0.042). The results also suggest that thiacloprid negatively affected odor-associated paired learning acquisition, as well as medium-term (1 h) (0 mg/L vs. 1.0 mg/L: p = 0.019) and long-term memory (24 h) (0 mg/L vs. 1.0 mg/L: p = 0.037) in adult honeybees. EAG amplitudes were dramatically reduced following R-linalool paired olfactory training (0 mg/L vs. 1.0 mg/L: p = 0.001; 0 mg/L vs. 0.5 mg/L: p = 0.027), while antennal activities only differed significantly in the control between paired and unpaired groups. Our results indicated that exposure to sub-lethal concentrations of thiacloprid may affect olfactory perception and learning and memory behaviors in honeybees. These findings have important implications for the safe use of agrochemicals in the environment.