A bare-eye based one-step signal amplified semiquantitative immunochromatographic assay for the detection of imidacloprid in Chinese cabbage samples

A colloidal gold immunochromatographic method for rapid screening of imidacloprid residues in Chinese herbal medicines

An imidacloprid colloidal gold immunochromatographic strip was developed in this work, and systematic analytical conditions were deeply investigated. The test strips were used for rapid screening of imidacloprid residues in Chinese herbal medicines. The performance of the colloidal gold test strips was investigated by using five selected Chinese herbal medicines (malt, Coix seed, lotus seed, dried ginger and honeysuckle). As a result, the developed imidacloprid colloidal gold immunochromatographic test strips could be used for rapid screening of imidacloprid residues in 60 kinds of different herbs (including 26 kinds of root/rhizome medicines, 20 kinds of seed/fruit/pericarp medicines, 11 kinds of flower/leaf/whole herb medicines, and 3 kinds of bark/aboveground issues of herb medicines), and the cut-off value was 50 μg/kg. The development of this method can achieve the goal of on-site, rapid and low-cost screening of imidacloprid residues in different herbs, which is of great significance for the quality assurance of herbs.

Fluorescent and Colorimetric Dual-Readout Immunochromatographic Assay for the Detection of Phenamacril Residues in Agricultural Products

The fungicide phenamacril has been employed to manage Fusarium and mycotoxins in crops, leading to persistent residues in the environment and plants. Detecting phenamacril is pivotal for ensuring environmental and food safety. In this study, haptens and artificial antigens were synthesized to produce antiphenamacril monoclonal antibodies (mAbs). Additionally, gold nanoparticles coated with a polydopamine shell were synthesized and conjugated with mAbs, inducing fluorescence quenching in quantum dots. Moreover, a dual-readout immunochromatographic assay that combines the positive signal from fluorescence with the negative signal from colorimetry was developed to enable sensitive and precise detection of phenamacril within 10 min, achieving detection limits of 5 ng/mL. The method's reliability was affirmed by using spiked wheat flour samples, achieving a limit of quantitation of 0.05 mg/kg. This analytical platform demonstrates high sensitivity, outstanding accuracy, and robust tolerance to matrix effects, making it suitable for the rapid, onsite, quantitative screening of phenamacril residues.

Sensitization Strategies of Lateral Flow Immunochromatography for Gold Modified Nanomaterials in Biosensor Development

Gold nanomaterials have become very attractive nanomaterials for biomedical research due to their unique physical and chemical properties, including size dependent optical, magnetic and catalytic properties, surface plasmon resonance (SPR), biological affinity and structural suitability. The performance of biosensing and biodiagnosis can be significantly improved in sensitivity, specificity, speed, contrast, resolution and so on by utilizing multiple optical properties of different gold nanostructures. Lateral flow immunochromatographic assay (LFIA) based on gold nanoparticles (GNPs) has the advantages of simple, fast operation, stable technology, and low cost, making it one of the most widely used in vitro diagnostics (IVDs). However, the traditional colloidal gold (CG)-based LFIA can only achieve qualitative or semi-quantitative detection, and its low detection sensitivity cannot meet the current detection needs. Due to the strong dependence of the optical properties of gold nanomaterials on their shape and surface properties, gold-based nanomaterial modification has brought new possibilities to the IVDs: people have attempted to change the morphology and size of gold nanomaterials themselves or hybrid with other elements for application in LFIA. In this paper, many well-designed plasmonic gold nanostructures for further improving the sensitivity and signal output stability of LFIA have been summarized. In addition, some opportunities and challenges that gold-based LFIA may encounter at present or in the future are also mentioned in this paper. In summary, this paper will demonstrate some feasible strategies for the manufacture of potential gold-based nanobiosensors of post of care testing (POCT) for faster detection and more accurate disease diagnosis.

Recent Advances in Aptasensors for Rapid Pesticide Residues Detection

Pesticides are applied widely to increase agricultural output and quality, however, this practice results in residual issues that not only harm the environment but also put people and animals' lives and health at risk. As a result, it is critical to find pesticide residues in a variety of sources, including crops, water supplies, and soil. Aptamers are more flexible in their synthesis and modification, have a high level of specificity, are inexpensive, and have good stability compared to conventional detection methods. They have therefore attracted a lot of interest in the industry. This study reviews the most recent aptasensor advancements in the detection of pesticide residues. Firstly, aptamers specifically binding to many pesticides are summarized. Secondly, the combination of aptasensors with colorimetric, fluorescent, surface enhanced Raman spectroscopy (SERS), resonance Light Scattering (RLS), chemiluminescence (CL), electrochemical, and electrochemiluminescence (ECL) technologies are systematically introduced, and their advantages and disadvantages are expounded. Importantly, the aptasensors for the detection of various pesticides (organochlorine, organophosphorus, neonicotinoids, carbamates, and pyrethroids) that have been developed so far are systematically analyzed and discussed. Finally, the furture prospects and challenges of the aptasensors are highlighted. It is expected to offer suggestions for the later creation of novel, highly effective and sensitive aptasensors for the detection of pesticide residues.

Immunochromatographic assay for the analysis of methomyl in cabbage and tomato

In this study, a hapten of methomyl was designed and used to produce monoclonal antibodies (mAbs) against methomyl. Based on these mAbs, we developed an enzyme-linked immunosorbent assay (ELISA) and immunochromatographic assay (ICA) strip for the determination of methomyl residues. Results from the ELISA showed that mAb 1D10 exhibited higher affinity with an affinity constant of 2.76 × 10¹⁰ L/mol and higher sensitivity with a limit of detection (LOD) was 8.12 ng/mL. After optimizing the ICA, a visible limit of detection (vLOD) was found to be 100 ng/g and the cut-off value was 500 ng/g for methomyl in cabbage and tomato. The calculated LODs were 3.2 ng/g and 5.4 ng/g in cabbage and tomato, respectively. Moreover, results from the ICA were consistent with those of the ELISA in our recovery assay using spiked samples. Hence, the ICA method has a bright future and great prospects for the detection of methomyl in food samples.

Enhanced Lateral Flow Immunoassay with Double Competition and Two Kinds of Nanoparticles Conjugates for Control of Insecticide Imidacloprid in Honey

Finding optimal conditions for competitive lateral flow immunoassay is a controversial task. The content of specific antibodies labeled by nanoparticles should be simultaneously high to reach intense signals and low to register an influence on the signals for minimal concentrations of the target analyte. We propose to use two kinds of complexes of gold nanoparticles in the assay, with antigen-protein conjugates and with specific antibodies. The first complex interacts both with immobilized antibodies in the test zone and with antibodies on the surface of the second complex. In this assay, the coloration is enhanced by the binding of two-colored preparations in the test zone, whereas the antigen in the sample inhibits both the binding of the first conjugate with the immobilized antibodies and with the second conjugate. This approach is realized for the detection of insecticide imidacloprid (IMD), an important toxic contaminant connected with the recent global death of bees. The proposed technique expands the working range of the assay, that is, in accordance with its theoretical analysis. The reliable change of coloration intensity is achieved for a 2.3-times-lower concentration of the analyte. The limit of IMD detection is 0.13 ng/mL for tested solutions and 1.2 µg/kg for initial honey samples. The combination of two conjugates doubles the coloration in the absence of the analyte. The developed lateral flow immunoassay is applicable for five-fold-diluted honey samples without extraction, does not require additional stages (all reagents are pre-applied to the test strip), and is implemented in 10 min.

A comprehensive review on the pretreatment and detection methods of neonicotinoid insecticides in food and environmental samples

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The metabolism and residue status of neonicotinoids were briefly summarized in this work.

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Sample pretreatment techniques for the analysis of neonicotinoids were critically discussed.

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The commonly used detection methods for neonicotinoids residues were also pointed out.

In recent years, the residues of neonicotinoid insecticide in food and environmental samples have attracted extensive attention. Neonicotinoids have many adverse effects on human health, such as cancer, chronic disease, birth defects, and infertility. They have substantial toxicity to some non-target organisms (especially bees). Hence, monitoring the residues of neonicotinoid insecticides in foodstuffs is necessary to guarantee public health and ecological stability. This review aims to summarize and assess the metabolic features, residue status, sample pretreatment methods (solid-phase extraction (SPE), Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS), and some novel pretreatment methods), and detection methods (instrument detection, immunoassay, and some innovative detection methods) for neonicotinoid insecticide residues in food and environmental samples. This review provides detailed references and discussion for the analysis of neonicotinoid insecticide residues, which can effectively promote the establishment of innovative detection methods for neonicotinoid insecticide residues.

Lateral flow assay applied to pesticides detection: recent trends and progress

Devices based on lateral flow assay (LFA) have been gaining more and more space in the detection market mainly due to their simplicity, speed, and low cost. These devices have excellent sensing format versatility and make these strips an ideal choice for field applications. The COVID-19 pandemic boosted the democratization of this method as a "point of care testing" (POCT), and the trend is that these devices become protagonists for the monitoring of pesticides in the environment. However, designing LFA devices for detecting and monitoring pesticides in the environment is still a challenge. This is because analytes are small molecules and have only one antigenic determinant, which makes it difficult to apply direct immunoassays. Furthermore, most LFA devices provide only qualitative or semi-quantitative results and have a limited number of applications in multi-residue analysis. Here, we present the state of the art on the use of LFA in the environmental monitoring of pesticides. Based on well-documented results, we review all available LFA formats and strategies for pesticide detection, which may have important implications for the future of monitoring pesticides in the environment. The main advances, challenges, and perspectives of these devices for a direction in this field of study are also presented.

New Approach to Generate Ratiometric Signals on Immunochromatographic Strips for Small Molecules

The self-calibration capability of ratiometric signals has been widely considered to enhance the accuracy, sensitivity, and anti-interference ability of immunoassays. Exploring a new approach to generate ratiometric signals can provide more options for various requirements. Herein, we integrated the negative-readout competitive and positive-readout noncompetitive immunoassays into a single assay by employing different color tracers, labeled peptidomimetic and anti-immunocomplex peptides, to create a new unconstrained ratiometric signal approach. Using an immunochromatographic strip (ICS) and a fungicide benzothiostrobin as the analytical platform and analyte, respectively, we showed that this approach can be extensively applied to fluorescence and colorimetry readouts, which have also been proven for strong anti-interference ability to an external light environment. Moreover, the enormous intuitional color changes of ratiometric fluorescent and colorimetric ICSs (RFICS and RCICS) enabled the formation of the color reference cards (like the pH paper) for visual judgment. After adaptation with a portable smartphone, the quantitative detection limits for RFICS and RCICS were 0.17 and 0.44 ng mL^-1, respectively. In addition, the ICSs showed good accuracy for the detection of benzothiostrobin in spiked samples.

Competitive immune-nanoplatforms with positive readout for the rapid detection of imidacloprid using gold nanoparticles

Two high-sensitivity competitive immune-nanoplatforms based on the inner filter effect (IFE-IN) and magnetic separation (MS-IN) with a positive readout were developed to rapidly detect imidacloprid (IMI) using gold nanoparticles (AuNPs). For IFE-IN, IMI competes with AuNPs-labeled IMI antigens (IMI-BSA-AuNPs) to bind with anti-IMI monoclonal antibody (mAb)-conjugated NaYF4:Yb,Er upconversion nanoparticles, which changes the fluorescence signal at excitation/emission wavelength of 980/544 nm. For MS-IN, the immunocomplex of IMI-BSA-AuNPs and magnetic-nanoparticles-labeled mAb (mAb-MNPs) dissociates in the presence of IMI, and the optical density of IMI-BSA-AuNPs at 525 nm increases with the IMI concentration after magnetic separation. Under the optimal conditions, the IMI concentration producing a 50% saturation of the signal (SC50) and linear range (SC10- SC90) were found to be 4.30 ng mL-1 and 0.47 - 21.37 ng mL-1 for IFE-IN, while 1.21 ng mL-1 and 0.07 - 10.21 ng mL-1 for MS-IN, respectively. Both IFE-IN and MS-IN achieved excellent accuracy for the detection of IMI in different matrices. The quantities of IMI in apple samples detected by IFE-IN and MS-IN were consistent with the high-performance liquid chromatography results. For IFE-IN, analyte competes with AuNPs-labeled-antigen to bind with the mAb-conjugated-UCNPs, which changes the fluorescence signal at 544 nm. For MS-IN, the immunocomplex of AuNPs-labeled-antigen and mAb-conjugated-MNPs dissociates in the presence of analyte, and the optical density of AuNPs-labeled-antigen at 525 nm increases with increasing analyte concentration after separation.

Novel immunochromatographic strip assay based on up-conversion nanoparticles for sensitive detection of imidacloprid in agricultural and environmental samples

Neonicotinoid insecticides are widely used in agriculture for pest control, but the pesticide residues in environmental and agricultural products were a big threat to the health of non-target organisms. In this study, a new immunochromatographic strip test was established for the rapid detection of imidacloprid residue, a neonicotinoid insecticide, based on up-conversion nanoparticles (UCNPs) coupled with the monoclonal antibody against imidacloprid. Under optimal conditions, the half inhibitory concentration (IC₅₀), detection limit, and the linear range of this strip were 8.37 ng/mL, 0.45 ng/mL, and 0.97-250 ng/mL. The strip test could be completed in 30 min. The average recoveries of imidacloprid spiked in water, Chinese cabbages, cucumber, honey, and tea samples were 70.1~101.8%, with coefficient of variations less than 18.9%. The strip was used to test real samples and verified by UPLC-MS/MS method with the good agreement (R² was 0.9825), indicating this novel strip immunoassay is accurate and reliable.

Development and perspectives of rapid detection technology in food and environment

Food safety become a hot issue currently with globalization of food trade and food supply chains. Chemical pollution, microbial contamination and adulteration in food have attracted more attention worldwide. Contamination with antibiotics, estrogens and heavy metals in water environment and soil environment have also turn into an enormous threat to food safety. Traditional small-scale, long-term detection technologies have been unable to meet the current needs. In the monitoring process, rapid, convenient, accurate analysis and detection technologies have become the future development trend. We critically synthesizing the current knowledge of various rapid detection technology, and briefly touched upon the problem which still exist in research process. The review showed that the application of novel materials promotes the development of rapid detection technology, high-throughput and portability would be popular study directions in the future. Of course, the ultimate aim of the research is how to industrialization these technologies and apply to the market.

Translocation and metabolism of imidacloprid in cabbage: Application of 14C-labelling and LC-QTOF-MS

Imidacloprid (IMI) is a widely used neonicotinoid insecticide effective against sucking and some chewing insects. Translocation and metabolism of IMI in plants are related to food safety. In this study, ¹⁴C-labeled IMI was used to investigate its translocation, transformation, radioactive IMI metabolites and possible metabolic pathways in cabbage. The amount of IMI accumulated in the edible part of cabbage accounted for 80.3-95.4% of the applied amounts by foliar application. There was a tendency to transport from edible parts to inedible parts. The proportions of extractable IMI decreased gradually from 92.4% to 83.0% in edible parts, greater than that in inedible parts over the experiment (0-19 days), while the bound residues showed an opposite trend. The half-life of IMI was determined as 33.0 and 63.0 days in the edible parts and whole plant, respectively. Five radioactive components including the parent IMI were detected by HPLC-LSC. The relative content of M1 was less than 0.01 mg kg^-1, which was not required to identify according to the metabolic scheme proposed by the US Environmental Protection Agency. The metabolites N-nitro(1-6-chloro-3-pyridylmethyl)-4,5-dihydroxyimidazol-2-imine (M2), N-nitro(1-6-chloro-3-pyridylmethyl)-4/5-hydroxyimidazole-2-imine (M3) and 1/3-(1-6-chloro-3-pyridylmethyl)-2,4-imidazodione (M4) were identified by LC-QTOF-MS. The primary metabolism of IMI in cabbage included hydrolysis and oxidation. The residue level and daily intake values of IMI in cabbage were estimated to be 0.033-0.078 mg kg^-1 and 9.56-20.01 ng d^-1 kg^-1, respectively, which were far below the maximum residue level and allowable daily intake values.

Electrodeposition of silver onto carbon graphite and their catalysis properties toward thiamethoxam reduction: application in food and beverage samples

The purpose of this paper is the electrodeposition of silver particles on graphite electrode (Ag@GrCE) using chronoamperometry and the use of this electrode for the determination of thiamethoxam. The electrode was prepared by chronoamperometry and characterized by X-Ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), EDX analysis and electrochemical impedance spectroscopy. The obtained electrode exhibits excellent electrocatalytic activity toward thiamethoxam reduction. The voltammetric response was linear as function of TXM concentration with a limit of detection around to 1.92 × 10⁻⁶ mol L⁻¹. The proposed electrode was successfully used to analyze thiamethoxam residue in some food samples including orange and tomato juices.

Development of Fluorescence Polarization Immunoassay for Imidacloprid in Environmental and Agricultural Samples

A fluorescence polarization immunoassay (FPIA) for the determination of imidacloprid (IMI) was developed with advantages of simple operation and short assay time. The haptens of IMI, acetamiprid (ACE), and thiamethoxam (THI) were conjugated with fluorescein isothiocyanate ethylenediamine (EDF) and 4'-Aminomethyl fluorescein (AMF), respectively, to prepare six fluorescence tracers. The conjugation of IMI hapten and EDF (IMI-EDF) was selected to develop the FPIA due to the largest fluorescent polarization value increase in the presence of anti-IMI monoclonal antibody. Under the optimum condition, the limit of detection, 50% inhibition concentration and detection range of the FPIA were 1.7, 4.8, and 1.7-16.3 μg/L, respectively. The cross-reactivities (CRs) with the analogs of IMI were negligible except for imidaclothiz with CR of 79.13%. The average recovery of spiked paddy water, corn and cucumber samples were 82.4-118.5% with the RSDs of 7.0-15.9%, which indicated the FPIA had good accuracy. Thus, the developed FPIA was a potential tool for the rapid and accurate determination of IMI in agricultural and environmental samples.

Gold nanoparticle-decorated metal organic frameworks on immunochromatographic assay for human chorionic gonadotropin detection

Gold nanoparticle-decorated metal organic frameworks (MOF@AuNPs) with significantly enhanced color signal intensity were synthesized through in situ growth of AuNPs on the MOF skeleton. The resultant MOF@AuNP nanocomposites were characterized with 16.7-fold higher absorbance than conventional 40 nm AuNPs (AuNP₄₀). Thus, for the first time, we applied it as a signal amplification label to improve the immunochromatographic assay (ICA) of human chorionic gonadotropin (HCG). The detection limit of our enhanced ICA was 1.69 mIU/mL, which is ca. 10.6-fold improvement in sensitivity compared to traditional AuNP₄₀-ICA. The recoveries of this MOF@AuNPs-ICA ranged from 86.03 to 119.22%, with coefficients of variation of 3.05 to 13.74%. The reliability and practicability were further validated by the clinically used chemiluminescence immunoassay method. Given their excellent signal amplification ability, the proposed MOF@AuNPs could serve as an ideal ICA label for rapid and sensitive detection of disease biomarkers. Graphical abstract.

Text-Displaying Semiquantitative Competitive Lateral Flow Immunoassay Relying on Inkjet-Printed Patterns

This work describes a colorimetric signaling approach for competitive lateral flow immunoassays (LFIAs) enabling sensitive and semiquantitative direct visual result readout in the form of "text", demonstrated on the example of 8-hydroxy-2'-deoxyguanosine (8-OHdG) detection. The distinctive feature of the developed text-displaying LFIA (TD-LFIA) is the test zone system consisting of a combination of two types of inkjet-deposited capture molecules referred to as "mask antigen" and "text antibody", allowing for sensitive turn-on signaling as opposed to the inverse response of conventional competitive LFIAs. The user operation is limited to sample application, followed by direct reading of assay results written in text after approximately 10 min. TD-LFIAs enabled the visual detection of 8-OHdG at concentrations down to 3 ng/mL, which is a 2-3 orders of magnitude lower visual detection limit than that achieved with the corresponding conventional design and is comparable to the existing LFIAs relying on external signal readout equipment. Highly reproducible observer-independent assay performance was confirmed, and the result interpretation is not influenced by sample color and readout timing. Making use of customizable threshold settings for text appearance, a device for semiquantitative assays was developed and successfully applied to the detection of 8-OHdG at four concentration levels (trace, low, medium, and high) in 54 human urine samples within the clinically relevant concentration range. The sensitive and intuitive signaling method of the developed system offers great potential for an alternative competitive LFIA platform suitable for real-world point-of-care testing applications.

Direct competitive immunosensor for Imidacloprid pesticide detection on gold nanoparticle-modified electrodes

A direct competitive immunosensor for the electrochemical determination of Imidacloprid (IMD) pesticide on gold nanoparticle-modified screen-printed carbon electrodes (AuNP-SPCE) is here reported for the first time. Self-obtained specific monoclonal antibodies are immobilized on the AuNP-SPCE taking advantage of the AuNPs biofunctionalization abilities. In our biosensor design, free IMD in the sample competes with IMD conjugated with horseradish peroxidase (IMD-HRP) for the recognition by the antibodies. After that, 3,3',5,5'-Tetramethylbenzidine (TMB) is enzymatically oxidized by HRP, followed by the oxidized TMB reduction back at the surface of the SPCE. This process gives an associated catalytic current (analytical signal) that is inversely proportional to the IMD amount. The main parameters affecting the analytical signal have been optimized, reaching a good precision (repeatability with a RSD of 6%), accuracy (relative error of 6%), stability (up to one month), selectivity and an excellent limit of detection (LOD of 22 pmol L^-1), below the maximum levels allowed by the legislation, with a wide response range (50-10000 pmol L^-1). The detection through antibodies also allows to have an excellent selectivity against other pesticides potentially present in real samples. Low matrix effects were found when analysing IMD in tap water and watermelon samples. The electrochemical immunosensor was also validated with HPLC-MS/MS, the reference method used in official laboratories for IMD analysis, through statistical tests. Our findings make the electrochemical immunosensor as an outstanding method for the rapid and sensitive determination of IMD at the point-of-use.

Comparison of three sample addition methods in competitive and sandwich colloidal gold immunochromatographic assay

Immunochromatographic assays (ICAs) are mainstream point-of-care diagnostic tools in disease control, food safety, and environmental monitoring. However, the important issue pertaining to the influence of sample addition methods on the detection performance of ICAs has not been addressed, and related information is still lacking. Herein, we selected the well-accepted gold nanoparticles (AuNPs) as visual labels. AuNP-based ICA was then used to explore the effects of three sample addition methods (i.e., dry, wet, and insert) on the analytical performance of ICAs by using competitive and sandwich models. Under optimized conditions, the competitive ICA with clenbuterol as an analyte showed a negligible difference (p > 0.05) in the detection performance of the three methods in ideal phosphate buffered saline solution. However, the wet method demonstrated the worst performance in pork samples (p < 0.05). The sandwich ICA strip with human chorionic gonadotropin as an analyte revealed the significantly different analytical performances of the three approaches in phosphate buffer (PB) solution and spiked serum (p < 0.05). Two independent linear correlations were observed with the increase in target concentration. However, for the wet method in the PB solution and serum, the first linear correlation was at a relatively narrow target concentration range, and the second linear correlation was at a wider concentration range compared with those for the dry and insert methods. Our findings demonstrated that sample addition methods slightly influence competitive ICAs (p > 0.05) but remarkably affect sandwich ICAs (p < 0.05). We believe that this study can further explain the differences in detection results for the same target analyte in actual ICA detection. The results may serve as a reference in the rational selection of the appropriate sample addition method for succeeding ICA works.

Quantitative Determination of Acetamiprid in Pollen Based on a Sensitive Enzyme-Linked Immunosorbent Assay

A sensitive biotinylated indirect competitive enzyme-linked immunosorbent assay (Bic-ELISA) was developed to detect acetamiprid pesticides in pollen, based on the heterogeneous coating antigen and biotinylated anti-acetamiprid monoclonal antibody. Under optimized experimental conditions, the detection limit for the Bic-ELISA was 0.17 ng/mL and the linear range was 0.25–25 ng/mL. The cross-reactivities could be regarded as negligible for the biotinylated antibodies with their analogues except for thiacloprid (1.66%). Analyte recoveries for extracts of spiked pollen (camellia pollen, lotus pollen, rape pollen) ranged from 81.1% to 108.0%, with intra-day relative standard deviations (RSDs) of 4.8% to 10.9%, and the average reproducibility was 85.4% to 110.9% with inter-assay and inter-assay RSDs of 6.1% to 11.7%. The results of Bic-ELISA methods for the Taobao’s website samples were largely consistent with HPLC-MS/MS. Therefore, the established Bic-ELISA methods would be conducive to the monitoring of acetamiprid in pollen.

The end user sensor tree: An end-user friendly sensor database

Detailed knowledge regarding sensor based technologies for the detection of food contamination often remains concealed within scientific journals or divided between numerous commercial kits which prevents optimal connectivity between companies and end-users. To overcome this barrier The End user Sensor Tree (TEST) has been developed. TEST is a comprehensive, interactive platform including over 900 sensor based methods, retrieved from the scientific literature and commercial market, for aquatic-toxins, mycotoxins, pesticides and microorganism detection. Key analytical parameters are recorded in excel files while a novel classification system is used which provides, tailor-made, experts' feedback using an online decision tree and database introduced here. Additionally, a critical comparison of reviewed sensors is presented alongside a global perspective on research pioneers and commercially available products. The lack of commercial uptake of the academically popular electrochemical and nanomaterial based sensors, as well as multiplexing platforms became very apparent and reasons for this anomaly are discussed.

A monoclonal antibody-based immunosensor for the electrochemical detection of imidacloprid pesticide

Imidacloprid (IMD) is one of the most used pesticides worldwide as a systemic insecticide as well as for pest control and seed treatment.

Development of immunochromatographic assays for the detection of imidacloprid in soil chemical barrier

A soil chemical barrier is the most important and common way to control termites; fast and on-site detection methods are significant tools to verify pesticide content meeting the standard requirements. In this study, conventional and enhanced immunochromatographic assays (ICAs) containing two test lines (TLs) were developed to semi-quantitatively detect imidacloprid in soil chemical barrier, and detection results were quantified by a smart phone. According to the results, the disappearance concentrations of first TL (TL-1) and second TL (TL-2) in an enhanced ICA and conventional ICA were 5 and 20 ng/mL and 20 and 80 ng/mL with the naked eye. The sensitivity of TL-2 was four times that of TL-1 in both ICAs, consistent with the maximum and minimum concentration differences for imidacloprid in Jiangsu province's "the technical regulation of assay and evaluation on chemical soil barrier of termite prevention treatment in buildings". The results of TLs can be used to judge whether the amount of imidacloprid in soil chemical barrier meets the standard. Enhanced and conventional ICAs were available for further quantitative testing with a smart phone, and the limit of detection (LOD) was 0.74 and 3.17 ng/mL, respectively. Moreover, some soil chemical barrier samples from several areas in Wuxi, Jiangsu province, were used to test by ICAs and high-performance liquid chromatography (HPLC), and the results of ICAs correlated well with HPLC.

An improved detection limit and working range of lateral flow assays based on a mathematical model

The detection limit and working range of lateral flow assays are investigated experimentally and numerically.

Quantum-Dot-Based Lateral Flow Immunoassay for Detection of Neonicotinoid Residues in Tea Leaves

Neonicotinoid insecticides are commonly used for pest control on tea plantations as a result of their broad-spectrum activity. However, neonicotinoid residues released from tea leaves into tea infusions pose a dietary risk to consumers. Therefore, a rapid, sensitive, and reliable on-site detection method for neonicotinoids is needed. We developed a quantum-dot-based fluorescent lateral flow immunochromatographic strip (LFICS) combined with a broad-specific antibody for detection of typical neonicotinoids (imidacloprid, imidaclothiz, and clothianidin), with sensitivities [50% inhibitory concentration (IC₅₀)] of 0.104-0.33 ng/mL and visual detection limits of 0.5-1 ng/mL. The strip assay could be completed in less than 30 min. Using the LFICS to analyze spiked tea samples (green tea, black tea, and oolong tea), the average recovery of the three neonicotinoids ranged between 71 and 111%, with the coefficient of variation below 12%. The results from the LFICS tests for field samples were consistent with results from ultraperformance liquid chromatography-tandem mass spectrometry. The newly developed strip is a useful tool for the on-site detection of neonicotinoid residues in tea.

Lateral Flow Assay Based on Paper-Hydrogel Hybrid Material for Sensitive Point-of-Care Detection of Dengue Virus

Paper-based devices have been broadly used for the point-of-care detection of dengue viral nucleic acids due to their simplicity, cost-effectiveness, and readily observable colorimetric readout. However, their moderate sensitivity and functionality have limited their applications. Despite the above-mentioned advantages, paper substrates are lacking in their ability to control fluid flow, in contrast to the flow control enabled by polymer substrates (e.g., agarose) with readily tunable pore size and porosity. Herein, taking the benefits from both materials, the authors propose a strategy to create a hybrid substrate by incorporating agarose into the test strip to achieve flow control for optimal biomolecule interactions. As compared to the unmodified test strip, this strategy allows sensitive detection of targets with an approximately tenfold signal improvement. Additionally, the authors showcase the potential of functionality improvement by creating multiple test zones for semi-quantification of targets, suggesting that the number of visible test zones is directly proportional to the target concentration. The authors further demonstrate the potential of their proposed strategy for clinical assessment by applying it to their prototype sample-to-result test strip to sensitively and semi-quantitatively detect dengue viral RNA from the clinical blood samples. This proposed strategy holds significant promise for detecting various targets for diverse future applications.

Development of an eco-friendly immunochromatographic test strip and its application in detecting Hg2+ without chelators

The schematic diagram of an eco-friendly immunochromatographic test strip (EFITS) and a competitive immunoreaction on the EFITS.