Calixarene-Based Supramolecular Sensor Array for Pesticide Discrimination

The identification and detection of pesticides is crucial to protecting both the environment and human health. However, it can be challenging to conveniently and rapidly differentiate between different types of pesticides. We developed a supramolecular fluorescent sensor array, in which calixarenes with broad-spectrum encapsulation capacity served as recognition receptors. The sensor array exhibits distinct fluorescence change patterns for seven tested pesticides, encompassing herbicides, insecticides, and fungicides. With a reaction time of just three minutes, the sensor array proves to be a rapid and efficient tool for the discrimination of pesticides. Furthermore, this supramolecular sensing approach can be easily extended to enable real-time and on-site visual detection of varying concentrations of imazalil using a smartphone with a color scanning application. This work not only provides a simple and effective method for pesticide identification and quantification, but also offers a versatile and advantageous platform for the recognition of other analytes in relevant fields.

Copper Oxide Anchored Carbon Nanofibers: A Versatile Platform for Multiplex Detection of Antibiotics, Heavy Metals and Pesticides

Electrochemical sensors offer promising prospects for real-time pollutant monitoring. In this study, copper oxide-dispersed graphitic carbon nanofibers (CuO-CNFs) grown via chemical vapour deposition were employed as a robust platform for detecting a variety of environmental pollutants. This array-based sensor adeptly identifies three different classes of analytes, i. e., antibiotics (chloramphenicol (CP) and tylosin tartrate (TT)), heavy metals (cadmium (Cd) and lead (Pb)), and pesticides (quinalphos (QP) and imidacloprid (IP)). Electron collection is facilitated by a glassy carbon electrode, while various physico-electrochemical methods delve into the properties of CuO-CNFs. The CuO-CNF-modified GCE array rapidly discerns (<15 sec) a broad linear range: 1-20 ppm for CP, 1-13.33 ppm for TT, 0.66-11.66 ppm for Cd, 20-33.33 ppm for Pb, 1.6-11.6 ppm for QP, and 5-25 ppm for IP, boasting quantification limits of 1.0, 1.0, 0.66, 20.0, 1.6, and 5.0 ppm for CP, TT, Cd, Pb, QP, and IP, respectively. Notably, this sensor achieves simultaneous identification of mixed analytes, including CP and TT, Cd and Pb, and QP and IP, within real tap water. Furthermore, the electrochemical sensor exhibits robustness; heightened sensitivity, selectivity, and stability; a swift response; and impressive reproducibility in detecting CP, TT, Cd, Pb, QP, and IP within aqueous samples. Consequently, this array-based electrochemical sensor has emerged as a rapid and simultaneous detection tool for diverse pollutant residues in surface and groundwater samples.

Electrochemical sensors of neonicotinoid insecticides residues in food samples: From structure to analysis

Most food samples are detected positive for neonicotinoid insecticides, posing a severe threat to human health. Electrochemical sensors have been proven effective for monitoring the residues to guarantee food safety, but there needs to be more review to conclude the development status comprehensively. On the other hand, various modified materials were emphasized to improve the performance of electrochemical sensors in relevant reviews, rather than the reasons why they were selected. Therefore, this paper reviewed the electrochemical sensors of neonicotinoid insecticides according to bases and strategies. The fundamental basis is the molecular structure of neonicotinoid insecticides, which was disassembled into four functional groups: nitro group, saturated nitrogen ring system, aromatic heterocycle and chlorine substituent. Their relationships were established with strategies including direct sensing, enzyme sensors, aptasensors, immunosensors, and sample pretreatment, respectively. It is hoped to provide a reference for the effective design of electrochemical sensors for small molecule compounds.

High sensitivity electrochemical detection of ultra-trace imidacloprid in fruits and vegetables using a Fe-rich FeCoNi-MOF

High sensitivity and ultra-trace detection of imidacloprid are important and challenging in the field of food. In this study, we prepared a Fe-rich FeCoNi-MOF in-situ modified nickel foam working electrode by one-step hydrothermal method, and achieved a highly sensitive detection of the imidacloprid. The characterization techniques confirmed that Fe-rich FeCoNi-MOF had excellent crystallinity, tighter structure, and exposed rich active sites. The detection results showed that Fe-rich FeCoNi-MOF electrochemical sensor had a minimum detection limit of 0.04 pmol/L (100 times lower than that of the bioelectrochemical sensors), a wide response range (1 pmol/L-120 μmol/L), and high sensitivity (124 μA pmol/L^-1 cm^-2). These advantages of the electrochemical sensor were revealed theoretically by the valence change of active metal and the first principle calculation. Lastly, the Fe-rich FeCoNi-MOF electrochemical sensor was applied to detect imidacloprid in apple, fresh tea leaves, tomato, cucumber, and had an excellent recovery of 98-102.8 %.

Enhancement of the sensing performance and stability of a MOF based-molecularly imprinted polymer by utilizing dual-ligands and triethanolamine catalysis

In this work, a terbium MOF-based molecularly imprinted polymer (Tb-MOF@SiO₂@MIP) was prepared using two ligands as organic linkers and triethanolamine (TEA) as a catalyst to improve the sensing performance and stability of the fluorescence sensors. The obtained Tb-MOF@SiO₂@MIP was then characterized using a transmission electron microscope (TEM), energy dispersive spectroscopy (EDS) Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). The results revealed that Tb-MOF@SiO₂@MIP was successfully synthesized with a thin imprinted layer of 76 nm. The synthesized Tb-MOF@SiO₂@MIP maintained 96% of its original fluorescence intensity after 44 days in aqueous environments because of appropriate coordination models between the imidazole ligands as a nitrogen donor and Tb (Ⅲ). Furthermore, TGA analysis results indicated that an increase in the thermal stability of Tb-MOF@SiO₂@MIP was attributed to the thermal barrier from a MIP layer. The Tb-MOF@SiO₂@MIP sensor responded well to the addition of imidacloprid (IDP) in the range of 2.07-150 ng mL^-1 with a low detection limit of 0.67 ng mL^-1. In vegetable samples, the sensor can quickly detect IDP levels with the average recovery ranging from 85.10 to 99.85% and RSD values ranging from 0.59 to 5.82%. The UV-vis absorption spectrum and density functional theory analysis results revealed that the inner filter effect and dynamic quenching process both contributed to the sensing process of Tb-MOF@SiO₂@MIP.

Analytical Techniques for the Characterization and Quantification of Monoclonal Antibodies

Monoclonal antibodies (mAbs) are a fast-growing class of biopharmaceuticals. They are widely used in the identification and detection of cell makers, serum analytes, and pathogenic agents, and are remarkably used for the cure of autoimmune diseases, infectious diseases, or malignancies. The successful application of therapeutic mAbs is based on their ability to precisely interact with their appropriate target sites. The precision of mAbs rely on the isolation techniques delivering pure, consistent, stable, and safe lots that can be used for analytical, diagnostic, or therapeutic applications. During the creation of a biologic, the key quality features of a particular mAb, such as structure, post-translational modifications, and activities at the biomolecular and cellular levels, must be characterized and profiled in great detail. This implies the requirement of powerful state of the art analytical techniques for quality control and characterization of mAbs. Until now, various analytical techniques have been developed to characterize and quantify the mAbs according to the regulatory guidelines. The present review summarizes the major techniques used for the analyses of mAbs which include chromatographic, electrophoretic, spectroscopic, and electrochemical methods in addition to the modifications in these methods for improving the quality of mAbs. This compilation of major analytical techniques will help students and researchers to have an overview of the methodologies employed by the biopharmaceutical industry for structural characterization of mAbs for eventual release of therapeutics in the drug market.

Pesticides monitoring in biological fluids: Mapping the gaps in analytical strategies

Pesticides play a key-role in the development of the agrifood sector allowing controlling pest growth and, thus, improving the production rates. Pesticides chemical stability is responsible of their persistency in environmental matrices leading to bioaccumulation in animal tissues and hazardous several effects on living organisms. The studies regarding long-term effects of pesticides exposure and their toxicity are still limited to few studies focusing on over-exposed populations, but no extensive dataset is currently available. Pesticides biomonitoring relies mainly on chromatographic techniques coupled with mass spectrometry, whose large-scale application is often limited by feasibility constraints (costs, time, etc.). On the contrary, chemical sensors allow rapid, in-situ screening. Several sensors were designed for the detection of pesticides in environmental matrices, but their application in biological fluids needs to be further explored. Aiming at contributing to the implementation of pesticides biomonitoring methods, we mapped the main gaps between screening and chromatographic methods. Our overview focuses on the recent advances (2016-2021) in analytical methods for the determination of commercial pesticides in human biological fluids and provides guidelines for their application.

Comparison of Chemiluminescence Enzyme Immunoassay (Cl-ELISA) with Colorimetric Enzyme Immunoassay (Co-ELISA) for Imidacloprid Detection in Vegetables

Imidacloprid is one of the most commonly used insecticides for managing pests, thus, improving the quality and yield of vegetables. The abuse/misuse of imidacloprid contaminates the environment and threatens human health. To reduce the risk, a colorimetric enzyme-linked immunoassay assay (Co-ELISA) and chemiluminescence enzyme-linked immunoassay assay (Cl-ELISA) were established to detect imidacloprid residues in vegetables. The linear range of Co-ELISA ranged between 1.56 μg/L and 200 μg/L with a limit of detection (LOD) of 1.56 μg/L. The values for Cl-ELISA were 0.19 μg/L to 25 μg/L with an LOD of 0.19 μg/L, which are lower than those of Co-ELISA. Fortifying Chinese cabbage, cucumber, and zucchini with imidacloprid at 10, 50, and 100 μg/L yielded recoveries between 81.7 and 117.6% for Co-ELISA and at 5, 10, and 20 µg/L yielded recoveries range from 69.7 to 120.6% for Cl-ELISA. These results indicate that Cl-ELISA has a high sensitivity and a rapid detection time, saving cost (antigen and antibody concentrations) and serving as a more efficient model for the rapid detection of imidacloprid residue.

Recent Advancements in Electrochemical Biosensors for Monitoring the Water Quality

The release of chemicals and microorganisms from various sources, such as industry, agriculture, animal farming, wastewater treatment plants, and flooding, into water systems have caused water pollution in several parts of our world, endangering aquatic ecosystems and individual health. World Health Organization (WHO) has introduced strict standards for the maximum concentration limits for nutrients and chemicals in drinking water, surface water, and groundwater. It is crucial to have rapid, sensitive, and reliable analytical detection systems to monitor the pollution level regularly and meet the standard limit. Electrochemical biosensors are advantageous analytical devices or tools that convert a bio-signal by biorecognition elements into a significant electrical response. Thanks to the micro/nano fabrication techniques, electrochemical biosensors for sensitive, continuous, and real-time detection have attracted increasing attention among researchers and users worldwide. These devices take advantage of easy operation, portability, and rapid response. They can also be miniaturized, have a long-life span and a quick response time, and possess high sensitivity and selectivity and can be considered as portable biosensing assays. They are of special importance due to their great advantages such as affordability, simplicity, portability, and ability to detect at on-site. This review paper is concerned with the basic concepts of electrochemical biosensors and their applications in various water quality monitoring, such as inorganic chemicals, nutrients, microorganisms' pollution, and organic pollutants, especially for developing real-time/online detection systems. The basic concepts of electrochemical biosensors, different surface modification techniques, bio-recognition elements (BRE), detection methods, and specific real-time water quality monitoring applications are reviewed thoroughly in this article.

Towards Development of Molecularly Imprinted Electrochemical Sensors for Food and Drug Safety: Progress and Trends

Due to their advantages of good flexibility, low cost, simple operations, and small equipment size, electrochemical sensors have been commonly employed in food safety. However, when they are applied to detect various food or drug samples, their stability and specificity can be greatly influenced by the complex matrix. By combining electrochemical sensors with molecular imprinting techniques (MIT), they will be endowed with new functions of specific recognition and separation, which make them powerful tools in analytical fields. MIT-based electrochemical sensors (MIECs) require preparing or modifying molecularly imprinted polymers (MIPs) on the electrode surface. In this review, we explored different MIECs regarding the design, working principle and functions. Additionally, the applications of MIECs in food and drug safety were discussed, as well as the challenges and prospects for developing new electrochemical methods. The strengths and weaknesses of MIECs including low stability and electrode fouling are discussed to indicate the research direction for future electrochemical sensors.

Fabrication of Fragment Antibody–Enzyme Complex as a Sensing Element for Immunosensing

Antibody–enzyme complexes (AECs) are ideal molecular recognition elements for immunosensing applications. One molecule possesses both a binding ability to specific targets and catalytic activity to gain signals, particularly oxidoreductases, which can be integrated into rapid and sensitive electrochemical measurements. The development of AECs using fragment antibodies rather than intact antibodies, such as immunoglobulin G (IgG), has attracted attention for overcoming the ethical and cost issues associated with the production of intact antibodies. Conventionally, chemical conjugation has been used to fabricate AECs; however, controlling stoichiometric conjugation using this method is difficult. To prepare homogeneous AECs, methods based on direct fusion and enzymatic conjugation have been developed, and more convenient methods using Catcher/Tag systems as coupling modules have been reported. In this review, we summarize the methods for fabricating AECs using fragment antibodies developed for sensing applications and discuss the advantages and disadvantages of each method.

Applications of electrochemical biosensors based on functional antibody-modified screen-printed electrodes: a review

The detection of biomolecular analytes is of great importance in clinical, environmental, and argo-food areas, among which the electrochemical methodology is attracting much attention. In particular, screen-printed electrode (SPE)-based sensing applications have exhibited potential possibility for on-site detection, especially for fast clinical biomarker detection, since they provide a miniaturized but robust and portable electrode detection system. In this context, we focused on the modification of SPE with functional antibodies to improve the electrochemical detection performance in versatile sensing applications, particularly for COVID-19 detection. These antibodies were immobilized onto the electrode surface via various methodologies, through which the powerful potential from the modification of SPE was revealed. Finally, more novel and excellent works on the biomolecular modification of SPE and the prospects of this technology from its state-of-art status to commercialization are previewed and future perspectives in this field are mentioned.

Monoclonal Antibody-Based Immunosensor for the Electrochemical Detection of Chlortoluron Herbicide in Groundwaters

Chlortoluron (3-(3-chloro-p-tolyl)-1,1-dimethyl urea) is an herbicide widely used in substitution to isoproturon to control grass weed in wheat and barley crops. Chlortoluron has been detected in groundwaters for more than 20 years; and dramatic increases in concentrations are observed after intense rain outbreaks. In this context; we developed an immunosensor for the determination of chlortoluron based on competitive binding of specific monoclonal antibodies on chlortoluron and immobilized biotinylated chlortoluron; followed by electrochemical detection on screen-printed carbon electrodes. The optimized immunosensor exhibited a logarithmic response in the range 0.01-10 µg·L-1; with a calculated detection limit (LOD) of 22.4 ng·L-1; which is below the maximum levels allowed by the legislation (0.1 µg·L-1). The immunosensor was used for the determination of chlortoluron in natural groundwaters, showing the absence of matrix effects.

Facile and Low-Cost SPE Modification Towards Ultra-Sensitive Organophosphorus and Carbamate Pesticide Detection in Olive Oil

Despite the fact that a considerable amount of effort has been invested in the development of biosensors for the detection of pesticides, there is still a lack of a simple and low-cost platform that can reliably and sensitively detect their presence in real samples. Herein, an enzyme-based biosensor for the determination of both carbamate and organophosphorus pesticides is presented that is based on acetylcholinesterase (AChE) immobilized on commercially available screen-printed carbon electrodes (SPEs) modified with carbon black (CB), as a means to enhance their conductivity. Most interestingly, two different methodologies to deposit the enzyme onto the sensor surfaces were followed; strikingly different results were obtained depending on the family of pesticides under investigation. Furthermore, and towards the uniform application of the functionalization layer onto the SPEs’ surfaces, the laser induced forward transfer (LIFT) technique was employed in conjunction with CB functionalization, which allowed a considerable improvement of the sensor’s performance. Under the optimized conditions, the fabricated sensors can effectively detect carbofuran in a linear range from 1.1 × 10⁻⁹ to 2.3 × 10⁻⁸ mol/L, with a limit of detection equal to 0.6 × 10⁻⁹ mol/L and chlorpyrifos in a linear range from 0.7 × 10⁻⁹ up to 1.4 × 10⁻⁸ mol/L and a limit of detection 0.4 × 10⁻⁹ mol/L in buffer. The developed biosensor was also interrogated with olive oil samples, and was able to detect both pesticides at concentrations below 10 ppb, which is the maximum residue limit permitted by the European Food Safety Authority.

Advances in immunosensor technology

In recent years, advances in immunosensor device fabrication have significantly expanded the use of this technology in a broad range of applications including clinical diagnosis, food analysis, quality control, environmental studies and industrial monitoring. The most important aspect in fabrication is to obtain a design that provides a low detection limit. The utilization of nanomaterials as a label, catalyst and biosensing transducer is, perhaps, the most popular approach in ultrasensitive devices. This chapter reviews recent advances in immunosensor fabrication and summarizes the most recent studies. Strategies employed to significantly improve sensitivity and specificity of immunosensor technology and the advantages and limitations thereof are explored.

A sensitive immunoassay based on fluorescence resonance energy transfer from up-converting nanoparticles and graphene oxide for one-step detection of imidacloprid

In this study, a fluorescence resonance energy transfer (FRET) immunoassay based on graphene oxide (GO) and up-converting nanoparticles (UCNPs) was established for rapid detection of imidacloprid, a commonly-used insecticide. Under 980 nm near-infrared light excitation, emission of UCNPs at 542 nm can be absorbed by the energy acceptor GO. The carboxyl-functionalized GO and UCNPs were coupled with competitive antigen and antibody against imidacloprid. After optimization, the FRET immunoassay showed a wide detection range of 0.08-50 ng/mL to imidacloprid, with cross-reaction toward other three neonicotinoids including imidaclothiz (74.4%), thiacloprid (36.9%) and clothianidin (31.9%). The average recoveries of spiked water, Chinese cabbage, cucumber, honey and tea samples were 76.8%-101.8%. The accuracy and reliability of the FRET immunoassay were verified by UPLC-MS/MS with a good correlation (R² = 0.9816). In a summary, this study provides a sensitive and one-step method for monitoring imidacloprid residue in food and environmental samples within 1 h.

Rapid on-site and naked-eye detection of common nitro pesticides with ionic liquids

Rapid 'in-field' detection of environmentally hazardous organophosphorus and nitro-containing pesticides is highly essential due to the lethal effects caused by the inhibition of the activity of acetylcholinesterase (AChE). In our present study, we demonstrate a novel sensing approach for the simultaneous analysis of five widely used pesticides (methyl parathion, pendimethalin, dicloran, trifluralin, and PCNB) based on the Meisenheimer complex formation between polynitro aromatic compounds (pesticides) and a nucleophile. This colorimetric determination of pesticides involves the use of an ionic liquid, tetrabutylammonium hydroxide (TBAOH), as the nucleophile, which is titrated against different concentrations of pesticides. The addition of TBAOH to the solutions of pesticides results in the formation of intensely colored complexes, which are visualized using UV-vis and NMR spectroscopies allowing the identification of new bands and peaks corresponding to the formation of Meisenheimer complexes. The limit of detection (LOD) for targeted pesticides was found to be in the range of 0.67-10 μM. Furthermore, the practical application of this method is demonstrated by developing different paper-based sensors. Therefore, the strategy proposed here not only serves as a valuable tool that allows unskilled people to detect hazardous pesticides in agricultural products 'on-site' but also offers a fast and convenient protocol for the identification of dangerous nitro-containing polyaromatic groups like nitro explosives.

Electrochemical (Bio)Sensors for Pesticides Detection Using Screen-Printed Electrodes

Pesticides are among the most important contaminants in food, leading to important global health problems. While conventional techniques such as high-performance liquid chromatography (HPLC) and mass spectrometry (MS) have traditionally been utilized for the detection of such food contaminants, they are relatively expensive, time-consuming and labor intensive, limiting their use for point-of-care (POC) applications. Electrochemical (bio)sensors are emerging devices meeting such expectations, since they represent reliable, simple, cheap, portable, selective and easy to use analytical tools that can be used outside the laboratories by non-specialized personnel. Screen-printed electrodes (SPEs) stand out from the variety of transducers used in electrochemical (bio)sensing because of their small size, high integration, low cost and ability to measure in few microliters of sample. In this context, in this review article, we summarize and discuss about the use of SPEs as analytical tools in the development of (bio)sensors for pesticides of interest for food control. Finally, aspects related to the analytical performance of the developed (bio)sensors together with prospects for future improvements are discussed.

A portable pencil-like immunosensor for point-of-care testing of inflammatory biomarkers

Portable devices for immunoassays are in high demand for point-of-care testing (POCT) of biomarkers. Here, we report a robust portable pencil-like immunosensor (PPS) platform for the determination of three inflammatory biomarkers including interleukin-6 (IL-6), procalcitonin (PCT), and C-reactive protein (CRP) in human serum samples. The PPS platform is composed of a unique pencil-like optical-fiber-based sensor, a reagent strip consisting of a series of pencil-cap-like wells, and a battery-powered photon counting detector for recording chemiluminescence. The PPS probe moves from well to well with a plug-into/out approach and goes through the immunoassay steps. Each fiber probe in the PPS platform can be sequentially used in up to 10 assays by simply propelling the intact probe out of the pencil body. The PPS platform is well-integrated into a portable suitcase-like device (32 cm × 23 cm × 11 cm) and is only 3 kg in weight. The sensor has good repeatability and can maintain 90% response after 14 days of storage at room temperature, showing its ability for assays in the field. The good linear relationship and efficient dynamic range with a limit-of-detection (LOD) of 1.05 pg/mL for IL-6, 10.64 pg/mL for PCT, and 29.40 ng/mL for CRP are obtained. The assay results are compared with clinical methods, and the findings confirm the high accuracy and precision of the proposed method. The proposed PPS platform is versatile and operable with minimal instruments and technical skills and simplifies the process of immune analysis, thus has great prospects for POCT of biomarkers. Graphical abstract.

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.