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

Back to Basics: Unraveling the Fundamentals of Lateral Flow Assays

BACKGROUND

Lateral flow assay (LFA) is a rapid analytical technique that has been implemented as a point-of-care approach for analyte detection. Given the rapid expansion of the use of LFA as a point-of-care testing strategy, LFA development has been subjected to extensive research, which has resulted in upgraded designs and technologies, improving levels of specificity and costs associated with manufacturing. This has allowed LFA to become an important option in rapid testing while maintaining appropriate limits of detection for accurate diagnoses.

CONTENT

This review focuses on the theoretical basis of LFA, its components, formats, multiparametric possibilities, labels, and applications. Also, challenges associated with the technique and possible solutions are explored.

SUMMARY

We explore LFA as a detection technique, its benefits, opportunities for improvement, and applications, and how challenges to its design can be approached.

Sensitive Colorimetric Lateral Flow Assays Enabled by Platinum-Group Metal Nanoparticles with Peroxidase-Like Activities

The last several decades have witnessed the success and popularity of colorimetric lateral flow assay (CLFA) in point-of-care testing. Driven by increasing demand, great efforts have been directed toward enhancing the detection sensitivity of CLFA. Recently, platinum-group metal nanoparticles (PGM NPs) with peroxidase-like activities have emerged as a type of promising colorimetric labels for enhancing the sensitivity of CLFA. By incorporating a simple and rapid post-treatment process, the PGM NP-based CLFAs are orders of magnitude more sensitive than conventional gold nanoparticle-based CLFAs. In this perspective, the study begins with introducing the design, synthesis, and characterization of PGM NPs with peroxidase-like activities. The current techniques for surface modification of PGM NPs are then discussed, followed by operation and optimization of PGM NP-based CLFAs. Afterward, opinions are provided on the social impact of PGM NP-based CLFAs. Lastly, this perspective is concluded with an outlook of future research directions in this emerging field, where the challenges and opportunities are discussed.

Organophosphate pesticide residues in fruits and vegetables in Nigeria: prevalence, environmental impact, and human health implications

Pesticides have become indispensable in modern agriculture, aiding in crop protection, and ensuring food security. However, their extensive use has raised concerns about environmental contamination and human health risks. This manuscript reviews the prevalence of organophosphate pesticide (OPP) use in Nigerian agriculture and explores methods for detecting pesticide residues in fruits and vegetables. Despite the critical role of pesticides in safeguarding crop yields, the lack of regulatory enforcement and monitoring in Nigeria poses significant challenges. The review underscores the importance of understanding the health implications of pesticide residues in food. While acute and sub-chronic health effects of OPP exposure have been studied, there remains a need for a focused review of the long-term impacts, particularly in the context of limited regulatory oversight. Additionally, the manuscript highlights gaps in knowledge regarding the effects of pesticides on biodiversity, ecosystems, and vulnerable populations such as children, pregnant women, and the elderly. Recommendations include longitudinal studies to assess cumulative and delayed health consequences, systematic reporting of poisoning incidents, and routine analysis of food products to ensure safety. By addressing these gaps, a more comprehensive understanding of the consequences of OPP usage in Nigeria can be achieved, facilitating the development of effective risk management strategies to protect both the environment and public health.

SERS Sensors with Bio-Derived Substrates Under the Way to Agricultural Monitoring of Pesticide Residues

Uncontrolled use of pesticides in agriculture leads to negative consequences for the environment, as well as for human and animal health. Therefore, timely detection of pesticides will allow application of measures to eliminate the excess of maximum residue limits and reduce possible negative consequences in advance. Common methods of pesticide analysis suffer from high costs, and are time consuming, and labor intensive. Currently, more attention is being paid to the development of surface-enhanced Raman scattering (SERS) sensors as a non-destructive and highly sensitive tool for detecting various chemicals in agricultural applications. This review focuses on the current developments of biocompatible SERS substrates based on natural materials with unique micro/nanostructures, flexible SERS substrates based on biopolymers, as well as functionalized SERS substrates, which are close to the current needs and requirements of agricultural product quality control and environmental safety assessment. The impact of herbicides on the process of photosynthesis is considered and the prospects for the application of Raman spectroscopy and SERS for the detection of herbicides are discussed.

Highly sensitive SERS-based lateral flow immunoassay of fipronil using bimetallic Au@Ag@Ag nanorods

A bimetallic core-shell-shell nanorods structure with gap-embedded Raman reporter 5,5'-dithio-bis-(2-nitrobenzoic acid) (DTNB) was developed and applied as a SERS-active nanotag in surface-enhanced Raman scattering lateral flow immunoassay (SERS-LFIA) of the insecticide fipronil. Due to the strong SERS signal of the AuDTNB@AgDTNB@AgNRods, fipronil is detected with extremely low detection limit of 4.6 pg/mL. To the best of our knowledge, the proposed technique is the first SERS-LFIA of fipronil, proven to be effective in the selective determination of the target analyte and capable of detecting fipronil in a matrix of food samples (cucumber and apple juice) with recoveries of 97.0-117.0%. Moreover, the applied functionalization of the SERS nanotag with anti-species antibodies has provided a versatile immunoprobe that could improve performance of different LFIAs.

Recent advances in the CRISPR/Cas system-based visual detection method

Currently, various infectious pathogens and bacterial toxins as well as heavy metal pollution pose severe threats to global environmental health and the socio-economic infrastructure. Therefore, there is a pressing need for rapid, sensitive, and convenient visual molecular detection methods. The rapidly evolving detection approach based on clustered regularly interspaced short palindromic repeats (CRISPR)/associated nucleases (Cas) has opened a new frontier in the field of molecular diagnostics. This paper reviews the development of visual detection methods in recent years based on different Cas and analyzes their advantages and disadvantages as well as the challenges of future research. Firstly, different CRISPR/Cas effectors and their working principles in the diagnosis of various diseases are briefly reviewed. Subsequently, the article focuses on the development of visual readout signals in point-of-care testing using laboratory-based CRISPR/Cas technology, including colorimetric, fluorescence, and lateral flow analysis. Finally, the challenges and prospects of visual detection methods based on CRISPR/Cas technology are discussed.

Lateral flow assays: Progress and evolution of recent trends in point-of-care applications

Paper based point-of-care (PoC) detection platforms applying lateral flow assays (LFAs) have gained paramount approval in the diagnostic domain as well as in environmental applications owing to their ease of utility, low cost, and rapid signal readout. It has centralized the aspect of self-evaluation exhibiting promising potential in the last global pandemic era of Covid-19 implementing rapid management of public health in remote areas. In this perspective, the present review is focused towards landscaping the current framework of LFAs along with integration of components and characteristics for improving the assay by pushing the detection limits. The review highlights the synergistic aspects of assay designing, sample enrichment strategies, novel nanomaterials-based signal transducers, and high-end analytical techniques that contribute significantly towards sensitivity and specificity enhancement. Various recent studies are discussed supporting the innovations in LFA systems that focus upon the accuracy and reliability of rapid PoC testing. The review also provides a comprehensive overview of all the possible difficulties in commercialization of LFAs subjecting its applicability to pathogen surveillance, water and food testing, disease diagnostics, as well as to agriculture and environmental issues.

Glyphosate as a Food Contaminant: Main Sources, Detection Levels, and Implications for Human and Public Health

Glyphosate is a broad-spectrum pesticide that has become the most widely used herbicide globally. However, concerns have risen regarding its potential health impacts due to food contamination. Studies have detected glyphosate in human blood and urine samples, indicating human exposure and its persistence in the organism. A growing body of literature has reported the health risks concerning glyphosate exposure, suggesting that the daily intake of contaminated food and water poses a public health concern. Furthermore, countries with high glyphosate usage and lenient regulations regarding food and water contamination may face more severe consequences. In this context, in this review, we examined the literature regarding food contamination by glyphosate, discussed its detection methods, and highlighted its risks to human health.

Microfabrication of engineered Lactococcus lactis biocarriers with genetically programmed immunorecognition probes for sensitive lateral flow immunoassay of antibiotic in milk and lake water

Micro/nanomaterials display considerable potential for increasing the sensitivity of lateral flow immunoassay (LFIA) by acting as 3D carriers for both antibodies and signals. The key to achieving high detection sensitivity depends on the probe's orientation on the material surface and its multivalent biomolecular interactions with targets. Here, we engineer Lactococcus lactis as the bacterial microcarrier (BMC) for a multivalent immunorecognition probe that was genetically programmed to display multifunctional components including a phage-screened single-chain variable fragment (scFv), an enhanced green fluorescent protein (eGFP), and a C-terminal peptidoglycan-binding domain (AcmA) anchored on BMC through the cell wall peptidoglycan. The innovative design of this biocarrier system, which incorporates a lab-on-a-chip microfluidic device, allows for the rapid and non-destructive self-assembly of the multivalent scFv-eGFP-AcmA@BMC probe, in which the 3D structure of BMC with a large peptidoglycan surface area facilitates the precisely orientated attachment and immobilization of scFv-eGFP-AcmA. This leads to a remarkable fluorescence aggregation amplification effect in LFIA, outperforming a monovalent 2D scFv-eGFP-AcmA probe for florfenicol detection. By designing a portable sensing device, we achieved an exceptionally low detection limit of 0.28 pg/mL and 0.21 pg/mL for florfenicol in lake water and milk sample, respectively. The successful microfabrication of this biocarrier holds potential to inspire innovative biohybrid designs for environment and food safety biosensing applications.

Multiplexed Capillary-Flow Driven Immunoassay for Respiratory Illnesses

Multiplexed analysis in medical diagnostics is widely accepted as a more thorough and complete method compared to single-analyte detection. While analytical methods like polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA) exist for multiplexed detection of biomarkers, they remain time-consuming and expensive. Lateral flow assays (LFAs) are an attractive option for point-of-care testing, and examples of multiplexed LFAs exist. However, these devices are limited by spatial resolution of test lines, large sample volume requirements, cross-reactivity, and poor sensitivity. Recent work has developed capillary-flow microfluidic ELISA platforms as a more sensitive alternative to LFAs; however, multiplexed detection on these types of devices has yet to be demonstrated. In the aftermath of the initial SARS-CoV-2 pandemic, the need for rapid, sensitive point-of-care devices has become ever clearer. Moving forward, devices that can distinguish between diseases with similar presenting symptoms would be the ideal home diagnostic. Here, the first example of a multiplexed capillary-flow immunoassay device for the simultaneous detection of multiple biomarkers is reported. From a single sample addition step, the reagents and washing steps required for two simultaneous ELISAs are delivered to spatially separated test strips. Visual results can be obtained in <15 min, and images captured with a smartphone can be analyzed for quantitative data. This device was used to distinguish between and quantify H1N1 hemagglutinin (HA) and SARS-CoV-2 nucleocapsid protein (N-protein). Using this device, analytical detection limits of 840 and 133 pg/mL were obtained for hemagglutinin and nucleocapsid protein, respectively. The presence of one target in the device did not increase the signal on the other test line, indicating no cross-reactivity between the assays. Additionally, simultaneous detection of both N-protein and HA was performed as well as simultaneous detection of N-protein and human C-reactive protein (CRP). Elevated levels of CRP in a patient infected with SARS-CoV-2 have been shown to correlate with more severe outcomes and a greater risk of death as well. To further expand on the simultaneous detection of two biomarkers, CRP and N-protein were detected simultaneously, and the presence of SARS-CoV-2 N-protein did not interfere with the detection of CRP when both targets were present in the sample.

Cas-based bacterial detection: recent advances and perspectives

Persistent bacterial infections pose a formidable threat to global health, contributing to widespread challenges in areas such as food safety, medical hygiene, and animal husbandry. Addressing this peril demands the urgent implementation of swift and highly sensitive detection methodologies suitable for point-of-care testing and large-scale screening. These methodologies play a pivotal role in the identification of pathogenic bacteria, discerning drug-resistant strains, and managing and treating diseases. Fortunately, new technology, the CRISPR/Cas system, has emerged. The clustered regularly interspaced short joint repeats (CRISPR) system, which is part of bacterial adaptive immunity, has already played a huge role in the field of gene editing. It has been employed as a diagnostic tool for virus detection, featuring high sensitivity, specificity, and single-nucleotide resolution. When applied to bacterial detection, it also surpasses expectations. In this review, we summarise recent advances in the detection of bacteria such as Mycobacterium tuberculosis (MTB), methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli (E. coli), Salmonella and Acinetobacter baumannii (A. baumannii) using the CRISPR/Cas system. We emphasize the significance and benefits of this methodology, showcasing the capability of diverse effector proteins to swiftly and precisely recognize bacterial pathogens. Furthermore, the CRISPR/Cas system exhibits promise in the identification of antibiotic-resistant strains. Nevertheless, this technology is not without challenges that need to be resolved. For example, CRISPR/Cas systems must overcome natural off-target effects and require high-quality nucleic acid samples to improve sensitivity and specificity. In addition, limited applicability due to the protospacer adjacent motif (PAM) needs to be addressed to increase its versatility. Despite the challenges, we are optimistic about the future of bacterial detection using CRISPR/Cas. We have already highlighted its potential in medical microbiology. As research progresses, this technology will revolutionize the detection of bacterial infections.

Microfluidic-assisted integrated nucleic acid test strips for POCT

Numerous diseases have posed significant threats to public health, notably the global pandemic of COVID-19, resulting in widespread devastation due to its high infectivity and severity. The nucleic acid lateral flow assay (NALFA) addresses challenges of complexity, cost, and time associated with traditional assays, offering a reliable platform for rapid and precise nucleic acid target detection. NALFA is gaining prominence as a point-of-care testing (POCT) technique, thanks to its user-friendly operation and rapid results. Nevertheless, conventional NALFA relies on specialized technicians and involves labor-intensive steps like DNA extraction and PCR processes, impeding its efficiency. To overcome these limitations, integrating NALFA with microfluidic technology, widely employed in rapid field detection, holds promise. This review comprehensively outlines prevailing strategies for integrating NALFA, encompassing both research initiatives and commercial applications. Addressing the bottleneck of nucleic acid amplification as a rate-limiting step, the review delves into progress in amplification-free NALFA and highlights prevalent signal amplification techniques. Ultimately, the review outlines the future prospect of integrated NALFA development, capturing the technology's evolution and providing valuable insights for academic and commercial endeavors.

Recent Advances in and Applications of Electrochemical Sensors Based on Covalent Organic Frameworks for Food Safety Analysis

The international community has been paying close attention to the issue of food safety as a matter of public health. The presence of a wide range of contaminants in food poses a significant threat to human health, making it vital to develop detection methods for monitoring these chemical contaminants. Electrochemical sensors using emerging materials have been widely employed to detect food-derived contaminants. Covalent organic frameworks (COFs) have the potential for extensive applications due to their unique structure, high surface area, and tunable pore sizes. The review summarizes and explores recent advances in electrochemical sensors modified with COFs for detecting pesticides, antibiotics, heavy metal ions, and other food contaminants. Furthermore, future challenges and possible solutions will be discussed regarding food safety analysis using COFs.

SALAD: Syringe-based Arduino-operated Low-cost Antibody Dispenser

Lateral Flow Assays (LFA) have been one of the most widely adopted technologies in clinical diagnosis over recent years, especially during the COVID-19 pandemic, due to their feasibility, compactness, and rapid readout. However, the precise dispensing of antibodies-a key part of the fabrication process-requires costly line dispenser equipment, which poses a challenge to researchers with limited budgets. This study aims to resolve this key issue by introducing a Syringe-based Arduino-operated Low-cost Antibody Dispenser (SALAD). By utilizing a microneedle, stepper motor-driven syringe pump, and conveyor belt, SALAD can form micro-droplets to create an even band of antibodies. Our evaluation results showed comparable performance between SALAD and a commercialized model - Claremont ALFRD, with SALAD exceeding in affordability and feasibility. SALAD yielded an even signal, uniform bandwidth, and low background noise, yet optimization in the conveyor belt should be considered to enhance stability. With a low manufacturing cost ($200.61) compared to the commercialized models, our model is expected to provide an affordable approach for LFA researchers.

Lateral Flow Assay: A Summary of Recent Progress for Improving Assay Performance

Lateral flow tests are one of the most important types of paper-based point-of-care (POCT) diagnostic tools. It shows great potential as an implement for improving the rapid screening and management of infections in global pandemics or other potential health disorders by using minimally expert staff in locations where no sophisticated laboratory services are accessible. They can detect different types of biomarkers in various biological samples and provide the results in a little time at a low price. An important challenge regarding conventional LFAs is increasing their sensitivity and specificity. There are two main approaches to increase sensitivity and specificity, including assay improvement and target enrichment. Assay improvement comprises the assay optimization and signal amplification techniques. In this study, a summarize of various sensitivity and specificity enhancement strategies with an objective evaluation are presented, such as detection element immobilization, capillary flow rate adjusting, label evolution, sample extraction and enrichment, etc. and also the key findings in improving the LFA performance and solving their limitations are discussed along with numerous examples.

Fungi That Promote Plant Growth in the Rhizosphere Boost Crop Growth

The fungi species dwelling in the rhizosphere of crop plants, revealing functions that endeavor sustainability of the plants, are commonly referred to as 'plant-growth-promoting fungi' (PGPF). They are biotic inducers that provide benefits and carry out important functions in agricultural sustainability. The problem encountered in the agricultural system nowadays is how to meet population demand based on crop yield and protection without putting the environment and human and animal health at risk based on crop production. PGPF including Trichoderma spp., Gliocladium virens, Penicillium digitatum, Aspergillus flavus, Actinomucor elegans, Podospora bulbillosa, Arbuscular mycorrhizal fungi, etc., have proven their ecofriendly nature to ameliorate the production of crops by improving the growth of the shoots and roots of crop plants, the germination of seeds, the production of chlorophyll for photosynthesis, and the abundant production of crops. PGPF's potential mode of action is as follows: the mineralization of the major and minor elements required to support plants' growth and productivity. In addition, PGPF produce phytohormones, induced resistance, and defense-related enzymes to inhibit or eradicate the invasion of pathogenic microbes, in other words, to help the plants while encountering stress. This review portrays the potential of PGPF as an effective bioagent to facilitate and promote crop production, plant growth, resistance to disease invasion, and various abiotic stresses.

Recent Progress in Electrochemical Nano-Biosensors for Detection of Pesticides and Mycotoxins in Foods

Pesticide and mycotoxin residues in food are concerning as they are harmful to human health. Traditional methods, such as high-performance liquid chromatography (HPLC) for such detection lack sensitivity and operation convenience. Efficient, accurate detection approaches are needed. With the recent development of nanotechnology, electrochemical biosensors based on nanomaterials have shown solid ability to detect trace pesticides and mycotoxins quickly and accurately. In this review, English articles about electrochemical biosensors in the past 11 years (2011-2022) were collected from PubMed database, and various nanomaterials are discussed, including noble metal nanomaterials, magnetic metal nanoparticles, metal-organic frameworks, carbon nanotubes, as well as graphene and its derivatives. Three main roles of such nanomaterials in the detection process are summarized, including biomolecule immobilization, signal generation, and signal amplification. The detection targets involve two types of pesticides (organophosphorus and carbamate) and six types of mycotoxins (aflatoxin, deoxynivalenol, zearalenone, fumonisin, ochratoxin A, and patulin). Although significant achievements have been made in the evolution of electrochemical nano-biosensors, many challenges remain to be overcome.

Development of a colloidal gold immunochromatographic test strip for the rapid detection of iprodione

Iprodione is a dicarboximide fungicide that is widely used in agriculture around the world. A reliable and rapid detection method is needed for the on-site monitoring of iprodione residues in a variety of agricultural products. Herein, a colloidal gold immunochromatographic test strip was developed based on a selected coating antigen and a specific monoclonal antibody against iprodione. The particle size of colloidal gold, the preparation technique of the conjugate pad, the composition of the loading buffer, and the extraction solvent were comprehensively optimized for the test strip. A cut-off value of 0.9 mg kg^-1 (50 ng mL^-1) and a visual limit of detection of 0.09 mg kg^-1 (5 ng mL^-1) were achieved in a complex matrix of tobacco. No cross-reactivity was observed for iprodione metabolite and four other widely used pesticides during tobacco growth. Furthermore, the developed colloidal gold immunochromatographic test strip was applied to determine iprodione residues in tobacco samples, and the obtained results were in good agreement with those obtained by liquid chromatography tandem mass spectrometry. Additionally, the test strip was found to be stable afterlong-term storage at 37 °C for two months. The developed colloidal gold immunochromatographic test strip showed excellent accuracy, sensitivity, specificity, and stability, therefore, it is suitable for the rapid detection of iprodione residues in complex matrices.