Origami multiple paper-based electrochemical biosensors for pesticide detection

A review of smart electrochemical devices for pesticide detection in agricultural food and runoff contaminants

In the evolving field of food and agriculture, pesticide utilization is inevitable for food production and poses an increasing threat to the ecosystem and human health. This review systematically investigates and provides a comprehensive overview of recent developments in smart electrochemical devices for detecting pesticides in agricultural food and runoff contaminants. The focus encompasses recent progress in lab-scale and portable electrochemical sensors, highlighting their significance in agricultural pesticide monitoring. This review compares these sensors comprehensively and provides a scientific guide for future sensor development for infield agricultural pesticide monitoring and food safety. Smart devices address challenges related to power consumption, low cost, wearability, and portability, contributing to the advancement of agricultural sustainability. By elucidating the intricate details of these smart devices, this review offers a comprehensive discussion and roadmap for future research aimed at cost-effective, flexible, and smart handy devices, including novel electrocatalysts, to foster the development of next-generation agricultural sensor technology, opportunity and future direction for food security.

Basic research for identification and classification of organophosphorus pesticides in water based on ultraviolet-visible spectroscopy information

In this study, the goal was to develop a method for detecting and classifying organophosphorus pesticides (OPPs) in bodies of water. Sixty-five samples with different concentrations were prepared for each of the organophosphorus pesticides, namely chlorpyrifos, acephate, parathion-methyl, trichlorphon, dichlorvos, profenofos, malathion, dimethoate, fenthion, and phoxim, respectively. Firstly, the spectral data of all the samples was obtained using a UV-visible spectrometer. Secondly, five preprocessing methods, six manifold learning methods, and five machine learning algorithms were utilized to build detection models for identifying OPPs in water bodies. The findings indicate that the accuracy of machine learning models trained on data preprocessed using convolutional smoothing + first-order derivatives (SG + FD) outperforms that of models trained on data preprocessed using other methods. The backpropagation neural network (BPNN) model exhibited the highest accuracy rate at 99.95%, followed by the support vector machine (SVM) and convolutional neural network (CNN) models, both at 99.92%. The extreme learning machine (ELM) and K-nearest neighbors (KNN) models demonstrated accuracy rates of 99.84% and 99.81%, respectively. Following the application of a manifold learning algorithm to the full-wavelength data set for the purpose of dimensionality reduction, the data was then visualized in the first three dimensions. The results demonstrate that the t-distributed domain embedding (t-SNE) algorithm is superior, exhibiting dense clustering of similar clusters and clear classification of dissimilar ones. SG + FD-t-SNE-SVM ranks highest among the feature extraction models in terms of performance. The feature extraction dimension was set to 4, and the average classification accuracy was 99.98%, which slightly improved the prediction performance over the full-wavelength model. As shown in this study, the ultraviolet-visible (UV-visible) spectroscopy system combined with the t-SNE and SVM algorithms can effectively identify and classify OPPs in waterbodies.

Paper-Based Electrochemical (Bio)Sensors for the Detection of Target Analytes in Liquid, Aerosol, and Solid Samples

The last decade has been incredibly fruitful in proving the multifunctionality of paper for delivering innovative electrochemical (bio)sensors. The paper material exhibits unprecedented versatility to deal with complex liquid matrices and facilitate analytical detection in aerosol and solid phases. Such remarkable capabilities are feasible by exploiting the intrinsic features of paper, including porosity, capillary forces, and its easy modification, which allow for the fine designing of a paper device. In this review, we shed light on the most relevant paper-based electrochemical (bio)sensors published in the literature so far to identify the smart functional roles that paper can play to bridge the gap between academic research and real-world applications in the biomedical, environmental, agrifood, and security fields. Our analysis aims to highlight how paper's multifarious properties can be artfully harnessed for breaking the boundaries of the most classical applications of electrochemical (bio)sensors.

Multifunctional Metal-Organic Frameworks Driven Three-Dimensional Folded Paper-Based Microfluidic Analysis Device for Chlorpyrifos Detection

Chlorpyrifos (CPF) residues in food pose a serious threat to ecosystems and human health. Herein, we propose a three-dimensional folded paper-based microfluidic analysis device (3D-μPAD) based on multifunctional metal-organic frameworks, which can achieve rapid quantitative detection of CPF by fluorescence-colorimetric dual-mode readout. Upconversion nanomaterials were first coupled with a bimetal organic framework possessing peroxidase activity to create a fluorescence-quenched nanoprobe. After that, the 3D-μPAD was finished by loading the nanoprobe onto the paper-based detection zone and spraying it with a color-developing solution. With CPF present, the fluorescence intensity of the detection zone gradually recovers, the color changes from colorless to blue. This showed a good linear relationship with the concentration of CPF, and the limits of detection were 0.028 (fluorescence) and 0.043 (colorimetric) ng/mL, respectively. Moreover, the 3D-μPAD was well applied in detecting real samples with no significant difference compared with the high-performance liquid chromatography method. We believe it has huge potential for application in the on-site detection of food hazardous substance residues.

Sustainable Sensing with Paper Microfluidics: Applications in Health, Environment, and Food Safety

This manuscript offers a concise overview of paper microfluidics, emphasizing its sustainable sensing applications in healthcare, environmental monitoring, and food safety. Researchers have developed innovative sensing platforms for detecting pathogens, pollutants, and contaminants by leveraging the paper's unique properties, such as biodegradability and affordability. These portable, low-cost sensors facilitate rapid diagnostics and on-site analysis, making them invaluable tools for resource-limited settings. This review discusses the fabrication techniques, principles, and applications of paper microfluidics, showcasing its potential to address pressing challenges and enhance human health and environmental sustainability.

Rapid and specific detection of thiabendazole: enzymatic digestion-enabled fluorescent aptasensor

Thiabendazole, a widely used broad-spectrum fungicide in agriculture, poses risks to human health. To monitor its presence in water, we propose a fluorescent aptasensor utilizing Escherichia coli exonuclease I (Exo I). The findings demonstrate a linear correlation between thiabendazole concentrations and digestion percentage, with a detection limit (LOD) exceeding 1 µM and a determination coefficient (R2) of 0.959. This aptamer-based fluorescence spectroscopy detection system holds promise for a rapid, specific, and sensitive analysis of thiabendazole in environmental waters and food matrices.

Herbicide detection: A review of enzyme- and cell-based biosensors

Herbicides are the most widely used class of pesticides in the world. Their intensive use raises the question of their harmfulness to the environment and human health. These pollutants need to be detected at low concentrations, especially in water samples. Commonly accepted analytical techniques (HPLC-MS, GC-MS, ELISA tests) are available, but these highly sensitive and time-consuming techniques suffer from high cost and from the need for bulky equipment, user training and sample pre-treatment. Biosensors can be used as complementary early-warning systems that are less sensitive and less selective. On the other hand, they are rapid, inexpensive, easy-to-handle and allow direct detection of the sample, on-site, without any further step other than dilution. This review focuses on enzyme- and cell- (or subcellular elements) based biosensors. Different enzymes (such as tyrosinase or peroxidase) whose activity is inhibited by herbicides are presented. Photosynthetic cells such as algae or cyanobacteria are also reported, as well as subcellular elements (thylakoids, chloroplasts). Atrazine, diuron, 2,4-D and glyphosate appear as the most frequently detected herbicides, using amperometry or optical transduction (mainly based on chlorophyll fluorescence). The recent new WSSA/HRAC classification of herbicides is also included in the review.

Smartphone-integrated paper-based sensing platform for the visualization and quantitative detection of pymetrozine

Pymetrozine (PYM) is an effective pyridine insecticide for controlling aphids, while its residues pose a serious threat to human health. Herein, a europium complex (Eu-DBPA, DBPA represents deprotonated 2,5-dibromoterephthalic acid ligand) probe was prepared for the detection of PYM via fluorescence quenching. The detection process has the advantages of short response time (2 min), wide linear range (0-4 and 4-45 mg/kg) and low detection limit (2.2 μg/kg). Furthermore, a portable detection platform was designed by integrating Eu-DBPA-based paper strip with smartphone and applied for the visual detection of PYM in real cucumber, tomato, cabbage and apple samples, obtaining satisfactory recovery (99.00 %-107.00 %) and low standard deviation (RSD < 3.4 %). In addition, a logic gate device was designed to simplify the detection process. The smartphone-integrated paper-based probe detection platform provides a new strategy for intelligent and online identification of hazards in environmental and biological samples.

Self-assembled C-Ag hybrid nanoparticle on nanoporous GaN enabled ultra-high enhancement factor SERS sensor for sensitive thiram detection

Considering pesticide residues cause significant harm to public health and the environment, developing a simple, sensitive, and reliable approach to pesticide residue detection to address this issue is necessary. In this study, an ultrasensitive and reliable surface-enhanced Raman scattering (SERS) sensor was developed using cetylpyridinium chloride as a protecting and reducing agent for the in situ synthesis and self-assembly of C-Ag nanoparticles on nanoporous GaN for the quantitative detection of thiram. A systematic investigation of the performance of the SERS sensor revealed that the SERS sensor delivered a limit of detection (LOD) of 10-14 M and an enhancement factor of up to 1.80 × 1011 with reasonable uniformity and reproducibility, with the stability of the SERS sensor demonstrated via long-term storage for up to 22 weeks in air. The enhancement mechanism of the SERS sensor was verified using a finite-difference time-domain simulation. The SERS sensor successfully detected thiram in real samples with an LOD of 10-10 M. Hence, this study provides an effective platform for monitoring food safety and the environment.

Bifunctional fluorescent molecularly imprinted resin based on carbon dot for selective detection and enrichment of 2,4-dichlorophenoxyacetic acid in lettuce

The work provided a method for synthesizing a simple fluorescent molecularly imprinted polymer by surface-initiated atom transfer radical polymerization (SI-ATRP) and its application in real sample. Poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) microspheres were selected as a matrix, 4-vinylpyridine, ethylene glycol dimethacrylate, 2,4-dichlorophenoxyacetic acid (2,4-D) as functional monomer, cross-linker and template molecule, respectively, to fabricate MAR@MIP with core-shell structure. For comparison, carbon dot (CD) as a fluorescence source was synthesized with o-phenylenediamine and tryptophan as precursors via hydrothermal method and integrated into MIP to acquire MAR@CD-MIP. MAR@CD-NIP was also prepared without adding the template molecule. The adsorption capacity of MAR@CD-MIP reached 104 mg g-1 for 2,4-D, which was higher than that of MAR@MIP (60 mg g-1). However, the adsorption capacity of MAR@CD-NIP was only 13.2 mg g-1. The linear range of fluorescence detection for 2,4-D was 18-72 μmol/L, and the limit of detection (LOD) was 0.35 μmol/L. The fluorescent MAR@CD-MIP was successfully applied in enrichment of lettuce samples. The recoveries of the three spiked concentrations of 2,4-D in lettuce were tested by fluorescence spectrophotometry and ranged in 97.3-101.7 %. Meanwhile, the results were also verified by HPLC. As a result, bi-functional molecularly imprinted resin was successfully fabricated to detect and enrich 2,4-D in real samples, and exhibited good selectivity, sensitivity and great application prospect in food detection.

OriPlex: Origami-enabled multiplexed detection of respiratory pathogens

Origami biosensors leverage paper foldability to develop total analysis systems integrated in a single piece of paper. This capability can also be utilized to incorporate additional features that would be difficult to achieve with rigid substrates. In this article, we report a new design for 3D origami biosensors called OriPlex, which leverages the foldability of filter paper for the multiplexed detection of bacterial pathogens. OriPlex immunosensors detect pathogens by folding nanoparticle reservoirs containing different types of nanoprobes. This releases antibody-coated nanoparticles in a central channel where targets are captured through physical interactions. The OriPlex concept was demonstrated by detecting the respiratory pathogens Pseudomonas aeruginosa (PA) and Klebsiella pneumoniae (KP) with a limit of detection of 3.4·103 cfu mL-1 and 1.4·102 cfu mL-1, respectively, and with a turn-around time of 25 min. Remarkably, the OriPlex biosensors allowed the multiplexed detection of both pathogens spiked into real bronchial aspirate (BAS) samples at a concentration of 105 cfu mL-1 (clinical infection threshold), thus demonstrating their suitability for diagnosing lower tract respiratory infections. The results shown here pave the way for implementing OriPlex biosensors as a screening test for detecting superbugs requiring personalized antibiotics in suspected cases of nosocomial pneumonia.

Extremozyme-Based Biosensors for Environmental Pollution Monitoring: Recent Developments

Extremozymes combine high specificity and sensitivity with the ability to withstand extreme operational conditions. This work presents an overview of extremozymes that show potential for environmental monitoring devices and outlines the latest advances in biosensors utilizing these unique molecules. The characteristics of various extremozymes described so far are presented, underlining their stability and operational conditions that make them attractive for biosensing. The biosensor design is discussed based on the detection of photosynthesis-inhibiting herbicides as a case study. Several biosensors for the detection of pesticides, heavy metals, and phenols are presented in more detail to highlight interesting substrate specificity, applications or immobilization methods. Compared to mesophilic enzymes, the integration of extremozymes in biosensors faces additional challenges related to lower availability and high production costs. The use of extremozymes in biosensing does not parallel their success in industrial applications. In recent years, the "collection" of recognition elements was enriched by extremozymes with interesting selectivity and by thermostable chimeras. The perspectives for biosensor development are exciting, considering also the progress in genetic editing for the oriented immobilization of enzymes, efficient folding, and better electron transport. Stability, production costs and immobilization at sensing interfaces must be improved to encourage wider applications of extremozymes in biosensors.

Microfluidics in environmental analysis: advancements, challenges, and future prospects for rapid and efficient monitoring

Microfluidic devices have emerged as advantageous tools for detecting environmental contaminants due to their portability, ease of use, cost-effectiveness, and rapid response capabilities. These devices have wide-ranging applications in environmental monitoring of air, water, and soil matrices, and have also been applied to agricultural monitoring. Although several previous reviews have explored microfluidic devices' utility, this paper presents an up-to-date account of the latest advancements in this field for environmental monitoring, looking back at the past five years. In this review, we discuss devices for prominent contaminants such as heavy metals, pesticides, nutrients, microorganisms, per- and polyfluoroalkyl substances (PFAS), etc. We cover numerous detection methods (electrochemical, colorimetric, fluorescent, etc.) and critically assess the current state of microfluidic devices for environmental monitoring, highlighting both their successes and limitations. Moreover, we propose potential strategies to mitigate these limitations and offer valuable insights into future research and development directions.

A dual-mode assay kit using a portable potentiostat connected to a smartphone via Bluetooth communication and a potential-power angle-based paper device susceptible for low-cost point-of-care testing of iodide and dopamine

BACKGROUND

Considering that the brain controls most of the body's activities, it is very important to measure the factors affecting its function, such as dopamine and iodide. Due to the growing population in the world, it is necessary to provide fast, cheap and accurate methods with the capability of on-site analysis and without the need for invasive sampling and operator skill. As a result, there is a strong desire to replace laboratory instruments with small sensors for point-of-care testing. Paper-based analytical devices (PADs) are one of the popular zero-cost approaches to achieve this goal.

RESULTS

We developed a simple and disposable diagnostic paper system based on electroanalytical and potential-power angle-based methods. First, we prepared an angle-based analytical system capable of performing semi-quantitative iodide analysis simply by reading the colored angle traveled. This system design is based on a channel containing complex reagents and two pencil-drawn electrodes to apply a constant voltage accelerating the anions migration. Meanwhile, a three-electrode system based on conductive pencil graphite is developed to measure dopamine concentration based on linear sweep voltammetry. For the quantitative analysis, the voltammetric data was wirelessly transmitted to a mobile device via Bluetooth communication. In this context, a power supply providing the required voltage for the migration of iodide ions, a portable potentiostat system, and a mobile application for measuring dopamine were developed. The calibration curves for I- and dopamine range from 3.5 × 10-4-47.0 × 10-4 and 10.0 × 10-6-1000.0 × 10-6 mol L-1 with LODs of 2.3 × 10-4 and 5.0 × 10-6 mol L-1, respectively.

SIGNIFICANCE AND NOVELTY

A new portable dual-mode voltage-assisted integrated PAD platform was designed for iodide and dopamine analysis. The characteristics of this device allow non-experts to carry out in-field analysis using sub-100 μL saliva sample with a time-to-result of <10 min along with reducing the overall cost and operational complexity.

A Ratiometric Biosensor Containing Manganese Dioxide Nanosheets and Nitrogen-Doped Quantum Dots for 2,4-Dichlorophenoxyacetic Acid Monitoring

Nanomaterials are desirable for sensing applications. Therefore, MnO2 nanosheets and nitrogen-doped carbon dots (NCDs) were used to construct a ratiometric biosensor for quantification of 2,4-dichlorophenoxyacetic acid. The MnO2 nanosheets drove the oxidation of colorless o-phenylenediamine to OPDox, which exhibits fluorescence emission peaks at 556 nm. The fluorescence of OPDox was efficiently quenched and the NCDs were recovered as the ascorbic acid produced by the hydrolyzed alkaline phosphatase (ALP) substrate increased. Owing to the selective inhibition of ALP activity by 2,4-D and the inner filter effect, the fluorescence intensity of the NCDs at 430 nm was suppressed, whereas that at 556 nm was maintained. The fluorescence intensity ratio was used for quantitative detection. The linear equation was F = 0.138 + 3.863·C 2,4-D (correlation coefficient R2 = 0.9904), whereas the limits of detection (LOD) and quantification (LOQ) were 0.013 and 0.040 μg/mL. The method was successfully employed for the determination of 2,4-D in different vegetables with recoveries of 79%~105%. The fluorescent color change in the 2,4-D sensing system can also be captured by a smartphone to achieve colorimetric detection by homemade portable test kit.

Exploring the potential of cellulose autofluorescence for optical detection of tannin in red wines

The growing demand for opto-electronic devices within an automated landscape has opened up new opportunities for harnessing sustainable cellulose materials for sensors technology. Cellulose, a versatile material, enables its combination with other materials, but in most of these applications, cellulose is typically employed as support or substrate, while its inherent autofluorescence remains largely underexplored for sensors. In light of this context, this study delves into the autofluorescence characteristics of pristine cellulose nanocrystals extracted from wood via enzymatic route for optical sensors tailored to detect tannins. By fine-tuning the experimental setup, photoluminescence (PL) emission bands were scrutinized across three distinct spectral regions, namely 300-400 nm, 400-500 nm and 550-700 nm. The proposed mechanism reveals the occurrence of dynamic fluorescence quenching, which enabled the selective monitoring of tannins in red wines across a dynamic range spanning from 10 to 1060 μg mL-1. This sensing platform provided a limit of detection (LoD) of 6.1 μg mL-1. Notably, the sensing platform's efficacy was validated with remarkable recovery rates of 99.7 % and 95.3 % when subjected to testing with cabernet sauvignon and tannat wines. These findings emphasize the sensing platform's potential for monitoring tannic acids in beverages and food products.

Acoustofluidics-Assisted Multifunctional Paper-Based Analytical Devices

Microfluidic paper-based analytical devices (μPADs) feature an economic and sensitive nature, while acoustofluidics displays contactless and versatile virtue, and both of them gained tremendous interest in the past decades. Integrating μPADs with acoustofluidic techniques provides great potential to overcome the inherent shortcomings and make appealing achievements. Here, we present acoustofluidics-assisted multifunctional paper-based analytical devices that leverage bulk acoustic waves to realize multiple applications on paper substrates, including uniform colorimetric detection, microparticle/cell enrichment, fluorescence amplification, homogeneous mixing, and nanomaterial synthesis. The glucose detection in the range of 5-15 mM was conducted to perform uniform colorimetric detection. Various types (brass powder, copper powder, diamond powder, and yeast cells) and sizes (5-200 μm) of solid particles and biological cells can be enriched on paper in a few seconds or minutes; thus, fluorescence amplification by 3 times was realized with the enrichment. The high-throughput and homogeneous mixing of two fluids can be achieved, and based on the mixing, nanomaterials (ZnO nanosheets) were synthesized on paper. We analyzed the underlying mechanisms of these applications in the devices, which are attributed to Faraday waves and Chladni patterns. With their simple fabrication and prominent effectiveness, the devices open up new possibilities for paper-based microfluidic devices.

Efficient Electrochemiluminescence Sensing in Microfluidic Biosensors: A Review

Microfluidic devices are capable of handling 10-9 L to 10-18 L of fluids by incorporating tiny channels with dimensions of ten to hundreds of micrometers, and they can be fabricated using a wide range of materials including glass, silicon, polymers, paper, and cloth for tailored sensing applications. Microfluidic biosensors integrated with detection methods such as electrochemiluminescence (ECL) can be used for the diagnosis and prognosis of diseases. Coupled with ECL, these tandem devices are capable of sensing biomarkers at nanomolar to picomolar concentrations, reproducibly. Measurement at this low level of concentration makes microfluidic electrochemiluminescence (MF-ECL) devices ideal for biomarker detection in the context of early warning systems for diseases such as myocardial infarction, cancer, and others. However, the technology relies on the nature and inherent characteristics of an efficient luminophore. The luminophore typically undergoes a redox process to generate excited species which emit energy in the form of light upon relaxation to lower energy states. Therefore, in biosensor design the efficiency of the luminophore is critical. This review is focused on the integration of microfluidic devices with biosensors and using electrochemiluminescence as a detection method. We highlight the dual role of carbon quantum dots as a luminophore and co-reactant in electrochemiluminescence analysis, drawing on their unique properties that include large specific surface area, easy functionalization, and unique luminescent properties.

Paper as smart support for bioreceptor immobilization in electrochemical paper-based devices

The use of paper as a smart support in the field of electrochemical sensors has been largely improved over the last 15 years, driven by its outstanding features such as foldability and porosity, which enable the design of reagent and equipment-free multi-analysis devices. Furthermore, the easy surface engineering of paper has been used to immobilize different bioreceptors, through physical adsorption, covalent bonding, and electrochemical polymerization, boosting the fine customization of the analytical performances of paper-based biosensors. In this review, we focused on the strategies to engineer the surface of the paper for the immobilization of (bio)recognition elements (eg., enzymes, antibodies, DNA, molecularly imprinted polymers) with the overriding goal to develop accurate and reliable paper-based electrochemical biosensors. Furthermore, we highlighted how to take advantage of paper for designing smart configurations by integrating different analytical processes in an eco-designed analytical tool, starting from the immobilization of the (bio)receptor and the reagents, through a designed sample flow along the device, until the analyte detection.

Advances in Bioelectrode Design for Developing Electrochemical Biosensors

The critical performance factors such as selectivity, sensitivity, operational and storage stability, and response time of electrochemical biosensors are governed mainly by the function of their key component, the bioelectrode. Suitable design and fabrication strategies of the bioelectrode interface are essential for realizing the requisite performance of the biosensors for their practical utility. A multifaceted attempt to achieve this goal is visible from the vast literature exploring effective strategies for preparing, immobilizing, and stabilizing biorecognition elements on the electrode surface and efficient transduction of biochemical signals into electrical ones (i.e., current, voltage, and impedance) through the bioelectrode interface with the aid of advanced materials and techniques. The commercial success of biosensors in modern society is also increasingly influenced by their size (and hence portability), multiplexing capability, and coupling in the interface of the wireless communication technology, which facilitates quick data transfer and linked decision-making processes in real-time in different areas such as healthcare, agriculture, food, and environmental applications. Therefore, fabrication of the bioelectrode involves careful selection and control of several parameters, including biorecognition elements, electrode materials, shape and size of the electrode, detection principles, and various fabrication strategies, including microscale and printing technologies. This review discusses recent trends in bioelectrode designs and fabrications for developing electrochemical biosensors. The discussions have been delineated into the types of biorecognition elements and their immobilization strategies, signal transduction approaches, commonly used advanced materials for electrode fabrication and techniques for fabricating the bioelectrodes, and device integration with modern electronic communication technology for developing electrochemical biosensors of commercial interest.

Self-calibrating dual-sensing electrochemical sensors for accurate detection of carbon dioxide in blood

A paper-based electrochemical dual-function biosensor capable of determining pH and TCO2 was synthesized for the first time using an iridium oxide pH electrode and an all-solid-state ion electrode (ASIE). In the study, to obtain highly reliable results, the biosensor was equipped with a real-time pH correction function before TCO2 measurements. Compared to traditional liquid-filling carbon dioxide detection sensors, the utilization of ferrocene endows our novel sensor with abundant positive sites, and thus greatly improves its performance. Conversely, the introduction of MXene with conductivity close to that of metals reduces electrode resistance, which is beneficial for accelerating the electrochemical reaction of the sensor and reducing LOD. After optimization, the detection range of TCO2 is 0.095 nM-0.66 M, with a detection limit of as low as 0.023 nM. In addition, the sensor was used in real serum sample-spiked recovery experiments and comparison experiments with existing clinical blood gas analyzers, which confirmed the effectiveness of its clinical application. This study provides a method for the rational design of paper-based electrochemical biosensors and a new approach for the clinical detection of blood carbon dioxide.

Sustainable plant-wearable sensors for on-site, rapid decentralized detection of pesticides toward precision agriculture and food safety

The synergy between eco-friendly biopolymeric films and printed devices leads to the production of plant-wearable sensors for decentralized analysis of pesticides in precision agriculture and food safety. Herein, a simple method for fabrication of flexible, and sustainable sensors printed on cellulose acetate (CA) substrates has been demonstrated to detect carbendazim and paraquat in agricultural, water and food samples. The biodegradable CA substrates were made by casting method while the full electrochemical system of three electrodes was deposited by screen-printing technique (SPE) to produce plant-wearable sensors. Analytical performance was assessed by differential pulse (DPV) and square wave voltammetry (SWV) in a linear concentration range between 0.1 and 1.0 μM with detection limits of 54.9 and 19.8 nM for carbendazim and paraquat, respectively. The flexible and sustainable non-enzymatic plant-wearable sensor can detect carbendazim and paraquat on lettuce and tomato skins, and also water samples with no interference from other pesticides. The plant-wearable sensors had reproducible response being robust and stable against multiple flexions. Due to high sensitivity and selectivity, easy operation and rapid agrochemical detection, the plant-wearable sensors can be used to detect biomarkers in human biofluids and be used in on-site analysis of other hazardous chemical substances.

Dual Chromatic Laser-Printed Microfluidic Paper-Based Analytical Device (μPAD) for the Detection of Atrazine in Water

Water pollution caused by pesticides is a significant threat to the environment and human health. Silver and gold nanoparticle (AgNPs, AuNPs)-based biosensors are affordable tools, ideal for environmental monitoring. Microfluidic paper-based devices (μPADs) are a promising approach for on-site testing, but few studies have explored the use of laser printing (LP) for μPAD-based biosensors. This study investigates the feasibility of using laser printing to fabricate paper-based biosensors for pesticide detection in water samples. The μPAD was designed and optimized by using different filter paper porosities, patterns, and channel thicknesses. The developed LP-μPAD was used to sense the pesticide atrazine in water through colorimetric assessments using a smartphone-assisted image analysis. The analytical assessment showed a limit of detection (LOD) of 3.5 and 10.9 μM for AgNPs and AuNPs, respectively. The sensor had high repeatability and reproducibility. The LP-μPAD also demonstrated good recovery and functionality in simulated contaminated water. Furthermore, the detection of pesticides was found to be specific under the influence of interferents, such as NaCl and pH levels. By combining laser printing and nanoparticles, the proposed sensor could contribute to developing effective and low-cost solutions for monitoring water quality that are widely accessible.

Pesticide biosensors: trends and progresses

Pesticides, chemical substances extensively employed in agriculture to optimize crop yields, pose potential risks to human and environmental health. Consequently, regulatory frameworks are in place to restrict pesticide residue concentrations in water intended for human consumption. These regulations are implemented to safeguard consumer safety and mitigate any adverse effects on the environment and public health. Although gas chromatography- and liquid chromatography-mass spectrometry (GC-MS and LC-MS) are highly efficient techniques for pesticide quantification, their use is not suitable for real-time monitoring due to the need for sophisticated laboratory pretreatment of samples prior to analysis. Since they would enable analyte detection with selectivity and sensitivity without sample pretreatment, biosensors appear as a promising alternative. These consist of a bioreceptor allowing for specific recognition of the target and of a detection platform, which translates the biological interaction into a measurable signal. As early detection systems remain urgently needed to promptly alert and act in case of pollution, we review here the biosensors described in the literature for pesticide detection to advance their development for use in the field.

Lab-made flexible third-generation fructose biosensors based on 0D-nanostructured transducers

Herein, we report a scalable benchtop electrode fabrication method to produce highly sensitive and flexible third-generation fructose dehydrogenase amperometric biosensors based on water-dispersed 0D-nanomaterials. The electrochemical platform was fabricated via Stencil-Printing (StPE) and insulated via xurography. Carbon black (CB) and mesoporous carbon (MS) were employed as 0D-nanomaterials promoting an efficient direct electron transfer (DET) between fructose dehydrogenase (FDH) and the transducer. Both nanomaterials were prepared in water-phase via a sonochemical approach. The nano-StPE exhibited enhanced electrocatalytic currents compared to conventional commercial electrodes. The enzymatic sensors were exploited for the determination of D-fructose in model solutions and various food and biological samples. StPE-CB and StPE-MS integrated biosensors showed appreciable sensitivity (∼150 μA cm-2 mM-1) with μmolar limit of detection (0.35 and 0.16 μM, respectively) and extended linear range (2-500 and 1-250 μM, respectively); the selectivity of the biosensors, ensured by the low working overpotential (+0.15 V), has been also demonstrated. Good accuracy (recoveries between 95 and 116%) and reproducibility (RSD ≤8.6%) were achieved for food and urine samples. The proposed approach because of manufacturing versatility and the electro-catalytic features of the water-nanostructured 0D-NMs opens new paths for affordable and customizable FDH-based bioelectronics.

Paper-Based All-in-One Origami Nanobiosensor for Point-of-Care Detection of Cardiac Protein Markers in Whole Blood

Rapid and accurate diagnosis of cardiovascular diseases (CVDs) at the earliest stage is of paramount importance to improve the treatment outcomes and avoid irreversible damage to a patient's cardiovascular system. Microfluidic paper-based devices (μPADs) represent a promising platform for rapid CVD diagnosis at the point of care (POC). This paper presents an electrochemical μPAD (E-μPAD) with an all-in-one origami design for rapid and POC testing of cardiac protein markers in whole blood. Based on the label-free, electrochemical impedance spectroscopy (EIS) immunoassay, the E-μPAD integrates all essential components on a single chip, including three electrochemical cells, a plasma separation membrane, and a buffer absorption pad, enabling easy and streamlined operations for multiplexed detection of three cardiac protein markers [cardiac troponin I (cTnI), brain natriuretic peptide (BNP)-32, and D-Dimer] on a finger-prick whole blood sample within 46 min. Superior analytical performance is achieved through sensitive EIS measurement on carbon electrodes decorated with semiconductor zinc oxide nanowires (ZnO NWs). Using spiked human plasma samples, ultralow limits of detection (LODs) of E-μPAD are achieved at 4.6 pg/mL (190 fM) for cTnI, 1.2 pg/mL (40 fM) for BNP-32, and 146 pg/mL (730 fM) for D-Dimer. Real human blood samples spiked with purified proteins are also tested, and the device's analytical performance was proven to be comparable to commercial ELISA kits. The all-in-one E-μPAD will allow rapid and sensitive testing of cardiac protein markers through easy operations, which holds great potential for on-site screening of acute CVDs in nonlaboratory settings such as emergency rooms, doctor's offices, or patient homes.

Research progress on pesticide residue detection based on microfluidic technology

The problem of pesticide residue contamination has attracted widespread attention and poses a risk to human health. The current traditional pesticide residue detection methods have difficulty meeting rapid and diverse field screening requirements. Microfluidic technology integrates functions from sample preparation to detection, showing great potential for quick and accurate high-throughput detection of pesticide residues. This paper reviews the latest research progress on microfluidic technology for pesticide residue detection. First, the commonly used microfluidic materials are summarized, including silicon, glass, paper, polydimethylsiloxane, and polymethyl methacrylate. We evaluated their advantages and disadvantages in pesticide residue detection applications. Second, the current pesticide residue detection technology based on microfluidics and its application to real samples are summarized. Finally, we discuss this technology's present challenges and future research directions. This study is expected to provide a reference for the future development of microfluidic technology for pesticide residue detection.

Glyphosate Separating and Sensing for Precision Agriculture and Environmental Protection in the Era of Smart Materials

The present article critically and comprehensively reviews the most recent reports on smart sensors for determining glyphosate (GLP), an active agent of GLP-based herbicides (GBHs) traditionally used in agriculture over the past decades. Commercialized in 1974, GBHs have now reached 350 million hectares of crops in over 140 countries with an annual turnover of 11 billion USD worldwide. However, rolling exploitation of GLP and GBHs in the last decades has led to environmental pollution, animal intoxication, bacterial resistance, and sustained occupational exposure of the herbicide of farm and companies' workers. Intoxication with these herbicides dysregulates the microbiome-gut-brain axis, cholinergic neurotransmission, and endocrine system, causing paralytic ileus, hyperkalemia, oliguria, pulmonary edema, and cardiogenic shock. Precision agriculture, i.e., an (information technology)-enhanced approach to crop management, including a site-specific determination of agrochemicals, derives from the benefits of smart materials (SMs), data science, and nanosensors. Those typically feature fluorescent molecularly imprinted polymers or immunochemical aptamer artificial receptors integrated with electrochemical transducers. Fabricated as portable or wearable lab-on-chips, smartphones, and soft robotics and connected with SM-based devices that provide machine learning algorithms and online databases, they integrate, process, analyze, and interpret massive amounts of spatiotemporal data in a user-friendly and decision-making manner. Exploited for the ultrasensitive determination of toxins, including GLP, they will become practical tools in farmlands and point-of-care testing. Expectedly, smart sensors can be used for personalized diagnostics, real-time water, food, soil, and air quality monitoring, site-specific herbicide management, and crop control.

Advancement in Paper-Based Electrochemical Biosensing and Emerging Diagnostic Methods

The utilization of electrochemical detection techniques in paper-based analytical devices (PADs) has revolutionized point-of-care (POC) testing, enabling the precise and discerning measurement of a diverse array of (bio)chemical analytes. The application of electrochemical sensing and paper as a suitable substrate for point-of-care testing platforms has led to the emergence of electrochemical paper-based analytical devices (ePADs). The inherent advantages of these modified paper-based analytical devices have gained significant recognition in the POC field. In response, electrochemical biosensors assembled from paper-based materials have shown great promise for enhancing sensitivity and improving their range of use. In addition, paper-based platforms have numerous advantageous characteristics, including the self-sufficient conveyance of liquids, reduced resistance, minimal fabrication cost, and environmental friendliness. This study seeks to provide a concise summary of the present state and uses of ePADs with insightful commentary on their practicality in the field. Future developments in ePADs biosensors include developing novel paper-based systems, improving system performance with a novel biocatalyst, and combining the biosensor system with other cutting-edge tools such as machine learning and 3D printing.

Affordable Portable Platform for Classic Photometry and Low-Cost Determination of Cholinesterase Activity

Excessive use of pesticides could potentially harm the environment for a long time. The reason for this is that the banned pesticide is still likely to be used incorrectly. Carbofuran and other banned pesticides that remain in the environment may also have a negative effect on human beings. In order to provide a better chance for effective environmental screening, this thesis describes a prototype of a photometer tested with cholinesterase to potentially detect pesticides in the environment. The open-source portable photodetection platform uses a color-programmable red, green and blue light-emitting diode (RGB LED) as a light source and a TSL230R light frequency sensor. Acetylcholinesterase from Electrophorus electricus (AChE) with high similarity to human AChE was used for biorecognition. The Ellman method was selected as a standard method. Two analytical approaches were applied: (1) subtraction of the output values after a certain period of time and (2) comparison of the slope values of the linear trend. The optimal preincubation time for carbofuran with AChE was 7 min. The limits of detection for carbofuran were 6.3 nmol/L for the kinetic assay and 13.5 nmol/L for the endpoint assay. The paper demonstrates that the open alternative for commercial photometry is equivalent. The concept based on the OS3P/OS3P could be used as a large-scale screening system.

Bimetallic AuPt alloy/rod-like CeO2 nanojunctions with high peroxidase-like activity for colorimetric sensing of organophosphorus pesticides

Organophosphorus pesticides (OP) have extensive applications in agriculture, while their overuse causes inevitable residues in food, soil, and water, ultimately being harmful to human health and even causing diverse dysfunctions. Herein, a novel colorimetric platform was established for quantitative determination of malathion based on peroxidase mimic AuPt alloy decorated on CeO₂ nanorods (CeO₂@AuPt NRs). The synthesized nanozyme oxidized colorless 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂. Besides, the oxidized TMB was inversely reduced by ascorbic acid (AA), which were originated from hydrolysis of L-ascorbic acid-2-phosphate (AA2P) with the assistance of acid phosphatase (ACP). Based upon this observation ACP analysis was explored by colorimetry, showing a wid linear range of 0.2 ~ 3.5 U L^-1 and a low limit of detection (LOD = 0.085 U L^-1, S/N = 3). Furthermore, malathion present in the colorimetric system inhibited the activity of ACP and simultaneously affected the generation of AA, in turn promoting the recovery of the chromogenic reaction. Based on this, the LOD was decreased to 1.5 nM (S/N = 3) for the assay of malathion with a wide linear range of 6 ~ 100 nM. This simple colorimetric platform provides some informative guidelines for determination of other pesticides and disease markers.

Novel dual-emission sulfur quantum dot sensing platform for quantitative monitoring of pesticide 2,4-dichlorophenoxyacetic acid

In this work, a novel environment-friendly dual-emission Rhodamine B modified sulfur quantum dots (RhB-SQDs) sensing platform was established to economically monitor organochlorine pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) through regulating the activity of alkaline phosphatase (ALP). This dual emission RhB-SQDs exhibited excellent fluorescence and high photostability with emission wavelengths of 455 nm and 580 nm. ALP catalyzed the hydrolysis of the substrate p-nitrophenyl phosphate to p-nitrophenol, which quenched RhB-SQDs fluorescence at 455 nm due to the internal filtration effect, but had no effect the fluorescence intensity of RhB-SQDs at 580 nm. When 2,4-D was present, the activity of ALP was specifically inhibited and enzymatic reaction was interrupted, leading to the reduction of p-nitrophenol production, so the fluorescence of RhB-SQDs at 455 nm was restored. It demonstrated a good linear relationship between the concentration of 2,4-D and F₄₅₅/F₅₈₀ in the range of 0.050-0.500 μg mL^-1, with a detection limit of 17.3 ng mL^-1. The dual-emission fluorescent probe was successfully realized in the identification of 2,4-D in natural water samples and vegetables with the advantages of exceptional accuracy, immunity to interference, and selectivity. The platform offers a fresh look at pesticide monitoring and has the potential to prevent pesticide-related health issues.

Trends in Paper-Based Sensing Devices for Clinical and Environmental Monitoring

Environmental toxic pollutants and pathogens that enter the ecosystem are major global issues. Detection of these toxic chemicals/pollutants and the diagnosis of a disease is a first step in efficiently controlling their contamination and spread, respectively. Various analytical techniques are available to detect and determine toxic chemicals/pathogens, including liquid chromatography, HPLC, mass spectroscopy, and enzyme-linked immunosorbent assays. However, these sensing strategies have some drawbacks such as tedious sample pretreatment and preparation, the requirement for skilled technicians, and dependence on large laboratory-based instruments. Alternatively, biosensors, especially paper-based sensors, could be used extensively and are a cost-effective alternative to conventional laboratory testing. They can improve accessibility to testing to identify chemicals and pollutants, especially in developing countries. Due to its low cost, abundance, easy disposal (by incineration, for example) and biocompatible nature, paper is considered a versatile material for the development of environmentally friendly electrochemical/optical (bio) sensor devices. This review presents an overview of sensing platforms constructed from paper, pointing out the main merits and demerits of paper-based sensing systems, their fabrication techniques, and the different optical/electrochemical detection techniques that they exploit.

Advances on microfluidic paper-based electroanalytical devices

Since the inception of the first electrochemical devices on paper substrates, many different reports of microfluidic paper-based electroanalytical devices (μPEDs), innovative hydrophobic barriers and electrode fabrication processes have allowed the incorporation of diverse materials, resulting in different applications and a boost in performance. These advancements have led to the creation of paper-based devices with comparable performance to many standard conventional devices, with the added benefits of pumpless fluidic transport, component separation and reagent storage that can be exploited to automate and handle sample preprocessing. Herein, we review μPEDs, summarize the characteristics and functionalities of μPEDs, such as separation, fluid flow control and storage, and outline the conventional and emerging fabrication and modification approaches for μPEDs. We also examine the recent application of μPEDs in biomedicine, the environment, and food and water safety, as well as some limitations and challenges that must be addressed.

PB@PDA nanocomposites as nanolabels and signal reporters for separate-type cathodic photoelectrochemical immunosensors in the detection of carcinoembryonic antigens

Photoelectrochemical (PEC) immunoassays exhibiting high sensitivity and decent operability have considerable potential in areas such as cancer diagnostics. In particular, cathodic PEC configurations can prevent interference from reductive substances, which can occur in biological samples; however, challenges remain in terms of sensitivity and operability. In this study, separate-type PEC immunoassays were developed for carcinoembryonic antigen (CEA) by combining microplate-based immune recognition and off-on cathodic PEC detection. Polydopamine (PDA)-coated Prussian blue (PB) nanoparticles (PB@PDA NPs) were used as signal tags to label the detection antibody. The PB NPs and PDA captured on the microplates both disassembled under strongly alkaline conditions to generate redox-active electron acceptors. The disassembled products were quantitatively transferred to PEC detection cells and synergistically enhanced the PEC current with microstructured BiOI, which operated as a cathodic semiconductor electrode. As proof of principle, carcinoembryonic antigen (CEA) was applied to elucidate the potential application of PEC immunoassay in clinical diagnosis, and the obtained linear range of the sensor was 0.001-100 ng mL^-1 with the detection limit of 54.9 fg mL^-1 (S/N = 3). The proposed separate-type off-on PEC strategy showed high sensitivity and decent operability for CEA detection, indicating its potential for the identification of other tumor markers.

Threaded 3D microfluidic paper analytical device-based ratiometric fluorescent sensor for background-free and visual detection of organophosphorus pesticides

With the increasing concerns of food safety and environmental protection, it is desirable to develop reliable, effective, and portable sensors for detection of organophosphorus pesticides (OPs). Here, a cascade reaction system integrated with threaded 3D microfluidic paper analytical device (3D μPAD) was firstly developed for background-free and visual detection of OPs in agricultural samples. Butyrylcholinesterase (BChE) hydrolyzed acetylcholine into thiocholine (TCh), which reduced MnO₂ nanosheets into Mn²⁺. With addition of OPs, BChE activity was irreversibly inhibited, and the generation of TCh and the reduction of MnO₂ nanosheets were prevented. Then the remaining MnO₂ nanosheets oxidized o-phenylenediamine into 2,3-diaminophenazine with yellow-emission fluorescence, which quenched the fluorescence intensity of red-emission carbon dots (RCDs) via inner-filter effect. Based on above mechanism, a ratiometric fluorescent system was established for OPs detection. Threaded 3D μPAD consisted of 4 layers, which allowed to load and/or add reagents to trigger the cascade reaction system for OPs detection. The fluorescent images presented distinguishable color variations from red to yellow with dichlorvos concentrations ranging from 2.5 to 120 μg L^-1, and the limit of detection was 1.0 μg L^-1. In the practical samples testing, threaded 3D μPAD can eliminate background influence on fluorescent signal for OPs detection. Threaded 3D μPAD integrated with ratiometric sensing platform has merits of accuracy response, facile operation, and background-free detection, which supplies a new alternative approach for on-site pesticide detection.

ALP-Based Biosensors Employing Electrodes Modified with Carbon Nanomaterials for Pesticides Detection

Due to the growing presence of pesticides in the environment and in food, the concern of their impact on human health is increasing. Therefore, the development of fast and reliable detection methods is needed. Enzymatic inhibition-based biosensors represent a good alternative for replacing the more complicated and time-consuming traditional methods (chromatography, spectrophotometry, etc.). This paper describes the development of an electrochemical biosensor exploiting alkaline phosphatase as the biological recognition element and a chemically modified glassy carbon electrode as the transducer. The biosensor was prepared modifying the GCE surface by a mixture of Multi-Walled-Carbon-Nanotubes (MWCNTs) and Electrochemically-Reduced-Graphene-Oxide (ERGO) followed by the immobilization of the enzyme by cross-linking with bovine serum albumin and glutaraldehyde. The inhibition of the biosensor response caused by pesticides was established using 2-phospho-L-ascorbic acid as the enzymatic substrate, whose dephosphorylation reaction produces ascorbic acid (AA). The MWCNTs/ERGO mixture shows a synergic effect in terms of increased sensitivity and decreased overpotential for AA oxidation. The response of the biosensor to the herbicide 2,4-dichloro-phenoxy-acetic-acid was evaluated and resulted in the concentration range 0.04-24 nM, with a limit of the detection of 16 pM. The determination of other pesticides was also achieved. The re-usability of the electrode was demonstrated by performing a washing procedure.

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.

Smartphone-Based Pressure Signal Readout Device Combined with Bidirectional Immunochromatographic Test Strip for Dual-Analyte Detection

Pressure has been a facile signal readout mode for developing point-of-care testing devices due to the attractive features of portability, accessibility, rapidity, and affordability. Herein, a pressure signal readout device was designed by integrating two homemade needle-type piezoresistive transducers, a controller for a thin-film piezoresistive sensor and a smartphone. Meanwhile, a bidirectional immunochromatographic test strip was designed as an immunoreaction platform for dual-analyte detection. Using PdCuPt nanoparticles with catalase-mimic activity as signal tags, the pressure signals triggered by catalyzed aerogenous reaction were monitored by the pressure signal readout device and read on a smartphone with the Bluetooth module. In this proof-of-principle work, imidacloprid and carbendazim were detected as model analytes. The dynamic ranges for quantitating imidacloprid and carbendazim are 20 pg mL^-1 to 50 ng mL^-1 and 50 pg mL^-1 to 50 ng mL^-1, respectively. The whole immunoassay process was completed within 16 min. The recovery values for imidacloprid and carbendazim spiked into herbal medicines are 82.0-110.0 and 84.0-116.0%, respectively, verifying its reliability for real sample detection. As the smartphone APP and controller for a thin-film piezoresistive sensor contain 12 signal channels, the system can be easily extended to meet the demand for high-throughput screening.

Electrochemical behaviour of cellulose/reduced graphene oxide/carbon fiber paper electrodes towards the highly sensitive detection of amitrole

Amitrole is a non-selective triazole herbicide that is widespread used to control a variety of weeds in agriculture, but it may pollute the environment and do harm to organisms. Thus, it is of critical significance to enlist a low-cost, sensitive, stable and renewable method to detect amitrole. In this paper, electrochemical experiments were carried out using carbon fibers/reduced graphene oxide/cellulose paper electrodes, which demonstrated good electrocatalytic performance for amitrole detection. The electrochemical process of amitrole on the surface of the reduced paper electrode was a quasi-reversible reaction controlled by diffusion. Cyclic voltammetry and the amperometric i-t curve method were used for amitrole determination at a micro molar level and higher-concentration range with the following characteristics: linear range 5 × 10^-6 mol L^-1 to 3 × 10^-5 mol L^-1, detection limit 2.44 × 10^-7 mol L^-1. In addition, the relative standard deviation of repeatability is 3.74% and of stability is 4.68%. The reduced paper electrode with high sensitivity, low detection limit, good stability and repeatability provides novel ideas for on-site amitrole detection in food and agriculture.

Regulatory Small RNAs for a Sustained Eco-Agriculture

Small RNA (sRNA) has become an alternate biotechnology tool for sustaining eco-agriculture by enhancing plant solidity and managing environmental hazards over traditional methods. Plants synthesize a variety of sRNA to silence the crucial genes of pests or plant immune inhibitory proteins and counter adverse environmental conditions. These sRNAs can be cultivated using biotechnological methods to apply directly or through bacterial systems to counter the biotic stress. On the other hand, through synthesizing sRNAs, microbial networks indicate toxic elements in the environment, which can be used effectively in environmental monitoring and management. Moreover, microbes possess sRNAs that enhance the degradation of xenobiotics and maintain bio-geo-cycles locally. Selective bacterial and plant sRNA systems can work symbiotically to establish a sustained eco-agriculture system. An sRNA-mediated approach is becoming a greener tool to replace xenobiotic pesticides, fertilizers, and other chemical remediation elements. The review focused on the applications of sRNA in both sustained agriculture and bioremediation. It also discusses limitations and recommends various approaches toward future improvements for a sustained eco-agriculture system.

Paper-Based Electrochemical Biosensors for Food Safety Analysis

Nowadays, foodborne pathogens and other food contaminants are among the major contributors to human illnesses and even deaths worldwide. There is a growing need for improvements in food safety globally. However, it is a challenge to detect and identify these harmful analytes in a rapid, sensitive, portable, and user-friendly manner. Recently, researchers have paid attention to the development of paper-based electrochemical biosensors due to their features and promising potential for food safety analysis. The use of paper in electrochemical biosensors offers several advantages such as device miniaturization, low sample consumption, inexpensive mass production, capillary force-driven fluid flow, and capability to store reagents within the pores of the paper substrate. Various paper-based electrochemical biosensors have been developed to enable the detection of foodborne pathogens and other contaminants that pose health hazards to humans. In this review, we discussed several aspects of the biosensors including different device designs (e.g., 2D and 3D devices), fabrication techniques, and electrode modification approaches that are often optimized to generate measurable signals for sensitive detection of analytes. The utilization of different nanomaterials for the modification of electrode surface to improve the detection of analytes via enzyme-, antigen/antibody-, DNA-, aptamer-, and cell-based bioassays is also described. Next, we discussed the current applications of the sensors to detect food contaminants such as foodborne pathogens, pesticides, veterinary drug residues, allergens, and heavy metals. Most of the electrochemical paper analytical devices (e-PADs) reviewed are small and portable, and therefore are suitable for field applications. Lastly, e-PADs are an excellent platform for food safety analysis owing to their user-friendliness, low cost, sensitivity, and a high potential for customization to meet certain analytical needs.

Ultrasensitive detection of acephate based on carbon quantum dot-mediated fluorescence inner filter effects

Acephate is an organophosphorus pesticide (OP) that is widely used to control insects in agricultural fields such as in vegetables and fruits. Toxic OPs can enter human and animal bodies and eventually lead to chronic or acute poisoning. However, traditional enzyme inhibition and colorimetric methods for OPs detection usually require complicated detection procedures and prolonged time and have low detection sensitivity. High-sensitivity monitoring of trace levels of acephate residues is of great significance to food safety and human health. Here, we developed a simple method for ultrasensitive quantitative detection of acephate based on the carbon quantum dot (CQD)-mediated fluorescence inner filter effect (IFE). In this method, the fluorescence from CQDs at 460 nm is quenched by 2,3-diaminophenazine (DAP) and the resulting fluorescence from DAP at 558 nm is through an IFE mechanism between CQDs and DAP, producing ratiometric responses. The ratiometric signal I558/I460 was found to exhibit a linear relationship with the concentration of acephate. The detection limit of this method was 0.052 ppb, which is far lower than the standards for acephate from China and EU in food safety administration. The ratiometric fluorescence sensor was further validated by testing spiked samples of tap water and pear, indicating its great potential for sensitive detection of trace OPs in complex matrixes of real samples.

A direct contact bioassay using immobilized microalgal balls to evaluate the toxicity of contaminated field soils

The present study used a bioassay of immobilized microalgae (Chlorella vulgaris) via direct contact to assess the toxicity of eleven uncontaminated (reference) and five field contaminated soils with various physicochemical properties and contamination. Photosynthetic oxygen concentration in the headspace of the test kit by Chlorella vulgaris in the reference soils ranged between 12.93% and 14.80% and only 2.54%-7.14% in the contaminated soils, respectively. Inherent test variability (CV_i) values ranged between 2.90% and 9.04%; variation due to soil natural properties (CV_rs) ranged between 0.33% and 13.0%; and minimal detectable difference (MDD) values ranged from 4.69% to 11.6%. A computed toxicity threshold of 15% was established for microalgae soil toxicity tests based on calculations of the maximal tolerable inhibition (MTI). All contaminated soils were considered toxic to microalgae because their levels of inhibition ranged between 39.5% and 82.9%, exceeding the 15% toxicity threshold. It can be concluded that the elevated concentrations of heavy metals and organic contaminants in the contaminated soils induced the higher inhibitory levels. Overall, direct contact soil toxicity tests using immobilized microalgae provided coherent and repeatable data and can be utilized as a simple and suitable tool for the toxicity testing of contaminated field soils.

Recent advances in electrochemical-based sensors amplified with carbon-based nanomaterials (CNMs) for sensing pharmaceutical and food pollutants

Foodborne-related infections due to additives and pollutants pose a considerable task for food processing enterprises. Therefore, the competent, cost-effective, and quick investigation of nutrition additives and contaminants is essential to reduce the threat of public fitness problems. The electrochemical sensor (ECS) shows facile and potent analytical approaches desirable for food protection and quality inspection over traditional methods. The consequence of a broad display of nanomaterials has paved the path for their relevance in designing high-performance ECSs appliances for medical diagnostics and conditions and food protection. This review article has discussed the importance of electrochemical-based sensors amplified with carbon-based nanomaterials (CNMs). Initially, we have demonstrated the types of pharmaceutical and food/agriculture pollutants (such as pesticides, heavy metals, antibiotics and other medical drugs) present in water. Subsequently, we have compiled the information on electrochemical techniques (such as voltammetric and electrochemical impedance spectroscopy) and their crucial parameters for detecting pollutants. Further, the applications of CNMs for sensing pharmaceutical and food pollutants have been demonstrated in detail. Finally, the topic has been concluded with existing challenges and future prospects.