Nano-interface driven electrochemical sensor for pesticides detection based on the acetylcholinesterase enzyme inhibition

Lamellar Ti3C2 MXene composite decorated with platinum-doped MoS2 nanosheets as electrochemical sensing functional platform for highly sensitive analysis of organophosphorus pesticides

Precisely detecting organophosphorus pesticides (OPs) is paramount in upholding human safety and environmental preservation, especially in food safety. Herein, an electrochemical acetylcholinesterase (AChE) sensing platform entrapped in chitosan (Chit) on the glassy carbon electrodes (GCEs) decorated with Pt/MoS2/Ti3C2 MXene (Pt/MoS2/TM) was constructed for the detection of chlorpyrifos. It is worth noting that Pt/MoS2/TM possesses good biocompatibility, remarkable electrical conductivity, environmental stability and large specific surface area. Besides, the heterostructure formed by the composite of TM and MoS2 improves the conductivity and maintains the original structure, which is conducive to improving the electrochemical property. The coordination effect between the individual components enables the even distribution of functional components and enhances the electrochemical performance of the biosensor (AChE-Chit/Pt/MoS2/TM). Under optimal efficiency and sensitivity, the AChE-Chit/Pt/MoS2/TM/GCE sensing platform exerts comparable analytical performance and a wide concentration range of chlorpyrifos from 10-12 to 10-6 M as well as a low limit of detection (4.71 × 10-13 M). Furthermore, the biosensor is utilized to detect OPs concerning three kinds of fruits and vegetables with good feasibility and recoveries (94.81% to 104.0%). This work would provide a new scheme to develop high-sensitivity sensors based on the two-dimensional nanosheet/laminar hybrid structure for practical applications in environmental monitoring and agricultural product detection.

Two Fluorescent Probes for Recognition of Acetylcholinesterase: Design, Synthesis, and Comparative Evaluation

In this study, two "on-off" probes (BF2-cur-Ben and BF2-cur-But) recognizing acetylcholinesterase (AChE) were designed and synthesized. The obtained probes can achieve recognition of AChE with good selectivity and pH-independence with a linear range of 0.5~7 U/mL and 0.5~25 U/mL respectively. BF2-cur-Ben has a lower limit of detection (LOD) (0.031 U/mL), higher enzyme affinity (Km = 16 ± 1.6 μM), and higher inhibitor sensitivity. A responsive mechanism of the probes for AChE was proposed based on HPLC and mass spectra (MS) experiments, as well as calculations. In molecular simulation, BF2-cur-Ben forms more hydrogen bonds (seven, while BF2-cur-But has only four) and thus has a more stable enzyme affinity, which is mirrored by the results of the comparison of Km values. These two probes could enable recognition of intracellular AChE and probe BF2-cur-Ben has superior cell membrane penetration due to its higher log p value. These probes can monitor the overexpression of AChE during apoptosis of lung cancer cells. The ability of BF2-cur-Ben to monitor AChE in vivo was confirmed by a zebrafish experiment.

Advances in surface-enhanced Raman spectroscopy-based sensors for detection of various biomarkers

Surface enhanced Raman spectroscopy (SERS) allows the ultrasensitive detection of analytes present in traces or even single molecule levels by the generation of electromagnetic fields. It is a powerful vibrational spectroscopic method that is capable to detect traces of chemical and biological analytes. SERS technique is involved in the extremely sophisticated studies of molecules with high specificity and sensitivity. In the vicinity of nanomaterials decorated surfaces, SERS can monitor extremely low concentrations of analytes in a non-destructive manner with narrow line widths. This review article is focused on some recently developed SERS-based sensors for distinct types of analytes like disease-related biomarkers, organic and inorganic molecules, various toxins, dyes, pesticides, bacteria as well as single molecules. This study aims to enlighten the arising sensing approaches based on the SERS technique. Apart from this, some basics of the SERS technique like their mechanism, detection strategy, and involvement of some specific nanomaterials are also highlighted herein. Finally, the study concluded with some discussion of applications of SERS in various fields like food and environmental analysis.

In-field deployable and facile nanosensor for the detection of pesticides residues

Local air and water should be first priority to understand the environment of any area. Different categories of contaminants behave like bottleneck situation in collection and analysis of data about abiotic factors for the understanding and resolving the environmental issues. In digital age the emerging nano technology enroll its role to meet the needs of hour. Due to increase in pesticides residues, the global health threats are on bloom because it inhibits the functionality of acetylcholinesterase (AChE) enzyme. Smart nanotechnology based system can tackle this issue and sense the pesticides residues in environment and vegetables as well. Here Au@ZnWO₄ composite is reported, for accurate detection of pesticides residues in biological food and environmental samples. The fabricated unique nanocomposite was characterized by SEM, FTIR, XRD and EDX. The characterized material used for the electrochemical detection of organophosphate pesticide (chlorpyrifos), with 1 pM LoD at a signal to noise ratio of 3. The main concern of study is to help out in disease prevention, food safety and ecosystem protection.

A scientometric study on application of electrochemical sensors for detection of pesticide using graphene-based electrode modifiers

Pesticide testing is an important topic in environmental protection and food safety. The development of green, accurate and reliable pesticide residue detection methods is an important technical support for implementing of agricultural quality supervision. Electrochemical sensors are a very promising analytical method for pesticide detection due to their high sensitivity, speed, low cost and portability. Performance enhancement of electrochemical sensors is often accompanied by research advances in materials science. Among them, carbon material is a very important electrode material for the fabrication of electrochemical sensors. The discovery of graphene makes it the most promising candidate among carbon materials for sensor performance enhancement. The topic of this review is the use of graphene-modified electrochemical sensors for pesticide detection in the last decade. Traditional literature summaries and bibliometric analyses were used for an in-depth analysis of this topic. In addition to the introduction of different sensor types and performance comparisons, this review also parses the authors' country, keywords and publication frequency. The related research experienced rapid growth several years ago and has now reached a relatively stable stage. We also discuss the perspectives on this topic.

Recent advances on rapid detection and remediation of environmental pollutants utilizing nanomaterials-based (bio)sensors

Environmental safety has become a significant issue for the safety of living species, humans, and the ecosystem as a consequence of the harmful and detrimental consequences of various pollutants such as pesticides, heavy metals, dyes, etc., emitted into the surroundings. To resolve this issue, various efforts, legal acts, scientific and technological perspectives have been embraced, but still remain a global concern. Furthermore, due to non-portability, complex detection, and inappropriate on-site recognition of sophisticated laboratory tools, the real-time analysis of these environmental contaminants has been limited. As a result of innovative nano bioconjugation and nanofabrication techniques, nanotechnology enables enhanced nanomaterials (NMs) based (bio)sensors demonstrating ultra-sensitivity and a short detection time in real-time analysis, as well as superior sensitivity, reliability, and selectivity have been developed. Several researchers have demonstrated the potent detection of pollutants such as Hg²⁺ ion by the usage of AgNP-MD in electronic and optoelectronic methods with a detection limit of 5-45 μM which is quite significant. Taking into consideration of such tremendous research, herein, the authors have highlighted 21st-century strategies towards NMs based biosensor technology for pollutants detection, including nano biosensors, enzyme-based biosensors, electrochemical-based biosensors, carbon-based biosensors and optical biosensors for on-site identification and detection of target analytes. This article will provide a brief overview of the significance of utilizing NMs-based biosensors for the detection of a diverse array of hazardous pollutants, and a thorough understanding of the detection processes of NMs-based biosensors, as well as the limit of quantification (LOQ) and limit of detection (LOD) values, rendering researchers to focus on the world's need for a sustainable earth.

Development of Nanomaterial-Modified Impedimetric Aptasensor—A Single-Step Strategy for 3,4-Methylenedioxymethylamphetamine Detection

Developing rapid, sensitive detection methods for 3,4-Methylenedioxymethylamphetamine (MDMA) is crucial to reduce its current misuse in the world population. With that aim, we developed an aptamer-modified tin nanoparticle (SnNP)-based nanoarchitecture as an electrochemical sensor in this study. This platform exhibited a high electron transfer rate with enhanced conductivity arising from its large surface area in comparison to the bare electrode. This observation was explained by the 40-fold higher electroactive surface area of SnNPs@Au, which provided a large space for 1.0 μM Apt_MDMA (0.68 ± 0.36 × 10¹² molecule/cm²) immobilization and yielded a significant electrochemical response in the presence of MDMA. Furthermore, the Apt_MDMA-modified SnNPs@Au sensing platform proved to be a simple yet ultrasensitive analytical device for MDMA detection in spiked biological and water samples. This novel electrochemical aptasensor showed good linearity in the range of 0.01–1.0 nM for MDMA (R² = 0.97) with a limit of detection of 0.33 nM and a sensitivity of 0.54 ohm/nM. In addition, the device showed high accuracy and stability along with signal recoveries in the range of 92–96.7% (Relative Standard Deviation, RSD, 1.1–2.18%). In conclusion, the proposed aptasensor developed here is the first to combine SnNPs and aptamers for illicit compound detection, and it offers a reliable platform for recreational drug detection.

New analytical strategies Amplified with 2D carbon nanomaterials for electrochemical sensing of food pollutants in water and soils sources

Pharmaceutical and food pollutants have threatened global health. Pharmacotherapy has left a positive impression in the field of health and life of people and animals. However, the many unresolved problems brought along with residues of pharmaceuticals in the environmental and food. Consumption of the world's freshwater resources, toxic chemicals, air pollution, plastic waste directly affects water and soil resources. Pesticides have a wide role in pollutants. Therefore, the determination of pesticides is significant to eliminate their negative effects on living things. Nowadays, there are many analytical methods available. However, new analysis methods are still being researched due to certain limitations of traditional methods. Electrochemical sensors have drawn attention because of their superior properties, such as short analysis time, affordability, high sensitivity, and selectivity. The development of new analytical strategies for assessing risks from pharmaceutical to food pollutants in water and soil sources is important for the measurement of different pollutants. Moreover, the 2D-carbon nanomaterials used in the development of electrochemical sensors are widely utilized to enlarge the surface area, increase porosity, and make easy immobilization. Graphene (graphene derivations) and carbon nanotubes integrated nanosensors are widely used for the determination of pesticides. 2D-carbon nanomaterials can be tailored according to the purpose of the study. The characterization and synthesis methods of 2D-carbon nanomaterials are widely explained. Furthermore, enzyme nanobiosensors, especially Acetylcholinesterase (AChE), are widely used to determine pesticides. The three main topics are focused on in this review: 2D-carbon nanomaterials, pesticides that threaten life, and the application of 2D-carbon nanomaterials-based electrochemical sensors. The various developed 2D-carbon nanomaterials-based electrochemical sensors were applied in pharmaceutical forms, fruits, tap/lake water, beverages, and soils sources. This work aims to indicate the recently published paper related to pesticide analysis and highlight the importance of 2D-nanomaterials on sensors.

Progress in Nanomaterials-Based Enzyme and Aptamer Biosensor for the Detection of Organophosphorus Pesticides

With the improvement of people's safety awareness, the requirement of pesticide detection is gradually increasing, and many new detection methods toward Organophosphorus pesticide (OPs) has been further developed and applied. Nanomaterials-based biosensors have played an important role in the trace detection of OPs. This article mainly introduces the detection principle of enzymes and aptamers as the identification element of biosensors. Various nanomaterials (i.e., metals and metal oxides, carbon nanotubes, graphene and graphene oxide, quantum dots, metal organic frameworks, molecular imprinted polymers, etc.) possess their unique properties and play different roles in the enzyme and aptamer-based biosensors toward OPs: (a) to produce the optical or electrochemical signal; (b) as a carrier to load the enzyme or aptamer; (c) to enhance the signal response. Besides, the intelligent portable devices provide the possibility to realize the onsite and real-time detection. The limitations of some nanomaterials and the future development are discussed. Finally, the future of enzyme and aptamer-based biosensors has prospected.

Gap controlled self-assembly Au@Ag@Au NPs for SERS assay of thiram

Thiram (TRM), one dithiocarbamate fungicide, is hazardous due to its ever-growing threat to our production and living. In order to detecting TRM more sensitively, a subtle surface-enhanced Raman scattering (SERS) substrate was reported to achieve TRM detection based on oil-water biphasic self-assembly interface of multi-interstitial Au@Ag@Au NPs crosslinking with 4,4' -Diamino-p-Terphenyl (DATP). This Au@Ag@Au@DATP array shows a noteworthy enhanced Raman signal and stability by controlling the inter-particle spacing of Au@Ag@Au NPs, which overcomes problems of traditional randomly self-assembly methods without cross linker. The Au@Ag@Au@DATP array attained the limit of detection (LOD) of 7.56 × 10^-3 ppb for TRM. In addition, this work gives a new approach for controlling gap of SERS hot spot, which have distinct potential in rapid assessment and identification of pesticides on foods.

Design, Elaboration, and Characterization of an Immunosensor for the Detection of a Fungal Toxin in Foodstuff Analyses

This work describes the complete elaboration of an immunosensor for the detection of the fungal B1 aflatoxin (AFB1). In a first step, a system made of three screen-printed electrodes (SPEs) was manufactured using gold, silver/silver chloride, and carbon pastes. Raman spectroscopy showed that the thermal treatment applied to the electrodes enabled a strong decrease in the amount of undesirable organic molecules for each paste. Atomic Force Microscopy was also used to reveal the morphology of the electrode surfaces. In a second step, an autonomous and cheap electronic system was designed for the control of the sensor and electrochemical measurements, showing current variations significantly higher than those observed with a commercial system. In a last step, the gold working electrode of this system was functionalized by a simple self-assembly method, optimized in a previous work, with a molecular architecture including an antibody recognizing specifically AFB1. The complete device was finally realized by combining the SPEs and the electronic platform. The resulting setup was able to detect AFB1 toxin in a buffer with an LOD of about 50 fg/mL. It was then applied to the detection of AFB1 in rice milk, a more realistic medium comparable with those met in an agrifood context. The electrochemical detection of AFB1 was possible in a range of concentration between 0.5 pg/mL and 2.5 pg/mL, with the sensor behaving linearly in this range.

Highly Sensitive Detection of the Insecticide Azamethiphos by Tris(2,2'-bipyridine)ruthenium(II) Electrogenerated Chemiluminescence

Azamethiphos (AZA) is an insecticide and neurotoxic agent that causes the inhibition of acetylcholinesterase (AChE). AChE is a vital enzyme for neurotransmission because it metabolizes acetylcholine neurotransmitter at the synaptic cleft and terminates synaptic transmission. It is worth mentioning that organophosphates and carbamates inhibit AChE. These AChE inhibitors bind to the active site of the enzyme and inactivate it, leading to paralysis and death. Herein, for the first time, we develop a sensitive, low-cost, and rapid electrogenerated chemiluminescence (ECL) system for the detection of AZA. The designed ECL sensor was applied for the highly sensitive detection of AZA with a wide dynamic range (from 0.1 μM to 1000 μM) and low detection limit of 0.07 μM (S/N = 3). The practical utility of the sensor demonstrates high recoveries (96-102%) in real samples of lake water and wastewater.

Recent advances in nanoremediation: Carving sustainable solution to clean-up polluted agriculture soils

Agriculture is one of the foremost significant human activities, which symbolizes the key source for food, fuel and fibers. This activity results in a lot of ecological harms particularly with the excessive usage of chemical fertilizers and pesticides. Different agricultural practices have remained industrialized to advance food production, due to the growth in the world population and to meet the food demand through the routine use of more effective fertilizers and pesticides. Soil is intensely embellished by environmental contamination and it can be stated as "universal incline." Soil pollution usually occurs from sewage wastes, accidental discharges or as byproducts of chemical residues of unrestrained production of numerous materials. Soil pollution with hazardous materials alters the physical, chemical, and biological properties, causing undesirable changes in soil fertility and ecosystem. Engineered nanomaterials offer various solutions for remediation of contaminated soils. Engineered nanomaterial-enable technologies are able to prevent the uncontrolled release of harmful materials into the environment along with capabilities to combat soil and groundwater borne pollutants. Currently, nanobiotechnology signifies a hopeful attitude to advance agronomic production and remediate polluted soils. Studies have outlined the way of nanomaterial applications to restore the eminence of the environment and assist the detection of polluted sites, along with potential remedies. This review focuses on the latest developments in agricultural nanobiotechnology and the tools developed to combat soil or land and or terrestrial pollution, as well as the benefits of using these tools to increase soil fertility and reduce potential toxicity.

Emerging vistas on pesticides detection based on electrochemical biosensors - An update

Organophosphates and carbamates pesticides are widely used to increase crop production globally causing a threat to human health and the environment. A variety of pesticides are applied during different stages of vegetable production. Therefore, monitoring the presence of pesticide residues in food and soil has great relevance to sensitive pesticide detection through distinct determination methods that are urgently required. Conventional techniques for the detection of pesticides have several limitations that can be overcome by the development of highly sensitive, fast, reliable and easy-to-use electrochemical biosensors. Herein, we describe the types of biosensors with the main focus on electrochemical biosensors fabricated for the detection of OPPs and carbamates pesticides. An overview of conventional techniques employed for pesticide detection is also discussed. This review aims to provide a glance of recently developed biosensors for some common pesticides like chlorpyrifos, malathion, parathion, paraoxon, and carbaryl which are present in food and environment samples.

A Novel Integrated APCI and MPT Ionization Technique as Online Sensor for Trace Pesticides Detection

The misuse of pesticides poses a tremendous threat to human health. Excessive pesticide residues have been shown to cause many diseases. Many sensor detection methods have been developed, but most of them suffer from problems such as slow detection speed or narrow detection range. So, the development of rapid, direct and sensitive means of detecting trace amounts of pesticide residues is always necessary. A novel online sensor technique was developed for direct analysis of pesticides in complex matrices with no sample pretreatment. The portable sensor ion source consists of an MPT (microwave plasma torch) with desolventizing capability and an APCI (atmosphere pressure chemical ionization), which provides abundant precursor ions and a strong electric field. The performance which improves the ionization efficiency and suppresses the background signal was verified by using pesticide standard solution and pesticide pear juice solution measurements with an Orbitrap mass spectrometer. The limit of detection (LOD) and the limit of quantization (LOQ) of the method were measured by pear juice solutions that were obtained in the ranges of 0.034-0.79 μg/L and 0.14-1 μg/L. Quantitative curves were obtained ranging from 0.5 to 100 μg/L that showed excellent semi-quantitative ability with correlation coefficients of 0.985-0.997. The recoveries (%) of atrazine, imidacloprid, dimethoate, profenofos, chlorpyrifos, and dichlorvos were 96.6%, 112.7%, 88.1%, 85.5%, 89.2%, and 101.9% with the RSDs ranging from 5.89-14.87%, respectively. The results show that the method has excellent sensitivity and quantification capability for rapid and direct detection of trace pesticide.

Aptamer Recognition-Driven Homogeneous Electrochemical Strategy for Simultaneous Analysis of Multiple Pesticides without Interference of Color and Fluorescence

Credible and simultaneous determination of multiple pesticides is highly desirable for guaranteeing food safety. However, the current methods are limited to significant interference of color and fluorescence or electrode's modification and mainly focus on the analysis of a single pesticide. Herein, we proposed a novel aptamer-based homogeneous electrochemical system for highly sensitive and simultaneous analysis of multiple pesticides based on target pesticide-switched exonuclease III (Exo III)-assisted signal amplification. The recognition of hairpin probes by target pesticides impels the production of pesticide-DNA complexes, which hybridize with electroactive dye-labeled DNA to form double-stranded DNA, subsequently initiating an Exo III-assisted digestion reaction to generate abundant electroactive dye-tagged mononucleotides. In comparison with pesticide deficiency, two higher differential pulse voltammetry (DPV) currents are measured, which rely on the amount of target pesticides. Therefore, simultaneous analysis of two pesticides is realized with limits of detection of 0.0048 and 0.0089 nM, respectively, comparable or superior to those of known methods that focused on a single pesticide. Moreover, the proposed system is successfully employed to simultaneously evaluate the residual level of acetamiprid and profenofos in Brassica chinensis and thus will find more useful applications for pesticide-related food safety.

Colorimetric detection of acetylcholinesterase and its inhibitor based on thiol-regulated oxidase-like activity of 2D palladium square nanoplates on reduced graphene oxide

A convenient and sensitive colorimetric assay for acetylcholinesterase (AChE) and its inhibitor has been designed based on the oxidase-like activity of {100}-faceted Pd square nanoplates which are grown in situ on reduced graphene oxide (PdSP@rGO). PdSP@rGO can effectively catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) without the assistance of H₂O₂ to generate blue oxidized TMB (oxTMB) with a characteristic absorption peak at 652 nm. In the presence of AChE, acetylthiocholine (ATCh), a typical AChE substrate, is hydrolyzed to thiocholine (TCh). The generated TCh can effectively inhibit the PdSP@rGO-triggered chromogenic reaction of TMB via cheating with Pd, resulting in color fading and decrease in absorbance. Thus, a sensitive probe for AChE activity is constructed with a working range of 0.25-5 mU mL^-1 and  a limit of detection (LOD) of 0.0625 mU mL^-1. Furthermore, because of the inhibition effect of tacrine on AChE, tacrine is also detected through the colorimetric AChE assay system within the concentrations range 0.025-0.4 μM with a LOD of 0.00229 μM. Hence, a rapid and facile colorimetric procedure to sensitively detect AChE and its inhibitor can be anticipated through modulating the oxidase-like activity of PdSP@rGO. Colorimetric method for detection of AChE and its inhibitor is established by modulating the oxidase mimetic activity of {100}-faceted Pd square nanoplates on reduced graphene oxide (PdSP@rGO).

Detection of organophosphorus pesticides by nanogold/mercaptomethamidophos multi-residue electrochemical biosensor

Based on the successful synthesis of mercaptomethamidophos as a substrate, a novel nanogold/mercaptomethamidophos multi-residue electrochemical biosensor was designed and fabricated by combining nanoscale effect, strong Au-S bonds as well as interaction between acetylcholinesterase (AChE) and mercaptomethamidophos, which can simultaneously detect 11 kinds of organophosphorus pesticides (OPPs) and total amount of OPPs using indirect competitive method. Electrochemical behavior of the modified electrode was characterized by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The AChE concentration and incubation time were optimized at 37.4 °C to achieve the best detection effect. This biosensor exhibits excellent electrochemical properties with a wider linear range of 0.1 ~ 1500 ng·mL^-1, lower detection limit of 0.019 ~ 0.077 ng·mL^-1, better stability and repeatability, which realizes the rapid detection of total amount of OPPs, and can simultaneously detect a large class of OPPs rather than one kind of OPP. Two OPPs (trichlorfon, dichlorvos) were detected in actual samples of apple and cabbage and achieved satisfactory test results.

Pesticide Aptasensors-State of the Art and Perspectives

Contamination by pesticides in the food chain and the environment is a worldwide problem that needs to be actively monitored to ensure safety. Unfortunately, standard pesticide analysis based on mass spectrometry takes a lot of time, money and effort. Thus, simple, reliable, cost-effective and field applicable methods for pesticide detection have been actively developed. One of the most promising technologies is an aptamer-based biosensor or so-called aptasensor. It utilizes aptamers, short single-stranded DNAs or RNAs, as pesticide recognition elements to integrate with various innovative biosensing technologies for specific and sensitive detection of pesticide residues. Several platforms for aptasensors have been dynamically established, such as colorimetry, fluorometry, electrochemistry, electrochemiluminescence (ECL) and so forth. Each platform has both advantages and disadvantages depending on the purpose of use and readiness of technology. For example, colorimetric-based aptasensors are more affordable than others because of the simplicity of fabrication and resource requirements. Electrochemical-based aptasensors have mainly shown better sensitivity than others with exceedingly low detection limits. This paper critically reviews the progression of pesticide aptasensors throughout the development process, including the selection, characterization and modification of aptamers, the conceptual frameworks of integrating aptamers and biosensors, the ASSURED (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free and deliverable to end users) criteria of different platforms and the future outlook.