Ti3C2 MXene/MoS2@AuNPs ternary nanocomposite for highly sensitive electrochemical detection of phoxim residues in fruits

Phoxim, extensively utilized in agriculture as an organothiophosphate insecticide, has the potential to cause neurotoxicity and pose human health hazards. In this study, an electrochemical enzyme biosensor based on Ti3C2 MXene/MoS2@AuNPs/AChE was constructed for the sensitive detection of phoxim. The two-dimensional multilayer structure of Ti3C2 MXene provides a robust framework for MoS2, leading to an expansion of the specific surface area and effectively preventing re-stacking of Ti3C2 MXene. Additionally, the synergistic effect of self-reduced grown AuNPs with MoS2 further improves the electrical conductivity of the composites, while the robust framework provides a favorable microenvironment for immobilization of enzyme molecules. Ti3C2 MXene/MoS2@AuNPs electrochemical enzyme sensor showed a significant response to phoxim in the range of 1 × 10-13 M to 1 × 10-7 M with a detection limit of 5.29 × 10-15 M. Moreover, the sensor demonstrated excellent repeatability, reproducibility, and stability, thereby showing its promising potential for real sample detection.

From challenge to opportunity: Revolutionizing the monitoring of emerging contaminants in water with advanced sensors

Emerging contaminants in water represent long-term and unpredictable threats to both environmental and human health due to their persistence and bioaccumulation. Current research predominantly focuses on their removal rather than sustained monitoring. This review comprehensively investigates advanced sensor technologies for detecting these contaminants in water, critically evaluating biosensors, optical sensors, electrochemical sensors, and nanomaterial sensors. Elucidating the operational principles, performance metrics such as detection thresholds, and the pros and cons of their practical applications, the review addresses a significant research gap in environmental monitoring. Moreover, it enhances understanding of sensor effectiveness, which in turn guides researchers in selecting the right sensor types for various environmental scenarios. Furthermore, by emphasizing the integration of nanotechnology and the standardization of evaluation protocols, it promotes the development of robust, deployable sensing solutions. Ultimately, this leads to the proposal of a strategic framework aimed at significantly improving the detection capabilities of emerging contaminants and supporting the preservation of environmental health.

A portable acetylcholinesterase-based electrochemical sensor for field detection of organophosphorus

A portable acetylcholinesterase (AChE)-based electrochemical sensor based on a screen-printed carbon electrode (SPCE) and a miniature potentiostat was constructed for the rapid field detection of organophosphorus pesticides (OPs). Graphene (GR) and gold nanoparticles (AuNPs) were successively introduced onto SPCE for surface modification. Due to the synergistic effect of the two nanomaterials, the signal of the sensor has a significant enhancement. Take isocarbophos (ICP) as a model for chemical warfare agents (CAWs) and Ops; the SPCE/GR/AuNPs/AChE/Nafion sensor shows a wider linear range (0.1-2000 μg L-1), and a lower limit of detection (0.012 μg L-1) than SPCE/AChE/Nafion and SPCE/GR/AChE/Nafion sensors. Tests in actual fruit and tap water samples also yielded satisfactory results. Therefore, the proposed method can be used as a simple and cost-effective strategy for construction of portable electrochemical sensors for OP field detection.

Oriented Design of Transition-Metal-Oxide Hollow Multishelled Micropolyhedron Derived from Bimetal-Organic Frameworks for the Electrochemical Detection of Multipesticide Residues

Transition-metal oxides (TMOs) with a hollow multishelled structure have emerged as highly potential materials for high-performance electrochemical sensing, benefiting from their superior electronic conductivity, exceptionally large specific surface area, excellent stability, and electrochemistry properties. In particular, binary TMOs are expected to outperform unitary TMOs due to the synergistic effect of the different metals. Herein, MnCo₂O_4.5 hollow quadruple-shelled porous micropolyhedrons (MnCo₂O_4.5 HoQS-MPs) were prepared and employed to construct an ultrasensitive sensing platform for a multipesticide assay. Profiting from complex hollow interior structures and abundant active sites, the MnCo₂O_4.5 HoQS-MPs manifest outstanding electrochemical properties as electrode materials for the pesticide assay. The MnCo₂O_4.5 HoQS-MP-based biosensor demonstrated remarkable performance for monocrotophos, methamidophos, and carbaryl detection, with wide linear ranges, as well as low detection limits. This work unveils a new pathway for the ultrasensitive detection of pesticides and demonstrates tremendous potential for detecting other environmentally deleterious chemicals.

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.

Electrochemical detection of methyl-paraoxon based on bifunctional cerium oxide nanozyme with catalytic activity and signal amplification effect

A new electrochemical sensor for organophosphate pesticide (methyl-paraoxon) detection based on bifunctional cerium oxide (CeO₂) nanozyme is here reported for the first time. Methyl-paraoxon was degraded into p-nitrophenol by using CeO₂ with phosphatase mimicking activity. The CeO₂ nanozyme-modified electrode was then synthesized to detect p-nitrophenol. Cyclic voltammetry was applied to investigate the electrochemical behavior of the modified electrode, which indicates that the signal enhancement effect may attribute to the coating of CeO₂ nanozyme. The current research also studied and discussed the main parameters affecting the analytical signal, including accumulation potential, accumulation time, and pH. Under the optimum conditions, the present method provided a wider linear range from 0.1 to 100 μmol/L for methyl-paraoxon with a detection limit of 0.06 μmol/L. To validate the proof of concept, the electrochemical sensor was then successfully applied for the determination of methyl-paraoxon in three herb samples, i.e., Coix lacryma-jobi, Adenophora stricta and Semen nelumbinis. Our findings may provide new insights into the application of bifunctional nanozyme in electrochemical detection of organophosphorus pesticide.

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A new electrochemical method for methyl-paraoxon detection by using bifunctional nanozyme was presented.

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The cerium oxide nanozyme modified glassy carbon electrode was prepared to improve the sensitivity.

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The developed method has been successfully applied in three herbal plant samples.

Magnetic nanomaterials based electrochemical (bio)sensors for food analysis

It is widely accepted that nanotechnology attracted more interest because of various values that nanomaterial applications offers in different fields. Recently, researchers have proposed nanomaterials based electrochemical sensors and biosensors as one of the potent alternatives or supplementary analytical tools to the conventional detection procedures that consumes a lot of time. Among different nanomaterials, researchers largely considered magnetic nanomaterials (MNMs) for developing and fabricating the electrochemical (bio)sensors for numerous utilizations. Among several factors, healthier and higher quality foods are the most important preferences of consumers and manufacturers. For this reason, developing new techniques for rapid, precise as well as sensitive determination of components or contaminants of foods is very important. Therefore, developing the new electrochemical (bio)sensors in food analysis is one of the key and effervescent research fields. In this review, firstly, we presented the properties and synthesis strategies of MNMs. Then, we summarized some of the recently developed MNMs-based electrochemical (bio)sensors for food analysis including detecting the antioxidants, synthetic food colorants, pesticides, heavy metal ions, antibiotics and other analytes (bisphenol A, nitrite and aflatoxins) from 2010 to 2020. Finally, the present review described advantages, challenges as well as future directions in this field.

Novel Au-tetrahedral aptamer nanostructure for the electrochemiluminescence detection of acetamiprid

In this work, an ultrasensitive and selective electrochemiluminescence (ECL) aptasensor with Au-tetrahedral aptamer nanostructure (Au-TAN) for acetamiprid detection was developed, which employed luminescence property of luminol and hydrogen peroxide (H₂O₂) as a co-reactant to apply the prepared Au-TAN to the luminescence systems. Au-TAN was prepared to modify an electrode surface via an Au-S bond to form a stable tetrahedral nanostructure. Fixed on the surface of the working electrode, Au-TAN could not only enhance the function of the aptamer but also boost the sensing performance. At the same time, Au nanoparticles (AuNPs) of the Au-TAN could also catalyze H₂O₂, thereby enhancing the luminescence performance of this aptasensor. The pH of the buffer solution, the concentration of H₂O₂ and the concentration of Au-TAN were optimized. Under the optimal conditions, the aptasensor had a detection limit of 0.0576 pM (S/N = 3), which was lower than those of other aptasensors for acetamiprid detection. Moreover, the weak alkaline environment explored in the experiment could expand its application range. Above all, the proposed method presented a high accuracy and sensitivity.

Preparation, surface functionalization and application of Fe3O4 magnetic nanoparticles

This paper reviews recent developments in the preparation, surface functionalization, and applications of Fe₃O₄ magnetic nanoparticles. Especially, it includes preparation methods (such as electrodeposition, polyol methods, etc.), organic materials (such as polymers, small molecules, surfactants, biomolecules, etc.) or inorganic materials (such as silica, metals, and metal oxidation/sulfide, functionalized coating of carbon surface, graphene, etc.) and its applications (such as magnetic separation, protein fixation, magnetic catalyst, environmental treatment, medical research, etc.). In the end, some existing challenges and possible future trends in the field were discussed.

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

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

Voltammetric determination of organophosphorus pesticides using a hairpin aptamer immobilized in a graphene oxide-chitosan composite

An aptasensor is described for electrochemical determination of organophosphorus pesticides (OPPs), specifically of profenofos, phorate, isocarbophos, and omethoate. The method uses a hairpin aptamer as signalling donor. Its 5' and 3' ends were modified with amino groups and the redox probe ferrocene (Fc), respectively. A nanocomposite consisting of graphene oxide and chitosan (GO-chit) was used to immobilize the aptamer via formation of an amide link. Its good conductivity facilitates monitoring of the electrochemical responses. Upon addition of an OPP, it will be bound by the aptamer. This results in an opening of the hairpin structure. Thus, Fc is shifted away from the surface of the electrode. As a result, the impedance increases and the redox signal of Fc decreases. The electrochemical performance, binding capacity and response of the aptasensor for profenofos, phorate, isocarbophos and omethoate were studied. The limits of detection are as low as 0.01, 0.1, 0.01 and 0.1 nM, respectively. Graphical abstract Schematic representation of an electrochemical aptasensor prepared by immobilizing ferrocene (Fc) labeled hairpin aptamer (HP) on the surface of graphene oxide-chitosan (GO-chit) modified electrode, and its application to the determination of organophosphorus pesticides (OPPs) by voltammetry.

Oligonucleotides and pesticide regulated peroxidase catalytic activity of hemin for colorimetric detection of isocarbophos in vegetables by naked eyes

A novel colorimetric sensing platform based on the peroxidase activity of hemin regulated by oligonucleotide and pesticide was reported for the ultrasensitive and selective detection of isocarbophos. Oligonucleotides can accumulate on the surface of hemin in acid condition and temporarily inhibit its catalytic activity, which results in the loss of one electron of TMB molecule and produce the blue products. With the addition of isocarbophos, the pesticide molecules can interact with oligonucleotides to form some complexes, which relieve the inhibition of ssDNA to hemin and further enhance its catalytic activity. Thus, the TMB molecules are further oxidized to lose another electron and produce the yellow product in a few minutes, which has the characteristic absorption peak at 450 nm. The color change of the sensing system is related to the amount of isocarbophos, so this method can quickly discriminate whether the target pesticide exceeds the maximal residue limit just by naked eyes. To improve the performance of sensing platform, some important parameters like buffer condition and ssDNA have been investigated, and the peroxidase activity of hemin was further studied to verify the catalytic mechanism. The proposed sensing platform has a detection limit as low as 0.6 μg/L and displays good selectivity against other competitive pesticides. Moreover, the developed sensing platform also exhibits favorable accuracy and stability, indicating that it has potential applications in the detection of pesticide residues in agricultural products. Graphical abstract A novel colorimetric sensing platform based on oligonucleotides and pesticide regulation; the peroxidase catalytic activity of hemin was firstly reported for the ultrasensitive and selective detection of isocarbophos pesticide.

Monocrotophos detection with a bienzyme biosensor based on ionic-liquid-modified carbon nanotubes

Acetylcholinesterase (AChE) biosensor technology is widely applied in the detection of organophosphate pesticides in agricultural production via the inhibition of AChE activity by organophosphates. However, the AChE electrode has some drawbacks, such as low stability and high overpotential. Combining the advantages of multiwalled carbon nanotubes (MWCNTs) and ionic liquids, we constructed a novel bienzyme electrode [Cl/iron porphyrin (FePP)-modified MWCNTs/AChE/glassy carbon electrode], which included AChE and mimetic oxidase FePP. In this electrode, FePP is covalently bound to the AChE carrier via ionic liquid for increased electrode sensitivity and stability. Under optimal conditions, this novel biosensor has a monocrotophos detection limit of 3.2 × 10-11 mol/L and good recovery of 89-104%. After 5 weeks of storage at 4 °C, the oxidation current was 97.8% of its original value. The biosensor has high stability and sensitivity for monocrotophos detection and is a promising device for monitoring food safety. Graphical abstract The complete synthesis process of Cl/FePP-MWCNTs/AChE/GCE.

Voltammetric Biosensor Based on Nitrogen-doped Ordered Mesoporous Carbon for Detection of Organophosphorus Pesticides in Vegetables

Background:

Pesticides residues in agricultural products have posed a serious threat to food safety and human health, so it is necessary to develop a rapid and accurate method to detect pesticide in the environment. N-OMC with excellent electroconductivity, high biocompatibility and the functional amino group that can be covalently attached to the enzyme can be applied to construct a sensitive and stable acetylcholinesterase biosensor for rapid and accurate detection of organophosphorus pesticides with the help of L-cysteine self-assembled monolayer and AuNPs.

Methods:

Transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption measurements are used to characterize materials. Electrochemical impedance spectroscopy and cyclic voltammetry are used to study the surface features of modified electrodes. Differential pulse voltammetric is used to measure the peak current of modified electrodes. GC-MS is applied to verify the reliability of the prepared biosensor for organophosphorus pesticides detection.

Results:

N-OMC was synthesized and applied to constructed stable and sensitive acetylcholinesterase biosensors. The combination of N-OMC, L-cysteine self-assembled monolayer and AuNPs to modify the electrode surface has greatly improved the conductivity of biosensor and provided a stable platform for acetylcholinesterase immobilization. The linear detection range of paraoxon was from 3 to 24 nM with a lower detection limit of 0.02 nM.

Conclusion:

The biosensor exhibited satisfactory reproducibility, repeatability and stability, and was successfully employed to determine the paraoxon in vegetables as well as tap water samples, providing a promising tool for rapid and sensitive detection of organophosphorus pesticides in agricultural products.

Metallic Transition Metal Dichalcogenide Nanosheets as an Effective and Biocompatible Transducer for Electrochemical Detection of Pesticide

Owing to their large specific surface, favorable electrical conductivity, and excellent electrocatalytic capabilities, two-dimensional transition metal dichalcogenides have received considerable attention in the field of biosensors. On the basis of these properties, we developed a portable and disposable enzyme-based biosensor for paraoxon detection using a metallic MoS₂ nanosheets modified screen-printed electrode (SPE). The exfoliated ultrathin metallic MoS₂ nanosheets can accelerate the electron transfer on electrode surface and contribute to the immobilization of acetylcholinesterase (AChE) via the cross-linking of glutaraldehyde. Electrodeposited gold nanoparticles (AuNPs) on SPE were used to immobilize MoS₂ nanosheets through the interaction between Au atoms on AuNPs and S atoms on MoS₂. Using acetylcholine as the substrate, AChE can catalyze the formation of electroactive thiocholine and further generate the redox current. In the presence of paraoxon, the activity of AChE can be inhibited, making the related electrochemical signals weaken. Under the optimized conditions, this electrochemical biosensor exhibited a favorable linear relationship with the concentration of paraoxon from 1.0 to 1000 μg L^-1, with the detection limit of 0.013 μg L^-1. Furthermore, this developed biosensor was successfully applied to detect paraoxon in pretreated apple and pakchoi samples, which can provide a reliable method for the rapid analysis of organophosphorus pesticides in agricultural products.

Recent Developments in Enzyme, DNA and Immuno-Based Biosensors

Novel sensitive, rapid and economical biosensors are being developed in a wide range of medical environmental and food applications. In this paper, we review some of the main advances in the field over the past few years by discussing recent studies from literature. A biosensor, which is defined as an analytical device consisting of a biomolecule, a transducer and an output system, can be categorized according to the type of the incorporated biomolecule. The biomolecules can be enzymes, antibodies, ssDNA, organelles, cells etc. The main biosensor categories classified according to the biomolecules are enzymatic biosensors, immunosensors and DNA-based biosensors. These sensors can measure analytes produced or reduced during reactions at lower costs compared to the conventional detection techniques. Numerous types of biosensor studies conducted over the last decade have been explored here to reveal their key applications in medical, environmental and food industries which provide comprehensive perspective to the readers. Overviews of the working principles and applications of the reviewed sensors are also summarized.

Progress in utilisation of graphene for electrochemical biosensors

This review discusses recent graphene (GR) electrochemical biosensor for accurate detection of biomolecules, including glucose, hydrogen peroxide, dopamine, ascorbic acid, uric acid, nicotinamide adenine dinucleotide, DNA, metals and immunosensor through effective immobilization of enzymes, including glucose oxidase, horseradish peroxidase, and haemoglobin. GR-based biosensors exhibited remarkable performance with high sensitivities, wide linear detection ranges, low detection limits, and long-term stabilities. Future challenges for the field include miniaturising biosensors and simplifying mass production are discussed.

Covalent immobilization of acetylcholinesterase on a novel polyacrylic acid-based nanofiber membrane

In this study, polyacrylic acid-based nanofiber (NF) membrane was prepared via electrospinning method. Acetylcholinesterase (AChE) from Electrophorus electricus was covalently immobilized onto polyacrylic acid-based NF membrane by demonstrating efficient enzyme immobilization, and immobilization capacity of polymer membranes was found to be 0.4 mg/g. The novel NF membrane was synthesized via thermally activated surface reconstruction, and activation with carbonyldiimidazole upon electrospinning. The morphology of the polyacrylic acid-based membrane was investigated by scanning electron microscopy, Fourier Transform Infrared Spectroscopy, and thermogravimetric analysis. The effect of temperature and pH on enzyme activity was investigated and maxima activities for free and immobilized enzyme were observed at 30 and 35°C, and pH 7.4 and 8.0, respectively. The effect of 1 mM Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Mg²⁺, Ca²⁺ ions on the stability of the immobilized AChE was also investigated. According to the Michaelis-Menten plot, AChE possessed a lower affinity to acetylthiocholine iodide after immobilization, and the Michaelis-Menten constant of immobilized and free AChE were found to be 0.5008 and 0.4733 mM, respectively. The immobilized AChE demonstrated satisfactory reusability, and even after 10 consecutive activity assay runs, AChE maintained ca. 87% of its initial activity. Free enzyme lost its activity completely within 60 days, while the immobilized enzyme retained approximately 70% of the initial activity under the same storage time. The favorable reusability of immobilized AChE enables the support to be employable to develop the AChE-based biosensors.

Recent Trends on Electrochemical Sensors Based on Ordered Mesoporous Carbon

The past decade has seen an increasing number of extensive studies devoted to the exploitation of ordered mesoporous carbon (OMC) materials in electrochemistry, notably in the fields of energy and sensing. The present review summarizes the recent achievements made in field of electroanalysis using electrodes modified with such nanomaterials. On the basis of comprehensive tables, the interest in OMC for designing electrochemical sensors is illustrated through the various applications developed to date. They include voltammetric detection after preconcentration, electrocatalysis (intrinsically due to OMC or based on suitable catalysts deposited onto OMC), electrochemical biosensors, as well as electrochemiluminescence and potentiometric sensors.

Nanomaterials-based enzyme electrochemical biosensors operating through inhibition for biosensing applications

In recent years great progress has been made in applying nanomaterials to design novel biosensors. Use of nanomaterials offers to biosensing platforms exceptional optical, electronic and magnetic properties. Nanomaterials can increase the surface of the transducing area of the sensors that in turn bring an increase in catalytic behaviors. They have large surface-to-volume ratio, controlled morphology and structure that also favor miniaturization, an interesting advantage when the sample volume is a critical issue. Biosensors have great potential for achieving detect-to-protect devices: devices that can be used in detections of pollutants and other treating compounds/analytes (drugs) protecting citizens' life. After a long term focused scientific and financial efforts/supports biosensors are expected now to fulfill their promise such as being able to perform sampling and analysis of complex samples with interest for clinical or environment fields. Among all types of biosensors, enzymatic biosensors, the most explored biosensing devices, have an interesting property, the inherent inhibition phenomena given the enzyme-substrate complex formation. The exploration of such phenomena is making remarkably important their application as research and applied tools in diagnostics. Different inhibition biosensor systems based on nanomaterials modification has been proposed and applied. The role of nanomaterials in inhibition-based biosensors for the analyses of different groups of drugs as well as contaminants such as pesticides, phenolic compounds and others, are discussed in this review. This deep analysis of inhibition-based biosensors that employ nanomaterials will serve researchers as a guideline for further improvements and approaching of these devices to real sample applications so as to reach society needs and such biosensor market demands.