Exploring pralidoxime chloride as a universal electrochemical probe for organophosphorus pesticides detection

Universal organophosphate pesticides detection by peptide based fluorescent probes

In practical applications, the rapid and efficient detection of universal organophosphorus pesticides (OPs) can assist inspectors in quickly identifying the presence of OPs in samples. However, this presents a challenge for most well-established methods, typically designed to detect only a specific type of organophosphorus molecule at a time. In this proof-of-concept study, we draw inspiration from the structural similarities among OPs to develop innovative peptide-based fluorescence probes for the first time, which could efficiently detect a broad range of OPs within a mere 3 min. Analysis of fluorescence curve fitting reveals a clear linear correlation between the fluorescent intensity of the peptide probes and the concentration of OPs. Additionally, the selectivity analysis indicates that these peptide fluorescent probes exhibit an excellent response to various OPs while maintaining sufficient selectivity for detecting other pesticide types. Accurate sample analysis has also highlighted the potential of these peptide probes as practical tools for the rapid detection of OPs in actual vegetable samples. In summary, this proof-of-concept study presents an innovative approach to designing and developing ultrafast, universally peptide-based OP probes. These custom-designed peptide probes may facilitate rapid sample screening and offer initial quantification for OPs, potentially saving valuable time and effort in practical OP detection.

Rhizosphere bacteria G-H27 significantly promoted the degradation of chlorpyrifos and fosthiazate

Microbial remediation of polluted environments is the most promising and significant research direction in the field of bioremediation. In this study, chlorpyrifos and fosthiazate were selected as representative organophosphorus pesticides, wheat was the tested plant, and fluorescently labeled degrading Bacillus cereus G-H27 were the film-forming bacteria. Exogenous strengthening technology was used to establish degrading bacterial biofilms on the root surface of wheat. The influence of root surface-degrading bacterial biofilms on the enrichment of chlorpyrifos and fosthiazate in wheat was comprehensively evaluated. First, the fluorescently-labeled degrading bacteria G-H27 was constructed, and its film-forming ability was investigated. Second, the growth- promoting characteristics and degradation ability of the bacteria G-H27 were investigated. Finally, the degradation effect of the root surface-degrading bacterial biofilm on chlorpyrifos and fosthiazate was determined. The above research provides an important material basis and method for the bioremediation of pesticide-contaminated soil.

Recent advancements in non-enzymatic electrochemical sensor development for the detection of organophosphorus pesticides in food and environment

Organophosphorus Pesticides (OPPs) are among the extensively used pesticides throughout the world to boost agricultural production. However, persistent residues of these toxic pesticides in various vegetables, fruits, and drinking water poses detrimental health effects. Consequently, the rapid monitoring of these harmful chemicals through simple and cost-effective methods has become crucial. In such an instance, electrochemical methods offer simple, rapid, sensitive, reproducible, and affordable detection pathways. To overcome the limitations associated with electrochemical enzymatic sensors, non-enzymatic sensors have emerged as promising and simpler alternatives. The non-enzymatic sensors have demonstrated superior activity, reaching detection limit up to femto (10-15) molar concentration in recent years, leveraging higher selectivity obtained through the molecularly imprinted polymers, synergistic effects between carbonaceous nanomaterials and metals, metal oxide alloys, and other alternative approaches. Herein, this review paper provides an overview of the recent advancements in the development of non-enzymatic electrochemical sensors for the detection of commonly used OPPs, such as Chlorpyrifos (CHL), Diazinon (DZN), Malathion (MTN), Methyl parathion (MP) and Fenthion (FEN). The design method of the electrodes, electrode functioning mechanism, and their analytical performance metrics, such as limit of detection, sensitivity, selectivity, and linearity range, were reviewed and compared. Furthermore, the existing challenges within this rapidly growing field were discussed along with their potential solutions which will facilitate the fabrication of advanced and sustainable non-enzymatic sensors in the future.

Advances in Microfluidics Techniques for Rapid Detection of Pesticide Residues in Food

Food safety is a significant issue that affects people worldwide and is tied to their lives and health. The issue of pesticide residues in food is just one of many issues related to food safety, which leave residues in crops and are transferred through the food chain to human consumption. Foods contaminated with pesticide residues pose a serious risk to human health, including carcinogenicity, neurotoxicity, and endocrine disruption. Although traditional methods, including gas chromatography, high-performance liquid chromatography, chromatography, and mass spectrometry, can be used to achieve a quantitative analysis of pesticide residues, the disadvantages of these techniques, such as being time-consuming and costly and requiring specialist staff, limit their application. Therefore, there is a need to develop rapid, effective, and sensitive equipment for the quantitative analysis of pesticide residues in food. Microfluidics is rapidly emerging in a number of fields due to its outstanding strengths. This paper summarizes the application of microfluidic techniques to pyrethroid, carbamate, organochlorine, and organophosphate pesticides, as well as to commercial products. Meanwhile, the study also outlines the development of microfluidics in combination with 3D printing technology and nanomaterials for detecting pesticide residues in food.

Detection of organophosphorus pesticides: exploring oxime as a probe with improved sensitivity by CeO2-modified electrode

In this paper, the catalytic activity of CeO₂ NPs toward oxime oxidation was adopted for the first time to develop an electrochemical sensor with improved sensitivity toward the direct detection of organophosphorus pesticides (OPs) without electrochemical redox activity. To enhance the conductivity of the sensor, CeO₂ NPs together with multi-walled carbon nanotubes (MWCNTs) were deposited onto a bare glassy carbon electrode (GCE) by the simple method of drop-casting. The electrochemical properties of the as-prepared sensor were evaluated in K₃[Fe(CN)₆] solution and the oxidation behavior of pralidoxime (PAM) chloride on the electrodes was characterized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results show that the modification of CeO₂ onto the electrode not only increases the electroactive area of the electrode but also significantly increases the peak current of PAM chloride oxidation, which confirms that CeO₂ has an electrocatalytic effect toward oxime oxidation. To evaluate the sensitivity of the as-fabricated sensor, the inhibition rate of PAM chloride peak current was tested in PAM chloride solution containing different concentrations of chlorpyrifos, which shows a very small detection limit of 2.5 × 10^-9 M. In addition, the sensor successfully achieved a convenient and sensitive determination of OPs in vegetable extracts.

High pressure Raman spectra and DFT calculation of glyphosate

Glyphosate, N-(phosphonomethyl)glycine, (C₃H₈NO₅P), was obtained through the method of slow evaporation method from aqueous solution and its structure analyzed through X-ray diffraction and the Rietveld method. The normal modes of the crystal were investigated using Raman spectroscopy and Density Functional Theory to obtain the assignment of most of the normal modes in the spectral range between 3070 and 45 cm^-1. The crystal was compressed to high pressure through a diamond anvil cell, up to 6.2 GPa. From the behavior of the modes corresponding to both internal modes and lattice modes it was possible to discovery two phase transitions undergone by glyphosate, one between 0.97 and 1.5 GPa and other in the pressure interval 4.29-4.63 GPa. The analysis of the Raman spectra also indicates a certain disorder and conformational changes of the molecules in the unit cell at high pressure. Additionally, the phase transitions revealed to be reversible, with no cracking of the sample in the compression - decompression run.

Detection of pollutants in water bodies: electrochemical detection or photo-electrochemical detection?

The massive discharge of pollutants including endocrine-disrupting chemicals (EDCs), heavy metals, pharmaceuticals and personal care products (PPCPs) into water bodies is endangering the ecological environment and human health, and needs to be accurately detected. Both electrochemical and photo-electrochemical detection methods have been widely used for the detection of these pollutants, however, which one is better for the detection of different environmental pollutants? In this feature article, different electrochemical and photo-electrochemical detection methods are summarized, including the principles, classification, common catalysts, and applications. By summarizing the advantages and disadvantages of different detection methods, this review provides a guide for other researchers to detect pollutants in water bodies by using electrochemical and photo-electrochemical analysis.

Enhancing the Sensitivity of the Bio-barcode Immunoassay for Triazophos Detection Based on Nanoparticles and Droplet Digital Polymerase Chain Reaction

An ultrasensitive bio-barcode competitive immunoassay method based on droplet digital polymerase chain reaction (ddPCR) was developed for the determination of triazophos. Gold nanoparticles (AuNPs) were coated with monoclonal antibodies (mAbs) and complementary double-stranded DNA (dsDNA), which included bio-barcode DNA and thiol-capped DNA. Magnetic nanoparticle (MNP) probes were constructed by modifying the MNPs with ovalbumin-hapten conjugates (OVA-hapten). The target pesticide and OVA-hapten on the surface of the MNP probes competed with the AuNP probes simultaneously, and then the bio-barcode DNA was released for quantification by ddPCR. The concentration of released DNA was inversely proportional to the concentration of pesticide to be tested. Under the optimum conditions, the competitive immunoassay exhibited a wide linear range of 0.01-20 ng/mL and a low detection limit of 0.002 ng/mL. Spike recovery tests were carried out using apple, rice, cabbage, and cucumber samples to verify the feasibility of the method. The recovery and relative standard deviations (RSDs) of the technique ranged from 76.9 to 94.4% and from 10.8 to 19.9%, respectively. To further validate the results, a linear correlation analysis was performed between the proposed method and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Consequently, the bio-barcode immunoassay based on nanoparticles and ddPCR, an ultrasensitive method, showed great potential for the determination of target pesticides in real samples.

A sensitive fluorescence assay of organophosphorus pesticides using acetylcholinesterase and copper-catalyzed click chemistry

Organophosphorus pesticides (OPs) are widely used in agricultural fields, but exhibit high toxicity to human beings. A sensitive fluorescence assay for organophosphorus pesticides was developed using the inhibition of acetylcholinesterase (AChE) activity and the copper-catalyzed click chemical reaction. In the click reaction, two hybridized DNA probes can be ligated with copper ions, inducing a fluorescence quenching during the strand displacement reaction. AChE can hydrolyze acetylthiocholine (ATCh) to form thiocholine (TCh) which contains a thiol group. TCh will react with copper ions, blocking the click reaction and a high fluorescence signal is observed. But in the presence of OPs, the activity of AChE is inhibited, releasing a high concentration of copper ions that catalyze the click chemical reaction and resulting in decreased fluorescence signals. Taking advantage of the copper-mediated signal amplification effect, the sensitivity was improved. This assay has also been applied to detect OPs in river water samples with satisfactory results, which demonstrates that the method has great potential for practical applications in environmental protection and food safety fields.

Silver-based surface enhanced Raman spectroscopy devices for detection of organophosphorus pesticides traces

The detection of traces of substances by surface-sensitive techniques such as surface enhanced Raman spectroscopy (SERS) explores the interaction of adsorbed molecules on plasmonic surfaces to improve the limit of detection of analytes. This article is an overview about recent development in SERS substrates applied in the detection of organophosphorus pesticides on plasmonic surfaces (arrays of metal nanoparticles). The morphology, roughness, chemical functionalization degree, and aggregation level of plasmonic centers are some of the critical parameters to be controlled in the optimization of SERS signal from specific analytes.

Homogeneous electrochemical aptasensor based on a dual amplification strategy for sensitive detection of profenofos residues

A homogeneous type of electrochemical aptasensor was designed based upon the principle of target-induced and tool enzyme-assisted signal amplification, which was employed for the detection of profenofos residues.

Supramolecular inter-ionic charge-transfer complexes between derivatives of pyridinium-4-oxime cations and hexacyanoferrate(ii) anions

Mono- and bis-pyridinium-4-oxime compounds are introduced as new electron acceptors for the formation of colored, supramolecular, inter-ionic charge-transfer complexes with hexacyanoferrate(ii) as a donor.