Bioactive Paper Sensor Based on the Acetylcholinesterase for the Rapid Detection of Organophosphate and Carbamate Pesticides

In many countries, people are becoming more concerned about pesticide residues which are present in or on food and feed products. For this reason, several methods have been developed to monitor the pesticide residue levels in food samples. In this study, a bioactive paper-based sensor was developed for detection of acetylcholinesterase (AChE) inhibitors including organophosphate and carbamate pesticides. Based on the Ellman colorimetric assay, the assay strip is composed of a paper support (1×10 cm), onto which a biopolymer chitosan gel immobilized in crosslinking by glutaraldehyde with AChE and 5,5′-dithiobis(2-nitrobenzoic) acid (DTNB) and uses acetylthiocholine iodide (ATChI) as an outside reagent. The assay protocol involves introducing the sample to sensing zone via dipping of a pesticide-containing solution. Following an incubation period, the paper is placed into ATChI solution to initiate enzyme catalyzed hydrolysis of the substrate, causing a yellow color change. The absence or decrease of the yellow color indicates the levels of the AChE inhibitors. The biosensor is able to detect organophosphate and carbamate pesticides with good detection limits (methomyl=6.16×10-4 mM and profenofos=0.27 mM) and rapid response times (~5 min). The results show that the paper-based biosensor is rapid, sensitive, inexpensive, portable, disposable, and easy-to-use

Preparation and Characterizations of Chitosan/Citral Nanoemulsions and their Antimicrobial Activity

Background and Objective: The antimicrobial activity of essential oils has been long recognized, however, they easily evaporate and/or decompose during preparation, owing to direct exposure to heat, pressure and light. The current study deals with the formulation and characterization of bio-based oil in water nanoemulsions and their antimicrobial activity against plant pathogens.Material and Methods: Citral oil and low molecular weight chitosan were used for preparation of nanoemulsions in the presence of sodium tripolyphosphate. Nanoemulsions were prepared by adding dropwise citral at different ratios into an aqueous solution containing chitosan, sodium tripolyphosphate and surfactant with continuous stirring and then ultrasonication. The success of formulation was confirmed by dynamic light scattering and scanning electron microscopy techniques. Physical stability and viscosity were investigated in details. The antimicrobial activity was evaluated against Erwinia carotovora, Aspergillus niger and Rhizopus stolonifer. Results and Conclusion: The nanoemulsions had a polydispersity index ranged from 0.508 to 0.614 and particle size from 27 to 1283 nm. The highest antimicrobial activity was observed with F1 formulation (EC50 = 23, 278 and 221 mg L-1, against Erwinia carotovora, Aspergillus niger and Rhizopus stolonifer, respectively). Based on the antimicrobial activity, the prepared chitosan/citral nanoemulsions can be a cost-effective way to protect crops from microbial pathogens. Because such formulations contain bioactive products, the development of resistant pathogens can be delayed.Conflict of Interest: The authors declare no conflict of interest.

Impact of organic amendments addition to sandy clay loam soil and sandy loam soil on leaching process of chlorantraniliprole insecticide and bispyribac-sodium herbicide

The leaching of two pesticides, cholantraniliprole (CAP) and bispyribac-sodium (BPS) in sandy clay loam soil (soil A) and sandy loam soil (soil B) were examined, by soil columns under laboratory conditions. In addition, the effect of adding 5% biochar and wheat straw to the soils on the leaching of CAP and BPS was studied. It is clear from the results that BPS is more leachable than CAP in all soil columns, and more leached to soil B. It was found that the addition of biochar and wheat straw has a significant effect on the movements of these pesticides and can be used to reduce the environmental impact. For CAP, 71 to 97% and 84 to 97% were recovered from the soil A columns and soil B columns, respectively, while for BPS, 94 to 99% were recovered from columns of soil A and soil B

Experimental modeling design to study the effect of different soil treatments on the dissipation of metribuzin herbicide with effect on dehydrogenase activity

The dissipation and side-effect of metribuzin (MBZ) were studied with various factors; two soil types (clay loam and sandy loam), soil amendment (wheat straw and without amendment), two temperature levels (25 and 50°C), sterilization (sterilized and unsterilized soil) and time of incubation (15 and 30 days) and designed by Windows version of MINITAB software package to reduce the time and the cost as well as increased the precision. Determination of MBZ by HPLC with recoveries ranged from 50.85 to 108.09%. The MBZ residues were detected in all samples up to 60 days of storage, respectively with decline in their concentrations with the time of incubation. The clay loam soil showed higher dissipation than the sandy loam soil. The different factors in the present study confirmed that the wheat straw amendment, non-sterilization and incubation at 50°C caused higher dissipation of MBZ than without wheat straw, sterilization and incubation at 25°C. The dissipation was described mathematically by a first order equation with t0.5 was ranged from 9.62 to 16.82 days in clay loam soil and from 10.01 to 16.04 days in sandy loam soil. The side-effect of MBZ was tested on soil dehydrogenase activity that can be considered as an indicator of the biological activity and microbial degradation. The result proved that the enzyme activity was significantly decreased in all treatments compared with the controls at 1 and 3 days of incubation then it was gradually increased at 7, 10, 15 and 30 days of incubation. Treatments of wheat straw, non-sterilized and incubated at 25°C or 50°C showed the lowest enzyme inhibition among all treatments

Effect of soil organic amendments on sorption behavior of two insecticides and two herbicides

The effect of biochar, compost, peat and wheat straw at 1 and 5% on adsorption isotherm of chlorantraniliprole, dinotefuran, bispyribac-sodium, and metribuzin was studied in clay loam soil and sandy loam soil. Biochar, compost, peat and wheat straw (at a rate of 1 % in soil) improved the adsorption capacity of chlorantraniliprole and metribuzin in sandy loam soil. The sorption coefficients are higher for chlorantraniliprole and metribuzin whereas lower for dinotefuran and bispyribac-sodium in amended soil compared to unamended sandy loam soil. There is not a clear direct correlation between Freundlich parameters as well as Kd or Koc and type of organic amendment. The sorption of all tested pesticides on biochar was increased, whereas on compost was decreased. The order of pesticides sorption in soils and different organic amendments is generally inversely proportional to their aqueous solubilites. Adsorption of chlorantraniliprole increases on the sandy loam soil amendment at the rate of 1% in the following order: peat > compost > biochar > original soil. Also, the magnitude of adsorption on soil A amendment at the rate of 5% can be arranged for dinotefuran in the order; peat > biochar > compost > original soil and for bispyribac-sodium and metribuzin peat = wheat straw > biochar > original soil

Toxicity Assessment of Buprofezin, Lufenuron, and Triflumuron to the Earthworm Aporrectodea caliginosa

Earthworms are particularly important soil macroinvertebrates and are often used in assessing the general impact of pesticide pollution in soil. The present study was conducted in order to investigate the toxicity of three insect growth regulators (IGRs) buprofezin, lufenuron, and triflumuron, at different application rates and exposure times toward mature earthworms Aporrectodea caliginosa. The effects of these pesticides on the growth rate in relation to the activities of acetylcholinesterase (AChE) and glutathione S-transferase (GST) as biochemical indicators were evaluated to elucidate the mechanisms of action. Toxicity studies indicated that lufenuron was the most harmful pesticide to mature earthworms, followed in descending order by buprofezin and triflumuron. A reduction in growth rate in all pesticide-treated worms was dose-dependent over the 28-day exposure period, which was accompanied by a decrease in AChE and GST activities. Relationships between growth rate, AChE, and GST provided strong evidence for the involvement of pesticidal contamination in the biochemical changes in earthworms, which can be used as a bioindicator of soil contamination by pesticides

Preparation of Ecofriendly Formulations Containing Biologically Active Monoterpenes with Their Fumigant and Residual Toxicities against Adults of Culex pipiens

Different mixtures of monoterpenes (ketone, alcohol, and alkene) were loaded on paper discs and wax and their knockdown activities were evaluated against Culex pipiens adults. Some individual monoterpenes were also evaluated by residual toxicity technique. Citronella oil as a reference was also loaded separately or in combination with monoterpenes on paper discs and wax. The ketone monoterpenes mixture (camphor, menthone, carvone, and fenchone) on paper discs was the most active (KT50 = 17.20 min) followed by ketone monoterpenes with citronella oil (KT50 = 20.79 min) and citronella oil alone (KT50 = 28.72 min). Wax formulations proved that the ketone and alcohol (geraniol, thymol, and menthol) monoterpenes gave the most activity as knockdown (KT50 = 31.79 and 43.39 min, resp.). Alcohol monoterpenes formulation recorded KT50 = 43.39 min. Residual activity of tested individual monoterpenes reported that the menthol was more toxic than camphor and camphene. Generally, this study suggests that the monoterpenes have the properties, which make them used as eco-friendly compounds in the control programs of Cx. pipiens adult. The use of paper discs is more applicable than wax in the adulticidal formulations

The state of HRM in the Middle East:Challenges and future research agenda

Based on a robust structured literature analysis, this paper highlights the key developments in the field of human resource management (HRM) in the Middle East. Utilizing the institutional perspective, the analysis contributes to the literature on HRM in the Middle East by focusing on four key themes. First, it highlights the topical need to analyze the context-specific nature of HRM in the region. Second, via the adoption of a systematic review, it highlights state of development in HRM in the research analysis set-up. Third, the analysis also helps to reveal the challenges facing the HRM function in the Middle East. Fourth, it presents an agenda for future research in the form of research directions. While doing the above, it revisits the notions of “universalistic” and “best practice” HRM (convergence) versus “best-fit” or context distinctive (divergence) and also alternate models/diffusion of HRM (crossvergence) in the Middle Eastern context. The analysis, based on the framework of cross-national HRM comparisons, helps to make both theoretical and practical implications