Analysis of phosphorothionate pesticides using a chloroperoxidase pretreatment and acetylcholinesterase biosensor detection

Insecticidal Effect of the Entomopathogenic Fungus Lecanicillium araneicola HK-1 in Aphis craccivora (Hemiptera: Aphididae)

Aphis craccivora (Hemiptera: Aphididae) is an important pest affecting various crops worldwide. However, only few studies have been conducted on the infection of A. craccivora by Lecanicillium and related insecticidal mechanisms. We investigated the infection process of A. craccivora by Lecanicillium araneicola HK-1 using fluorescence microscopy and scanning electron microscopy (SEM), and our results indicated that the conidia of strain HK-1 easily attached to the feet and dorsum of A. craccivora. The activities of chitinase and extracellular protease were induced in the aphid after treatment with HK-1. A bioassay on A. craccivora showed that the median lethal concentration (LC50) of the fungus crude extract was 24.00 mg mL-1 for 24 h of treatment. Additionally, the results showed that the crude extract disrupted the enzyme system of A. craccivora, inducing the inhibition of carboxylesterase (CarE) and the induction of glutathione S-transferase (GST) and acetylcholinesterase (AChE). Combining these results with those of a gas chromatography-mass spectrometry (GC-MS) analysis, it is suggested that p-cymene, hymecromone, 9,12-octadecadienoic acid (Z, Z) methyl ester, and 9,12-octadecadienoic acid (Z, Z) may be connected to the insecticidal effects we observed. This study provides a theoretical basis for the use of L. araneicola HK-1 as a potential biological control agent.

High-performance thin-layer chromatography in combination with an acetylcholinesterase-inhibition bioassay with pre-oxidation of organothiophosphates to determine neurotoxic effects in storm, waste, and surface water

Pesticides such as organothiophosphates (OTPs) are neurotoxically active and enter the aquatic environment. Bioassays, using acetylcholinesterase (AChE), a suitable substrate and reactant, can be applied for the photometric detection of AChE-inhibiton (AChE-I) effects. The oxidized forms of OTPs, so-called oxons, have higher inhibition potentials for AChE. Therefore, a higher sensitivity is achieved for application of oxidized samples to the AChE assay. In this study, the oxidation of malathion, parathion, and chlorpyrifos by n-bromosuccinimide (NBS) was investigated in an approach combining high-performance thin-layer chromatography (HPTLC) with an AChE-I assay. Two AChE application approaches, immersion and spraying, were compared regarding sensitivity, precision, and general feasibility of the OTP effect detection. The oxidation by NBS led to an activation of the OTPs and a strong increase in sensitivity similar to the oxons tested. The sensitivity and precision of the two application techniques were similar, although the spray method was slightly more sensitive to the oxidized OTPs. The 10% inhibition concentrations (IC10) for the spray approach were 0.26, 0.75, and 0.35 ng/spot for activated malathion, parathion, and chlorpyrifos, respectively. AChE-I effect recoveries in samples from a stormwater retention basin and receiving stream were between 69 and 92% for malathion, parathion, and chlorpyrifos. The overall workflow, including sample enrichment by solid-phase extraction, HPTLC, oxidation of OTPs, and AChE-I assay, was demonstrated to be suitable for the detection of AChE-I effects in native water samples. An effect of unknown origin was found in a sample from a stormwater retention basin.

Effects of the deglycosylation on the structure and activity of chloroperoxidase: Molecular dynamics simulation approach

Chloroperoxidase (CPO) is a versatile fungal heme-thiolate protein that catalyzes a variety of one electron and two-electron oxidations. Chloroperoxidase is a versatile fungal heme-thiolate protein that catalyzes a variety of oxidations. CPO enzyme contains thirteen sugars, including five N-acetyl D-glucosamines (NAG) and eight mannoses (MAN), which are attached to the protein via the glycosidic bonds. Removal of the sugars from CPO leads to increase the hydrophobicity of the enzyme, as well as the reduction of the alkylation reactions. However, due to the lack of the proper force field for the sugars, they are ignored in the theoretical studies. The present study aims to assess the effects of the sugar segments on the structure and activity of CPO through the simulation of the halo structure and the structures without the sugar segment. Despite the difficulty of the process and being time-consuming, the suitable force field is introduced successfully for the sugars. According to molecular dynamics simulation (MD), seven channels and fifteen cavities are identified in the CPO structure. Two of the channels provide the substrate access to the active site. The MD simulation results reveal that the removal of NAG decreases the number of the cavities from fifteen to eleven. Besides, the removal of NAG is associated with removing the channel providing the substrate access. The number of the cavities decreases from fifteen to fourteen through the removal of MAN; however, channel providing the substrate access to the active site is partly preserved. The MD simulation results indicate that the structures without the sugar units are more compact in comparison with the halo structures. The removal of the sugar segments induces the significant changes in the flexibility of the residues that affect the catalytic activity of the enzyme. As a result, the enzyme activities, such as the oxidation, alkylation, halogenation, and epoxidation cannot occur when the sugar segments of the enzyme are removed.

Progress in enzyme inhibition based detection of pesticides

The previous few decades have seen the development of biosensors and their use in monitoring of pesticides in food and environmental samples. Although inhibition-based biosensors have been subject of several recent research works, their performance characteristics greatly depend on the type of immobilization and the presence of interfering compounds in the samples. Moreover, sensitivity, detection limits, and rapidity of the response are few of the other major features that need to be investigated further if they are to become operationally user-friendly. This review will highlight research carried out in the past on biosensors that are based on enzyme inhibition for determination of organophosphorus compounds and carbamate pesticides.

Biosensor: an emerging safety tool for meat industry

The meat industry associated with the health hazards like deadly pathogens, veterinary drugs, pesticide residues, toxins and heavy metals is in need of a tool to tackle the awful situation and ensure safer product to consumer. The growth in the industry, global trade scenario, stringent laws and consumer awareness has placed an extra onus on the meat industry to meet out the expectations and demands. Biosensors are the latest tool of detection in the fast growing industries including the food industry. Hence an attempt is envisaged here to review the possibility of harnessing biosensors as tool of safety to safe guard the consumer health and address safety issues in reference to the common threats of concern in the meat industry.

Exonuclease I-aided homogeneous electrochemical strategy for organophosphorus pesticide detection based on enzyme inhibition integrated with a DNA conformational switch

A homogeneous electrochemical strategy for the detection of organophosphorus pesticides based on the inhibition of acetylcholinesterase activity and configuration change of hairpin DNA probes was developed.

Biosensors for the analysis of microbiological and chemical contaminants in food

Increases in food production and the ever-present threat of food contamination from microbiological and chemical sources have led the food industry and regulators to pursue rapid, inexpensive methods of analysis to safeguard the health and safety of the consumer. Although sophisticated techniques such as chromatography and spectrometry provide more accurate and conclusive results, screening tests allow a much higher throughput of samples at a lower cost and with less operator training, so larger numbers of samples can be analysed. Biosensors combine a biological recognition element (enzyme, antibody, receptor) with a transducer to produce a measurable signal proportional to the extent of interaction between the recognition element and the analyte. The different uses of the biosensing instrumentation available today are extremely varied, with food analysis as an emerging and growing application. The advantages offered by biosensors over other screening methods such as radioimmunoassay, enzyme-linked immunosorbent assay, fluorescence immunoassay and luminescence immunoassay, with respect to food analysis, include automation, improved reproducibility, speed of analysis and real-time analysis. This article will provide a brief footing in history before reviewing the latest developments in biosensor applications for analysis of food contaminants (January 2007 to December 2010), focusing on the detection of pathogens, toxins, pesticides and veterinary drug residues by biosensors, with emphasis on articles showing data in food matrices. The main areas of development common to these groups of contaminants include multiplexing, the ability to simultaneously analyse a sample for more than one contaminant and portability. Biosensors currently have an important role in food safety; further advances in the technology, reagents and sample handling will surely reinforce this position.