A highly sensitive bio-barcode immunoassay for multi-residue detection of organophosphate pesticides based on fluorescence antiquenching

Balancing the risks and benefits of organophosphate pesticides(OPs)on human and environmental health relies partly on their accurate measurement.A highly sensitive fluorescence anti-quenching multi-residue bio-barcode immunoassay was developed to detect OPs(triazophos,parathion,and chlorpyrifos)in apples,turnips,cabbages,and rice.Gold nanoparticles were functionalized with monoclonal antibodies against the tested OPs.DNA oligonucleotides were complementarily hybridized with an RNA fluorescent label for signal amplification.The detection signals were generated by DNA-RNA hybridization and ribonuclease H dissociation of the fluorophore.The resulting fluorescence signal enables multiplexed quantification of triazophos,parathion,and chlorpyrifos residues over the concentration range of 0.01-25,0.01-50,and 0.1-50 ng/mL with limits of detection of 0.014,0.011,and 0.126 ng/mL,respectively.The mean recovery ranged between 80.3% and 110.8% with relative standard deviations of 7.3%-17.6%,which correlate well with results obtained by liquid chromatography-tandem mass spectrometry(LC-MS/MS).The proposed bio-barcode immunoassay is stable,reproducible and reliable,and is able to detect low residual levels of multi-residue OPs in agricultural products.

混配农药中毒防治研究

首次在我国开展大规模的混配农药中毒流行病学调查,发现接触混配农药是当前发生农药中毒的重要危险因素,为针对性的预防提供了科学依据。毒理学研究证实多数农药混剂呈增毒效应或协同作用,且与其毒代动力学变化有密切关系,为今后开发高效、低毒的混配农药提供了毒理学依据。在国内外首次建立甲基对硫磷单克隆抗体酶联免疫测定法,并成功研制便携式血胆碱酯酶快速测定仪;这些检测接触、效应生物标志物的灵敏、特异、便捷的方法已试用于现场,并具有开发为产品的前景。同时还发现对氧磷酶基因在192位点的单核苷酸多态性,可能是甲基对硫磷免疫毒性作用的易感性生物标志物之一。在总结不同类别农药混配后所致中毒的临床表现特点和规律的基础上,修订现行的农药中毒诊断标准,增添了有机磷单剂及混剂中毒所致“中间期肌无力综合征”的新内容,将提高我国农药中毒的诊治水平。本研究主要成果达国内领先和国际先进水平。

Isolation and characterization of a profenofos degrading bacterium

Profenofos, a well known organophosphate pesticide, has been in agricultural use over the last two decades for controlling Lepidopteron pests of cotton and tobacco crops. In this study, a bacterial strain, OW, was isolated from a long term profenofos exposed soil by an enrichment technique, and its ability to degrade profenofos was determined using gas chromatography. The isolated strain OW was identified as Pseudomonas aeruginosa according to its physiological and biochemical properties, and the analysis of its 16S rRNA gene sequence. The strain grew well at pH 5.5-7.2 with a broad temperature profile. Bioremediation of profenofos-contaminated soil was examined using soil treated with 200 μg/g profenofos, which resulted in a higher degradation rate than control soils without inoculation. In a mineral salt medium （FTW）, removal in the level of profenofos of 86.81% was obtained within 48 h of incubation. The intermediates of profenofos metabolism indicated that the degradation occurred through a hydrolysis mechanism, and one of the metabolites was found to be 4 bromo-2-cholorophenol （BCP） which in turn was also mineralized by the strain. The results of this study highlighted the potentiality of P. aeruginosa as a biodegrader which could be used for the bioremediation of profenofos contaminated soil.

Developmental Effects of Malathion Exposure on Recognition Memory and Spatial Learning in Males Wistar Rats

Most cognitive effects of Organophosphate Pesticides (OP) are induced after exposure to parathion, chlorpyrifos and diazinon, which the usage has been restricted because of overt signs of their toxicities. In this study, we investigate whether developmental exposure to Malathion could impair spatial learning and recognition memory in male rats. Animals exposed by intragastric route, from in utero to young adult stage, to incremental doses of Malathion dissolved in corn oil;100, 200 and 300 mg/kg of body weight, and one control group are given corn oil. Then, cognitive and behaveioral abilities are assessed using Barnes maze and object recognition memory task. Malathion administration at 300 mg/kg is toxic to pregnant dams, and pups are stillborns. Rats exposed to 200 mg/kg make a significant working memory error, and require more time to find an escape box during the initial training phase of Barnes maze. However, fewer errors are made in rats exposed to 100 mg/kg. For reversal learning task, the high dose group shows great deficits in spatial strategy to locate the new position of the box. With respect to recognition task, both dose 100 and 200 mg/kg impair significant short-term (2 h after habituation phase) object recognition memory, but long-term (24 h after habituation phase) recognition memory is intact in high dose group. The current study also reveals that all treatments induce high significant neocortex acetylcholinesterase (AChE) activity inhibition, but 100 mg/kg dose is not sufficient to disrupt great hippocampal activity alteration. These results suggest that developmental exposure to Malathion, despite low toxicity described, may induce late-emerging spatial learning and recognition memorialterations. Moreover, Cortical and hippocampal area that support strongly these behaviors remain sensitive to incremental doses of Malathion.

Cerium dioxide as a new reactive sorbent for fast degradation of parathion methyl and some other organophosphates

Cerium dioxide was used for the first time as reactive sorbent for the degradation of the organophosphate pesticides para-thion methyl, chlorpyrifos, dichlofenthion, fenchlorphos, and prothiofos, as well as of some chemical warfare agents-nerve gases soman and O-ethyl S-[2-（diisopropylamino） ethyl] methylphosphonothioate （VX）. CeO2 specimens were prepared by calcination of basic cerous carbonate obtained by precipitation from an aqueous solution. The CeO2 samples containing certain amounts （1 wt.%-5 wt.%） of the neighboring lanthanides （La, Pr, Nd） were prepared in a similar way from pure lanthanide salts. It was shown that ceria accelerated markedly the decomposition of parathion methyl causing the cleavage of the P-O-aryl bond in the pesticide molecule. A similar reaction mechanism was proposed for the degradation of other organophosphate pesticides and nerve agents. The degradation times （reaction half-times） were in an order of minutes in the presence of CeO2, compared to hours or days under common environ-mental conditions. The reaction in suitable organic solvents allowed conversions of about 90%for parathion methyl loading of 20 mg pesticide/g CeO2 within 2 h with a reactant half-life in the order of 0.1 min. The key parameter governing the degradation efficiency of CeO2 was the temperature during calcination. At optimum calcination temperature （about 773.15 K）, the produced ceria retained a sufficiently high surface area, and attained an optimum degree of crystallinity （related to a number of crystal defects, and thus poten-tial reactive sites）. The presence of other lanthanides somewhat decreased the reaction rate, but this effect was not detrimental and permitted the possible use of chemically impure ceria as a reactive sorbent. A fast organophosphate degradation was demonstrated not only in non-polar solvents （such as heptane）, but also in polar aprotic solvents （acetonitrile, acetone） that are miscible with water. This opens new possibilities for designing more versatile decontamination strategies. The cleavage of phosphate ester bonds is of a great importance not only for the degradation of dangerous chemicals （chemical weapons, pesticides）, but also for interactions of ceria （es-pecially the nano-sized one） in biologically relevant systems.

A Highly Efficient ZrO2 Nanoparticle Based Electrochemical Sensor for the Detection of Organophosphorus Pesticides

A sensitive electrochemical method for square-wave voltammetric detection of organophosphate （OP） com- pounds was developed based on zirconia （ZrO2） nanoparticles modified electrode. The electrode was fabricated us- ing electrochemical deposition and characterized by scanning electron microscopy （SEM）, which confirmed the successful formation of nanoparticles. Due to the strong affinity of ZrO2 with the phosphoric group, OPs can strongly bind to the surface of ZrO2 nanoparticles （ZrO2NPs）. Under optimized operational conditions, SWV was employed for Omethoate （a model of OP compounds） detection with 5 min absorption, which showed a wide detec- tion range from 98.5 pmoloL-x to 985 nmol·L^1, with a detection limit as low as 52.5 pmol·L^-1. This electrochemi- cal sensor has good selectivity, stability and reproducibility, and great potential in the detection of OP compounds in agriculture area.

Immobilization of an enzyme from a Fusarium fungus WZ-I for chlorpyrifos degradation

The free enzyme extracted from WZ-I, which was identified as Fusarium LK. ex Fx, could effectively degrade chlorpyrifos, an organophosphate insecticide. The methods of immobilizing this free enzyme and determined its degradation-related characteristics were investigated. The properties of the immobilized enzyme were compared with those of the free enzyme. The optimal immobilization of the enzyme was achieved in a solution of 30 g/L sodium alginate at 4℃ for 4-12 hr. The immobilized enzyme showed the maximal activity at pH 8.0, 45℃. The maximum initial rate and the substrate concentration of the immobilized enzyme were less than that of the free enzyme. The immobilized enzyme, therefore, had a higher capacity to withstand a broader range of temperatures and pH conditions than the free enzyme. With varying pH and temperatures, the immobilized enzyme was more active than the free enzyme in the degradation reaction. In addition, the immobilized enzyme exhibited only a slight loss in its initial activity, even after three repeated uses. The results showed that the immobilized enzyme was more resistant to different environmental conditions, suggesting that it was viable for future practical use.

A review on phorate persistence, toxicity and remediation by bacterial communities

Pesticides are an integral part in maintaining agriculture and horticultural productivity and play a vital role in meeting the increasing food, fiber, and fuel needs of the growing population. Globally, organophosphate pesticides(OPPs) are among the most common pesticides used due to their high proficiency and relatively low persistence in the environment. However, recent studies have reported problems due to pesticide use, e.g., phorate contamination of aquatic ecosystems(fresh and groundwater), sediments, fruits and vegetables, and forage crops. This review highlights many cases where phorate has been detected above its respective maximum residue limit values. Organophosphate pesticides, including phorate, have negative impacts on both the environment and human health. The ecological and public health concerns of recurrent pesticide utilization have encouraged the research related to environmental fate of pesticides.Bioremediation is an effective, eco-friendly, and financially viable approach for the decontamination and degradation of toxic OPPs from the environment,compared to the costly, unecological, and time-consuming physicochemical approaches, which lead to the generation of byproducts of higher toxicity.Researchers have recognized that a wide range of microbes, mainly bacteria, can degrade this extremely hazardous pesticide. Therefore, this review discusses the present pesticide scenarios, especially phorate contamination, its toxicity, biodegradation, and metabolic products via bacterial communities, both in India and globally. The latest and up-to-date literatures on the use, contamination, and bacterial application of phorate degradation are also summarized. This article offers national and international food safety organizations and public health authorities the ability to be involved in preventing the risks associated with the use of food and nutrition products contaminated with extremely toxic phorate pesticide. This article would also enable researchers to develop comprehensive and sustainable methods to effectively remediate pesticide-contaminated environments. In conclusion, it is envisaged that the successful application of bacterial communities for degradation of phorate would help in understanding the fate and persistence of such toxic pollutants in a better way.

Disruption of iron homeostasis and resultant health effects upon exposure to various environmental pollutants:A critical review

Environmental pollution has become one of the greatest problems in the world, and the concerns about environmental pollutants released by human activities from agriculture and industrial production have been continuously increasing. Although intense efforts have been made to understand the health effects of environmental pollutants, most studies have only focused on direct toxic effects and failed to simultaneously evaluate the long-term adaptive, compensatory and secondary impacts on health. Burgeoning evidence suggests that environmental pollutants may directly or indirectly give rise to disordered element homeostasis, such as for iron. It is crucially important to maintain concerted cellular and systemic iron metabolism. Otherwise, disordered iron metabolism would lead to cytotoxicity and increased risk for various diseases, including cancers. Thus, study on the effects of environmental pollutants upon iron homeostasis is urgently needed. In this review, we recapitulate the available findings on the direct or indirect impacts of environmental pollutants, including persistent organic pollutants（POPs）, heavy metals and pesticides, on iron homeostasis and associated adverse health problems. In view of the unanswered questions, more efforts are warranted to investigate the disruptive effects of environmental pollutants on iron homeostasis and consequent toxicities.