Selected pesticidal POPs and metabolites in the soil of five Vietnamese cities: Sources, fate, and health risk implications.

Large quantities of organochlorine pesticides (OCPs) have been used in tropical regions. The fate processes and risks of these legacy contaminants in the tropics are poorly understood. Herein, we investigated the occurrence of three classes of widely used OCPs and their metabolites in surface and core soil from five cities across Vietnam with a prevalent tropical monsoon climate and a long history of OCP application. We aimed to elucidate migration potentials, degradation conditions, and transformation pathways and assess current health risks of these contaminants. Generally, the concentrations of OCPs and metabolites in the soil core were slightly lower than those in surface soil except for hexachlorocyclohexane (HCH) isomers. 2,2-bis(4-chlorophenyl)-1,1,1-trichloroethane (p,p'-DDT), 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), the sum of dicofol and 4,4'-dichlorobenzophenone (p,p'-DBP), and 2,2-bis(4-chlorophenyl)-1,1-dichloroethane (p,p'-DDD) were the most abundant compounds in both surface and core soils. A uniform distribution of HCHs (the sum of α-, ß-, γ-, and δ-HCH) at trace levels was found in almost all soils, serving as evidence of the lack of recent use of HCH pesticides. Higher concentrations of DDTs (the sum of DDT, DDD, and DDE) were observed in north-central Vietnamese soil, whereas appreciable concentrations of ENDs (the sum of α- and ß-endosulfan and endosulfan sulfate) were only found in southern Vietnamese soils. Empirical diagnostic ratios indicated residuals of DDTs were mainly from technical DDT rather than dicofol, whereas aged HCHs could be explained by the mixture of lindane and technical HCH. Both historical applications and recent input explain DDTs and ENDs in Vietnamese soil. Total organic carbon performs well in preventing vertical migration of more hydrophobic DDTs and ENDs. The dominant transformation pathway of DDT in surface soil followed p,p'-DDE→2,2-bis(4-chlorophenyl)-1-chloroethylene or p,p'-DDMU→1,1-bis(4-chlorophenyl)ethylene or p,p'-DDNU→p,p'-DBP, whereas the amount of p,p'-DDMU converted from p,p'-DDD and p,p'-DDE is similar in soil core. Non-cancer risks of OCPs and metabolites in all soils and cancer risks of those chemicals in core soils were below the safety threshold, whereas a small proportion of surface soil exhibited potential cancer risk after considering the exposure pathway of vegetable intake. This study implied that organic matter in non-rainforest tropical deep soils still could hinder the leaching of hydrophobic organic contaminants as in subtropical and temperate soils. When lands with a history of OCP application are used for agricultural purposes, dietary-related risks need to be carefully assessed.

A glutamate-gated chloride channel as the mite-specific target-site of dicofol and other diphenylcarbinol acaricides.

Dicofol has been widely used to control phytophagous mites. Although dicofol is chemically related to DDT, its mode of action has remained elusive. Here, we mapped dicofol resistance in the spider mite Tetranychus urticae to two genomic regions. Each region harbored a glutamate-gated chloride channel (GluCl) gene that contained a mutation-G314D or G326E-known to confer resistance against the unrelated acaricide abamectin. Using electrophysiology assays we showed that dicofol and other diphenylcarbinol acaricides-bromopropylate and chlorobenzilate-induce persistent currents in Xenopus oocytes expressing wild-type T. urticae GluCl3 receptors and potentiate glutamate responses. In contrast, the G326E substitution abolished the agonistic activity of all three compounds. Assays with the wild-type Drosophila GluClα revealed that this receptor was unresponsive to dicofol. Homology modeling combined with ligand-docking confirmed the specificity of electrophysiology assays. Altogether, this work elucidates the mode of action of diphenylcarbinols as mite-specific agonists of GluCl.

Water quality, human health risk, and pesticides accumulation in African catfish and Nile tilapia from the Kitchener Drain-Egypt.

Pesticides are toxic and could negatively impact humans and the ecosystem. The Kitchener Drain is among the longest drains in Egypt and carries a wide range of wastewater from the agriculture sector, which contains pesticides and may pollute the ecosystem. Thus, water quality, human health risk, and pesticide accumulation in African catfish and Nile tilapia from the Kitchener Drain-Egypt. The water and fish samples were collected from Kitchener Drain in Kafr Elsheikh Governorate, Egypt, during the four seasons. The results indicated that heptachlor and diazinon were undetected during the four seasons. However, endosulfan, chlorpyrifos, and dicofol were detected in winter and autumn. Only p,p'-DDT was detected during spring. Endosulfan, heptachlor, and aldrin were detected in Nile tilapia during winter. Only heptachlor and aldrin were detected during spring. Endosulfan, heptachlor, dicofol, p,p'-DDT, chlorpyrifos, and diazinon were detected in the autumn season. In summer, dicofol and p,p'-DDT were detected, while endosulfan, heptachlor p,p'-DDT, aldrin, chlorpyrifos, and diazinon were not detected. In African catfish, endosulfan, heptachlor, dicofol, and p,p'-DDT were detected during winter, while chlorpyrifos, aldrin, and chlorpyrifos, aldrin, and diazinon were not detected. In the spring season, endosulfan, heptachlor, and aldrin were detected. Endosulfan, heptachlor, dicofol, p,p'-DDT, aldrin, chlorpyrifos, and diazinon were detected in the autumn season. Similarly, in the summer season, endosulfan, heptachlor, dicofol, p,p'-DDT, aldrin, chlorpyrifos, and diazinon were detected. The sequence of estimated daily intake (EDI) in Nile tilapia during the four seasons is heptachlor > endosulfan > dicofol > p,p'-DDT > aldrin > diazinon > chlorpyrifos. The sequence of EDI in African catfish during the four seasons is endosulfan > p,p'-DDT > heptachlor > aldrin > dicofol > diazinon > chlorpyrifos. In conclusion, the results confirmed the absence of a hazard index for consuming Nile tilapia and African catfish collected from the Kitchener drain.

Multiomics analyses reveal dose-dependent effects of dicofol exposure on host metabolic homeostasis and the gut microbiota in mice.

BACKGROUND: Environmental exposure to dicofol (DCF), one of common organochlorine pesticides (OCPs) widely used for controlling agricultural pests, elicits a potential risk for human health due to its toxicity. However, potential physiological hazards of oral DCF exposure remain largely unknown. METHODS: Mice were exposed to relatively chronic and subacute DCF at different doses (5, 20 and 100 mg/kg) by gavage for 2 weeks. 1H NMR-based metabolomics was used to explore alterations of metabolic profiling induced by DCF exposure. Targeted metabolomics was subsequently employed to investigate the dose-dependent effects of oral DCF exposure on lipid metabolism and the gut microbiota-derived metabolites of mice. 16S rRNA gene sequencing was further employed to evaluate the changes of gut community of mice exposed to DCF. RESULTS: Oral exposure to DCF dose-dependently induced liver injury, manifested by hepatic lipogenesis, inflammation and liver dysfunction of mice. Typically, DCF exposure disrupted host fatty acids metabolism that were confirmed by marked alteration in the levels of related genes. DCF exposure also dose-dependently caused dysbiosis of the gut bacteria and its metabolites including altered microbial composition accompanied by inhibition of bacterial fermentation. CONCLUSION: These results provide metabolic evidence that DCF exposure dose-dependently induces liver lipidosis and disruption of the gut microbiota in mice, which enrich our views of molecular mechanism of DCF hepatoxicity.

Determination of Dicofol in Tea Using Surface-Enhanced Raman Spectroscopy Coupled Chemometrics.

Dicofol is a highly toxic residual pesticide in tea, which seriously endangers human health. A method for detecting dicofol in tea by combining stoichiometry with surface-enhanced Raman spectroscopy (SERS) technology was proposed in this study. AuNPs were prepared, and silver shells were grown on the surface of AuNPs to obtain core-shell Au@AgNPs. Then, the core-shell Au@AgNPs were attached to the surface of a PDMS membrane by physical deposition to obtain a Au@AgNPs/PDMS substrate. The limit of detection (LOD) of this substrate for 4-ATP is as low as 0.28 × 10-11 mol/L, and the LOD of dicofol in tea is 0.32 ng/kg, showing high sensitivity. By comparing the modeling effects of preprocessing and variable selection algorithms, it is concluded that the modeling effect of Savitzky-Golay combined with competitive adaptive reweighted sampling-partial least squares regression is the best (Rp = 0.9964, RPD = 10.6145). SERS technology combined with stoichiometry is expected to rapidly detect dicofol in tea without labels.

Removal of pesticides from secondary treated urban wastewater by reverse osmosis.

The residues of pesticides that reach water resources from agricultural activities in several ways contaminate drinking water resources and threaten aquatic life. This study aimed to investigate the performance of three reverse osmosis (RO) membranes (BW30-LE, SW30-XLE, and GE-AD) in rejecting four different pesticides (tributyl phosphate, flutriafol, dicofol, and irgarol) from secondary treated urban wastewater and also to elucidate the mechanisms underlying the rejection of these pesticides. RO experiments were conducted using pesticide-spiked wastewater samples under 10 and 20 bar transmembrane pressures (TMP) and membrane performances were evaluated. Overall, all the membranes tested exhibited over 95% rejection performances for all pesticides at both TMPs. The highest rejections for tributyl phosphate (99.0%) and irgarol (98.3%) were obtained with the BW30-LE membrane, while for flutriafol (99.9%) and dicofol (99.1%) with the GE-AD membrane. The increase in TMP from 10 to 20 bar did not significantly affect the rejections of all pesticides. The rejection performances of RO membranes were found to be governed by projection area as well as molecular weight and hydrophobicity/hydrophilicity of pesticides. Among the membranes tested, the SW30-XLE membrane was the most prone to fouling due to the higher roughness.

Outdoor Atmospheric Micro-/Nanomineral-Mediated Organochlorine Pesticides in Sichuan Basin, China: Adsorption, Occurrence, and Risk Assessment.

Atmospheric micro-/nanominerals play an important role in the adsorption, enrichment, and migration of organochlorine pesticides (OCPs). In the present study, the correlations between OCPs and minerals in outdoor atmospheric dustfall were investigated, and the correlations were used to speculate the source of p,p'-(dicofol+dichlorobenzophenone [DBP]), which is the sum of p,p'-dicofol and p,p'-DBP. Atmospheric dustfall samples were collected from 53 sites in the Chengdu-Deyang-Mianyang economic region in the Sichuan basin. In this region, 24 OCPs were analyzed by gas chromatography-tandem mass spectrometry. The average concentration of 24 OCPs was 51.2 ± 27.4 ng/g. The results showed that the concentration of Σ24 OCPs in urban areas was higher than that in suburban areas (p < 0.05). Minerals in atmospheric dustfall were semiquantitatively analyzed by X-ray diffraction. The primary minerals were quartz, calcite, and gypsum. A Spearman correlation analysis of OCPs and minerals showed that low-volatility OCPs could be adsorbed by minerals in atmospheric dustfall. A density functional theory simulation verified that p,p'-(dicofol+DBP) in atmospheric dustfall was primarily derived from the p,p'-dicofol adsorbed by gypsum. Isomeric ratio results suggested that the samples had weathered lindane and chlordane profiles and confirmed that residents in the Sichuan basin used technical dichlorodiphenyltrichloroethane. Finally, the OCPs were evaluated to determine the potential risk of cancer in adults and children from OCP exposure. Exposure to OCPs via atmospheric dustfall was safe for adults. The cancer risk for children exposed to OCPs was slightly lower than the threshold value (10-6 ) under a high dust ingestion rate, which poses a concern. Environ Toxicol Chem 2023;42:594-604. © 2022 SETAC.

Profiles and determinants of dicofol, endosulfans, mirex, and toxaphenes in breast milk samples from 10 prefectures in Japan.

Human exposure to persistent organic pollutants (POPs) is reflected by POP concentrations in breast milk. Many studies of POPs in breast milk have been performed in Japan, but insufficient information is available about some legacy POPs (e.g., mirex and toxaphenes, included in the Stockholm Convention in 2001) and novel POPs (e.g., dicofol and endosulfans, included in the Stockholm Convention in 2019 and 2011, respectively). In this study, dicofol, endosulfan, mirex, and toxaphene concentrations in breast milk from 10 prefectures in Japan were determined. The samples were collected between 2005 and 2010, before Stockholm Convention restrictions on endosulfans and mirex were implemented. Common POPs (e.g., polychlorinated biphenyls) were also analyzed to allow the contamination statuses to be compared. The α-endosulfan and ß-endosulfan concentrations were 0.26-13 and 0.012-0.82 ng/g lipid, respectively. The toxaphene #26 and #50 concentrations were <0.08-5.6 and < 0.1-8.5 ng/g lipid, respectively. The dicofol concentrations were <0.01-4.8 ng/g lipid. The mirex concentrations were <0.2-3.5 ng/g lipid. The α- and ß-endosulfan concentrations on a lipid weight basis negatively correlated with the lipid contents of the milk samples (ρ = -0.65, p < 0.01 for α-endosulfan; ρ = -0.58, p < 0.01 for ß-endosulfan). The toxaphene concentrations positively correlated with the lipid contents. The mirex concentrations positively correlated with the maternal age but negatively correlated with the maternal body mass index. No correlations between the dicofol concentrations and the factors were found. Principal component analysis divided the data into four groups, (1) chlordanes, dichlorodiphenyltrichloroethanes and related compounds, hexachlorobenzene, hexachlorocyclohexanes, hexachloroethane, and polychlorinated biphenyls, (2) endosulfans, (3) dicofol, dieldrin, and toxaphenes, and (4) bromodiphenyl ether 47. This indicated that bromodiphenyl ether 47, dicofol, endosulfans, and toxaphenes have different exposure routes or different kinetics to the other legacy POPs.

Characteristics and Residual Health Risk of Organochlorine Pesticides in Fresh Vegetables in the Suburb of Changchun, Northeast China.

In this study, eleven organochlorine pesticides (OCPs) in fresh vegetables in the Changchun suburb were investigated, and their potential health risks were evaluated. The average concentrations of OCPs in edible parts of vegetables were found in the following descending order: Σhexachlorocyclohexanes (ΣHCHs) (6.60 µg·kg-1) > Σdichlorodiphenyltrichloroethanes (ΣDDTs) (5.82 µg·kg-1) > ΣChlordanes (2.37 µg·kg-1) > heptachlor (0.29 µg·kg-1). Moreover, OCPs in different types of vegetables exceeded the maximum residue limits (MRLs), and the exceeding rates in various vegetables decreased in the following order: leafy vegetables (19.12%) > root vegetables (18.75%) > fruit vegetables (3.85%). The proportions of OCPs exceeding MRL in different vegetables were found in the following descending order: Welsh onion (22.50%) > radish (18.75%) > Chinese cabbage (14.29%) > pepper (6.90%) > cucumber (3.23%) > eggplant (2.94%) > tomato (2.78%). The sources' identification results showed that DDTs in vegetables came mainly from newly imported technical DDTs and dicofol, while HCHs originated mainly from lindane. For both adults and children, the average target hazard quotients (avg. THQ) were all less than 1, and the average hazard index (avg. HI) values were 0.043 and 0.036, respectively. There were no significant health risks associated with OCP exposure for the inhabitants of the study area.

Application of the QuEChERS method for the determination of pesticides, PAHs and PCBs in fish in Senegal.

Pollution of water by persistent organic pollutants is well described; however, little is known about the accumulation of these pollutants by aquatic organisms. For this reason, a method based on QuEChERS extraction and gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) was developed for the determination of pesticides, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in the muscles of five fish species from the bay of Soumbedioune (Dakar, Senegal). This method shows good recoveries of extraction (68.2-98.1% for pesticides, 83.87-98.10% for PAHs and 81.30-98.15% for PCBs), precision (% RSD ≤ 1%), sensitivity (LODs between 0.001 and 0.079 ng g-1), linearity (R2 ≥ 0.99) and repeatability and reproducibility, evaluated for three concentration levels (10 ng g-1, 200 ng g-1 and 500 ng g-1), ≤ 15% for the majority of pollutants under study except for alachlor, atrazine, acetochlor, dicofol, deltamethrin and dichlorvos where a RSD ≥ 20% was determined for the 10 ng g-1 concentration. Organic pollutants have been detected in fish from the Soumbedioune coast demonstrating the necessity of a regular survey of water and fish in order to protect the populations.

A novel FRET immunosensor for rapid and sensitive detection of dicofol based on bimetallic nanoclusters.

To minimize the need of complex testing procedures, accurate, rapid and selective on-site determination of dicofol (DICO) is of vital importance. Herein, fluorescence immunosensing platforms based on the Förster resonance energy transfer (FRET) between Au-Ag bimetallic nanoclusters (Au-Ag NCs) and Au nanoflowers (Au NFs) were developed for the rapid detection of DICO in both liquid system and paper-based analytical devices (PADs). Conjugations of Au-Ag NCs and antigen (NCs-Agen) and Au-Ag NCs were regarded as energy donors in liquid system and PADs, respectively, while conjugations of Au NFs and antibody (NFs-Ab) were synthesized as energy acceptors. The overlapping spectrum and decrease of fluorescence lifetime of NCs-Agen proved that the fluorescence quenching mechanism was FRET effect. When DICO was captured by NFs-Ab, FRET effect was inhibited due to the long distance between NFs-Ab and NCs/NCs-Agen. Under optimal conditions, the FRET-based fluorescent immunosensors allowed for a rapid response toward DICO with considerable sensitivities of 0.185 ng/mL and 0.170 ng/mL in liquid system and PADs, respectively. Excellent specificity and satisfactory recovery in three kinds of tea samples were confirmed as well. This study opens an avenue for on-site, portable and sensitive detection methods.

Evidence of stockpile contamination for legacy polychlorinated biphenyls and organochlorine pesticides in the urban environment of Cyprus (Eastern Mediterranean): Influence of meteorology on air level variability and gas/particle partitioning based on equilibrium and steady-state models.

The present study investigated comprehensively the atmospheric occurrence and fate of an extensive range of polychlorinated biphenyls (PCBs; forty-two congeners), organochlorine pesticides (OCPs; twenty-seven emerging and legacy agrochemicals) and polycyclic aromatic hydrocarbons (PAHs; fifty parent and alkylated members, including the non USEPA-16 listed toxic ones), in both gas and particulate phase of the scarcely monitored atmosphere over Cyprus for the first time. Parent-metabolite concentration ratios suggested fresh application for dichlorodiphenyl-trichloroethanes (DDTs), dicofol, hexachlorocyclohexanes, endosulfan and chlorothalonil, particularly during spring (April-May). Regressions of logarithms of partial pressure against ambient temperature revealed that secondary recycling from contaminated terrestrial surfaces regulates the atmospheric level variability of PCBs, DDTs, aldrin, chlordane, dicofol, heptachlor and endosulfan. Enthalpies of surface-air exchange (∆HSA) calculated from Clausius-Clapeyron equations were significantly correlated to vaporization enthalpies (∆HV) determined by chromatographic techniques, corroborating presence of potential stockpile-contaminated sites around the study area. The Harner-Bidleman equilibrium model simulating urban areas, and the Li-Jia empirical model, predicted better the partitioning behavior of PAHs (

Immunological quantitative detection of dicofol in medicinal materials.

In this study, a highly specific and sensitive monoclonal antibody against dicofol (DIC) was prepared and used to create a colloidal gold immunochromatographic strip (ICS) for the quantitative analysis of DIC in liquorice and Angelica sinensis samples. We found that for both the liquorice and Angelica sinensis samples, the cut-off value for the ICS was 500 ng g-1, respectively, and using a colloidal gold test strip reader, the half-maximal inhibitory concentrations (IC50) were found to be 35 ng g-1 and 88 ng g-1, the limits of detection were 2 ng g-1 and 3 ng g-1, and the linear detection scopes (IC20-IC80) were from 6 to 201 ng g-1 and from 10 to 819 ng g-1, respectively. In the recovery test, we found that recoveries were within the range of 90.6% to 97.2% and the coefficients of variation were less than 8.6% in the intra-assay and inter-assay for the liquorice samples and the recoveries ranged from 90.8% to 97.3% and the coefficients of variation were less than 9.1% in the intra-assay and inter-assay for the Angelica sinensis samples. The established ICS assay could be used for the rapid quantitative screening of chemicals in Chinese traditional medicinal materials.

Differential Bioaccumulation Patterns of α, ß-Hexachlorobenzene and Dicofol in Adipose Tissue from the GraMo Cohort (Southern Spain).

To identify bioaccumulation patterns of α-, ß- hexachlorocyclohexane (HCH) and dicofol in relation to sociodemographic, dietary, and lifestyle factors, adipose tissue samples of 387 subjects from GraMo cohort in Southern Spain were analyzed. Potential predictors of these organochlorine pesticides (OCP) levels were collected by face-to-face interviews and assessed by multivariable linear and logistic regression. OCPs were detected in 84.2% (ß-HCH), 21.7% (α-HCH), and 19.6% (dicofol) of the population. ß-HCH levels were positively related to age, body mass index (BMI), mother's occupation in agriculture during pregnancy, living in Poniente and Alpujarras, white fish, milk and water consumption, and negatively related to being male, living near to an agricultural area, working ≥10 years in agriculture, and beer consumption. Detectable α-HCH levels were positively related to age, BMI, milk consumption, mother's occupation in agriculture during pregnancy, and negatively with residence in Poniente and Alpujarras, Granada city, and Granada Metropolitan Area. Residence near to an agricultural area, smoking habit, white fish and water consumption, and living in Poniente and Alpujarras, Granada city and Granada Metropolitan Area were negatively associated with detectable dicofol levels. Our study revealed different bioaccumulation patterns of α, ß-HCH and dicofol, probably due to their dissimilar period of use, and emphasize the need for assessing the exposure to frequently overlooked pollutants.

How can environmental conditions influence dicofol genotoxicity on the edible Asiatic clam, Meretrix meretrix?

Genotoxic effects of dicofol on the edible clam Meretrix meretrix were investigated through a mesocosm experiment. Individuals of M. meretrix, were exposed to environmental concentration (D1 = 50 ng/L) and supra-environmental concentration (D2 = 500 ng/L) of dicofol for 15 days, followed by the same depuration period. DNA damage (i.e., strand breaks and alkali-labile sites) was evaluated at day 1, 7 and 15, during uptake and depuration, using Comet assay (alkaline version) and nuclear abnormalities (NAs) as genotoxicity biomarkers. The protective effects of dicofol against DNA damage induced by ex vivo hydrogen peroxide (H2O2) exposure were also assessed. Comet assay results revealed no significant DNA damages under dicofol exposure, indicating 1) apparent lack of genotoxicity of dicofol to the tested conditions and/or 2) resistance of the animals due to optimal adaptation to stress conditions. Moreover, ex vivo H2O2 exposure showed an increase in the DNA damage in all the treatments without significant differences between them. However, considering only the DNA damage induced by H2O2 during uptake phase, D1 animals had significantly lower DNA damage than those from other treatments, revealing higher protection against a second stressor. NAs data showed a decrease in the % of cells with polymorphic, kidney shape, notched or lobbed nucleus, along the experiment. The combination of these results supports the idea that the clams used in the experiment were probably collected from a stressful environment (in this case Pearl River Delta region) which could have triggered some degree of adaptation to those environmental conditions, explaining the lack of DNA damages and highlighting the importance of organisms' origin and the conditions that they were exposed during their lives.

The BODIPY-based chemosensor for the fluorometric determination of organochlorine pesticide dicofol.

Dicofol is an organochlorine pesticide, which is widely used in fruits, tea and other crops, and is moderately toxic to humans. Therefore, the monitoring of organochlorine pesticide-dicofol is critical for food safety. In this work, a fluorometric chemosensor based on mercaptoethanol and boron dipyrromethene (BODIPY) was first constructed to detect the dicofol. The chemosensor displayed turn-off fluorescence behavior upon dicofol with a detection limit of 200 ppb. The nucleophilicity of the glutathione and other biological thiols was studied to evaluate the reactivity of thiols with dicofol. In practical applications, an obvious color difference was observed on a paper based microfluidic device modified by phenyltriethoxysilane (PTES). We designed an integrated device for pretreatment and paper-based detection, and successfully used for the detection of dicofol in tea. The applicability was demonstrated by detection of dicofol in real tea samples with good recovery ranging from 86% to 109%. The apparatus was convenient and could be used for on-site evaluation of dicofol.

Spectroscopic and in silico insight into the interaction between dicofol and human serum albumin.

Dicofol, a broad-spectrum acaricide, has garnered considerable attention because of the potential harm to the environment and various organisms. Herein, this study applied spectroscopic and in silico methods to understand the interaction between human serum albumin (HSA) and dicofol. Fluorescence experiments demonstrated that dicofol formed a stable complex and the binding process occurred in Suldow's site I of HSA. Its binding constant was 2.26 × 105 M-1 at 298 K. Van der Waals forces and hydrogen bond were primarily facilitated the interaction between dicofol and HSA (ΔH < 0, ΔS < 0) according to thermodynamic experiments. Additionally, 3D fluorescence and circular dichroism (CD) spectra revealed a few conformational changes in HSA due to dicofol. Molecular docking analysis indicated that dicofol interacted with Ser192, Gln196, Leu481, Arg218, Leu238, and Phe211 via van der Waals forces and formed a hydrogen bond with His242. Molecular dynamics (MD) simulation showed that Lys195 and Arg218 residues contributed greater energy for forming the HSA-dicofol complex. MD simulation analysis also showed that dicofol can affect the HSA structure with a reduction in α-helix. This research is desired to facilitate a new perspective on the toxicity mechanism of dicofol in the human body.

Exploring the binding mechanism and adverse toxic effects of persistent organic pollutant (dicofol) to human serum albumin: A biophysical, biochemical and computational approach.

The organochlorine pesticide dicofol (DCF), a persistent organic pollutant, is used as acaricide worldwide. Considering its large consumption in the agriculture sector and potential toxic effects such as endocrine disruption, carcinogenicity, and environmental persistence are detrimental to human health. To take an extensive evaluation of its potential toxicity, the current study was aimed to explore the binding mechanism and adverse effect of DCF on human serum albumin (HSA) by using an array of biophysical techniques (UV-visible, fluorescence, 3D fluorescence, and circular dichroism spectroscopy), isothermal titration calorimetric (ITC), computational methods and biochemical approaches. Fluorescence quenching and UV-Visible spectra of the HSA-DCF system confirmed static quenching mechanism and complex formation between HSA and DCF. The thermodynamics results from ITC revealed DCF-HSA interaction was exothermic and spontaneous and involved hydrophobic interactions and hydrogen bonding. The esterase activity of HSA displayed constant Vmax and elevated Km values confirming DCF-HSA competitive interaction. Circular dichroism spectra results revealed structural changes in HSA protein on interaction with DCF. Furthermore, molecular-specific site marker and molecular modelling results affirmed that the binding Site of DCF is Site I of HSA. A significant carbonyl content level in DCF-HSA system suggested protein structure damage. This work is likely to add a better understanding of DCF toxicity in human health and helpful in fortifying the check on food safety.

Immunoassay based on Au-Ag bimetallic nanoclusters for colorimetric/fluorescent double biosensing of dicofol.

The high toxicity of dicofol (DICO) to nontarget organisms has resulted in the contamination of food materials and caused a threat to human health. Developing a rapid and sensitive detection method of DICO in food samples is essential and still pursued. Fluorescent nanomaterials have been widely applied in biosensors to improve the sensitivity of detection. Herein, glutathione-capped Au-Ag bimetallic nanoclusters (Au-Ag NCs) exhibited the outstanding fluorescence characteristic with the average fluorescence lifetime of 1971.08 ns and photoluminescence quantum yield of 9.84% when the molar ratio of Au to Ag was 5:1. Polyethyleneimine modified gold nanoparticles (PEI-Au NPs) with the positive charge were prepared to generate a strong colorimetric signal. A dual-model colorimetric/fluorescent immune probe based on the Au-Ag NCs and PEI-Au NPs was successfully constructed by electrostatic force, and could be applied in both ic-ELISA and LFIA methods for rapid and ultrasensitive detection of DICO. In the ic-ELISA method, the introduction of fluorescence signal significantly increased the sensitivity of detection with the limit of detection (LOD) of 0.62 ng/mL and exhibited an excellent linear relationship within the range of 1.36 ng/mL-19.92 ng/mL. In the LFIA method, the fluorescence signal of Au-Ag NCs was accumulated on the test line and control line for the fluorescence model detection with a quantitative LOD at the level of 1.59 ng/mL. Such a dual-model colorimetric/fluorescent immunoassay serves as a promising candidate to develop new approaches in field detection.

Development of immunochromatographic strips for the detection of dicofol.

In this study, a monoclonal antibody (mAb) against dicofol was developed to prepare immunochromatographic strips (ICAs) for the detection of dicofol residues in fruit and vegetables. The mAb exhibited high affinity and high sensitivity, with an affinity constant of 2.96 × 1010 and a limit of detection of 3.142 ng mL-1. A cross reactivity test revealed that the mAb also had good specificity for dicofol. This ICA method gave a visible limit of detection of 50 ng g-1, and a cut-off value of 500 ng g-1 for the detection of dicofol in both apple and cucumber with the naked eye. Importantly, the results here are consistent with results obtained using liquid chromatography mass spectrometry and ic-ELISAs indicating that this ICA method is reliable and practical when used for the detection of dicofol in fruit and vegetables.