Ecotoxicological impact of dinotefuran insecticide and its metabolites on non-targets in agroecosystem: Harnessing nanotechnology- and bio-based management strategies to reduce its impact on non-target ecosystems.

The class of insecticides known as neonicotinoid insecticides has gained extensive application worldwide. Two characteristics of neonicotinoid pesticides are excellent insecticidal activity and a wide insecticidal spectrum for problematic insects. Neonicotinoid pesticides can also successfully manage pest insects that have developed resistance to other insecticide classes. Due to its powerful insecticidal properties and rapid plant absorption and translocation, dinotefuran, the most recent generation of neonicotinoid insecticides, has been widely used against biting and sucking insects. Dinotefuran has a wide range of potential applications and is often used globally. However, there is growing evidence that they negatively impact the biodiversity of organisms in agricultural settings as well as non-target organisms. The objective of this review is to present an updated summary of current understanding regarding the non-target effects of dinotefuran; we also enumerated nano- and bio-based mitigation and management strategies to reduce the impact of dinotefuran on non-target organisms and to pinpoint knowledge gaps. Finally, future study directions are suggested based on the limitations of the existing studies, with the goal of providing a scientific basis for risk assessment and the prudent use of these insecticides.

Occurrence and fate of five representative neonicotinoid insecticides across different wastewater treatment plants and the impact on receiving water bodies.

Neonicotinoids (NEOs), despite their widespread use as insecticides, exhibit a notable knowledge deficit in regards to their presence in wastewater treatment plants (WWTPs) and their surrounding environments. This study delves into the presence and disposition of 5 NEOs: Thiamethoxam (THM), Clothianidin (CLO), Imidacloprid (IMD), Acetamiprid (ACE), and Thiacloprid (THA) across 3 domestic WWTPs and their receiving waters. Notably, THM, CLO, and ACE were consistently detected in all water and sludge samples, with THM emerging as the most abundant compound in both influent and effluent. Among the 3 WWTPs, WWTP 2, employing a fine bubble oxidation process, achieved the highest removal efficiency, surpassing 68%, in contrast to WWTP 1 (CAST) at 37% and WWTP 3 (A/A/O) at 7%. Biodegradation played a pivotal role in NEO removal, accounting for 36.7% and 68.2% of the total removal in WWTP 1 and WWTP 2, respectively. Surprisingly, in WWTP 3, biotransformation process inadvertently increased ACE and CLO concentrations by approximately 4.1% and 4.5%, respectively. The total NEO concentration in the receiving surface waters ranged from 72.7 to 155.5 ng/L, while sediment concentrations were significantly lower, spanning between 0.10 and 1.53 ng/g. WWTPs serve as both a removal and concentration point for NEOs, thereby significantly influencing their transportation. Additionally, the concentration of most NEOs in the receiving waters progressively increased from upstream to downstream, highlighting the substantial impact of WWTP discharges on natural water environments. This research offers valuable insights into NEO pollution surrounding WWTPs in the Pearl River Delta, ultimately aiding in pollution control and environmental protection decisions.

Contaminants of emerging concern in water and sediment of the Venice Lagoon, Italy.

This study investigates for the first time the contamination of water and sediment of the Venice Lagoon by twenty Contaminants of Emerging Concern (CECs): three hormones, six pharmaceutical compounds (diclofenac and five antibiotics, three of which are macrolides), nine pesticides (methiocarb, oxadiazon, metaflumizone, triallate, and five neonicotinoids), one antioxidant (BHT), and one UV filter (EHMC). Water and sediment samples were collected in seven sites in four seasons, with the aim of investigating the occurrence, distribution, and possible emission sources of the selected CECs in the studied transitional environment. The most frequently detected contaminants in water were neonicotinoid insecticides (with a frequency of quantification of single contaminants ranging from 73% to 92%), and EHMC (detected in the 77% of samples), followed by BHT (42%), diclofenac (39%), and clarithromycin (35%). In sediment the highest quantification frequencies were those of BHT (54%), estrogens (ranging from 35% to 65%), and azithromycin (46%). Although this baseline study does not highlight seasonal or spatial trends, results suggested that two of the major emission sources of CECs in the Venice Lagoon could be tributary rivers from its drainage basin and treated wastewater, due to the limited removal rates of some CECs in WWTPs. These preliminary results call for further investigations to better map priority emission sources and improve the understanding of CECs environmental behavior, with the final aim of drawing up a site-specific Watch List of CECs for the Venice Lagoon and support the design of more comprehensive monitoring plans in the future.

Evaluating the toxicity effects of thiamethoxam and its main metabolite clothianidin to earthworms (Eisenia fetida) from the perspective of endogenous metabolites.

The widespread application of neonicotinoid insecticides (NNIs) has attracted widespread attention to their potential ecotoxicological effects. In this study, we systematically evaluated the toxic effects of thiamethoxam (TMX) and its metabolite clothianidin (CLO) on earthworms (Eisenia fetida). Specifically, the antioxidant system responses and endogenous metabolite metabolism responses in earthworms were analyzed in the temporal dimension after 7, 14, 21 and 28 days of exposure to TMX and CLO. The results found that TMX and CLO could inhibit the growth phenotype of earthworms and cause significant changes in antioxidant system related indicators. More importantly, we found that TMX and CLO could cause significant changes in the metabolic profiles of earthworms through NMR-based metabolomics. From the changes in endogenous metabolites, the toxicity effects of TMX on earthworms gradually increases with prolonged exposure time. Differently, the toxicity effects of CLO on earthworms is significantly higher than that of TMX in the early stages of exposure. Meanwhile, these impacts will not weaken with prolonged exposure time. Furthermore, the results of KEGG enrichment pathway analysis indicated that TMX and CLO could significantly interfere with energy homeostasis, redox homeostasis, osmotic regulation, amino acid metabolism and protein synthesis in earthworms. These findings further deepen our understanding of the ecotoxicological effects of NNIs on soil organism.

Identification and Coexposure of Neonicotinoid Insecticides and Their Transformation Products in Retail Cowpea (Vigna unguiculata).

There is growing evidence that the transformation products of emerging contaminants in foodstuffs may pose a health risk to humans. However, the exact identities, levels, and estimated dietary intake (EDI) of neonicotinoid transformation products in crops remain poorly understood. We established an extended suspect screening strategy to investigate neonicotinoid insecticides and their transformation products in retail cowpea from 11 cities in Hainan Province, China. Forty-nine transformation products were identified in retail cowpea, of which 22-36 were found in 98.6% of the samples. Notably, 31 new transformation products were derived from new processes or a combination of different transformation processes. The mean concentrations of neonicotinoids and nine of the transformation products (with authentic standards) were in the ranges of 0.0824-5.34 and 0.0636-1.50 ng/g, respectively. The cumulative EDIs of the quantified transformation products were lower than those of parent neonicotinoids with the exception of clothianidin desmethyl, which had a ratio of 1157%. However, the coexistence of the other 40 transformation products (without authentic standards) in cowpea suggested that the exposure risk from all of the transformation products might be higher. This study demonstrated that pesticide transformation products should be considered in food chain risk assessments and included in future regulatory management.

Potential Toxic Mechanisms of Neonicotinoid Insecticides in Rice: Inhibiting Auxin-Mediated Signal Transduction.

Inappropriate application of pesticides not only causes sub-lethal effects on ecosystem service providers but also reduces crop yield and quality. As a xenobiotic signal molecule, pesticides may interact with signal transduction receptors in crops, resulting in oxidative damage and even metabolic perturbations. We discovered that three neonicotinoid insecticides (NIs), namely, imidacloprid, thiamethoxam, and clothianidin, at 0.06-0.12 kg ai/ha significantly inhibited the auxin signal pathway in rice leaves, thereby reducing the intracellular auxin (IAA) content. Molecular simulation further confirmed that NIs occupied the binding site where auxin transporter-like proteins 1 (LAX11) and 2 (LAX12), in which Thr253 and Asn66 of LAX11, as well as Thr244 and Asn57 of LAX12, were bound to the nitroguanidine of NIs via H-bonds. Meanwhile, Asn66 of LAX11 and Asn57 of LAX12 interacted with nitroguanidine via aromatic H-bonds. Moreover, phenylpropanoid biosynthesis was significantly disturbed because of the inhibited auxin signal pathway. Notably, peroxidase-coding genes were downregulated with a maximum value greater than 10-fold, resulting in decreased antioxidant metabolites flavone (37.82%) and lignin content (20.15%). Ultimately, rice biomass was reduced by up to 25.41% due to the decline in IAA content and antioxidant capacity. This study deeply explored the molecular mechanism of metabolic perturbations in crops stressed by pesticides, thus providing a scientific basis for pesticide environmental risk assessment and agricultural product safety.

Synthesis of environmentally friendly neonicotinoid insecticide with proper functional properties by theoretical methodologies.

Modern insecticide substitutes using acetylcholine receptors (nAChR) as biochemical targets, such as neonicotinoid insecticides (NNIs), have been extensively researched. Only 12 compounds have been experimentally realized since the initial discovery of imidacloprid. Increasingly, the bottleneck in this field is to rapidly determine the synthesizability of NNI substitutes. Here, we designed a coupled evaluation system for synthesis prediction and validation, including the synthesis probability, reaction path difficulty, and electron transfer characteristics of NNIs and their substitutes. Firstly, a total of 1475 eigenvalues were generated and 52 critical eigenvalues were screened out through the Pearson's correlation coefficient. The positive and unlabeled (PU) machine learning was constructed using the critical eigenvalues NNIs, including 12 experimentally synthesized NNIs (positive samples) and 73 unsynthesized NNI substitutes (unlabeled samples). Results identified 3 NNI substitutes that were highly promising candidates for synthesis (synthesis probability > 0.5). The results of density functional theory demonstrated the ranking of their reaction ease was UN-1 (31.4 kcal/mol) > UN-2 (81.6 kcal/mol) > UN-3 (3.35 ×103 kcal/mol). Time-dependent density functional theory revealed that changes in the electron distribution and electron excitation type were critical factors affecting their synthesizability, and the local excitation type was more favorable for the synthesizability of NNI substituents. The findings provide significant guidance for NNIs synthesis, reducing the possible space of unlabeled samples to 95.89% of their original size, while also minimizing the cost of research on subsequent NNI substitutes.

Seed treatment with clothianidin induces changes in plant metabolism and alters pollinator foraging preferences.

Neonicotinoids, systemic insecticides that are distributed into all plant tissues and protect against pests, have become a common part of crop production, but can unintentionally also affect non-target organisms, including pollinators. Such effects can be direct effects from insecticide exposure, but neonicotinoids can affect plant physiology, and effects could therefore also be indirectly mediated by changes in plant phenology, attractiveness and nutritional value. Under controlled greenhouse conditions, we tested if seed treatment with the neonicotinoid clothianidin affected oilseed rape's production of flower resources for bees and the content of the secondary plant products glucosinolates that provide defense against herbivores. Additionally, we tested if seed treatment affected the attractiveness of oilseed rape to flower visiting bumblebees, using outdoor mesocosms. Flowers and leaves of clothianidin-treated plants had different profiles of glucosinolates compared with untreated plants. Bumblebees in mesocosms foraged slightly more on untreated plants. Neither flower timing, flower size nor the production of pollen and nectar differed between treatments, and therefore cannot explain any preference for untreated oilseed rape. We instead propose that this small but significant preference for untreated plants was related to the altered glucosinolate profile caused by clothianidin. Thereby, this study contributes to the understanding of the complex relationships between neonicotinoid-treated crops and pollinator foraging choices, by suggesting a potential mechanistic link by which insecticide treatment can affect insect behavior.

Transport of neonicotinoid insecticides in a wetland ecosystem: Has the cultivation of different crops become the major sources?

Extensive application of neonicotinoid insecticides (NNIs) in agricultural production has resulted in widespread contamination of multiple environmental media. To investigate the occurrence and fate of NNIs in the largest marsh distribution area in Northeast China, an integrated ecosystem covering farmlands, rivers, and marshes, referred to as the farmland-river-marsh continuum in this study, was chosen for soil, water, and sediment sampling. Five NNIs were detected, with imidacloprid (IMI), thiamethoxam (THM), and clothianidin (CLO) being the most frequently detected ones in different samples. Concentrations of target NNIs in soil, surface water, and sediment samples were 2.23-136 ng/g dry weight (dw), 3.20-51.7 ng/L, and 1.53-8.40 ng/g dw, respectively. In soils, NNIs were detected more often and at higher concentrations in upland fields, while the concentration of NNIs in the soybean-growing soils (71.5 ng/g dw) was significantly higher than in the rice-growing soils (18.5 ng/g dw) (p < 0.05). Total concentration of NNIs in surface water was lower in the Qixing River channel than inside the marsh, while that in sediments showed an opposite trend. Total migration mass of IMI from approximately 157,000 ha of farmland soil by surface runoff was estimated to be 2636-3402 kg from the application time to the sampling period. The storage of NNIs in sediments was estimated to range from 45.9 to 252 ng/cm2. The estimated environmental risks, calculated as the risk quotients (RQs), revealed low risks to aquatic organisms (RQs <0.1) from the residual concentrations of NNIs in water.

Neonicotinoid Insecticides and Their Metabolites Can Pass through the Human Placenta Unimpeded.

Studies on neonicotinoid (NEO) exposure in pregnant women and fetuses are scarce, and transplacental transfer of these insecticides is unknown. In this study, parent NEOs (p-NEOs) and their metabolites (m-NEOs) were determined in 95 paired maternal (MS) and cord serum (CS) samples collected in southern China. Imidacloprid was the predominant p-NEO in both CS and MS samples, found at median concentrations of 1.84 and 0.79 ng/mL, respectively, whereas N-desmethyl-acetamiprid was the most abundant m-NEO in CS (median: 0.083 ng/mL) and MS (0.13 ng/mL). The median transplacental transfer efficiencies (TTEs) of p-NEOs and m-NEOs were high, ranging from 0.81 (thiamethoxam, THM) to 1.61 (olefin-imidacloprid, of-IMI), indicating efficient placental transfer of these insecticides. Moreover, transplacental transport of NEOs appears to be passive and structure-dependent: cyanoamidine NEOs such as acetamiprid and thiacloprid had higher TTE values than the nitroguanidine NEOs, namely, clothianidin and THM. Multilinear regression analysis revealed that the concentrations of several NEOs in MS were associated significantly with hematological parameters related to hepatotoxicity and renal toxicity. To our knowledge, this is the first analysis of the occurrence and distribution of NEOs in paired maternal-fetal serum samples.

Sex-Dependent Environmental Health Risk Analysis of Flupyradifurone.

Pesticides are used in agricultural production worldwide, resulting in widespread environmental pollution. Many diseases are closely related to exposure to pesticide residues. In this study, the association between exposure to the pesticide flupyradifurone (FPF), a substitute for neonicotinoids, and sex-dependent thyroid dysfunction was explored for the first time. Exposure using rat models revealed that the FPF metabolism is sex-dependent, with males preferring N-dealkylation and hydrolytic metabolism and females preferring hydroxylation. In particular, novel chloropyridine-site hydroxylation I and II metabolic pathways of FPF were discovered. More importantly, differential metabolic pathways of FPF induced sex-based dysregulation of the hypothalamic-pituitary-thyroid axis, in which females exhibited subclinical hyperthyroidism, while males displayed abnormal hypothyroidism. This may be attributed to the potential agonistic or antagonistic effect of FPF sex-dependent metabolites on liver thyroid hormone receptors. Furthermore, FPF exposure further mediated sex-specific dysregulation of cellular lipid homeostasis, with abnormal fatty acid ß-oxidation and excessive energy expenditure in females and the risk of excessive accumulation of triglycerides in males. These results illustrate the potential risk of sex-related thyroid metabolic diseases caused by FPF and provide an important basis and support for further studies of FPF on human health and as an environmental pollutant.

Exposure to neonicotinoid insecticides and their characteristic metabolites: Association with human liver cancer.

Neonicotinoid insecticides (NEOs) are commonly applied for pest control in China and around the world. Previous studies reported that NEOs are hepatotoxic to mammals. However, limited studies have explored the associations between NEOs exposure and liver disease. In the present study, we detected six parent NEOs (p-NEOs), including acetamiprid, thiacloprid, dinotefuran, clothianidin, imidacloprid, and thiamethoxam, and five characteristic metabolites (m-NEOs), including 5-hydroxy-imidacloprid, olefin-imidacloprid, N-desmethyl-acetamiprid, 1-methyl-3-(tetrahydro-3-furylmethyl) guanidine and 1-methyl-3-(tetrahydro-3-furyl methyl) urea, in blood samples collected from healthy donors (n = 100; females vs. males: 45 vs. 55; age: 22-91 years) and liver cancer patients (n = 274; females vs. males: 118 vs. 156; age: 11-88 years) in one hospital from Guangzhou city, South China. NEOs were frequently detected (61%-94%) in blood samples, with median concentrations ranging from 0.19 ng/mL to 1.28 ng/mL and 0.20 ng/mL to 2.03 ng/mL for healthy and liver cancer populations, respectively. olefin-imidacloprid was the most abundant NEOs in healthy and liver cancer populations, accounting for 23.4% and 20.7%, respectively. Significant positive correlations among most m-NEOs concentrations were found, and associations between m-NEOs and their corresponding p-NEOs were positively correlated. These findings indicated that the sources of m-NEOs were both endogenous and exogeneous. Females had higher median concentrations of NEOs and their metabolites than males. Moreover, the α-fetoprotein values and blood concentrations of target analytes (r = 0.428-0.601, p < 0.05) were positively correlated. Meanwhile, associations between the concentrations of p-NEOs and m-NEOs and liver cancer were found (odds ratio = 2.33-9.02, 95% confidence interval = 0.31-22.7, p < 0.05), indicating that human exposure to NEOs and their metabolites might increase the odds of liver cancer prevalence. Our work provided a new insight into the hepatotoxicity of NEOs and their metabolites, and human health risks of exposure to these pollutants warranted further studies.

Occurrence and distribution of neonicotinoids and characteristic metabolites in paired urine and indoor dust from young adults: Implications for human exposure.

Neonicotinoid insecticides (NEOs) are widely used for pest control worldwide. The profile of NEOs in paired urine and indoor dust has not yet been reported in China. In this study, 40 paired samples (i.e., 160 urine and 40 indoor dust) were collected from university students and dormitories from Guangzhou City of China to measure the concentrations of six NEOs and their three metabolites. Target analytes were frequently detected in paired urine (81%-98%) and indoor dust (75%-95%) samples, with median concentrations ranging from 0.02 [specific gravity (SG) adjusted: 0.02] to 2.08 (SG-adjusted: 2.38) ng/mL in urine and from 0.05 to 2.74 ng/g in indoor dust. 5-Hydroxy-imidacloprid was predominant in urine, while N-desmethyl acetamiprid was predominant in indoor dust samples, accounting for 56% and 37%, respectively. 1-Methyl-3-(tetrahydro-3-furylmethyl) urea, a dinotefuran degradate, was measured for the first time in indoor dust, with the median level of 1.02 ng/g. Significant gender-related differences (p < 0.05) in the urinary concentrations of most NEOs were found. We calculated the estimated daily intake (EDI) of target compounds from urine and indoor measurements. The EDIs of target analytes varied among all urine and indoor dust samples, with median values ranging from 0.51 (SG-adjusted: 0.56) to 51.6 (SG-adjusted: 52.8) ng/kg bw/day and from 0.04 to 2.10 pg/kg bw/day, respectively. Moreover, the median EDIsurine of most target analytes in females were significantly higher than (p < 0.05) those in males. The median EDIsdust of target compounds in dust from female dormitories were slightly higher than that in dust from male dormitories. These findings indicated that females were more exposed to NEO than males. Thus, the potential health risks of exposure to NEOs and their metabolites in female adults should be addressed in future studies. To our knowledge, this study is the first to report the profiles of NEOs and their metabolites in paired urine and indoor dust samples from young adults in China.

Profiles of neonicotinoid insecticides and their metabolites in paired saliva and periodontal blood samples in human from South China: Association with oxidative stress markers.

Neonicotinoid insecticides (NEOs) are widely used around the world. The distribution of NEOs in paired saliva and periodontal blood samples was not previously documented in China. In this study, the concentrations of six NEOs and three corresponding metabolites were measured in 188 paired saliva and periodontal blood samples collected from South China. NEOs and their metabolites were frequently detected (68-94%) in paired saliva and periodontal blood, with median levels of 0.01-0.99 ng/mL. 1-Methyl-3-(tetrahydro-3-furylmethyl) urea was the most predominant NEO in paired saliva (39%) and periodontal blood (42%). Gender-related differences in NEOs and their metabolite concentrations were found: males showed lower levels than females. We calculated the concentration ratios between saliva and periodontal blood (S/PB ratios), and found that the median S/PB ratios of NEO and their metabolites were higher than 1, indicating that NEOs and their metabolites were easily excreted via saliva. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) was measured in paired saliva and periodontal blood as a marker of oxidative stress. 8-OHdG concentrations in saliva and periodontal blood were significantly and positively correlated (p < 0.05) with the concentrations of most NEOs and their metabolites in saliva and periodontal blood samples. These findings indicated that exposure to NEOs and their metabolites is associated with oxidative stress. This study is the first to report NEOs and their metabolites in paired saliva and periodontal blood samples collected from South China.

Binary and ternary toxicological interactions of clothianidin and eight commonly used pesticides on honey bees (Apis mellifera).

Although many toxicological evaluations have been conducted for honey bees (Apis mellifera), most of these studies have only focused on the effects of individual chemicals. However, honey bees are usually exposed to pesticide mixtures under field conditions. In this study, we examined the effects of individual pesticides and mixtures of clothianidin (CLO) with eight other pesticides [carbaryl (CAR), thiodicarb (THI), chlorpyrifos (CHL), beta-cyfluthrin (BCY), gamma-cyhalothrin (GCY), tetraconazole (TET), spinosad (SPI) and indoxacarb (IND)] on honey bees using a feeding method. Toxicity tests of a 4-day exposure to individual pesticides revealed that CLO had the highest toxicity to A. mellifera, with an LC50 value of 0.24 µg a.i. mL-1, followed by IND and CHL with LC50 values of 3.40 and 3.56 µg a.i. mL-1, respectively. SPI and CAR had relatively low toxicities, with LC50 values of 7.19 and 8.42 µg a.i. mL-1, respectively. In contrast, TET exhibited the least toxicity, with an LC50 value of 258.7 µg a.i. mL-1. Most binary mixtures of CLO with other pesticides exerted additive and antagonistic effects. However, all the ternary mixtures containing CLO and TET (except for CLO+TET+THD) elicited synergistic responses to bees. Either increased numbers of components in the mixture or/and a unique mode of action appeared to be responsible for the higher toxicity of mixtures. Our findings emphasized the need for risk assessment of pesticide mixtures rather than the individual chemicals. Our data also provided information that might help growers avoid increased toxicity and unnecessary injury to pollinators.

Imidacloprid and thiamethoxam affect synaptic transmission in zebrafish.

Imidacloprid (IMI) and thiamethoxam (THM) are two commonly applied neonicotinoid insecticides. IMI and THM could cause negative impacts on non-target organisms like bees. However, the information about neurotoxicity of IMI and THM in fish is still scarce. Here we investigated the effects of IMI and THM on locomotor behavior, AChE activity, and transcription of genes related to synaptic transmission in zebrafish exposed to IMI and THM with concentrations of 50 ng L-1 to 50,000 ng L-1 at 14 day post fertilization (dpf), 21 dpf, 28 dpf and 35 dpf. Our results showed that IMI and THM significantly influenced the locomotor activity in larvae at 28 dpf and 35 dpf. THM elevated AChE activity at 28 dpf. The qPCR data revealed that IMI and THM affected the transcription of marker genes belonging to the synapse from 14 dpf to 35 dpf. Furthermore, IMI and THM mainly affected transcription of key genes in γ-aminobutyric acid, dopamine and serotonin pathways in larvae at 28 dpf and 35 dpf. These results demonstrated the neurotoxicity of IMI and THM in zebrafish. The findings from this study suggested that IMI and THM in the aquatic environment may pose potential risks to fish fitness and survival.

Paracoccus and Achromobacter bacteria contribute to rapid biodegradation of imidacloprid in soils.

Neonicotinoids are among the most widely used insecticides worldwide, and as such, have garnered increasing attention from the scientific community in regards to their potentially negative environmental impacts. Recently, the degradability of neonicotinoid in soil has gained more attentions. However, what role soil microbes play in this degradation remains vastly underexplored. In this study, we compared the capacity of soil microbes sampled from different geographic regions and fields to degrade the neonicotinoid insecticide imidacloprid. Additionally, the composition of microbiota having low, middle, and high degradation activity was analyzed via high throughput sequencing. Correlations between microbiota composition and degradation activities were analyzed and reconfirmed. The results showed that the composition of soil microbiota and their degradation activity (ranged from zero to 96.25%) varied significantly between soil samples from different geographic locations. Correlation analysis showed that Paracoccus and Achromobacter bacteria were positively correlated with high degradation activity. Imidacloprid degradation experiments using these bacteria showed that Achromobacter sp. alone exhibited degradation activity reaching and sustaining 100% by day 20 while Paracoccus sp. did not. However, combining these bacteria resulted in increased degradation activity which reached 100% at day 15 relative to that achieved by Achromobacter sp. alone. This study demonstrated the capacity of soil microbes to degrade imidacloprid, and identified two promising bacterial candidates that could be potentially used in future to reduce imidacloprid accumulation in soils.

Simultaneous analysis of current-use pesticides and their transformation products in water using mixture-sorbent solid phase extraction and high-performance liquid chromatography-tandem mass spectrometry.

Pesticides have posed significant threats to aquatic ecosystems, yet little is known about their transformation products. The challenge is to simultaneously analyze various pesticides and transformation products in water as they have distinct physicochemical properties. A mix-mode solid phase extraction method was established to simultaneously analyze current-use pesticides and their transformation products using a mixture of hydrophile-lipophile balance, weak anion, and cation exchange resins (2:1:1, w/w/w) in combination with high-performance liquid chromatography and tandem mass spectrometry for chemical quantification. Neutral, acidic, and alkaline methanol were used as the elution solvent. Box-Behnken design was applied to optimize extraction conditions. Optimal conditions were as follows: sorbent mass, 200 mg; volume of elution solvent, 5 mL × 3; pH 4. The method was validated for compounds at concentrations from 20 to 1000 ng/L in different types of water samples, with recovery being from 43.5 ± 3.1 to 141 ± 35%. Low method detection limits (0.02-5.6 ng/L) implied that the developed method was sensitive. Finally, the method was applied to monitor current-use pesticides and their transformation products in natural waters. Frequent detection of transformation products of pesticides indicated that their contribution to aquatic risk should not be ignored.

Neonicotinoids caused oxidative stress and DNA damage in juvenile Chinese rare minnows (Gobiocypris rarus).

To assess the effects of neonicotinoid insecticides on fish, juvenile Chinese rare minnows (Gobiocypris rarus) were exposed to 0.1, 0.5, or 2.0 mg/L neonicotinoid insecticides (imidacloprid, nitenpyram, and dinotefuran) for 60 days. The endpoints, including oxidative stress and DNA damage, were determined. The results of oxidative stress assays showed that SOD activities were significantly increased in the 2.0 mg/L imidacloprid and 0.5 mg/L nitenpyram and dinotefuran treatments (p < 0.05). CAT activity was significantly increased with 0.1 mg/L nitenpyram (p < 0.05), whereas it was significantly decreased in the 0.1 and 2.0 mg/L dinotefuran treatment groups (p < 0.05). Moreover, MDA content was significantly decreased in all imidacloprid treatments and in the 0.5 and 2.0 mg/L dinotefuran treatments (p < 0.05); however, it was significantly increased in the 0.1 mg/L nitenpyram treatment (p < 0.05). GSH content was significantly increased at all treatments except for the 0.5 mg/L dinotefuran treatment (p < 0.05). The transcript expression results showed that gstm mRNA expression was significantly inhibited by 0.5 and 2.0 mg/L imidacloprid, and gstp1 mRNA expression was significantly inhibited by all nitenpyram treatments (p < 0.05). In addition, ugt1a mRNA expression was significantly inhibited in the 0.5 mg/L nitenpyram treatment (p < 0.05). The results of the DNA damage assay showed that tail moments were significantly increased by the 2.0 mg/L imidacloprid treatment (p < 0.01), while tail DNA was significantly increased by 0.5 and 2.0 mg/L imidacloprid, 2.0 mg/L nitenpyram and all dinotefuran treatments (p < 0.01). Moreover, olive tail moments were significantly increased by the 0.5 and 2.0 mg/L imidacloprid and 2.0 mg/L dinotefuran treatments (p < 0.01). Therefore, our oxidative stress and DNA damage findings demonstrated that imidacloprid and nitenpyram could cause adverse effects on juvenile rare minnows.

Dual amplification in a fluorometric acetamiprid assay by using an aptamer, G-quadruplex/hemin DNAzyme, and graphene quantum dots functionalized with D-penicillamine and histidine.

D-penicillamine and histidine-functionalized graphene quantum dot (DPA-GQD-His) was synthesized and applied in a fluorometric method for determination of acetamiprid using a G-quadruplex DNAzyme. At first DNA probe (probe 1) consists of a target-specific aptamer with two arms of DNA segments. Probe 1 was hybridized with DNA probe 2 composed of a single DNA sequence with two split G-rich DNA sequences. This leads to the formation of a triplex-to-G-quadruplex (TPGQ). Next, acetamiprid was hybridized with the aptamer in the TPGQ to release free DNA probe 2. The released probe 2, in the presence of of K+, undergoes a structural change into a stem-loop structure (by self-complementary hybridization and Hoogsteen hydrogen bonding) that bears a G-quadruplex structure. This is followed by conjugation with hemin to form the G-quadruplex/hemin DNAzyme. The DNAzyme catalyzes the oxidation of o-phenylenediamine by H2O2 to produce a yellow fluorescent product with excitation/emission maxima at 420/560 nm. The oxidation product interacts with DPA-GQD-His to achieve a rapid energy transfer between DPA-GQD-His and oxidation product. This increases the fluorescence of the oxidation product and quenches the fluorescence of DPA-GQD-His. DPA-GQD-His also improves the catalytic activity of DNAzyme towards oxidation of ophenylenediamine oxidization and enhances fluorometric response to acetamiprid. The assay works in the 1.0 fM to 1.0 nM acetamiprid concentration range and has a 0.38 fM detection limit. It was successfully applied to the determination of acetamiprid in tea. Graphical abstractThe study reported one double amplification strategy for ultrasensitive fluorescence detection of acetamiprid in tea with D-penicillamine and histidine-functionalized graphene quantum dots and G-quadruplex/heminDNAzyme. The analtyical method exhibits ultra high sensitivity, selectivity and rapidity of fluorescence response to acetamiprid.