Computational design and preparation of water-compatible noncovalent imprinted microspheres.

Herein, 2,4-dichlorophenoxyacetic acid (2,4-D) was used as a model template in a rational design strategy to produce water-compatible noncovalent imprinted microspheres. The proposed approach involved computational modelling for screening functional monomers and a simple method for preparing monodisperse and highly cross-linked microspheres. The fabricated non-imprinted polymer (NIP) and 2,4-d-imprinted polymer (2,4-d-MIP) were characterised, and their adsorption capabilities in an aqueous environment were evaluated. Results reveal that the pseudo-second-order kinetics model was appropriate for representing the adsorption of 2,4-D on NIP and 2,4-d-MIP, with R2 values of 0.97 and 0.99, respectively. The amount of 2,4-D adsorbed on 2,4-d-MIP (97.75 mg g-1) was considerably higher than those of phenoxyacetic acid (35.77 mg g-1), chlorogenic acid (9.72 mg g-1), spiramycin (1.56 mg g-1) and tylosin (1.67 mg g-1). Furthermore, it exhibited strong resistance to protein adsorption in an aqueous medium. These findings confirmed the feasibility of the proposed approach, providing a reference for the development of water-compatible noncovalent imprinted polymers.

Exposure to Agent Orange is associated with increased recurrence after surgical treatment of stage I non-small cell lung cancer.

OBJECTIVE: Approximately 3 million Americans served in the armed forces during the Vietnam War. Veterans have a higher incidence rate of lung cancer compared with the general population, which may be related to exposures sustained during service. Agent Orange, one of the tactical herbicides used by the armed forces as a means of destroying crops and clearing vegetation, has been linked to the development of several cancers including non-small cell lung cancer. However, traditional risk models of lung cancer survival and recurrence often do not include such exposures. We aimed to examine the relationship between Agent Orange exposure and overall survival and disease recurrence for surgically treated stage I non-small cell lung cancer. METHODS: We performed a retrospective cohort study using a uniquely compiled dataset of US Veterans with pathologic I non-small cell lung cancer. We included adult patients who served in the Vietnam War and underwent surgical resection between 2010 and 2016. Our 2 comparison groups included those with identified Agent Orange exposure and those who were unexposed. We used multivariable Cox proportional hazards and Fine and Gray competing risk analyses to examine overall survival and disease recurrence for patients with pathologic stage I disease, respectively. RESULTS: A total of 3958 Vietnam Veterans with pathologic stage I disease were identified (994 who had Agent Orange exposure and 2964 who were unexposed). Those who had Agent Orange exposure were more likely to be male, to be White, and to live a further distance from their treatment facility (P < .05). Tumor size distribution, grade, and histology were similar between cohorts. Multivariable Cox proportional hazards modeling identified similar overall survival between cohorts (Agent Orange exposure hazard ratio, 0.97; 95% CI, 0.86-1.09). Patients who had Agent Orange exposure had a 19% increased risk of disease recurrence (hazard ratio, 1.19; 95% CI, 1.02-1.40). CONCLUSIONS: Veterans with known Agent Orange exposure who undergo surgical treatment for stage I non-small cell lung cancer have an approximately 20% increased risk of disease recurrence compared with their nonexposed counterparts. Agent Orange exposure should be taken into consideration when determining treatment and surveillance regimens for Veteran patients.

Association of PKLR gene copy number, expression levels and enzyme activity with 2,3,7,8-TCDD exposure in individuals exposed to Agent Orange/Dioxin in Vietnam.

2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) is the most toxic congener of dioxin and has serious long-term effects on the environment and human health. Pyruvate Kinase L/R (PKLR) gene expression levels and gene variants are associated with pyruvate kinase enzyme deficiency, which has been identified as the cause of several diseases linked to dioxin exposure. In this study, we estimated PKLR gene copy number and gene expression levels using real-time quantitative PCR (RT-qPCR) assays, genotyped PKLR SNP rs3020781 by Sanger sequencing, and quantified plasma pyruvate kinase enzyme activity in 100 individuals exposed to Agent Orange/Dioxin near Bien Hoa and Da Nang airfields in Vietnam and 100 healthy controls. The means of PKLR copy numbers and PKLR gene expression levels were significantly higher, while pyruvate kinase enzyme activity was significantly decreased in Agent Orange/Dioxin-exposed individuals compared to healthy controls (P < 0.0001). Positive correlations of PKLR gene copy number and gene expression with 2,3,7,8-TCDD concentrations were observed (r = 0.2, P = 0.045 and r = 0.54, P < 0.0001, respectively). In contrast, pyruvate kinase enzyme activity was inversely correlated with 2,3,7,8-TCDD concentrations (r = -0.52, P < 0.0001). PKLR gene copy number and gene expression levels were also inversely correlated with pyruvate kinase enzyme activity. Additionally, PKLR SNP rs3020781 was found to be associated with 2,3,7,8-TCDD concentrations and PKLR gene expression. In conclusion, PKLR copy number, gene expression levels, and pyruvate kinase enzyme activity are associated with 2,3,7,8-TCDD exposure in individuals living in Agent Orange/Dioxin-contaminated areas.

Elevated 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide concentrations in the household dust of farmers with recent occupational use.

Pesticide dust concentrations in homes have been previously associated with occupational and home/garden use of pesticides, hygiene practices, and other factors. This study evaluated the relationship between self-reported use of 2,4-dichlorophenoxyacetic acid (2,4-D) and house dust concentrations and these factors in the Biomarkers of Exposure and Effect in Agriculture (BEEA) Study, a molecular epidemiologic study of farmers in Iowa and North Carolina. The vacuum dust from the homes of 35 BEEA participants was analyzed for the presence of 2,4-D. Participants provided detailed information on occupational and home/garden pesticide use during the past 12 months and reported household characteristics via questionnaires. Linear regression models were used to examine the association between 2,4-D concentrations and four exposure metrics for occupational use in the last 12 months (yes/no, days since last use, days of use, intensity-weighted days of use), home/garden use (yes/no), as well as several household characteristics. 2,4-D was detected in all homes and was used occupationally by 54% of the participants. In a multi-variable model, compared to homes with no occupational or home/garden 2,4-D use reported in the past 12 months, concentrations were 1.6 (95% confidence interval (CI): 0.5, 4.9) times higher in homes with low occupational 2,4-D use (intensity-weighted days < median) and 3.1 (95% CI: 1.0, 9.8) times higher in homes of participants with high use (≥median intensity-weighted days) (p-trend = 0.06). Similar patterns were observed with other occupational metrics. Additionally, 2,4-D dust concentrations were non-significantly elevated (relative difference (RD) = 1.8, 95% CI: 0.5, 6.2) in homes with home/garden use and were significantly lower in homes that did not have carpets (RD = 0.20, 95% CI: 0.04, 0.98). These analyses suggest that elevated 2,4-D dust concentrations were associated with several metrics of recent occupational use and may be influenced by home/garden use and household characteristics.

Detection of 2,4-dichlorophenoxyacetic acid in water sample by organosilane based silica nanocomposites.

The present study aims to produce nanocomposites of silica based organosilane as sensitive and selective fluorescent sensor for the recognition of 2,4 dichlorophenoxyacetic acid (2,4-D). Hydrazone tethered triazole functionalized organosilane has been synthesized by the condensation reaction of 4-hydroxybenzaldehyde and phenyl hydrazine followed by Cu(I) catalysed cycloaddition of azide with alkyne. The prepared compound has been further grafted over silica surface and the synthesized materials were characterized by FT-IR, NMR (1H and 13C), XRD, mass spectrometry and FE-SEM spectral analyses. The prepared organosilane and its HSNPs have been utilized as an effective emission probe for the selective detection of 2,4 D with good linear relationship in the range of 0-160 µM and 0-115 µM and LOD value of 46 nM and 13.5 nM respectively. In the presence of other active species, the sensor shows minimal interference while the comparison with the previously reported techniques suggests it to be more desirable for the sensitive and selective detection of 2,4 D. Further, the real sample application for detection of 2,4 D was analyzed in field water and the HSNPs based sensing system gave recovery percentage of above 98 %.

Preparation of complex biological sample-compatible "turn-on"-type ratiometric fluorescent molecularly imprinted polymer microspheres via one-pot surface-initiated ATRP.

The efficient preparation of ratiometric fluorescent molecularly imprinted polymer (MIP) microspheres that can directly and selectively optosense a herbicide (i.e., 2,4-dichlorophenoxyacetic acid, 2,4-D) in undiluted pure milk is described. The dual fluorescent MIP microparticles were readily obtained through grafting a green 4-nitrobenzo[c][1,2,5]oxadiazole (NBD)-labeled 2,4-D-MIP layer with hydrophilic polymer brushes onto the preformed uniform "living" red CdTe quantum dot (QD)-labeled SiO2 microspheres via one-pot surface-initiated atom transfer radical polymerization (SI-ATRP) in the presence of a polyethylene glycol macro-ATRP initiator. They proved to be highly promising "turn-on"-type fluorescent chemosensors with red CdTe QD (the maximum emission wavelength λe,max around 710 nm) and green NBD (λe,max around 515 nm) as the reference fluorophore and "turn-on"-type responsive fluorophore, respectively. The sensors showed excellent photostability and reusability, high 2,4-D selectivity and sensitivity (the limit of detection = 0.12 µM), and direct visual detection ability (a fluorescent color change occurs from red to blue-green with the concentration of 2,4-D increasing from 0 to 100 µM) in pure bovine milk. The sensors were used for 2,4-D detection with high recoveries (96.0-104.0%) and accuracy (RSD ≤ 4.0%) in pure goat milk at three spiking levels of both 2,4-D and its mixtures with several analogues. This new strategy lays the foundation for efficiently developing diverse complex biological sample-compatible ratiometric fluorescent MIPs highly useful for real-world bioanalyses and diagnostics.

[Simultaneous determination of 40 plant growth regulators, fungicides, insecticides, and antibiotics in bean sprouts by QuEChERS-high performance liquid chromatography-tandem mass spectrometry].

Chromatography combined with mass spectrometry is the most commonly used detection technology, and it offers the advantages of high sensitivity and high selectivity. The quick, easy, inexpensive, effective, rugged, and safe (QuEChERS) method is low-cost, effective, and time efficient. The application of the QuEChERS has now been extended to the analysis of contaminants in food samples. The aim of the study was to identify different concentration levels of multiple harmful drug residues in bean sprouts. In this study, QuEChERS coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established for the simultaneous determination of 40 plant growth regulators, fungicides, insecticides, and antibiotics in bean sprouts. In the HPLC-MS/MS experiment, gibberellic acid, 4-fluorophenoxyacetic acid, chloramphenicol, N6-(δ2-isopentenyl)-adenine, 6-benzylaminopurine, 4-chlorophenoxyacetic acid, and 2,4-dichlorophenoxyacetic acid (2,4-D) were analyzed by MS/MS with negative electrospray ionization (ESI-). The other 33 target analytes (chlormequat, ronidazole, metronidazole, pymetrozine, dimetridazole, methomyl, carbendazim, enoxacin, levofloxacin, pefloxacin mesylate, norfloxacin, ciprofloxacin, enrofloxacin, thiabendazole, lomefloxacin, chlorpyrifos, sarafloxacin, imidacloprid, etc.) were analyzed by MS/MS with positive electrospray ionization (ESI+). Sensitive MS conditions were realized by optimizing the instrumental parameters such as the desolvent temperature, collision energy, spraying needle position, precursor ions, and product ions. Then, the optimal pretreatment method was determined by comparing the recovery rates of the 40 drugs obtained with different extraction solvents (methanol, acetonitrile, acetonitrile containing 0.1% ammonia, acetonitrile with 1% acetic acid), different extraction methods (ultrasonic extraction, shaking extraction), and purification with primary secondary amine (PSA) and C18. In this study, the bean sprouts samples were extracted twice by 10 mL acetonitrile with 1% acetic acid, and extracted under ultrasonic conditions. Then, the extracting solution was only cleaned with 100 mg C18. The chromatographic separation of the 40 compounds was accomplished on a Waters ACQUITY UPLC BEH C18 column (100 mm×2.1 mm, 1.7 µm) with gradient elution. Methanol and 0.01% formic acid aqueous solution were used as the mobile phases. The 40 compounds were analyzed in the multiple reaction monitoring (MRM) mode. The matrix matching external standard method was used for quantitative determination. The results showed that the 40 compounds could be analyzed within 15 min. Under the optimized conditions, the calibration curves showed good linearities for the 40 compounds, and the coefficients of determination (r2) were greater than 0.99 in the range of 2-200 µg/L. The limits of detection (LODs) and limits of quantification (LOQs) were in the range of 0.1-3 µg/kg and 0.3-9 µg/kg, respectively. Using negative bean sprouts as the substrates, the recovery tests were carried out at three spiked levels of 5, 10, and 50 µg/kg. The average recoveries of the 40 drugs were 78.5% to 115.3%, and the corresponding relative standard deviations (RSDs) were 1.3% to 9.7% (n=6). This method was successfully applied to the analysis of the 40 drug residues in 21 batches of local bean sprouts in Handan city. The results revealed the presence of extensive drug residues in the bean sprouts. The 26 batches were detected to varying degrees, among which 4-chlorophenoxyacetic acid, carbendazim, 6-benzyladenine, 2,4-D, enrofloxacin, and metronidazole were detected at high rates. The detection rates of 4-chlorophenoxyacetic acid, 6-benzyladenine, carbendazim, 2,4-D, gibberellic acid, and enrofloxacin were 28.6%, 19.0%, 9.5%, 9.5%, 4.8%, and 4.8%, respectively. The contents ranged from 37.5-352.4, 32.4-273.1, 28.8-38.7, 316.1-20.2, 19.9 and 13.6 µg/kg, respectively. Given its advantages of simplicity, rapidness, and high sensitivity, the developed method can be used for the rapid and accurate determination of trace levels of the 40 drug residues in large quantities of bean sprouts.

Molecularly imprinted core-shell Au nanoparticles for 2,4-dichlorophenoxyacetic acid detection in milk using surface-enhanced Raman spectroscopy.

Surface-enhanced Raman spectroscopy (SERS) has been extensively investigated for rapid and sensitive detection of trace level chemical contaminants in foods. Lack of selectivity to the targeted molecules in food matrices and fairly poor spectral reproducibility remain the main challenges for practical SERS applications. Herein, an ingenious strategy was proposed to hybridize molecularly imprinted polymers (MIPs) with gold nanoparticles as the functional SERS substrate for selective separation and detection of 2,4-dichlorophenoxyacetic acid (2,4-D), a systemic herbicide that has acute toxicity and potential cancer risk. The core-shell AuNPs@MIPs nanoparticles were finely tailored by wrapping an ultrathin layer of MIPs shell on the surface of AuNPs, which allowed selectively separating and enriching 2,4-D to the near surface of AuNPs and ensured the enhancement of Raman scattering signal of the analyte. Embedding an internal standard (i.e., 4-aminothiophenol) inside AuNPs@MIPs for SERS spectral calibration improved the quantification accuracy for 2,4-D. Three-dimensional finite difference time domain (3D-FDTD) simulation demonstrated the maximal electric field enhancement presented in the gap between adjacent AuNPs@MIPs with the theoretical enhancement factor (EF) as high as 5.85 × 106. Chemometric models established using SERS spectra showed accurate differentiation and quantification results for 2,4-D in milk at various contamination levels with a limit of detection (LOD) of 0.011 µg/mL. Our approach to integrate MIPs with noble metallic nanoparticles has great potential for selective and quantitative detection of analytes using SERS for practical agri-food analysis.

Development of a Rapid Gold Nanoparticle Immunochromatographic Strip Based on the Nanobody for Detecting 2,4-DichloRophenoxyacetic Acid.

2,4-Dichlorophenoxyacetic acid (2,4-D) is a systemic conductive herbicide widely used across the world. With the large-scale and continuous use of 2,4-D, its possible harm to the environment and non-target organisms has attracted increasing attention, and the construction of a stable rapid on-site detection method is particularly important. In order to achieve on-site rapid detection of 2,4-D, we developed a gold nanoparticle immunochromatographic strip method with the visual elimination value was 50 ng/mL, and a quantitative detection limit of 11 ng/mL based on a nanobody. By combing with the color snap, the immunochromatographic strip could quantitatively analyze the amounts of 2,4-D. Meanwhile, a colorimetric card based on the true color of the test strips was developed for the qualitative analysis of 2,4-D on-site. The samples (water, fruits and vegetables) with and without 2,4-D were detected by the immunochromatographic strips, and the results showed the accuracy and reliability. Thus, this assay is a rapid and simple on-site analytical tool to detect and quantify 2,4-D levels in environmental samples, and the analytical results can be obtained in about ten minutes. In addition, the nanobody technology used in this study provides an inexhaustible supply of a relatively stable antibodies that can be archived as a nanobody, plasmid or even its sequence.

An ic-ELISA and immunochromatographic strip assay for the detection of 2,4-dichlorophenoxyacetic acid in bean sprouts and cabbage.

The compound 2,4-dichlorophenoxyacetic acid (2,4-D) is a synthetic plant growth regulator, which is widely used in agricultural production. Consequently, it is necessary to establish a rapid and sensitive detection method to monitor its use and prevent the environmental and human health problems caused by overuse. In this study, a monoclonal antibody (mAb) 2D5 against 2,4-D was prepared, and based on it, an ic-ELISA and an immunochromatographic strip assay (ICA) were developed for rapid detection. The 50% inhibitory concentration (IC 50) of the mAb against 2,4-D was 1.7 ng mL-1 and the mAb showed no cross-reactivity with other plant growth regulators with similar structures to 2,4-D. Under optimum conditions, the ICA showed a visual detection limit (vLOD) of 20 ng mL-1 and a cut-off value of 200 ng mL-1 in bean sprouts, and cabbage samples gave the same results. The quantitative detection showed the linear detection ranges for bean sprouts and cabbage samples were 6.3-73.0 and 5.4-132.6 ng mL-1, respectively. The ICA was successfully applied to detect 2,4-D in bean sprouts and cabbage samples and achieved good recoveries ranging from 94.7% to 104.3% with a coefficient of variation (CV) less than 8.3%. Hence, the ICA provides a sensitive, efficient and reliable detection method, which has broad application prospects in the detection of a large number of samples.

The association between 2,4-D and serum testosterone levels: NHANES 2013-2014.

BACKGROUND: Previous studies have investigated associations between herbicides such as 2,4-Dichlorophenoxyacetic acid (2,4-D) and dyshormonogenesis, specifically low testosterone, in human, rodent, and cell models, but results have been conflicting and inconclusive. METHODS: Using data from a cross-sectional study of 456 adult men in the 2013-2014 NHANES survey cycle, we examined the relationship between urinary concentrations of 2,4-D and serum testosterone levels. RESULTS: Multivariable regression models adjusting for potential confounders revealed a significant, negative association between urinary 2,4-D and mean serum testosterone among U.S. adult males (ß = - 11.4 ng/dL, p = 0.02). Multivariable logistic regression models using a cutoff defining abnormally low testosterone (i.e., serum testosterone < 300 ng/dL) revealed no significant associations between 2,4-D and the odds of low testosterone. CONCLUSION: These findings expand on previous literature implicating a role for 2,4-D in the etiology of low testosterone and dyshormonogenesis. Future studies are warranted to corroborate these findings, determine clinical significance, and to investigate the proposed potential biological mechanisms underlying this association.

Adsorption of atrazine and 2,4-D pesticides on alternative biochars from cedar bark sawdust (Cedrella fissilis).

Bark residues of the forest species Cedrela fissilis were physically and chemically modified with zinc chloride (ZnCl2) as an activating agent. The two modified materials were analyzed as adsorbents in removing atrazine and 2,4-D herbicides from effluents. Firstly, the precursor material and the modified ones were characterized by different techniques to identify the structural changes that occurred in the surfaces. Through TGA, it was observed that both modified materials have thermal stability close to each other and are highly superior to the precursor. X-ray diffractions proved that the amorphous structure was not altered, the three materials being highly heterogeneous and irregular. The micrographs showed that the treatments brought new spaces and cavities on the surface, especially for the material carbonized with ZnCl2. The pHPZC of the modified materials was close to 7.5. The physically modified material had a surface area of 47.31 m2 g-1 and pore volume of 0.0095 cm3 g-1, whereas the carbonized material had a surface area of 98.12 m2 g-1 and pore volume of 0.0099 cm3 g-1. Initial tests indicated that none of the adsorbents were efficient in removing 2,4-D. However, they showed good potential for removing atrazine. The Koble-Corrigan isothermal model best fits the experimental data, with a maximum capacity of 3.44 mg g-1 and 2.70 mg g-1 for physically modified and with ZnCl2, respectively. The kinetic studies showed that the system tends to enter into equilibrium after 120 min, presenting good statistical indicators to the linear driving force model (LDF). The surface diffusion coefficients were 2.18×10-9 and 2.37×10-9 cm2 s-1 for atrazine adsorption on the physically and chemically modified materials. These results showed that the application of residues from the processing of cedar bark is promising. However, new future studies must be carried out to improve the porous development of the material and obtain greater adsorption capacities.

Terahertz fingerprint characterization of 2,4-dichlorophenoxyacetic acid and its enhanced detection in food matrices combined with spectral baseline correction.

Rapid and accurate detection of pesticide residues in food matrices are of great significance to food safety. This study aimed to characterize the fingerprint peaks of 2,4-dichlorophenoxyacetic acid (2,4-D) and to enhance its detection accuracy in food matrices by using terahertz (THz) time-domain spectroscopy. Density functional theory was used to simulate molecular dynamics of 2,4-D peaks (1.35, 1.60, 2.37 and 3.00 THz). Four baseline correction methods, including asymmetric least squares smoothing (AsLS), adaptive iteratively reweighted penalized least squares (AirPLS), background correction (Backcor), baseline estimation and denoising with sparsity (BEADS) were compared and used to eliminate spectral baselines of Zizania latifolia (ZIZLA), rice and maize containing 2,4-D residues, from 0.1 to 4 THz. Based on the peak information of 1.35 THz, the detection limit and accuracy of 2,4-D residues in these food matrices were significantly improved after THz spectral baseline correction, providing a new feasibility for food safety and agricultural applications.

Signal optimized rough silver nanoparticle for rapid SERS sensing of pesticide residues in tea.

Trace detection of toxic chemicals in foodstuffs is of great concern in recent years. Surface-enhanced Raman scattering (SERS) has drawn significant attention in the monitoring of food safety due to its high sensitivity. This study synthesized signal optimized flower-like silver nanoparticle-(AgNP) with EF at 25 °C of 1.39 × 106 to extend the SERS application for pesticide sensing in foodstuffs. The synthesized AgNP was deployed as SERS based sensing platform to detect methomyl, acetamiprid-(AC) and 2,4-dichlorophenoxyacetic acid-(2,4-D) residue levels in green tea via solid-phase extraction. A linear correlation was twigged between the SERS signal and the concentration for methomyl, AC and 2,4-D with regression coefficient of 0.9974, 0.9956 and 0.9982 and limit of detection of 5.58 × 10-4, 1.88 × 10-4 and 4.72 × 10-3 µg/mL, respectively; the RSD value < 5% was recorded for accuracy and precision analysis suggesting that proposed method could be deployed for the monitoring of methomyl, AC and 2,4-D residue levels in green tea.

Cellulose paper-based SERS sensor for sensitive detection of 2,4-D residue levels in tea coupled uninformative variable elimination-partial least squares.

Food safety is a growing concern in recent years. This work presents the design of a simple and sensitive method for predicting 2,4-D (2,4-dichlorophenoxyacetic acid) residue levels in green tea extract employing surface-enhanced Raman spectroscopy (SERS) coupled uninformative variable elimination-partial least squares (UVE-PLS). Herein, SERS active citrate functionalized silver nanoparticles (AgNPs) with enhancement factor 1.51 × 108 was used to prepare cellulose paper (common office) templated SERS sensor for acquiring SERS spectra of 2,4-D. The principle of the work was based on the interaction between 2,4-D and citrate group of AgNPs via chlorine atoms in the concentration range 1.0 × 10-4 to 1.0 × 103 µg/g. Three different wavenumber selection chemometric algorithms were studied comparatively to build an optimum calibration model, among them UVE-PLS showed enhanced performance as evident from the RPD value of 6.01 and Rp = 0.9864. Under optimized experimental condition proposed paper-based SERS sensor exhibited detection limit and RSD of 1.0 × 10-4 µg/g and <5%, respectively. In addition, the validation results by HPLC method were satisfactory (p > 0.05).

Impact of dichlorprop on soil microbial community structure and diversity during its enantioselective biodegradation in agricultural soils.

Enantioselective biodegradation of racemic dichlorprop in two soils was investigated in the laboratory. Chiral separation of racemic dichlorprop was achieved by using HPLC with Phenomenex Lux Amylose-2. The first-order kinetic model fitted well the dissipation data of racemic dichlorprop and its pure R- and S-enantiomers. S-dichlorprop was preferentially degraded in both soils and enantioselectivity was affected by soil pH. The half-lives (DT50) of S-dichlorprop were 8.22 days in soil A and 8.06 days in soil D, while R-dichlorprop was more persistent with DT50 of 12.93 days in soil A and 12.38 days in soil D, respectively. Dichlorprop dissipated faster in soil D with lower organic matter content. In sterilized soils, neglected dissipation was observed and enantiomer fraction values remained constant, indicating that the enantioselective degradation was mainly controlled by soil microorganisms. Soil microbial community structure and diversity was assessed by Illumina MiSeq sequencing of 16S rRNA genes from dichlorprop and no dichlorprop contaminated microcosms. Compared with controls, dichlorprop application had no significant effect on microbial community structures at phylum level, but increased bacterial diversity and dichlorprop degradation related taxa in both soils. S-dichlorprop preferential degradation might be attributed to the S-enantiomer preferred degraders in the family of Sphingomonadaceae.

Smartphone-Assisted Robust Sensing Platform for On-Site Quantitation of 2,4-Dichlorophenoxyacetic Acid Using Red Emissive Carbon Dots.

On-site quantitative analysis of pesticide is of significant importance for addressing serious public health issues in clinical, food, and environmental settings. Herein, we designed a novel smartphone-assisted sensing platform for on-site monitoring of 2,4-dichlorophenoxyacetic acid (2,4-D) based on carbon dots/cobalt oxyhydroxide nanosheet (CDs/CoOOH) composite. In this work, a red emissive CDs/CoOOH composite was proposed as a signal indicator for shielding background interference, enhancing anti-interference capability. 2,4-D as an inhibitor of alkaline phosphatase could specifically suppress the production of ascorbic acid, which restrained in situ etching of the CDs/CoOOH composite and further triggered the fluorescence response of the biosensor. By employing a lab-on-smartphone based device and self-designed application software, the fluorescence image was directly captured and analyzed with a sensitive detection limit of 100 µg L-1 for 2,4-D. Merging the CDs/CoOOH composite-based fluorometric system with the smartphone-assisted optical reader, such a cost-effective and portable platform provided a new sight for on-site monitoring of pesticide and expanded application prospect in the field of biological analysis.

Detection of 2,4-dichlorophenoxyacetic acid herbicide using a FGE-sulfatase based whole-cell Agrobacterium biosensor.

2,4-Dichlorophenoxyacetic acid (2,4-D) has been widely used as a herbicide for agricultural purposes. Currently, the available methods for detecting 2,4-D require multi-step sample preparations and expensive instruments. The use of a whole cell biosensor is an interesting approach that is straightforward and simple to use. In this study, we constructed a genetic-based Agrobacterium tumefaciens biosensor based on a cadA promoter and cadR regulator from Bradyrhizobium sp. strain HW13 (2,4-D degrader) with a formylglycine generating enzyme (FGE)-sulfatase as the reporter gene. The performance of the biosensor was further improved through direct evolution of the cadR activator. The detection limit of cadR mutants for phenoxyacetic acid herbicides including 2,4-D and 4-Chlorophenoxyacetic acid (4-CPAA) were 1.56 µM (an eight-fold improvement compared to wild-type CadR). The biosensor could detect 2,4-D contamination in environmental samples without encountering interference from other complex compounds. The Agrobacterium biosensor was also stable after storing in a simple Luria-Bertani (LB) medium at 4 °C for 30 days where the activity remained at 82% when exposed to 100 µM of 2,4-D. This novel biosensor, with its high stability under simple storage conditions, exhibits promising potential to be used as an inexpensive and easy-to-use tool to screen for 2,4-D contamination in environmental sources.

SERS-based rapid detection of 2,4-dichlorophenoxyacetic acid in food matrices using molecularly imprinted magnetic polymers.

In order to remove the limitations of natural antibodies or enzymes, a nano-magnetic biomimetic platform based on a surface-enhanced Raman scattering (SERS) sensor has been developed for highly sensitive capture and detection of 2,4-dichlorophenoxyacetic acid (2,4-D) in food and water samples. Magnetic-based molecular imprinted polymer nanoparticles (Mag@MIP NPs) were constructed to capture the target 2,4-D molecule via biomimetic recognition, and gold nanoparticles (Au NPs) served as SERS-based probes, which are bound to the Mag@MIP NPs by electrostatic adsorption. The as-prepared SERS-MIP sensor for sensing of 2,4-D achieved a good linear relationship with a low detection limit (LOD) of 0.00147 ng/mL within 2 h and exhibited high sensitivity. The sensor was successfully applied to detect 2,4-D in milk and tap water and achieved good recoveries ranging from 93.5 to 102.2%. Moreover, the designed sensor system exhibited satisfactory results (p > 0.05) compared to HPLC by validation analysis. Hence, the findings demonstrated that the proposed method has significant potential for practical application in food safety and environmental protection. Graphical abstract .

Primary production of freshwater microbial communities is affected by a cocktail of herbicides in an outdoor experiment.

Primary production (PP) is a key variable to evaluate the quality of the ecological services provided by freshwater bodies because it gives information on the amount of oxygen and organic matter incorporated into the system. We analysed the impact of a mixture of commercial formulations of glyphosate- and 2,4-D-based herbicides (Roundup Max® and AsiMax 50®, respectively) on freshwater primary production. Primary production was studied through the oxygen exchange method. Four measurements were made during a 23-day experiment in outdoor mesocosms using the light and dark bottle method. High and low concentrations of the active ingredients were assayed to evaluate a concentration-dependent effect. Our results indicated that the mixture of Roundup Max® and AsiMax 50® acted mostly additively on gross and net primary production. Moreover, we found a concentration-dependent effect of each herbicide on PP. Thus, AsiMax 50® at low and Roundup Max® at high concentration induced a significant early decrease in respiration and gross primary production 4 h after application, attributable to physiological responses. Besides, significant increases in primary production were simultaneously recorded with increases in chlorophyll a concentration and micro + nano-phytoplankton abundance 7 days after the application of Roundup Max® at high concentration. This study contributes to the knowledge of the impact of widely used herbicides on freshwater ecosystems.