Persulfate activation by biochar and iron: Effect of chloride on formation of reactive species and transformation of N,N-diethyl-m-toluamide (DEET).

Fenton-like processes using persulfate for oxidative water treatment and contaminant removal can be enhanced by the addition of redox-active biochar, which accelerates the reduction of Fe(III) to Fe(II) and increases the yield of reactive species that react with organic contaminants. However, available data on the formation of non-radical or radical species in the biochar/Fe(III)/persulfate system are inconsistent, which limits the evaluation of treatment efficiency and applicability in different water matrices. Based on competition kinetics calculations, we employed different scavengers and probe compounds to systematically evaluate the effect of chloride in presence of organic matter on the formation of major reactive species in the biochar/Fe(III)/persulfate system for the transformation of the model compound N,N­diethyl-m-toluamide (DEET) at pH 2.5. We show that the transformation of methyl phenyl sulfoxide (PMSO) to methyl phenyl sulfone (PMSO2) cannot serve as a reliable indicator for Fe(IV), as previously suggested, because sulfate radicals also induce PMSO2 formation. Although the formation of Fe(IV) cannot be completely excluded, sulfate radicals were identified as the major reactive species in the biochar/Fe(III)/persulfate system in pure water. In the presence of dissolved organic matter, low chloride concentrations (0.1 mM) shifted the major reactive species likely to hydroxyl radicals. Higher chloride concentrations (1 mM), as present in a mining-impacted acidic surface water, resulted in the formation of another reactive species, possibly Cl2•-, and efficient DEET degradation. To tailor the application of this oxidation process, the water matrix must be considered as a decisive factor for reactive species formation and contaminant removal.

A tumor-targeted and enzyme-responsive gold nanorod-based nanoplatform with facilitated endo-lysosomal escape for synergetic photothermal therapy and protein therapy.

To tackle the obstacles related to tumor targeting and overcome the limitations of single treatment models, we have developed a nanoplatform that is both tumor-targeted and enzyme-responsive. This nanoplatform integrates photothermal gold nanorods (AuNRs) and protein drugs into a single system. This nanosystem, known as AuNRs@HA-mPEG-Deta-LA, was fabricated by modifying gold nanorods (AuNRs) with a polymeric ligand called hyaluronic acid-grafted-(mPEG/diethylenetriamine-conjugated-lipoic acid). The purpose of this fabrication was to load cytochrome c (CC) and utilize it for the synergetic protein-photothermal therapy of cancer. The resulting nanoplatform exhibited a high efficiency in loading proteins and demonstrated excellent stability in different biological environments. Additionally, CC-loaded AuNRs@HA-mPEG-Deta-LA not only enabled localized hyperthermia for photothermal therapy (PTT) with laser irradiation but also facilitated the release of CC under the action of hyaluronidase, an enzyme known to be overexpressed in tumor cells. The confocal imaging results demonstrated that the presence of a specific polymeric ligand on this nanoparticle enhances the internalization of CD44-positive cancer cells, accelerates endo/lysosomal escape, and facilitates the controlled release of CC within the cells. Furthermore, the results of the MTT assay also showed that AuNRs@HA-mPEG-Deta-LA as a protein nanocarrier demonstrated excellent biocompatibility. Importantly, this synergistic therapeutic strategy effectively induced apoptosis in A549 cancer cells by increasing the intracellular concentration of CC and utilizing the photothermal conversion of AuNRs, which was observed to be more effective compared to using only protein therapy or PTT. Therefore, this study showcased a nanoplatform based on AuNRs that has great potential for tumor-targeted protein delivery in combination with PTT in cancer treatment.

Poly(oxyethylene)/Poly(oxypropylene) butyl ether prolongs the repellent effect of N,N-diethyl-3-toluamide on the skin.

N,N-diethyl-meta-toluamide (DEET) is a widely used insect repellent, with minimal skin permeation and sustained repellent activity in the superficial layers of the skin. In this study, we prepared a 10% DEET formulation consisting of 40% ethanol with or without 2% poly(oxyethylene)/poly(oxypropylene) butyl ether (POE-POP), an amphiphilic random copolymer. Further, we demonstrated the effects of POE-POP on tensile stress (stickiness), hydrophobicity, skin retention, permeation, and repellent activity of DEET. Stickiness was measured in male ICR mice (7-week old), and skin retention and permeation were evaluated in male Wistar rats (7-week old). In addition, female Aedes albopictus were used to measure the repellent action of DEET. The addition of POE-POP did not affect stickiness, volatility, and degradability but decreased logP and increased viscosity of DEET. Next, we demonstrated the behavior of DEET formulations in the rat skin. POE-POP prolonged the retention of DEET in the superficial layers of the rat skin (skin surface and stratum corneum) and decreased the penetration of DEET into rat skin tissues (epithelium and dermis). The repellent effect of DEET was also enhanced by the addition of POE-POP. However, severe skin damage was not observed after repetitive treatment with DEET formulations containing POE-POP for one month (twice a day). In conclusion, we demonstrated that a 10% DEET formulation consisting of 40% ethanol and 2% POE-POP attenuated the skin penetration and prolonged the repellent action of DEET without causing stickiness and skin damage. We conclude that the combination of ethanol and POE-POP is useful as a safe and effective delivery system for the development of insect repellent formulations containing DEET.

Repellent efficacy of the nanogel containing Acroptilon repens essential oil in comparison with DEET against Anopheles stephensi.

OBJECTIVE: Malaria is a vector-borne disease that causes many deaths worldwide; repellents are a practical approach to malaria prevention, especially in endemic regions. RESULTS: Gas chromatography-mass spectrometry analysis was used to identify compounds in Acroptilon repens essential oil (EO). Alpha-copaene (15.67%), α-cubenen (3.76%), caryophyllene oxide (14.00%), 1-heptadecane (5.61%), and δ-cadinene (2.84) were five major compounds. After that, the nanoemulsion containing the EO with a particle size of 46 ± 4 nm, SPAN 0.85, PDI 0.4, and zeta potential - 5.7 ± 0.4 mV was prepared. Then, it was gellified by adding CMC (carboxymethyl cellulose) to the nanoemulsion. Besides, ATR-FTIR analysis (Attenuated Total Reflection-Fourier Transform InfraRed) was used to confirm the EO's successful loading in the nanogel. Finally, the protection time and repellent activity of nanogel compared to DEET (N, N-diethyl-meta-toluamide) were investigated against Anopheles stephensi. Interestingly, the nanogel with a protection time of 310 ± 45 min was significantly more potent than DEET (160 ± 17 min). It could thus be considered for future investigation against other mosquitoes.

Long-Term Insect Repellent Electrospun Microfibers from Recycled Poly(ethylene terephthalate).

In recent years, there has been an increase in the incidence of insect-borne diseases. Topically applied insect repellents are used to prevent these infectious diseases, but concerns of skin permeability and rapid evaporation rates have made way for alternative preventative methods. Encapsulation of insect repellents in polymeric materials allows for nonskin contact methods of repellent delivery with extended-release profiles without the need for reapplication. Poly(ethylene terephthalate) (PET) is widely used in textiles as well as food packaging and other single-use applications. This short product lifespan makes PET a major environmental pollutant; thus, recycling of PET is of great interest and utility. We report on the fabrication and evaluation of recycled PET microfibers containing N,N-diethyl-meta-toluamide (DEET) and picaridin and the first evaluation of dual repellent loading (DEET/picaridin) via electrospinning. The electrospun microfibers displayed a repellent retention up to 97% within the polymer network upon processing. Release profiles were characterized by isothermal thermogravimetric analysis (TGA). Hansen solubility parameters correlated release profiles with the chemical affinity between PET and the repellent substrate. Insect repellency was assessed against live mosquitoes using a novel bioassay method. Repellency was observed to be as high as 100% for over 1 week and 80% for over 3 weeks. Our method allows for long-lasting repellency with the potential for large-scale textile manufacturing.

Tannic acid-assisted fabrication of antibacterial sodium alginate-based gel beads for the multifunctional adsorption of heavy metal ions and dyes.

The existence of heavy metals and dyes seriously affects the ecological environment and human safety. Antibacterial adsorption materials with the broad-spectrum removal of multiple pollutants are urgently required for water remediation. Herein, a sustainable and antibacterial sodium alginate (SA) gel bead adsorbent with honeycomb cellular architecture is developed by the biomimetic deposition polyphenolic tannic acid (TA) induced grafting diethylenetriamine (DETA) under mild conditions for efficient removal of Cr(VI) and dyes. Taking advantage of the catechol surface chemistry, TA occurring rapid polymerization with DETA monomers not only enhances the water resistance and thermal stability of the gel bead, but also introduces abundant polyphenolic functional groups and active adsorption sites. The multifunctional gel bead showed outstanding antibacterial activity against S. aureus (sterilization rates: 83.8 %) and E. coli (sterilization rates: 99.5 %). The maximum adsorption capacity of gel bead for Cr(VI) was 163.9 mg/g. Moreover, the removal efficiency of the gel bead for dyes of Safranine T and Rhodamine B was 89.5 % (maximum adsorption capacity: 537 mg/g) and 76.7 % (maximum adsorption capacity: 460.2 mg/g), respectively, indicating its excellent broad-spectrum adsorption performance for multiple pollutants. Therefore, TA-assisted fabrication of SA-based gel bead with excellent antibacterial property is a promising multifunctional adsorption material for practical water remediation.

Mosquito Repellent Efficacy of Australian Blue Cypress Callitris intratropica Essential Oil and a Topical Formulation under Laboratory and Field Conditions.

Mosquito repellents are important for personal protection against nuisance and potentially infectious mosquito bites. Repellent activity of Australian blue cypress essential oil (EO) and a commercially formulated skin lotion containing blue cypress EO (topical formulation) were compared with 20% DEET (N, N-diethyl-3 toluamide) against mosquitoes under laboratory and field conditions in North Queensland, Australia. On a volunteer's forearm, 1 mL of candidate material was applied to approximately 600 cm2 of exposed skin. When blue cypress EO was applied at various concentrations (0.5%-10.5%), it did not fully prevent mosquito landing or biting. However, a dose-dependent increase, approaching 80% protection, was observed at high EO concentrations. On the basis of these results, three concentrations (5%, 10%, and 20%) of blue cypress EO were selected for complete protection time (CPT) experiments. Topical formulation (undiluted) was also included in CPT experiments. Although some protection was afforded, mosquito landing/probing were still recorded immediately after application for both blue cypress EO and its topical formulation. Specifically, protection declined for blue cypress EO from 80% to 70% (laboratory) and from 93% to 50% (field) within 1 hour. For topical formulation, protection declined from 85% to 75% in the laboratory and from 63% to 50% in the field. In comparison, DEET maintained a 100% protection throughout the testing period of up to 1 h, and there was no landing/probing observed in volunteers who had applied DEET. To conclude, both blue cypress products provided some protection against mosquito bites, which decreased soon after application.

Combining chemical, bioanalytical and predictive tools to assess persistence, seasonality, and sporadic releases of organic micropollutants within the urban water cycle.

Using a novel liquid chromatography-tandem mass spectrometry method with large volume direct injection and quantitation via isotope dilution, we evaluated the presence of 55 organic micropollutants in wastewater effluents, and locations within the Bow River and Elbow River watersheds in and around the city of Calgary, Alberta, Canada. In addition to establishing baseline micropollutant data for water utility operations, our study aimed to enhance our understanding of micropollutant behavior in the urban water cycle, assess the contributions of three wastewater treatment plants (WWTPs) to downstream receiving waters, explain the potential causes of total estrogenicity measured using the yeast-estrogen screen assay (YES), and prioritize a subset of substances for continuous monitoring. With data spanning 48 months and 95 river km, our results indicate the extensive persistence of metformin (antidiabetic), seasonality of N,N­diethyl-m-toluamide (DEET, insect repellant), O-desmethylvenlafaxine (antidepressant metabolite), and sulfamethoxazole (antibiotic) in source waters, and sporadic detections of a well-known perfluoroalkyl substance (PFOA). The seasonality of pharmaceuticals at the sentinel downstream monitoring site appeared to coincide with river dilution while that of DEET was likely attributable to peak usage during the warmer months. Steroidal estrogens were rarely detected in wastewater effluents although total estrogenicity via YES was evident, suggesting the presence of less potent but more abundant non-steroidal estrogens (e.g., flame retardants, bisphenols, and phthalates). A conservative mass balance analysis suggests that the largest WWTP (serving a population of >1 million) consistently contributed the highest load of micropollutants, with the exception of metformin, which appeared to be influenced by a smaller WWTP (serving 115,000) that operates a different activated sludge process. We consider metformin, sucralose, diclofenac, and venlafaxine as more effective conservative tracers of wastewater pollution due to their notably higher concentrations and persistence in the Bow River compared to carbamazepine and caffeine, respectively. Finally, hierarchical clustering revealed a close association between E. coli and caffeine, supporting the use of caffeine as an indicator of short-term, untreated anthropogenic inputs. Overall, this study yields valuable insights on the presence, behavior, and sources of organic micropollutants in the urban water cycle and identifies indicators of anthropogenic impacts that are useful for prioritizing future monitoring campaigns in Calgary and elsewhere.

Comparative study on removal of platinum cytostatic drugs at trace level by cysteine, diethylenetriamino functionalized Si-gels and polyethyleneimine functionalized sponge: Adsorption performance and mechanisms.

To efficiently remove trace Pt-based cytostatic drugs (Pt-CDs) from aqueous environments, a comparative investigation was conducted on the adsorption behavior of three commercial adsorbents including cysteine-functionalized silica gel (Si-Cys), 3-(diethylenetriamino) propyl-functionalized silica gel (Si-DETA) and open-celled cellulose MetalZorb® sponge (Sponge). The research on the adsorption of cisplatin and carboplatin encompasses investigations of pH dependence, adsorption kinetics, adsorption isotherms, and adsorption thermodynamics. The obtained results were compared with those of PtCl42- to better understand the adsorption mechanisms. The adsorption of cisplatin and carboplatin by Si-Cys was significantly better than Si-DETA and Sponge, which suggested that in chelation-dominated chemisorption, thiol groups provided high-affinity sites for Pt(II) complexation. Adsorption of the anion PtCl42- was more pH dependent and generally superior to that of cisplatin and carboplatin, benefiting from the contribution of ion association with protonated surfaces. The removal process of aqueous Pt(II) compounds occurred by the hydrolysis of complexes in solution and subsequent adsorption, and the specific adsorption process was explained by the synergistic action of ion association and chelation mechanisms. The rapid adsorption processes involving diffusion and chemisorption were well described by pseudo-second-order kinetic model. The isotherm studies suggested monolayer adsorption, consistent with the Langmuir model. Indicated from the adsorption enthalpy results, the chelation of cisplatin and carboplatin with thiol groups was an endothermic reaction, while the adsorption of PtCl42- was exothermic. At 343 K, Si-Cys achieved 98.5 ± 0.1 % (cisplatin) and 94.1 ± 0.1 % (carboplatin) removal. To validate the obtained findings, the described process was applied to urine samples doped with Pt-CDs as analog of hospital wastewaters and the removal was very efficient, ranging from 72 ± 1 % to 95 ± 1 %, when using Si-Cys as adsorbent, although limited matrix effects were observed.

Cation-free siRNA-cored nanocapsules for tumor-targeted RNAi therapy.

Cation-associated cytotoxicity limits the systemic administration of RNA delivery in vivo, demanding the development of non-cationic nanosystems. In this study, cation-free polymer-siRNA nanocapsules with disulfide-crosslinked interlayer, namely T-SS(-), were prepared via the following steps: 1) complexation of siRNA with a cationic block polymer cRGD-poly(ethylene glycol)-b-poly[(2-aminoethanethiol)aspartamide]-b-poly{N'-[N-(2-aminoethyl)-2-ethylimino-1-aminomethyl]aspartamide}, abbreviated as cRGD-PEG-PAsp(MEA)-PAsp(C=N-DETA), 2) interlayer crosslinking via disulfide bond in pH 7.4 solution, and 3) removal of cationic DETA pendant at pH 5.0 via breakage of imide bond. The cationic-free nanocapsules with siRNA cores not only showed great performance (such as efficient siRNA encapsulation, high stability in serum, cancer cell targeting via cRGD modification, and GSH-triggered siRNA release), but also achieved tumor-targeted gene silencing in vivo. Moreover, the nanocapsules loaded with siRNA against polo-like kinase 1 (siRNA-PLK1) significantly inhibited tumor growth without showing cation-associated toxicity side effects and remarkably improved the survival rate of PC-3 tumor-bearing mice. The cation-free nanocapsules could potentially serve as a safe and effective platform for siRNA delivery. STATEMENT OF SIGNIFICANCE: Cation-associated toxicity limits the clinical translation of cationic carriers for siRNA delivery. Recently, several non-cationic carriers, such as siRNA micelles, DNA-based nanogels, and bottlebrush-architectured poly(ethylene glycol), have been developed to deliver siRNA. However, in these designs, siRNA as a hydrophilic macromolecule was attached to the nanoparticle surface instead of being encapsulated. Thus, it was easily degraded by serum nuclease and often induced immunogenicity. Herein, we demonstrate a new type of cation-free siRNA-cored polymeric nanocapsules. The developed nanocapsules not only showed capacities including efficient siRNA encapsulation, high stability in serum, and cancer cell targeting via cRGD modification, but also achieved an efficient tumor-targeted gene silencing in vivo. Importantly, unlike cationic carriers, the nanocapsules exhibited no cation-associated side effects.

Deep oxidative desulfurization of simulated and real gas oils by NiFe2O4@SiO2-DETA@POM as a retrievable hybrid nanocatalyst.

Magnetic nanoparticles surrounded with a silica shell are useful materials to immobilize active agents on their surface. Here, a heteropolyacid-functionalized hybrid nanomaterial (NiFe2O4@SiO2-DETA@POM) was prepared and characterized by X-ray powder diffraction patterns (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA/DTG), vibrating sample magnetometer (VSM), the field emission scanning electron microscopy (FE-SEM), and the electron-dispersive X-ray spectroscopy (EDS). The synthesized hybrid nanostructure was used as a solid nanocatalyst in oxidative desulfurization (ODS) of real fuel and simulated gasoline samples. The ODS process of benzothiophene (BT) and dibenzothiophene (DBT) as model compounds in the presence of NiFe2O4@SiO2-DETA@POM and by using urea-hydrogen peroxide/acetic acid as a safer oxidizing agent was investigated. A good result was obtained by removing 97% of benzothiophene and 98% of dibenzothiophene. Also, 96% of the sulfur compounds were eliminated when the ODS process was tested on a real crude oil sample (600 ppm) under an optimized dosage of nanocatalyst, urea-hydrogen peroxide/acetic acid (0.1 g, 1 g/4 ml) at 50 ºC for 60 min. NiFe2O4@SiO2-DETA@POM could be recycled for five consecutive oxidation runs without significant deterioration in its catalytic activity. The UHP's safety and efficiency as an oxidant, high removal efficacy, short transformation times, easy workup procedure, catalyst reusability, simple separation of nanocatalyst, green conditions, and environmental compatibility and sustainability. The obtained results prove that NiFe2O4@SiO2-DETA@POM is a suitable and efficient hybrid catalyst for the oxidative desulfurization of simulated and real fuels.

Screening of pesticides and emerging contaminants in eighteen Greek lakes by using target and non-target HRMS approaches: Occurrence and ecological risk assessment.

Lakes, albeit ecosystems of vital importance, are insufficiently investigated with respect to the degradation of water quality due to the organic micropollutants load. As regards Greece, screening of lake waters is scarce and concerns a limited number of contaminants. However, understanding the occurrence of contaminants of emerging concern (CECs) and other micropollutants in lakes is essential to appraise their potential ecotoxicological effects. The aim of this study was to deploy a multiresidue screening approach based on liquid chromatography-high-resolution mass spectrometry (HRMS) to get a first snapshot for >470 target CECs, including pesticides, pharmaceuticals, personal care products (PPCPs), per- and polyfluoroalkyl substances (PFASs), as well as organophosphate flame retardants (OPFRs) in eighteen Greek lakes in Central, Northern and West Northern Greece. The omnipresent compounds were DEET (N,N-diethyl-meta-toluamide), caffeine and TCPP (tris (1-chloro-2-propyl) phosphate). Maximum concentrations varied among the different classes. DEET was detected at a maximum average concentration of >1000 ng/L in Lake Orestiada, while its mean concentration was estimated at 233 ng/L. The maximum total concentrations for pesticides, PPCPs, PFASs, and OPFRs were 5807, 2669, 33.1, and 1214 ng/L, respectively, indicating that Greek lakes are still threatened by the intense agricultural activity. Besides, HRMS enabled a non-target screening by exploiting the rich content of the full-scan raw data, allowing the 'discovery' of tentative candidates, such as surfactants, pharmaceuticals, and preservatives among others, without reference standards. The potential ecotoxicity was assessed by both the risk quotient method and ECOSAR (Ecological Structure Activity Relationships) revealing low risk for most of the compounds.

Scavenging of hexavalent chromium from aqueous solution by Macadamia nutshell biomass modified with diethylenetriamine and maleic anhydride.

Based on the premise that aqueous anions of hexavalent chromium (Cr(VI)) are capable of electrostatic interaction with cationic and polar active sites, acid-washed Madacamia nutshell biomass was sequentially treated with diethylenetriamine (DETA) and maleic anhydride (MA) to graft poly(diethylenetriamine-co-maleic anhydride). By displaying a new peak at 1685 cm-1 ascribed to amide CO stretching vibrations, Fourier transform infrared spectroscopy highlighted the formation of amide groups through reaction of DETA with carboxyl groups on the biomass surface. Scanning electron microscopic images of the MA-modified biomass displayed polymeric growths attributed to copolymerization of DETA with MA. The polar and ionizable amide and amine groups of the grafted copolymer endowed the adsorbent with Cr(VI) removal capabilities over a wide pH range demonstrated by removal efficiencies between 70.9% and 81.7% in the pH 1.6 to pH 10.0 range for the treatment of 20 mL solutions containing 100 mg L-1 Cr(VI) with 200 mg of adsorbent. Conformity of the adsorption isotherm data to the Freundlich model revealed the heterogeneous nature of the adsorbent surface, which comprised a variety of functional groups capable of interaction with Cr(VI) species in solution. The Sips isotherm model provided the best fit to the equilibrium experimental data, and the adsorption capacity was 779.1 mg g-1 at pH 1.6, room temperature and an adsorbent dosage of 5.0 g L-1. The findings indicate that Cr(VI) adsorption onto diethylenetriamine and maleic anhydride modified Madacamia nutshell biomass is a promising option for Cr(VI) removal from aqueous solutions.

Mosquito Repellent Potential of Carpesium abrotanoides Essential Oil and Its Main Components Against a Dengue Vector, Aedes aegypti (Diptera: Culicidae).

Disease vectoring mosquitoes are a serious threat to humans. However, till today only few mosquito repellents have been identified. The current study was conducted to evaluate the repellent potential of Carpesium abrotanoides essential oil against Aedes aegypti females by human bait technique. Essential oil was extracted by steam distillation process while the identification of chemical constituents was carried out by gas chromatography-mass spectrometry. Time span repellent bioassays of C. abrotanoides essential oil in comparison to DEET were performed at three different doses (33 µg/cm2, 165 µg/cm2, and 330 µg/cm2) under laboratory conditions. Highest repellency periods for essential oil and DEET were observed at the tested dose of 330 µg/cm2 with 315 min and 720 min, respectively. Lowest repellency period of 45 min for essential oil and 105 min for DEET was recorded at the tested dose of 33 µg/cm2. Major constituents caryophyllene (24.3%) and trans-nerolidol (12.0%) of C. abrotanoides essential oil were also evaluated as repellents at three different doses (330 µg/cm2, 165 µg/cm2, and 33 µg/cm2) against Ae. aegypti. Surprisingly, trans-nerolidol completely inhibited Ae. aegypti landings for 45 min when tested at 330 µg/cm2. However, caryophyllene did not completely inhibit Ae. aegypti landing even after immediate application at the tested dose of 330 µg/cm2. At the tested dose of 330 µg/cm2, the mixture (trans-nerolidol + caryophyllene) completely inhibited Ae. aegypti landing for 60 min indicating the synergistic effect of caryophyllene. Hence, C. abrotanoides as well as its major constituent, especially trans-nerolidol, have potential to formulate as mosquito repellent comparable of DEET.

Toxicity and Repellency of Magnolia grandiflora Seed Essential Oil and Selected Pure Compounds Against the Workers of Hybrid Imported Fire Ants (Hymenoptera: Formicidae).

We tested Magnolia grandiflora L. (Magnoliales: Magnoliaceae) seed essential oil and its pure compounds for their repellency and toxicity against workers of hybrid imported fire ants. Series of dosages were tested starting from 156 µg/g to the dose where the treatment failed. Workers removed significantly less sand from the vials with M. grandiflora seed essential oil and 1-octanol treated sand at serial dosages of 156-4.9 µg/g than the solvent control whereas the amount removed at 2.4-0.6 µg/g was similar to the solvent control. In 1-decanol treatments, workers removed significantly less sand at serial dosages of 156-0.15 µg/g than the solvent control whereas the removal of sand at the dose of 0.08 µg/g was similar to the solvent control. In DEET (N, N-diethyl-meta-toluamide) treatments, workers removed significantly less sand at serial dosages of 156-78 µg/g than the solvent control whereas the quantity of removed sand at 39 µg/g was similar to the solvent control. Based on the mean amount of sand removed, M. grandiflora essential oil, 1-decanol, and 1-octanol showed significantly higher repellency than DEET. 1-Decanol and 1-octanol, present in seed essential oil showed toxicity against fire ant workers. 1-Decanol with LC50 of 140.6 µg/g was the most toxic natural compound followed by 1-octanol (LC50 = 486.8 µg/g). Bifenthrin with LC50 value of 0.018 µg/g showed much higher toxicity than these natural compounds. High repellency and toxicity of 1-decanol makes it a natural compound of interest for further studies under field conditions.

Highly efficient removal of DEET by UV-LED irradiation in the presence of iron-containing coagulant.

N,N-Diethyl-3-methyl benzoyl amide (DEET) has been detected as an emerging pollutant in various water bodies because of its widespread use as an insect repellent. In this study, the combination of UV-LED275 and iron-containing coagulant (FeCl3) was used for the elimination of DEET in water. It was found that UV-LED275/FeCl3 (98 %) system presented a favorable removal of DEET compared with UV254/FeCl3 (59 %) and UV-LED275/Fe2(SO4)3 (81 %) processes at initial pH 3.5. DEET degradation by both UV-LED275/FeCl3 and UV-LED275/Fe2(SO4)3 processes followed pseudo-first-order kinetics with the calculated pseudo-first-order rate constants (kobs) of 0.0105 and 0.0046 cm2 mJ-1, respectively. The results of ESR analysis and radicals quenching experiments indicated that hydroxyl radicals (OH) and superoxide radicals (O2-) were responsible for DEET degradation in UV-LED275/FeCl3 process, and the former played the major role. An increase in FeCl3 dosage was beneficial to the degradation. In the UV-LED275/FeCl3 process, DEET degradation increased with a decrease in pH from 3.5 to 3.0, whereas it was almost completely suppressed with an increase in pH from 4.3 to 6.3. DEET degradation was almost unchanged after the introduction of NO3-, and it impeded after the addition of humic acid (HA), HCO3-, and SO42-. The plausible degradation pathway mainly involved hydroxylation, cleavage of the C-N bond, acetylation, and dealkylation. Among the disinfection by-products (DBPs) evaluated, UV-LED275/FeCl3 pretreatment generally increased the generation of trichloromethane, chloral hydrate, dichloroacetic acid, and trichloroacetic acid, which implied that further assessment of environmental risk was needed during its practical applications.

Novel ß-Cyclodextrin and Catnip Essential Oil Inclusion Complex and Its Tick Repellent Properties.

Cyclodextrin inclusion complexes have been successfully used to encapsulate essential oils, improving their physicochemical properties and pharmacological effects. Besides being well-known for its effects on cats and other felines, catnip (Nepeta cataria) essential oil demonstrates repellency against blood-feeding pests such as mosquitoes. This study evaluates the tick repellency of catnip oil alone and encapsulated in ß-cyclodextrin, prepared using the co-precipitation method at a 1:1 molar ratio. The physicochemical properties of this inclusion complex were characterized using GC-FID for encapsulation efficiency and yield and SPME/GC-MS for volatile emission. Qualitative assessment of complex formation was done by UV-Vis, FT-IR, 1H NMR, and SEM analyses. Catnip oil at 5% (v/v) demonstrated significant tick repellency over time, being comparable to DEET as used in commercial products. The prepared [catnip: ß-CD] inclusion complex exerted significant tick repellency at lower concentration of the essential oil (equivalent of 1% v/v). The inclusion complex showed that the release of the active ingredient was consistent after 6 h, which could improve the effective repellent duration. These results demonstrated the effective tick repellent activity of catnip essential oil and the successful synthesis of the inclusion complex, suggesting that ß-CDs are promising carriers to improve catnip oil properties and to expand its use in repellent formulations for tick management.

Pyridostigmine bromide, chlorpyrifos, and DEET combined Gulf War exposure insult depresses mitochondrial function in neuroblastoma cells.

Gulf War Illness (GWI) is defined by the Centers for Disease Control and Prevention (CDC) as a multi-symptom illness having at least one symptom from two of three factors, which include: fatigue, mood-cognition problems, and musculoskeletal disorders. The cluster of long-term symptoms is unique to military personnel from coalition countries including United States, Australia, and the United Kingdom that served in Operation Desert Storm from 1990 to 1991. Reporting of these symptoms is much lower among soldiers deployed in other parts of the world like Bosnia during the same time period. The exact cause of GWI is unknown, but combined exposure to N,N-diethyl-m-toluamide (DEET), organophosphates like chlorpyrifos (CPF), and pyridostigmine bromide (PB), has been hypothesized as a potential mechanism. Mitochondrial dysfunction is known to occur in most neurodegenerative diseases that share symptoms with GWI and has therefore been implicated in GWI. Although exposure to these and other toxicants continues to be investigated as potential causes of GWI, their combined impact on mitochondrial physiology remains unknown. In this study, the effects of combined GWI toxicant exposure on mitochondrial function were determined in a commonly used and readily available immortalized cell line (N2a), whose higher rate of oxygen consumption resembles that of highly metabolic neurons in vivo. We report that combined exposure containing pesticide CPF 71 µM, insect repellants DEET 78 µM, and antitoxins PB 19 µM, causes profound mitochondrial dysfunction after a 4-h incubation resulting in decreased mitochondrial respiratory states in the absence of proapoptotic signaling, proton leak, or significant increase in reactive oxygen species production.

A new colorimetric DET technique for determining mm-resolution sulfide porewater distributions and allowing improved interpretation of iron(II) co-distributions.

Measurement of sulfide in pore waters is critical for understanding biogeochemical processes, especially within coastal sediments. Here we report the development of a new colorimetric DET (diffusive equilibration in thin films) technique for determining mm-resolution, two-dimensional sulfide distributions in sediment pore waters. This colorimetric sulfide DET method was based on the standard spectrophotometric methylene blue assay, but modified to allow quantitation of sulfide by computer imaging densitometry. The method detection and effective upper measurement limits of the optimised technique were 3.7 and 1000 µmol L-1, respectively. The optimised sulfide DET method was combined with the colorimetric iron(II) DET method to obtain co-distributions in coastal seagrass (Zostera muelleri) colonised sediment under light and dark conditions. In the dark, seagrass sediments were more reduced than in the light, with large areas being dominated by high porewater sulfide concentrations. These co-distributions were compared with those obtained using the previously described DET-DGT (diffusive gradients in thin films) method for measuring iron(II) and sulfide co-distributions. There was less overlap of iron(II) and sulfide distributions using the sulfide DET as the two DET methods are influenced most by the later hours of deployment, whereas the sulfide-DGT measurement integrates concentrations over the whole deployment period. Overlap was most apparent in very dynamic sediment zones, such as burrow wall sediments.

Investigação do comportamento de tolerância ao N, N- dietilmetilbenzamida (DEET) em populações de Aedes aegypti (Diptera: Culicidae) / Investigation of tolerance behavior to N, N-diethylmethylbenzamide (DEET) in populations of Aedes aegypti (Diptera: Culicidae)

Aedes aegypti é um mosquito de grande interesse para saúde pública, pois é o vetor de arbovírus, como dengue, chikungunya e Zika. Para o controle desse vetor, são utilizados o controle biológico, mecânico e o controle químico, com utilização de inseticidas e repelentes. Os repelentes são considerados uma das melhores formas de se evitar as picadas das fêmeas, sendo os mais comercializados aqueles que possuem N,N-dietilmetilbenzamida (DEET) na fórmula, além de serem um dos mais estudados atualmente. Entretanto a resitência a alguns inseticidas como o piretroide, pode levar à alteração na atividade locomotora dos mosquitos. Deste modo, o presente trabalho tem como objetivo avaliar aspectos relacionados à tolerância ao DEET e à resistência a xenobióticos em cepas Ae. aegypti de campo (Laranjeiras) e de laboratório (Rockefeller). Foram realizados testes de repelência com Ae. aegypti para a resposta ao odor humano. Em cada teste, foram utilizadas 50 fêmeas, totalizando 700 fêmeas da população Laranjeiras e 1500 fêmeas para a população Rockefeller. As fêmeas foram colocadas em gaiolas de teste por cerca de duas horas, a fim de se adaptarem ao ambiente. Posteriormente, foi realizado o teste de repelência, que consistiu na exposição do mosquito a 0,5 mL de DEET (10% em etanol), este foi aplicado uniformemente pelo antebraço humano. Para diagnosticar a presença da mutação kdr na população de Laranjeiras foram analisadas 32 fêmeas dessa população. Para avaliar a atividade locomotora das fêmeas de Ae. aegypti Rockefeller e de Laranjeiras, foi utilizado o Drosophila Activity Monitor - Trikinetics. No período de setembro a novembro de 2019, foram instaladas 290 ovitrampas no município de Laranjeiras - SE, tendo sido verificado um total de 80,3% de palhetas com presença de ovos de Aedes, contabilizando 15.940 ovos. Após a realização dos bioensaios, foi possivel observar maior sensibilidade ao DEET nas fêmeas provinientes do campo. Além disso, também foi possivel observar a presença da mutação kdr e uma maior atividade locomotora nessa população. Dessa forma, nossos resultados sugerem que mosquitos resistentes podem ser mais suceptíveis ao DEET.

Aedes aegypti is a mosquito of great interest for public health, as it is the vector of arboviruses, such as dengue, chikungunya and Zika. Biological, mechanical and chemical control, with the use of insecticides and repellents, are used against this vector. Repellents are considered one of the best ways to avoid female bites, being those that have N, N-diethylmethylbenzamide (DEET) in the formula the most commercialized, as well as the most studied today. However, resistance to some insecticides such as pyrethroid, can lead to changes in the locomotor activity of mosquitoes. Thus, this study aims to evaluate aspects related to DEET tolerance and resistance to xenobiotics in field Ae. aegypti (Laranjeiras) and laboratory (Rockefeller) strains. Repellency tests were performed with Ae. aegypti for the response to human odor. In each test, 50 females were used, totaling 700 females from the Laranjeiras population and 1500 females from the Rockefeller population. The females were placed in test cages for about two hours in order to adapt to the environment. Subsequently, the repellency test was performed, which consisted of exposing the mosquito to 0.5 mL of DEET (10% in ethanol), which was applied evenly to the human forearm. To diagnose the presence of the kdr mutation in the population of Laranjeiras, 32 females from that population were analyzed. To evaluate the locomotor activity of Ae. aegypti Rockefeller and Laranjeiras females,, the Drosophila Activity Monitor - Trikinetics was used. In the period from September to November 2019, 290 ovitraps were installed in the municipality of Laranjeiras - SE, with a total of 80.3% of reeds with the presence of Aedes eggs, accounting for 15,940 eggs. After conducting the bioassays, it was possible to observe greater sensitivity to DEET in females from the field. In addition, it was also possible to observe the presence of the kdr mutation and greater locomotor activity in this population. Thus, our results suggest that resistant mosquitoes may be more susceptible to DEET.