Quaternary ammonium compounds (QACs): a review on occurrence, fate and toxicity in the environment

Chemical composition-dependent removal of cationic surfactants by carbon nanotubes

How to attenuate water surfactant pollution using carbon nanomaterials (CNMs) has been gaining increasing research attention in recent years. However, how the composition of cationic surfactants and physicochemical properties of CNMs may affect cationic surfactant maximum removal efficiency (R_{efficiency-max}) with minimal cost from the aqueous phase and the associated mechanisms remain largely unclear. To address this knowledge gap, we compared removal efficiency of three cationic surfactants including dodecyl dimethyl benzyl ammonium chloride (DDBAC), tetradecyl dimethyl benzyl ammonium chloride (TDBAC) and hexadecyltrimethylammonium bromide (CTAB) by various carbon nanotubes (CNTs), including pristine and OH- or COOH-functionalized multiwalled- (MWCNTs) and single-walled (SWCNTs) CNTs. The results showed that R_{efficiency-max} of CTAB by pristine MWCNTs with an outer diameter OD < 8 nm is 50.36 ± 0.56%, while that by OH-MWCNTs with OD < 8 nm is merely 22.72 ± 0.21%. Surface area and porosity of CNTs strongly affect R_{efficiency-max} of cationic surfactants. The MWCNTs with a smaller OD have a higher R_{efficiency-max} than that with a larger one especially for CTAB, due to their larger surface area and porosity. Among various CNTs, SWCNTs is an ideal choice for removing cationic surfactants, especially for non-aromatic CTAB. Interestingly, for most cases, cationic surfactant removal by CNTs decreased when the amount of CNTs added exceeded a certain level, attributable to their aggregation. This implies that it is impossible to completely remove some cationic surfactants even when excess CNTs were added. The π-π bonding dominates over hydrophobic interaction in regulating cationic surfactant removal especially for those with aromatic structure. Aromatic cationic surfactants such as DDBAC and TDBAC can be removed more readily by CNTs than those without a benzene ring due to their strong π-π interactions. TDBAC has a longer hydrophobic chain relative to DDBAC, leading to a better removal efficiency by CNTs, due to stronger hydrophobic interaction.

Benzalkonium ion sorption to peat and clays: Relative contributions of ion exchange and van der Waals interactions

Due to their use in various domestic and industrial formulations, benzalkonium compounds have been isolated in many environmental matrices. Sorption to soil components has been shown to play a key role in their environmental fate. Whereas sorption of benzalkonium compounds to soils is attributed to cation exchange and van der Waals forces, the relative contributions of these two mechanisms at environmental levels have not been clearly defined. In this study a previously reported algal toxicity assay-based method was employed to determine the distribution coefficients (K_d) of benzalkonium compounds between water and soil components, at environmental concentrations. Cation exchange capacity corrected K_d values for organic matter and clays were all within one order of magnitude. This implies that ion exchange is the dominant mechanism of sorption for benzalkonium compounds. When the sorption data were used to compute sorption energies for four homologues of benzalkonium ions, the magnitude of the free energy change of sorption increased with size of the molecule. The increase in sorption energy could be partly explained by increased energy of hydration with addition of methylene groups to the alkyl chain. A model that predicts sorption coefficients of benzalkonium compounds to soils using organic carbon content and cation exchange capacity was also defined. When tested using an artificial soil, the model estimates were all within one order of magnitude of the experimental values.

Enhanced Extraction of AFFF-Associated PFASs from Source Zone Soils

Poly- and perfluoroalkyl substances (PFASs) derived from aqueous film-forming foam (AFFF) are increasingly recognized as groundwater contaminants, though the composition and distribution of AFFF-derived PFASs associated with soils and subsurface sediments remain largely unknown. This is particularly true for zwitterionic and cationic PFASs, which may be incompletely extracted from subsurface solids by analytical methods developed for anionic PFASs. Therefore, a method involving sequential basic and acidic methanol extractions was developed and evaluated for recovery of anionic, cationic, and zwitterionic PFASs from field-collected, AFFF-impacted soils. The method was validated by spike-recovery experiments with equilibrated soil-water-AFFF and analytical standards. To determine the relative importance of PFASs lacking commercially available analytical standards, their concentrations were estimated by a novel semiquantitation approach. Total PFAS concentrations determined by semiquantitation were compared with concentrations determined by the total oxidizable precursor assay. Finally, the described method was applied to two soil cores from former fire-training areas in which cations and zwitterions were found to contribute up to 97% of the total PFAS mass. This result demonstrates the need for extraction and analysis methods, such as the ones presented here, that are capable of quantifying cationic and zwitterionic PFASs in AFFF-impacted source zone soils.

Distance-based paper device using polydiacetylene liposome as a chromogenic substance for rapid and in-field analysis of quaternary ammonium compounds

This work presents an affordable distance-based microfluidic paper-based device (μPAD), using polydiacetylene (PDA) liposome as a chromogenic substance with a smartphone-based photo editor, for rapid and in-field analysis of quaternary ammonium compounds (QACs) (e.g., didecyldimethylammonium chloride (DDAC), benzyldimethyltetradecyl ammonium chloride (BAC), and cetylpyridinium chloride (CPC)). In-field analysis of these compounds is important to ensure their antimicrobial activity and user safety since they are widely utilized as disinfectants in households and hospitals. The μPAD featured a thermometer-like shape consisting of a sample reservoir and a microchannel as the detection zone, which was pre-deposited with PDA liposome. The color change from blue to red appeared in the presence of QACs and the color bar lengths were proportional to the QAC concentrations. Reactions of QACs with the PDA required a specific pH range (from pH 4.0 to 10.0) and a readout time of 7 min. Analytical performance characteristics of the device were tested with DDAC, BAC, and CPC showing acceptable specificity, accuracy (96.1-109.4%), and precision (%RSDs ≤ 9.3%). Limits of detection and quantitation were in the ranges of 20 to 80 and 70 to 250 μM, respectively. Feasibility of the newly developed device was demonstrated for in-field analysis of QACs in fumigation solution providing comparable results with those obtained from a colorimetric assay (P > 0.05). The proposed device shows potentials for further applications of other analytes since it offers speed, simplicity, and affordability for in-field analysis, especially in remote areas where expertise, resources, and infrastructures are limited. Graphical abstract.

Solidago virgaurea L. Plant Extract Targeted Against Candida albicans to Reduce Oral Microbial Biomass: a Double Blind Randomized Trial on Healthy Adults

Oral microbiome plays an important part on oral health and endogenous bacteria and fungi should not be eradicated. However, their proliferation must be controlled by oral hygiene care. In vitro, Solidago virgaurea ssp. virgaurea L. (SV) plant extract inhibits the adherence and hyphal formation of a fungus, Candida albicans. It reduces the biomass of Candida-bacterial biofilms but not fungal or bacterial growth. Unlike chemical antiseptics, like triclosan and chlorhexidine for instance, SV is a plant extract easily biodegradable. The purpose of this study was to assess the in vivo effectiveness of SV extract in reducing oral biomass. A randomized, double-blind clinical study, with dental plaque evaluation designed to assess the effectiveness of a fluorinated toothpaste containing SV (Bucovia™, Givaudan, Vernier, Switzerland) was conducted. Sixty-six subjects (SV group n = 33 vs. control n = 33) brushed their teeth twice a day for a 4-week period. Supragingival dental plaque was sampled. Total bacterial load (broad spectral bacterial quantitative Polymerase Chain Reaction (qPCR)), C. albicans and seven bacterial species were quantified by qPCR. In the Intervention group, there was a decrease of Total bacterial load (ΔD0D28 p = 0.005 and ΔD14D28 p = 0.026), Streptococcus mutans (ΔD0D14 p = 0.024) and C. albicans (ΔD0D28 p = 0.022). In the Control group Total bacterial load tended to decrease from baseline to day 28 (ΔD0D28 p = 0.062 and ΔD14D28 p = 0.009). Plaque Index and Gingival Index improved in both groups.

Antifogging/Antibacterial Coatings Constructed by N-Hydroxyethylacrylamide and Quaternary Ammonium-Containing Copolymers

Endoscopic surgery has gained widespread applications in various clinical departments, and endoscope surfaces with antifogging and antibacterial properties are essential for elaborate procedures. In this work, novel antifogging/antibacterial coatings were developed from a cationic copolymer and a hydrophilic copolymer, polyhedral oligomeric silsesquioxane-poly(quaternary ammonium compound-co-2-aminoethyl methacrylate hydrochloride) [POSS-P(QAC-co-AEMA)] and poly(N-hydroxyethylacrylamide-co-glycidyl methacrylate) [P(HEAA-co-GMA)] via a facile and green blending method. Such transparent coatings showed excellent antifogging performance under both in vitro and in vivo fogging conditions, mainly attributed to the high water-absorbing capability of HEAA and QAC. Antibacterial assays proved that the blending coatings had a superior antibacterial property, which could be improved with the proportion of POSS-P(QAC-co-AEMA) because of the bactericidal efficiency of cationic QAC. Meanwhile, owing to the high hydratability of HEAA, the blending coatings exhibited a bacteria-repelling property. By simply tuning the blending ratio of POSS-P(QAC-co-AEMA) and P(HEAA-co-GMA), the comprehensive bacteria-killing and bacteria-repelling properties of the coatings were achieved. Moreover, after incubating with red blood cells, the prepared blending coatings presented a lower hemolytic rate of less than 5%. The findings provided a potential means for addressing the challenge of fogging and bacterial contamination occurring in endoscopic lenses and other medical devices.

Comprehensive screening of quaternary ammonium surfactants and ionic liquids in wastewater effluents and lake sediments

Quaternary ammonium compounds (QACs) are widely applied as surfactants and biocides in cleaning and personal-care products. Because of incomplete removal during wastewater treatment, QACs are present in wastewater effluents, with which they are discharged into natural waters, where they accumulate in sediments. To assess the levels of QACs in aquatic environments, a liquid chromatography high-resolution mass spectrometry method using both target and suspect screening was developed. The water and sediment sample preparation, measurement, and data analysis workflow were optimized for 22 target compounds with a wide range of hydrophobicity, including ionic liquids that have potential use as solvents and QACs common in personal-care and sanitizing products. In wastewater effluents, average concentrations of all target and suspect QACs combined ranged from 0.4 μg L-1 to 6.6 μg L-1. Various homologs of benzylalkyldimethylammonium (BAC) and dialkyldimethylammonium (DADMAC) as well as the ionic liquid butylpyridinium and 15 suspect QACs were detected in at least one wastewater effluent sample. A spatial profile of sediment samples in a lake demonstrated potential inputs from both municipal wastewater effluent and agricultural sources for BACs. In sediment cores, two distinct trends of temporal QAC accumulation were observed. In lakes with large watersheds and mixed domestic and industrial wastewater sources (Lake Pepin and Duluth Harbor), peak concentrations of QACs were found at depths corresponding to deposition in the 1980s and decreases after this time are attributed to improved wastewater treatment and source control. In a smaller lake with predominantly domestic wastewater inputs (Lake Winona), concentrations of QACs increased slowly over time until today.

Fitness costs associated with carriage of a large staphylococcal plasmid are reduced by subinhibitory concentrations of antiseptics

Staphylococcus aureus carries a collection of mobile genetic elements that often harbor virulence and antimicrobial resistance genes. Since the introduction of antibiotics, plasmids have become a major genetic element responsible for the distribution of antimicrobial resistance. Under antimicrobial selection, resistance plasmids are maintained within bacterial populations as a means to ensure survival. However, in the absence of selection, large plasmids can be lost due to the fitness costs associated with harboring these genetic elements. pC02 is a previously identified multidrug resistance, conjugative plasmid that is found in S. aureus. In addition to antibiotic resistance, pC02 also carries genes known to be associated with antiseptic resistance. Among these, we previously characterized the contribution of qacA to pC02 mediated reduced chlorhexidine susceptibility. Herein, we demonstrate that pC02 also mediates triclosan resistance, likely due to the presence of fabI, a known triclosan resistance gene. Moreover, we demonstrate that conjugative transfer of pC02 increases triclosan resistance in recipient cells. Competition assays demonstrated a fitness cost associated with carriage of the large pC02 plasmid. However, subinhibitory concentrations of either chlorhexidine or triclosan abrogated this fitness cost. Given the widespread use of these antiseptics, both of which accumulate in wastewater and other environmental reservoirs, indiscriminate use of antiseptics likely imposes a constant selective pressure that promotes maintenance of antimicrobial resistance factors within S. aureus.

Cationic chitosan derivatives as potential antifungals: A review of structural optimization and applications

The increasing resistance of pathogen fungi poses a global public concern. There are several limitations in current antifungals, including few available fungicides, severe toxicity of some fungicides, and drug resistance. Therefore, there is an urgent need to develop new antifungals with novel targets. Chitosan has been recognized as a potential antifungal substance due to its good biocompatibility, biodegradability, non-toxicity, and availability in abundance, but its applications are hampered by the low charge density results in low solubility at physiological pH. It is believed that enhancing the positive charge density of chitosan may be the most effective approach to improve both its solubility and antifungal activity. Hence, this review mainly focuses on the structural optimization strategy of cationic chitosan and the potential antifungal applications. This review also assesses and comments on the challenges, shortcomings, and prospect of cationic chitosan derivatives as antifungal therapy.

Oxidative stress, metabolic and histopathological alterations in mussels exposed to remediated seawater by GO-PEI after contamination with mercury

The modern technology brought new engineering materials (e.g. nanostructured materials) with advantageous characteristics such as a high capacity to decontaminate water from pollutants (for example metal(loid)s). Among those innovative materials the synthesis of nanostructured materials (NSMs) based on graphene as graphene oxide (GO) functionalized with polyethyleneimine (GO-PEI) had a great success due to their metal removal capacity from water. However, research dedicated to environmental risks related to the application of these materials is still non-existent. To evaluate the impacts of such potential stressors, benthic species can be a good model as they are affected by several environmental constraints. Particularly, the mussel Mytilus galloprovincialis has been identified by several authors as a bioindicator that responds quickly to environmental disturbances, with a wide spatial distribution and economic relevance. Thus, the present study aimed to evaluate the impacts caused in M. galloprovincialis by seawater previously contaminated by Hg and decontaminated using GO-PEI. For this, histopathological and biochemical alterations were examined. This study demonstrated that mussels exposed to the contaminant (Hg), the decontaminant (GO-PEI) and the combination of both (Hg + GO-PEI) presented an increment of histopathological, oxidative stress and metabolic alterations if compared to organisms under remediated seawater and control conditions The present findings highlight the possibility to remediate seawater with nanoparticles for environmental safety purposes.

Mechanisms of cetyltrimethyl ammonium chloride-induced toxicity to photosystem II oxygen evolution complex of Chlorella vulgaris F1068

Microalgae photosynthesis is sensitive to coexisted contaminates in aquatic environment, thereby causes adverse effect on algal growth and nutrients uptake. Here, we investigated the photosynthetic toxicity mechanism of cetyltrimethyl ammonium chloride (CTAC)-induced on a green microalga Chlorella vulgaris F1068 (C. vulgaris F1068). Results showed that CTAC reduced the algal growth rate, nutrients removal efficiency and weakened the photosynthetic performance. Meanwhile, the efficiency of oxygen evolution complex (OEC) and oxygen evolvement rates stressed by CTAC were significantly declined to 90.48% and 58.48% of the control (without CTAC), respectively. In addition, atomic force microscopy (AFM) detected the damage of PSII-OEC morphology and structure by CTAC. Furthermore, proteomic analysis showed that 41% of proteins were in the chloroplast thylakoid membranes which function in photosynthesis. The activity of oxygen-evolving enhancer protein 2 (OEE2 or PsbP) involved in electron transfer was significantly inhibited by CTAC, which down-regulated 15.14-fold in the presence of 0.6 mg/L CTAC. These results indicated that photosynthetic inhibition of CTAC mainly occurred in the PSII-OEC. This study provided a new perspective of the photosynthetic response in evaluation of environmental bioimpacts of surfactants on microalgae.

The Recent Progress in Modification of Polymeric Membranes Using Organic Macromolecules for Water Treatment

For decades, the water deficit has been a severe global issue. A reliable supply of water is needed to ensure sustainable economic development in population growth, industrialization and urbanization. To solve this major challenge, membrane-based water treatment technology has attracted a great deal of attention to produce clean drinking water from groundwater, seawater and brackish water. The emergence of nanotechnology in membrane science has opened new frontiers in the development of advanced polymeric membranes to enhance filtration performance. Nevertheless, some obstacles such as fouling and trade-off of membrane selectivity and permeability of water have hindered the development of traditional polymeric membranes for real applications. To overcome these issues, the modification of membranes has been pursued. The use of macromolecules for membrane modification has attracted wide interests in recent years owing to their interesting chemical and structural properties. Membranes modified with macromolecules have exhibited improved anti-fouling properties due to the alteration of their physiochemical properties in terms of the membrane morphology, porosity, surface charge, wettability, and durability. This review provides a comprehensive review of the progress made in the development of macromolecule modified polymeric membranes. The role of macromolecules in polymeric membranes and the advancement of these membrane materials for water solution are presented. The challenges and future directions for this subject are highlighted.

Quantitative structure-activity relationship between the toxicity of amine surfactant and its molecular structure

With the extensive applications and ongoing world demand, more and more amine surfactants are discharged into natural environment. However, the database about toxicity of amine surfactants is incomplete, which is not beneficial to environmental protection process. In this paper, the toxicity of 20 amine surfactants on Daphnia magna were tested to extend the toxicity data of amine surfactants. Besides, 35 molecular structure descriptors including quantum parameters, physicochemical parameters and topological indices were chosen and calculated as independent variables to develop the quantitative structure-activity relationship (QSAR) model between the toxicity of amine surfactants and their molecular structure by genetic function approximation (GFA) algorithm. According to statistical analysis, a robust model was built with the determination coefficient of (R²) was 0.962 and coefficient determinations of cross-validation (R_cv²) was 0.794. Meanwhile, external validation was implemented to evaluate the QSAR model. The result of coefficient determinations of cross-validation (R_ext²) for external validation was calculated as 0.942, illustrating the model has great goodness-of-fit and good prediction ability.

Benzalkonium chloride alters phenotypic and genotypic antibiotic resistance profiles in a source water used for drinking water treatment

Antibiotic resistance is a major public health concern. Triclosan is an antimicrobial compound with direct links to antibiotic resistance that was widely used in soaps in the U.S. until its ban by the U.S. Food and Drug Administration. Benzalkonium chloride (BAC), a quaternary ammonium compound, has widely replaced triclosan in soaps marketed as an antibacterial. BAC has been detected in surface waters and its presence will likely increase following increased use in soap products. The objective of this study was to determine the effect of BAC on relative abundance of antibiotic resistance in a bacterial community from a surface water used as a source for drinking water treatment. Bench-scale microcosm experiments were conducted with microbial communities amended with BAC at concentrations ranging from 0.1 μg L^-1 to 500 μg L^-1. Phenotypic antibiotic resistance was quantified by culturing bacteria in the presence of different antibiotics, and genotypic resistance was determined using qPCR to quantify antibiotic resistance genes (ARGs). BAC at concentrations ranging from 0.1 μg L^-1 to 500 μg L^-1 was found to positively select for bacteria resistant to ciprofloxacin and sulfamethoxazole, and negatively select against bacteria with resistance to six other antibiotics. Exposure to BAC for 14 days increased the relative abundance of sul1 and bla_TEM. This study re-highlights the importance of employing both culture and non-culture-based techniques to identify selection for antibiotic resistance. The widespread use of BAC will likely impact antibiotic resistance profiles of bacteria in the environment, including in source waters used for drinking water, wastewater treatment plants, and natural waterways.

Effective removal of polymer quaternary ammonium salt by biodegradation and a subsequent Fenton oxidation process

In this paper, a process combining biodegradation and Fenton oxidation was proposed for the removal of polydiallyldimethylammonium chloride-acrylic-acrylamide-hydroxyethyl acrylate (PDM) in aqueous phase. Biodegradation of PDM was investigated in activated sludge systems, and the effects of the solution pH, mixed liquid suspended solids (MLSS), salinity, co-substrate, and initial substrate concentration, were studied. The biodegradation process was well-described with the Monod model and the values of the kinetics parameters v_max, k_s were 0.05 h^-1 and 333 mg/L. The optimal biodegradation conditions in the experimental range were determined to be: pH = 7.0, 0%-0.01% (w/v) NaCl, 4000 mg/L of MLSS, and 500 mg/L of glucose as co-substrate. FT-IR analysis indicated that PDM molecules biodegradation partly. The microbial community structures and dehydrogenase activity analysis revealed that PDM showed some toxicity to microorganisms in activated sludge. The effects of several parameters, including the pH and chemical doses, were investigated for removing PDM in Fenton oxidation process. The optimal Fenton oxidation process conditions in the experimental range were pH = 2.0, Fe²⁺ concentration of 40 mg/L, and H₂O₂ dosage of 23 mL/L. PDM was treated by biodegradation and subsequent Fenton oxidation under the optimal operating conditions. The removal efficiency was 44.5% after the biodegradation process and further increased to 85.5% after Fenton oxidation. The combined process was revealed to be a promising solution for achieving effective and economical removal of PDM.

Biodegradability of Dental Care Antimicrobial Agents Chlorhexidine and Octenidine by Ligninolytic Fungi

Chlorhexidine (CHX) and octenidine (OCT), antimicrobial compounds used in oral care products (toothpastes and mouthwashes), were recently revealed to interfere with human sex hormone receptor pathways. Experiments employing model organisms—white-rot fungi Irpex lacteus and Pleurotus ostreatus—were carried out in order to investigate the biodegradability of these endocrine-disrupting compounds and the capability of the fungi and their extracellular enzyme apparatuses to biodegrade CHX and OCT. Up to 70% ± 6% of CHX was eliminated in comparison with a heat-killed control after 21 days of in vivo incubation. An additional in vitro experiment confirmed manganese-dependent peroxidase and laccase are partially responsible for the removal of CHX. Up to 48% ± 7% of OCT was removed in the same in vivo experiment, but the strong sorption of OCT on fungal biomass prevented a clear evaluation of the involvement of the fungi or extracellular enzymes. On the other hand, metabolites indicating the enzymatic transformation of both CHX and OCT were detected and their chemical structures were proposed by means of liquid chromatography–mass spectrometry. Complete biodegradation by the ligninolytic fungi was not achieved for any of the studied analytes, which emphasizes their recalcitrant character with low possibility to be removed from the environment.

Antimicrobial Efficiency and Surface Interactions of Quaternary Ammonium Compound Absorbed on Dielectric Barrier Discharge (DBD) Plasma Treated Fiber-Based Wiping Materials

The physicochemical interactions between alkyldimethylbenzylammonium chloride (ADBAC) as disinfectant and three commercial wiping materials made from 100% polyester (PET), 55%cellulose/45%PET (blend), and 100% cellulose were investigated after treatment with dielectric barrier discharge (DBD) plasma at atmospheric pressure. Wipe material type in terms of cellulose content, liquor ratio, and immersion time demonstrated a significant influence on the adsorption of ADBAC. The higher the content of cellulose in the material, the higher is the adsorption of ADBAC active ingredient. The antimicrobial tests confirm that the ADBAC adsorbed on pure cellulosic material is inactivated losing its bactericidal activity, while 100% PET and blend wipes showed good antimicrobial efficacy. XPS analysis demonstrates the strong interactions of ADBAC with the plasma-generated oxygen species in the polyester-containing wipes surface. Unexpectedly, plasma-treated blend wipe displays a reverse antimicrobial effect compared to untreated samples, performing better in Gram-negative bacteria. The best result was obtained in the plasma treated 100% polyester wipe showing an improvement of about 20% in Gram-positive bacteria and an excellent performance in Gram-negative ones. This method allows the unprecedented use of pure polyester as effective wiping material for surface disinfection eliminating the major drawback of pure polyester, its high hydrophobicity.

The occurrence of the multidrug resistance (MDR) and the prevalence of virulence genes and QACs resistance genes in E. coli isolated from environmental and avian sources

Colibacillosis is a major disease affecting poultry leads to high morbidity and mortality which causing tremendous economic losses worldwide. These economic disparities are amplified among low and middle-income where sanitation and hygiene are challenged by the increasing demand for quality sources of animal protein. With a view to investigating the prevalence of virulence genes and QACs resistance genes as well as monitoring the antibiogram of E. coli strains, a total of 368 specimens were collected from diseased broiler chickens (n = 226) and environmental sources (n = 142) at large-scale poultry farms in Ismailia Governorate, Egypt. The bacteriological examination proved that E. coli prevalence was 26.76% and 50.44% in the farm environment and diseased broilers, respectively. In tandem, the isolated E. coli strains were serogrouped, determining the most common serotypes were O78, O1:H7, O91:H21 and O126. Isolates were tested for antimicrobial susceptibility against 12 antibiotics, screened for 4 virulence genes (iss, papC, eaeA, and cfaI), and screened for 3 QACs resistance genes (qacEΔ1, qacA/B, and qacC/D). All the tested strains were positive for iss and papC genes, only 20.3% of the tested strains were positive for eaeA gene, moreover, the examined strains were negative to CFAI gene. Furthermore, all the tested strains were positive for qacEΔ1, qacA/B, and qacC/D genes. In conclusion; virulence genes (iss, papC) as well as QACs resistance genes are common in avian Pathogenic E. coli and environmental strains and are mainly associated with multi-drug resistance phenomena.

Identifying and Prioritizing Chemicals with Uncertain Burden of Exposure: Opportunities for Biomonitoring and Health-Related Research

BACKGROUND

The National Institutes of Health's Environmental influences on Child Health Outcomes (ECHO) initiative aims to understand the impact of environmental factors on childhood disease. Over 40,000 chemicals are approved for commercial use. The challenge is to prioritize chemicals for biomonitoring that may present health risk concerns.

OBJECTIVES

Our aim was to prioritize chemicals that may elicit child health effects of interest to ECHO but that have not been biomonitored nationwide and to identify gaps needing additional research.

METHODS

We searched databases and the literature for chemicals in environmental media and in consumer products that were potentially toxic. We selected chemicals that were not measured in the National Health and Nutrition Examination Survey. From over 700 chemicals, we chose 155 chemicals and created eight chemical panels. For each chemical, we compiled biomonitoring and toxicity data, U.S. Environmental Protection Agency exposure predictions, and annual production usage. We also applied predictive modeling to estimate toxicity. Using these data, we recommended chemicals either for biomonitoring, to be deferred pending additional data, or as low priority for biomonitoring.

RESULTS

For the 155 chemicals, 97 were measured in food or water, 67 in air or house dust, and 52 in biospecimens. We found in vivo endocrine, developmental, reproductive, and neurotoxic effects for 61, 74, 47, and 32 chemicals, respectively. Eighty-six had data from high-throughput in vitro assays. Positive results for endocrine, developmental, neurotoxicity, and obesity were observed for 32, 11, 35, and 60 chemicals, respectively. Predictive modeling results suggested 90% are toxicants. Biomarkers were reported for 76 chemicals. Thirty-six were recommended for biomonitoring, 108 deferred pending additional research, and 11 as low priority for biomonitoring.

DISCUSSION

The 108 deferred chemicals included those lacking biomonitoring methods or toxicity data, representing an opportunity for future research. Our evaluation was, in general, limited by the large number of unmeasured or untested chemicals. https://doi.org/10.1289/EHP5133.

Sulfur and nitrogen containing plasma polymers reduces bacterial attachment and growth

Role of sulfur (S) and nitrogen (N) groups in promoting cell adhesion or commonly known as biocompatibility, is well established, but their role in reducing bacterial attachment and growth is less explored or not well-understood. Natural sulfur-based compounds, i.e. sulfide, sulfoxide and sulfinic groups, have shown to inhibit bacterial adhesion and biofilm formation. Hence, we mimicked these surfaces by plasma polymerizing thiophene (ppT) and air-plasma treating this ppT to achieve coatings with S of similar oxidation states as natural compounds (ppT-air). In addition, the effects of these N and S groups from ppT-air were also compared with the biocompatible amine-amide from n-heptylamine plasma polymer. Crystal violet assay and live and dead fluorescence staining of E. coli and S. aureus showed that all the N and S coated surfaces generated, including ppHA, ppT and ppT-air, produced similarly potent, growth reduction of both bacteria by approximately 65% at 72 h compared to untreated glass control. The ability of osteogenic differentiation in Wharton's jelly mesenchymal stem cells (WJ-MSCs) were also used to test the cell biocompatibility of these surfaces. Alkaline phosphatase assay and scanning electron microscopy imaging of these WJ-MSCs growths indicated that ppHA, and ppT-air were cell-friendly surfaces, with ppHA showing the highest osteogenic activity. In summary, the N and S containing surfaces could reduce bacteria growth while promoting mammalian cell growth, thus serve as potential candidate surfaces to be explored further for biomaterial applications.

Modified clays alter diversity and respiration profile of microorganisms in long-term hydrocarbon and metal co-contaminated soil

Clays and surfactant‐modified clays (organoclays) are becoming popular as pollutant sorbents due to their high reactivity and low‐cost availability. However, the lack of field testing and data on ecotoxicity limits their application. Considering such aspects, this study assessed the impact of clay amendments to polycyclic aromatic hydrocarbons (PAHs)/cadmium (Cd)‐contaminated soil on microbial respiration profiles (active vs. inactive cells) using redox staining and the relative abundance and diversity of bacteria and archaea. These clay products are bentonite, cationic surfactant‐modified bentonite and palmitic acid‐grafted surfactant‐modified bentonite). After 70 days, the addition of bentonite and its modified forms altered microbial community structure mainly among dominant groups (Actinobacteria, Proteobacteria, Firmicutes and Chloroflexi) with effects varying depending on material loading to soil. Among amendments, fatty acid (palmitic acid) tailored cationic surfactant‐modified bentonite proved to be microbial growth supportive and significantly increased the number of respiration‐active microbial cells by 5% at a low dose of material (e.g. 1%). Even at high dose (5%), the similarity index using operational taxonomic units (OTUs) also indicates that this modified organoclay‐mixed soil provided only slightly different environment than control soil, and therefore, it could offer more biocompatibility than its counterpart organoclay at similar dose (e.g. cationic surfactant‐modified bentonite). This study promotes designing ‘eco‐safe’ clay‐based sorbents for environmental remediation.

Unconventional Oil and Gas Energy Systems: An Unidentified Hotspot of Antimicrobial Resistance?

Biocides used in unconventional oil and gas (UOG) practices, such as hydraulic fracturing, control microbial growth. Unwanted microbial growth can cause gas souring, pipeline clogging, and microbial-induced corrosion of equipment and transportation pipes. However, optimizing biocide use has not been a priority. Moreover, biocide efficacy has been questioned because microbial surveys show an active microbial community in hydraulic fracturing produced and flowback water. Hydraulic fracturing produced and flowback water increases risks to surface aquifers and rivers/lakes near the UOG operations compared with conventional oil and gas operations. While some biocides and biocide degradation products have been highlighted as chemicals of concern because of their toxicity to humans and the environment, the selective antimicrobial pressure they cause has not been considered seriously. This perspective article aims to promote research to determine if antimicrobial pressure in these systems is cause for concern. UOG practices could potentially create antimicrobial resistance hotspots under-appreciated in the literature, practice, and regulation arena, hotspots that should not be ignored. The article is distinctive in discussing antimicrobial resistance risks associated with UOG biocides from a biological risk, not a chemical toxicology, perspective. We outline potential risks and highlight important knowledge gaps that need to be addressed to properly incorporate antimicrobial resistance emergence and selection into UOG environmental and health risk assessments.

Formation, classification and identification of non-extractable residues of 14C-labelled ionic compounds in soil

The influence of an ionic functional group on the fate of chemicals in the environment, especially the formation of non-extractable residues (NER), has not been systematically investigated. Using 4-n-dodecylphenol[phenylring-¹⁴C(U)], 4-n-dodecylbenzenesulfonicacid[phenylring-¹⁴C(U)] sodiumsalt (¹⁴C-DS^-) and 4-n-dodecylbenzyltrimethylammoniumchloride[phenylring-¹⁴C(U)] (¹⁴C-DA⁺) all with a high structural similarity, the formation, classification and identification of NER of negatively (¹⁴C-DS^-), positively (¹⁴C-DA⁺) and uncharged (¹⁴C-DP) chemicals were investigated in a sterilized and non-sterilized soil. After 84 days of incubation in non-sterile soil, 40.6%, 21.7% and 33.5% of the applied radioactivity (AR) of ¹⁴C-DP, ¹⁴C-DS^- and ¹⁴C-DA⁺, respectively, were converted to NER. In contrast, in sterile soil NER formation was markedly lower. The NER were further investigated with respect to sequestered, covalently bound and biogenic residues (i.e. NER types I, II, and III). Silylation of ¹⁴C-DP, ¹⁴C-DS^- and ¹⁴C-DA⁺ derived NER released 3.0-23.2% AR, indicating that these were sequestered, whereas the residual NER (12.9-33.1% AR) was covalently bound to the soil. Analysis of extracts derived by silylation showed that ¹⁴C-DP, but neither ¹⁴C-DS^- nor ¹⁴C-DA⁺, were released by silylation, suggesting that DP might be part of the sequestered NER. Acid hydrolysis of the NER containing soil and subsequent analysis of soil extracts for ¹⁴C-aminoacids indicated that 2.5-23.8% AR were biogenic residues. Most DP and DS^- derived NER were biogenically or covalently bound, whereas DA⁺ predominantly forms sequestered NER in soil. From these results we propose that chemicals forming high amounts of NER should be investigated regarding types I-III NER because sequestered parent compounds should be considered in persistence assessments.

Phytotoxicity and oxidative effects of typical quaternary ammonium compounds on wheat (Triticum aestivum L.) seedlings

The large-scale use of quaternary ammonium compounds (QACs) in medicines or disinfectants can lead to their release into the environment, posing a potential risk to organisms. This study examined the effects of three typical QACs, dodecyltrimethylammonium chloride (DTAC), dodecyldimethylbenzylammonium chloride (DBAC), and didodecyldimethylammonium chloride (DDAC), on hydroponically cultured wheat seedlings. After 14 days of exposure, both hormesis and phytotoxicity were observed in the wheat seedlings. The shoot and root fresh weight gradually increased as QAC concentrations rose from 0.05 to 0.8 mg L^-1. However, higher QAC concentrations severely inhibited plant growth by decreasing shoot and root fresh weight, total root length, and photosynthetic pigment content. Moreover, the increase in malondialdehyde and O₂^.- contents, as well as root membrane permeability, reflected an oxidative burst and membrane lipid peroxidation caused by QACs. However, the effects of QACs on the levels of these oxidative stress markers were compound-specific, and the changes in superoxide dismutase, peroxidases, and catalase activity were partly related to reactive oxygen species levels. Considering the order of median effective concentration values (EC₅₀) and the levels of oxidative stress induced by the three tested QACs, their phytotoxicities in wheat seedlings increased in the following order: DDAC < DTAC < DBAC, which mainly depended on their characteristics and applied concentrations. These results, which illustrated the complexity of QAC toxicity to plants, could potentially be used to assess the risk posed by these compounds in the environment.

Migration of Quaternary Ammonium Cations from Exfoliated Clay/Low-Density Polyethylene Nanocomposites into Food Simulants

Clay/polymer nanocomposites (CPNs) are polymers incorporating refined clay particles that are frequently functionalized with quaternary ammonium cations (QACs) as dispersion aids. There is interest in commercializing CPNs for food contact applications because they have improved strength and barrier properties, but there are few studies on the potential for QACs in CPNs to transfer to foods under conditions of intended use. In this study, we manufactured low-density poly(ethylene) (LDPE)-based CPNs and assessed whether QACs can migrate into several food simulants under accelerated storage conditions. QACs were found to migrate to a fatty food simulant (ethanol) at levels of ∼1.1 μg mg^-1 CPN mass after 10 days at 40 °C, constituting about 4% total migration (proportion of the initial QAC content in the CPN that migrated to the simulant). QAC migration into ethanol was ∼16× higher from LDPE containing approximately the same concentration of QACs but no clay, suggesting that most QACs in the CPN are tightly bound to clay particles and are immobile. Negligible QACs were found to migrate into aqueous, alcoholic, or acidic simulants from CPNs, and the amount of migrated QACs was also found to scale with the temperature and the initial clay concentration. The migration data were compared to a theoretical diffusion model, and it was found that the diffusion constant for QACs in the CPN was several orders of magnitude slower than predicted, which we attributed to the potential for QACs to migrate as dimers or other aggregates rather than as individual ions. Nevertheless, the use of the migration model resulted in a conservative estimate of the mass transfer of QAC from the CPN test specimens.

Antibacterial performance of polymer quaternary ammonium salt-capped silver nanoparticles on Bacillus subtilis in water

In this study, we prepared polymer quaternary ammonium salt–capped silver nanoparticles (PQAS–AgNPs) and investigated their antimicrobial activities. The antimicrobial effectiveness of PQAS–AgNPs on Bacillus subtilis (B. subtilis), and the effect of dose, pH, chloride ion and humic acid (HA) were studied. It was found that PQAS–AgNPs revealed excellent antimicrobial activity to B. subtilis, compared with polyvinylpyrrolidone-capped silver nanoparticles (PVP-AgNPs), which was the reference antimicrobial material. The positive surface, the antimicrobial activity of PQAS, and the synergistic antibacterial effect between PQAS and AgNPs contributed to the significant antibacterial superiority of PQAS–AgNPs. This study demonstrated that the impact of the dose of the material was positive and the microbiocidal efficacy of PQAS–AgNPs was stronger at lower pH. In addition, the antibacterial performance of PQAS–AgNPs decreased in the presence of Cl⁻ and HA. Finally, in combination with the results of FCM and adenosine triphosphate (ATP) content, it was found that PQAS–AgNPs destroyed the respiratory chain of bacterial cells, reduced the synthesis of ATP, and destroyed the cell wall and cell membrane function.

Polymer quaternary ammonium salt–capped silver nanoparticles (PQAS–AgNPs) were synthesized, and they exhibited significant antibacterial capacity against Bacillus subtilis.

Silica-quaternary ammonium "Fixed-Quat" nanofilm coated fiberglass mesh for water disinfection and harmful algal blooms control

Intensification of pollution loading worldwide has promoted an escalation of different types of disease-causing microorganisms, such as harmful algal blooms (HABs), instigating detrimental impacts on the quality of receiving surface waters. Formation of unwanted disinfection by-products (DBPs) resulting from conventional disinfection technologies reveals the need for the development of new sustainable alternatives. Quaternary Ammonium Compounds (QACs) are cationic surfactants widely known for their effective biocidal properties at the ppm level. In this study, a novel silica-based antimicrobial nanofilm was developed using a composite of silica-modified QAC (Fixed-Quat) and applied to a fiberglass mesh as an active surface via sol-gel technique. The synthesized Fixed-Quat nanocoating was found to be effective against E. coli with an inactivation rate of 1.3 × 10^-3 log reduction/cm min. The Fixed-Quat coated fiberglass mesh also demonstrated successful control of Microcystis aeruginosa with more than 99% inactivation after 10 hr of exposure. The developed antimicrobial mesh was also evaluated with wild-type microalgal species collected in a water body experiencing HABs, obtaining a 97% removal efficiency. Overall, the silica-functionalized Fixed-Quat nanocoating showed promising antimicrobial properties for water disinfection and HABs control, while decreasing concerns related to DBPs formation and the possible release of toxic nanomaterials into the environment.

Remediation of arsenic from contaminated seawater using manganese spinel ferrite nanoparticles: Ecotoxicological evaluation in Mytilus galloprovincialis

In the last decade different approaches have been applied for water remediation purposes, including the use of nanoparticles (NPs) to remove metals and metalloids from water. Although studies have been done on the toxic impacts of such NPs, very scarce information is available on the impacts of water after decontamination when discharged into aquatic environments. As such, in the present study we aimed to evaluate the ecotoxicological safety of seawater previously contaminated with arsenic (As) and remediated by using manganese-ferrite (MnFe₂O₄-NPs) NPs. For this, mussels Mytilus galloprovincialis were exposed for 28 days to different conditions, including clean seawater (control), As (1000 μg L^-1) contaminated and remediated (As 70 μg L^-1) seawater, water containing MnFe₂O₄- NPs (50 mg L^-1) with and without the presence of As. At the end of exposure, concentrations of As in mussels tissues were quantified and biomarkers related to mussels' metabolism and oxidative stress status were evaluated. Results revealed that mussels exposed to water contaminated with As and to As + NPs accumulated significantly more As (between 62% and 76% more) than those exposed to remediated seawater. Regarding biomarkers, our findings demonstrated that in comparison to remediated seawater (conditions a, b, c) mussels exposed to contaminated seawater (conditions A, B, C) presented significantly lower metabolic activity, lower expenditure of energy reserves, activation of antioxidant and biotransformation defences, higher lipids and protein damages and greater AChE inhibition. Furthermore, organisms exposed to As, NPs or As + NPs revealed similar biochemical effects, both before and after water decontamination. In conclusion, the present study suggests that seawater previously contaminated with As and remediated by MnFe₂O₄-NPs presented significantly lower toxicity than As contaminated water, evidencing the potential use of these NPs to remediate seawater contaminated with As and its safety towards marine systems after discharges to these environments.

Biocompatible functionalisation of nanoclays for improved environmental remediation

Among the wide range of materials used for remediating environmental contaminants, modified and functionalised nanoclays show particular promise as advanced sorbents, improved dispersants, or biodegradation enhancers. However, many chemically modified nanoclay materials are incompatible with living organisms when they are used in natural systems with detrimental implications for ecosystem recovery. Here we critically review the pros and cons of functionalised nanoclays and provide new perspectives on the synthesis of environmentally friendly varieties. Particular focus is given to finding alternatives to conventional surfactants used in modified nanoclay products, and to exploring strategies in synthesising nanoclay-supported metal and metal oxide nanoparticles. A large number of promising nanoclay-based sorbents are yet to satisfy environmental biocompatibility in situ but opportunities are there to tailor them to produce "biocompatible" or regenerative/reusable materials.

Molecular epidemiology and decreased susceptibility to disinfectants in carbapenem-resistant Acinetobacter baumannii isolated from intensive care unit patients in central China

BACKGROUND

Infection with carbapenem-resistant Acinetobacter baumannii (CRAB) is an increasing problem for critically ill patients. The srains are frequently resistant to all antibiotics and disinfectants are often used to block the spread of these bacteria, playing an important role in infection control.

OBJECTIVES

The aim of this study was to investigate the antibiotic susceptibility, the clonal relationship, disinfectant resistance gene, β-lactamase genes and the disinfectant sensitivity of 82 A. baumannii isolates collected at a large hospital in Wuhan, China.

DESIGN

A retrospective basic study.

METHODS

Here we investigated 82 A. baumannii isolates from intensive care unit patients in a major teaching hospital in China for the distribution of resistance-associated genes and susceptibility to chlorine disinfectant (CLR), benzalkonium bromide (BB) and Chlorhexidine gluconate(CHG). Multi-locus sequence typing (MLST) was applied to explore their genetic evolution relationships.

RESULTS

qacE (30.48%, 25/82) and qac△E1 (76.82%, 63/82) genes were detected in our study, while none were positive for qacA/B, qacC/D or qacG. The MIC values of CLR were 250mg/L; The MIC values ranged from 32 to 128μg/mL for BB; The MIC values ranged from 0.0019% to 0.0078% for CHG. The presence or absence of qacE gene has a significant impact(p＜0.05) on MICs of BB or CHG. All isolates harboured bla_OXA-51/23 genes, and 98.78% of isolates contained the ISaba1 insertion sequence. All isolates were classified into 8 sequence types(STs) within clonal complex 92(CC92).

CONCLUSIONS

The predominant CRAB strains in our intensive care unit are bla_OXA-23-containing A. baumannii of CC92. The high prevalence of qac genes and reduced susceptibility to disinfectants confirm the need for continued vigilance against nosocomial infections.

Application of an algal growth inhibition assay to determine distribution coefficients of benzalkonium ions between kaolinite and water

Benzalkonium compounds are widely used and found in environmental samples. Due to their amphiphilic nature, it is important to know sorption coefficients to account their bioavailability. However, currently available models describing their partitioning were developed using low molecular weight homologues and it cannot be ascertained whether they are applicable to their higher molecular weight homologues. Reasons for the scarcity of data on highly sorptive compounds include the lack of reliable quantification techniques for analyzing these chemicals at environmentally relevant levels. This study, therefore, reports on an algal growth inhibition assay-based method for the determination of kaolinite/water distribution coefficients for benzalkonium compounds at their environmentally relevant concentration range. Sorption to clay was computed using the difference between median effective concentration determined in a culture with kaolinite and that derived from a culture grown in standard medium. A kinetic model was used to account for uptake into algal cells and to calculate free concentrations. Due to the sensitivity of the algal species, Pseudokirchneriella subcapitata, it was possible to determine distribution coefficients below micromole per liter concentrations. The computed distribution coefficients showed a linear increase with number of carbon atoms in the alkyl chain up to 14. The proposed bioassay-based method should be applicable to determine distribution coefficients for highly hydrophobic chemicals and ionic liquids at a concentration range lower than typical analytical limits.

Natural Shape-Retaining Microcapsules With Shells Made of Chitosan-Coated Colloidal Lignin Particles

Thin film coating of charged nanoparticles with oppositely charged polymers is an efficient and straightforward way for surface modification, but synthetic polyelectrolytes should be replaced by abundant biopolymers. In this study a thin film of chitosan was adsorbed onto colloidal lignin particles (CLPs) that were then systematically studied for olive oil stabilization with an objective to develop shape-retaining microcapsules that comprised of only renewable biomaterials. Full surface coverage was achieved with merely 5 wt% of chitosan relative to the dry weight of CLPs, reversing their surface charge from negative to positive. Such modification rendered the chitosan-coated particles excellent stabilizers for forming Pickering emulsions with olive oil. The emulsion droplets could be further stabilized by sodium triphosphate that provided ionic intra- and inter-particle cross-linking of the chitosan corona on the CLPs. Following the optimum conditions, the non-cross-linked microcapsules exhibited a strong stability against coalescence and the electrostatically stabilized ones additionally retained their shape upon drying and rewetting. Non-cross-linked microcapsules were used to demonstrate encapsulation and rapid release of ciprofloxacin as a model lipophilic drug in aqueous media. Overall, the combination of antimicrobial chitosan and antioxidative lignin nanoparticles hold unprecedented opportunities as biocompatible and biodegradable materials for controlled drug delivery.

Quaternary Ammonium Compounds: Simple in Structure, Complex in Application

Quaternary ammonium compounds, referred to as QACs, are cationic substances with a structure on the edge of organic and inorganic chemistry and unique physicochemical properties. The purpose of the present work is to introduce QACs and their wide application potential. Fundamental properties, methods of preparation, and utilization in organic synthesis are reviewed. Modern applications and the use of QACs as reactive substrates, reagents, phase-transfer catalysts, ionic liquids, electrolytes, frameworks, surfactants, herbicides, and antimicrobials are further covered. A brief discussion of the health and environmental impact of QACs is also provided. The emphasis is largely on tetraalkylammonium compounds bearing linear alkyl chains.

Extracellular polymeric substrates of Chlorella vulgaris F1068 weaken stress of cetyltrimethyl ammonium chloride on ammonium uptake

This study investigated the influences of cetyltrimethyl trimethyl ammonium chloride (CTAC), an emerging pollutant quaternary ammonium compound (QAC) in municipal effluents, on the transfer and uptake of NH₄⁺ by Chlorella vulgaris F1068 cells removed EPS artificially (EPS-R) and coated EPS naturally (EPS-C) under different scenarios (e.g., the presence or absence of CTAC, different photoperiod sequences (light 12 h: dark 12 h or dark 12 h: light 12 h)). The results showed that the removal of EPS increased the transfer and uptake of NH₄⁺ but the presence of EPS caged NH₄⁺ and effectively weakened the stress of CTAC (<0.5 mg/L) on NH₄⁺ uptake. The main mechanism was considered that CTAC in the concentration range from 0.1 to 0.5 mg/L induced an increased amount of polysaccharide and protein in EPS and thus protected algal normal physiological functions (including cell membrane permeability and glutamine synthetase activity) from the damage of CTAC (0.1 to 0.5 mg/L) regardless of the photoperiod sequences. Thereby, the findings of this study provided an insight into the role of algal EPS in transfer and uptake of nutrients under the coexisted toxics for the future algae-based sewage treatment application.

Insight into the Hydration of Cationic Surfactants: A Thermodynamic and Dielectric Study of Functionalized Quaternary Ammonium Chlorides

Hydrophobic interactions are one of the main thermodynamic driving forces in self-assembly, folding, and association processes. To understand the dehydration-driven solvent exposure of hydrophobic surfaces, the micellization of functionalized decyldimethylammonium chlorides, XC₁₀Me₂N⁺Cl^-, with a polar functional group, X = C₂OH, C₂OMe, C₂OC₂OMe, C₂OOEt, together with the "reference" compound decyltrimethylammonium chloride, C₁₀Me₃N⁺Cl^-, was investigated in aqueous solution by density measurements, isothermal titration calorimetry (ITC), and dielectric relaxation spectroscopy (DRS). From the density data, the apparent molar volumes of monomers and micelles were estimated, whereas the ITC data were analyzed with the help of a model equation, yielding the thermodynamic parameters and aggregation number. From the DRS spectra, effective hydration numbers of the free monomers and micelles were deduced. The comprehensive analysis of the obtained results shows that the thermodynamics of micellization are strongly affected by the nature of the functional group. Surprisingly, the hydration of micelles formed by surfactant cations with a single alkyl chain on quaternary ammonium is approximately the same, regardless of the alkyl chain length or functionalization of the headgroup. However, notable differences were found for the free monomers where increasing polarity lowers the effective hydration number.

Potential ecotoxicological effects of antimicrobial surface coatings: a literature survey backed up by analysis of market reports

This review was initiated by the COST action CA15114 AMICI "Anti-Microbial Coating Innovations to prevent infectious diseases," where one important aspect is to analyze ecotoxicological impacts of antimicrobial coatings (AMCs) to ensure their sustainable use. Scopus database was used to collect scientific literature on the types and uses of AMCs, while market reports were used to collect data on production volumes. Special attention was paid on data obtained for the release of the most prevalent ingredients of AMCs into the aqueous phase that was used as the proxy for their possible ecotoxicological effects. Based on the critical analysis of 2,720 papers, it can be concluded that silver-based AMCs are by far the most studied and used coatings followed by those based on titanium, copper, zinc, chitosan and quaternary ammonium compounds. The literature analysis pointed to biomedicine, followed by marine industry, construction industry (paints), food industry and textiles as the main fields of application of AMCs. The published data on ecotoxicological effects of AMCs was scarce, and also only a small number of the papers provided information on release of antimicrobial ingredients from AMCs. The available release data allowed to conclude that silver, copper and zinc are often released in substantial amounts (up to 100%) from the coatings to the aqueous environment. Chitosan and titanium were mostly not used as active released ingredients in AMCs, but rather as carriers for other release-based antimicrobial ingredients (e.g., conventional antibiotics). While minimizing the prevalence of healthcare-associated infections appeared to be the most prosperous field of AMCs application, the release of environmentally hazardous ingredients of AMCs into hospital wastewaters and thus, also the environmental risks associated with AMCs, comprise currently only a fraction of the release and risks of traditional disinfectants. However, being proactive, while the use of antimicrobial/antifouling coatings could currently pose ecotoxicological effects mainly in marine applications, the broad use of AMCs in other applications like medicine, food packaging and textiles should be postponed until reaching evidences on the (i) profound efficiency of these materials in controlling the spread of pathogenic microbes and (ii) safety of AMCs for the human and ecosystems.

Discharge of biocidal products from healthcare activities into a sewage system-a case study at a French university hospital

This study focused on the presence of three biocidal products specific to healthcare facilities, i.e. chlorhexidine digluconate (CHD), bis(aminopropyl)laurylamine (BAPLA), and didecyldimethylammonium chloride (DDAC), in a hospital sewage system. Five sampling campaigns were conducted in 2016 and 2017 throughout the entire Poitiers University Hospital sewage system. DDAC concentrations ranging from 933 ± 119 to 3250 ± 482 μg/L were detected in 24-h composite samples, while lower concentrations (both within the same range) were detected for the two other compounds (i.e. 25 ± 5 to 97 ± 39 μg/L for CHD and 18 ± 3 to 142 ± 16 μg/L for BAPLA). Based on these findings, a mass balance was determined for these discharged compounds to compare the quantities detected in discharges to the amounts used for healthcare in the hospital. Hence, 60-90% of the quantities of DDAC used were found to be present at the hospital sewage outfall. Higher percentages of CHD (100-242%) were noted because of the high presumably quantities used for antiseptic applications, which were not considered in mass balance calculation. Finally, only 10-30% of BAPLA quantities used were detected at the site outfall. Analysis of the results for the different sampling points revealed the nature of the emission sources. For surface applications of DDAC and BAPLA, management of hospital linen is thus a major source of discharged biocidal products, probably following the washing of biocide-soaked textiles used for hospital facility maintenance. Moreover, discharge of biocidal products from a healthcare establishment depends especially on biocide handling practices in the emitting establishment. For BAPLA, compliance with hospital recommended dosages and practices whereby operators are required to prepare tailored quantities of detergents and disinfectants for each specific task could largely explain the limited release of this compound.

Role of Bacteriophages in the Implementation of a Sustainable Dairy Chain

The growing human population is currently facing an unprecedented challenge regarding global food sustainability. Thus, it is of paramount to maintain food production and quality while avoiding a negative impact on climate change and the environment at large. Along the food chain, several practices could compromise future food safety and human health. One example is the widespread use of antibiotics and disinfectants in dairy production, which has contributed to the current antibiotic resistance crisis. Moreover, the uncontrolled release of antimicrobials to the environment poses a significant threat to natural ecosystems. For these reasons, research has recently focused on exploiting natural antimicrobials with the goal of achieving a safer and more sustainable dairy production chain. In this context, bacteriophages, viruses that infect bacteria, may become good allies to prevent and treat diseases in cattle, or be used as disinfectants in dairy facilities and as preservatives in dairy products. This review provides an overview of the current research regarding the use of phages as a global approach to reduce economic losses and food waste, while increasing food safety and reducing the environmental impact of food production. Our current understanding of progress, solutions, and future challenges in dairy production, processing, safety, waste processing, and quality assurance is also discussed.

Inhibition of Wild Enterobacter cloacae Biofilm Formation by Nanostructured Graphene- and Hexagonal Boron Nitride-Coated Surfaces

Although biofilm formation is a very effective mechanism to sustain bacterial life, it is detrimental in medical and industrial sectors. Current strategies to control biofilm proliferation are typically based on biocides, which exhibit a negative environmental impact. In the search for environmentally friendly solutions, nanotechnology opens the possibility to control the interaction between biological systems and colonized surfaces by introducing nanostructured coatings that have the potential to affect bacterial adhesion by modifying surface properties at the same scale. In this work, we present a study on the performance of graphene and hexagonal boron nitride coatings (h-BN) to reduce biofilm formation. In contraposition to planktonic state, we focused on evaluating the efficiency of graphene and h-BN at the irreversible stage of biofilm formation, where most of the biocide solutions have a poor performance. A wild Enterobacter cloacae strain was isolated, from fouling found in a natural environment, and used in these experiments. According to our results, graphene and h-BN coatings modify surface energy and electrostatic interactions with biological systems. This nanoscale modification determines a significant reduction in biofilm formation at its irreversible stage. No bactericidal effects were found, suggesting both coatings offer a biocompatible solution for biofilm and fouling control in a wide range of applications.

Natural Shape-Retaining Microcapsules With Shells Made of Chitosan-Coated Colloidal Lignin Particles

Thin film coating of charged nanoparticles with oppositely charged polymers is an efficient and straightforward way for surface modification, but synthetic polyelectrolytes should be replaced by abundant biopolymers. In this study a thin film of chitosan was adsorbed onto colloidal lignin particles (CLPs) that were then systematically studied for olive oil stabilization with an objective to develop shape-retaining microcapsules that comprised of only renewable biomaterials. Full surface coverage was achieved with merely 5 wt% of chitosan relative to the dry weight of CLPs, reversing their surface charge from negative to positive. Such modification rendered the chitosan-coated particles excellent stabilizers for forming Pickering emulsions with olive oil. The emulsion droplets could be further stabilized by sodium triphosphate that provided ionic intra- and inter-particle cross-linking of the chitosan corona on the CLPs. Following the optimum conditions, the non-cross-linked microcapsules exhibited a strong stability against coalescence and the electrostatically stabilized ones additionally retained their shape upon drying and rewetting. Non-cross-linked microcapsules were used to demonstrate encapsulation and rapid release of ciprofloxacin as a model lipophilic drug in aqueous media. Overall, the combination of antimicrobial chitosan and antioxidative lignin nanoparticles hold unprecedented opportunities as biocompatible and biodegradable materials for controlled drug delivery.

The role of surfactants in wastewater treatment: Impact, removal and future techniques: A critical review

Wastewater treatment has an important responsibility to react to changing consumer and industrial produced wastes that pose environmental challenges. Surfactants are one of these emerging contaminants. They are of interest because of their increasingly ubiquitous domestic and industrial use and the difficulty their presence causes traditional treatment. In response to this developing area, this critical review considers research from a variety of technical backgrounds to provide an up to date overview of the impact of surfactants on the environment, health and their removal. This found major concerns about surfactants on the environment and on health being corroborated in the past five years. Current research into removal focuses on existing biological and chemical wastewater treatment optimisation. Despite improvements being found to traditional biological methods using chemical pre-treatments there is a clear lack of consensus regarding the ideal strategy. Drawbacks and potential solutions for a range of these technologies, including Fenton reaction and aerobic degradation, are discussed. In this field the authors recommend an improved diversity in surfactants used for the research and addressing of significant knowledge gaps. Novel methods, such as Carbon Nanotube (CNT) use are also discussed. These methods, while showing promising results, will require continual research effort to resolve present issues such as variable performance and environmental concerns. Larger scale work is also needed to validate the initial work done. Potential uses of surfactants to optimise wastewater treatment, such as Surfactant Modified Zeolites (SMZs), are also discussed. This review finds that surfactant removal from wastewater is a promising and challenging field that warrants further investigation.

Accumulation of quaternary ammonium compounds as emerging contaminants in sediments collected from the Pearl River Estuary, China and Tokyo Bay, Japan

In this work, the distribution of quaternary ammonium compounds (QACs) in two dated sediment cores, collected from the Pearl River Estuary (PRE) and Tokyo Bay (TB), were investigated to understand the historical input of QACs and their diagenetic behavior in urban estuarine environments. The vertical variation profiles of QAC concentrations showed that benzylalkyldimethyl ammonium compounds (BACs) and dialkyldimethyl ammonium compounds (DADMACs) were widely used during 1970s and 1980s both in China and Japan. The declining environmental concentrations of QACs suggested a compositional change of commodities and the effectiveness of emission control strategies. For the individual QAC homologues, BAC homologues decreased significantly over time, while DADMAC compositions remained relatively stable. The differences in concentration and composition profiles of BACs and DADMACs in the sediment cores provided useful information on the patterns of use of QACs in China and Japan, as well as their diagenetic behaviors in the sediments.

Detailed mass flows and removal efficiencies for biocides and antibiotics in Swedish sewage treatment plants

Antimicrobial compounds, such as biocides and antibiotics, are widely used in society with significant quantities of these chemicals ending up in sewage treatment plants (STPs). In this study, mass flows and removal efficiency in different treatment steps at three Swedish STPs were evaluated for eleven different biocides and antibiotics. Mass flows were calculated at eight different locations (incoming wastewater, water after the first sedimentation step, treated effluent, primary sludge, surplus sludge, digested sludge, dewatered digested sludge and reject water). Samples were collected for a total of nine days over three weeks. The STPs were able to remove 53->99% of the antimicrobial compounds and 0-64% were biodegraded on average in the three STPs. Quaternary ammonium compounds were removed from the wastewater >99%, partly through biodegradation, but 38-96% remained in the digested sludge. Chlorhexidine was not biodegraded but was efficiently removed from the wastewater to the sludge. The biological treatment step was the most important step for the degradation of the studied compounds, but also removed several compounds through the surplus sludge. Compounds that were inefficiently removed included benzotriazoles, trimethoprim and fluconazole. The study provides mass flows and removal efficiencies for several compounds that have been seldom studied.