Perfluoroalkyl Substances (PFAS) Affect Inflammation in Lung Cells and Tissues.

Adverse lung outcomes from exposure to per-and polyfluoroalkyl substances (PFAS) are known; however, the mechanism of action is poorly understood. To explore this, human bronchial epithelial cells were grown and exposed to varied concentrations of short-chain (perfluorobutanoic acid, perflurobutane sulfonic acid and GenX) or long-chain (PFOA and perfluorooctane sulfonic acid (PFOS)) PFAS, alone or in a mixture to identify cytotoxic concentrations. Non-cytotoxic concentrations of PFAS from this experiment were selected to assess NLRP3 inflammasome activation and priming. We found that PFOA and PFOS alone or in a mixture primed and activated the inflammasome compared with vehicle control. Atomic force microscopy showed that PFOA but not PFOS significantly altered the membrane properties of cells. RNA sequencing was performed on the lungs of mice that had consumed PFOA in drinking water for 14 weeks. Wild type (WT), PPARα knock-out (KO) and humanized PPARα (KI) were exposed to PFOA. We found that multiple inflammation- and immune-related genes were affected. Taken together, our study demonstrated that PFAS exposure could alter lung biology in a significant manner and may contribute to asthma/airway hyper-responsiveness.

Salinity and hydraulic retention time induce membrane phospholipid acyl chain remodeling in Halanaerobium congolense WG10 and mixed cultures from hydraulically fractured shale wells.

Bacteria remodel their plasma membrane lipidome to maintain key biophysical attributes in response to ecological disturbances. For Halanaerobium and other anaerobic halotolerant taxa that persist in hydraulically fractured deep subsurface shale reservoirs, salinity, and hydraulic retention time (HRT) are important perturbants of cell membrane structure, yet their effects remain poorly understood. Membrane-linked activities underlie in situ microbial growth kinetics and physiologies which drive biogeochemical reactions in engineered subsurface systems. Hence, we used gas chromatography-mass spectrometry (GC-MS) to investigate the effects of salinity and HRT on the phospholipid fatty acid composition of H. congolense WG10 and mixed enrichment cultures from hydraulically fractured shale wells. We also coupled acyl chain remodeling to membrane mechanics by measuring bilayer elasticity using atomic force microscopy (AFM). For these experiments, cultures were grown in a chemostat vessel operated in continuous flow mode under strict anoxia and constant stirring. Our findings show that salinity and HRT induce significant changes in membrane fatty acid chemistry of H. congolense WG10 in distinct and complementary ways. Notably, under nonoptimal salt concentrations (7% and 20% NaCl), H. congolense WG10 elevates the portion of polyunsaturated fatty acids (PUFAs) in its membrane, and this results in an apparent increase in fluidity (homeoviscous adaptation principle) and thickness. Double bond index (DBI) and mean chain length (MCL) were used as proxies for membrane fluidity and thickness, respectively. These results provide new insight into our understanding of how environmental and engineered factors might disrupt the physical and biogeochemical equilibria of fractured shale by inducing physiologically relevant changes in the membrane fatty acid chemistry of persistent microbial taxa. GRAPHICAL ABSTRACTSalinity significantly alters membrane bilayer fluidity and thickness in Halanaerobium congolense WG10.

Vermont-wide assessment of anthropogenic background concentrations of perfluoroalkyl substances in surface soils.

Shallow surface soils from 66 suburban sampling locations across Vermont were analyzed for 17 different perfluoroalkyl acids (PFAA). PFAA were detected in all 66 surface soils, with a total concentration of PFAA ranging from 540 to 36,000 ng/kg dry soil weight (dw). Despite the complexity of site-specific factors, some general trends and correlations in PFAA concentrations were observed. For instance, perfluoro-1-octanesulfonate (PFOS) dominated in all soil samples while seven other PFAA, including perfluoro-n-nonanoic acid, perfluoro-n-octanoic acid, perfluoro-n-hexanoic acid, perfluoro-n-heptanoic acid, perfluoro-n-decanoic acid, perfluoro-n-undecanoic acid, perfluoro-1-butanesulfonate, and perfluoro-1-hexanesulfonate (PFNA, PFOA, PFHxA, PFHpA, PFDA, PFUnDA, and PFBS, respectively), were identified at more than 50 % of the locations. Perfluoroalkyl carboxylic acids (PFCA) showed a positive correlation with total organic carbon, whereas no clear correlation was observed for perfluoroalkyl sulfonate acids (PFSA). In addition, variations in geographical distributions of PFAA were observed, with relatively higher total PFAA in northern regions when compared to Southern Vermont. Moreover, PFHxA, PFNA, PFDA, PFUnDA, PFOS, and total PFAA were positively correlated to land-use types in Northern Vermont. These results are useful for understanding unique behaviors of PFCA vs. PFSA in geospatially distributed surface soils and for providing anthropogenic background data for setting PFAS cleanup standards for surface soils.

A Critical Review on Electric Field-Assisted Membrane Processes: Implications for Fouling Control, Water Recovery, and Future Prospects.

Electrofiltration, an electric field-assisted membrane process, has been a research topic of growing popularity due to its ability to improve membrane performance by providing in situ antifouling conditions in a membrane system. The number of reports on electrofiltration have increased exponentially over the past two decades. These reports explored many innovations, such as novel configurations of an electric field, engineered membrane materials, and interesting designs of foulant compositions and membrane modules. Recent electrofiltration literature focused mainly on compiling results without a comprehensive comparative analysis across different works. The main objective of this critical review is to, first, organize, compare and contrast the results across various electrofiltration studies; second, discuss various types of mechanisms that could be incorporated into electrofiltration and their effect on membrane system performance; third, characterize electrofiltration phenomenon; fourth, interpret the effects of various operational conditions on the performance of electrofiltration; fifth, evaluate the state-of-the-art knowledge associated with modeling efforts in electrofiltration; sixth, discuss the energy costs related to the implementation of electrofiltration; and finally, identify the current knowledge gaps that hinder the transition of the lab-scale observations to industry-scale electrofiltration as well as the future prospects of electrofiltration.

Factors influencing recovery of SARS-CoV-2 RNA in raw sewage and wastewater sludge using polyethylene glycol-based concentration method.

Wastewater surveillance for monitoring severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an important epidemiologic tool for the assessment of population-wide coronavirus disease 2019 (COVID-19). This tool can be successfully implemented only if SARS-CoV-2 RNA in wastewater can be accurately recovered and quantified. The lack of standardized procedure for wastewater virus analysis has resulted in varying SARS-CoV-2 concentrations for the same sample. This study reports the effect of 4 key factors-sample volume, percentage polyethylene glycol (PEG)-NaCl, incubation period, and storage duration at 4°C-on the recovery of spiked noninfectious SARS-CoV-2 RNA in raw sewage and sludge samples. N1 and N2 genes of SARS-CoV-2 were quantified using the reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and digital droplet PCR (RT-ddPCR) techniques. Results indicate that 1) for raw sewage, 50-ml sample volume, 30% PEG-NaCl addition, 6-h incubation, and sample analysis within 24 h of collection can result in much better RNA recovery (RT-qPCR: 72% for N1 and 82% for N2; RT-ddPCR: 55% for N1 and 85% for N2) when compared with commonly used PEG-based method; 2) for sludge, the sample analysis using raw sewage protocol and all other variations of each factor mostly resulted in false negatives for both N1 and N2. The absence of N1 and N2 suggests that sludge samples probably need a pretreatment step that releases RNA entrapped in sludge solids back into bulk solution. In conclusion, our modified PEG-based concentration method can cut down the analysis time at least by half, which in turn helps to implement early detection system for SARS-CoV-2 in wastewater.

Size-selective Catalytic Polymer Acylation with a Molecular Tetrahedron.

Selective catalysis at the molecular level represents a cornerstone of chemical synthesis. However, it still remains an open question how to elevate tunable catalysis to larger length scales to functionalize whole polymer chains in a selective manner. We now report a hydrazone-linked tetrahedron with wide openings, which acts as a catalyst to size-selectively functionalize polydisperse polymer mixtures. Our experimental and computational evidence supports a dual role of the hydrazone-linked tetrahedron. To accelerate functionalization of the polymer substrates, the tetrahedron (i) unfolds the polymer substrates and/or breaks the polymer aggregates as well as (ii) enables target sites (amino groups) on the polymers to coordinate with catalytic units (triglyme) attached to the tetrahedron. With the tetrahedron as the catalyst, we find that the reactivity of the shorter polymers increases selectively. Our findings enable the possibility to engineer hydrolytically stable molecular polyhedra as organocatalysts for size-selective polymer modification.

Hyperspectral Imaging Microscopy of Acetaminophen Adsorbed on Multiwalled Carbon Nanotubes.

In this study, enhanced dark-field hyperspectral imaging (ED-HSI) was employed to directly observe acetaminophen (AAP), a model pharmaceutical and personal care product (PPCP), adsorbed on multiwalled carbon nanotubes with large diameters (L-MWCNT) and small diameters (S-MWCNT) under equilibrium conditions. The ED-HSI results revealed that (1) AAP molecules primarily adsorbed onto the external surfaces, rather than the internal surfaces of L- and S-MWCNT aggregates, (2) or on sidewall of the dispersed tubes, but not at their end caps. Besides, ED-HSI images showed that the surface coverage ratio of AAP/S-MWCNT is smaller than that of AAP/L-MWCNT (1.1 vs 3.4), indicating that there are more available adsorption sites on S-MWCNT than L-MWCNT when the adsorption reached equilibrium. This finding was consistent with the adsorption capacities of S-MWCNT and L-MWCNT (252.7 vs 54.6 mg g-1). Direct visualization of sorption sites for PPCP molecules provides new insights into the heterogeneous structures and surface properties of MWCNT and helps elucidate the adsorption mechanisms that are fundamental to the design of functional adsorbents for PPCP contaminants.

Free Diffusivity of Icosahedral and Tailed Bacteriophages: Experiments, Modeling, and Implications for Virus Behavior in Media Filtration and Flocculation.

The aqueous bulk diffusivities of several near-spherical (icosahedral) and nonspherical (tailed) bacterial viruses were experimentally determined by measuring their flux across large pore membranes and using dynamic light scattering, with excellent agreement between values measured using the two techniques. For the icosahedral viruses, good agreement was also found between measured diffusivity values and values predicted with the Stokes-Einstein equation. However, when the tailed viruses were approximated as spheres, poor agreement was found between measured values and Stokes-Einstein predictions. The shape of the tailed organisms was incorporated into two modeling approaches used to predict diffusivity. Model predictions were found to be in good agreement with measured values, demonstrating the importance of the tail in the diffusive transport of these viruses. Our calculations also show that inaccurate estimates of virus diffusion can lead to significant errors when predicting diffusive contributions to flocculation and to single collector efficiency in media filtration.

Cytotoxic Effect of Lipophilic Bismuth Dimercaptopropanol Nanoparticles on Epithelial Cells.

Bismuth nanoparticles have many interesting properties to be applied in biomedical and medicinal sectors, however their safety in humans have not been comprehensively investigated. The objective of this research was to determine the cytotoxic effect of bismuth dimercaptopropanol nanoparticles (BisBAL NPs) on epithelial cells. The nanoparticles are composed of 18.7 nm crystallites on average and have a rhombohedral structure, agglomerating into chains-like or clusters of small nanoparticles. Based on MTT viability assay and fluorescence microscopy, cytotoxicity was not observed on monkey kidney cells after growing with 5 µM of BisBAL NPs for 24 h. Employing same techniques, identical results were obtained with human epithelial cells (HeLa), showing a not strain-dependent phenomenon. The absence of toxic effects on epithelial cells growing with BisBAL NPs was corroborated with long-time experiments (24-72 hrs.), showing no difference in comparison with growing control (cells without nanoparticles). Further, genotoxicity assays, comet assay and fluorescent microscopy and electrophoresis in bromide-stained agarose gel revealed no damage to genomic DNA of MA104 cells after 24 h. of exposition to BisBAL NPs. Finally, the effect of bismuth nanoparticles on protein synthesis was studied in cells growing with BisBAL NPs for 24 h. SDS-PAGE assays showed no difference between treated and untreated cells, suggesting that BisBAL NPs did not interfere with protein synthesis. Hence BisBAL NPs do not appear to exert cytotoxic effects suggesting their biological compatibility with epithelial cells.

Sustainable polyelectrolyte multilayer surfaces: possible matrix for salt/dye separation.

The development of a sustainable membrane surface based on chitosan/poly(acrylic acid) (CHI/PAA) multilayers suitable for applications in analytical separations is reported here. Bilayers are constructed on polyamide microfiltration membranes at a pH combination of 3/3 (CHI pH/PAA pH) through a layer by layer approach. A 12.5 bilayer yielded a thickness of 400 nm. Low pressure (10 psi) filtrations through a 5.5 bilayered membrane exhibited high flux (7 m(3) m(-2) day(-1)) and selectivity (NaCl/reactive black 5 (RB5) selectivity >8000). The selectivity and flux observed here are the highest reported to date for low pressure filtrations through membranes. The increase in flux with increasing feed salt concentration is correlated with morphological transformations. Salt content above 7500 ppm causes some perturbation of surface layers. The presence of RB5, a model dye in the feed, restores the surface to maintain sustainability. A skin layer as thin as 50 nm imparts a large separation window. An RB5 feed concentration of 500 ppm results in 98.64% rejection with a flux of 25.79 m(3) m(-2) day(-1). The increase in flux with feed dye concentration supports the plasticizing action of RB5. The transport studies with large feed dye concentrations indicate that at a dye concentration of 500 ppm, the linear growing region (pre-exponential, 5.5 bilayer) itself provides a separation window similar to that of 100 ppm. At the same time, 1000 ppm requires a 9.5 bilayer that falls in the nonlinear growing region. Scanning electron microscopy images show the increase in porosity with respect to feed dye. Interesting morphologies that show the sustainable nature of the membrane surfaces along with the transport data of RB5 are presented.

Characterizing reactive oxygen generation and bacterial inactivation by a zerovalent iron-fullerene nano-composite device at neutral pH under UV-A illumination.

A nano-composite device composed of nano-scale zerovalent iron (ZVI) and C60 fullerene aggregates (ZVI/nC60) was produced via a rapid nucleation method. The device was conceived to deliver reactive oxygen species (ROS) generated by photosensitization and/or electron transfer to targeted contaminants, including waterborne pathogens under neutral pH conditions. Certain variations of the nano-composite were fabricated differing in the amounts of (1) ZVI (0.1mM and 2mM) but not nC60 (2.5mg-C/L), and (2) nC60 (0-25mg-C/L) but not ZVI (0.1mM). The generation of ROS by the ZVI/nC60 nano-composites and ZVI nanoparticles was quantified using organic probe compounds. 0.1mM ZVI/2.5mg-C/L C60 generated 3.74-fold higher O2(-) concentration and also resulted in an additional 2-log inactivation of Pseudomonas aeruginosa when compared to 0.1mM ZVI (3-log inactivation). 2mM ZVI/2.5mg-C/L nC60 showed negligible improvement over 2mM ZVI in terms of O2(-) generation or inactivation. Further, incremental amounts of nC60 in the range of 0-25mg-C/L in 0.1mM ZVI/nC60 led to increased O2(-) concentration, independent of UV-A. This study demonstrates that ZVI/nC60 device delivers (1) enhanced O2(-) with nC60 as a mediator for electron transfer, and (2) (1)O2 (only under UV-A illumination) at neutral pH conditions.

Single-walled carbon nanotubes increase pandemic influenza A H1N1 virus infectivity of lung epithelial cells.

BACKGROUND: Airborne exposure to nanomaterials from unintended occupational or environmental exposures or as a consequence of product use may lead to adverse health effects. Numerous studies have focused on single-walled carbon nanotubes (SWCNTs) and their ability to cause pulmonary injury related to fibrosis, and cancer; however few studies have addressed their impact on infectious agents, particularly viruses that are known for causing severe disease. Here we have demonstrated the ability of pristine SWCNTs of diverse electronic structure to increase the susceptibility of small airway epithelial cells (SAEC) to pandemic influenza A H1N1 infection and discerned potential mechanisms of action driving this response. METHODS: Small airway epithelial cells (SAEC) were exposed to three types of SWCNTs with varying electronic structure (SG65, SG76, CG200) followed by infection with A/Mexico/4108/2009 (pH1N1). Cells were then assayed for viral infectivity by immunofluorescence and viral titers. We quantified mRNA and protein levels of targets involved in inflammation and anti-viral activity (INFß1, IL-8, RANTES/CCL5, IFIT2, IFIT3, ST3GAL4, ST6GAL1, IL-10), localized sialic acid receptors, and assessed mitochondrial function. Hyperspectral imaging analysis was performed to map the SWCNTs and virus particles in fixed SAEC preparations. We additionally performed characterization analysis to monitor SWCNT aggregate size and structure under biological conditions using dynamic light scattering (DLS), static light scattering (SLS). RESULTS: Based on data from viral titer and immunofluorescence assays, we report that pre-treatment of SAEC with SWCNTs significantly enhances viral infectivity that is not dependent on SWCNT electronic structure and aggregate size within the range of 106 nm - 243 nm. We further provide evidence to support that this noted effect on infectivity is not likely due to direct interaction of the virus and nanoparticles, but rather a combination of suppression of pro-inflammatory (RANTES) and anti-viral (IFIT2, IFIT3) gene/protein expression, impaired mitochondrial function and modulation of viral receptors by SWCNTs. CONCLUSIONS: Results of this work reveal the potential for SWCNTs to increase susceptibility to viral infections as a mechanism of adverse effect. These data highlight the importance of investigating the ability of carbon-nanomaterials to modulate the immune system, including impacts on anti-viral mechanisms in lung cells, thereby increasing susceptibility to infectious agents.

Silver nanoparticle behavior, uptake, and toxicity in Caenorhabditis elegans: effects of natural organic matter.

Significant progress has been made in understanding the toxicity of silver nanoparticles (Ag NPs) under carefully controlled laboratory conditions. Natural organic matter (NOM) is omnipresent in complex environmental systems, where it may alter the behavior of nanoparticles in these systems. We exposed the nematode Caenorhabditis elegans to Ag NP suspensions with or without one of two kinds of NOM, Suwannee River and Pony Lake fulvic acids (SRFA and PLFA, respectively). PLFA rescued toxicity more effectively than SRFA. Measurement of total tissue silver content indicated that PLFA reduced total organismal (including digestive tract) uptake of ionic silver, but not of citrate-coated Ag NPs (CIT-Ag NPs). The majority of the CIT-Ag NP uptake was in the digestive tract. Limited tissue uptake was detected by hyperspectral microscopy but not by transmission electron microscopy. Co-exposure to PLFA resulted in the formation of NOM-Ag NP composites (both in medium and in nematodes) and rescued AgNO3- and CIT-Ag NP-induced cellular damage, potentially by decreasing intracellular uptake of CIT-Ag NPs.

Characterization of physicochemical properties of nanomaterials and their immediate environments in high-throughput screening of nanomaterial biological activity.

Thousands of nanomaterials (NMs) are in commerce and few have toxicity data. To prioritize NMs for toxicity testing, high-throughput screening (HTS) of biological activity may be the only practical and timely approach to provide the necessary information. As in all nanotoxicologic studies, characterization of physicochemical properties of NMs and their immediate environments in HTS is critical to understanding how these properties affect NM bioactivity and to allow extrapolation to NMs not screened. The purpose of the study, the expert-groups-recommended minimal characterization, and NM physicochemical properties likely to affect measured bioactivity all help determine the scope of characterization. A major obstacle in reaping the full benefits of HTS for NMs is the low throughput of NM physicochemical characterization, which may require more sample quantity than HTS assays. Increasing the throughput and speed, and decreasing the amount of NMs needed for characterization are crucial. Finding characterization techniques and biological activity assays compatible with diverse classes of NMs is a challenge and multiple approaches for the same endpoints may be necessary. Use of computational tools and nanoinformatics for organizing and analyzing data are important to fully utilize the power of HTS. Other desired advances include the ability to more fully characterize: pristine NM without prior knowledge of NM physicochemical properties; non-pristine NMs (e.g., after use); NM in not-perfectly-dispersed suspension; and NM in biological samples at exposure-relevant conditions. Through combining HTS and physicochemical characterization results, we will better understand NM bioactivities, prioritize NMs for further testing, and build computational models to predict NM toxicity.

Effect of chloride on the dissolution rate of silver nanoparticles and toxicity to E. coli.

Pristine silver nanoparticles (AgNPs) are not chemically stable in the environment and react strongly with inorganic ligands such as sulfide and chloride once the silver is oxidized. Understanding the environmental transformations of AgNPs in the presence of specific inorganic ligands is crucial to determining their fate and toxicity in the environment. Chloride (Cl(-)) is a ubiquitous ligand with a strong affinity for oxidized silver and is often present in natural waters and in bacterial growth media. Though chloride can strongly affect toxicity results for AgNPs, their interaction is rarely considered and is challenging to study because of the numerous soluble and solid Ag-Cl species that can form depending on the Cl/Ag ratio. Consequently, little is known about the stability and dissolution kinetics of AgNPs in the presence of chloride ions. Our study focuses on the dissolution behavior of AgNPs in chloride-containing systems and also investigates the effect of chloride on the growth inhibition of E.coli (ATCC strain 33876) caused by Ag toxicity. Our results suggest that the kinetics of dissolution are strongly dependent on the Cl/Ag ratio and can be interpreted using the thermodynamically expected speciation of Ag in the presence of chloride. We also show that the toxicity of AgNPs to E.coli at various Cl(-) concentrations is governed by the amount of dissolved AgCl(x)((x-1)-) species suggesting an ion effect rather than a nanoparticle effect.

Detection, characterization, and abundance of engineered nanoparticles in complex waters by hyperspectral imagery with enhanced Darkfield microscopy.

We introduce a novel methodology based on hyperspectral imagery with enhanced Darkfield microscopy for detection, characterization, and analysis of engineered nanoparticles in both ultrapure water and in complex waters, such as simulated-wetland ecosystem water and wastewater. Hyperspectral imagery analysis of 12 different nanoparticle sample types, scattering the obliquely incident visible and near-infrared light (VNIR: 400-1000 nm) in an enhanced Darkfield background, showed that the sample information in terms of the spatial distribution as well as spectral characteristics unique to each nanoparticle types, at a sensitivity of single nanoparticle (size ≥10 nm) can be obtained. Hyperspectral imagery and Raman spectral analyses of the silver nanoparticles (AgNPs) revealed that the apparent hydrodynamic size of the particle increased while the primary size remained unchanged in the presence of coatings, which is further confirmed by dynamic light scattering measurements. Similar in size, AgNPs with different coatings exhibited similar spectral color (or peak position) but a red-shift in the peak positions by same amount relative to Bare AgNPs was observed. In conclusion, hyperspectral imagery with enhanced Darkfield microscopy can be a promising tool for detection and characterization of engineered nanoparticles in environmental systems, facilitating studies on fate and transformation of these particles in various types of water samples.

Bacteriophage inactivation by UV-A illuminated fullerenes: role of nanoparticle-virus association and biological targets.

Inactivation rates of the MS2 bacteriophage and (1)O(2) generation rates by four different photosensitized aqueous fullerene suspensions were in the same order: aqu-nC(60) < C(60)(OH)(6) ≈ C(60)(OH)(24) < C(60)(NH(2))(6). Alterations to capsid protein secondary structures and protein oxidation were inferred by detecting changes in infrared vibrational frequencies and carbonyl groups respectively. MS2 inactivation appears to be the result of loss of capsid structural integrity (localized deformation) and the reduced ability to eject genomic RNA into its bacterial host. Evidence is also presented for possible capsid rupture in MS2 exposed to UV-A illuminated C(60)(NH(2))(6) through TEM imagery and detection of RNA infrared fingerprints in ATR-FTIR spectra. Fullerene-virus mixtures were also directly visualized in the aqueous phase using a novel enhanced darkfield transmission optical microscope fitted with a hyperspectral imaging (HSI) spectrometer. Perturbations in intermolecular extended chains, HSI, and electrostatic interactions suggest that inactivation is a function of the relative proximity between nanoparticles and viruses and (1)O(2) generation rate. MS2 log survival ratios were linearly related to CT (product of (1)O(2) concentration C and exposure time T) demonstrating the applicability of classical Chick-Watson kinetics for all fullerenes employed in this study. Results suggest that antiviral properties of fullerenes can be increased by adjusting the type of surface functionalization and extent of cage derivatization thereby increasing the (1)O(2) generation rate and facilitating closer association with biological targets.

Long-term transformation and fate of manufactured ag nanoparticles in a simulated large scale freshwater emergent wetland.

Transformations and long-term fate of engineered nanomaterials must be measured in realistic complex natural systems to accurately assess the risks that they may pose. Here, we determine the long-term behavior of poly(vinylpyrrolidone)-coated silver nanoparticles (AgNPs) in freshwater mesocosms simulating an emergent wetland environment. AgNPs were either applied to the water column or to the terrestrial soils. The distribution of silver among water, solids, and biota, and Ag speciation in soils and sediment was determined 18 months after dosing. Most (70 wt %) of the added Ag resided in the soils and sediments, and largely remained in the compartment in which they were dosed. However, some movement between soil and sediment was observed. Movement of AgNPs from terrestrial soils to sediments was more facile than from sediments to soils, suggesting that erosion and runoff is a potential pathway for AgNPs to enter waterways. The AgNPs in terrestrial soils were transformed to Ag(2)S (~52%), whereas AgNPs in the subaquatic sediment were present as Ag(2)S (55%) and Ag-sulfhydryl compounds (27%). Despite significant sulfidation of the AgNPs, a fraction of the added Ag resided in the terrestrial plant biomass (~3 wt % for the terrestrially dosed mesocosm), and relatively high body burdens of Ag (0.5-3.3 µg Ag/g wet weight) were found in mosquito fish and chironomids in both mesocosms. Thus, Ag from the NPs remained bioavailable even after partial sulfidation and when water column total Ag concentrations are low (<0.002 mg/L).

Mechanisms of bacteriophage inactivation via singlet oxygen generation in UV illuminated fullerol suspensions.

Nonenveloped viruses are shown to be inactivated by singlet oxygen ((1)O2) produced in UVA photosensitized aqueous suspensions of a polyhydroxylated fullerene (C60(OH)22-24; fullerol, 40 microM). Experiments were performed with MS2, a ssRNA bacteriophage, as well as two dsDNA phages: PRD1, which has an internal lipid membrane, and T7, which entirely lacks lipids. MS2 was highly susceptible to inactivation, having a rate constant of 0.034 min(-1) with UVA alone, which increased to 0.102 min(-1) with photoactivated fullerol. PRD1 and T7 were not susceptible to UVA alone but were photoinactivated by fullerol with rate constants of 0.026 and 0.035 min(-1), respectively. The role of 1(O)2 was demonstrated by three independent observations: (i) viruses that were insensitive to UVA alone were photoinactivated by rose bengal in the absence of fullerol, (ii) beta-carotene reduced (but did not eliminate) photoinactivation rates, and (iii) singlet oxygen sensor green fluorescence spectroscopy directly detected (1)O2 in UVA illuminated fullerol suspensions. Qualitative evidence is also presented that fullerol aggregates were closely associated with viruses allowing efficient transfer of 1(O)2 to their capsids. Fourier transform infrared spectroscopy revealed significant oxidative modifications to capsid proteins but comparatively minor changes to the DNA and (phospho)lipids. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) suggested (1)O2 induced crosslinking of proteins. Hence, phage inactivation by photoactivated fullerol nanoparticles appears to be caused by cross-linking of capsid protein secondary structures by exogenous (1)O2 and consequentimpairmentof their ability to bind to surface receptors of their bacterial hosts (loss of infectivity) rather than by direct reactions with fullerol.

Spectroscopic characterization of extracellular polymeric substances from Escherichia coli and Serratia marcescens: suppression using sub-inhibitory concentrations of bismuth thiols.

Free and bound (or capsular) EPS produced by suspended cultures of Escherichia coli and Serratia marcescens were characterized in detail using colorimetric analysis of total proteins and polysaccharides, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) in the presence and absence of bismuth-based antifouling agents. Subtle differences in the chemical composition of free and bound EPS were observed for both bacteria in the absence of bismuth. Total polysaccharides and proteins in free and bound EPS decreased upon treatment with subinhibitory concentrations of lipophilic bismuth thiols (bismuth dimercaptopropanol, BisBAL; bismuth ethanedithiol, BisEDT; and bismuth pyrithione, BisPYR), with BisBAL being most effective. Bismuth thiols also influenced acetylation and carboxylation of polysaccharides in EPS from S. marcescens. Extensive homology between EPS samples in the presence and absence of bismuth was observed with proteins, polysaccharides, and nucleic acids varying predominantly only in the total amount produced. Second derivative analysis of the amide I region of FTIR spectra revealed decreases in protein secondary structures in the presence of bismuth thiols. Hence, antifouling properties of bismuth thiols appear to originate in their ability to suppress O-acetylation and protein secondary structure formation in addition to free and bound EPS secretion.