Presence of nanoparticles in wash water from conventional silver and nano-silver textiles

Impacts of sulfidation of silver nanowires on the degradation of bisphenol A in water

Silver nanowires (AgNWs) are widely produced in many electronic and optical products, and could be inevitably discharged into the aquatic environments. Sulfidation is one of the most important transformation processes of AgNWs, and could significantly affect their fate and interactions with other pollutants in aquatic environment. In the present study, the sulfidation products of AgNWs with different atomic ratio of Ag and S were prepared under environmentally relevant conditions. The crystal structure, elemental composition, morphology and size of the sulfidation products were comprehensively characterized by powder X-ray diffraction, UV-vis spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscope. The products were heterostructured nanowires and the Ag₂S/Ag molar ratio increased with extension of the reaction time. The produced Ag₂S-Ag nanowires displayed a good photocatalytic activity and facilitated the degradation of the copresent organic pollutant bisphenol A (BPA) under simulated sunlight irradiation. As sulfidation time increased, more Ag₂S was generated and the Ag₂S-Ag composites displayed high promotion effect on BPA degradation. This effect could be ascribed to the favorable synergistic effects between Ag₂S and AgNWs, such as high electron-hole separation efficiency and low charge transfer resistance. The chemical scavenger experiments demonstrated that superoxide anion radicals and photogenerated holes in the sulfidation products of AgNWs could be the main reactive species for photocatalytic degradation.

Copper Drinking Water Pipes as a Previously Undocumented Source of Silver-Based Nanoparticles

Wastewater streams are widely known to release silver-based nanoparticles (Ag-b-NPs) into the environment with a plethora of unknown consequences. Until recently, studies have commonly associated Ag-b-NP sources with products that contain these NPs for antimicrobial reasons, such as fabrics, cosmetics, and medical products. However, our study reveals that there is a thus far completely undocumented source of Ag-b-NPs: copper drinking water pipes. We applied cloud point extraction hyphenated to electrothermal atomic absorption spectrometry or single-particle inductively coupled plasma mass spectrometry to analyze the concentration and perform size-selective quantification of Ag-b-NPs in tap water passing through copper pipes. Up to 83 ng of total silver and 25 ng of Ag-b-NPs were present in tap water samples per liter, which resulted in an NP proportion of approximately 30% of total silver. In total, 96% of the measurable particle sizes ranged from 10 to 36 nm. Additionally, 53 μg of copper was released per liter tap water on average. The measurements included tap water from different sampling days and from four different buildings with varying ages, whereas Ag-b-NPs could be detected in the tap water of two buildings. Silver traces in the copper pipe material of 27.5 ± 4.4 μg g^-1 were found to be responsible for the release of nanoparticulate silver into the tap water.

Characterisation of Electrical and Stiffness Properties of Conductive Textile Coatings with Metal Flake-Shaped Fillers

Two conductive formulations containing different types of micron-sized metal flakes (silver-coated copper (Cu) and pure silver (Ag)) were characterised and used to form highly electrically conductive coatings (conductors) on plain and base-coated woven fabrics, the latter in an encapsulated construction. With e-textiles as the intended application, the fabric stiffness, in terms of flexural stiffness and sheet resistance (R_sh), after durability testing (laundering and abrasion) was investigated and related to user friendliness and long-term performance. Bare and encapsulated conductors with increasing amounts of deposited solids were fabricated by adjusting the knife coating parameters, such as the coating gap height (5, 20, 50, and 200 μm), which reduced the R_sh, as determined by four-point probe (4PP) measurements; however, this improvement was at the expense of increased flexural stiffness of the coated fabrics. The addition of a melamine derivative (MF) as a cross-linker to the Cu formulation and the encapsulation of both conductor types gave the best trade-off between durability and R_sh, as confirmed by 4PP measurements. However, the infrared camera images revealed the formation of hotspots within the bare conductor matrix, although low resistances (determined by 4PP) and no microstructural defects (determined by SEM) were detected. These results stress the importance of thorough investigation to assure the design of reliable conductors applied on textiles requiring this type of maintenance.

Roles of Silver-Chloride Complexations in Sunlight-Driven Formation of Silver Nanoparticles

In aerobic natural surface water, a silver ion (Ag⁺) exists in various Ag⁺-Cl^- complexes because of a strong affinity for a chloride ion (Cl^-); however, little information is available about the role of the Ag⁺-Cl^- complex in the formation of silver nanoparticles (AgNPs). This study demonstrates that soluble AgCl_x^(x-1)- species act as a precursor of AgNPs under simulated sunlight irradiation. The AgNP photoproduction increases with Cl^- levels up to 0.0025 M ([Ag⁺] = 5 × 10^-7 M) and decreases with continued Cl^- level increase (0.09 to 0.5 M). At [Cl^-] ≤ 0.0025 M (freshwater systems), photoproduction of AgNP correlates with the formation of AgCl_(aq), suggesting that it is the most photoactive species in those systems. Matching the ionic strength of experiments containing various Cl^- levels indicates that the trend in AgNP photoproduction correlates with Cl^- concentrations rather than ionic strength-induced effects. The photoproduction of AgNPs is highly pH-dependent, especially at pH > 8.3. The UV and visible light portions of the solar light spectrum are equally important in photoreduction of Ag⁺. Overall, we show evidence that AgCl_x^(x-1)- species irradiated under sunlight conditions contributes to the formation of nanosized silver (Ag) in the environment.

Influence of Chain Architecture on Nanopore Accessibility in Polyelectrolyte Block-Co-Oligomer Functionalized Mesopores

Functionalized ordered mesoporous silica materials are commonly investigated for applications such as drug release, sensing, and separation processes. Although, various homopolymer functionalized responsive mesopores are reported, little focus has been put on copolymers in mesopores. Mesoporous silica films are functionalized with responsive and orthogonally charged block-co-oligomers. Responsive 2-dimethylamino)ethyl methacrylate)-block-2-(methacryloyloxy)ethyl phosphate (DMAEMA-b-MEP) block-co-oligomers are introduced into mesoporous films using controlled photoiniferter initiated polymerization. This approach allows a very flexible charge composition design. The obtained block-co-oligomer functionalized mesopores show a complex gating behavior indicating a strong interplay between the different blocks emphasizing the strong influence of charge distribution inside mesopores on ionic pore accessibility. For example, in contrast to mesopores functionalized with zwitterionic polymers, DMAEMA-b-MEP block-co-oligomer functionalized mesopores, containing two oppositely charged blocks, do not show bipolar ion exclusion, demonstrating the influence of the chain architecture on mesopore accessibility. Furthermore, ligand binding-based selective gating is strongly influenced by this chain architecture as demonstrated by an expansion of pore accessibility states for block-co-oligomer functionalized mesopores as compared to the individual polyelectrolyte functionalization for calcium induced gating.

Morphological Transformation of Silver Nanoparticles from Commercial Products: Modeling from Product Incorporation, Weathering through Use Scenarios, and Leaching into Wastewater

There is increasing interest in the environmental fate and effects of engineered nanomaterials due to their ubiquitous use in consumer products. In particular, given the mounting evidence that dramatic transformations can occur to a nanomaterial throughout its product lifecycle, the appropriateness of using pristine nanomaterials in environmental testing is being questioned. Using a combination of transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-mass spectrometry (ICP-MS), this work examines the morphological and compositional effects of conditions mimicking a typical lifecycle of a nano-enabled product, from the production of the silver nanoparticle (AgNP)-laden textiles, through its use, laundering, and then finally, its leaching and incubation in the wastewater collection system. These simulated weathering conditions showed evidence for the transformation of AgNPs into AgCl and Ag₂S. Incubation in raw wastewater had the most dramatic effect on the AgNPs in terms of transformation, no matter what initial weathering was applied to the NPs prior to incubation. However, despite extensive transformation noted, AgNPs were still present within all the samples after the use scenarios.

Intracellular Dissolution of Silver Nanoparticles: Evidence from Double Stable Isotope Tracing

To track transformations of silver nanoparticles (AgNPs) in vivo, HepG2 and A549 cells were cocultured with two enriched stable Ag isotopes (¹⁰⁷AgNPs and ¹⁰⁹AgNO₃) at nontoxic doses. After enzymatic digestion, ¹⁰⁷AgNPs, ionic ¹⁰⁷Ag⁺ and ¹⁰⁹Ag⁺ in exposed cells could be separated and quantified by liquid chromatography combined with ICP-MS. We found that ratios of ¹⁰⁷Ag⁺ to total ¹⁰⁷Ag and proportions of ¹⁰⁷Ag⁺/ ¹⁰⁹Ag⁺ in cells increased gradually after exposure, proving that the Trojan-horse mechanism occurred, i.e., AgNPs released high contents of Ag⁺ after internalization. While the presence of ¹⁰⁹Ag⁺ (5 and 100 μg/L) has little influence on the uptake of ¹⁰⁷AgNPs (0.1 and 2 mg/L), the presence of ¹⁰⁷AgNPs at a high dose (2 mg/L) dramatically increases the ingestion of ¹⁰⁹Ag⁺, even though ¹⁰⁷AgNPs at a low dose (100 μg/L) showed negligible effects on the internalization of ¹⁰⁹Ag⁺. Cellular homeostasis may be perturbed under sublethal exposure of ¹⁰⁷AgNPs, and thus enhanced uptake of ¹⁰⁹Ag⁺. Our findings suggest that the widely adopted control experiments in toxicology studies, culturing organisms with AgNO₃ at the same concentration of Ag⁺ in the AgNP exposure medium, may underestimate uptake of Ag⁺ and thus cannot exclude suspected toxic effects of Ag⁺ at high AgNP exposure doses.

Ag Nanoparticles/α-Ag2WO4 Composite Formed by Electron Beam and Femtosecond Irradiation as Potent Antifungal and Antitumor Agents

The ability to manipulate the structure and function of promising systems via external stimuli is emerging with the development of reconfigurable and programmable multifunctional materials. Increasing antifungal and antitumor activity requires novel, effective treatments to be diligently sought. In this work, the synthesis, characterization, and in vitro biological screening of pure α-Ag₂WO₄, irradiated with electrons and with non-focused and focused femtosecond laser beams are reported. We demonstrate, for the first time, that Ag nanoparticles/α-Ag₂WO₄ composite displays potent antifungal and antitumor activity. This composite had an extreme low inhibition concentration against Candida albicans, cause the modulation of α-Ag₂WO₄ perform the fungicidal activity more efficient. For tumor activity, it was found that the composite showed a high selectivity against the cancer cells (MB49), thus depleting the populations of cancer cells by necrosis and apoptosis, without the healthy cells (BALB/3T3) being affected.

The response of nitrogen removal and related bacteria within constructed wetlands after long-term treating wastewater containing environmental concentrations of silver nanoparticles

The wide application of consumer products containing silver nanoparticles (AgNPs) inevitably results in their release into sewer systems and wastewater treatment plants, where they would encounter (and cause potential negative impacts) constructed wetlands (CWs), a complex biological system containing plants, substrate and microorganisms. Herein, the long-term effects of environmental AgNPs concentrations on nitrogen removal, key enzymatic activities and nitrogen-related microbes in constructed wetlands (CWs) were investigated. The short-term exposure (40 d) to AgNPs significantly inhibited TN and NH₄⁺-N removal, and the inhibition degree had a positive relationship with AgNPs levels. After about 450 d exposure, 200 μg/L AgNPs could slightly increase average TN removal efficiency, while presence of 50 μg/L AgNPs showed no difference, compared to control. The NH₄⁺-N removal in all CWs had no difference. The present study indicated that short-term AgNPs loading evidently reduced nitrogen removal, whereas long-term exposure to AgNPs showed no adverse impacts on NH₄⁺-N removal and slightly stimulated TN removal, which was related to the increase of corresponding enzymatic activities. After exposing AgNPs for 450 d, the abundance of relative functional genes and the composition of key community structure were determined by qPCR and high-throughput sequencing, respectively. The results showed that the abundance of amoA and nxrA dramatically higher than control, whereas the abundance of nirK, nirS, nosZ and anammox 16S rRNA was slightly higher than control, but had no statistical difference, which accorded with the TN removal performance. The microbial community analysis showed that different AgNPs concentrations could affect the microbial diversity and structure. The changes of the relative abundance of nitrogen-related genera were associated with the impacts of AgNPs on the nitrogen removal performance. Overall, the AgNPs loading had impacts on the key enzymatic activities, the abundance of nitrogen-related genes and microbial community, thus finally affected the treatment performance of CWs.

Determination of Nanoparticle Uptake, Distribution, and Characterization in Plant Root Tissue after Realistic Long-Term Exposure to Sewage Sludge Using Information from Mass Spectrometry

The use of nanoparticles (NPs) in numerous products and their potential accumulation causes major concern for humans and the environment. Until now, the uptake of NPs in plant tissue was mostly shown under greenhouse conditions at high doses and short exposure periods. Here, we present results on the uptake of particulate silver (Ag) and cerium dioxide (CeO₂) in the tissues of Triticum aestivum, Brassica napus, and Hordeum vulgare, after exposure to sewage sludge treated with nano-Ag (NM300 K at 1.8 and 7.0 mg/kg sludge per dm soil) and nano-CeO₂ (NM212 at 10 and 50 mg/kg sludge per dm soil). All plants were cultivated in a rural area near the German town Schmallenberg according to the common regional crop rotation on outdoor lysimeters. The highest concentrations measured were 86.4 mg/kg for Ag ( Hordeum vulgare) and 94 mg/kg for Ce ( Triticum sativum). Analysis of plant samples revealed the presence of Ag mainly in its ionic form. However, the occurrence of nano- and larger sized particles of Ag and CeO₂ was observed as well. Quantitative shares of the particulate fraction of the total element concentration were estimated up to 22.4% for Ag and up to 85.1% for CeO₂. A high abundance of particle agglomerates in the phloem suggests upward transport of the nanoparticles to other plant parts. A small number of agglomerates in the xylem suggests a downward transport and subsequent accumulation in the root phloem. Exemplary investigations of Brassica napus root exposed to nano-CeO₂ revealed no accumulation of the pristine material in the cell nucleus; however, CePO₄ was found_. The presence of this substance points to a dissolution of the low soluble CeO₂ in planta and subsequent precipitation. Furthermore, for the first time, mixed NP-salt agglomerates, composed of Ca₃PO₄⁺ and K₃SO₄⁺ NPs, could be observed within Brassica napus root tissue.

Sampling and pre-treatment effects on the quantification of (nano)silver and selected trace elements in surface water - Application in a Dutch case study

Detection and quantification of trace elements in aqueous samples is crucial in terms of environmental monitoring and risk assessment for (heavy) metals in the environment. Silver (Ag) in its nanoparticulate form is commonly used as antimicrobial additive in consumer products and pharmaceuticals. Since released dissolved Ag species act as the actual antimicrobial agent, Ag nanomaterials are supposed to pose risks to the environment by a release of dissolved species. Unfortunately, no standard protocols exist yet to gain reliable information about the presence and distribution of nanomaterials in the environment. Therefore, we present an interlaboratory collaboration involving three laboratories to quantify silver, silver based nanoparticles (Ag-b-NPs) and a wide range of relevant trace elements after different sample pre-treatments for profiling surface water of a Dutch channel. Besides quantification of the elements, different sample pretreatments like acidification, with or without filtration, and their effect on the measurable elemental content were studied. Total Ag and Ag-b-NPs were quantified at lower ng L^-1 range in the channel water whereas reasonable differences depending on the pre-treatment were identified; Ba, As, Pb, Co, Cr, Cu, Ni and Zn were detected at μg L^-1 range and Na, K, Mg, Ca and Fe at mg L^-1 range. Significant sample pre-treatment effects were observed for the elements Cr, Cu, Fe, Pb and Zn, which is very likely due to the existence of particulate species. Measured concentrations were well comparable among the three laboratories underpinning method validity and correctness allowing for a comprehensive, reliable risk assessment for nanomaterials in the environment.

Substrate-Independent Coating with Persistent and Stable Antifouling and Antibacterial Activities to Reduce Bacterial Infection for Various Implants

Implantation of biomedical devices accompanying infections has caused severe problems to public health that require feasible solutions. In this study, a simple approach is reported to fabricate a antimicrobial and antifouling dual-functional coating. This coating consists of a substrate-independent layer-by-layer (LBL) film formed by poly (diallyldimethylammonium) (PDDA) and poly (styrenesulfonate) (PSS), where parts of PSS and PDDA are physically substituted by hetero-bifunctional polyethylene glycol (PEG) ending with a carboxyl group and antimicrobial peptide (ε-Poly-l-lysine, ε-PL). This design (ε-PL-PEG-(PDDA/PSS)9 coating) exhibits not only potent antimicrobial activity against Gram-positive/negative bacteria but also superior antifouling activity on various substrates, including glass and plastic. Moreover, the antifouling and antibacterial performance can be maintained for a longer period of time under physiological environments even after physical damage of the surface due to the homogeneous interspersion and free migration of ε-PL-PEG-COOH in the LBL film. This allows the supplement of these molecules to the surface against molecule loss during usage. Both in vitro and in vivo (rodent subcutaneous infection model) studies show obvious reduction of the bacteria on the coated substrate and in the surrounding tissues with up to 3.2-log reduction, even after repeated usage. The inflammation around the implantation area is also significantly inhibited.

Disposable Paper-Based Analytical Device for Visual Speciation Analysis of Ag(I) and Silver Nanoparticles (AgNPs)

A disposable, instrument-free, height readout paper-based analytical device (HR-PAD) based on a paper strip inkjet-printed with CdTe quantum dots (QDs) was developed for the sensitive speciation analysis of Ag⁺ and silver nanoparticles (AgNPs). When the paper strip is immersed into a sample solution, capillary action draws it through the surface and any Ag⁺ in the solution quenches the fluorescence of CdTe QDs via a cation exchange reaction between Ag⁺ and the CdTe QDs, with the height of the quenched band being proportional to the concentration of Ag⁺. In contrast, fluorescence quenching cannot be observed when only AgNPs are present in solution. Thus, the concentration of AgNPs can be obtained by subtracting the Ag⁺ content from the total silver determined by the HR-PAD after digestion with HNO₃. Under optimized conditions, the methodology provides high selectivity, sensitivity, and accuracy for the detection of Ag⁺ or AgNPs in various samples, even at concentrations as low as 0.05 mg L^-1. Precisions of 4.5% and 2.2% RSDs were achieved at concentrations of 1 mg L^-1 and 7 mg L^-1 of Ag⁺, respectively. Compared to conventional methods, this approach is inexpensive and user-friendly and eliminates the need for expensive and sophisticated detection instruments. The practicality of the method was demonstrated via the speciation analysis of AgNPs and Ag⁺ in river water and 12 commercial products with satisfactory results.

Bactericidal and Cytotoxic Properties of Silver Nanoparticles

Silver nanoparticles (AgNPs) can be synthesized from a variety of techniques including physical, chemical and biological routes. They have been widely used as nanomaterials for manufacturing cosmetic and healthcare products, antimicrobial textiles, wound dressings, antitumor drug carriers, etc. due to their excellent antimicrobial properties. Accordingly, AgNPs have gained access into our daily life, and the inevitable human exposure to these nanoparticles has raised concerns about their potential hazards to the environment, health, and safety in recent years. From in vitro cell cultivation tests, AgNPs have been reported to be toxic to several human cell lines including human bronchial epithelial cells, human umbilical vein endothelial cells, red blood cells, human peripheral blood mononuclear cells, immortal human keratinocytes, liver cells, etc. AgNPs induce a dose-, size- and time-dependent cytotoxicity, particularly for those with sizes ≤10 nm. Furthermore, AgNPs can cross the brain blood barrier of mice through the circulation system on the basis of in vivo animal tests. AgNPs tend to accumulate in mice organs such as liver, spleen, kidney and brain following intravenous, intraperitoneal, and intratracheal routes of administration. In this respect, AgNPs are considered a double-edged sword that can eliminate microorganisms but induce cytotoxicity in mammalian cells. This article provides a state-of-the-art review on the synthesis of AgNPs, and their applications in antimicrobial textile fabrics, food packaging films, and wound dressings. Particular attention is paid to the bactericidal activity and cytotoxic effect in mammalian cells.

Chemical and Physical Transformations of Silver Nanomaterial Containing Textiles After Modeled Human Exposure

The antimicrobial properties of silver nanomaterials (AgNM) have been exploited in various consumer applications, including textiles such as wound dressings. Understanding how these materials chemically transform throughout their use is necessary to predict their efficacy during use and their behavior after disposal. The aim of this work was to evaluate chemical and physical transformations to a commercial AgNM-containing wound dressing during modeled human exposure to synthetic sweat (SW) or simulated wound fluid (WF). Scanning electron microscopy with energy dispersive X-ray spectroscopy (EDS) revealed the formation of micrometer-sized structures at the wound dressing surface after SW exposure while WF resulted in a largely featureless surface. Measurements by X-ray photoelectron spectroscopy (XPS) revealed a AgCl surface (consistent with EDS) while X-ray diffraction (XRD) found a mixture of zero valent silver and AgCl suggesting the AgNM wound dressings surface formed a passivating AgCl surface layer after SW and WF exposure. For WF, XPS based findings revealed the addition of an adsorbed protein layer based on the nitrogen marker which adsorbed released silver at prolonged exposures. Silver release was evaluated by inductively coupled plasma mass spectrometry which revealed a significant released silver fraction in WF and minimal released silver in SW. Analysis suggests that the protein in WF sequestered a fraction of the released silver which continued with exposure time, suggesting additional processing at the wound dressing surface even after the initial transformation to AgCl. To evaluate the impact on antimicrobial efficacy, zone of inhibition (ZOI) testing was conducted which found no significant change after modeled human exposure compared to the pristine wound dressing. The results presented here suggest AgNM-containing wound dressings transform chemically in simulated human fluids resulting in a material with comparable antimicrobial properties with pristine wound dressings. Ultimately, knowing the resulting chemical properties of the AgNM wound dressings will allow better predictive models to be developed regarding their fate.

Considering the forms of released engineered nanomaterials in probabilistic material flow analysis

Most existing models for assessing the releases of engineered nanomaterials (ENMs) into the environment are based on the assumption that ENMs remain in their pristine forms during their whole life cycle. It is known, however, that this is not always the case as ENMs are often embedded into solid matrices during manufacturing and can undergo physical or chemical transformations during their life cycle, e.g. upon release to wastewater. In this work, we present a method for systematically assessing the forms in which nano-Ag and nano-TiO₂ flow through their life cycle (i.e. production, manufacturing, use and disposal) to their points of release to air, soil and surface water. Input data on the forms of released ENMs were probability distributions based on peer-reviewed literature. Release data were incorporated into a probabilistic material flow analysis model to quantify the proportions of ENMs in product-embedded, matrix-embedded, pristine, transformed and dissolved forms in all technical and environmental compartments into which they flow, at the European scale. Releases of nano-Ag to surface water and soil were modelled to occur primarily in transformed forms (Q25 and Q75 of 34-58% and 78-86%, respectively, with means of 53% and 82%), while releases to air were mostly in pristine and matrix-embedded forms (38-46% and 36-44%, respectively, with means of 42% and 40%). In contrast, nano-TiO₂ releases to air, soil and water were estimated to be predominantly in pristine form (75-85%, 90-95%, 96-98%, respectively, with means of 80%, 91% and 97%). The distributions of ENM releases between forms developed here will improve the representativeness and appropriateness of input data for environmental fate modelling and risk assessment of ENMs.

Interpreting the effects of natural organic matter on antimicrobial activity of Ag2S nanoparticles with soft particle theory

Natural organic matter (NOM) ubiquitously exists in natural waters and would adsorb onto the particle surface. Previous studies showed that NOM would alleviate the toxicity of nanomaterials, while the mechanism is seldom quantitatively interpreted. Herein, the effects of humic substances [Suwannee River fulvic acid (SRFA) and Suwannee River humic acid (SRHA)] and biomacromolecules [alginate and bovine serum albumin (BSA)] on the aggregation and antimicrobial effects of silver sulfide nanoparticles (Ag₂S-NPs) were investigated. The aggregation kinetics of Ag₂S-NPs in electrolyte solutions were in agreement with the results based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The dynamic light scattering (DLS) results showed that the SRFA, SRHA, alginate and BSA molecules coated on the Ag₂S-NPs surfaces. The NOM coating layer prevented salt-induced coagulation of Ag₂S-NPs, and the effects of BSA and SRHA on Ag₂S-NPs stabilizing were more obvious than that of SRFA and alginate. Flow cytometry analysis results suggested that BSA and SRHA were more effective on alleviating the Ag₂S-NPs induced cell (Escherichia coli) membrane damage than SRFA and alginate. After interpreting the electrophoretic mobility (EPM) data of the NOM coated Ag₂S-NPs by Ohshima's soft particle theory, it was found that the thickness of the NOM coating layers followed the orders of BSA > SRHA > alginate > SRFA. The E.coli cell membrane damage level was negatively correlated with the thickness and softness of the coating layer. NOM coating may physically alleviate the contact between NPs and E. coli cells and thus attenuate the extent of cell membrane damage caused by the NP-cell interaction. This work provides a new perspective for quantitatively interpreting the influence of NOM on the environmental behaviors and risks of nanomaterials.

Water-Insoluble Polymeric Guanidine Derivative and Application in the Preparation of Antibacterial Coating of Catheter

Antibacterial coatings have been considered as an effective method for preventing the implant-associated infections caused by the bacterial colonization. In this study, we report a water-insoluble polyelectrolyte-surfactant complex, poly(hexamethylene biguanide) hydrochloride-sodium stearate (PHMB-SS) that can be facilely coated onto the surfaces of biomedical catheter and kill the bacteria by releasing the PHMB and prevent the generation of the biofilm. The PHMB-SS-coated surfaces showed better bactericidal activity toward Staphylococcus aureus and Escherichia coli. The PHMB-SS-coated catheters could not only relatively prevent the bacterial colonization in vitro but also in an implant-associated bacterial infection animal model in vivo. Moreover, no significant cytotoxicity and host response were observed in vitro and in vivo, indicating the high biocompatibility of the coating. The water-insoluble antibacterial coating reported in this work represents a novel approach to build a simple and effective coating for the prevention of device-associated infections.

Transformation of AgCl Particles under Conditions Typical of Natural Waters: Implications for Oxidant Generation

The engineered silver nanoparticles (AgNPs) used in consumer products are ultimately released to the environment either as Ag(0), silver sulfide (Ag₂S(s)), silver chloride (AgCl(s)), and/or dissolved Ag(I) complexes. Of these, AgCl(s) and Ag₂S(s) exhibit semiconducting properties and hence may have significant implications to oxidant generation and subsequent redox transformations in natural waters. In this work, we investigate the transformation and photoreactivity of AgCl(s) under simulated natural water conditions with the photoreactivity probed by measuring the oxidation of formate (HCOO^-), a simple compound with a well-defined oxidation pathway. Our results show that AgCl(s) undergoes rapid dissolution in the presence of chloride concentrations representative of seawater (ca. 0.5 M NaCl) forming dissolved Ag(I) complexes but is stable in fresh waters and slightly brackish waters (≤200 mM NaCl). We further show that under these lower salinity conditions in which AgCl(s) is stable, pH has a significant impact on the reactivity of semiconducting AgCl(s). The photoreactivity (measured as initial HCOO^- oxidation rate) of AgCl(s) is relatively constant at pH 4.0 for periods of 24 h or more; however, it decreases rapidly under alkaline conditions. The rapid transformation (or "aging") of AgCl(s) under alkaline conditions suggests that AgCl(s), potentially transported through wastewater effluent to fresh or brackish water environments, may not have a significant impact in such environments. In comparison, in situ formed AgCl(s), potentially formed as a result of the oxidation of high concentrations (≥60 μg Ag·L^-1) of Ag(0) and/or Ag₂S(s), may have significant implications to oxidant generation in natural waters. Our results further show that rapid cycling of Ag between the 0 and +I redox states in sunlit surface waters as a result of the presence of AgNP oxidants (such as H₂O₂ and organic radicals) will further enhance the rate and extent of oxidant generation by AgCl(s).

Occurrence, characterisation and fate of (nano)particulate Ti and Ag in two Norwegian wastewater treatment plants

Due to their widespread application in consumer products, elemental titanium (e.g., titanium dioxide, TiO₂) and silver (Ag), also in nanoparticulate form, are increasingly released from households and industrial facilities to urban wastewater treatment plants (WWTPs). A seven-day sampling campaign was conducted in two full-scale WWTPs in Trondheim (Norway) employing only primary treatment. We assessed the occurrence and elimination of Ti and Ag, and conducted size-based fractionation using sequential filtration of influent samples to separate particulate, colloidal and dissolved fractions. Eight-hour composite influent samples were collected to assess diurnal variations in total Ti and Ag influx. Measured influent Ti concentrations (up to 290 μg L^-1) were significantly higher than Ag (<0.15-2.1 μg L^-1), being mostly associated with suspended solids (>0.7 μm). Removal efficiencies ≥70% were observed for both elements, requiring for one WWTP to account for the high Ti content (∼2 g L^-1) in the flocculant. Nano- and micron-sized Ti particles were observed with scanning transmission electron microscopy (STEM) in influent, effluent and biosolids, while Ag nanoparticles were detected in biosolids only. Diurnal profiles of influent Ti were correlated to flow and pollutant concentration patterns (especially total suspended solids), with peaks during the morning and/or evening and minima at night, indicating household discharges as predominant source. Irregular profiles were exhibited by influent Ag, with periodic concentration spikes suggesting short-term discharges from one or few point sources (e.g., industry). Influent Ti and Ag dynamics were reproduced using a disturbance scenario generator model, and we estimated per capita loads of Ti (42-45 mg cap^-1 d^-1) and Ag (0.11 mg cap^-1 d^-1) from households as well as additional Ag load (14-22 g d^-1) from point discharge. This is the first study to experimentally and mathematically describe short-term release dynamics and dry-weather sources of emissions of Ti and Ag in municipal WWTPs and receiving environments.

Miniaturized liquid chromatography coupled on-line to in-tube solid-phase microextraction for characterization of metallic nanoparticles using plasmonic measurements. A tutorial

This tutorial aims at providing guidelines for analyzing metallic nanoparticles (NPs) and their dispersions by using methods based on miniaturized liquid chromatography with diode array detection (MinLC-DAD) and coupled on-line to in-tube solid-phase microextraction (IT-SPME). Some practical advice and considerations are given for obtaining reliable results. In addition, this work outlines the potential applications that set these methodologies apart from microscopy-related techniques, dynamic light scattering, single particle ICP-MS, capillary electrophoresis, field-flow fractionation and other chromatographic configurations, which are discussed and mainly seek to accomplish size estimation and NP separation, speciation analysis and quantification of mainly AgNPs and AuNPs. MinLC-DAD has the potential to estimate the NP concentration and from it the average size of unknown samples by calibrating with a single standard, as well as studying potentially non-spherical particles and stability-related properties of their dispersions. While keeping the signal dependency with concentration and increasing the method sensitivity, IT-SPME-MinLC-DAD goes further allowing for the assessment of the dispersant effect and ultimately changes in the nanoparticle surroundings that range from modifications of the hydrodynamic diameter to the exposure to different reagents and matrices. The methodology can still be improved by either exploring newer IT-SPME adsorbents or by assaying new system configurations. Taking into account that this technique gives complementary information in relation to other techniques discussed here, this tutorial serves as a guide for analyzing metallic NPs towards a better understanding of the particle behavior under different scenarios.

Assessing the release of copper from nanocopper-treated and conventional copper-treated lumber into marine waters I: Concentrations and rates

Little is known about the release of metal engineered nanomaterials (ENMs) from consumer goods, including lumber treated with micronized copper. Micronized copper is a recent form of antifouling wood preservative containing nanosized copper particles for use in pressure-treated lumber. The present study investigated the concentrations released and the release rate of total copper over the course of 133 d under freshwater, estuarine, and marine salinity conditions (0, 1, 10, and 30‰) for several commercially available pressure-treated lumbers: micronized copper azole (MCA) at 0.96 and 2.4 kg/m3 , alkaline copper quaternary (ACQ) at 0.30 and 9.6 kg/m3 , and chromated copper arsenate (CCA) at 40 kg/m3 . Lumber was tested as blocks and as sawdust. Overall, copper was released from all treated lumber samples. Under leaching conditions, total release ranged from 2 to 55% of the measured copper originally in the lumber, with release rate constants from the blocks of 0.03 to 2.71 (units per day). Generally, measured release and modeled equilibrium concentrations were significantly higher in the estuarine conditions compared with freshwater or marine salinities, whereas rate constants showed very limited differences between salinities. Furthermore, organic carbon was released during the leaching and demonstrated a significant relationship with released copper concentrations as a function of salinity. The results indicate that copper is released into estuarine/marine waters from multiple wood treatments including lumber amended with nanoparticle-sized copper. Environ Toxicol Chem 2018;37:1956-1968. Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Shifts of system performance and microbial community structure in a constructed wetland after exposing silver nanoparticles

The increasing utilization of silver nanoparticles (Ag NPs) in industry and commerce inevitably raises its release into wastewater. In this work, effects of Ag NPs on system performance and microbial community along the way of a vertical flow constructed wetland (VFCW) were investigated, along with the removal and fate of Ag NPs within the system. Results showed that the performance of control wetland kept stable during the experimental period, and the top substrate layer (soil layer) of wetland could remove most of pollutants in the influent. The study also suggested that addition of Ag NPs did not significantly affect organic matters removal. However, adverse effects were observed on the nitrogen and phosphorus removal. Removal efficiencies of TN, NH₄⁺-N and TP approximately obviously reduced by approximately 10.10%, 8.42% and 28.35% respectively in contrast to before dosing after exposing 100 μg/L Ag NPs for 94 d, while the no dosing wetland with the stable performance. It was found that Ag NPs accumulated in the upper soil layer more than in the lower soil layer, and Ag NPs could enter into the plant tissues. After continuous input of Ag NPs, removal efficiency of Ag NPs was measured as 95.72%, which showed that the CW could effectively remove Ag NPs from the wastewater. The high-throughput sequencing results revealed that Ag NPs caused the shifts in microbial community structures and changed the relative abundances of key functional bacteria, which finally resulted in a lower efficiency of biological nitrogen and phosphorus removal.

A review of the fate of engineered nanomaterials in municipal solid waste streams

Significant knowledge and data gaps associated with the fate of product-embedded engineered nanomaterials (ENMs) in waste management processes exist that limit our current ability to develop appropriate end-of-life management strategies. This review paper was developed as part of the activities of the IWWG ENMs in Waste Task Group. The specific objectives of this review paper are to assess the current knowledge associated with the fate of ENMs in commonly used waste management processes, including key processes and mechanisms associated with ENM fate and transport in each waste management process, and to use that information to identify the data gaps and research needs in this area. Literature associated with the fate of ENMs in wastes was reviewed and summarized. Overall, results from this literature review indicate a need for continued research in this area. No work has been conducted to quantify ENMs present in discarded materials and an understanding of ENM release from consumer products under conditions representative of those found in relevant waste management process is needed. Results also indicate that significant knowledge gaps associated with ENM behaviour exist for each waste management process investigated. There is a need for additional research investigating the fate of different types of ENMs at larger concentration ranges with different surface chemistries. Understanding how changes in treatment process operation may influence ENM fate is also needed. A series of specific research questions associated with the fate of ENMs during the management of ENM-containing wastes have been identified and used to direct future research in this area.

Real-time monitoring of the Trojan-horse effect of silver nanoparticles by using a genetically encoded fluorescent cell sensor

Silver nanoparticles (AgNPs) are widely incorporated into commercial products due to their antimicrobial properties. As a consequence, concerns about the adverse effects induced by AgNPs to humans and the environment need to be carefully examined. The existing literature reveals that AgNPs exhibit certain toxic effects, but it remains to be proved whether AgNPs or the ionic silver (Ag+) released from AgNPs are the main toxic species. Here, a genetically encoded fluorescent protein sensor with high affinity to Ag+ was developed. The resulting sensor, MT2a-FRET, was found to be ratiometric, sensitive and selective toward only Ag+ but inert against AgNPs. This makes this sensor a potential useful tool for monitoring the real-time intracellular dissolutions of AgNPs. Our data supported that AgNPs display the "Trojan-horse" mechanism, where AgNPs are internalized by cells and undergo dissolution intracellularly. We further found that cells exhibited a detoxification ability to remove active Ag+ from cells in 48 hours.

Speciation evolution of zinc and copper during pyrolysis and hydrothermal carbonization treatments of sewage sludges

Thermal and hydrothermal treatments are promising techniques for sewage sludge management that can potentially facilitate safe waste disposal, energy recovery, and nutrient recovery/recycling. Content and speciation of heavy metals in the treatment products affect the potential environmental risks upon sludge disposal and/or application of the treatment products. Therefore, it is important to study the speciation transformation of heavy metals and the effects of treatment conditions. By combining synchrotron X-ray spectroscopy/microscopy analysis and sequential chemical extraction, this study systematically characterized the speciation of Zn and Cu in municipal sewage sludges and their chars derived from pyrolysis (a representative thermal treatment technique) and hydrothermal carbonization (HTC; a representative hydrothermal treatment technique). Spectroscopy analysis revealed enhanced sulfidation of Zn and Cu by anaerobic digestion and HTC treatments, as compared to desulfidation by pyrolysis. Overall, changes in the chemical speciation and matrix properties led to reduced mobility of Zn and Cu in the treatment products. These results provide insights into the reaction mechanisms during pyrolysis and HTC treatments of sludges and can help evaluate the environmental/health risks associated with the metals in the treatment products.

Nanoparticles in the environment: where do we come from, where do we go to?

Nanoparticles serve various industrial and domestic purposes which is reflected in their steadily increasing production volume. This economic success comes along with their presence in the environment and the risk of potentially adverse effects in natural systems. Over the last decade, substantial progress regarding the understanding of sources, fate, and effects of nanoparticles has been made. Predictions of environmental concentrations based on modelling approaches could recently be confirmed by measured concentrations in the field. Nonetheless, analytical techniques are, as covered elsewhere, still under development to more efficiently and reliably characterize and quantify nanoparticles, as well as to detect them in complex environmental matrixes. Simultaneously, the effects of nanoparticles on aquatic and terrestrial systems have received increasing attention. While the debate on the relevance of nanoparticle-released metal ions for their toxicity is still ongoing, it is a re-occurring phenomenon that inert nanoparticles are able to interact with biota through physical pathways such as biological surface coating. This among others interferes with the growth and behaviour of exposed organisms. Moreover, co-occurring contaminants interact with nanoparticles. There is multiple evidence suggesting nanoparticles as a sink for organic and inorganic co-contaminants. On the other hand, in the presence of nanoparticles, repeatedly an elevated effect on the test species induced by the co-contaminants has been reported. In this paper, we highlight recent achievements in the field of nano-ecotoxicology in both aquatic and terrestrial systems but also refer to substantial gaps that require further attention in the future.

Life span-resolved nanotoxicology enables identification of age-associated neuromuscular vulnerabilities in the nematode Caenorhabditis elegans

At present, the majority of investigations concerning nanotoxicology in the nematode C. elegans address short-term effects. While this approach allows for the identification of uptake pathways, exposition and acute toxicity, nanoparticle-organism interactions that manifest later in the adult life of C. elegans are missed. Here we show that a microhabitat composed of liquid S-medium and live bacteria in microtiter wells prolongs C. elegans longevity and is optimally suited to monitor chronic eNP-effects over the entire life span (about 34 days) of the nematode. Silver (Ag) nanoparticles reduced C. elegans life span in concentrations ≥10 μg/mL, whereas nano ZnO and CeO₂ (1-160 μg/mL) had no effect on longevity. Monitoring of locomotion behaviors throughout the entire life span of C. elegans showed that Ag NPs accelerate the age-associated decline of swimming and increase of uncoordinated movements at concentrations of ≥10 μg/mL, whereas neuromuscular defects did not occur in response to ZnO and CeO₂ NPs. By means of a fluorescing reporter worm expressing tryptophan hydroxylase-1::DsRed Ag NP-induced behavioral defects were correlated to axonal protein aggregation and neurodegeneration in single serotonergic HSN as well as sensory ADF neurons. Notably, serotonergic ADF neurons represented a sensitive target for Ag NPs in comparison to GABAergic neurons that showed no signs of degeneration under the same conditions. We conclude that due to its analogy to the jellylike boom culture of C. elegans on microbe-rich rotting plant material liquid S-medium culture in spatially confined microtiter wells represents a relevant as well as practical tool for comparative identification of age-resolved nanoparticle effects and vulnerabilities in a significant target organism. Consistent with this, specifically middle-aged nematodes showed premature neuromuscular defects after Ag NP-exposure.

Impact of a Model Soil Microorganism and of Its Secretome on the Fate of Silver Nanoparticles

Sulfidation is a key process for silver nanoparticles released from consumer products in the environment. This study focuses on the impact of a model soil microorganism, Bacillus subtilis, on the fate of pristine and already sulfidized Ag-NPs. The nanoparticles were incubated with the initial growth medium, isolated secretome, and living bacteria, and characterized for their size and morphology, agglomeration state, structure, and Ag speciation. No Ag internalization or sorption on the cell wall was detected. A partial sulfidation, leading to an Ag-Ag₂S core-shell structure, was observed in the presence of the secretome, and the rate limiting step of the reaction was the oxidation of Ag⁰, and it was favored near the crystal dislocations. The sulfidation was complete in the presence of the living bacteria and followed an indirect pathway. Both crystalline Ag₂S and amorphous Ag₂S and/or Ag-thiol were identified. At the opposite, the bacteria had no impact on Ag₂S. These results suggest that microorganisms participate in the sulfidation of Ag-NPs in aerobic systems such as unsaturated soils, and thus affect the bioavailability of Ag. It is important to take these transformations into account during exposure experiments, since they drastically change the exposure conditions. Finally, the secretome of B. subtilis might be used for the green synthesis of Ag-Ag₂S core-shell nanoparticles.

Multi-functional wool fabrics by graft-copolymerisation with polystyrene sulphonate: their enhanced fire retardancy, mechanical properties, and stain-resistance

pSS-Grafted wool fabrics showed enhanced fire retardancy, tensile strength and stain-resistance against an acid dye-based stain.

Impacts of silver nanoparticles on the nutrient removal and functional bacterial community in vertical subsurface flow constructed wetlands

The widespread utilization of silver nanoparticles (AgNPs) in industrial and commercial products inevitably raises the release into wastewater. In this study, the influences of AgNPs (0, 50 and 200μg/L) on the performance and microbial community of CWs were evaluated. Compared with the control system (without AgNPs), the COD removal was not affected, whereas the TN, NH₄⁺-N, and TP removals were evidently affected in presence of AgNPs, and the effects had a positive relation with AgNPs concentration. In addition, AgNPs were effectively removed from wastewater and mainly accumulated in the soil layer and plant tissues. The illumina high-throughput sequencing results indicated that there were obvious variations in the microbial community at different AgNPs concentrations, associated with the variations of CW performance. Sequencing analyses also showed that Proteobacteria, Acidobacteria, Bacteroidetes were the dominant phyla. These results may provide valuable information and reference for evaluating the effect of AgNPs on constructed wetlands.

Transport, retention, and long-term release behavior of polymer-coated silver nanoparticles in saturated quartz sand: The impact of natural organic matters and electrolyte

This study investigated the transport and long-term release of stabilized silver nanoparticles (AgNPs), including polyvinylpyrrolidone-coated AgNPs (PVP-AgNPs) and bare AgNPs (Bare-AgNPs), in the presence of natural organic matters (NOMs; both humic acids (HA) and alginate (Alg)) and an electrolyte (Ca²⁺) in a sand-packed column. Very low breakthrough rate (C/C₀) of AgNPs (below 0.04) occurred in the absence of NOM and the electrolyte. Increasing the concentration of NOM and decreasing the influent NOM solution's ionic strength (IS) reduced the retention of AgNPs. The reduced NP retention at high NOM and low IS was mainly attributed to the increased energy barrier between the AgNPs and the sand grain surface. Notably, the retention of PVP-AgNPs was enhanced at high Alg concentration and low IS, which mainly resulted from the improved hydrophobicity that could increase the interaction between the PVP-AgNPs and the collector. The total release amount of PVP-AgNPs (10.03%, 9.50%, 28.42%, 6.37%) and Bare-AgNPs (3.28%, 2.58%, 10.36%, 1.54%) were gained when exposed to four kinds of NOM solutions, including deionized water, an electrolyte solution (1 mM Ca²⁺), HA with an electrolyte (1 mM Ca²⁺), and a Alg (40 mg/L) solution with an electrolyte (1 mM Ca²⁺). The long-term release of retained silver nanoparticles in the quartz sand was mostly through the form of released Ag NPs. The factors that increased the mobility of AgNPs in quartz sand could improve the release of the AgNPs. The release of AgNPs had no significant change in the presence Ca²⁺ but were increased in the presence of HA. The Alg slightly decreased the release of AgNPs by increasing the hydrophobicity of AgNPs. The results of the study indicated that all the tested NOM and Ca²⁺ have prominent influence on the transport and long-term release behavior of silver nanoparticles in saturated quartz sand.

The acute toxic effects of silver nanoparticles on myocardial transmembrane potential, INa and IK1 channels and heart rhythm in mice

This study focused on the potential toxicity of silver nanoparticles (AgNPs) on cardiac electrophysiology which is rarely investigated. We found that AgNPs (10^-9-10^-6g/ml) concentration-dependently depolarized the resting potential, diminished the action potential, and finally led to loss of excitability in mice cardiac papillary muscle cells in vitro. In cultured neonatal mice cardiomyocytes, AgNPs (10^-9-10^-7g/ml) concentration-dependently decreased the Na⁺ currents (I_Na), accelerated the activation, and delayed the inactivation and recovery of Na⁺ channels from inactivation within 5 min. AgNPs at 10^-8g/ml also rapidly decreased the inwardly rectifying K⁺ currents (I_K1) and delayed the activation of I_K1 channels. Intravenous injection of AgNPs at 3 mg/kg only decreased the heart rate, while at ≥4 mg/kg sequentially induced sinus bradycardia, complete atrio-ventricular conduction block, and cardiac asystole. AgNPs at 10^-10-10^-6g/ml did not increase reactive oxygen species (ROS) generation and only at 10^-6g/ml mildly induced lactate dehydrogenase (LDH) release in the cardiomyocytes within 5 min. Endocytosis of AgNPs by cardiomyocytes was not observed within 5 min, but was observed 1 h after exposing to AgNPs. Comparative Ag⁺ (≤0.02% of the AgNPs) could not induce above toxicities. We conclude that AgNPs exert rapid toxic effects on myocardial electrophysiology and induce lethal bradyarrhythmias. These acute toxicities are likely due to direct effects of AgNPs on ion channels at the nano-scale level, but not caused by Ag⁺, ROS, and membrane injury. These findings provide warning to the nanomedical practice using AgNPs.

Airborne Nanoparticle Release and Toxicological Risk from Metal-Oxide-Coated Textiles: Toward a Multiscale Safe-by-Design Approach

Nano metal oxides have been proposed as alternatives to silver (Ag) nanoparticles (NPs) for antibacterial coatings. Here, cotton and polyester-cotton fabrics were sonochemically coated with zinc oxide (ZnO) and copper oxide (CuO) NPs. By varying the reaction solvent (water or ethanol), NPs with different sizes and shapes were synthesized. The cytotoxic and pro-inflammatory effects of studied NPs were investigated in vitro in human alveolar epithelial A549 and macrophage-like THP1 cells. To understand the potential respiratory impact of the NPs, the coated textiles were subjected to the abrasion tests, and the released airborne particles were measured. A very small amount of the studied metal oxides NPs was released from abrasion of the textiles coated by the ethanol-based sonochemical process. The release from the water-based coating was comparably higher. Lung and immune cells viability decreased after 24 h of exposure only at the highest studied NPs concentration (100 μg/mL). Different from the ZnO NPs, both formulations of CuO NPs induced IL-8 release in the lung epithelial cells already at subtoxic concentrations (1-10 μg/mL) but not in immune cells. All of the studied NPs did not induce IL-6 release by the lung and immune cells. Calculations revealed that the exposures of the NPs to human lung due to the abrasion of the textiles were lower or comparable to the minimum doses in the cell viability tests (0.1 μg/mL), at which acute cytotoxicity was not observed. The results alleviate the concerns regarding the potential risk of these metal oxide NPs in their applications for the textile coating and provide insight for the safe-by-design approach.

Oral Exposure to Silver Nanoparticles or Silver Ions May Aggravate Fatty Liver Disease in Overweight Mice

As the applications and environmental release of silver ions and nanoparticles are increasing, increasing human exposure to these pollutants has become an emerging health concern. The impeding effects of such pollutants on susceptible populations are severely under-studied. Here, we demonstrate that silver nanoparticles (Ag NPs), at a dose that causes no general toxicity in normal mice, promotes the progression of fatty liver disease from steatosis to steatohepatitis only in overweight mice. Exposure to Ag⁺ ions induces the same effects in overweight mice. Ag NPs rather than Ag⁺ ions cause this disease progression based on our findings that Ag⁺ ions are partly reduced to Ag NPs in fatty livers, and the toxic effect is correlated with the liver dose of Ag NPs, not Ag⁺ ions. Furthermore, the Ag NP-induced pro-inflammatory activation of Kupffer cells in the liver, enhancement of hepatic inflammation, and suppression of fatty acid oxidation are identified as key factors in the underlying mechanisms.

Quantification and size characterisation of silver nanoparticles in environmental aqueous samples and consumer products by single particle-ICPMS

Single particle-inductively coupled plasma mass spectrometry (SP-ICPMS) is a promising technique able to generate the number based-particle size distribution (PSD) of nanoparticles (NPs) in aqueous suspensions. However, SP-ICPMS analysis is not consolidated as routine-technique yet and is not typically applied to real test samples with unknown composition. This work presents a methodology to detect, quantify and characterise the number-based PSD of Ag-NPs in different environmental aqueous samples (drinking and lake waters), aqueous samples derived from migration tests and consumer products using SP-ICPMS. The procedure is built from a pragmatic view and involves the analysis of serial dilutions of the original sample until no variation in the measured size values is observed while keeping particle counts proportional to the dilution applied. After evaluation of the analytical figures of merit, the SP-ICPMS method exhibited excellent linearity (r²>0.999) in the range (1-25) × 10⁴ particlesmL^-1 for 30, 50 and 80nm nominal size Ag-NPs standards. The precision in terms of repeatability was studied according to the RSDs of the measured size and particle number concentration values and a t-test (p = 95%) at the two intermediate concentration levels was applied to determine the bias of SP-ICPMS size values compared to reference values. The method showed good repeatability and an overall acceptable bias in the studied concentration range. The experimental minimum detectable size for Ag-NPs ranged between 12 and 15nm. Additionally, results derived from direct SP-ICPMS analysis were compared to the results conducted for fractions collected by asymmetric flow-field flow fractionation and supernatant fractions after centrifugal filtration. The method has been successfully applied to determine the presence of Ag-NPs in: lake water; tap water; tap water filtered by a filter jar; seven different liquid silver-based consumer products; and migration solutions (pure water and sweat simulant) from plasters. Results obtained by SP-ICPMS were supported by transmission electron microscopy and energy dispersive spectroscopy characterisation, suggesting that the proposed methodology can be applied as a positive screening test in the simultaneous quantification and size characterisation of Ag-NPs in samples of environmental interest.

Polyester Textiles as a Source of Microplastics from Households: A Mechanistic Study to Understand Microfiber Release During Washing

Microplastic fibers make up a large proportion of microplastics found in the environment, especially in urban areas. There is good reason to consider synthetic textiles a major source of microplastic fibers, and it will not diminish since the use of synthetic fabrics, especially polyester, continues to increase. In this study we provide quantitative data regarding the size and mass of microplastic fibers released from synthetic (polyester) textiles during simulated home washing under controlled laboratory conditions. Consideration of fabric structure and washing conditions (use of detergents, temperature, wash duration, and sequential washings) allowed us to study the propensity of fiber shedding in a mechanistic way. Thousands of individual fibers were measured (number, length) from each wash solution to provide a robust data set on which to draw conclusions. Among all the variables tested, the use of detergent appeared to affect the total mass of fibers released the most, yet the detergent composition (liquid or powder) or overdosing of detergent did not significantly influence microplastic release. Despite different release quantities due to the addition of a surfactant (approximately 0.025 and 0.1 mg fibers/g textile washed, without and with detergent, respectively), the overall microplastic fiber length profile remained similar regardless of wash condition or fabric structure, with the vast majority of fibers ranging between 100 and 800 μm in length irrespective of wash cycle number. This indicates that the fiber staple length and/or debris encapsulated inside the fabric from the yarn spinning could be directly responsible for releasing stray fibers. This study serves as a first look toward understanding the physical properties of the textile itself to better understand the mechanisms of fiber shedding in the context of microplastic fiber release into laundry wash water.

Life Cycle Assessment and Release Studies for 15 Nanosilver-Enabled Consumer Products: Investigating Hotspots and Patterns of Contribution

Increasing use of silver nanoparticles (AgNPs) in consumer products as antimicrobial agents has prompted extensive research toward the evaluation of their potential release to the environment and subsequent ecotoxicity to aquatic organisms. It has also been shown that AgNPs can pose significant burdens to the environment from life cycle emissions associated with their production, but these impacts must be considered in the context of actual products that contain nanosilver. Here, a cradle-to-gate life cycle assessment for the production of 15 different AgNP-enabled consumer products was performed, coupled with release studies of those same products, thus providing a consistent analytical platform for investigation of potential nanosilver impacts across a range of product types and concentrations. Environmental burdens were assessed over multiple impact categories defined by the United States Environmental Protection Agency's Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI 2.1) method. Depending on the product composition and silver loading, the contribution of AgNP synthesis to the overall impacts was seen to vary over a wide range from 1% to 99%. Release studies found that solid polymeric samples lost more silver during wash compared to fibrous materials. Estimates of direct ecotoxicity impacts of AgNP releases from those products with the highest leaching rates resulted in lower impact levels compared to cradle-to-gate ecotoxicity from production for those products. Considering both cradle-to-gate production impacts and nanoparticle release studies, in conjunction with estimates of life cycle environmental and health benefits of nanoparticle incorporation, can inform sustainable nanoenabled product design.

Catalytic role of iron in the formation of silver nanoparticles in photo-irradiated Ag+-dissolved organic matter solution

Photo-reduction of Ag⁺ to silver nanoparticle (AgNPs) by dissolved organic matter (DOM) is a possible source of naturally occurring AgNPs. However, how this photo-reduction process is influenced by ubiquitous metal ions is still not well understood. In addition, in previous studies, the formation of AgNPs in DOM solution was usually monitored by UV-Vis spectroscopy, and there is still lack of quantitative analysis for the formed AgNPs. In the present study, the role of Fe²⁺/Fe³⁺ at environmental concentration level on this photochemical process was investigated, and the enhanced formation of AgNPs by Fe²⁺/Fe³⁺ was probed and quantified by using UV-Vis spectroscopy, transmission electron microscopy, and liquid chromatography-inductively coupled plasma mass spectrometry. It was demonstrated that while Fe³⁺ can oxidize AgNPs to release Ag⁺, Fe²⁺ can reduce Ag⁺ into AgNPs. However, the DOM-induced reduction of Fe³⁺ makes iron an effective electron shuttle between DOM and Ag⁺, and both Fe²⁺ and Fe³⁺ enhanced AgNP formation. The impacts of environmentally relevant factors, including DOM concentration and solution pH, on this process were studied comprehensively, which showed that the catalytic role of iron was more significant at higher DOM concentration and lower pH. This iron-enhanced formation of AgNPs in photo-irradiated Ag⁺-DOM solution have great environmental implications on the formation of natural AgNPs and the transformation of engineered AgNPs in acidic surface water with high iron content.

Dual-Functional Polyethylene Glycol-b-polyhexanide Surface Coating with in Vitro and in Vivo Antimicrobial and Antifouling Activities

In recent years, microbial colonization on the surface of biomedical implants/devices has become a severe threat to human health. Herein, surface-immobilized guanidine derivative block copolymers create an antimicrobial and antifouling dual-functional coating. We report the preparation of an antimicrobial and antifouling block copolymer by the conjugation of polyhexanide (PHMB) with either allyl glycidyl ether or allyloxy polyethylene glycol (APEG; MW 1200 and 2400). The allyl glycidyl ether modified PHMB (A-PHMB) and allyloxy polyethylene glycol_1200/2400 modified PHMB (APEG_1200/2400-PHMB) copolymers were grafted onto a silicone rubber surface as a bottlebrush-like coating, respectively, using a plasma-UV-assisted surface-initiated polymerization. Both A-PHMB and APEG_1200/2400-PHMB coatings exhibited excellent broad-spectrum antimicrobial properties against Gram-negative/positive bacteria and fungi. The APEG₂₄₀₀-PHMB coating displayed an improved antibiofilm as well as antifouling properties and a long reusable cycle, compared with two other coatings, due to its abundant PEG blocks among those copolymers. Also, the APEG₂₄₀₀-PHMB-coated silicone coupons were biocompatible toward mammalian cells, as revealed by in vitro hemocompatibile and cytotoxic assays. An in vivo study showed a significant decline of Escherichia coli colonies with a 5-log reduction, indicating the APEG₂₄₀₀-PHMB coating surface worked effectively in the rodent subcutaneous infection model. This PHMB-based block copolymer coating is believed to be an effective strategy to prevent biomaterial-associated infections.

Microplastic Exposure Assessment in Aquatic Environments: Learning from Similarities and Differences to Engineered Nanoparticles

Microplastics (MPs) have been identified as contaminants of emerging concern in aquatic environments and research into their behavior and fate has been sharply increasing in recent years. Nevertheless, significant gaps remain in our understanding of several crucial aspects of MP exposure and risk assessment, including the quantification of emissions, dominant fate processes, types of analytical tools required for characterization and monitoring, and adequate laboratory protocols for analysis and hazard testing. This Feature aims at identifying transferrable knowledge and experience from engineered nanoparticle (ENP) exposure assessment. This is achieved by comparing ENP and MPs based on their similarities as particulate contaminants, whereas critically discussing specific differences. We also highlight the most pressing research priorities to support an efficient development of tools and methods for MPs environmental risk assessment.

Silver Nanoparticles: Technological Advances, Societal Impacts, and Metrological Challenges

Silver nanoparticles (AgNPs) show different physical and chemical properties compared to their macroscale analogs. This is primarily due to their small size and, consequently, the exceptional surface area of these materials. Presently, advances in the synthesis, stabilization, and production of AgNPs have fostered a new generation of commercial products and intensified scientific investigation within the nanotechnology field. The use of AgNPs in commercial products is increasing and impacts on the environment and human health are largely unknown. This article discusses advances in AgNP production and presents an overview of the commercial, societal, and environmental impacts of this emerging nanoparticle (NP), and nanomaterials in general. Finally, we examine the challenges associated with AgNP characterization, discuss the importance of the development of NP reference materials (RMs) and explore their role as a metrological mechanism to improve the quality and comparability of NP measurements.

The need for a life-cycle based aging paradigm for nanomaterials: importance of real-world test systems to identify realistic particle transformations

Assessing the risks of manufactured nanomaterials (MNM) has been almost exclusively focused on the pristine, as-produced materials with far fewer studies delving into more complex, real world scenarios. However, when considering a life-cycle perspective, it is clear that MNM released from commercial products during manufacturing, use and disposal are far more relevant both in terms of more realistic environmental fate and transport as well as environmental risk. The quantity in which the particles are released and their (altered) physical and chemical form should be identified and it is these metrics that should be used to assess the exposure and hazard the materials pose. The goal of this review is to (1) provide a rationale for using a life-cycle based approach when dealing with MNM transformations, (2) to elucidate the different chemical and physical forces which age and transform MNM and (3) assess the pros and cons of current analytical techniques as they pertain to the measurement of aged and transformed MNM in these complex release scenarios. Specifically, we will describe the possible transformations common MNM may undergo during the use or disposal of nano-products based on how these products will be used by the consumer by taking stock of the current nano-enabled products on the market. Understanding the impact of these transformations may help forecast the benefits and/or risks associated with the use of products containing MNM.

Probabilistic approach for assessing infants' health risks due to ingestion of nanoscale silver released from consumer products

Silver nanoparticles (n-Ag) are widely used in consumer products and many medical applications because of their unique antibacterial properties. Their use is raising concern about potential human exposures and health effects. Therefore, it is informative to assess the potential human health risks of n-Ag in order to ensure that nanotechnology-based consumer products are deployed in a safe and sustainable way. Even though toxicity studies clearly show the potential hazard of n-Ag, there have been few attempts to integrate hazard and exposure assessments to evaluate risks. The underlying reason for this is the difficulty in characterizing exposure and the lack of toxicity studies essential for human health risk assessment (HHRA). Such data gaps introduce significant uncertainty into the risk assessment process. This study uses probabilistic methods to assess the relative uncertainty and potential risks of n-Ag exposure to infants. In this paper, we estimate the risks for infants potentially exposed to n-Ag through drinking juice or milk from sippy cups or licking baby blankets containing n-Ag. We explicitly evaluate uncertainty and variability contained in available dose-response and exposure data in order to make the risk characterization process transparent. Our results showed that individual margin of exposures for oral exposure to sippy cups and baby blankets containing n-Ag exhibited minimal risk.