Toxicity and accumulation of silver nanoparticles during development of the marine polychaete Platynereis dumerilii

Antidepressant pharmaceuticals in aquatic systems, individual-level ecotoxicological effects: growth, survival and behavior

The growing consumption of antidepressant pharmaceuticals has resulted in their widespread occurrence in the environment, particularly in waterways with a typical concentration range from ng L^-1 to μg L^-1. An increasing number of studies have confirmed the ecotoxic potency of antidepressants, not only at high concentrations but also at environmentally relevant levels. The present review covers literature from the last decade on the individual-level ecotoxicological effects of the most commonly used antidepressants, including their impact on behavior, growth, and survival. We focus on the relationship between antidepressants physico-chemical properties and dynamics in the environment. Furthermore, we discuss the advantages of considering behavioral changes as sensitive endpoints in ecotoxicology, as well as some current methodological shortcomings in the field, including low standardization, reproducibility and context-dependency.

The Nereid on the rise: Platynereis as a model system

The Nereid Platynereis dumerilii (Audouin and Milne Edwards (Annales des Sciences Naturelles 1:195-269, 1833) is a marine annelid that belongs to the Nereididae, a family of errant polychaete worms. The Nereid shows a pelago-benthic life cycle: as a general characteristic for the superphylum of Lophotrochozoa/Spiralia, it has spirally cleaving embryos developing into swimming trochophore larvae. The larvae then metamorphose into benthic worms living in self-spun tubes on macroalgae. Platynereis is used as a model for genetics, regeneration, reproduction biology, development, evolution, chronobiology, neurobiology, ecology, ecotoxicology, and most recently also for connectomics and single-cell genomics. Research on the Nereid started with studies on eye development and spiralian embryogenesis in the nineteenth and early twentieth centuries. Transitioning into the molecular era, Platynereis research focused on posterior growth and regeneration, neuroendocrinology, circadian and lunar cycles, fertilization, and oocyte maturation. Other work covered segmentation, photoreceptors and other sensory cells, nephridia, and population dynamics. Most recently, the unique advantages of the Nereid young worm for whole-body volume electron microscopy and single-cell sequencing became apparent, enabling the tracing of all neurons in its rope-ladder-like central nervous system, and the construction of multimodal cellular atlases. Here, we provide an overview of current topics and methodologies for P. dumerilii, with the aim of stimulating further interest into our unique model and expanding the active and vibrant Platynereis community.

The protective role of vitamins (E + C) on Nile tilapia (Oreochromis niloticus) exposed to ZnO NPs and Zn ions: Bioaccumulation and proximate chemical composition

The accumulation potency of zinc nanoparticles in Nile tilapia (Oreochromis niloticus) were previously studied but their impacts on proximate chemical composition in muscle tissue by describing the dose-dependent accumulation and the protective role of vitamins (E + C), have not been investigated. Therefore, this study was carried out to assess the protective role of vitamins (E + C) on Zn accumulation in muscle and gill tissues of O. niloticus exposed to three sublethal concentrations (1/8 LC50, 1/4 LC50, and 1/2 LC50) of zinc oxide nanoparticles (ZnO NPs) compared to zinc oxide bulk particles (ZnO BPs) as well as their effects on the induced chemical composition alterations for different experimental periods (7, 14, 21, and 28 day). The data displayed that fish exposed to the different sublethal concentrations of ZnO NPs or ZnO BPs have a significant increase (p<0.05) in Zn ions accumulation in muscle and gill tissues compared to control group but Zn was accumulated in gill tissue higher than muscle tissue at all exposure periods. Also, Zn accumulation was higher in fish tissues exposed to ZnO NPs than ZnO BPs. On the other hand, groups supplemented with vitamins (E + C) showed a significant decreasing (p<0.05) in accumulated Zn levels compared to groups without supplementation. The values of these supplemented groups returned to similar levels established in the control at low concentrations but still higher than control at the high concentrations. Furthermore, the results showed that moisture and ash content slightly increased while protein and fat decreased in fish exposed to ZnO NPs or ZnO BPs compared to control group. In conclusion, the findings supported that a combination of vitamins (E + C) reduced Zn accumulation and ameliorated chemical composition alterations in O.niloticus fish.

AF4-UV-ICP-MS for detection and quantification of silver nanoparticles in seafood after enzymatic hydrolysis

A method based on asymmetric flow field-flow fractionation (AF4) coupled to ultraviolet-visible (UV-vis) spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS) has been developed for silver nanoparticles (Ag NPs) detection and quantification in bivalve molluscs. Samples were pre-treated using a conventional enzymatic (pancreatin and lipase) hydrolysis procedure (37 °C, 12 h). AF4 was performed using a regenerated cellulose (RC) membrane (10 kDa, 350 μm spacer) and aqueous 5 mM Tris-HCl pH = 7.4 as carrier. AF4 separation was achieved with a program that included a focusing step with tip and focus flows of 0.20 and 3.0 mL min^-1, respectively, and an injection time of 4.0 min. Elution of different size fractions was performed using a cross flow of 3.0 mL min^-1 for 15 min, followed by linear cross flow decrease for 7.5 min, and a washing step for 9.4 min with no cross flow. Several bivalve molluscs (clams, oysters and variegated scallops) were analysed for total Ag content (ICP-MS after microwave assisted acid digestion), and for Ag NPs by the method presented here. Results show that Ag NPs are detected at the same elution time than proteins (UV monitoring at 280 and 405 nm), which suggests a certain interaction occurred between Ag NPs with proteins in the enzymatic extracts. AF4-UV-ICP-MS fractograms also suggest different Ag NPs size distributions for selected samples. Membrane recoveries, determined by peak area comparison of fractograms with and without application of cross flow, were within the 49-121% range. Confirmation of the presence Ag NPs in the investigated enzymatic extracts was demonstrated by SEM after an oxidative pre-treatment based on hydrogen peroxide and microwave irradiation.

Do the graphene nanoflakes pose a potential threat to the polychaete Hediste diversicolor?

Graphene is a promising material with a wide range of future applications that could potentially lead to its transfer from numerous water and terrestrial sources to the sea, thus fate and effects of graphene in the marine ecosystem deserve attention. Within this work, the impact of the short- and long-term exposure (36 h and 24 days) of the marine benthic polychaete Hediste diversicolor to various concentrations (36 h: 0.4, 4, 40 and 400 mg L^-1; 24 days: 4 and 40 mg L^-1) of the pristine graphene multilayer nanoflakes (of thickness 8-12 nm) was investigated. Experiments revealed a limited toxic effect of graphene on H. diversicolor. Although the polychaetes ingested graphene, no impact on their total energy content was found. The toxic effect expressed by significant elevation of catalase activity indicating activation of defence mechanisms was recorded but only at the early stage of exposure. Activities of other antioxidant and cellular damage biomarkers (SOD, GST, GSH, MDA, CBO) remained unaffected. Moreover, no neurotoxic effect expressed by inhibition of acetylcholinesterase (AChE) activity was observed. Substantial inter-individual variability in the activities of some biomarkers at the end of the long-term experiment was found. Polychaetes were buried deeper in the sediment with graphene than in the controls indicating an escape reaction and avoidance behaviour. The latter may lead to the transfer of graphene from the sediment surface to deeper sediment layers with unknown consequences for the benthic ecosystem.

Sub-chronic effects of AgNPs and AuNPs on Gammarus fossarum (Crustacea Amphipoda): From molecular to behavioural responses

The aim of the present study was the assessment of the sub-chronic effects of silver (AgNPs) and gold nanoparticles (AuNPs) of 40 nm primary size either stabilised with citrate (CIT) or coated with polyethylene glycol (PEG) on the freshwater invertebrate Gammarus fossarum. Silver nitrate (AgNO₃) was used as a positive control in order to study the contribution of silver ions potentially released from AgNPs on the observed effects. A multibiomarker approach was used to assess the long-term effects of AgNPs and AuNPs 40 nm on molecular, cellular, physiological and behavioural responses of G. fossarum. Specimen of G. fossarum were exposed for 15 days to 0.5 and 5 µgL^-1 of CIT and PEG AgNPs and AuNPs 40 nm in the presence of food. A significant uptake of both Ag and Au was observed in exposed animals but was under the toxic threshold leading to mortality of G. fossarum. Silver nanoparticles (CIT-AgNPs and PEG-AgNPs 40 nm) led to an up-regulation of Na⁺K⁺ATPase gene expression. An up-regulation of Catalse and Chitinase gene expressions due to exposure to PEG-AgNPs 40 nm was also observed. Gold nanoparticles (CIT and PEG-AuNPs 40 nm) led to an increase of CuZnSOD gene expression. Furthermore, both AgNPs and AuNPs led to a more developed digestive lysosomal system indicating a general stress response in G. fossarum. Both AgNPs and AuNPs 40 nm significantly affected locomotor activity of G. fossarum while no effects were observed on haemolymphatic ions and ventilation.

Green Synthesis and Antibacterial Activity of HAp@Ag Nanocomposite Using Centella asiatica (L.) Urban Extract and Eggshell

In recent years, the green synthesis of nanoparticles via biological processes has attracted considerable attention. Herein, we introduce a facile and green approach for the synthesis of poriferous silver nanoparticles (Ag-NPs) decorated hydroxylapatite (HAp@Ag) nanoparticles with excellent antibacterial properties. All the nanocomposites were fully characterized in the solid state via various techniques such as X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectrometer (EDX), in which the synthesized Ag-NPs (24 nm in diameter) and their homogeneous incorporation on HAp have been studied by ultraviolet-visible (UV-vis) technique, transmission electron microscopy (TEM), and dynamic light scattering (DLS) analysis. The obtained results indicate that the structure and morphology of HAp have no significant changes after the incorporation of Ag-NPs on its surface. Moreover, an impressive antibacterial activity of HAp@Ag nanocomposite against Gram-positive bacterium Staphylococcus aureus and Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa has been recorded by using the agar well diffusion method. As a result, the HAp@Ag nanocomposite promises to be a great biomedical material with high antibacterial properties.

Engineered metal nanoparticles in the marine environment: A review of the effects on marine fauna

There is an increasing awareness of how damaging pollutants in the marine environment can be, however information on the effects of metal engineered nanoparticles (ENPs) on marine biota is still insufficient, despite an exponential rising in related publications in recent years. In order to provide an integrated insight on the present state of the art on metal ENP-related ecotoxicology studies on marine fauna, this review aimed to: (i) highlight the means of toxicity of metal ENPs in the marine environment, (ii) identify the principal biotic and abiotic factors that may alter metal ENP toxicity, and (iii) analyse and categorize results of these studies, including accumulation, molecular and histological biomarkers, genotoxicity and behavioural changes. Data retrieved from Scopus yielded 134 studies that met pre-established criteria. Most often, the target ENPs were titanium, zinc, copper or silver, and most studies (61.2%) focused on the phylum Mollusca. The degree of toxicity of metal ENPs was often dependent on the concentrations tested, length of exposure and the type of tissue sampled. Effects from simple tissue accumulation to DNA damage or behavioural alterations were identified, even when concentrations below environmentally available levels were used. It is proposed that other phyla besides the traditional Mollusca (and within it Bivalvia) should be used more often in this kind of studies, that exact pathways of toxicity be further explored, and lastly that co-stressors be used in order to best mimic conditions observed in nature. In this review, the current knowledge on engineered metal nanoparticles and their effects on marine fauna was summarized, highlighting present knowledge gaps. Guidelines for future studies focusing on under-developed subjects in ENP toxicology are also briefly provided.

Progress in the Research of the Toxicity Effect Mechanisms of Heavy Metals on Freshwater Organisms and Their Water Quality Criteria in China

Water quality criteria are the scientific basis for formulating water quality standards and environmental management practices. Due to the development of urbanization and industrialization, the problem of heavy metal pollution has become a serious environmental problem. Heavy metals not only have major impacts on aquatic organisms, but also seriously threaten human health. However, the current environmental criteria refer to the maximum value limitations of environmental factors in environmental media where harmful or detrimental effects are not produced on specific protected objects. This study reviewed the sources, hazard levels, toxic effect mechanisms, and the current research status of China’s water quality criteria for heavy metal pollutants. In addition, the focus and direction of future research on the toxic effects of heavy metal on aquatic organisms and the necessary criteria changes were discussed. The present study would provide an important theoretical basis for the future research of water quality criteria and risk assessment of heavy metal pollutants.

Effect of Chlamydomonas reinhardtii on the fate of CuO nanoparticles in aquatic environment

In this study, the effect of Chlamydomonas reinhardtii on the fate of CuO nanoparticles (CuO-NPs) in aquatic environment were investigated in terms of the colloidal stability, the free Cu²⁺ releasing, extracellular adsorption Cu (Cu_ex) and intracellular assimilation Cu (Cu_in). The results showed that, with the increasing microalgal density, the absolute value of zeta potential of CuO-NPs decreased and the mean hydrodynamic diameter (MHD) became larger, leading to a better aggregation and settling behavior of CuO-NPs. The microalgae also promoted the free Cu²⁺ releasing, however, inhibited adsorption and assimilation of metal nanoparticles (MNPs) into microalgal cells, resulting in the reduction of the Cu_ex and Cu_in per microalgal cell. The phenomenon was probably due to the reduced chance of contact between microalgae and MNPs. The internalization of CuO-NPs was also observed in microalgal cells by high resolution transmission electron microscope (HRTEM). Furthermore, the results of fast fourier transform (FFT)/inversed FFT (IFFT) analysis indicated that the CuO-NPs was reduced to Cu₂O-NPs in the microalgae cells. The above results suggested that the microalgae can significantly affect the fate of MNPs, and subsequently, influencing the bioavailability and toxicity of MNPs in the aquatic environment.

Biodynamics of Silver Nanoparticles in an Estuarine Oyster Revealed by 110mAgNP Tracing

The prevalence of silver nanoparticles (AgNPs) requires a comprehensive understanding of their biological impacts especially in marine and estuarine environments. Nevertheless, the background Ag concentration in organisms may impede the accuracy of Ag detection if the net accumulated Ag is low over a short exposure period. Here, a radio-synthesizing method was employed to trace the behavior of AgNPs with two sizes (15 and 60 nm) and two coatings (humic acid and citrate) in an estuarine oyster Crassostrea hongkongensis. This method was sensitive to detect the bioaccumulation and depuration of AgNPs in the oysters over a short period of exposure, which was necessary given the significant changes of particle aggregation in saline water environments. Through radioactive AgNP tracing and biokinetic modeling, we for the first time demonstrated the differential uptake mechanisms of different-sized AgNPs in oysters. Specifically, the ingestion of particles dominated the uptake of 60 nm AgNPs, whereas dermal uptake and ingestion contributed equally to 15 nm AgNPs. Surface coating (humic acid vs citrate) did not significantly affect the uptake of AgNPs by the oysters. The depuration of AgNPs from the oysters was relatively faster than that for the Ag ion. The digestive gland was the key detoxification organ of AgNPs with the greatest loss of Ag by the end of depuration. The findings of this study provide fundamental knowledge for nano-specific risk assessment in marine and estuarine environments.

Photocatalytic degradation of azo dye using core@shell nano-TiO2 particles to reduce toxicity

Clean and safe water is fundamental for human and environmental health. Traditional remediation of textile dye-polluted water with chemical, physical, and biological processes has many disadvantages. Due to this, nano-engineered materials are drawing more attention to this area. However, the widespread use of nano-particles for this purpose may lead to photocatalytic degradation of xenobiotics, while increasing the risk of nano-particle-induced ecotoxicity. Therefore, we comparatively evaluated the toxicity of novel synthesized core@shell TiO₂ and SiO₂ nano-particles to embryonic stages of Danio rerio and Xenopus laevis. The ability of photocatalytic destruction of the synthesized nano-particles was tested using toxic azo dye, disperse red 65, and the effects of reducing the toxicity were evaluated. The reflux process was used to synthesize catalysts in the study. The samples were characterized by scanning electron microscopy, X-ray fluorescence spectroscopy, X-ray diffractometry, BET surface area, and UV-vis-diffuse reflectance spectra. It was determined that the synthesized nano-particles had no significant toxic effect on D. rerio and X. laevis embryos. On the other hand, photocatalytic degradation of the dye significantly reduced lethal effects on embryonic stages of the organisms. Therefore, we suggest that specific nano-particles may be useful for water remediation to prevent human health and environmental impact. However, further risk assessment should be conducted for the ecotoxicological risks of nano-particles spilled in aquatic environments and the relationship of photocatalytic interaction with nano-particles and xenobiotics.

Immunotoxicity of Silver Nanoparticles (AgNPs) on the Leukocytes of Common Bottlenose Dolphins (Tursiops truncatus)

Silver nanoparticles (AgNPs) have been extensively used and are considered as an emerging contaminant in the ocean. The environmental contamination of AgNPs is expected to increase greatly over time, and cetaceans, as the top ocean predators, will suffer the negative impacts of AgNPs. In the present study, we investigate the immunotoxicity of AgNPs on the leukocytes of cetaceans using several methods, including cytomorphology, cytotoxicity, and functional activity assays. The results reveal that 20 nm Citrate-AgNPs (C-AgNP₂₀) induce different cytomorphological alterations and intracellular distributions in cetacean polymorphonuclear cells (cPMNs) and peripheral blood mononuclear cells (cPBMCs). At high concentrations of C-AgNP₂₀ (10 and 50 μg/ml), the time- and dose-dependent cytotoxicity in cPMNs and cPBMCs involving apoptosis is demonstrated. C-AgNP₂₀ at sub-lethal doses (0.1 and 1 μg/ml) negatively affect the functional activities of cPMNs (phagocytosis and respiratory burst) and cPBMCs (proliferative activity). The current study presents the first evidence of the cytotoxicity and immunotoxicity of AgNPs on the leukocytes of cetaceans and improves our understanding of environmental safety concerning AgNPs. The dose-response data of AgNPs on the leukocytes of cetaceans are invaluable for evaluating the adverse health effects in cetaceans and for proposing a conservation plan for marine mammals.

Partitioning of nanoparticle-originated dissolved silver in natural and artificial sediments

Sediments are believed to be a major sink for silver nanoparticles (AgNPs) in the aquatic environment, but there is a lack of knowledge about the environmental effects and behavior of AgNPs in sediments. The release of highly toxic Ag⁺ through dissolution of AgNPs is one mechanism leading to toxic effects in sediments. We applied an ultrasound-assisted sequential extraction method to evaluate the dissolution of AgNPs and to study the partitioning of dissolved Ag in sediments. Silver was spiked into artificial and 2 natural sediments (Lake Höytiäinen sediment and Lake Kuorinka sediment) as silver nitrate (AgNO₃ ), uncoated AgNPs, or polyvinylpyrrolidone-coated AgNPs (PVP-AgNPs). In addition, the total body burdens of Ag in the sediment-dwelling oligochaete Lumbriculus variegatus were assessed over a 28-d exposure period. The dissolution rate was found to be similar between the uncoated AgNP and PVP-AgNP groups. In all sediments, dissolved Ag was mainly bound to the residual fraction of the sediment, followed by iron and manganese oxides or natural organic matter. In Lake Kuorinka sediment, dissolved Ag that originated from PVP-AgNPs was relatively more bioaccessible, also resulting in higher total body burden in L. variegatus than that from uncoated AgNPs or AgNO₃ . In artificial sediment and Lake Höytiäinen sediment, AgNO₃ was significantly more bioaccessible than AgNPs. Our results highlight the importance of sediment properties and AgNP surface chemistry when evaluating the environmental exposure of AgNPs. Environ Toxicol Chem 2017;36:2593-2601. © 2017 SETAC.

Effect of exposure time, particle size and uptake pathways in immune cell lysosomal cytotoxicity of mussels exposed to silver nanoparticles

Cytotoxicity evaluation of hemocytes (lysosomal membrane stability [LMS] assay) from Mytilus galloprovincialis Lamarck, exposed to a sublethal dose (100 μg/L) of two size of silver nanoparticles (AgNPs: <50 nm and <100 nm) - prior to and after inhibition of potential uptake pathways (i.e., clathrin- and caveolae-mediated endocytosis) within different times of exposure (3, 6, 12 h) - showed that there was a significant cytotoxic effect on immune cells of mussels exposed for different times to either AgNP size (p < 0.01); the greater effect was with the smaller size. However, hemocytes seemed more sensitive to the larger AgNP after clathrin-mediated endocytosis was blocked (p < 0.01); this was not so with inhibition of caveolae-mediated endocytosis. Dimethyl-sulfoxide (DMSO) did not impart a carrier-mediated effect despite an enhanced cytotoxicity when DMSO was present with AgNP. From these results, it is concluded that the immunotoxicity of AgNP in mussels was size-dependent as well as length of exposure-dependent. It was also clear that nanoparticles (NP) internalization mechanisms were a major factor underlying any toxicity.

Aggregation, Sedimentation, Dissolution, and Bioavailability of Quantum Dots in Estuarine Systems

To understand their fate and transport in estuarine systems, the aggregation, sedimentation, and dissolution of CdSe quantum dots (QDs) in seawater were investigated. Hydrodynamic size increased from 40 to 60 nm to >1 mm within 1 h in seawater, and the aggregates were highly polydispersed. Their sedimentation rates in seawater were measured to be 4-10 mm/day. Humic acid (HA), further increased their size and polydispersity, and slowed sedimentation. Light increased their dissolution and release of dissolved Cd. The ZnS shell also slowed release of Cd ions. With sufficient light, HA increased the dissolution of QDs, while with low light, HA alone did not change their dissolution. The benthic zone in estuarine systems is the most probable long-term destination of QDs due to aggregation and sedimentation. The bioavailability of was evaluated using the mysid Americamysis bahia. The 7-day LC50s of particulate and dissolved QDs were 290 and 23 μg (total Cd)/L, respectively. For mysids, the acute toxicity appears to be from Cd ions; however, research on the effects of QDs should be conducted with other organisms where QDs may be lodged in critical tissues such as gills or filtering apparatus and Cd ions may be released and delivered directly to those tissues.

Exposure of juvenile turbot (Scophthalmus maximus) to silver nanoparticles and 17α-ethinylestradiol mixtures: Implications for contaminant uptake and plasma steroid hormone levels

Combined exposure to engineered nanoparticles (ENPs) and anthropogenic contaminants can lead to changes in bioavailability, uptake and thus effects of both groups of contaminants. In this study we investigated effects of single and combined exposures of silver (Ag) nanoparticles (AgNPs) and the synthetic hormone 17α-ethinylestradiol (EE2) on tissue uptake of both contaminants in juvenile turbot (Scophthalmus maximus). Silver uptake and tissue distribution (gills, liver, kidney, stomach, muscle and bile) were analyzed following a 14-day, 2-h daily pulsed exposure to AgNPs (2 μg L^-1 and 200 μg L^-1), Ag⁺ (50 μg L^-1), EE2 (50 ng L^-1) and AgNP + EE2 (2 or 200 μg L^-1+50 ng L^-1). Effects of the exposures on plasma vitellogenin (Vtg) levels, EE2 and steroid hormone concentrations were investigated. The AgNP and AgNP + EE2 exposures resulted in similar Ag concentrations in the tissues, indicating that combined exposure did not influence Ag uptake in tissues. The highest Ag concentrations were found in gills. For the Ag⁺ exposed fish, the highest Ag concentrations were measured in the liver. Our results show dissolution processes of AgNPs in seawater, indicating that the tissue concentrations of Ag may partly originate from ionic release. Plasma EE2 concentrations and Vtg induction were similar in fish exposed to the single contaminants and the mixed contaminants, indicating that the presence of AgNPs did not significantly alter EE2 uptake. Similarly, concentrations of most steroid hormones were not significantly altered due to exposures to the combined contaminants versus the single compound exposures. However, high concentrations of AgNPs in combination with EE2 caused a drop of estrone (E1) (female fish) and androstenedione (AN) (male and female fish) levels in plasma below quantification limits. Our results indicate that the interactive effects between AgNPs and EE2 are limited, with only high concentrations of AgNPs triggering synergistic effects on plasma steroid hormone concentrations in juvenile turbots.

Influence of Silver nanoparticles on nutrient removal and microbial communities in SBR process after long-term exposure

The widespread utilization of silver nanoparticles (AgNPs) in industrial and commercial products inevitably raises the release into wastewater that might cause potential negative impacts on sewage treatment system. In this paper, long-term exposure experiments at four levels were conducted to determine whether AgNPs caused adverse impacts on nutrient removals in sequencing batch reactors (SBRs) and changes of microbial community structure. Compared with the control reactor (without AgNPs), carbon, nitrogen and phosphorus removal in presence of 0.1mg/L AgNPs was no difference. However, presence of 1.0 and 10mg/L AgNPs decreased the average removal efficiencies of COD from 95.4% to 85.2% and 68.3%, ammonia nitrogen from 98.8% to 71.2% and 49%, SOP from 97.6% to 75.5% and 54.1%, respectively. It was found that AgNPs could accumulate in sludge with the distribution coefficients of 39.2-114L/g, inhibit the protein and polysaccharide production in EPS, reduce the SOUR of sludge, and greatly increase LDH release from microbial cells. The illumina high-throughput sequencing results indicated that AgNPs concentration changed the structures of bacterial communities, associating with the effects of AgNPs on reactor performance. Sequence analyses showed that Proteobacteria, Bacteroidetes and Acidobacteria were the dominant phyla. It was notable that AgNPs addition reduced the contents of several nitrifying bacteria at genera level in sludge, leading to the lower removal of nitrogen.

Toxicity Testing of Silver Nanoparticles in Artificial and Natural Sediments Using the Benthic Organism Lumbriculus variegatus

The increased use of silver nanoparticles (AgNP) in industrial and consumer products worldwide has resulted in their release to aquatic environments. Previous studies have mainly focused on the effects of AgNP on pelagic species, whereas few studies have assessed the risks to benthic invertebrates despite the fact that the sediments act as a large potential sink for NPs. In this study, the toxicity of sediment-associated AgNP was evaluated using the standard sediment toxicity test for chemicals provided by the Organization of Economic Cooperation and Development. The freshwater benthic oligochaete worm Lumbriculus variegatus was exposed to sediment-associated AgNP in artificial and natural sediments at concentrations ranging from 91 to 1098 mg Ag/kg sediment dry weight. Silver nitrate (AgNO3) was used as a reference compound for Ag toxicity. The measured end points of toxicity were mortality, reproduction, and total biomass. In addition, the impact of sediment-associated AgNP on the feeding rate of L. variegatus was studied in a similar test set-up as mentioned previously. The addition of AgNP into the sediment significantly affected the feeding rate and reproduction of the test species only at the highest concentration (1098 mg/kg) of Ag in the natural sediment with the lowest pH. In comparison, the addition of AgNO3 resulted in reproductive toxicity in every tested sediment, and Ag was more toxic when spiked as AgNO3 than AgNP. In general, sediments were observed to have a high capacity to eliminate the AgNP-derived toxicity. However, the capacity of sediments to eliminate the toxicity of Ag follows a different pattern when spiked as AgNP than AgNO3. The results of this study emphasize the importance of sediment-toxicity testing and the role of sediment properties when evaluating the environmental effects and behavior of AgNP in sediments.

Effects of nanomaterials on marine invertebrates

The development of nanotechnology will inevitably lead to the release of consistent amounts of nanomaterials (NMs) and nanoparticles (NPs) into marine ecosystems. Ecotoxicological studies have been carried out to identify potential biological targets of NPs, and suitable models for predicting their impact on the health of the marine environment. Recent studies in invertebrates mainly focused on NP accumulation and sub-lethal effects, rather than acute toxicity. Among marine invertebrates, bivalves represent by large the most studied group, with polychaetes and echinoderms also emerging as significant targets of NPs. However, major scientific gaps still need to be filled. In this work, factors affecting the fate of NPs in the marine environment, and their consequent uptake/accumulation/toxicity in marine invertebrates will be summarized. The results show that in different model species, NP accumulation mainly occurs in digestive tract and gills. Data on sub-lethal effects and modes of action of different types of NPs (mainly metal oxides and metal based NPs) in marine invertebrates will be reviewed, in particular on immune function, oxidative stress and embryo development. Moreover, the possibility that such effects may be influenced by NP interactions with biomolecules in both external and internal environment will be introduced. In natural environmental media, NP interactions with polysaccharides, proteins and colloids may affect their agglomeration/aggregation and consequent bioavailability. Moreover, once within the organism, NPs are known to interact with plasma proteins, forming a protein corona that can affect particle uptake and toxicity in target cells in a physiological environment. These interactions, leading to the formation of eco-bio-coronas, may be crucial in determining particle behavior and effects also in marine biota. In order to classify NPs into groups and predict the implications of their release into the marine environment, information on their intrinsic properties is clearly insufficient, and a deeper understanding of NP eco/bio-interactions is required.

Saltwater ecotoxicology of Ag, Au, CuO, TiO2, ZnO and C60 engineered nanoparticles: An overview

This review paper examined 529 papers reporting experimental nanoecotoxicological original data. Only 126 papers referred to saltwater environments (water column and sediment) including a huge variety of species (n=51), their relative endpoints and engineered nanoparticles (ENPs) (n=38). We tried to provide a synthetic overview of the ecotoxicological effects of ENPs from existing data, refining papers on the basis of cross-cutting selection criteria and supporting a "mind the gap" approach stressing on missing data for hazard and risk assessment. After a codified selection procedure, attention was paid to Ag, Au, CuO, TiO2, ZnO and C60 ENPs, evidencing and comparing the observed nanoecotoxicity range of effect. Several criticisms were evidenced: i) some model organisms are overexploited like microalgae and molluscs compared to annelids, echinoderms and fish; ii) underexploited model organisms: mainly bacteria and fish; iii) exposure scenario variability: high species-specific and ENP scenarios including organism life stage and way of administration/spiking of toxicants; iv) scarce comparability between results due to exposure scenario variability; v) micro- and mesocosms substantially unexplored; vi) mixture effects: few examples are available only for ENPs and traditional pollutants; mixtures of ENPs have not been investigated yet; vii) effects of ions and ENPs: nAg, nCuO and nZnO toxicity aetiology is still a matter of discussion; viii) size and morphology effects of ENPs: scarcely investigated, justified and understood. Toxicity results evidenced that: nAu>nZnO>nAg>nCuO>nTiO2>C60.

De novo transcriptome sequencing of a non-model polychaete species

Transcriptome sequencing is a useful method for studying gene-sequences data, especially in non-model organisms whose genomic sequences are yet to be determined. Indeed, even without any genome reference, transcripts can be assembled de novo to produce a genome-scale transcription map. Here we describe a de novo transcriptome assembly for the polychaete worm Ophryotrocha diadema, generated from 454-sequencing (Roche GS-FLX Titanium Sequencing). We describe the sequencing, the assembly and functional annotation of EST sequences, and the level of transcriptome coverage provided by our sequence data. The sequences we assembled represent a wide depiction of expressed genes from throughout the lifespan of O. diadema. We found gene sequences to be part of a broad range of functions (i.e. biological and metabolic processes, immune system, reproductive processes, development and growth, signalling and response to stimuli) and we therefore built the first transcriptomic reference for Ophryotrocha polychaete worms. These results encourage us to focus our investigation on many aspects of O. diadema and to extend our research to co-generic species.

Effect of sulfidation and dissolved organic matters on toxicity of silver nanoparticles in sediment dwelling organism, Chironomus riparius

The properties, fate, and toxicity of silver nanoparticles (AgNPs) are readily modified in the environment. Thus, in order to predict the environmental impact of AgNPs, the toxicity test should be conducted to assess the interactions of AgNPs with environmental matrices. Dissolved organic matter (DOM) is known to mitigate AgNPs toxicity in natural systems, and it is also known that silver binds strongly to sulfur. Little is known, however, about the effect of sulfidation and to what extent it could compete with DOM in the sediment. We therefore investigated the effect of sulfide on a sediment dwelling organism, Chironomus riparius using ecotoxicity endpoints. We then investigated how sulfide and a combination of sulfide and DOM affect the toxicity of AgNPs in C. riparius. We also monitored the concentrations of silver in the water and sediment compartments, as well as in C. riparius tissue, in the presence and absence of sulfide. Finally, in order to investigate how sulfide and DOM affect the release of ions from AgNPs, we also monitored released Ag(+) in each treatment. In the presence of sulfide, AgNPs were found to be less toxic to C. riparius in acute and chronic endpoints than AgNPs alone, whereas DOM treatment did not modulate the toxicity of AgNPs. Sulfide treatment reduced the release of Ag(+) from AgNPs. Water-spiked AgNPs with sulfide were found to be more slowly incorporated into both sediment and larvae as compared to the AgNP alone. Overall, the results suggest that the presence of sulfide in sediment mitigates the ecotoxicity of AgNPs in C. riparius.

Physiological effects and cellular responses of metamorphic larvae and juveniles of sea urchin exposed to ionic and nanoparticulate silver

The widespread use of silver nanoparticles (AgNPs) would likely result in their discharge into wastewater and inevitable release in densely populated coastal areas. It is known that AgNPs can cause harmful effects to marine fauna, but how they affect development stages is still an open question. In order to understand in details how polymer-coated AgNPs (PAAm-AgNPs) (from 0.19 to 4.64mM as Ag) can affect critical stages of marine invertebrate development, metamorphic larvae and juveniles of sea urchins were used as biological models. Multidimensional scaling (MDS) approach based on Bray-Curtis similarity matrix with PERMANOVA showed organisms in a multivariate space undergoing through different physiological conditions as a function of time, chemical forms of silver, nominal concentrations, and presence or absence of food. Sublethal effects such as lethargy, oedema and immobility mainly characterized PAAm-AgNPs effects with juveniles and postlarvae, whereas necrosis and death arose in Ag(+) conditions in short-term tests. Chronically exposed metamorphic larvae had their morphogenic processes interrupted by PAAm-AgNPs and a high mortality rate was observed in recovery period. On the contrary, Ag(+) ions caused progressive mortality during exposure, but a quick recovery in uncontaminated seawater was observed. By means of fluorescent markers we showed that nanosilver could be transferred between consecutive stages (swimming larvae and postlarvae) and highlighted how important is food to enhance PAAm-AgNPs uptake. Using TEM we observed that unfed juveniles had nanosilver aggregates mostly restricted to their coelomic sinuses, while metamorphic larvae already had nano-contamination overspread in different tissues and blastocoel. Our main hypothesis for nanotoxicity of PAAM-AgNPs relies on the slow dissolution of nano-core over time, but in this study the effects of particulate silver form itself are also evoked. Main mechanisms governing tissular and cellular responses to nano-intoxication such as inflammatory response and detoxification based on the role of sentinel cells (peritoneal cells and coelomocytes) for general homeostasis are discussed. This paper is first to detail physiological states, main uptake routes and cellular response against polymer-coated AgNPs in developmental stages of marine invertebrate species.

Genetic correlations and little genetic variance for reaction norms may limit potential for adaptation to pollution by ionic and nanoparticulate silver in a whitefish (Salmonidae)

For natural populations to adapt to anthropogenic threats, heritable variation must persist in tolerance traits. Silver nanoparticles, the most widely used engineered nanoparticles, are expected to increase in concentrations in freshwaters. Little is known about how these particles affect wild populations, and whether genetic variation persists in tolerance to permit rapid evolutionary responses. We sampled wild adult whitefish and crossed them in vitro full factorially. In total, 2896 singly raised embryos of 48 families were exposed to two concentrations (0.5 μg/L; 100 μg/L) of differently sized silver nanoparticles or ions (silver nitrate). These doses were not lethal; yet higher concentrations prompted embryos to hatch earlier and at a smaller size. The induced hatching did not vary with nanoparticle size and was stronger in the silver nitrate group. Additive genetic variation for hatching time was significant across all treatments, with no apparent environmental dependencies. No genetic variation was found for hatching plasticity. We found some treatment‐dependent heritable variation for larval length and yolk volume, and one instance of additive genetic variation for the reaction norm on length at hatching. Our assessment suggests that the effects of silver exposure on additive genetic variation vary according to trait and silver source. While the long‐term fitness consequences of low‐level silver exposure on whitefish embryos must be further investigated to determine whether it is, in fact, detrimental, our results suggest that the evolutionary potential for adaptation to these types of pollutants may be low.

Toxicity of silver and gold nanoparticles on marine microalgae

The increased use of nanomaterials in several novel industrial applications during the last decade has led to a rise in concerns about the potential toxic effects of released engineered nanoparticles (NPs) into the environment, as their potential toxicity to aquatic organisms is just beginning to be recognised. Toxicity of metallic nanoparticles to aquatic organisms, including microalgae, seems to be related to their physical and chemical properties, as well as their behaviour in the aquatic media where processes of dissolution, aggregation and agglomeration can occur. Although the production of these particles has increased considerably in recent years, data on their toxicity on microalgae, especially those belonging to marine or estuarine environments remain scarce and scattered. The literature shows a wide variation of results on toxicity, mainly due to the different methodology used in bioassays involving microalgae. These can range for up to EC50 data, in the case of AgNPs, representing five orders of magnitude. The importance of initial cellular density is also addressed in the text, as well as the need for keeping test conditions as close as possible to environmental conditions, in order to increase their environmental relevance. This review focuses on the fate and toxicity of silver, gold, and gold-silver alloy nanoparticles on microalgae, as key organisms in aquatic ecosystems. It is prompted by their increased production and use, and taking into account that oceans and estuaries are the final sink for those NPs. The design of bioassays and further research in the field of microalgae nanoecotoxicology is discussed, with a brief survey on newly developed technology of green (algae mediated) production of Ag, Au and Ag-Au bimetallic NPs, as well as some final considerations about future research on this field.

Toxicity mechanisms of ionic silver and polymer-coated silver nanoparticles with interactions of functionalized carbon nanotubes on early development stages of sea urchin

Exposures of aquatic organisms to multiple contaminants are likely to take place in estuarine and coastal areas and combined effects on early life stages have to be examined. Among emerging contaminants, ionic silver (Ag(+)) and silver nanoparticles (AgNps) have demonstrated contrasting effects on marine invertebrates, but their interactions with functionalized carbon nanotubes (f-SWCNTs) have not yet been investigated in details. In order to observe the impacts and understand the toxicity mechanism of Ag(+) and polymer-coated AgNps, and their combined effects with f-SWCNTs, successive development stages of embryos of sea urchin, Strongylocentrotus droebachiensis, were exposed to Ag(+), AgNps and f-SWCNTs, separately and in mixtures using moderate environmental concentrations. We also assessed long-term effects of treatments under recovery conditions. Morphological endpoints such as archenteron elongation, primary and secondary mesenchyme cells fate, pigment cells migration, spiculogenic cells and gut development indicated different effects of silver and nanosilver forms during successive development stages. Whereas Ag(+) induced vegetalization and extrusion of mesenchyme cells on early embryos; f-SWCNTs+Ag(+) strongly interfered with gut regionalization in late larvae. Sensitive blastocoelar cells got vacuolized and shapeless with AgNps, but not with mixtures with f-SWCNTs. Increased concentrations of Ag(+) and f-SWCNTs+Ag(+) led to the most disruptive effects during development, but f-SWCNTs+Ag(+) caused the highest mortality rate during the recovery period, which indicated far-reaching effects driven by f-SWCNTs and their ability to keep silver more available during exposure period.

Chronic Effects of Coated Silver Nanoparticles on Marine Invertebrate Larvae: A Proof of Concept Study

Silver nanoparticles (AgNPs), owing to their unique physical and chemical properties, have become increasingly popular in consumer products. However, data on their potential biological effects on marine organisms, especially invertebrates, remain very limited. This proof of principle study reports the chronic sub-lethal toxicity of two coated AgNPs (oleic acid coated AgNPs and polyvinylpyrrolidone coated AgNPs) on marine benthic invertebrate larvae across three phyla (i.e., the barnacle Balanus Amphitrite, the slipper-limpet Crepidula onyx, and the polychaete Hydroides elegans) in terms of growth, development, and metamorphosis. Bioaccumulation and biodistribution of silver were also investigated. Larvae were also exposed to silver nitrate (AgNO₃) in parallel to distinguish the toxic effects derived from nano-silver and the aqueous form of silver. The sub-lethal effect of chronic exposure to coated AgNPs resulted in a significant retardation in growth and development, and reduction of larval settlement rate. The larval settlement rate of H. elegans was significantly lower in the coated AgNP treatment than the AgNO₃ treatment, suggesting that the toxicity of coated AgNPs might not be solely evoked by the release of silver ions (Ag⁺) in the test medium. The three species accumulated silver effectively from coated AgNPs as well as AgNO₃, and coated AgNPs were observed in the vacuoles of epithelial cell in the digestive tract of C. onyx. Types of surface coatings did not affect the sub-lethal toxicity of AgNPs. This study demonstrated that coated AgNPs exerted toxic effects in a species-specific manner, and their exposure might allow bioaccumulation of silver, and affect growth, development, and settlement of marine invertebrate larvae. This study also highlighted the possibility that coated AgNPs could be taken up through diet and the toxicity of coated AgNPs might be mediated through toxic Ag⁺ as well as the novel modalities of coated AgNPs.

Impact of nanoparticles on human and environment: review of toxicity factors, exposures, control strategies, and future prospects

Nanotechnology has revolutionized the world through introduction of a unique class of materials and consumer products in many arenas. It has led to production of innovative materials and devices. Despite of their unique advantages and applications in domestic and industrial sectors, use of materials with dimensions in nanometers has raised the issue of safety for workers, consumers, and human environment. Because of their small size and other unique characteristics, nanoparticles have ability to harm human and wildlife by interacting through various mechanisms. We have reviewed the characteristics of nanoparticles which form the basis of their toxicity. This paper also reviews possible routes of exposure of nanoparticles to human body. Dermal contact, inhalation, and ingestion have been discussed in detail. As very limited data is available for long-term human exposures, there is a pressing need to develop the methods which can determine short and long-term effects of nanoparticles on human and environment. We also discuss in brief the strategies which can help to control human exposures to toxic nanoparticles. We have outlined the current status of toxicological studies dealing with nanoparticles, accomplishments, weaknesses, and future challenges.