Stabilization of engineered zero-valent nanoiron with Na-acrylic copolymer enhances spermiotoxicity

Investigating the toxic mechanism of iron oxide nanoparticles-induced oxidative stress in tadpole (Duttaphrynus melanostictus): A combined biochemical and molecular study

Metal oxide nanomaterials have toxicity towards aquatic organisms, especially microbes and invertebrates, but little is known about their impact on amphibians. We conducted a study on Duttaphrynus melanostictus (D. melanostictus) tadpoles to explore the chronic toxicity effects of iron oxide nanoparticles (IONPs) and the underlying mechanisms of IONPs-induced oxidative stress. IONPs exposure led to increased iron accumulation in the blood, liver, and kidneys of tadpoles, significantly affecting blood parameters and morphology. Higher IONPs concentrations (10 and 50 mg L-1) triggered reactive oxygen species generation, resulting in lipid peroxidation, oxidative stress, and pronounced toxicity in tadpoles. The activity levels of antioxidant enzymes/proteins (SOD, CAT, albumin, and lysozyme) decreased after IONPs exposure, and immunological measures in the blood serum were significantly reduced compared to the control group. Molecular docking analysis revealed that IONPs primarily attached to the surface of SOD/CAT/albumin/lysozyme through hydrogen bonding and hydrophobic forces. Overall, this study emphasizes the ability of IONPs to induce oxidative damage by decreasing immunological profiles such as ACH50 (34.58 ± 2.74 U mL-1), lysozyme (6.94 ± 0.82 U mL-1), total Ig (5.00 ± 0.35 g dL-1), total protein (1.20 ± 0.17 g dL-1), albumin (0.52 ± 0.01 g dL-1) and globulin (0.96 ± 0.01 g dL-1) and sheds light on their potential toxic effects on tadpoles.

Toxicity of zero-valent iron nanoparticles to soil organisms and the associated defense mechanisms: a review

Nanoscale zero-valent iron particles (NZVI) are widely used in a variety of industries owing to their advantageous mechanical, physical, and chemical properties. These particles can be released into environmental media, including water, soil, and air, through several pathways. NZVI in the ecosystem can be taken up, excreted and distributed within organisms, which is harmful to plants, animals and humans. Plants play a significant role as producers in the ecological circle and can both positively and negatively affect the ecological behavior of NZVI. Therefore, understanding the relationship between plants and NZVI is likely to be of great value for the assessment of NZVI-associated risks and future research directions. In this review, we summarize the current knowledge on the uptake, distribution, and accumulation of NZVI in plants; the phytotoxicity triggered by NZVI exposure at the physiological, biochemical, and molecular levels; and the defense mechanism used by plants to defend against NZVI-induced insults. We further discuss the toxic effects of NZVI on soil animals and microorganisms as well as the risk posed by the presence of NZVI in the food chain.

Exploratory study of removing nutrients from aqueous environments employing a green synthesised nano zero-valent iron

This study explores the green synthesis of nano zero-valent iron (nZVI) extracted from the peel of selected waste fruits: banana (BP), mango (MP), and pomegranate (GP), for the removal of nutrients from aqueous environments. The extract was prepared by heating de-ionised water at 60°C for 5 min, adding a reducing and a stabilising agent, FeCl₃, then stirring with a N₂ gas flush solution to form iron nanoparticles, with a final drying step under N₂ conditions. Using a variety of characterisation techniques, it was determined that nZVI particles were successfully synthesised via the reduction of iron (III) to iron (0) and stabilised by the presence of phenolic compounds in the extract. The removal of 20 mg/L nutrients from an aqueous solution carried out using the nZVIs resulted in nitrate removal of 92% (nZVI-GP), 88% (nZVI-BP), and 72% (nZVI-MP) within 5 min, whereas ∼98% phosphate was removed by all three nZVIs within 60 min. The aging effect was also tested. Aging the nZVIs for >20 days resulted in less efficient phosphate adsorption after exposure for 250 min; ∼70% phosphate removal was achieved using the nZVIs under these conditions. The mechanisms and pathways of nitrate reduction, including the adsorption of phosphate by nZVI were demonstrated, and discussed. Leachability tests of the phosphate-loaded nZVIs revealed that 10%, 28%, and 48% phosphate was released from the nZVI-GP, nZVI-BP, and nZVI-MP particles, respectively. Using waste fruit is, therefore, a viable and sustainable alternative to the traditional sodium borohydride method to produce nZVIs for environmental application.

Nanopolystyrene beads affect motility and reproductive success of oyster spermatozoa (Crassostrea gigas)

Oysters are keystone species that use external fertilization as a sexual mode. The gametes are planktonic and face a wide range of stressors, including plastic litter. Nanoplastics are of increasing concern because their size allows pronounced interactions with biological membranes, making them a potential hazard to marine life. In the present study, oyster spermatozoa were exposed for 1 h to various doses (from 0.1 to 25 µg mL^-1) of 50-nm polystyrene beads with amine (50-NH₂ beads) or carboxyl (50-COOH beads) functions. Microscopy revealed adhesion of particles to the spermatozoa membranes, but no translocation of either particle type into cells. Nevertheless, the 50-NH₂ beads at 10 µg mL^-1 induced a high spermiotoxicity, characterized by a decrease in the percentage of motile spermatozoa (-79%) and in the velocity (-62%) compared to control spermatozoa, with an overall drop in embryogenesis success (-59%). This major reproduction failure could be linked to a homeostasis disruption in exposed spermatozoa. The 50-COOH beads hampered spermatozoa motility only when administered at 25 µg mL^-1 and caused a decrease in the percentage of motile spermatozoa (-66%) and in the velocity (-38%), but did not affect embryogenesis success. Microscopy analyses indicated these effects were probably due to physical blockages by microscale aggregates formed by the 50-COOH beads in seawater. This toxicological study emphasizes that oyster spermatozoa are a useful and sensitive model for (i) deciphering the fine interactions underpinning nanoplastic toxicity and (ii) evaluating adverse effects of plastic nanoparticles on marine biota while waiting for their concentration to be known in the environment.

Reactive Oxygen Species-Related Nanoparticle Toxicity in the Biomedical Field

The unique physicochemical characteristics of nanoparticles have recently gained increasing attention in a diverse set of applications, particularly in the biomedical field. However, concerns about the potential toxicological effects of nanoparticles remain, as they have a higher tendency to generate excessive amounts of reactive oxygen species (ROS). Due to the strong oxidation potential, the excess ROS induced by nanoparticles can result in the damage of biomolecules and organelle structures and lead to protein oxidative carbonylation, lipid peroxidation, DNA/RNA breakage, and membrane structure destruction, which further cause necrosis, apoptosis, or even mutagenesis. This review aims to give a summary of the mechanisms and responsible for ROS generation by nanoparticles at the cellular level and provide insights into the mechanics of ROS-mediated biotoxicity. We summarize the literature on nanoparticle toxicity and suggest strategies to optimize nanoparticles for biomedical applications.

Gamete quality in a multistressor environment

Over the past few decades, accumulated evidence confirms that the global environment conditions are changing rapidly. Urban industrialization, agriculture and globalization have generated water, air and soil pollution, giving rise to an environment with a growing number of stress factors, which has a serious impact on the fitness, reproduction and survival of living organisms. The issue raises considerable concern on biodiversity conservation, which is now at risk: it is estimated that a number of species will be extinct in the near future. Sexual reproduction is the process that allows the formation of a new individual and is underpinned by gamete quality defined as the ability of spermatozoa and oocytes to interact during fertilization leading to the creation and development of a normal embryo. This review aimed to provide the current state of knowledge regarding the impact of a broad spectrum of environmental stressors on diverse parameters used to estimate and evaluate gamete quality in humans and in canonical animal models used for experimental research. Effects of metals, biocides, herbicides, nanoparticles, plastics, temperature rise, ocean acidification, air pollution and lifestyle on the physiological parameters that underlie gamete fertilization competence are described supporting the concept that environmental stressors represent a serious hazard to gamete quality with reproductive disorders and living organism failure. Although clear evidence is still limited, gamete capacity to maintain and/or recover physiological conditions is recently demonstrated providing further clues about the plasticity of organisms and their tolerance to the pressures of pollution that may facilitate the reproduction and the persistence of species within the scenario of global change. Changes in the global environment must be urgently placed at the forefront of public attention, with a massive effort invested in further studies aimed towards implementing current knowledge and identifying new methodologies and markers to predict impairment of gamete quality.

Bibliometric study of the toxicology of nanoescale zero valent iron used in soil remediation

The application of nanoscale zero-valent iron is one of the most widely used remediation technologies; however, the potential environmental risks of this technology are largely unknown. In order to broaden the knowledge on this subject, the present work consists of a bibliometric study of all of publications related to the toxicity of zero-valent iron nanoparticles used in soil remediation available from the Scopus (Elsevier) and Web of Science (Thompson Reuters) databases. This study presents a temporal distribution of the publications, the most cited articles, the authors who have made the greatest contribution to the theme, and the institutions, countries, and scientific journals that have published the most on this subject. The use of bibliometrics has allowed for the visualization of a panorama of the publications, providing an appropriate analysis to guide new research towards an effective contribution to science by filling the existing gaps. In particular, the lack of studies in several countries reveals a promising area for the development of further research on this topic.

Nanoscale zerovalent iron particles induce differential cytotoxicity, genotoxicity, oxidative stress and hemolytic responses in human lymphocytes and erythrocytes in vitro

The growing usage of nanoscale zerovalent iron particles (nZVI) in the remediation of soil, ground/surface water has elicited large-scale environmental release triggering human exposure. The size of nanomaterials is a key regulator of toxicity. However, the effect of a variable size of nZVI on genotoxicity is unexplored in human cells. To the best of our knowledge, in this study, the cytotoxic, genotoxic and hemolytic potential of nZVI-1 (15 nm) and nZVI-2 (50 nm) at concentrations of 5, 10 and 20 μg/mL was evaluated for the first time in human lymphocytes and erythrocytes treated for 3 hours. In erythrocytes, spherocytosis and echinocytosis occurred upon exposure to nZVI-1 and nZVI-2, respectively, leading to hemolysis. Lymphocytes treated with 20 μg/mL nZVI-2 and 10 μg/mL nZVI-1, incurred maximum DNA damage, although nZVI-2 induced higher cyto-genotoxicity than nZVI-1. This can be attributed to higher Fe ion dissolution and time/concentration-dependent colloidal destabilization (lower zeta potential) of nZVI-2. Although nZVI-1 showed higher uptake, its lower genotoxicity can be due to lesser Fe content, Fe ion dissolution and superior colloidal stability (higher zeta potential) compared with nZVI-2. Substantial accumulation of Ca²⁺ , superoxide anions, hydroxyl radicals and H₂ O₂ leading to mitochondrial impairment and altered antioxidant enzyme activity was noted at the same concentrations. Pre-treatment with N-acetyl-cysteine modulated these parameters indicating the indirect action of reactive oxygen species in nZVI-induced DNA damage. The morphology of diffused nuclei implied the possible onset of apoptotic cell death. These results validate the synergistic role of size, ion dissolution, colloidal stability and reactive oxygen species on cyto-genotoxicity of nZVI and unlock further prospects in its environmental nano-safety evaluation.

Genetic, reproductive and oxidative damage in mice triggered by co-exposure of nanoparticles: From a hypothetical scenario to a real concern

Humans are potentially exposed to multiple nanoparticles kinds through nanotechnology-based consumer products. There is insufficient data on the in vivo toxicity of nanotechnology products, as well as no data on the possible toxicity, including genotoxicity and reproductive toxicity of co-exposure to different kind of nanoparticles. In this work, solid lipid nanoparticles (SLNs) and superparamagnetic iron oxide nanoparticles (SPIONs) were selected for evaluation of a hypothetical condition of in vivo co-exposure. Genotoxicity of SPIONs and SLNs was performed separately and in 1:1 mixture in mice. Bone marrow micronucleus assay, sperm morphology test, and sperm count were carried out. Also, the serum ALT and AST activities; and hematological parameters of the treated mice were analyzed. The results showed a significant increase (p < 0.05) in micronucleated polychromatic erythrocytes (MNPCE) and nuclear abnormalities (NA) in SPIONs, SLNs and their mixture treated mice. The mixture induced the highest frequency of MNPCE and NA. A similar result was observed in the sperm morphology test, with the mixture inducing the highest sperm abnormalities, followed by SLNs and the least by SPIONs. Significant alteration to RDW, MCHC, MCV, GRAN, and platelets, as well as increased activities of serum AST were observed in the mice treated with a mixture of the two kinds of nanoparticles. Calculation of interaction factor showed a possible synergistic effect between SPIONs and SLNs in MNPCE, NA and sperm morphology studied. Even as a hypothetical scenario of co-exposure to SLNs and SPIONs, this study showed, for the first time, that co-exposure to SPIONs and SLNs is more genotoxic to somatic and germ cells than their individual exposure.

Nanoplastics impaired oyster free living stages, gametes and embryos

In the marine environment, most bivalve species base their reproduction on external fertilization. Hence, gametes and young stages face many threats, including exposure to plastic wastes which represent more than 80% of the debris in the oceans. Recently, evidence has been produced on the presence of nanoplastics in oceans, thus motivating new studies of their impacts on marine life. Because no information is available about their environmental concentrations, we performed dose-response exposure experiments with polystyrene particles to assess the extent of micro/nanoplastic toxicity. Effects of polystyrene with different sizes and functionalizations (plain 2-μm, 500-nm and 50-nm; COOH-50 nm and NH₂-50 nm) were assessed on three key reproductive steps (fertilization, embryogenesis and metamorphosis) of Pacific oysters (Crassostrea gigas). Nanoplastics induced a significant decrease in fertilization success and in embryo-larval development with numerous malformations up to total developmental arrest. The NH₂-50 beads had the strongest toxicity to both gametes (EC₅₀ = 4.9 μg/mL) and embryos (EC₅₀ = 0.15 μg/mL), showing functionalization-dependent toxicity. No effects of plain microplastics were recorded. These results highlight that exposures to nanoplastics may have deleterious effects on planktonic stages of oysters, presumably interacting with biological membranes and causing cyto/genotoxicity with potentially drastic consequences for their reproductive success.

The Toxicity Assessment of Iron Oxide (Fe₃O₄) Nanoparticles on Physical and Biochemical Quality of Rainbow Trout Spermatozoon

The aim of this study was to evaluate the in vitro effect of different doses (50, 100, 200, 400, and 800 mg/L) of Fe₃O₄ nanoparticles (NPs) at 4 °C for 24 h on the kinematics of rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) spermatozoon. Firstly, Fe₃O₄ NPs were prepared at about 30 nm from Iron (III) chloride, Iron (II) chloride, and NH₃ via a co-precipitation synthesis technique. Then, the prepared Fe₃O₄ NPs were characterized by different instrumental techniques for their chemical structure, purity, morphology, surface properties, and thermal behavior. The size, microstructure, and morphology of the prepared Fe₃O₄ NPs were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) spectroscopy, and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS). The thermal properties of the Fe₃O₄ NPs were determined with thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimeter (DSC) analysis techniques. According to our results, there were statistically significant (p < 0.05) decreases in the velocities of spermatozoon after treatment with 400 mg/L Fe₃O₄ NPs. The superoxide dismutase (SOD) and catalase (CAT) activities were significant (p < 0.05) decrease after 100 mg/L in after exposure to Fe₃O₄ NPs in 24 h. As the doses of Fe₃O₄ NPs increases, the level of malondialdehyde (MDA) and total glutathione (tGSH) significantly (p < 0.05) increased at doses of 400 and 800 mg/L.

Effects of nanosilver on Mytilus galloprovincialis hemocytes and early embryo development

Silver nanoparticles (AgNP), one of the main nanomaterials for production and use, are expected to reach the aquatic environment, representing a potential threat to aquatic organisms. In this study, the effects of bare AgNPs (47 nm) on the marine mussel Mytilus galloprovincialis were evaluated at the cellular and whole organism level utilizing both immune cells (hemocytes) and developing embryos. The effects were compared with those of ionic Ag⁺(AgNO₃). In vitro short-term exposure (30 min) of hemocytes to AgNPs induced small lysosomal membrane destabilization (LMS EC₅₀ = 273.1 μg/mL) and did not affect other immune parameters (phagocytosis and ROS production). Responses were little affected by hemolymph serum (HS) as exposure medium in comparison to ASW. However, AgNPs significantly affected mitochondrial membrane potential and actin cytoskeleton at lower concentrations. AgNO₃ showed much higher toxicity, with an EC₅₀ = 1.23 μg/mL for LMS, decreased phagocytosis and induced mitochondrial and cytoskeletal damage at similar concentrations. Both AgNPs and AgNO₃ significantly affected Mytilus embryo development, with EC₅₀ = 23.7 and 1 μg/L, respectively. AgNPs caused malformations and developmental delay, but no mortality, whereas AgNO₃ mainly induced shell malformations followed by developmental arrest or death. Overall, the results indicate little toxicity of AgNPs compared with AgNO₃; moreover, the mechanisms of action of AgNP appeared to be distinct from those of Ag⁺. The results indicate little contribution of released Ag⁺ in our experimental conditions. These data provide a further insight into potential impact of AgNPs in marine invertebrates.

Cytotoxicity and genotoxicity of CuO nanoparticles in sea urchin spermatozoa through oxidative stress

Copper oxide nanoparticles (CuO NPs) are extensively used in various industrial and commercial applications. Despite their wide application may lead to the contamination of marine ecosystem, their potential environmental effects remain to be determined. Toxicity assessment studies have primarily focused on investigating the effects of CuO NPs on fertilization success and embryo development of different sea urchin species while the impact on sperm quality have never been assessed. In this line, this study aims to assess the effects of CuO NPs on the spermatozoa of the sea urchin Paracentrotus lividus. After sperm exposure to CuO NPs, biomarkers of sperm viability, cytotoxicity, oxidative stress, and genotoxicity as well as morphology were evaluated. Results showed that CuO NPs exposure decreased sperm viability, impaired mitochondrial activity and increased the production of reactive oxygen species (ROS) and lipid peroxidation. Furthermore, CuO NPs exposure caused DNA damage and morphological alterations. Together with the antioxidant rescue experiments, these results suggest that oxidative stress is the main driver of CuO NP spermiotoxic effects. The mechanism of toxicity is here proposed: the spontaneous generation of ROS induced by CuO NPs and the disruption of the mitochondrial respiratory chain lead to production of ROS that, in turn, induce lipid peroxidation and DNA damage, and result in defective spermatozoa up to induce sperm cytotoxicity. Investigating the effects of CuO NPs on sea urchin spermatozoa, this study provides valuable insights into the mechanism of reproductive toxicity induced by CuO NPs.

Mytilus galloprovincialis (Lamarck, 1819) spermatozoa: hsp70 expression and protamine-like protein property studies

In this work, we describe results of the reproductive health monitoring studies in Mytilus galloprovincialis following spermatozoa hsp70 expression and protamine-like protein properties. Mussels control (ctr) were released within cages for 30 days in three different marine sites near Naples (Campania, Italy): Bagnoli south (BAs) and Bagnoli north (BAn), both close to a disposal metallurgical factory and in Capo Miseno (CM). Studies of hsp70 gene expression carried out, by RT-qPCR, in mussel spermatozoa have shown varied expression levels, particularly 5, 13, and 15-fold more than ctr in CM, BAs, and BAn, respectively, indicating highest involvement of stress proteins in spermatozoa of mussels in Bagnoli. In order to evaluate the possible risk on Mytilus galloprovincialis sustainability loss, electrophoretic analyses were performed on protamine-like proteins (PL) of collected spermatozoa. The results showed that CM PL were apparently unaltered with respect to ctr PL, while BAs and BAn PL appeared in part in the form of peptides and in part as bands with low mobility. Further, CM and BAs PL showed, by electrophoretic mobility shift assay, a decrease in DNA binding ability and a change in their DNA binding mode. The results of this investigation show the usefulness of the study of alterations of spermatozoa hsp70 expression and protamine-like protein properties for eco-toxicological evaluation using Mytilus galloprovincialis as a bioindicator.

The characterization of iron (III) in seawater and related toxicity to early life stages of scleractinian corals

Currently toxicity data for iron (Fe) in seawater are limited; furthermore, these data are of poor quality as a result of the importance of Fe solubility in test solutions being overlooked. The present study characterized the solubility and lability of Fe(III) in seawater and then examined the effects of Fe(III) on the fertilization success and larval survival of the tropical marine scleractinian corals Acropora spathulata and Platygyra daedalea. We present the first assessment of the effects of Fe on the early life stages of scleractinian corals. Concentrations of both soluble and labile forms of Fe were very low, with dissolved Fe concentrations ≤0.195 mg/L in bioassay test solutions and chemical determinations revealing labile Fe concentrations ≤1.21 mg/L. For fertilization experiments, the median effect concentration (EC50) value for total Fe was 25 mg/L for the most sensitive species, P. daedalea, whereas the EC50 values for A. spathulata ranged between 40 and 66 mg/L. The median lethal concentration value for P. daedalea larval survival was 47 mg/L Fe after 72-h exposure. We provide Fe toxicity data for tropical marine keystone species that could be used to help generate more reliable guideline values for Fe in marine waters. Environ Toxicol Chem 2018;37:1104-1114. © 2017 SETAC.

Environmental transformations and ecological effects of iron-based nanoparticles

The increasing application of iron-based nanoparticles (NPs), especially high concentrations of zero-valent iron nanoparticles (nZVI), has raised concerns regarding their environmental behavior and potential ecological effects. In the environment, iron-based NPs undergo physical, chemical, and/or biological transformations as influenced by environmental factors such as pH, ions, dissolved oxygen, natural organic matter (NOM), and biotas. This review presents recent research advances on environmental transformations of iron-based NPs, and articulates their relationships with the observed toxicities. The type and extent of physical, chemical, and biological transformations, including aggregation, oxidation, and bio-reduction, depend on the properties of NPs and the receiving environment. Toxicities of iron-based NPs to bacteria, algae, fish, and plants are increasingly observed, which are evaluated with a particular focus on the underlying mechanisms. The toxicity of iron-based NPs is a function of their properties, tolerance of test organisms, and environmental conditions. Oxidative stress induced by reactive oxygen species is considered as the primary toxic mechanism of iron-based NPs. Factors influencing the toxicity of iron-based NPs are addressed and environmental transformations play a significant role, for example, surface oxidation or coating by NOM generally lowers the toxicity of nZVI. Research gaps and future directions are suggested with an aim to boost concerted research efforts on environmental transformations and toxicity of iron-based NPs, e.g., toxicity studies of transformed NPs in field, expansion of toxicity endpoints, and roles of laden contaminants and surface coating. This review will enhance our understanding of potential risks of iron-based NPs and proper uses of environmentally benign NPs.

In planta genotoxicity of nZVI: influence of colloidal stability on uptake, DNA damage, oxidative stress and cell death

Nanoremediation of soil, ground and surface water using nanoscale zerovalent iron particles (nZVI) has facilitated their direct environmental exposure posing ecotoxicological concerns. Numerous studies elucidate their phytotoxicity in terms of growth and their fate within the plant system. However, their potential genotoxicity and cytotoxicity mechanisms are not known in plants. This study encompasses the physico-chemical characterisation of two forms of nZVI (nZVI-1 and nZVI-2) with different surface chemistries and their influence on uptake, root morphology, DNA damage, oxidative stress and cell death in Allium cepa roots after 24 h. To our knowledge, this is the first report on the cyto-genotoxicity of nZVI in plants. The adsorption of nZVI on root surfaces caused root tip, epidermal and root hair damage as assessed by Scanning Electron Microscopy. nZVI-1, due to its colloidal destabilisation (low zeta potential, conductivity and high polydispersity index), smaller size and high uptake imparted enhanced DNA damage, chromosome/nuclear aberrations (CAs/NAs) and micronuclei formation compared to nZVI-2. Although nZVI-2 exhibited high zeta potential and conductivity, its higher dissolution and substantial uptake induced genotoxicity. nZVI incited the generation of reactive oxygen species (ROS) (hydrogen peroxide, superoxide and hydroxyl radicals) leading to membrane lipid peroxidation, electrolyte leakage and mitochondrial depolarisation. The inactivation of catalase and insignificant glutathione levels marked the onset of oxidative stress. Increased superoxide dismutase and guaiacol peroxidase enzyme activities, and proline content indicated the activation of antioxidant defence machinery to alleviate ROS. Moreover, ROS-mediated apoptotic and necrotic cell death occurred in both nZVI-1 and nZVI-2-treated roots. Our results open up further possibilities in the environmental safety appraisal of bare and modified nZVI in correlation with their physico-chemical characters.

Sensitivity of eastern oyster (Crassostrea virginica) spermatozoa and oocytes to dispersed oil: Cellular responses and impacts on fertilization and embryogenesis

The 2010 Deepwater Horizon (DWH) oil spill released millions of barrels of oil and dispersant into the Gulf of Mexico. The timing of the spill coincided with the spawning season of Crassostrea virginica. Consequently, gametes released in the water were likely exposed to oil and dispersant. This study aimed to (i) evaluate the cellular effects of acute exposure of spermatozoa and oocytes to surface slick oil, dispersed mechanically (HEWAF) and chemically (CEWAF), using flow-cytometric (FCM) analyses, and (ii) determine whether the observed cellular effects relate to impairments of fertilization and embryogenesis of gametes exposed to the same concentrations of CEWAF and HEWAF. Following a 30-min exposure, the number of spermatozoa and their viability were reduced due to a physical action of oil droplets (HEWAF) and a toxic action of CEWAF respectively. Additionally, reactive oxygen species (ROS) production in exposed oocytes tended to increase with increasing oil concentrations suggesting that exposure to dispersed oil resulted in an oxidative stress. The decrease in fertilization success (1-h), larval survival (24-h) and increase in abnormalities (6-h and 24-h) may be partly related to altered cellular characteristics. FCM assays are a good predictor of sublethal effects especially on fertilization success. These data suggest that oil/dispersant are cytotoxic to gametes, which may affect negatively the reproduction success and early development of oysters.

The interactions between nanoscale zero-valent iron and microbes in the subsurface environment: A review

Nanoscale zero-valent iron (NZVI) particles, applied for in-situ subsurface remediation, are inevitable to interact with various microbes in the remediation sites directly or indirectly. This review summarizes their interactions, including the effects of NZVI on microbial activity and growth, the synergistic effect of NZVI and microbes on the contaminant removal, and the effects of microbes on the aging of NZVI. NZVI could exert either inhibitive or stimulative effects on the growth of microbes. The mechanisms of NZVI cytotoxicity (i.e., the inhibitive effect) include physical damage and biochemical destruction. The stimulative effects of NZVI on certain bacteria are associated with the creation of appropriate living environment, either through providing electron donor (e.g., H₂) or carbon sources (e.g., the engineered organic surface modifiers), or through eliminating the noxious substances that can cause bactericidal consequence. As a result of the positive interaction, the combination of NZVI and some microbes shows synergistic effect on contaminant removal. Additionally, the aged NZVI can be utilized by some iron-reducing bacteria, resulting in the transformation of Fe(III) to Fe(II), which can further contribute to the contaminant reduction. However, the Fe(III)-reduction process can probably induce environmental risks, such as environmental methylation and remobilization of the previously entrapped heavy metals.

Toxicity of iron-based nanoparticles to green algae: Effects of particle size, crystal phase, oxidation state and environmental aging

With the increasing environmental application and discharge of iron-based nanoparticles (NPs), a comprehensive understanding of their fate and ecotoxicological effect in the aquatic environment is very urgent. In this study, toxicities of 4 zero-valent iron NPs (nZVI) of different sizes, 2 Fe₂O₃ NPs of different crystal phases, and 1 type of Fe₃O₄ NPs to a green alga (Chlorella pyrenoidosa) were investigated, with a focus on the effects of particle size, crystal phase, oxidation state, and environmental aging. Results show that the algal growth inhibition of nZVI increased significantly with decreasing particle size; with similar particle sizes (20-30 nm), the algal growth inhibition decreased with oxidation of the NPs with an order of nZVI > Fe₃O₄ NPs > Fe₂O₃ NPs, and α-Fe₂O₃ NPs presented significantly higher toxicity than γ-Fe₂O₃ NPs. The NP-induced oxidative stress was the main toxic mechanism, which could explain the difference in algal toxicity of the NPs. The NP-cell heteroagglomeration and physical interactions also contributed to the nanotoxicity, whereas the effect of NP dissolution was negligible. The aging in distilled water and 3 surface water samples for 3 months increased surface oxidation of the iron-based NPs especially nZVI, which decreased the toxicity to algae. These findings will be helpful for the understanding of the fate and toxicity of iron-based NPs in the aquatic environment.

Review: Morphofunctional and biochemical markers of stress in sea urchin life stages exposed to engineered nanoparticles

We describe the use of different life stages of the Mediterranean sea urchin Paracentrotus lividus for the assessment of the possible risk posed by nanoparticles (NPs) in the coastal water. A first screening for the presence of NPs in sea water may be obtained by checking their presence inside tissues of organisms taken from the wild. The ability of NPs to pass from gut to the coelomic fluid is demonstrated by accumulation in sea urchin coelomocytes; the toxicity on sperms can be measured by embryotoxicity markers after sperm exposure, whereas the transfer through the food chain can be observed by developmental anomalies in larvae fed with microalgae exposed to NPs. The most used spermiotoxicity and embryotoxicity tests are described, as well as the biochemical and histochemical analyses of cholinesterase (ChE) activities, which are used to verify toxicity parameters such as inflammation, neurotoxicity, and interference in cell-to-cell communication. Morphological markers of toxicity, in particular skeletal anomalies, are described and classified. In addition, NPs may impair viability of the immune cells of adult specimens. Molecular similarity between echinoderm and human immune cells is shown and discussed. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1552-1562, 2016.

Dissolved Organic Matter or Salts Change the Bioavailability Processes and Toxicity of the Nanoscale Tetravalent Lead Corrosion Product PbO2 to Medaka Fish

Nanoscale lead dioxide (nPbO_2(s)) is a corrosion product formed from the chlorination of lead-containing plumbing materials. This metal oxide nanoparticle (NP) plays a key role in determining lead pollution in drinking water and receiving water bodies. This study uses nPbO_2(s) and medaka fish (Oryzias latipes) as surrogates to investigate the aqueous fate and toxicological risk of metal oxide NPs associated with water matrices. The larvae of medaka were treated with solutions containing nPbO_2(s) or Pb(II)_aq in different water matrices for 7-14 days to investigate the in vivo toxic effects of NPs. Ionic strength enhanced aggregation and sedimentation of nPbO_2(s) in water, leading to increased lead contents in fish bodies. However, the presence of dissolved organic matter in water enhanced particle stability and accelerated the lead dissolution, thus changing the bioavailability processes (bioaccessibility) of particles. Oxidative stress response and neurotoxicity in exposed fish was greater for nPbO_2(s) solution with increased salinity than dissolved organic matter. We predict the bioavailability processes and toxicity of nPbO_2(s) in medaka from the aqueous particle behavior under environmentally relevant exposure conditions. Our investigation suggests a toxicological risk of metal oxide NP pollution in the aquatic environment.

Spermiotoxicity of nickel nanoparticles in the marine invertebrate Ciona intestinalis (ascidians)

Nickel nanoparticles (Ni NPs) are increasingly used in modern industries as catalysts, sensors, and in electronic applications. Due to this large use, their inputs into marine environment have significantly increased; however, the potential ecotoxicological effects in marine environment have so far received little attention. In particular, little is known on the impact of NPs on gamete quality of marine organisms and on the consequences on fertility potential. The present study examines, for the first time, the impact of Ni NPs exposure on sperm quality of the marine invertebrate Ciona intestinalis (ascidian). Several parameters related with sperm status such as plasma membrane lipid peroxidation, mitochondrial membrane potential (MMP), intracellular pH, DNA integrity, and fertilizing ability were assessed as toxicity end points after exposure to different Ni NPs concentrations. Ni NPs generate oxidative stress that in turn induces lipid peroxidation and DNA fragmentation, and alters MMP and sperm morphology. Furthermore, sperm exposure to Ni NPs affects their fertilizing ability and causes developmental anomalies in the offspring. All together, these results reveal a spermiotoxicity of Ni NPs in ascidians suggesting that the application of these NPs should be carefully assessed as to their potential toxic effects on the health of marine organisms that, in turn, may influence the ecological system. This study shows that ascidian sperm represent a suitable and sensitive tool for the investigation of the toxicity of NPs entered into marine environment, for defining the mechanisms of toxic action and for the environmental monitoring purpose.

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.

Evaluating the mobility of polymer-stabilised zero-valent iron nanoparticles and their potential to co-transport contaminants in intact soil cores

The use of zero-valent iron nanoparticles (nZVI) has been advocated for the remediation of both soils and groundwater. A key parameter affecting nZVI remediation efficacy is the mobility of the particles as this influences the reaction zone where remediation can occur. However, by engineering nZVI particles with increased stability and mobility we may also inadvertently facilitate nZVI-mediated contaminant transport away from the zone of treatment. Previous nZVI mobility studies have often been limited to model systems as the presence of background Fe makes detection and tracking of nZVI in real systems difficult. We overcame this problem by synthesising Fe-59 radiolabelled nZVI. This enabled us to detect and quantify the leaching of nZVI-derived Fe-59 in intact soil cores, including a soil contaminated by Chromated-Copper-Arsenate. Mobility of a commercially available nZVI was also tested. The results showed limited mobility of both nanomaterials; <1% of the injected mass was eluted from the columns and most of the radiolabelled nZVI remained in the surface soil layers (the primary treatment zone in this contaminated soil). Nevertheless, the observed breakthrough of contaminants and nZVI occurred simultaneously, indicating that although the quantity transported was low in this case, nZVI does have the potential to co-transport contaminants. These results show that direct injection of nZVI into the surface layers of contaminated soils may be a viable remediation option for soils such as this one, in which the mobility of nZVI below the injection/remediation zone was very limited. This Fe-59 experimental approach can be further extended to test nZVI transport in a wider range of contaminated soil types and textures and using different application methods and rates. The resulting database could then be used to develop and validate modelling of nZVI-facilitated contaminant transport on an individual soil basis suitable for site specific risk assessment prior to nZVI remediation.

In vivo exposure of the marine clam Ruditapes philippinarum to zinc oxide nanoparticles: responses in gills, digestive gland and haemolymph

Potential nanoparticle (NP) toxicity poses a growing concern in marine coastal environments. Among NPs, zinc oxide nanoparticles (nZnO) are widely used in many common products that ultimately become deposited in coastal habitats from multiple non-point sources. In this study, we evaluated the in vivo effects of nZnO in the clam Ruditapes philippinarum. Animals were exposed to nZnO (1 and 10 μg/L) and ZnCl2 (10 μg/L) for 7 days. ZnCl2 was used to compare the effects of the NPs to those of Zn(2+) and to ascertain whether nZnO toxicity is attributable to the release of ions into the aquatic medium. At differing time intervals during the exposure, several biochemical and cellular responses were evaluated in the clam gills, digestive gland, and haemolymph. The results showed that nZnO, at concentrations close to the predicted environmental levels, significantly affected various parameters in clam tissues. Significant increases in catalase and superoxide dismutase activities and a decreasing trend of glutathione S-transferase activity indicated the involvement of oxidative stress in nZnO toxicity. In clams exposed to ZnCl2, slight variations in antioxidant enzyme activities were detected with respect to nZnO-treated clams. However, no damage to lipids, proteins or DNA was revealed in all exposure conditions, suggesting a protection of antioxidant enzymes in the tissues. Of the various haemolymph parameters measured, haemocyte proliferation increased significantly, in ZnCl2-treated clams in particular. Under nZnO (10 μg/L) and ZnCl2 exposure, DNA damage in haemocytes was also revealed, but it was lower in clams exposed to ZnCl2. A decreasing trend in gill AChE activity of treated clams proposed a possible role of zinc ions in nZnO toxicity. However, the dissimilar modulation of the responses in the nZnO- and ZnCl2-exposed clams suggested different mechanisms of action, with nZnO toxicity possibly depending not only on the release of zinc ions but also on NP-specific features. Changes in the biological parameters measured in the clams were consistent with Zn accumulation in their gills and digestive glands.

Effect of injection velocity and particle concentration on transport of nanoscale zero-valent iron and hydraulic conductivity in saturated porous media

Successful groundwater remediation by injecting nanoscale zero-valent iron (NZVI) particles requires efficient particle transportation and distribution in the subsurface. This study focused on the influence of injection velocity and particle concentration on the spatial NZVI particle distribution, the deposition processes and on quantifying the induced decrease in hydraulic conductivity (K) as a result of particle retention by lab tests and numerical simulations. Horizontal column tests of 2m length were performed with initial Darcy injection velocities (q0) of 0.5, 1.5, and 4.1m/h and elemental iron input concentrations (Fe(0)in) of 0.6, 10, and 17g/L. Concentrations of Fe(0) in the sand were determined by magnetic susceptibility scans, which provide detailed Fe(0) distribution profiles along the column. NZVI particles were transported farther at higher injection velocity and higher input concentrations. K decreased by one order of magnitude during injection in all experiments, with a stronger decrease after reaching Fe(0) concentrations of about 14-18g/kg(sand). To simulate the observed nanoparticle transport behavior the existing finite-element code OGS has been successfully extended and parameterized for the investigated experiments using blocking, ripening, and straining as governing deposition processes. Considering parameter relationships deduced from single simulations for each experiment (e.g. deposition rate constants as a function of flow velocity) one mean parameter set has been generated reproducing the observations in an adequate way for most cases of the investigated realistic injection conditions. An assessment of the deposition processes related to clogging effects showed that the percentage of retention due to straining and ripening increased during experimental run time resulting in an ongoing reduction of K. Clogging is mainly evoked by straining which dominates particle deposition at higher flow velocities, while blocking and ripening play a significant role for attachment, mainly at lower injection velocities. Since the injection of fluids at real sites leads to descending flow velocities with increasing radial distance from the injection point, the simulation of particle transport requires accounting for all deposition processes mentioned above. Thus, the derived mean parameter set can be used as a basis for quantitative and predictive simulations of particle distributions and clogging effects at both lab and field scale. Since decreases in K can change the flow system, which may have positive as well as negative implications for the in situ remediation technology at a contaminated site, a reliable simulation is thus of great importance for NZVI injection and prediction.

Nanoscale zerovalent iron (nZVI) at environmentally relevant concentrations induced multigenerational reproductive toxicity in Caenorhabditis elegans

Nanoscale zerovalent iron (nZVI) is widely used with large scale for environmental remediation for in situ or ex situ applications. The potential impact of nZVI on biota at environmentally relevant concentrations needs to be elucidated. In this study, the reproductive toxicities of three irons species: carboxymethyl cellulose (CMC)-stabilized nZVI, nanoscale iron oxide (nFe3O4), and ferrous ion (Fe(II)aq) in the soil-dwelling nematode Caenorhabditis elegans were examined. In addition, the generational transfer of reproductive toxicity of CMC-nZVI on C. elegans was investigated. The results showed that CMC-nZVI, nFe3O4, and Fe(II)aq did not cause significant mortality after 24 h exposure at the examined concentrations. Reproductive toxicity assays revealed that CMC-nZVI, nFe3O4, and Fe(II)aq significantly decreased offsprings in parental generation (F0) in accompany with the increased intracellular reactive oxygen species (ROS). Furthermore, the reproductive toxicity of CMC-nZVI at environmentally relevant concentrations was transferrable from the F0 to the F1 and F2 generations, but then recovered in the F3 and F4 generations. Further evidence showed that total irons were accumulated in the F0 and F1 generations of C. elegans after CMC-nZVI parental exposure. This study demonstrated that environmentally relevant concentrations of CMC-nZVI induced multigenerational reproductive toxicity which can be ascribed to its high production of ROS in F0 generation, toxicity of Fe(II)aq, and iron accumulation in C. elegans. Since nZVI is widely used for environmental remediation, considering the multigenerational toxicity, this study thus implicates a potential environmental risk of nZVI-induced nanotoxicity in the environment.

Higher concentrations of nanoscale zero-valent iron (nZVI) in soil induced rice chlorosis due to inhibited active iron transportation

In this study, the effects of concentrations 0, 100, 250, 500, 750 and 1000 mg kg(-1) of nanoscale zero-valent iron (nZVI) on germination, seedlings growth, physiology and toxicity mechanisms were investigated. The results showed that nZVI had no effect on germination, but inhibited the rice seedlings growth in higher concentrations (>500 mg kg(-1) nZVI). The highest suppression rate of the length of roots and shoots reached 46.9% and 57.5%, respectively. The 1000mg kg(-1) nZVI caused the highest suppression rates for chlorophyll and carotenoids, at 91.6% and 85.2%, respectively. In addition, the activity of antioxidant enzymes was altered by the translocation of nanoparticles and changes in active iron content. Visible symptoms of iron deficiency were observed at higher concentrations, at which the active iron content decreased 61.02% in the shoots, but the active iron content not decreased in roots. Interestingly, the total and available amounts of iron in the soil were not less than those in the control. Therefore, the plants iron deficiency was not caused by (i) deficiency of available iron in the soil and (ii) restraint of the absorption that plant takes in the available iron, while induced by (ⅲ) the transport of active iron from the root to the shoot was blocked. The cortex tissues were seriously damaged by nZVI which was transported from soil to the root, these were proved by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). This current study shows that the mechanism of iron deficiency in rice seedling was due to transport of active iron from the root to the shoot blocked, which was caused by the uptake of nZVI.

A comparative study with biologically and chemically synthesized nZVI: applications in Cr (VI) removal and ecotoxicity assessment using indigenous microorganisms from chromium-contaminated site

In the present communication, we report a comparative study of Cr (VI) removal using biologically synthesized nano zero valent iron (BS-nZVI) and chemically synthesized nZVI (CS-nZVI), both immobilized in calcium alginate beads. The parameters like initial Cr (VI) concentration, nZVI concentration, and the contact time for Cr (VI) removal were optimized based on Box-Behnken design (BBD) by response surface modeling at a constant pH 7. Under the optimized conditions (concentration of nZVI = 1000 mg L(-1), contact time = ∼ 80 min, and initial concentration of Cr (VI) = 10 mg L(-1)), the Cr (VI) removal by the immobilized BS-nZVI and CS-nZVI alginate beads was 80.04 and 81.08 %, respectively. The adsorption of Cr (VI) onto the surface of alginate beads was confirmed by scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM-EDX), Fourier transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) analysis. The applicability of the process using both the sorbents was successfully test medium Cr (VI) spiked environmental water samples. In order to assess the ecotoxic effects of nZVI, the decline in cell viability, generation of intracellular reactive oxygen species (ROS), cell membrane damage, and biouptake was studied at 1000 mg L(-1) concentration, with five indigenous bacterial isolates from chromium-contaminated lake sediments and their consortium.

Dynamic changes in the sperm quality of Mytilus galloprovincialis under continuous thermal stress

Global warming is an increasingly serious problem underlying ecological change in marine flora and fauna. Mytilus galloprovincialis is an intertidal species that colonizes coasts in moderate and warm climates, and can thus withstand extreme climatic conditions; however, it successfully reproduces only within a certain temperature range. The effects of prolonged exposure to 28 °C, a temperature unsuitable for breeding activity, on sperm quality were evaluated in this study. Such heat stress induced the following: a significant reduction in concentration; a biphasic pattern of motility and mitochondrial membrane potential that first increased, and then collapsed; a decrease in the intracellular calcium concentration; a rapid increase in lipid peroxidation that was normalized after the third week of heat stress; an increase in DNA fragmentation after the third week of heat stress; and atypical morphology (i.e., sperm with a globular head, asymmetrical tail, and acrosome loss). Currently, these elevated-temperature conditions are achieved along the Mediterranean coast during the late summer, when the reproductive activity of M. galloprovincialis is suspended after massive spawning in the spring. The increasing global temperature, however, may shift their breeding season, thus significantly impacting marine ecosystems and mussel production.

Ecotoxicological impact of engineered nanomaterials in bivalve molluscs: An overview

The increasing production and application of engineered nanomaterials (ENMs) in consumer products over the past decade will inevitably lead to their release into aquatic systems and thereby cause the exposure to aquatic organisms, resulting in growing environmental and human health concern. Since bivalves are widely used in the monitoring of aquatic pollution, the aim of this review was to compile and analyse data concerning the ecotoxicity of ENMs using bivalve molluscs. The state of the art regarding the experimental approach, characterization, behaviour, fate, bioaccumulation, tissue and subcellular distribution and mechanisms of toxicity of ENMs in marine and freshwater bivalve molluscs is summarized to achieve a new insight into the mode of action of these nanoparticles in invertebrate organisms. This review shows that the studies about the toxic effects of ENMs in bivalves were conducted mainly with seawater species compared to freshwater ones and that the genus Mytilus is the main taxa used as a model system. There is no standardization of experimental approaches for toxicity testing and reviewed data indicate the need to develop standard protocols for ENMs ecotoxicological testing. In general, the main organ for ENM accumulation is the digestive gland and their cellular fate differs according to nano-specific properties, experimental conditions and bivalve species. Endosomal-lysosomal system and mitochondria are the major cellular targets of ENMs. Metal based ENMs mode of action is related mainly to the dissolution and/or release of the chemical component of the particle inducing immunotoxicity, oxidative stress and cellular injury to proteins, membrane and DNA damage. This review indicates that the aquatic environment is the potential ultimate fate for ENMs and confirms that bivalve molluscs are key model species for monitoring aquatic pollution by ENMs.

Methods for characterizing the fate and effects of nano zerovalent iron during groundwater remediation

The emplacement of nano zerovalent iron (nZVI) for groundwater remediation is usually monitored by common measurements such as pH, total iron content, and oxidation-reduction potential (ORP) by potentiometry. However, the interpretation of such measurements can be misleading because of the complex interactions between the target materials (e.g., suspensions of highly reactive and variably aggregated nanoparticles) and aquifer materials (sediments and groundwater), and multiple complications related to sampling and detection methods. This paper reviews current practice for both direct and indirect characterizations of nZVI during groundwater remediation and explores prospects for improving these methods and/or refining the interpretation of these measurements. To support our recommendations, results are presented based on laboratory batch and column studies of nZVI detection using chemical, electrochemical, and geophysical methods. Chemical redox probes appear to be a promising new method for specifically detecting nZVI, based on laboratory tests. The potentiometric and voltammetric detections of iron nanoparticles, using traditional stationary disc electrodes, rotating disc electrodes, and flow-through cell disc electrodes, provide insight for interpreting ORP measurements, which are affected by solution chemistry conditions and the interactions between iron nanoparticles and the electrode surface. The geophysical methods used for characterizing ZVI during groundwater remediation are reviewed and its application for nZVI detection is assessed with results of laboratory column experiments.

Mutagenic Effects of Iron Oxide Nanoparticles on Biological Cells

In recent years, there has been an increased interest in the design and use of iron oxide materials with nanoscale dimensions for magnetic, catalytic, biomedical, and electronic applications. The increased manufacture and use of iron oxide nanoparticles (IONPs) in consumer products as well as industrial processes is expected to lead to the unintentional release of IONPs into the environment. The impact of IONPs on the environment and on biological species is not well understood but remains a concern due to the increased chemical reactivity of nanoparticles relative to their bulk counterparts. This review article describes the impact of IONPs on cellular genetic components. The mutagenic impact of IONPs may damage an organism's ability to develop or reproduce. To date, there has been experimental evidence of IONPs having mutagenic interactions on human cell lines including lymphoblastoids, fibroblasts, microvascular endothelial cells, bone marrow cells, lung epithelial cells, alveolar type II like epithelial cells, bronchial fibroblasts, skin epithelial cells, hepatocytes, cerebral endothelial cells, fibrosarcoma cells, breast carcinoma cells, lung carcinoma cells, and cervix carcinoma cells. Other cell lines including the Chinese hamster ovary cells, mouse fibroblast cells, murine fibroblast cells, Mytilus galloprovincialis sperm cells, mice lung cells, murine alveolar macrophages, mice hepatic and renal tissue cells, and vero cells have also shown mutagenic effects upon exposure to IONPs. We further show the influence of IONPs on microorganisms in the presence and absence of dissolved organic carbon. The results shed light on the OPEN ACCESS Int. J. Mol. Sci. 2015, 16 23483 transformations IONPs undergo in the environment and the nature of the potential mutagenic impact on biological cells.

Effect of geochemical properties on degradation of trichloroethylene by stabilized zerovalent iron nanoparticle with Na-acrylic copolymer

Stable nanoscale zero-valent iron (NZVI) particles have been developed to remediate chlorinated compounds. The degradation kinetics and efficiency of trichloroethylene (TCE) by a commercial stabilized NZVI with Na-acrylic copolymer (acNZVI) were investigated and compared with those by laboratory-synthesized NZVI and carboxymethyl cellulose (CMC)-stabilized NZVI particles. Results show that the degradation of TCE by acNZVI was faster than that by NZVI and CMC-NZVI. Increase in temperature enhanced the degradation rate and efficiency of TCE with acNZVI. The activation energy of TCE degradation by acNZVI was estimated to be 23 kJ/mol. The degradation rate constants of TCE decreased from 0.064 to 0.026 min(-1) with decrease in initial pH from 9.03 to 4.23. Common groundwater anions including NO3(-), Cl(-), HCO3(-), and SO4(2-) inhibited slightly the degradation efficiencies of TCE by acNZVI. The Na-acrylic copolymer-stabilized NZVI, which exhibited high degradation kinetics and efficiency, could be a good remediation agent for chlorinated organic compounds.

Common strategies and technologies for the ecosafety assessment and design of nanomaterials entering the marine environment

The widespread use of engineered nanomaterials (ENMs) in a variety of technologies and consumer products inevitably causes their release into aquatic environments and final deposition into the oceans. In addition, a growing number of ENM products are being developed specifically for marine applications, such as antifouling coatings and environmental remediation systems, thus increasing the need to address any potential risks for marine organisms and ecosystems. To safeguard the marine environment, major scientific gaps related to assessing and designing ecosafe ENMs need to be filled. In this Nano Focus, we examine key issues related to the state-of-the-art models and analytical tools being developed to understand ecological risks and to design safeguards for marine organisms.

The interaction of polymer-coated magnetic nanoparticles with seawater

Laboratory studies were conducted to evaluate the interaction between bare and polymer-coated magnetic nanoparticles (MNPs) with various environmentally relevant carrying solutions including natural oceanic seawater with and without addition of algal exopolymeric substances (EPS). The MNPs were coated with three different stabilising agents, namely gum Arabic (GA-MNP), dextran (D-MNP) and carboxymethyl-dextran (CMD-MNP). The colloidal stability of the suspensions was evaluated over 48 h and we demonstrated that: (i) hydrodynamic diameters increased over time regardless of carrying solution for all MNPs except the GA-coated ones; however, the relative changes were carrying solution- and coat-dependent; (ii) polydispersity indexes of the freshly suspended MNPs are below 0.5 for all coated MNPs, unlike the much higher values obtained for the uncoated MNPs; (iii) freshly prepared MNP suspensions (both coated and uncoated) in Milli-Q (MQ) water show high colloidal stability as indicated by zeta-potential values below -30 mV, which however decrease in absolute value within 48 h for all MNPs regardless of carrying solution; (iv) EPS seems to "stabilise" the GA-coated and the CMD-coated MNPs, but not the uncoated or the D-coated MNPs, which form larger aggregates within 48 h; (v) despite this aggregation, iron (Fe)-leaching from MNPs is sustained over 48h, but remained within the range of 3-9% of the total iron-content of the initially added MNPs regardless of suspension media and capping agent. The environmental implications of our findings and biotechnological applicability of MNPs are discussed.

Mobility enhancement of nanoscale zero-valent iron in carbonate porous media through co-injection of polyelectrolytes

The mobility of nanoscale zero-valent iron (nZVI), which is used for in situ groundwater remediation, is affected by chemical and physical heterogeneities within aquifers. Carbonate minerals in porous aquifers and the presence of divalent cations reduce nZVI mobility. This study assesses the potential for enhancing the mobility of polyacrylic acid coated nZVI (PAA-nZVI) in such aquifers through the co-injection of polyelectrolytes (natural organic matter, humic acid, carboxymethyl cellulose, and lignin sulfonate). When applied at the same concentration, all of the polyelectrolytes produced similar enhancement of PAA-nZVI mobility in carbonate porous media. This increase in mobility was a result of increased repulsion between PAA-nZVI and the carbonate matrix. Lignin sulfonate, an environmentally friendly and inexpensive agent, was identified as the most suitable polyelectrolyte for field applications. The greatest increase in PAA-nZVI mobility was achieved with co-injection of lignin sulfonate at concentrations ≥50 mg L(-1); at these concentrations the maximum PAA-nZVI travel distance in carbonate porous media was twice of that in the absence of lignin sulfonate.

Potential environmental implications of nanoscale zero-valent iron particles for environmental remediation

OBJECTIVES

Nanoscale zero-valent iron (nZVI) particles are widely used in the field of various environmental contaminant remediation. Although the potential benefits of nZVI are considerable, there is a distinct need to identify any potential risks after environmental exposure. In this respect, we review recent studies on the environmental applications and implications of nZVI, highlighting research gaps and suggesting future research directions.

METHODS

Environmental application of nZVI is briefly summarized, focusing on its unique properties. Ecotoxicity of nZVI is reviewed according to type of organism, including bacteria, terrestrial organisms, and aquatic organisms. The environmental fate and transport of nZVI are also summarized with regards to exposure scenarios. Finally, the current limitations of risk determination are thoroughly provided.

RESULTS

The ecotoxicity of nZVI depends on the composition, concentration, size and surface properties of the nanoparticles and the experimental method used, including the species investigated. In addition, the environmental fate and transport of nZVI appear to be complex and depend on the exposure duration and the exposure conditions. To date, field-scale data are limited and only short-term studies using simple exposure methods have been conducted.

CONCLUSIONS

In this regard, the primary focus of future study should be on 1) the development of an appropriate and valid testing method of the environmental fate and ecotoxicity of reactive nanoparticles used in environmental applications and 2) assessing their potential environmental risks using in situ field scale applications.

Embryotoxicity of TiO2 nanoparticles to Mytilus galloprovincialis (Lmk)

Few data exist on the ecotoxicological effects of nanosized titanium dioxide (nTiO2) towards marine species with specific reference to bivalve molluscs and their relative life stages. Mytilus galloprovincialis Lamarck was selected to assess the potential adverse effects of nTiO2 (0-64 mg/L) on its early larval development stages (pre-D shell stage, malformed D-shell stage and normal D-shell stage larvae) considering two exposure scenarios characterised by total darkness (ASTM protocol) and natural photoperiod (light/dark). This approach was considered to check the presence of potential effects associated to the photocatalytic properties of nTiO2. Parallel experiments were carried on with the bulk reference TiCl4. The toxicity of nTiO2 showed to be mainly related to its "nano" condition and to be influenced by the exposure to light that supported the increase in the number of pre-D shell stage (retarded) larvae compared to the malformed ones especially at the maximum effect concentrations (4 and 8 mg nTiO2/L). The non-linear regression toxicity data analysis showed the presence of two EC50 values per exposure scenario: a) EC(50)1 = 1.23 mg/L (0.00-4.15 mg/L) and EC(50)2 = 38.56 mg/L (35.64-41.47 mg/L) for the dark exposure conditions; b) EC(50)1 = 1.65 mg/L (0.00-4.74 mg/L) and EC(50)2 = 16.39 mg/L (13.31-19.48 mg/L) for the light/dark exposure conditions. The potential implication of agglomeration and sedimentation phenomena on ecotoxicological data was discussed.

The zerovalent iron nanoparticle causes higher developmental toxicity than its oxidation products in early life stages of medaka fish

Nanoscale zerovalent iron (nZVI)-mediated oxidation reaction is increasingly being used for enhanced treatment of water or wastewater processes; however, the fate and eco-toxicological effects of nZVI in the surface aquifer remain unclear. We investigated bioaccumulation and lethal-to-sublethal toxic effects on early life development of Japanese medaka (Oryzias latipes) with 7-day exposure to 25-200 mg/L of well-characterized solutions containing carboxymethyl cellulose (CMC)-stabilized nZVI (CMC-nZVI), nanoscale iron oxide (nFe3O4) or ferrous ion [Fe(II)aq]. The CMC-nZVI solution had the greatest acute mortality and developmental toxic effects in embryos, with lesser and the least effects with Fe(II)aq and nFe3O4. The toxicity of CMC-nZVI was ascribed to its high reactivity in the oxygenic solution, which led to a combination of hypoxia and production of reactive oxygen species (ROS) and Fe(II)aq. nFe3O4 (50-100 mg/L) was more bioavailable to embryos and bioaccmulative in hatchlings than suspended CMC-nZVI. The antioxidant balance was differentially altered by induced intracellular ROS in hatchlings with all 3 iron species. We revealed causal toxic effects of nZVI and its oxidized products in early life stages of medaka fish using different organizational levels of biomarker assays. The toxicity results implicate a potential eco-toxicological impact of nZVI on the aquatic environment.

Carbonate minerals in porous media decrease mobility of polyacrylic acid modified zero-valent iron nanoparticles used for groundwater remediation

The limited transport of nanoscale zero-valent iron (nZVI) in porous media is a major obstacle to its widespread application for in situ groundwater remediation. Previous studies on nZVI transport have mainly been carried out in quartz porous media. The effect of carbonate minerals, which often predominate in aquifers, has not been evaluated to date. This study assessed the influence of the carbonate minerals in porous media on the transport of polyacrylic acid modified nZVI (PAA-nZVI). Increasing the proportion of carbonate sand in the porous media resulted in less transport of PAA-nZVI. Predicted travel distances were reduced to a few centimeters in pure carbonate sand compared to approximately 1.6 m in quartz sand. Transport modeling showed that the attachment efficiency and deposition rate coefficient increased linearly with increasing proportion of carbonate sand.

Preparation of magnetic recoverable nanosize Cu-Fe2O3/Fe photocatalysts

Iron based catalysts generally have the advantage of the easily operated magnetically recovery from application sites. In the present work, paramagnetic iron and copper core-shell nanoparticles having the iron fractions (X(Fe) = Fe/(Cu+Fe)) of 0.33-1.0 were prepared and characterized by in situ synchrotron X-ray absorption and scattering spectroscopy. During the temperature-programmed carbonization (TPC) of Cu(2+)- and Fe(3+)-β-cyclodextrin (CD) complexes, a rapid reduction of Cu(II) occurs at about 453 K together with a growth of the metallic copper (Cu). Iron proceeds in the distinct growth path. At 453-513 K, the Fe(III) → Fe(II) → Fe consecutive reduction is observed. The unreduced Fe(III) (7-13%) is coated on the surfaces of the Fe nanoparticles (as Fe2O3/Fe). Growth of the Fe nanoparticle is inhibited by the surface Fe2O3, while the steady growth in Cu is observed. The Cu has a size range of 14-18 nm in diameter, compared to the small Fe2O3/Fe ones (3-6 nm). Under the UV-visible light irradiation for four hours, methylene blue can be photocatalytically degraded (>90%) by the (Cu-Fe2O3/Fe)@C. The (Cu-Fe2O3/Fe)@C photocatalysts can effectively oxidize dye molecules, providing a promising alternative for dye degradation using solar energy. Recovery of the (Cu-Fe2O3/Fe)@C photocatalysts can be attained by applying external magnetic field to trap the ferromagnetic Cu-Fe2O3/Fe nanoparticles, which suggests an economically attractive process, especially applied in photocatalytic degradation of dye-contaminated wastewater.

Genotoxicity of copper oxide and silver nanoparticles in the mussel Mytilus galloprovincialis

Though there is some information on cytotoxicity of copper nanoparticles and silver nanoparticles on human cell lines, there is no information on their genotoxic and cytotoxic behaviour in bivalve molluscs. The aim of this study was to investigate the genotoxic impact of copper oxide and silver nanoparticles using mussels Mytilus galloprovincialis. Mussels were exposed to 10 μg L⁻¹ of CuO nanoparticles and Cu²⁺ and Ag nanoparticles and Ag⁺ for 15 days to assess genotoxic effects in hemocytes using the comet assay. The results obtained indicated that copper and silver forms (nanoparticles and ionic) induced DNA damage in hemolymph cells and a time-response effect was evident when compared to unexposed mussels. Ionic forms presented higher genotoxicity than nanoparticles, suggesting different mechanisms of action that may be mediated through oxidative stress. DNA strand breaks proved to be a useful biomarker of exposure to genotoxic effects of CuO and Ag nanoparticles in marine molluscs.

A mesocosm study of fate and effects of CuO nanoparticles on endobenthic species (Scrobicularia plana, Hediste diversicolor)

The fate and effects of CuO nanoparticles (CuO NPs) were examined in endobenthic species (Scrobicularia plana , Hediste diversicolor), under environmentally realistic conditions in outdoor mesocosms (exposure to Cu at 10 μg L(-1) in particulate (CuO NPs) or soluble salt (CuNO(3)) forms) for 21 days. Labile Cu was determined in water and sediment by using diffusive gradient in thin films. No labile Cu being detected from CuO NPs; the observed effects in invertebrates exposed to CuO NPs were mainly attributed to the toxicity of nanoparticulate rather than dissolved Cu toxicity. Bioaccumulation of CuO NPs was observed in both species. Biomarkers were examined at different levels of biological organization: biochemical markers of defense and damage, biomarkers of genotoxicity (comet assay), and behavioral biomarkers (feeding and burrowing). Behavioral biomarkers, antioxidant defenses (catalase, glutathion S-transferase, metallothionein), and genotoxicity are the most sensitive tools to highlight the effect of soluble or nanoparticulate metal forms. Concerning other biomarkers of defense (superoxide dismutase, lactate dehydrogenase, laccase) and damage (thiobarbituric acid reactive substances, acetylcholinesterase, acid phosphatase), no significant effects were detected. This experiment shows the suitability of mesocosms for studying the environmental effects of nanoparticles.

The effect of engineered iron nanoparticles on growth and metabolic status of marine microalgae cultures

Synthetic zero-valent nano-iron (nZVI) compounds are finding numerous applications in environmental remediation owing to their high chemical reactivity and versatile catalytic properties. Studies were carried out to assess the effects of three types of industrially relevant engineered nZVI on phytoplankton growth, cellular micromorphology and metabolic status. Three marine microalgae (Pavlova lutheri, Isochrysis galbana and Tetraselmis suecica) were grown on culture medium fortified with the nano-Fe compounds for 23 days and subsequent alterations in their growth rate, size distribution, lipid profiles and cellular ultrastructure were assessed. The added nano Fe concentrations were either equimolar with the EDTA-Fe conventionally added to the generic f/2 medium (i.e. 1.17 × 10(-5)M), or factor 10 lower and higher, respectively. We provide evidence for the: (1) broad size distribution of nZVI particles when added to the nutrient rich f/2 media with the higher relative percentage of the smallest particles with the coated forms; (2) normal algal growth in the presence of all three types of nZVIs with standard growth rates, cellular morphology and lipid content comparable or improved when compared to algae grown on f/2 with EDTA-Fe; (3) sustained algal growth and normal physiology at nZVI levels 10 fold below that in f/2, indicating preference to nanoparticles over EDTA-Fe; (4) increased total cellular lipid content in T. suecica grown on media enriched with uncoated nZVI25, and in P. lutheri with inorganically coated nZVI(powder), when compared at equimolar exposures; (5) significant change in fatty acid composition complementing the nZVI(powder)-mediated increase in lipid content of P. lutheri; (6) a putative NP uptake mechanism is proposed for I. galbana via secretion of an extracellular matrix that binds nZVIs which then become bioavailable via phagocytotic membrane processes.