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To date, research on the toxicity and potential environmental impacts of nanomaterials has predominantly focused on relatively simple and single-component materials, whilst more complex nanomaterials are currently entering commercial stages. The current study aimed to assess the long-term and size-dependent (60 and 500 nm) toxicity of a novel core–shell nanostructure consisting of a SiC core and TiO2 shell (SiC/TiO2, 5, 25, and 50 mg L−1) to the common model organism Daphnia magna. These novel core–shell nanostructures can be categorized as advanced materials. Experiments were conducted under environmentally realistic feeding rations and in the presence of a range of concentrations of humic acid (0.5, 2, 5, and 10 mg L−1 TOC). The findings show that although effect concentrations of SiC/TiO2 were several orders of magnitude lower than the current reported environmental concentrations of more abundantly used nanomaterials, humic acid can exacerbate the toxicity of SiC/TiO2 by reducing aggregation and sedimentation rates. The EC50 values (mean ± standard error) based on nominal SiC/TiO2 concentrations for the 60 nm particles were 28.0 ± 11.5 mg L−1 (TOC 0.5 mg L−1), 21.1 ± 3.7 mg L−1 (TOC 2 mg L−1), 18.3 ± 5.4 mg L−1 (TOC 5 mg L−1), and 17.8 ± 2.4 mg L−1 (TOC 10 mg L−1). For the 500 nm particles, the EC50 values were 34.9 ± 16.5 mg L−1 (TOC 0.5 mg L−1), 24.8 ± 5.6 mg L−1 (TOC 2 mg L−1), 28.0 ± 10.0 mg L−1 (TOC 5 mg L−1), and 23.2 ± 4.1 mg L−1 (TOC 10 mg L−1). We argue that fate-driven phenomena are often neglected in effect assessments, whilst environmental factors such as the presence of humic acid may significantly influence the toxicity of nanomaterials. [ABSTRACT FROM AUTHOR]

The continuous release of nanoparticles and nanoplastics into the marine environment necessitates the examination of their combined effects in marine organisms. Natural Organic Matter (NOM) can significantly influence the behavior of nanomaterials in the marine environment. The present study explores the effects of algal Extracellular Polymeric Substances (EPS) in reducing the combined toxic effects of three different polystyrene nanoplastics (PSNPs)— aminated (NH2-PSNPs), carboxylated (COOH-PSNPs), and plain PSNPs — and P25 titanium dioxide nanoparticles (Nano-TiO2) towards the marine alga, Chlorella sp. Two doses (0.25 and 2.5 mg/L) of nano-TiO2 mixed with the PSNPs (1 mg/L) were employed. The COOH-PSNPs with 2.5 mg/L nano-TiO2 exhibited higher growth inhibition toward algal cells. Addition of algal EPS to the mixture of NMs decreased the negative effect significantly. The mean hydrodynamic diameter increased significantly from 666 to 797 nm and 1248 to 3589 nm at concentrations 0.25 and 2.5 mg/L, respectively when the mixtures of nano-TiO2 and COOH-PSNPs were incubated with the algal EPS. In comparison to the pristine NMs, the EPS-NMs were found to significantly reduce the superoxide and hydroxyl radical production. The results were further validated with the estimation of lipid peroxidation (LPO), esterase activity, photosynthetic efficiency, and membrane permeability in the cells. The major outcomes from this study highlight the role of algal EPS in significantly reducing the toxic impact of binary mixture of NMs in marine organisms. [ABSTRACT FROM AUTHOR]

We systematically investigated how the combinations of size, shape and the natural organic matter (NOM)-ecocorona of gold (Au) engineered nanoparticles (ENPs) influence the attachment of the particles to algae and physical toxicity to the cells. Spherical (10, 60 and 100 nm), urchin-shaped (60 nm), rod-shaped (10 × 45, 40 × 60 and 50 × 100 nm), and wire-shaped (75 × 500, 75 × 3000 and 75 × 6000 nm) citrate-coated and NOM-coated Au-ENPs were used. Among the spherical particles only the spherical 10 nm Au-ENPs caused membrane damage to algae. Only the rod-shaped 10 × 45 nm induced membrane damage among the rod-shaped Au-ENPs. Wire-shaped Au-ENPs caused no membrane damage to the algae. NOM ecocorona decreased the membrane damage effects of spherical 10 nm and rod-shaped 10 × 45 nm ENPs. The spherical Au-ENPs were mostly loosely attached to the cells compared to other shapes, whereas the wire-shaped Au-ENPs were mostly strongly attached compared to particles with other shapes. NOM ecocorona determined the strength of Au-ENPs attachment to the cell wall, leading to the formation of loose rather than strong attachment of Au-ENPs to the cells. After removal of the loosely and strongly attached Au-ENPs, some particles remained anchored to the surface of the algae. The highest concentration was detected for spherical 10 nm Au-ENPs followed by rod-shaped 10 × 45 nm Au-ENPs, while the lowest concentration was observed for the wire-shaped Au-ENPs. The combined effect of shape, size, and ecocorona controls the Au-ENPs attachment and physical toxicity to cells. [ABSTRACT FROM AUTHOR]

To study the effects of nanomaterials after inhalation, a large number ofin vitrolung models have been reported in literature. Although thein vitromodels contribute to the reduction of animal studies, insufficient data exists to determine the predictive value of thesein vitromodels for thein vivosituation. The aim of this study was to determine the correlation betweenin vitroandin vivodata by comparing the dose metrics of silver nanoparticles in anin vitrolung model of increasing complexity to our previously publishedin vivoinhalation study.In vivo, the previously published study showed that the alveolar dose expressed as particle surface area is the most suitable dose metric to describe the toxicity of silver nanoparticles after inhalation. The results of the present study show that particle surface area is a suitable dose metric to describe the effects of silver nanoparticles when using a simple monolayer of lung epithelial cells. The dose metric shifted from particle surface area to particle mass when adding an increasing number of macrophages. In addition, a co-culture of endothelial cells, epithelial cells and macrophages on a Transwell® insert correlated less well to thein vivoresults compared to the epithelial monolayer. We conclude that for studying the acute pulmonary toxicity of nanoparticles simplein vitromodels using an epithelial monolayer better predict thein vivoresponse compared to complex co-culture models. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (NPs) are used in more consumer products than any other nanomaterial and their release into the environment is unavoidable. Of primary concern is the wastewater stream in which most silver NPs are transformed to silver sulfide NPs (Ag2S-NPs) before being applied to agricultural soils within biosolids. While Ag2S-NPs are assumed to be biologically inert, nothing is known of their effects on terrestrial plants. The phytotoxicity of Ag and its accumulation was examined in short-term (24 h) and longer-term (2-week) solution culture experiments with cowpea (Vigna unguiculataL. Walp.) and wheat (Triticum aestivumL.) exposed to Ag2S-NPs (0–20 mg Ag L−1), metallic Ag-NPs (0–1.6 mg Ag L−1), or ionic Ag (AgNO3; 0–0.086 mg Ag L−1). Although not inducing any effects during 24-h exposure, Ag2S-NPs reduced growth by up to 52% over a 2-week period. This toxicity did not result from their dissolution and release of toxic Ag+in the rooting medium, with soluble Ag concentrations remaining below 0.001 mg Ag L−1. Rather, Ag accumulated as Ag2S in the root and shoot tissues when plants were exposed to Ag2S-NPs, consistent with their direct uptake. Importantly, this differed from the form of Ag present in tissues of plants exposed to AgNO3. For the first time, our findings have shown that Ag2S-NPs exert toxic effects through their direct accumulation in terrestrial plant tissues. These findings need to be considered to ensure high yield of food crops, and to avoid increasing Ag in the food chain. [ABSTRACT FROM PUBLISHER]

To disentangle the contribution of ionic and nanoparticulate Ag to the overall toxicity to the earthwormEisenia fetida, a semi-permeable membrane strategy was used to separate Ag+released from silver nanoparticles (AgNPs) in an aqueous exposure. Internal Ag fractionation, activities of antioxidant enzymes and metabolites inE. fetidawere determined after 96 h of exposure to two sizes of polyvinylpyrrolidone-coated AgNPs. The response of the antioxidant system combined with the content of malondialdehyde indicated that the Ag+released from AgNPs induced significant oxidative stress to the earthworms. Ag accumulated from AgNPs was predominantly associated with the granules and cell membrane compartments, whereas dissolved Ag was localized in the cytosol-containing fraction. In both Ag+exposures, two intermediates in the Krebs cycle, succinate and fumarate, were significantly elevated and depleted, respectively. A similar alteration pattern was seen in groups exposed to both smaller AgNPs (S AgNP, 10 nm) and larger AgNP (L AgNP, 40 nm), indicating that these effects inE. fetidawere induced by exposure to released Ag+. In addition, unique metabolic responses including decreased malate and glucose levels in S AgNP-exposed earthworms could be associated with exposure to nanoparticulate silver. Increased leucine and arginine and decreased ATP and inosine levels were observed in L AgNP exposures only, which clearly demonstrated a size-specific effect of AgNPs. Collectively, this study provided strong evidence that nanosilver acts by a different mechanism than ionic silver to cause acute toxicity toE. fetida, but further verification under different environmental conditions is needed. [ABSTRACT FROM PUBLISHER]

The four copper nanoparticles (CuNPs) with the size of 25, 50, 78 and 100 nm and one type of micron-sized particles (MPs) (∼500 nm) were exposed to two mammalian (H4IIE and HepG2) and two piscine (PLHC-1 and RTH-149) cell lines to test the species-specific toxicities of CuNPs. The results showed that the morphologies, ion release and size of the particles all played an important role when investigating the toxicity. Furthermore, the authors found that the particle forms of CuNPs in suspensions highly contribute to the toxicity in all exposed cell lines whereas copper ions (Cu2+) only caused significant responses in mammalian cell lines, indicating the species-specific toxicity of CuNPs. This study revealed that the morphologies, ion release rate of NPs as well as the species-specific vulnerabilities of cells should all be considered when explaining and extrapolating toxicity test results among particles and among species. [ABSTRACT FROM AUTHOR]