Phytotoxicity and biotransformation of La2O3 nanoparticles in a terrestrial plant cucumber (Cucumis sativus)

Abstract

With the increasing applications of metal-based nanoparticles in various commercial products, it is necessary to address their environmental fate and potential toxicity. In this work, we assessed the phytotoxicity of lanthanum oxide (La₂O₃) NPs to cucumber plants and determined its distribution and biotransformation in roots by TEM and EDS, as well as STXM and NEXAFS. LaCl₃ was also studied as a reference toxicant. La₂O₃ NPs and LaCl₃ were both transformed to needle-like LaPO₄ nanoclusters in the intercellular regions of the cucumber roots. In vitro experiments demonstrated that the dissolution of La₂O₃ NPs was significantly enhanced by acetic acid. Accordingly, we proposed that the dissolution of NPs at the root surface induced by the organic acids extruded from root cells played an important role in the phytotoxicity of La₂O₃ NPs. The reactions of active NPs at the nano-bio interface should be taken into account when studying the toxicity of dissolvable metal-based nanoparticles.     

CeO2 nanoparticles alter the outcome of species interactions

Despite considerable research on the environmental impacts of nanomaterials, we know little about how they influence interactions between species. Here, we investigated the acute (12 d) and chronic (64 d) toxicities of cerium oxide nanoparticles (CeO₂ NPs) and bulk particles (0–200?mg/L) to three ciliated protist species (Loxocephalus sp., Paramecium aurelia, and Tetrahymena pyriformis) in single-, bi-, and multispecies microcosms. The results show that CeO₂ NPs strongly affected the interactions between ciliated protozoan species. When exposed to the highest CeO₂ NPs (200?mg/L), the intrinsic growth rates of Loxocephalus and Paramecium were significantly decreased by 18.87% and 88.27%, respectively, while their carrying capacities declined by more than 90%. However, CeO₂ NP exposure made it difficult to predict outcomes of interspecific competition between species. At higher NP exposure (100 and 200?mg/L), competition led to the extinction of both species in the Loxocephalus and Paramecium microcosms that survived in the absence of competitors or CeO₂ NPs. Further, the presence of potential competitors improved the survival of Loxocephalus to hundreds of individuals per milliliter in microcosms with Tetrahymena where Loxocephalus would otherwise not be able to tolerate high levels of NP exposure. This result could be attributed to weakened NP adsorption on the cell surface due to competitor-caused reduction of NP surface charge (from ?18.52 to ?25.17?mV) and intensified NP aggregation via phagocytosis of NPs by ciliate cells. Our results emphasize the need to explicitly consider species interactions for a more comprehensive understanding of the ecological consequences of NP exposure.     

Toxicity of CeO2 nanoparticles on a freshwater experimental trophic chain: A study in environmentally relevant conditions through the use of mesocosms

The toxicity of CeO₂ NPs on an experimental freshwater ecosystem was studied in mesocosm, with a focus being placed on the higher trophic level, i.e. the carnivorous amphibian species Pleurodeles waltl. The system comprised species at three trophic levels: (i) bacteria, fungi and diatoms, (ii) Chironomus riparius larvae as primary consumers and (iii) Pleurodeles larvae as secondary consumers. NP contamination consisted of repeated additions of CeO₂ NPs over 4 weeks, to obtain a final concentration of 1?mg/L. NPs were found to settle and accumulate in the sediment. No effects were observed on litter decomposition or associated fungal biomass. Changes in bacterial communities were observed from the third week of NP contamination. Morphological changes in CeO₂ NPs were observed at the end of the experiment. No toxicity was recorded in chironomids, despite substantial NP accumulation (265.8?±?14.1?mg Ce/kg). Mortality (35.3?±?6.8%) and a mean Ce concentration of 13.5?±?3.9?mg/kg were reported for Pleurodeles. Parallel experiments were performed on Pleurodeles to determine toxicity pathways: no toxicity was observed by direct or dietary exposures, although Ce concentrations almost reached 100?mg/kg. In view of these results, various toxicity mechanisms are proposed and discussed. The toxicity observed on Pleurodeles in mesocosm may be indirect, due to microorganism’s interaction with CeO₂ NPs, or NP dissolution could have occurred in mesocosm due to the structural complexity of the biological environment, resulting in toxicity to Pleurodeles. This study strongly supports the importance of ecotoxicological assessment of NPs under environmentally relevant conditions, using complex biological systems.     

Dissolution and bandgap paradigms for predicting the toxicity of metal oxide nanoparticles in the marine environment: an in vivo study with oyster embryos

Dissolution and bandgap paradigms have been proposed for predicting the ability of metal oxide nanoparticles (NPs) to induce oxidative stress in different in vitro and in vivo models. Here, we addressed the effectiveness of these paradigms in vivo and under conditions typical of the marine environment, a final sink for many NPs released through aquatic systems. We used ZnO and MnO₂ NPs as models for dissolution and bandgap paradigms, respectively, and CeO₂ NPs to assess reactive oxygen radical (ROS) production via Fenton-like reactions in vivo. Oyster embryos were exposed to 0.5–500?μM of each test NP over 24?h and oxidative stress was determined as a primary toxicity pathway across successive levels of biological complexity, with arrested development as the main pathological outcome. NPs were actively ingested by oyster larvae and entered cells. Dissolution was a viable paradigm for predicting the toxicity of NPs in the marine environment, whereas the surface reactivity based paradigms (i.e. bandgap and ROS generation via Fenton-like reaction) were not supported under seawater conditions. Bio-imaging identified potential cellular storage-disposal sites of solid particles that could ameliorate the toxicological behavior of non-dissolving NPs, whilst abiotic screening of surface reactivity suggested that the adsorption-complexation of surface active sites by seawater ions could provide a valuable hypothesis to explain the quenching of the intrinsic oxidation potential of MnO₂ NPs in seawater.     

Cerium oxide nanoparticles induce oxidative stress in the sediment-dwelling amphipod Corophium volutator

Cerium oxide nanoparticles (CeO₂ NPs) exhibit fast valence exchange between Ce(IV) and Ce(III) associated with oxygen storage and both pro and antioxidant activities have been reported in laboratory models. The reactivity of CeO₂ NPs once they are released into the aquatic environment is virtually unknown, but this is important to determine for assessing their environmental risk. Here, we show that amphipods (Corophium volutator) grown in marine sediments containing CeO₂ NPs showed a significant increase in oxidative damage compared to those grown in sediments without NPs and those containing large-sized (bulk) CeO₂ particles. There was no exposure effect on survival, but significant increases in single-strand DNA breaks, lipid peroxidation and superoxide dismutase activity were observed after a 10-day exposure to 12.5?mg?L^?1 CeO₂. Characterisation of the CeO₂ NPs dispersed in deionised or saline exposure waters revealed that more radicals were produced by CeO₂ NPs compared with bulk CeO₂. Electron energy loss spectroscopy (EELS) analysis revealed that both CeO₂ NPs were predominantly Ce(III) in saline waters compared to deionised waters where they were predominantly Ce(IV). In both types of medium, the bulk CeO₂ consisted mainly of Ce(IV). These results support a model whereby redox cycling of CeO₂ NPs between Ce(III) and Ce(IV) is enhanced in saline waters, leading to sublethal oxidative damage to tissues in our test organism.     

Phytotoxicity and biotransformation of La₂O₃ nanoparticles in a terrestrial plant cucumber (Cucumis sativus)

With the increasing applications of metal-based nanoparticles in various commercial products, it is necessary to address their environmental fate and potential toxicity. In this work, we assessed the phytotoxicity of lanthanum oxide (La?O?) NPs to cucumber plants and determined its distribution and biotransformation in roots by TEM and EDS, as well as STXM and NEXAFS. LaCl? was also studied as a reference toxicant. La?O? NPs and LaCl? were both transformed to needle-like LaPO? nanoclusters in the intercellular regions of the cucumber roots. In vitro experiments demonstrated that the dissolution of La?O? NPs was significantly enhanced by acetic acid. Accordingly, we proposed that the dissolution of NPs at the root surface induced by the organic acids extruded from root cells played an important role in the phytotoxicity of La?O? NPs. The reactions of active NPs at the nano-bio interface should be taken into account when studying the toxicity of dissolvable metal-based nanoparticles.     

The effect of zirconium doping of cerium dioxide nanoparticles on pulmonary and cardiovascular toxicity and biodistribution in mice after inhalation

Development and manufacture of nanomaterials is growing at an exponential rate, despite an incomplete understanding of how their physicochemical characteristics affect their potential toxicity. Redox activity has been suggested to be an important physicochemical property of nanomaterials to predict their biological activity. This study assessed the influence of redox activity by modification of cerium dioxide nanoparticles (CeO₂ NPs) via zirconium (Zr) doping on the biodistribution, pulmonary and cardiovascular effects in mice following inhalation. Healthy mice (C57BL/6?J), mice prone to cardiovascular disease (ApoE^?/?, western-diet fed) and a mouse model of neurological disease (5?×?FAD) were exposed via nose-only inhalation to CeO₂ NPs with varying amounts of Zr-doping (0%, 27% or 78% Zr), or clean air, over a four-week period (4?mg/m³ for 3?h/day, 5?days/week). Effects were assessed four weeks post-exposure. In all three mouse models CeO₂ NP exposure had no major toxicological effects apart from some modest inflammatory histopathology in the lung, which was not related to the amount of Zr-doping. In ApoE^?/? mice CeO₂ did not change the size of atherosclerotic plaques, but there was a trend towards increased inflammatory cell content in relation to the Zr content of the CeO₂ NPs. These findings show that subacute inhalation of CeO₂ NPs causes minimal pulmonary and cardiovascular effect four weeks post-exposure and that Zr-doping of CeO₂ NPs has limited effect on these responses. Further studies with nanomaterials with a higher inherent toxicity or a broader range of redox activities are needed to fully assess the influence of redox activity on the toxicity of nanomaterials.     

Close association of intestinal autofluorescence with the formation of severe oxidative damage in intestine of nematodes chronically exposed to Al(2)O(3)-nanoparticle

In nematodes, acute exposure (24-h) to 8.1–30.6 mg/L Al₂O₃-nanoparticles (NPs) or Al₂O₃ did not influence intestinal autofluorescence, whereas chronic exposure (10-d) to Al₂O₃-NPs at concentrations of 8.1–30.6 mg/L or Al₂O₃ at concentrations of 23.1–30.6 mg/L induced significant increases of intestinal lipofuscin accumulation, and formation of severe stress response and oxidative damage in intestines. Moreover, significant differences of intestinal autofluorescence, stress response and oxidative damage in intestines of Al₂O₃-NPs exposed nematodes from those in Al₂O₃ exposed nematodes were detected at examined concentrations. Oxidative damage in intestine was significantly correlated with intestinal autofluorescence in exposed nematodes, and oxidative damage in intestine was more closely associated with intestinal autofluorescence in nematodes exposed to Al₂O₃-NPs than exposed to Al₂O₃. Thus, chronic exposure to Al₂O₃-NPs may cause adverse effects on intestinal lipofuscin accumulation by inducing the formation of more severe oxidative stress in intestines than exposure to Al₂O₃ in nematodes.     

Oral intake of added titanium dioxide and its nanofraction from food products,food supplements and toothpaste by the Dutch population

Titanium dioxide (TiO₂) is commonly applied to enhance the white colour and brightness of food products. TiO₂ is also used as white pigment in other products such as toothpaste. A small fraction of the pigment is known to be present as nanoparticles (NPs). Recent studies with TiO₂ NPs indicate that these particles can have toxic effects. In this paper, we aimed to estimate the oral intake of TiO₂ and its NPs from food, food supplements and toothpaste in the Dutch population aged 2 to over 70 years by combining data on food consumption and supplement intake with concentrations of Ti and TiO₂ NPs in food products and supplements. For children aged 2–6 years, additional intake via ingestion of toothpaste was estimated. The mean long-term intake to TiO₂ ranges from 0.06?mg/kg bw/day in elderly (70+), 0.17?mg/kg bw/day for 7–69-year-old people, to 0.67?mg/kg bw/day in children (2–6 year old). The estimated mean intake of TiO₂ NPs ranges from 0.19?μg/kg bw/day in elderly, 0.55?μg/kg bw/day for 7–69-year-old people, to 2.16?μg/kg bw/day in young children. Ninety-fifth percentile (P95) values are 0.74, 1.61 and 4.16?μg/kg bw/day, respectively. The products contributing most to the TiO₂ intake are toothpaste (in young children only), candy, coffee creamer, fine bakery wares and sauces. In a separate publication, the results are used to evaluate whether the presence of TiO₂ NPs in these products can pose a human health risk.     

Physiological effects of magnetite (Fe3O4) nanoparticles on perennial ryegrass (Lolium perenne L.) and pumpkin (Cucurbita mixta) plants

Abstract

To date, knowledge gaps and associated uncertainties remain unaddressed on the effects of nanoparticles (NPs) on plants. This study was focused on revealing some of the physiological effects of magnetite (Fe₃O₄) NPs on perennial ryegrass (Lolium perenne L.) and pumpkin (Cucurbita mixta cv. white cushaw) plants under hydroponic conditions. This study for the first time reports that Fe₃O₄ NPs often induced more oxidative stress than Fe₃O₄ bulk particles in the ryegrass and pumpkin roots and shoots as indicated by significantly increased: (i) superoxide dismutase and catalase enzyme activities, and (ii) lipid peroxidation. However, tested Fe₃O₄ NPs appear unable to be translocated in the ryegrass and pumpkin plants. This was supported by the following data: (i) No magnetization was detected in the shoots of either plant treated with 30, 100 and 500 mg l^?1 Fe₃O₄ NPs; (ii) Fe K-edge X-ray absorption spectroscopic study confirmed that the coordination environment of Fe in these plant shoots was similar to that of Fe-citrate complexes, but not to that of Fe₃O₄ NPs; and (iii) total Fe content in the ryegrass and pumpkin shoots treated with Fe₃O₄ NPs was not significantly increased compared to that in the control shoots.     

Amplification of arsenic genotoxicity by TiO2 nanoparticles in mammalian cells: new insights from physicochemical interactions and mitochondria

Titanium dioxide nanoparticles (TiO₂ NPs) have shown great adsorption capacity for arsenic (As); however, the potential impact of TiO₂ NPs on the behavior and toxic responses of As remains largely unexplored. In the present study, we focused on the physicochemical interaction between TiO₂ NPs and As(III) to clarify the underlying mechanisms involved in their synergistic genotoxic effect on mammalian cells. Our data showed that As(III) mainly interacted with TiO₂ NPs by competitively occupying the sites of hydroxyl groups on the surface of TiO₂ NP aggregates, resulting in more aggregation of TiO₂ NPs. Although TiO₂ NPs at concentrations used here had no cytotoxic or genotoxic effects on cells, they efficiently increased the genotoxicity of As(III) in human-hamster hybrid (A_L) cells. The synergistic genotoxicity of TiO₂ NPs and As(III) was partially inhibited by various endocytosis pathway inhibitors while it was completely blocked by an As(III)-specific chelator. Using a mitochondrial membrane potential fluorescence probe, a reactive oxygen species (ROS) probe together with mitochondrial DNA-depleted ρ⁰ A_L cells, we discovered that mitochondria were essential for mediating the synergistic DNA-damaging effects of TiO₂ NPs and As(III). These data provide novel mechanistic proof that TiO₂ NPs enhanced the genotoxicity of As(III) via physicochemical interactions, which were mediated by mitochondria-dependent ROS.     

Impact of non-functionalized and amino-functionalized multiwall carbon nanotubes on pesticide uptake by lettuce (Lactuca sativa L.)

Abstract

The effect of non-functionalized and amino-functionalized multiwall carbon nanotube (CNT) exposure, as well as the impact of CNT presence on coexistent pesticide accumulation, was investigated in lettuce (Lactuca sativa L.). Lettuce seeds were sown directly into CNT-amended vermiculite (1000?mg?L^?1) to monitor phytotoxicity during germination and growth. During growth, lettuce seedlings were subsequently exposed to chlordane (cis-chlordane [CS], trans-chlordane [TC] and trans-nonachlor [TN]) and p,p′-DDE (all at 100?ng/L) in the irrigation solution for a 19-d growth period. CNT exposure did not significantly influence seed germination (82–96%) or plant growth. Similarly, pesticide exposure had no impact on plant growth, total pigment production or tissue lipid peroxidation. After 19?d, the root content of total chlordane and p,p′-DDE was 390 and 73.8?µg?g^?1, respectively; in plants not exposed to CNTs, the shoot levels were 1.58 and 0.40?µg?g^?1, respectively. The presence and type of CNT significantly influenced pesticide availability to lettuce seedlings. Non-functionalized CNT decreased the root and shoot pesticide content by 88% and 78%, respectively, but amino-functionalized CNT effects were significantly more modest, with decreases of 57% in the roots and 23% in the shoots, respectively. The presence of humic acid completely reversed the reduced accumulation of pesticides induced by amino-functionalized CNT, likely due to strong competition over adsorption sites on the nanomaterial (NM). These findings have implications for food safety and for the use of engineered NMs in agriculture, especially with leafy vegetables.     

FTIR microscopy reveals distinct biomolecular profile of crustacean digestive glands upon subtoxic exposure to ZnO nanoparticles

Biomolecular profiling with Fourier-Transform InfraRed Microscopy was performed to distinguish the Zn²⁺-mediated effects on the crustacean (Porcellio scaber) digestive glands from the ones elicited by the ZnO nanoparticles (NPs). The exposure to ZnO NPs or ZnCl₂ (1500 and 4000?µg Zn/g of dry food) activated different types of metabolic pathways: some were found in the case of both substances, some only in the case of ZnCl₂, and some only upon exposure to ZnO NPs. Both the ZnO NPs and the ZnCl₂ increased the protein (～1312?cm^?1; 1720–1485?cm^?1/3000–2830?cm^?1) and RNA concentration (～1115?cm^?1). At the highest exposure concentration of ZnCl₂, where the effects occurred also at the organismal level, some additional changes were found that were not detected upon the ZnO NP exposure. These included changed carbohydrate (most likely glycogen) concentrations (～1043?cm^?1) and the desaturation of cell membrane lipids (～3014?cm^?1). The activation of novel metabolic pathways, as evidenced by changed proteins’ structure (at 1274?cm^?1), was found only in the case of ZnO NPs. This proves that Zn²⁺ are not the only inducers of the response to ZnO NPs. Low bioavailable fraction of Zn²⁺ in the digestive glands exposed to ZnO NPs further supports the role of particles in the ZnO NP-generated effects. This study provides the evidence that ZnO NPs induce their own metabolic responses in the subtoxic range.     

The effect of papaverine on local tissue P O 2 and microflow in cat brain cortex

Summary The effect of intracarotid and intravenous administration of papaverine on local tissue P _{O 2} and microflow in the cat's brain surface was studied. Local tissue P _{O 2} was measured with a multiwire surface electrode polaroraphically, and microflow by local hydrogen clearance method.The intracarotid infusions were made for 1, 2 and 5 min with doses of 0.1, 0.2 and 0.5 mg/kg/min papaverine, and the intravenous ones for 5 min with doses of 0.2, 0.5 and 1 mg/kg/min.The continuous intracarotid infusions showed that papaverine in the doses used distinctly increased local tissues P _{O 2} and microcirculation of the brain surface. With the doses applied, systemic arterial pressure (SAP) changed little. It slightly decreased only during the 5 min infusions containing 0.5 mg/kg/min. The duration of the effect increased with increases in the duration of the infusion and of the dose. The maximum duration was observed with 5 min infusions and lasted for 10–15 min after drug administration was discontinued. During the i.v. infusions, tissue P _{O 2} and microflow rose less than with intracarotid ones. No redistribution of capillary flow was observed.     

Antioxidant ameliorating effects against H2O2-induced cytotoxicity in primary endometrial cells

Oxidative stress and a disrupted antioxidant system are involved in a variety of pregnancy complications. In the present study, the role of vitamin E (Vit E) and folate as radical scavengers on the GSH homeostasis in stress oxidative induced in rat endometrial cells was investigated. Primary endometrial stromal cell cultures treated with 50 and 200?µM of H₂O₂ and evaluated the cytoprotective effects of Vit E (5?µM) and folate (0.01?µM) in H₂O₂-treated cells for 24?h. Following the exposure of endometrial cells to H₂O₂ alone and in the presence of Vit E and/or folate, cell survival, glutathione peroxidase (GPx) and glutathione reductase activities and the level of reduced glutathione (GSH) were measured. Cell adhesions comprise of cell attachment and spreading on collagen were determined. Flow cytometric analysis using annexin V was used to measure apoptosis. H₂O₂ treatment showed a marked decrease in cell viability, GPx and GR activities and the level of GSH. Although Vit E or folate had some protective effect, combination therapy with Vit E and folate attenuated all the changes due to H₂O₂ toxicity. An increasing number of alive cells was showed in the cells exposed to H₂O₂ (50?µM) accompanied by co-treatment with Vit E and folic acid. The present findings indicate that co-administration of Vit E and folate before and during pregnancy may maintain a viable pregnancy and contribute to its clinical efficacy for the treatment of some idiopathic infertility.     

The effect and fate of water-soluble carbon nanodots in maize (Zea mays L.)

In this study, the toxicity of water-soluble carbon nanodots (C-dots) to maize (Zea mays L.) and their uptake and transport in plants were investigated. After exposed in sand matrix amended with 0–2000?mg/L C-dots for 4 weeks, we found that the phytotoxicity of C-dots was concentration-dependent. C-dots at 250 and 500?mg/L showed no toxicity to maize. However, 1000 and 2000?mg/L C-dots significantly reduced the fresh weight of root by 57% and 68%, and decreased the shoot fresh weight by 38% and 72%, respectively. Moreover, in maize roots, the exposure of C-dots at 2000?mg/L significantly increased the H₂O₂ content and lipid peroxidation (6.5 and 1.65 times higher, respectively), as well as, the antioxidant enzymes activities, up to 2, 1.5, 1.9 and 1.9 times higher for catalase, ascorbate peroxidase, guaiacol peroxidase and superoxide dismutase, respectively. On the other hand, C-dots were observed in detached root-cap cells, cortex and vascular bundle of roots and mesophyll cells of leaves through fluorescence microscopy analysis, suggesting that C-dots were absorbed and translocated systemically in maize. Remarkably, a certain amount of C-dots were excreted out from leaf blade. To our knowledge, this is the first study combined phenotypic observation with physiologic responses and bioaccumulation and translocation analysis of C-dots to investigate their effect and fate in maize.     

In vivo toxicological evaluation of polymer brush engineered nanoceria: impact of brush charge

Nanoceria has a broad variety of industrial and pharmacological applications due to its antioxidant activity. Nanoceria can be modified by surface coating with polyelectrolyte brushes. Brushes can increase the surface charge of nanoceria, providing greater aqueous stability while reducing agglomeration. However, surface-coating also behaves as a barrier around nanoceria, affecting its redox equilibrium and, hence, its biological and toxicological properties. In the present study, we examined whether bare nanoceria (CeO₂; 80–150?nm) and nanoceria modified by surface polymer brush, using negatively charged polyacrylic acid (CeO₂@PAA) and positively charged poly (2-(methacryloyloxy)ethyl-trimethyl-ammonium chloride (CeO₂@PMETAC), could induce systemic toxicity. As CeO₂ has limited colloidal stability, which might result in vascular occlusion, intraperitoneal injection was used instead of intravenous administration. C57Bl/6 mice were four times injected with three different doses of each nanoceria-based sample (corresponding to 1.8, 5.3 and 16?mg Ce/kg BW/administration) for a total period of 14?days. CeO₂@PMETAC induced a significant dose-dependent neutrophilia. Histopathological evaluation showed inflammatory processes in the capsule of liver, kidney, and spleen of animals at all doses of CeO₂@PMETAC, and with the highest dose of CeO₂@PAA and CeO₂. However, none of the nanoceria-based samples tested increased the level of DNA damage or micronuclei in blood cells, even though Ce was detected by inductively coupled plasma mass spectrometry analyses in the bone marrow. Only CeO₂@PMETAC induced the presence of megakaryocytes in the spleen. A higher accumulation of Ce in mononuclear phagocyte system organs (liver, spleen and bone marrow) was observed after CeO₂@PMETAC treatment compared with CeO₂@PAA and CeO₂.     

Tissue distribution following 28 day repeated oral administration of aluminum‐based nanoparticles with different properties and the in vitro toxicity

The tissue distribution and toxicity of nanoparticles (NPs) depend on their physical and chemical properties both in the manufactured condition and within the biological system. We characterized three types of commercially available aluminum‐based NPs (Al‐NPs), two rod‐type aluminum oxide NPs (Al₂O₃, AlONPs), with different aspect ratios (short [S]‐ and long [L]‐AlONPs), and spherical aluminum cerium oxide NPs (AlCeO₃, AlCeONPs). The surface area was in order of the S‐AlONPs > L‐AlONPs > AlCeONPs. Very importantly, we found that AlCeONPs is Al₂O₃‐coated CeO₂ NPs, but not AlCeO₃ NPs, and that the Al level in AlCeONPs is approximately 20% of those in S‐ and L‐AlONPs. All three types of Al‐NPs were slightly ionized in gastric fluid and rapidly particlized in the intestinal fluid. There were no significant differences in the body weight gain following 28 days of repeated oral administration of the three different types of Al‐NPs. All Al‐NPs elevated Al level in the heart, spleen, kidney and blood at 24 hours after the final dose, accompanied by the altered tissue level of redox reaction‐related trace elements. Subsequently, in four types of cells derived from the organs which Al‐NPs are accumulated, H9C2 (heart), HEK‐293 (kidney), splenocytes and RAW264.7 (blood), S‐AlONPs showed a very low uptake level and did not exert significant cytotoxicity. Meanwhile, cytotoxicity and uptake level were the most remarkable in cells treated with AlCeONPs. In conclusion, we suggest that the physicochemical properties of NPs should be examined in detail before the release into the market to prevent unexpected adverse health effects.     

Assessment of impact of α‐Fe2O3 and γ‐Fe2O3 nanoparticles on phytoplankton species Selenastrum capricornutum and Nannochloropsis oculata

In this study, the impact of alpha‐iron oxide (α‐Fe₂O₃, 20‐40 nm) and gamma iron oxide (γ‐Fe₂O₃, 20‐40 nm) nanoparticles (NPs) on phytoplankton species Selenastrum capricornutum and Nannochloropsis oculata was investigated Characterizations of the NPs were systematically carried out by TEM, dynamic light scattering, zeta potential, X‐ray diffraction, SEM, and Fourier transformation infrared spectroscopy. Acute toxicity was tested between 0.2 and 50 mg/L for each NP for a period of 72 hours exposure. γ‐Fe₂O₃ NP inhibited development of N oculata at the rate of 54% in 0.2 mg/L group with a high mortality rate of up to 82%. α‐Fe₂O₃ NPs were less toxic that induced 97% mortality on N oculata at 10 mg/L suspensions. In contrast, α‐Fe₂O₃ NP inhibited growth of S capricornutum strongly (73%) in 0.2 mg/L group. γ‐Fe₂O₃ NPs showed similar growth inhibition (72%) on S capricornutum in 10 mg/L suspensions. Despite the differential effects, the results indicated acute toxicity of α‐Fe₂O₃ and γ‐Fe₂O₃ NPs on N oculata and S capricornutum.