CuO Nanoparticles Exposure Research Articles

Integrative chemical, physiological, and metabolomics analyses reveal nanospecific phytotoxicity of metal nanoparticles

The increasing application of metal nanoparticles (NPs) via agrochemicals and sewage sludge results in non-negligible phytotoxicological risks. Herein, the potential phytotoxicity of ZnO and CuO NPs on wheat was determined using integrative chemical, physiological, and metabolomics analyses, in comparison to Zn2+ and Cu2+. It was found that ZnO or CuO NPs had a stronger inhibitory effect on wheat growth than Zn2+ or Cu2+. After exposure to ZnO or CuO NPs, wheat seedlings accumulated significantly higher levels of Zn or Cu than the corresponding Zn2+ or Cu2+ treatments, indicating the active uptake of NPs via wheat root. TEM analysis further confirmed the intake of NPs. Moreover, ZnO or CuO NPs exposure altered micronutrients (Fe, Mn, Cu, and Zn) accumulation in the tissues and decreased the activities of antioxidant enzymes. The metabolomics analysis identified 312, 357, 145, and 188 significantly changed metabolites (SCMs) in wheat root exposed to ZnO NPs, CuO NPs, Zn2+, and Cu2+, respectively. Most SCMs were nano-specific to ZnO (80%) and CuO NPs (58%), suggesting greater metabolic reprogramming by NPs than metal ions. Overall, nanospecific toxicity dominated the phytotoxicity of ZnO and CuO NPs, and our results provide a molecular perspective on the phytotoxicity of metal oxide NPs.

Metal Nanoparticles with Antimicrobial Properties: The Toxicity Response in Mouse Mesenchymal Stem Cells.

Some metal nanoparticles (NP) are characterized by antimicrobial properties with the potential to be used as alternative antibiotics. However, NP may negatively impact human organism, including mesenchymal stem cells (MSC), a cell population contributing to tissue growth and regeneration. To address these issues, we investigated the toxic effects of selected NP (Ag, ZnO, and CuO) in mouse MSC. MSC were treated with various doses of NP for 4 h, 24 h, and 48 h and multiple endpoints were analyzed. Reactive oxygen species were generated after 48 h CuO NP exposure. Lipid peroxidation was induced after 4 h and 24 h treatment, regardless of NP and/or tested dose. DNA fragmentation and oxidation induced by Ag NP showed dose responses for all the periods. For other NP, the effects were observed for shorter exposure times. The impact on the frequency of micronuclei was weak. All the tested NP increased the sensitivity of MSC to apoptosis. The cell cycle was most affected after 24 h, particularly for Ag NP treatment. In summary, the tested NP induced numerous adverse changes in MSC. These results should be taken into consideration when planning the use of NP in medical applications where MSC are involved.

Melatonin-mediated resistance to copper oxide nanoparticles-induced toxicity by regulating the photosynthetic apparatus, cellular damages and antioxidant defense system in maize seedlings

The pollution of nanoparticles (NPs) has linked with severe negative effects on crop productivity. Thus, effective strategies are needed to mitigate the phytotoxicity of NPs. The aim of present study was to evaluate the efficacy of exogenously applied melatonin (MT) in mitigating the toxic effects of copper oxide nanoparticles (CuO NPs) from maize seedlings. Therefore, we comprehensively investigated the inhibitory effects of MT against CuO NPs-induced toxicity on morpho-physiological, biochemical and ultrastructural levels in maize. Our results show that CuO NPs (300 mg L−1) exposure displayed significantly reduction in all plant growth traits and induced toxicity in maize. Furthermore, 50 μM MT provided maximum plant tolerance against CuO NPs-induced phytotoxicity. It was noticed that MT improved plant growth, biomass, photochemical efficiency (Fv/Fm), chlorophyll contents (Chl a and Chl b), SPAD values and gas exchange attributes (stomatal conductance, net photosynthetic rate, intercellular CO2 concentration and transpiration rate) under CuO NPs stress. In addition, MT enhanced the antioxidant defense system and conferred protection to ultrastructural (mainly chloroplast, thylakoids membrane and plastoglobuli) damages and stomatal closure in maize plants subjected to CuO NPs stress. Together, it can be stated that the exogenous supply of MT improves the resilience of maize plants against the CuO NPs-induced phytotoxicity. Our current findings can be useful for the enhancement of plant growth and yield attributes in CuO NPs-contaminated soils. The reported information can provide insight into the MT pathways that can be used to improve crop stress tolerance in a challenging environment.

Simultaneous exposure of wheat (Triticum aestivum L.) to CuO and S nanoparticles alleviates toxicity by reducing Cu accumulation and modulating antioxidant response

Widespread use of metal-based nanoparticles (NPs) may result in the increased accumulation of metals in agricultural soil, which could affect crop productivity and contaminate the food-chain. The effect of sulfur nanoparticles (S NPs, 200 mg/L) co-exposure on the toxicity of CuO nanoparticles (CuO NPs, 25 and 50 mg/L) to wheat seedlings was investigated in a hydroponic system. CuO NPs exposure significantly inhibited the growth of wheat seedlings, causing 43.6% and 54.1% decreases in the fresh biomass of plants and 82.8% and 83.1% decrease in the total chlorophyll contents at 25 and 50 mg/L (CuONP25 and CuONP50), respectively, as compared to controls. CuO NPs exposure at both concentrations increased the malondialdehyde (MDA) content in shoot and root tissues by 66.4–67.9% and 47.7–48.8%, respectively. Further, CuO NPs exposure elevated the activities POD, SOD, and CAT by 2.19–2.27, 5.82–6.09, and 1.44–1.95 times in roots, and by 45.2–67.8%, 86.7–154.5%, and 22.5–56.1% in shoot, respectively, in comparison to control. The addition of S NPs alone increased wheat biomass by 11.0% and total chlorophyll contents by 4.4%, compared to controls. Further, simultaneous exposure to S NPs (200 mg/L) and CuO NPs (25 or 50 mg/L) alleviated the CuO NPs toxicity; wheat biomass was 47.8% and 37.7% higher in CuONP25 + SNP and CuONP50 + SNP treatments, respectively, as compared to CuO NPs alone treated plants. Co-exposed plants showed reduced levels of total reactive oxygen species (ROS), O2·- and H2O2. Additionally, S NPs exposure reduced Cu uptake and accumulation in both root and shoot tissue by 32.2–54.4% and 38.3–57.5%, respectively. In summary, S NPs alleviated CuO NPs toxicity to wheat seedlings, most likely by reducing Cu bioavailability and accumulation of Cu in plant tissues, and also altered S nutrition and the modulation of antioxidant response in plants. These results showed that S NPs application has the potential to alleviate CuO NP toxicity and increase wheat productivity affected by metals toxicity.

Oxidative Stress in Far Eastern Mussel Mytilus trossulus (Gould, 1850) Exposed to Combined Polystyrene Microspheres (µPSs) and CuO-Nanoparticles (CuO-NPs)

The ingress of nanoparticles of metal oxides and microfragments of synthetic polymers (microplastics) into a marine environment causes unpredictable consequences. The effects of such particles cannot be predicted due to a lack of ecotoxicological information. In this research, a series of laboratory experiments were conducted on the combined effects of CuO-nanoparticles (CuO-NPs) and polystyrene microspheres (µPSs) on the development of oxidative stress processes in the marine filter-feeder mollusk Mytilus trossulus. Biomarkers of oxidative stress, including the lysosome membrane stability of hematocytes (LMS), the index of antioxidant activity (IAA), the levels of malonaldehyde (MDA) and protein carbonyls (PCs), and DNA damage in digestive gland cells, were measured after 5 days of exposure. Based on a battery of biochemical markers, it was shown that oxidative stress was induced at varying degrees in the experimental mollusks when exposed to CuO-NPs and µPSs both separately and in combination. In contrast, the single-treatment effect on the lysosomal membrane was enhanced by the combined CuO-NPs and µPSs (from 77.14 ± 8.56 to 42 ± 4.26 min). In addition, exposure to both the compounds alone and in combination decreased the IAA (from 22.87 ± 1.25, to 19.55 ± 0.21, 10.73 ± 0.53, and 12.06 ± 1.62 nM/mg protein, respectively). The PC level significantly increased only after CuO-NP exposure (from 0.496 ± 0.02 to 0.838 ± 0.03 μM/mg protein). Furthermore, the results showed that the investigated particles, both alone and in combination, promoted DNA damage in digestive gland cells (from 2.02 ± 0.52 to 5.15 ± 0.37, 18.29 ± 2.14, and 10.72 ± 2.53%, respectively), indicating that these compounds are genotoxic. Overall, the results obtained suggest that oxidative stress is the leading factor in the negative effects of CuO-NPs and µPSs. Considering the exceptional role of genome integrity in the functioning of biological systems, the revealed damages in the DNA molecule structure should be attributed to the most important manifestations of the toxicity of these two forms of marine pollution.

CuO, ZnO, and γ-Fe2O3 nanoparticles modified the underground biomass and rhizosphere microbial community of Salvia miltiorrhiza (Bge.) after 165-day exposure

To investigate whether metal oxide nanoparticles exhibit toxicity or positive effects on medicinal plants, CuO, ZnO, and γ-Fe2O3 nanoparticles (NPs), at concentrations of 100 and 700 mg kg−1, were introduced into the cultivation of Salvia miltiorrhiza (Bge.). Metal elemental contents, chemical constituents, biomass and the structure of the rhizosphere microbial community was used to estimate this effect. The results indicated CuO NPs increased the Cu content and ZnO NPs increased the Zn content significantly as exposure increased, γ-Fe2O3 NPs had no significant effect on Fe content in S. miltiorrhiza roots, while 100 mg kg−1 ZnO and CuO NPs significantly decreased the Fe content in roots. Additionally, ZnO and γ-Fe2O3 NPs increased the underground biomass, and diameter of S. miltiorrhiza roots. However, these three metal oxide nanoparticles had no significant effect on total tanshinones, while the 700 mg kg−1 γ-Fe2O3 NPs treatment increased salvianolic acid B content by 36.46%. High-throughput sequencing indicated at 700 mg kg−1 ZnO NPs, the relative abundance of Humicola (Zn superoxide dismutase producer), was notably increased by 97.46%, and that of Arenimonas, Thiobacillus and Methylobacillus (taxa related to heavy metal tolerance) was significantly increased by 297.14%, 220.26% and 107.00%. The 700 mg kg−1 CuO NPs exposure caused a significant increase in the relative abundances of Sphingomonas (a copper-resistant and N2-fixing genus) and Flavisolibacter (stripe rust biocontrol bacteria) by 127.32% and 118.33%. To our best knowledge, this is the first study to examine the potential impact of NPs on the growth and rhizosphere microorganisms of S. miltiorrhiza.

Copper Oxide Nanoparticle Diameter Mediates Serum‐Sensitive Toxicity in BEAS‐2B Cells

Copper oxide (CuO) nanoparticles (NPs) are abundant in manufacturing processes, but they are an airway irritant. In vitro pulmonary toxicity of CuO NPs has been modeled using cell lines such as human bronchial epithelial cell line BEAS‐2B. In 2D in vitro culture, BEAS‐2B undergoes squamous differentiation due to the presence of serum. Differentiation is part of the repair process of lung cells in vivo that helps to preserve the epithelial lining of the respiratory tract. Herein, the effects of serum on the hydrodynamic diameter, cellular viability, cellular differentiation, and cellular uptake of 5 and 35 nm CuO NPs are investigated, and the mean cell area is used as the differentiation marker for BEAS‐2B cells. The results demonstrate that the hydrodynamic diameter decreases with the addition of serum to the culture medium. Serum also increases the mean cell area, and only affects dose‐dependent cytotoxicity of 35 nm CuO NPs, while simultaneously having no effect on intracellular Cu2+. This study presents evidence that both NP size and the presence of serum in culture media influence the relative viability of BEAS‐2B cells following CuO NP exposure and highlights a critical need for carefully designed experiments and accurately reported conditions.

CuO Nanoparticle Exposure Impairs the Root Tip Cell Walls of Arabidopsis thaliana Seedlings

The increasing number of applications of nanoparticles (NPs) in various fields has led to negative effects on the environment. In this study, the effects of CuO nanoparticles (CuO NPs) on Arabidopsis root tips were investigated. Significant growth inhibition on Arabidopsis roots was observed after treatment with both CuO NPs (10 mg/L) and the correspondingly released Cu2+ (0.80 mg/L). Scanning electron microscope images demonstrated that NPs primarily deposited on the surface of root tips and penetrated intercellular spaces after CuO NP exposure. Light and fluorescence microscope visualization revealed that the root tips were damaged severely after CuO NP exposure, with swelling of the hair zone, splitting of the cell wall junction, and disordered cell arrangement in the root tip. Semiquantitative analysis by Fourier transform infrared spectroscopy demonstrated that the cell wall xyloglucan and esterified pectin contents in the roots were decreased. Similar but weaker effects on the roots were detected after Cu2+ treatment. Additionally, some genes related to cell wall organization were downregulated by CuO NP stress, partially contributing to the cell wall component change. The results demonstrated that CuO NPs produced phytotoxicity to the cell wall through both physical damage and biochemical disruption, causing loosening of the tethers between cellulose microfibrils in the cell wall and the disruption of cell adhesion. The phytotoxicity of CuO NPs in the plant cell wall was mainly caused by NPs and was partially related to the released Cu2+. These findings are helpful to understand better the negative effects of CuO NPs on plant regarding the cell wall.

Exposure of CuO nanoparticles and their metal counterpart leads to change in the gut microbiota and resistome of collembolans

The widespread use of copper oxide nanoparticles (CuONPs) has dramatically increased their concentrations in soils and severely affected the health of soil organisms. The gut microbiota critically contributes to the metabolism and immune system of its host and is sensitive to environmental pollution. The toxic effect of CuONPs on the gut microbiota, especially in soil fauna, still needs further research. In the present study, a comprehensive toxicological test was performed to reveal the effects of CuONPs and their metal counterpart on the gut microbiota of soil collembolans using Illumina high throughput sequencing. Furthermore, the concomitant changes in the collembolans gut-associated antibiotic resistance genes (ARGs) and metabolism were investigated using high-throughput quantitative PCR and carbon and nitrogen stable isotope compositions. Both CuONPs and ionic copper (Cu) exposure disturbed the collembolan gut microbial community structure while only CuONPs reduced the gut microbial diversity. A total of 66 ARGs were detected in the collembolan guts, and CuONPs exposure induced a reduction in both diversity and abundance of ARGs. Additionally, CuONPs and ionic Cu exposure altered the C and N stable isotope compositions of the collembolans, indicating a change in their metabolism. Moreover, structural equation modeling indicated that 85.5% of the carbon stable isotope variations and 73.3% of the nitrogen stable isotope variations were explained by changes in Cu bioaccumulation and the gut microbiota. The results of the present study extend our knowledge regarding the comprehensive toxicity of metal oxide NPs on soil fauna.

Exposure to CuO Nanoparticles Mediates NFκB Activation and Enhances Amyloid Precursor Protein Expression.

Amyloid precursor protein (APP) is directly related to Aβ amyloidosis—a hallmark of Alzheimer’s disease (AD). However, the impact of environmental factors upon APP biology and Aβ amyloid pathology have not been well studied. The increased use of nanoparticles (NPs) or engineered nanomaterials (ENMs) has led to a growing body of evidence suggesting that exposure to metal/metal oxide NPs, such as Fe2O3, CuO, and ZnO, may contribute to the pathophysiology of neurodegenerative diseases such as AD through neuroinflammation. Our previous studies indicated that exposure to CuO nanoparticles (CuONPs) induce potent in vitro neurotoxicity. Herein, we investigated the effects on APP expression in neuronal cells exposed to different metal oxide NPs. We found a low dose of CuONPs effectively activated the NFκB signaling pathway and increased APP expression. Moreover, the inhibition of p65 expression using siRNA abolished CuONP-mediated APP expression, suggesting that NFκB-regulated APP expression in response to CuONP exposure may be associated with AD pathology.

Exposure of CuO Nanoparticles Contributes to Cellular Apoptosis, Redox Stress, and Alzheimer's Aβ Amyloidosis.

Fe2O3, CuO and ZnO nanoparticles (NP) have found various industrial and biomedical applications. However, there are growing concerns among the general public and regulators about their potential environmental and health impacts as their physio-chemical interaction with biological systems and toxic responses of the latter are complex and not well understood. Herein we first reported that human SH-SY5Y and H4 cells and rat PC12 cell lines displayed concentration-dependent neurotoxic responses to insults of CuO nanoparticles (CuONP), but not to Fe2O3 nanoparticles (Fe2O3NP) or ZnO nanoparticles (ZnONP). This study provides evidence that CuONP induces neuronal cell apoptosis, discerns a likely p53-dependent apoptosis pathway and builds out the relationship between nanoparticles and Alzheimer’s disease (AD) through the involvement of reactive oxygen species (ROS) and increased Aβ levels in SH-SY5Y and H4 cells. Our results implicate that exposure to CuONP may be an environmental risk factor for AD. For public health concerns, regulation for environmental or occupational exposure of CuONP are thus warranted given AD has already become a pandemic.

A global metabolomic insight into the oxidative stress and membrane damage of copper oxide nanoparticles and microparticles on microalga Chlorella vulgaris

To compare aquatic organisms’ responses to the toxicity of copper oxide (CuO) nanoparticles (NPs) with those of CuO microparticles (MPs) and copper (Cu) ions, a global metabolomics approach was employed to investigate the changes of both polar and nonpolar metabolites in microalga Chlorella vulgaris after 5-day exposure to CuO NPs and MPs (1 and 10 mg/L), as well as the corresponding dissolved Cu ions (0.08 and 0.8 mg/L). Unchanged growth, slight reactive oxygen species production, and significant membrane damage (at 10 mg/L CuO particles) in C. vulgaris were demonstrated. A total of 75 differentiated metabolites were identified. Most metabolic pathways perturbed after CuO NPs exposure were shared by those after CuO MPs and Cu ions exposure, including accumulation of chlorophyll intermediates (max. 2.4–5.2 fold), membrane lipids remodeling for membrane protection (decrease of phosphatidylethanolamines (min. 0.6 fold) and phosphatidylcholines (min. 0.2–0.7 fold), as well as increase of phosphatidic acids (max. 1.5–2.9 fold), phosphatidylglycerols (max. 2.2–2.3 fold), monogalactosyldiacylglycerols (max. 1.2–1.4 fold), digalactosylmonoacylglycerols (max. 1.9–3.8 fold), diacylglycerols (max. 1.4 fold), lysophospholipids (max. 1.8–3.0 fold), and fatty acids (max. 3.0–6.2 fold)), perturbation of glutathione metabolism induced by oxidative stress, and accumulation of osmoregulants (max. 1.3–2.6 fold) to counteract osmotic stress. The only difference between metabolic responses to particles and those to ions was the accumulation of fatty acids oxidation products: particles caused higher fold changes (particles/ions ratio 1.9–3.0) at 1 mg/L and lower fold changes (particles/ions ratio 0.4–0.7) at 10 mg/L compared with ions. Compared with microparticles, there was no nanoparticle-specific pathway perturbed. These results confirm the predominant role of dissolved Cu ions on the toxicity of CuO NPs and MPs, and also reveal particle-specific toxicity from a metabolomics perspective.

ZnO and CuO nanoparticles: a threat to soil organisms, plants, and human health.

The progressive increase in nanoparticles (NPs) applications and their potential release into the environment because the majority of them end up in the soil without proper care have drawn considerable attention to the public health, which has become an increasingly important area of research. It is required to understand ecological threats of NPs before applications. Once NPs are released into the environment, they are subjected to translocation and go through several modifications, such as bio/geo-transformation which plays a significant role in determination of ultimate fate in the environment. The interaction between plants and NPs is an important aspect of the risk assessment. The plants growing in a contaminated medium may significantly pose a threat to human health via the food chain. Metal oxide NPs ZnO and CuO, the most important NPs, are highly toxic to a wide range of organisms. Exposure and effects of CuO and ZnO NPs on soil biota and human health are critically discussed in this study. The potential benefits and unintentional dangers of NPs to the environment and human health are essential to evaluate and expected to produce less toxic and more degradable NPs to minimize the environmental risk in the future.

Physiological and transcriptomic analyses reveal CuO nanoparticle inhibition of anabolic and catabolic activities of sulfate-reducing bacterium

The widespread use of CuO nanoparticles (NPs) results in their continuous release into the environment, which could pose risks to public health and to microbial ecosystems. Following consumption, NPs will initially enter into sewer systems and interact with and potentially influence sewer microbial communities. An understanding of the response of microbes in sewers, particularly sulfate-reducing bacteria (SRB), to the CuO NPs induced stress is important as hydrogen sulfide produced by SRB can cause sewer corrosion and odour emissions. In this study, we elucidated how the anabolic and catabolic processes of a model SRB, Desulfovibrio vulgaris Hidenborough (D. vulgaris), respond to CuO NPs. Physiological analyses indicated that the exposure of the culture to CuO NPs at elevated concentrations (>50 mg/L) inhibited both its anabolic and catabolic activities, as revealed by lowered cell proliferation and sulfate reduction rate. The antibacterial effects of CuO NPs were mainly attributed to the overproduction of reactive oxygen species. Transcriptomic analysis indicated that genes encoding for flagellar assembly and some genes involved in electron transfer and respiration were down-regulated, while genes for the ferric uptake regulator (Fur) were up-regulated. Moreover, the CuO NPs exposure significantly up-regulated genes involved in protein synthesis and ATP synthesis. These results suggest that CuO NPs inhibited energy conversion, cell mobility, and iron starvation to D. vulgaris. Meanwhile, D. vulgaris attempted to respond to the stress of CuO NPs by increasing protein and ATP synthesis. These findings offer new insights into the bacterial-nanoparticles interaction at the transcriptional level, and advance our understanding of impacts of CuO NPs on SRB in the environment.

Interaction of CuO nanoparticles with duckweed (Lemna minor. L): Uptake, distribution and ROS production sites

CuO engineered nanoparticles (NPs) are of increasing concern due to their extensive use in daily life and adverse effect on aquatic organisms. The investigations on the toxicity of CuO NPs to aquatic plants through uptake from roots versus fronds are limited. This paper discusses the interactions of CuO NPs with Lemna minor, a floating plant. After CuO NPs (150 μg L−1) exposure for 7 days, the frond number, frond surface area and dry weights of whole plants significantly decreased by 32%, 47% and 33%; the responses were dose-dependent. Microscopy imaging showed that the epidermis was severely damaged in fronds, edges were severely sloughed off and cell integrity was damaged in roots. Shrinkage of both chloroplast and starch grains were observed in the frond cells. Internalization of CuO NPs in root and frond cells during CuO NPs (1 mg L−1) exposure was confirmed with the root Cu levels of Lemna minor being three times higher than the fronds by using transmission electron microscopy and flame atomic absorption spectrophotometry. Reactive oxygen species, mainly H2O2 (increased by 56%) and ·OH (increased by 57%), accumulated in Lemna minor tissues in response to CuO NPs exposure. Moreover, chloroplasts were confirmed as a site of ROS production. These findings are helpful for better understanding the biological responses of aquatic plants upon NPs exposure.

Enhanced organics and Cu2+ removal in electroplating wastewater by bioaugmentation

With the improvement of electroplating process and products requirement, refractory organics, heavy metals or even heavy metal nanoparticles (NP) exist simultaneously in electroplating wastewater inevitably, makes electroplating wastewater treatment effluent difficult to meet the discharge standard. In order to improve the organics removal under the exposure of CuO NP, strains (designated as L1–L5) that have both organics degradation and Cu2+ tolerance capacities were isolated and employed in the electroplating wastewater bioaugmentation treatment using a hydrolytic/anoxic/oxic-membrane bioreactor. The Cu2+ adsorption process followed pseudo-second order kinetics and the isotherms fit well to Langmuir isotherm model. L2, L3 and L4 showed higher Cu2+ adsorption capacity than that of L1 and L5. Under the optimal condition, the maximum Cu2+ adsorption capacity of L2, L3 and L4 was 34.15, 45.68 and 26.72 mg g−1, respectively. Their average COD removal efficiency achieved 65.7 ± 10.9%, 61.5 ± 6.7% and 71.6 ± 6.0%, respectively. The three isolates were used to construct consortia with the inoculum concentration of 400 mg L−1. One-time and repeated inoculations were evaluated to find the applicable strategy. Repeated inoculation resulted in a better COD and Cu removal performance (76.2 ± 2.6% and 98.5 ± 0.3%, respectively) than those of one-time inoculation (69.0 ± 2.0% and 98.0 ± 0.3%, respectively). The most functionally stable, balanced and resistant bacterial community was formed in the one-time inoculation system while for fungal community it was formed in the repeated inoculation system.

Uptake, Distribution, and Transformation of CuO NPs in a Floating Plant Eichhornia crassipes and Related Stomatal Responses.

Engineered nanoparticles (NPs) are being released into aquatic environments with their increasing applications. In this work, we investigated the interaction of CuO NPs with a floating plant, water hyacinth (Eichhornia crassipes). CuO NPs (50 mg/L) showed significant growth inhibition on both roots and shoots of E. crassipes after 8-day exposure, much higher than that of the bulk CuO particles (50 mg/L) and their corresponding dissolved Cu2+ ions (0.30 mg/L). Scanning electron and light microscopic observations showed that the root caps and meristematic zone of E. Crassipes were severely damaged after CuO NP exposure, with disordered cell arrangement and a destroyed elongation zone of root tips. It is confirmed that CuO NPs could be translocated to shoot from both roots and submerged leaves. As detected by X-ray absorption near-edge spectroscopy analysis (XANES), CuO NPs were observed in roots, submerged leaves, and emerged leaves. Cu2S and other Cu species were also detected in these tissues, providing solid evidence of the transformation of CuO NPs. In addition, stomatal closure was observed during CuO NPs-leaf contact, which was induced by the production of H2O2 and increased Ca level in leaf guard cells. These findings are helpful for better understanding the fate of NPs in aquatic plants and related biological responses.

Exposure to metal oxide nanoparticles in physiological fluid induced synergistic biological effects in a keratinocyte model

Nanoparticles (NPs) possess distinctive physicochemical properties that in addition to differentiating them from their bulk counterparts can induce negative cellular consequences. Standard in vitro systems have served as the primary model for NP safety evaluations, but suffer from a lack physiological relevance. One way to overcome this limitation and evaluate NP characteristics under more accurate conditions is through the use of artificial physiological fluids, which mimic the composition of in vivo environments. In this study, we identified that copper oxide (CuO) and titanium dioxide (TiO2) NPs displayed modified behavior when dispersed in artificial interstitial fluid (IF) versus traditional media, including extensive agglomeration and increased particle deposition. When keratinocyte cells underwent CuO NP exposure, synergistic stress and toxicity responses occurred within an IF environment, correlating with augmented particle deposition. However, following IF incubation alone or concurrently with TiO2 NPs, which are not innately toxic, no combinatorial responses were identified. These results indicate that synergistic outcomes arise when toxic NPs undergo fluid-induced alterations to key physicochemical properties and behaviors. This study highlights the necessity of carrying out NP characterization and safety assessments in physiologically-representative environments; as altered behavior patterns have the potential to induce bioresponses not identified within traditional models.

Interactions of CuO nanoparticles with the algae Chlorella pyrenoidosa: adhesion, uptake, and toxicity

The potential adverse effects of CuO nanoparticles (NPs) have increasingly attracted attention. Combining electron microscopic and toxicological investigations, we determined the adhesion, uptake, and toxicity of CuO NPs to eukaryotic alga Chlorella pyrenoidosa. CuO NPs were toxic to C. pyrenoidosa, with a 72 h EC50 of 45.7 mg/L. Scanning electron microscopy showed that CuO NPs were attached onto the surface of the algal cells and interacted with extracellular polymeric substances (EPS) excreted by the organisms. Transmission electron microscopy (TEM) showed that EPS layer of algae was thickened by nearly 4-fold after CuO NPs exposure, suggesting a possible protective mechanism. In spite of the thickening of EPS layer, CuO NPs were still internalized by endocytosis and were stored in algal vacuoles. TEM and electron diffraction analysis confirmed that the internalized CuO NPs were transformed to Cu2O NPs (d-spacing, ∼0.213 nm) with an average size approximately 5 nm. The toxicity investigation demonstrated that severe membrane damage was observed after attachment of CuO NPs with algae. Reactive oxygen species generation and mitochondrial depolarization were also noted upon exposure to CuO NPs. This work provides useful information on understanding the role of NPs–algae physical interactions in nanotoxicity.

CuO Nanoparticle Interaction with Arabidopsis thaliana: Toxicity, Parent-Progeny Transfer, and Gene Expression.

CuO nanoparticles (NPs) (20, 50 mg L(-1)) inhibited seedling growth of different Arabidopsis thaliana ecotypes (Col-0, Bay-0, and Ws-2), as well as the germination of their pollens and harvested seeds. For most of growth parameters (e.g., biomass, relative growth rate, root morphology change), Col-0 was the more sensitive ecotype to CuO NPs compared to Bay-0 and Ws-2. Equivalent Cu(2+) ions and CuO bulk particles had no effect on Arabidopsis growth. After CuO NPs (50 mg L(-1)) exposure, Cu was detected in the roots, leaves, flowers and harvested seeds of Arabidopsis, and its contents were significantly higher than that in CuO bulk particles (50 mg L(-1)) and Cu(2+) ions (0.15 mg L(-1)) treatments. Based on X-ray absorption near-edge spectroscopy analysis (XANES), Cu in the harvested seeds was confirmed as being mainly in the form of CuO (88.8%), which is the first observation on the presence of CuO NPs in the plant progeny. Moreover, after CuO NPs exposure, two differentially expressed genes (C-1 and C-3) that regulated root growth and reactive oxygen species generation were identified, which correlated well with the physiological root inhibition and oxidative stress data. This current study provides direct evidence for the negative effects of CuO NPs on Arabidopsis, including accumulation and parent-progeny transfer of the particles, which may have significant implications with regard to the risk of NPs to food safety and security.