Copper oxide nanoparticles can induce toxicity to the freshwater shredder Allogamus ligonifer

Effects of copper and cadmium on stream leaf decomposition: evidence from a microcosm study

We seek to understand how copper and cadmium act on leaf litter decomposition by their effects on microbial conditioning and litter fragmentation by invertebrates. In this study, we evaluated, in an integrated manner, different biological elements responsible for functioning of streams. Thus, we performed a microcosm assay with different concentrations for the two metals and their combination, evaluating their effects on fungi sporulation rate, consumption rate by shredders, and, consequently, the leaf litter decomposition rates. Sporulation rates were affected by all copper concentrations tested 10 ×  = 16 µg L-1 and 25 ×  = 40 µg L-1) but significantly reduced only at the highest concentration of cadmium (25 ×  = 22.5 µg L-1). Increased copper and cadmium concentrations reduced the consumption of leaf litter by Phylloicus at 60%. The concentrations (10 × and 25 ×) of both metals resulted in a reduction in decomposition rates. When combined, copper and cadmium negatively affected microbial conditioning, consumption by shredders, and leaf litter decomposition. Increases in concentrations of copper and cadmium directly affected organic matter decomposition in aquatic environments. Thus, the presence of a high concentration of heavy metals in aquatic environments alters the functioning of ecosystems. As trace-elements occur in a combined manner in environments, our results show that the combined effects of different metals potentiate the negative effects on ecosystem processes.

Impacts of low concentrations of nanoplastics on leaf litter decomposition and food quality for detritivores in streams

In forested streams, leaf litter decomposition is a vital ecosystem process, governed primarily by aquatic hyphomycetes. These fungi are crucial mediators of nutrients and energy to invertebrates and higher trophic levels. Very little information is available on the impact of low concentrations of different sizes of nanoplastic particles (NPPs) on leaf litter decomposition and aquatic hyphomycetes communities. Besides, NPPs impact on leaf litter nutritional quality and invertebrate feeding behaviour is unknown. We conducted a microcosm assay with varying concentrations (0-25 μg L^-1) of small (100 nm; SNPPs) and large (1000 nm; LNPPs) plastic particles to assess their impact on leaf litter decomposition, sporulation rates and community structure of aquatic hyphomycetes. Furthermore, leaf litter was retrieved and fed to invertebrates to assess feeding rates. Our results indicated that leaf litter decomposition, fungal sporulation and abundance were significantly affected by NPPs concentrations and sizes. By contrast, leaf litter nutritional quality was impacted only by sizes. The NPPs, particularly SNPPs, augmented leaf litter polyunsaturated fatty acids (18-31%), consequently improving food quality; however, invertebrates' feeding rates were not impacted. Overall, our study provides novel insights on the risks posed by NPPs with pronounced impact at the basal trophic level.

Transformation and release of micronized Cu used as a wood preservative in treated wood in wetland soil

Micronized Cu (μ-Cu) is used as a wood preservative, replacing toxic chromated copper arsenate (CCA). Micronized Cu is malachite [Cu₂CO₃(OH)₂] that has been milled to micron/submicron particles, with many particle diameters less than 100 nm, mixed with biocides and then used to treat wood. In addition to concerns about the fate of the Cu from μ-Cu, there is interest in the fate of the nano-Cu (n-Cu) constituents. We examined movement of Cu from μ-Cu-treated wood after placing treated-wood stakes into model wetland ecosystems. Release of Cu into surface and subsurface water was monitored. Surface water Cu reached maximum levels 3 days after stake installation and remained elevated if the systems remained inundated. Subsurface water Cu levels were 10% of surface water levels at day 3 and increased gradually thereafter. Sequential filtering indicated that a large portion of the Cu in solution was associating with soluble organics, but there was no evidence for n-Cu in solution. After 4 months, Cu in thin-sections of treated wood and adjacent soil were characterized with micro X-ray absorption fine structure spectroscopy (μ-XAFS). Localization and speciation of Cu in the wood and adjacent soil using μ-XAFS clearly indicated that Cu concentrations decreased over time in the treated wood and increased in the adjacent soil. However, n-Cu from the treated wood was not found in the adjacent soil or plant roots. The results of this study indicate that Cu in the μ-Cu-treated wood dissolves and migrates into adjacent soil and waters primarily in ionic form (i.e., Cu²⁺) and not as nano-sized Cu particles. A reduced form of Cu (Cu₂S) was identified in deep soil proximal to the treated wood, indicating strong reducing conditions. The formation of the insoluble Cu₂S effectively removes some portion of dissolved Cu from solution, reducing movement of Cu²⁺ to the water column and diminishing exposure.

Photoactive titanium dioxide nanoparticles modify heterotrophic microbial functioning

Nanoparticulate titanium dioxide (nTiO₂) is frequently applied, raising concerns about potential side effects on the environment. While various studies have assessed structural effects in aquatic model ecosystems, its impact on ecosystem functions provided by microbial communities (biofilms) is not well understood. This is all the more the case when considering additional stressors, such as UV irradiation - a factor known to amplify nTiO₂-induced toxicity. Using pairwise comparisons, we assessed the impact of UV (UV-A = 1.6 W/m²; UV-B = 0.7 W/m²) at 0, 20 or 2000 μg nTiO₂/L on two ecosystem functions provided by leaf-associated biofilms: while leaf litter conditioning, important for detritivorous invertebrate nutrition, seems unaffected, microbial leaf decomposition was stimulated (up to 25%) by UV, with effect sizes being higher in the presence of nTiO₂. Although stoichiometric and microbial analyses did not allow for uncovering the underlying mechanism, it seems plausible that the combination of a shift in biofilm community composition and activity together with photodegradation as well as the formation of reactive oxygen species triggered changes in leaf litter decomposition. The present study implies that the multiple functions a microbial community performs are not equally sensitive. Consequently, relying on one of the many functions realized by the same microbial community may be misleading for environmental management.

Copper/Carbon Core/Shell Nanoparticles: A Potential Material to Control the Fish Pathogen Saprolegnia parasitica

Copper-based fungicides have a long history of usage in agriculture and aquaculture. With the rapid development of metal-based nanoparticles, copper-based nanoparticles have attracted attention as a potential material for prevention and control of Saprolegnia parasitica. The present study investigated the effectiveness of copper/carbon core/shell nanoparticles (CCCSNs) and a commercial CCCSNs filter product (COPPERWARE®) against S. parasitica in a recirculating system. Results showed that the growth of agar plugs with mycelium was significantly suppressed after exposure to both CCCSNs powder and COPPERWARE® filters. Even the lowest concentration of CCCSNs used in our study (i.e., 100 mg/mL) exhibited significant inhibitory effects on S. parasitica. The smallest quantity of the filter product COPPERWARE® (3.75 × 3.7 × 1.2 cm, 2.58 g) used in our aquarium study also demonstrated significant inhibition compared with the control group. However, we observed leaching of copper into the water especially when larger quantities of COPPERWARE® were used. Water turbidity issues were also observed in tanks with the filter material. Besides these issues, which should be further investigated if the product is to be used on aquatic species sensitive to copper, CCCSNs has promising potential for water disinfection.

Can photocatalytic and magnetic nanoparticles be a threat to aquatic detrital food webs?

Freshwaters are likely to serve as reservoirs for engineered nanomaterials (ENMs) due to their accelerated unintentional release, increasing the relevance of assessing their impacts on aquatic biota and the ecosystem processes they drive. Stream-dwelling microbes, particularly fungi, and invertebrate shredders play an essential role in the decomposition of organic matter and transfer of energy to higher trophic levels. We assessed the impacts of two photocatalytic (nano-TiO₂ and erbium doped nano-TiO₂) and one magnetic (nano-CoFe₂O₄) ENMs on detrital-based food webs in freshwaters by exposing chestnut leaves, colonized by stream-dwelling microbes, to a series of concentrations (0.25-150 mg L^-1) of these ENMs. Microbial decomposition and biomass of fungal communities, associated with leaves, were not affected by the ENMs. However, the activities of antioxidant enzymes of microbial decomposers were significantly (P < 0.05) stimulated by ENMs in a concentration-dependent way, suggesting oxidative stress in stream microbial communities. The stronger responses of these stress biomarkers against nano-TiO₂ (increase upto 837.5% for catalase, 1546.8% for glutathione peroxidase and 1154.6% for glutathione S-transferase) suggest a higher toxicity of this ENM comparing to the others. To determine whether the effects could be transferred across trophic levels, the invertebrate shredder Sericostoma sp. was exposed to ENMs (1 and 50 mg L^-1) for 5 days either via contaminated water or contaminated food (leaf litter). Leaf consumption rate by shredders decreased significantly (P < 0.05) with increasing concentrations of ENMs via food or water; the effects were more pronounced when exposure occurred via contaminated food (up to 99.3%, 90.7% and 90.3% inhibition by nano-Er:TiO₂, nano-CoFe₂O₄ and nano-TiO₂, respectively). Overall, the tested photocatalytic and magnetic ENMs can be harmful to microbial decomposers and invertebrate shredders further compromising detrital-based food webs in streams.

Biochemical and functional responses of stream invertebrate shredders to post-wildfire contamination

Forests in Mediterranean Europe including Portugal are highly susceptible to wildfires. Freshwaters are often exposed to post-wildfire contamination that contains several toxic substances, which may impose risk to freshwater organisms and ecosystem functions. However, knowledge on the impacts of post-wildfire runoffs from different origins on freshwater biota is scarce. In forest streams, invertebrate shredders have a major contribution to aquatic detrital-based food webs, by translocating energy and nutrients from plant-litter to higher trophic levels. We investigated the leaf consumption behaviour and the responses of oxidative and neuronal stress enzymatic biomarkers in the freshwater invertebrate shredder Allogamus ligonifer after short-term exposure (96 h) to post-wildfire runoff samples from Pinus and Eucalyptus plantation forests and stream water from a burnt catchment in Portugal. Chemical analyses indicated the presence of various metals and PAHs at considerable concentrations in all samples, although the levels were higher in the runoff samples from forests than in the stream water. The shredding activity was severely inhibited by exposure to increased concentrations of post-wildfire runoff samples from both forests. The dose-response patterns of enzymatic biomarkers suggest oxidative and neuronal stress in the shredders upon exposure to increasing concentrations of post-wildfire runoffs. The impacts were more pronounced for the runoffs from the burnt forests. Moreover, the response patterns suggest that the energy from the feeding activity of shredders might have contributed to alleviate the stress in A. ligonifer. Overall, the outcomes suggest that the post-wildfire contamination can induce sublethal effects on invertebrate shredders with impacts on key ecological processes in streams.

Fungistatic effect of agrochemical and pharmaceutical fungicides on non-target aquatic decomposers does not translate into decreased fungi- or invertebrate-mediated decomposition

Leaf litter decomposition is a key ecological process in freshwater ecosystems. Fungi, particularly aquatic hyphomycetes, play a major role in organic matter turnover and constitute a pivotal node in detrital food webs. The extensive use of antifungal formulations, which include agrochemicals and pharmaceuticals, is a threat to biodiversity and may affect non-target microbial and invertebrate decomposer communities. Using a laboratory approach, we assessed the effects of tebuconazole (agrochemical), clotrimazole and terbinafine (pharmaceuticals) on aquatic communities and on the decomposition of plant litter. Alder leaves were colonized by natural microbiota in a clean stream, and then exposed in microcosms to 8 concentrations of each fungicide (10 to 1280 μg L^-1). Fungicides led to shifts in species dominance in all tested concentrations, but no effects on leaf decomposition were observed. In addition, tebuconazole and clotrimazole strongly reduced fungal biomass and reproduction, whilst terbinafine stimulated fungal reproduction at lower concentrations but had no measurable effects on fungal biomass. Subsequently, the indirect effects of the fungicides were assessed on the next trophic level (detritivore invertebrates), by evaluating leaf consumption by a specialist (Allogamus sp.) and a generalist (Chironomus riparius) species, when feeding on fungicide-preconditioned leaves. The feeding activity of C. riparius and Allogamus sp. was not affected, and as expected, specialists were more efficient than generalists in exploring leaves as a dietary resource. However, results indicated that these fungicides have direct negative effects on microbial decomposers, and thus may compromise ecosystem functions on the long term.

Maodaa S, Allam AA, Elshaer N. Ecofriendly Synthesis and Insecticidal Application of Copper Nanoparticles against the Storage Pest Tribolium castaneum

In spite of great developments in the agricultural field and plant productivity in the last decades, the concern about the control of agricultural pests is still continuous. However, pest management is expected to have more effects from nanomaterials by providing innovative solutions. The current study confirms the biotransformation of copper nanoparticles (CuNPs) using a cell-free culture extract of metal copper-resistant bacteria Pseudomonas fluorescens MAL2, which was isolated from heavy metal-contaminated soils collected from Sharqia Governorate, Egypt. The local screened bacterial isolate, Pseudomonas fluorescens MAL2, is similar to Pseudomonas fluorescens DSM 12442T DSM. After optimization of growth conditions, F-Base medium was found to be the best medium and pH 7, temperature 35 °C, concentration of CuSO4·5H2O 300 ppm, 10 mL supernatant: 40 mL CuSO4·5H2O (300 ppm), and reaction time 90 min were recorded as the best growth conditions to the fabrication of CuNPs. The formed CuNPs were characterized using initially visual observation of the change in the color of the reaction mixture from blue color to the dark green as an indication of CuNPs biotransformation. Then, UV-Vis spectroscopy showed a maximum absorption at 610 nm under the optimum conditions performed. Transmission Electron Microscopy (TEM) revealed the formation of spherical aspect with size ranges from 10:70 nm; moreover, Energy Dispersive X-ray spectroscopy (EDX) indicated the presence of CuNPs and other elements. In addition, the presence of alcohols, phenols, alkenes, and amines is confirmed by Fourier-Transform Infrared spectroscopy (FTIR) spectroscopy analysis. Dynamic Light Scattering (DLS) supported that the Zeta-average size of nanoparticle was 48.07 with 0.227 PdI value. The Zeta potential showed -26.00mV with a single peak. The biosynthesized CuNPs (Bio CuNPs) showed toxicity against the stored grain pest (Tribolium castaneum), where LC50 value was 37 ppm after 5 days of treatment. However, the negligible effect was observed with chemical synthesis of CuNPs (Ch CuNPs) at the same concentration. The results suggest that Bio CuNPs could be used not only as a biocontrol agent, but also as an ecofriendly and inexpensive approach for controlling the stored grain pests.

Interaction of Copper-Based Nanoparticles to Soil, Terrestrial, and Aquatic Systems: Critical Review of the State of the Science and Future Perspectives

In the past two decades, increased production and usage of metallic nanoparticles (NPs) have inevitably increased their discharge into the different compartments of the environment, which ultimately paved the way for their uptake and accumulation in various trophic levels of the food chain. Due to these issues, several questions have been raised on the usage of NPs in everyday life and have become a matter of public health concern. Among the metallic NPs, Cu-based NPs have gained popularity due to their cost-effectiveness and multifarious promising uses. Several studies in the past represented the phytotoxicity of Cu-based NPs on plants. However, comprehensive knowledge is still lacking. Additionally, the impact of Cu-based NPs on soil organisms such as agriculturally important microbes, fungi, mycorrhiza, nematode, and earthworms is poorly studied. This review article critically analyses the literature data to achieve a more comprehensive knowledge on the toxicological profile of Cu-based NPs and increase our understanding of the effects of Cu-based NPs on aquatic and terrestrial plants as well as on soil microbial communities. The underlying mechanism of biotransformation of Cu-based NPs and the process of their penetration into plants have also been discussed herein. Overall, this review could provide valuable information to design rules and regulations for the safe disposal of Cu-based NPs into a sustainable environment.

Uranium toxicity to aquatic invertebrates: A laboratory assay

Uranium mining is an environmental concern because of runoff and the potential for toxic effects on the biota. To investigate uranium toxicity to freshwater invertebrates, we conducted a 96-h acute toxicity test to determine lethal concentrations (testing concentrations up to 262 mg L^-1) for three stream invertebrates: a shredder caddisfly, Schizopelex festiva Rambur (Trichoptera, Sericostomatidae); a detritivorous isopod, Proasellus sp. (Isopoda, Asellidae); and a scraper gastropod, Theodoxus fluviatilis (Gastropoda, Neritidae). Next, we ran a chronic-toxicity test with the most tolerant species (S. festiva) to assess if uranium concentrations found in some local streams (up to 25 μg L^-1) affect feeding, growth and respiration rates. Finally, we investigated whether S. festiva takes up uranium from the water and/or from ingested food. In the acute test, S. festiva survived in all uranium concentrations tested. LC₅₀-96-h for Proasellus sp and T. fluviatilis were 142 mg L^-1 and 24 mg L^-1, respectively. Specimens of S. festiva exposed to 25 μg L^-1 had 47% reduced growth compared with specimens under control conditions (21.5 ± 2.9 vs. 40.6 ± 4.9 μg of mass increase animal^-1·day^-1). Respiration rates (0.40 ± 0.03 μg O₂·h^-1·mg animal^-1) and consumption rates (0.54 ± 0.05 μg μg animal^-1·day^-1; means ± SE) did not differ between treatments. Under laboratory conditions S. festiva accumulated uranium from both the water and the ingested food. Our results indicate that uranium can be less toxic than other metals or metalloids produced by mining activities. However, even at the low concentrations observed in streams affected by abandoned mines, uranium can impair physiological processes, is bioaccumulated, and is potentially transferred through food webs.

Copper-based nanomaterials for environmental decontamination - An overview on technical and toxicological aspects

Synthesis of the various types of engineered nanomaterials has gained a huge attention in recent years for various applications. Copper based nanomaterials are a branch of this category seem to be able to provide an efficient and cost-effective way for the treatment of the persistent effluents. The present work aimed to study the various parameters may involve in the overall performance of the copper based nanomaterials for environmental clean-up purposes. To this end, the related characteristics of copper based nanomaterials and their effects on the nanomaterials reactivity and the environmental and operating parameters have been critically reviewed. Toxicological study of the copper based nanomaterials has been also considered as a factor with high importance for the selection of a typical nanomaterial with optimum performance and minimum environmental and health subsequent effects.

Toxicity of Metal Oxide Nanoparticles

In the recent times, nanomaterials are used in many sectors of science, medicine and industry, without revealing its toxic effects. Thus, it is in urgent need for exploring the toxicity along with the application of such useful nanomaterials. Nanomaterials are categorized with a particle size of 1-100 nm. They have gained increasing attention because of their novel properties, including a large specific surface area and high reaction activity. The various fundamental and practical applications of nanomaterials include drug delivery, cell imaging, and cancer therapy. Nanosized semiconductors have their versatile applications in different areas such as catalysts, sensors, photoelectronic devices, highly functional and effective devices etc. Metal oxides contribute in many areas of chemistry, physics and materials science. Mechanism of toxicity of metal oxide nanoparticles can occur by different methods like oxidative stress, co-ordination effects, non-homeostasis effects, genotoxicity and others. Factors that affect the metal oxide nanoparticles were size, dissolution and exposure routes. This chapter will explain elaborately the toxicity of metal oxide nano structures in living beings and their effect in ecosystem.

Temperature modulates AgNP impacts on microbial decomposer activity

Silver nanoparticles (AgNP)s can have toxic effects on aquatic species and compromise important ecosystem processes. AgNP impacts have been the focus of much research, but their effects under different environmental contexts, such as the increase in global temperature are difficult to predict. The aim of this study was to evaluate the interactive effects of AgNPs and temperature on the activity and diversity of microbial decomposers of plant litter in streams. Litter-associated microbial communities were exposed in microcosms to increased concentrations of AgNPs (50 to 75000μgL^-1) and AgNO₃ (5 to 7500μgL^-1) and kept for 21days at 10°C, 16°C and 23°C. Effects of AgNPs and AgNO₃ were assessed based on leaf mass loss and litter-associated microbial communities by measuring microbial diversity, the activity of fungal extracellular enzymes, and fungal biomass and reproduction. Increase in temperature stimulated leaf mass loss, but not fungal biomass and reproduction. Increased AgNP and AgNO₃ concentrations inhibited fungal reproduction and diversity, particularly at 23°C. Activities of the extracellular enzymes phenol oxidase and β-glucosidase were generally higher at 23°C. Microbial communities were mainly structured by AgNP and AgNO₃ concentrations more than by temperature. The negative effects of nano and ionic Ag on microbial activity were more pronounced at 10 and 23°C. The behavior of AgNPs was more related to water physical and chemical characteristics (pH) than to temperature. Results highlight the importance of considering different environmental scenarios when examining NP toxicity to freshwater biota and ecosystem processes.

How do physicochemical properties influence the toxicity of silver nanoparticles on freshwater decomposers of plant litter in streams?

AgNP physicochemical properties may affect AgNP toxicity, but their effects on plant litter decomposition and the species driving this key ecosystem process in freshwaters have been poorly investigated. We assessed the impacts of AgNPs with different size and surface coating (100nm PVP (polyvinylpyrrolidone)-dispersant, 50-60nm and 35nm uncoated) on freshwater decomposers of leaf litter by exposing leaf associated microbial assemblages to increasing concentrations of AgNPs (up to 200mgL^-1) and of AgNO₃ (up to 25mgL^-1). We further conducted a feeding preference experiment with a common invertebrate shredder, Limnephilus sp., which was allowed to feed on microbially-colonized leaves previously exposed to AgNPs and AgNO₃. Leaf decomposition and microbial activity and diversity were inhibited when exposed to increased concentrations of 100nm AgNPs (≥25mgL^-1), while microbial activity was stimulated by exposure to 35nm AgNPs (≥100mgL^-1). Invertebrate shredders preferred leaves exposed to 35nm AgNPs (25mgL^-1) and avoided leaves exposed to AgNO₃ (≥2mgL^-1). Results from the characterization of AgNPs by dynamic light scattering revealed that AgNps with PVP-dispersant were more stable than the uncoated AgNPs. Our results highlight the importance of considering the physicochemical properties of NPs when assessing their toxicity to litter decomposers in freshwaters.

Shorter lifetime of a soil invertebrate species when exposed to copper oxide nanoparticles in a full lifespan exposure test

Toxicity tests that last the all life duration of the organisms are not common, instead, long-term tests usually include one reproductive cycle. In the present study we optimized and propose a lifespan (all life) term test using Enchytraeus crypticus (Oligochaeta). The effect of copper oxide nanoparticles (CuO-NPs) was assessed in this lifespan test and compared to copper salt (CuCl₂), using the same effect concentrations on reproduction (EC₅₀). Monitored endpoints included survival and reproduction over-time (202 days). Results from survival showed that CuO-NPs caused shorter life of the adults compared to CuCl₂ (control LT₅₀: 218 days > CuCl₂ LT₅₀: 175 days > CuO-NPs LT₅₀: 145 days). The effect was even more amplified in terms of reproduction (control ET₅₀: 158 days > CuCl₂ ET₅₀: 138 days > CuO-NPs ET₅₀: 92 days). Results suggest that CuO-NPs may cause a higher Cu effect via a trojan horse mechanism. The use of lifespan tests brings a novel concept in soil ecotoxicity, the longevity. This is a particularly important aspect when the subject is nanomaterials toxicity, where longer term exposure time is expected to reveal unpredicted effects via the current short/long-term tests. The present study confirms this higher effect for CuO-NPs.

Effects of copper oxide nanomaterials (CuONMs) are life stage dependent - full life cycle in Enchytraeus crypticus

Copper oxide nanomaterials (CuONMs) have various applications in industry and enter the terrestrial environment, e.g. via sewage sludge. The effects of CuONMs and copper chloride (CuCl₂) were studied comparing the standard enchytraeid reproduction test (ERT) and the full life cycle test (FLCt) with Enchytraeus crypticus. CuONMs mainly affected growth or juveniles' development, whereas CuCl₂ mainly affected embryo development and/or hatching success and adults survival. Compared to the ERT, the FLCt allowed discrimination of effects between life stages and provided indication of the underlying mechanisms; further, the FLCt showed increased sensitivity, e.g. reproductive effects for CuONMs: EC₁₀ = 8 mg Cu/kg and EC₁₀ = 421 mg Cu/kg for the FLCt and the ERT respectively. The performance of the FLCt is preferred to the ERT and we recommend it as a good alternative to assess hazard of NMs. Effects of CuONMs and CuCl₂ are life stage dependent and are different between Cu forms.

Ecotoxicological effects and mechanism of CuO nanoparticles to individual organisms

Copper oxide nanoparticles (CuO NPs) are used extensively in a variety of applications such as antimicrobial agent, photo-catalyst and gas sensors. The expanding production and widespread utilization of CuO NPs may pose risks to individual organisms and ecosystem. Comprehensive understanding the CuO NPs-induced adverse effects and their underlying mechanism are of great importance to assess the environmental risk of CuO NPs and to expand their use safely. However, toxic effects of CuO NPs to individual organisms and the mechanism of their action are still deficient and ambiguities. To ensure the safely use of CuO NPs, more attention should be paid on the long-term and chronic effects of CuO NPs at low concentration. Efforts should be devoted to develop techniques to differentiate toxicities induced by CuO NPs or dissolved Cu²⁺, and to reduce the toxicity of CuO NPs by controlling the particle diameter, modifying surface characteristic, selecting proper exposure route and regulating the release of Cu²⁺ from CuO NPs. This review provides a brief overview of toxicity of CuO NPs to individual organisms with a broad range of taxa (microorganisms, algae, plants, invertebrates and vertebrates) and to discuss the underlying toxicity mechanisms including oxidative stress, dynamic unbalance and coordination effects.

Solid lipid nanoparticles affect microbial colonization and enzymatic activity throughout the decomposition of alder leaves in freshwater microcosms

Solid lipid nanoparticles (SLNs) are used as carriers for drug delivery, and are high biocompatible and designed to endure in the host organism. Despite its current industrial production is low, many of these substances are available on the market, and much more are in the production pipeline. As a result, many of them will end in aquatic systems raising the question whether they can pose a risk to aquatic biota and the associated ecological processes. Microbial decomposers of plant litter, play a key role in forested streams being responsible for the energy flow between terrestrial and aquatic environments. Here, we investigated the effects of SLNs on alder leaf litter decomposition by aquatic microbes. Alder leaves were immersed in a stream of Northeast Portugal to allow microbial colonization before being exposed in microcosms of two types of SLNs at two concentrations for 42 days. Results showed that rates of leaf decomposition decreased with exposure to SLNs. Bacterial biomass was not inhibited by SLNs, and cultivable fungi densities remained constant (SLN-A) or increased (SLN-C) compared with control microcosms. The type and concentration of SLNs influenced differently the leaf colonization by fungi as well as fungal sporulation rate. These effects were accompanied by changes in the community extraenzymatic profile: the activities of alkaline phosphatase, acidic phosphatase, Naphthol-AS-BI-phosphohydrolase (P cycle) and lipases increased in the SLNs microcosms. This study provided the first evidence of the adverse effects of the release of SLNs to streams on leaf litter decomposition. Those effects seem to depend on the composition and concentration of SLNs, as well on the microbial target group, or enzyme. Thus, prior to massive industrial production of these nanomaterials, some measures should be taken to avoid environmental impact affecting the microbial communities responsible for detritus decomposition.

Plant Mediated Green Synthesis of CuO Nanoparticles: Comparison of Toxicity of Engineered and Plant Mediated CuO Nanoparticles towards Daphnia magna

Research on green production methods for metal oxide nanoparticles (NPs) is growing, with the objective to overcome the potential hazards of these chemicals for a safer environment. In this study, facile, ecofriendly synthesis of copper oxide (CuO) nanoparticles was successfully achieved using aqueous extract of Pterospermum acerifolium leaves. P. acerifolium-fabricated CuO nanoparticles were further characterized by UV-Visible spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and dynamic light scattering (DLS). Plant-mediated CuO nanoparticles were found to be oval shaped and well dispersed in suspension. XPS confirmed the elemental composition of P. acerifolium-mediated copper nanoparticles as comprised purely of copper and oxygen. DLS measurements and ion release profile showed that P. acerifolium-mediated copper nanoparticles were more stable than the engineered CuO NPs. Copper oxide nanoparticles are used in many applications; therefore, their potential toxicity cannot be ignored. A comparative study was performed to investigate the bio-toxic impacts of plant-synthesized and engineered CuO nanoparticles on water flea Daphnia. Experiments were conducted to investigate the 48-h acute toxicity of engineered CuO NPs and plant-synthesized nanoparticles. Lower EC50 value 0.102 ± 0.019 mg/L was observed for engineered CuO NPs, while 0.69 ± 0.226 mg/L was observed for plant-synthesized CuO NPs. Additionally, ion release from CuO nanoparticles and 48-h accumulation of these nano CuOs in daphnids were also calculated. Our findings thus suggest that the contribution of released ions from nanoparticles and particles/ions accumulation in Daphnia needs to be interpreted with care.

Enzymatic biomarkers can portray nanoCuO-induced oxidative and neuronal stress in freshwater shredders

Commercial applications of nanometal oxides have increased concern about their release into natural waters and consequent risks to aquatic biota and the processes they drive. In forest streams, the invertebrate shredder Allogamus ligonifer plays a key role in detritus food webs by transferring carbon and energy from plant litter to higher trophic levels. We assessed the response profiles of oxidative and neuronal stress enzymatic biomarkers in A. ligonifer after 96h exposure to nanoCuO at concentration ranges <LC₃₀. To better understand the contribution of ionic form in nanoCuO-induced stress, Cu²⁺ released from nanoCuO was quantified and the enzymatic responses to Cu²⁺ exposure at similar effective concentrations were compared. The highest activities of superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) were observed at concentrations <LC₅. The enzymatic activities decreased at effective concentrations between LC₁₀ and LC₃₀. GR activity remained higher than in control at all concentrations. The activity of glutathione S-transferase (GST) increased whereas that of catalase (CAT) decreased at concentrations between LC₁₀ and LC₃₀. The response patterns suggested that antioxidant enzymes could prevent oxidative stress at low concentrations (<LC₁₀) of nanoCuO, thereby contributing to the survival of A. ligonifer. At concentrations between LC₁₀ and LC₃₀, effects of nanoparticulate or released ionic copper on enzyme activities were concentration-dependent, and led to oxidative stress and even to animal death. The activity of acetylcholinesterase (AChE) was strongly inhibited even at concentrations <LC₁₀, suggesting neuronal stress in A. ligonifer.

EU Regulation of Nanobiocides: Challenges in Implementing the Biocidal Product Regulation (BPR)

The Biocidal Products Regulation (BPR) contains several provisions for nanomaterials (NMs) and is the first regulation in the European Union to require specific testing and risk assessment for the NM form of a biocidal substance as a part of the information requirements. Ecotoxicological data are one of the pillars of the information requirements in the BPR, but there are currently no standard test guidelines for the ecotoxicity testing of NMs. The overall objective of this work was to investigate the implications of the introduction of nano-specific testing requirements in the BPR and to explore how these might be fulfilled in the case of copper oxide nanoparticles. While there is information and data available in the open literature that could be used to fulfill the BPR information requirements, most of the studies do not take the Organisation for Economic Co-operation and Development's nanospecific test guidelines into consideration. This makes it difficult for companies as well as regulators to fulfill the BPR information requirements for nanomaterials. In order to enable a nanospecific risk assessment, best practices need to be developed regarding stock suspension preparation and characterization, exposure suspensions preparation, and for conducting ecotoxicological test.

Natural organic matter alters size-dependent effects of nanoCuO on the feeding behaviour of freshwater invertebrate shredders

Nanoparticle size and the presence of natural organic matter (NOM) may influence the toxicity of nanoCuO to aquatic biota, but their interactive effects have been poorly investigated. We examined the feeding behaviour of the invertebrate shredder Allogamus ligonifer when exposed to sublethal concentrations of nanoCuO (50 and 100 mg L(-1)) with three particle sizes (12, 50 and 80 nm) in the absence or presence of humic acid (HA, 100 mg L(-1)) as a proxy of NOM. We further examined the ability of invertebrates to recover from the stressors. In the absence of nanoCuO and HA, the feeding rate of shredders was 0.416 mg leaf DM mg(-1 )animal DM day(-1). The exposure to increased nanoCuO concentrations inhibited the feeding rate and effects were stronger as nanoparticle size decreased (up to 83.3% inhibition for 12 nm particles). The exposure to HA alone inhibited the feeding activity by 52.7%. However, the co-exposure to nanoCuO and HA alleviated the inhibitory effects promoted by smaller and medium sized nanoCuO (up to 29.5%). The recovery of feeding activity by the shredders after stress removal was very low; maximum recovery (16.7%) was found for invertebrates rescued from pre-exposure to lower concentration of nanoCuO with larger size.

Interactions between salt marsh plants and Cu nanoparticles - Effects on metal uptake and phytoremediation processes

The increased use of metallic nanoparticles (NPs) raises the probability of finding NPs in the environment. A lot of information exists already regarding interactions between plants and metals, but information regarding interactions between metallic NPs and plants, including salt marsh plants, is still lacking. This work aimed to study interactions between CuO NPs and the salt marsh plants Halimione portulacoides and Phragmites australis. In addition, the potential of these plants for phytoremediation of Cu NPs was evaluated. Plants were exposed for 8 days to sediment elutriate solution doped either with CuO or with ionic Cu. Afterwards, total metal concentrations were determined in plant tissues. Both plants accumulated Cu in their roots, but this accumulation was 4 to 10 times lower when the metal was added in NP form. For P. australis, metal translocation occurred when the metal was added either in ionic or in NP form, but for H. portulacoides no metal translocation was observed when NPs were added to the medium. Therefore, interactions between plants and NPs differ with the plant species. These facts should be taken in consideration when applying these plants for phytoremediation of contaminated sediments in estuaries, as the environmental management of these very important ecological areas can be affected.

Aquatic acute species sensitivity distributions of ZnO and CuO nanoparticles

Metal oxide nanoparticles are increasingly being produced and will inevitably end up in the aquatic environment. Up till now, most papers have studied individual nanoparticle effects. However, the implementation of these data into a risk assessment tool, needed to characterise their risk to the aquatic environment, is still largely lacking. Therefore, aquatic species sensitivity distributions (SSDs) were constructed for ZnO and CuO nanoparticles and 5% hazard concentrations (HC5) were calculated in this study. The effect of individual nanoparticles on these SSDs was estimated by comparison with bulk SSDs. Additionally, the effect of nanoparticle dynamics (aggregation and dissolution) was considered by evaluating the effect of aggregate size on the toxicity, by estimation of the dissolved fraction and comparison with SSDs for ZnCl2 and CuCl2 inorganic salt. Bacteria, protozoa, yeast, rotifera, algae, nematoda, crustacea, hexapoda, fish and amphibia species were included in the analysis. The results show that algae (Zn) and crustacea (Zn, Cu) are the most sensitive species when exposed to the chemicals. Similar acute sensitivity distributions were obtained for ZnO nanoparticles (HC5: 0.06 with 90% confidence interval: 0.03-0.15 mg Zn/l; 43 data points), bulk ZnO (HC5: 0.06 with CI: 0.03-0.20 mg Zn/l; 23 dps) and ZnCl2 (HC5: 0.03 with CI: 0.02-0.05 mg Zn/l; 261 dps). CuO nanoparticles (HC5: 0.15 with CI: 0.05-0.47 mg Cu/l; 43 dps) are more toxic than the bulk materials (HC5: 6.19 with CI: 2.15-38.11 mg Cu/l; 12 dps) but less toxic than CuCl2 (HC5: 0.009 with CI: 0.007-0.012 mg Cu/l; 594 dps) to aquatic species. However, the combined dissolution and SSD results indicate that the toxicity of these nanoparticles is mainly caused by dissolved metal ions. Based on the available information, no current risk of these nanoparticles to the aquatic environment is expected.

Gene transcription patterns and energy reserves in Daphnia magna show no nanoparticle specific toxicity when exposed to ZnO and CuO nanoparticles

There is still a lot of contradiction on whether metal ions are solely responsible for the observed toxicity of ZnO and CuO nanoparticles to aquatic species. While most experiments have studied nanoparticle effects at organismal levels (e.g. mortality, reproduction), effects at lower levels of biological organization may clarify the role of metal ions, nanoparticles and nanoparticle aggregates. In this study, the effect of ZnO and CuO nanoparticles was tested at two lower levels: energy reserves and gene transcription and compared with zinc and copper salts. Daphnia magna was exposed during 96h to 10% immobilization concentrations of all chemicals, after which daphnids were sampled for determination of glycogen, lipid and protein concentration and for a differential gene transcription analysis using microarray. The dissolved, nanoparticle and aggregated fraction in the medium was characterized. The results showed that ZnO nanoparticles had largely dissolved directly after addition to the test medium. The CuO nanoparticles mostly formed aggregates, while only a small fraction dissolved. The exposure to zinc (both nano and metal salt) had no effect on the available energy reserves. However, in the copper exposure, the glycogen, lipid and protein concentration in the exposed daphnids was lower than in the unexposed ones. When comparing the nanoparticle (ZnO or CuO) exposed daphnids to the metal salt (zinc or copper salt) exposed daphnids, the microarray results showed no significantly differentially transcribed gene fragments. The results indicate that under the current exposure conditions the toxicity of ZnO and CuO nanoparticles to D. magna is solely caused by toxic metal ions.

Fungi from metal-polluted streams may have high ability to cope with the oxidative stress induced by copper oxide nanoparticles

Increased commercialization of products based on metal oxide nanoparticles increases the likelihood that these nanoparticles will be released into aquatic environments, thus making relevant the assessment of their potential impacts on aquatic biota. Aquatic fungi are distributed worldwide and play a key role in organic matter turnover in freshwater ecosystems. The present study investigated the impacts of copper oxide spherical nanoparticles (CuO-NPs; <50 nm powder, 5 levels ≤200 mg/L) on cellular targets and antioxidant defenses in 5 fungal isolates collected from metal-polluted or nonpolluted streams. The CuO-NPs induced oxidative stress in aquatic fungi, as evidenced by intracellular accumulation of reactive oxygen species, and led to plasma membrane damage and DNA strand breaks in a concentration-dependent manner. Effects were more pronounced with a longer exposure time (3 d vs 10 d). Under CuO-NP exposure, mycelia of fungi collected from metal-polluted streams showed less oxidative stress and higher activities of superoxide dismutase and glutathione reductase compared with fungi from nonpolluted streams. The latter fungi responded to CuO-NPs with a stronger stimulation of glutathione peroxidase activity. These findings may indicate that fungi isolated from metal-polluted streams had a greater ability to maintain the pool of reduced glutathione than those from nonpolluted streams. Overall, results suggest that populations adapted to metals may develop mechanisms to cope with the oxidative stress induced by metal nanoparticles.

NanoE-Tox: New and in-depth database concerning ecotoxicity of nanomaterials

The increasing production and use of engineered nanomaterials (ENMs) inevitably results in their higher concentrations in the environment. This may lead to undesirable environmental effects and thus warrants risk assessment. The ecotoxicity testing of a wide variety of ENMs rapidly evolving in the market is costly but also ethically questionable when bioassays with vertebrates are conducted. Therefore, alternative methods, e.g., models for predicting toxicity mechanisms of ENMs based on their physico-chemical properties (e.g., quantitative (nano)structure-activity relationships, QSARs/QNARs), should be developed. While the development of such models relies on good-quality experimental toxicity data, most of the available data in the literature even for the same test species are highly variable. In order to map and analyse the state of the art of the existing nanoecotoxicological information suitable for QNARs, we created a database NanoE-Tox that is available as Supporting Information File 1. The database is based on existing literature on ecotoxicology of eight ENMs with different chemical composition: carbon nanotubes (CNTs), fullerenes, silver (Ag), titanium dioxide (TiO2), zinc oxide (ZnO), cerium dioxide (CeO2), copper oxide (CuO), and iron oxide (FeO x ; Fe2O3, Fe3O4). Altogether, NanoE-Tox database consolidates data from 224 articles and lists altogether 1,518 toxicity values (EC50/LC50/NOEC) with corresponding test conditions and physico-chemical parameters of the ENMs as well as reported toxicity mechanisms and uptake of ENMs in the organisms. 35% of the data in NanoE-Tox concerns ecotoxicity of Ag NPs, followed by TiO2 (22%), CeO2 (13%), and ZnO (10%). Most of the data originates from studies with crustaceans (26%), bacteria (17%), fish (13%), and algae (11%). Based on the median toxicity values of the most sensitive organism (data derived from three or more articles) the toxicity order was as follows: Ag > ZnO > CuO > CeO2 > CNTs > TiO2 > FeO x . We believe NanoE-Tox database contains valuable information for ENM environmental hazard estimation and development of models for predicting toxic potential of ENMs.

Polyhydroxyfullerene binds cadmium ions and alleviates metal-induced oxidative stress in Saccharomyces cerevisiae

The water-soluble polyhydroxyfullerene (PHF) is a functionalized carbon nanomaterial with several industrial and commercial applications. There have been controversial reports on the toxicity and/or antioxidant properties of fullerenes and their derivatives. Conversely, metals have been recognized as toxic mainly due to their ability to induce oxidative stress in living organisms. We investigated the interactive effects of PHF and cadmium ions (Cd) on the model yeast Saccharomyces cerevisiae by exposing cells to Cd (≤5 mg liter(-1)) in the absence or presence of PHF (≤500 mg liter(-1)) at different pHs (5.8 to 6.8). In the absence of Cd, PHF stimulated yeast growth up to 10.4%. Cd inhibited growth up to 79.7%, induced intracellular accumulation of reactive oxygen species (ROS), and promoted plasma membrane disruption in a dose- and pH-dependent manner. The negative effects of Cd on growth were attenuated by the presence of PHF, and maximum growth recovery (53.8%) was obtained at the highest PHF concentration and pH. The coexposure to Cd and PHF decreased ROS accumulation up to 36.7% and membrane disruption up to 30.7% in a dose- and pH-dependent manner. Two mechanisms helped to explain the role of PHF in alleviating Cd toxicity to yeasts: PHF decreased Cd-induced oxidative stress and bound significant amounts of Cd in the extracellular medium, reducing its bioavailability to the cells.

Physiological responses to nanoCuO in fungi from non-polluted and metal-polluted streams

Nanocopper oxide (nanoCuO) is among the most widely used metal oxide nanoparticles which increases their chance of being released into freshwaters. Fungi are the major microbial decomposers of plant litter in streams. Fungal laccases are multicopper oxidase enzymes that are involved in the degradation of lignin and various xenobiotic compounds. We investigated the effects of nanoCuO (5 levels, ≤ 200 mg L(-1)) on four fungal isolates collected from metal-polluted and non-polluted streams by analyzing biomass production, changes in mycelial morphology, laccase activity, and quantifying copper adsorbed to mycelia, and ionic and nanoparticulate copper in the growth media. The exposure to nanoCuO decreased the biomass produced by all fungi in a concentration- and time-dependent manner. Inhibition of biomass production was stronger in fungi from non-polluted (EC₅₀(10 days) ≤ 31 mg L(-1)) than from metal-polluted streams (EC₅₀(10 days) ≥ 65.2 mg L(-1)). NanoCuO exposure led to cell shrinkage and mycelial degeneration, particularly in fungi collected from non-polluted streams. Adsorption of nanoCuO to fungal mycelia increased with the concentration of nanoCuO in the medium and was higher in fungi from non-polluted streams. Extracellular laccase activity was induced by nanoCuO in two fungal isolates in a concentration-dependent manner, and was highly correlated with adsorbed Cu and/or ionic Cu released by dissolution from nanoCuO. Putative laccase gene fragments were also detected in these fungi. Lack of substantial laccase activity in the other fungal isolates was corroborated by the absence of laccase-like gene fragments.

Copper oxide nanoparticles induced mitochondria mediated apoptosis in human hepatocarcinoma cells

Copper oxide nanoparticles (CuO NPs) are heavily utilized in semiconductor devices, gas sensor, batteries, solar energy converter, microelectronics and heat transfer fluids. It has been reported that liver is one of the target organs for nanoparticles after they gain entry into the body through any of the possible routes. Recent studies have shown cytotoxic response of CuO NPs in liver cells. However, the underlying mechanism of apoptosis in liver cells due to CuO NPs exposure is largely lacking. We explored the possible mechanisms of apoptosis induced by CuO NPs in human hepatocellular carcinoma HepG2 cells. Prepared CuO NPs were spherical in shape with a smooth surface and had an average diameter of 22 nm. CuO NPs (concentration range 2–50 µg/ml) were found to induce cytotoxicity in HepG2 cells in dose-dependent manner, which was likely to be mediated through reactive oxygen species generation and oxidative stress. Tumor suppressor gene p53 and apoptotic gene caspase-3 were up-regulated due to CuO NPs exposure. Decrease in mitochondrial membrane potential with a concomitant increase in the gene expression of bax/bcl2 ratio suggested that mitochondria mediated pathway involved in CuO NPs induced apoptosis. This study has provided valuable insights into the possible mechanism of apoptosis caused by CuO NPs at in vitro level. Underlying mechanism(s) of apoptosis due to CuO NPs exposure should be further invested at in vivo level.