Environmental implications of nanoparticle aging in the processing and fate of copper-based nanomaterials

Lettuce (Lactuca sativa L.) alters its metabolite accumulation to cope with CuO nanoparticles by promoting antioxidant production and carbon metabolism

Copper-based nanoparticles (NPs) are gradually being introduced as sustainable agricultural nanopesticides. However, the effects of NPs on plants requires carefully evaluation to ensure their safe utilization. In this study, leaves of 2-week-old lettuce (Lactuca sativa L.) were exposed to copper oxide nanoparticles (CuO-NPs, 0 [CK], 100 [T1], and 1000 [T2] mg/L) for 15 days. A significant Cu accumulation (up to 1966 mg/kg) was detected in lettuce leaves. The metabolomics revealed a total of 474 metabolites in lettuce leaves, and clear differences were observed in the metabolite profiles of control and CuO-NPs treated leaves. Generally, phenolic acids and alkaloids, which are important antioxidants, were significantly increased (1.26-4.53 folds) under foliar exposure to NPs; meanwhile, all the significantly affected flavonoids were down-regulated after CuO-NP exposure, indicating these flavonoids were consumed under oxidative stress. Succinic and citric acids, which are key components of the tricarboxylic acid cycle, were especially increased under T2, suggesting the energy and carbohydrate metabolisms were enhanced under high-concentration CuO-NP treatment. There was also both up- and down-regulation of fatty acids, suggesting cell membrane fluidity and function responded to CuO-NPs. Galactinol, which is related to galactose metabolism, and xanthosine, which is crucial in purine and caffeine metabolism, were down-regulated under T2, indicating decreased stress resistance and disturbed nucleotide metabolism under the high CuO-NP dose. Moreover, the differentially accumulated metabolites were significantly associated with plant growth and its antioxidant ability. Future work should focus on controlling the overuse or excessive release of NPs into agricultural ecosystems to limit their adverse effects.

Green Synthesis of Silver Nanoparticles and their Potential Applications in Mitigating Cancer

In recent years, the field of nanotechnology has brought about significant advancements that have transformed the landscape of disease diagnosis, prevention, and treatment, particularly in the realm of medical science. Among the various approaches to nanoparticle synthesis, the green synthesis method has garnered increasing attention. Silver nanoparticles (AgNPs) have emerged as particularly noteworthy nanomaterials within the spectrum of metallic nanoparticles employed for biomedical applications. AgNPs possess several key attributes that make them highly valuable in the biomedical field. They are biocompatible, cost-effective, and environmentally friendly, rendering them suitable for various bioengineering and biomedical applications. Notably, AgNPs have found a prominent role in the domain of cancer diagnosis. Research investigations have provided evidence of AgNPs' anticancer activity, which involves mechanisms such as DNA damage, cell cycle arrest, induction of apoptosis, and the regulation of specific cytokine genes. The synthesis of AgNPs primarily involves the reduction of silver ions by reducing agents. Interestingly, natural products and living organisms have proven to be effective sources for the generation of precursor materials used in AgNP synthesis. This comprehensive review aims to summarize the key aspects of AgNPs, including their characterization, properties, and recent advancements in the field of biogenic AgNP synthesis. Furthermore, the review highlights the potential applications of these nanoparticles in combating cancer.

Dissolution kinetics of copper oxide nanoparticles in presence of glyphosate

Recently CuO nanoparticles (n-CuO) have been proposed as an alternative method to deliver a Cu-based pesticide for controlling fungal infestations. With the concomitant use of glyphosate as an herbicide, the interactions between n-CuO and this strong ligand need to be assessed. We investigated the dissolution kinetics of n-CuO and bulk-CuO (b-CuO) particles in the presence of a commercial glyphosate product and compared it to oxalate, a natural ligand present in soil water. We performed experiments at concentration levels representative of the conditions under which n-CuO and glyphosate would be used (∼0.9 mg/L n-CuO and 50 μM of glyphosate). As tenorite (CuO) dissolution kinetics are known to be surface controlled, we determined that at pH 6.5, T ∼ 20 °C, using KNO3 as background electrolyte, the presence of glyphosate leads to a dissolution rate of 9.3 ± 0.7 ×10-3 h-1. In contrast, in absence of glyphosate, and under the same conditions, it is 2 orders of magnitude less: 8.9 ± 3.6 ×10-5 h-1. In a more complex multi-electrolyte aqueous solution the same effect is observed; glyphosate promotes the dissolution rates of n-CuO and b-CuO within the first 10 h of reaction by a factor of ∼2 to ∼15. In the simple KNO3 electrolyte, oxalate leads to dissolution rates of CuO about two times faster than glyphosate. However, the kinetic rates within the first 10 h of reaction are about the same for the two ligands when the reaction takes place in the multi-electrolyte solution as oxalate is mostly bound to Ca2+ and Mg2+.

How Synthesis of Algal Nanoparticles Affects Cancer Therapy? - A Complete Review of the Literature

The necessity to engineer sustainable nanomaterials for the environment and human health has recently increased. Due to their abundance, fast growth, easy cultivation, biocompatibility and richness of secondary metabolites, algae are valuable biological source for the green synthesis of nanoparticles (NPs). The aim of this review is to demonstrate the feasibility of using algal-based NPs for cancer treatment. Blue-green, brown, red and green micro- and macro-algae are the most commonly participating algae in the green synthesis of NPs. In this process, many algal bioactive compounds, such as proteins, carbohydrates, lipids, alkaloids, flavonoids and phenols, can catalyze the reduction of metal ions to NPs. In addition, many driving factors, including pH, temperature, duration, static conditions and substrate concentration, are involved to facilitate the green synthesis of algal-based NPs. Here, the biosynthesis, mechanisms and applications of algal-synthesized NPs in cancer therapy have been critically discussed. We also reviewed the effective role of algal synthesized NPs as anticancer treatment against human breast, colon and lung cancers and carcinoma.

Effect of particle size of nanoscale zero-valent copper on inorganic phosphorus adsorption-desorption in a volcanic ash soil

Zero-valent copper engineered nanoparticles (Cu-ENPs) released through unintentional or intentional actions into the agricultural soils can alter the availability of inorganic phosphorus (IP) to plants. In this study, we used adsorption-desorption experiments to evaluate the effect of particle size of 1% Cu-ENPs (25 nm and 40-60 nm) on IP availability in Santa Barbara (SB) volcanic ash soil. X-Ray Diffraction results showed that Cu-ENPs were formed by a mixture of Cu metallic and Cu oxides (Cu2O or/and CuO) species, while specific surface area values showed that Cu-ENPs/25 nm could form larger aggregate particles compared to Cu-ENPs/40-60 nm. The kinetic IP adsorption of SB soil without and with 1% Cu-ENPs (25 nm and 40-60 nm) followed the mechanism described by the pseudo-second-order (k2 = 0.45-1.13 x 10-3 kg mmol-1 min-1; r2 ≥ 0.999, and RSS ≤ 0.091) and Elovich (α = 14621.10-3136.20 mmol kg-1 min-1; r2 ≥ 0.984, and RSS ≤ 69) models. Thus, the rate-limiting step for IP adsorption in the studied systems was chemisorption on a heterogeneous surface. Adsorption equilibrium isotherms without Cu-ENPs were fitted well to the Freundlich model, while with 1% Cu-ENPs (25 nm and 40-60 nm), isotherms were described best by the Freundlich and/or Langmuir model. The IP relative adsorption capacity (KF) was higher with 1% Cu-ENPs/40-60 nm (KF = 110.41) than for 1% Cu-ENPs/25 nm (KF = 74.40) and for SB soil (KF = 48.17). This study showed that plausible IP retention mechanisms in the presence of 1% Cu-ENPs in SB soil were: i) ligand exchange, ii) electrostatic attraction, and iii) co-precipitate formation. The desorption study demonstrated that 1% Cu-ENPs/40-60 nm increased the affinity of IP in SB soil with a greater effect than 1% Cu-ENPs/25 nm. Thus, both the studied size ranges of Cu-ENPs could favor an accumulation of IP in volcanic ash soils.

Green and sustainable synthesis of nanomaterials: Recent advancements and limitations

Nanomaterials have been widely used in diverse fields of research such as engineering, biomedical science, energy, and environment. At present, chemical and physical methods are the main methods for large-scale synthesis of nanomaterials, but these methods have adverse effects on the environment, and health issues, consume more energy, and are expensive. The green synthesis of nanoparticles is a promising and environmentally friendly approach to producing materials with unique properties. Natural reagents such as herbs, bacteria, fungi, and agricultural waste are used in the green synthesis of nanomaterials instead of hazardous chemicals and reduce the carbon footprint of the synthesis process. Green synthesis of nanomaterials is highly beneficial compared to traditional methods due to its low cost, negligible pollution level, and safety for the environment and human health. Nanoparticles possess enhanced thermal and electrical conductivity, catalytic activity, and biocompatibility, making them highly attractive for a range of applications, including catalysis, energy storage, optics, biological labeling, and cancer therapy. This review article provides a comprehensive overview of recent advancements in the green synthesis routes of different types of nanomaterials, including metal oxide-based, inert metal-based, carbon-based, and composite-based nanoparticles. Moreover, we discuss the various applications of nanoparticles, emphasizing their potential to revolutionize fields such as medicine, electronics energy, and the environment. The factors affecting the green synthesis of nanomaterials, and their limitations are also pointed out to decide the direction of this research field, Overall, this paper highlights the importance of green synthesis in promoting sustainable development in various industries.

Aging of Copper Nanoparticles in the Marine Environment Regulates Toxicity for a Coastal Phytoplankton Species

Environmental conditions in aquatic ecosystems transform toxic chemicals over time, influencing their bioavailability and toxicity. Using an environmentally relevant methodology, we tested how exposure to seawater for 1-15 weeks influenced the accumulation and toxicity of copper nanoparticles (nano-Cu) in a marine phytoplankton species. Nano-Cu rapidly agglomerated in seawater and then decreased in size due to Cu dissolution. Dissolution rates declined during weeks 1-4 and remained low until 15 weeks, when the large agglomerates that had formed began to rapidly dissolve again. Marine phytoplankton species were exposed for 5-day periods to nano-Cu aged from 1 to 15 weeks at concentrations from 0.01 to 20 ppm. Toxicity to phytoplankton, measured as change in population growth rate, decreased significantly with particle aging from 0 to 4 weeks but increased substantially in the 15-week treatment due apparently to elevated Cu dissolution of reagglomerated particles. Results indicate that the transformation, fate, and toxicity of nano-Cu in marine ecosystems are influenced by a highly dynamic physicochemical aging process.

Foliar enrichment of copper oxide nanoparticles promotes biomass, photosynthetic pigments, and commercially valuable secondary metabolites and essential oils in dragonhead (Dracocephalum moldavica L.) under semi-arid conditions

High alkaline and low organic carbon hinder micronutrients, such as copper (Cu), bioavailability in (semi-) arid soils, affecting plant nutrient quality and productivity. This study aimed at investigating the potential beneficial effects of foliar Cu oxide nanoparticles (CuONPs) and conventional chelated-Cu applications (0-400 mg Cu/L) on the biomass, physiological biomarkers of plant productivity and oxidative stress, Cu bioaugmentation, and essential oils and secondary metabolites in dragonhead (Dracocephalum moldavica [L.]) grown in Cu-limited alkaline soil in semi-arid condition. Employing a randomized complete block design with three replicates, two different sources of Cu (CuONPs and chelated-Cu), and a wide range of Cu concentrations (0, 40, 80, 160, and 400 mg Cu/L), plants were foliarly treated at day-60 and day-74. At day-120, plants were harvested at the end of the flowering stage. Results showed shoot Cu bioaccumulation, flavonoids and anthocyanin increased in a dose-dependent manner for both Cu compounds, but the beneficial effects were significantly higher with CuONPs compared to chelated-Cu treatments. Further, shoot biomass (23 %), photosynthetic pigments (chlorophyll-a and chlorophyll-b; 77 and 123 %, respectively), and essential oil content and yield (70 and 104 %, respectively) increased significantly with foliar application of 80 mg/L CuONPs compared to equivalent concentration of chelated-Cu, suggesting an optimal threshold beyond which toxicity was observed. Likewise, commercially important secondary metabolites' yield (such as geranyl acetate, geranial, neral, and geraniol) was higher with 80 mg/L CuONPs compared to 160 mg/L chelated-Cu (2.3, 0.5, 2.5, and 7.1 %, respectively). TEM analyses of leaf ultrastructure revealed altered cellular organelles for both compounds at 400 mg/L, corroborating the results of oxidative stress response (malondialdehyde and H2O2). In conclusion, these findings indicate significantly higher efficacy of CuONPs, with an optimal threshold of 80 mg/L, in promoting essential oil and bioactive compound yield in dragonhead and may pave a path for the use of nano-Cu as a sustainable fertilizer promoting agricultural production in semi-arid soils that are micronutrient Cu deficient.

Effects of interactions between natural organic matter and aquatic organism degradation products on the transformation and dissolution of cobalt and nickel-based nanoparticles in synthetic freshwater

Expanding applications and production of engineered nanoparticles lead to an increased risk for their environmental dispersion. Systematic knowledge of surface transformation and dissolution of nanoparticles is essential for risk assessment and regulation establishment. Such aspects of Co- and Ni-based nanoparticles including metals, oxides, and solution combustion synthesized metal nanoparticles (metal cores with carbon shells) were investigated upon environmental interaction with organic matter, simulated by natural organic matter (NOM) and degradation products from zooplankton and algae (eco-corona biomolecules, EC) in freshwater (FW). The presence of NOM and EC in FW results in negative surface charges of the nanoparticles reduces the extent of nanoparticles agglomeration, and increases concentration, mainly due to the surface adsorption of carboxylate groups of the organic matter. The dissolution of the Co-based nanoparticles was for all conditions (FW, FW with NOM or EC) higher than the Ni-based, except for Co₃O₄ being nearly non-soluble. The surface transformation and dissolution of nanoparticles are highly exposure and time-dependent, and surface- and environment specific. Therefore, no general correlation was observed between dissolution and, particle types, surface conditions, or EC/NOM adsorption. This underlines the importance of thorough investigations of nanoparticles adsorption/desorption, degradation, and exposure scenarios for developing regulatory relevant protocols and guidelines.

Simulation of the Environmental Fate and Transformation of Nano Copper Oxide in a Freshwater Environment

Production of engineered nanomaterials (ENMs) has rapidly increased, yet uncertainty exists regarding the full extent of their environmental implications. This study investigates the fate, transformation, and speciation of nano copper oxide (nanoCuO) released into Lake Waccamaw, North Carolina, over 101 years. Using the Advanced Toxicant module of the Water Quality Analysis Simulation Program (WASP8), we assessed the accumulation and mass proportions of nanoCuO and Cu²⁺ (the product of nanoCuO's dissolution) in the water column and sediments. Our simulations suggest that when nanoCuO is released into Lake Waccamaw, the highest concentrations of both nanoCuO and Cu²⁺ are found in the surface sediments, followed by the subsurface sediments and the water column. Simulating different heteroaggregation attachment efficiencies of nanoCuO suggested that increases in attachment efficiency increased nanoCuO concentrations and mass proportions in the water column and sediments, while Cu²⁺ exhibited the opposite trends. After 101 years, most nanoCuO in the sediments was attached to particulate organic matter and clay particles at all attachment efficiencies, while low attachment efficiency slowed aggregate formation in the water column. Our results highlight the influence that heteroaggregation has on the behavior of nanoCuO inputs and suggest the potential for legacy contamination of nanoCuO and Cu²⁺ in sediments.

Iron Speciation in Respirable Particulate Matter and Implications for Human Health

Particulate matter (PM) air pollution poses a major global health risk, but the role of iron (Fe) is not clearly defined because chemistry at the particle-cell interface is often not considered. Detailed spectromicroscopy characterizations of PM_2.5 samples from the San Joaquin Valley, CA identified major Fe-bearing components and estimated their relative proportions. Iron in ambient PM_2.5 was present in spatially and temporally variable mixtures, mostly as Fe(III) oxides and phyllosilicates, but with significant fractions of metallic iron (Fe(0)), Fe(II,III) oxide, and Fe(III) bonded to organic carbon. Fe(0) was present as aggregated, nm-sized particles that comprised up to ∼30% of the Fe spectral fraction. Mixtures reflect anthropogenic and geogenic particles subjected to environmental weathering, but reduced Fe in PM originates from anthropogenic sources, likely as abrasion products. Possible mechanistic pathways involving Fe(0) particles and mixtures of Fe(II) and Fe(III) surface species may generate hydrogen peroxide and oxygen-centered radical species (hydroxyl, hydroperoxyl, or superoxide) in Fenton-type reactions. From a health perspective, PM mixtures with reduced and oxidized Fe will have a disproportionate effect in cellular response after inhalation because of their tendency to shuttle electrons and produce oxidants and electrophiles that induce inflammation and oxidative stress.

Influence of copper treatment on bioaccumulation, survival, behavior, and fecundity in the fruit fly Drosophila melanogaster: Toxicity of copper oxide nanoparticles differ from dissolved copper

Copper oxide (CuO) NPs are widely used and subsequently released into terrestrial ecosystems. In the present study, bioaccumulation and effects of CuO NPs and dissolved Cu was examined in the fruit fly Drosophila melanogaster after 7 and 10 days dietary exposure at concentrations ranging between 0.09 and 1.2 mg Cu ml^-1 for dissolved Cu and between 0.2 and 11 mg Cu ml^-1 for CuO NPs. Both Cu forms were bioaccumulated and affected survival and climbing in flies, but not egg-to-adult development. Dissolved Cu caused higher mortality than CuO NPs (CuO NPs 10-days LC₅₀ was 2 times higher), whereas NPs affected climbing and decreased the number of eggs laid per female, potentially affecting fruit fly population size in terrestrial environments. Thus, the study indicates that CuO NPs might cause effects that are different from dissolved Cu due to differences in the mechanism of uptake or toxicity. Therefore, we need to consider relevant sublethal endpoints when assessing these CuO NPs to ensure that we do not overlook long-term effects.

Influence of Aging on Bioaccumulation and Toxicity of Copper Oxide Nanoparticles and Dissolved Copper in the Sediment-Dwelling Oligochaete Tubifex tubifex: A Long-Term Study Using a Stable Copper Isotope

For engineered metal nanoparticles (NPs), such as copper oxide (CuO) NPs, the sediment is recognized as a major compartment for NP accumulation. Sediment-dwelling organisms, such as the worm Tubifex tubifex, will be at particular risk of metal and metal NP exposure. However, a range of complex transformation processes in the sediment affects NP bioavailability and toxicity as the contamination ages. The objective of this study was to examine bioaccumulation and adverse effects of CuO NPs in T. tubifex compared to dissolved Cu (administered as CuCl₂) and the influence of aging of spiked sediment. This was done in a 28-day exposure experiment with T. tubifex incubated in clean sediment or freshly spiked sediment with different concentrations of dissolved Cu (up to 230 μg g⁻¹ dw) or CuO NPs (up to 40 μg g⁻¹ dw). The experiment was repeated with the same sediments after it had been aged for 2 years. To obtain a distinct isotopic signature compared to background Cu, both Cu forms were based on the stable isotope ⁶⁵Cu (>99%). The 28-day exposure to sediment-associated dissolved ⁶⁵Cu and ⁶⁵CuO NPs resulted in a clear concentration-dependent increase in the T. tubifex⁶⁵Cu body burden. However, despite the elevated ⁶⁵Cu body burdens in exposed worms, limited adverse effects were observed in either of the two experiments (e.g., above 80% survival in all treatments, low or no effects on the growth rate, feeding rate, and reproduction). Organisms exposed to aged sediments had lower body burdens of ⁶⁵Cu than those exposed to freshly spiked sediments and we suggest that aging decreases the bioavailability of both ⁶⁵Cu forms. In this study, the use of a stable isotope made it possible to use environmentally realistic Cu concentrations and, at the same time, differentiate between newly accumulated ⁶⁵Cu and background Cu in experimental samples despite the high background Cu concentrations in sediment and T. tubifex tissue. Realistic exposure concentrations and aging of NPs should preferably be included in future studies to increase environmental realism to accurately predict the environmental risk of metal NPs.

A critical review of the environmental impacts of manufactured nano-objects on earthworm species

The presence of manufactured nano-objects (MNOs) in various consumer or their (future large-scale) use as nanoagrochemical have increased with the rapid development of nanotechnology and therefore, concerns associated with its possible ecotoxicological effects are also arising. MNOs are releasing along the product life cycle, consequently accumulating in soils and other environmental matrices, and potentially leading to adverse effects on soil biota and their associated processes. Earthworms, of the group of Oligochaetes, are an ecologically significant group of organisms and play an important role in soil remediation, as well as acting as a potential vector for trophic transfer of MNOs through the food chain. This review presents a comprehensive and critical overview of toxic effects of MNOs on earthworms in soil system. We reviewed pathways of MNOs in agriculture soil environment with its expected production, release, and bioaccumulation. Furthermore, we thoroughly examined scientific literature from last ten years and critically evaluated the potential ecotoxicity of 16 different metal oxide or carbon-based MNO types. Various adverse effects on the different earthworm life stages have been reported, including reduction in growth rate, changes in biochemical and molecular markers, reproduction and survival rate. Importantly, this literature review reveals the scarcity of long-term toxicological data needed to actually characterize MNOs risks, as well as an understanding of mechanisms causing toxicity to earthworm species. This review sheds light on this knowledge gap as investigating bio-nano interplay in soil environment improves our major understanding for safer applications of MNOs in the agriculture environment.

Interaction of different-sized ZnO nanoparticles with maize (Zea mays): Accumulation, biotransformation and phytotoxicity

This study aimed to investigate the biotransformation of ZnO nanoparticles (NPs) in maize grown in hydroponics for ecotoxicity assessment. Maize seedlings grown for 14 days were exposed to a solution of 9 nm ZnO NPs, 40 nm ZnO NPs, and ZnSO₄ at a Zn concentration of 300 mg L^-1 for 1, 3, and 7 days, respectively. The results of in-situ Zn distribution in maize (Zea mays) showed that 9 nm ZnO NPs could quickly enter the roots of maize and reach the center column transport system of the stem. The results of transmission electron microscopy combined with energy dispersive X-ray spectroscopy revealed that ZnO NPs were accumulated in the vacuoles of the roots, and then transformed and transported through vesicles. Simulated studies showed that low pH (5.6) played a critical role in the transformation of ZnO NPs, and organic acids (K_f = 10^11.4) could promote particle dissolution. Visual MINTEQ software simulated the species of Zn after the entry of ZnO NPs or Zn²⁺ into plants and found that the species of Zn was mainly Zn²⁺ when the Zn content of plants reached 200-300 ppm. Considering that the lowest Zn content of the roots in treatments was 1920 mg kg^-1, combination of the result analysis of root effects showed that the toxicity of roots in most treatments had a direct relationship with Zn²⁺. However, treatment with 9 nm ZnO NPs exhibited significantly higher toxicity than ZnSO₄ treatment on day 1 when the Zn²⁺ concentration difference was not significant, which was mainly due to the large amount of ZnO NPs deposited in the roots. To the authors' knowledge, this study was the first to confirm the process of biotransformation and explore the factors affecting the toxicity of ZnO NPs in depth.

Differential bioaccumulations and ecotoxicological impacts of metal-oxide nanoparticles, bulk materials, and metal-ions in cucumbers grown in sandy clay loam soil

Expanding applications of metal-oxide nanoparticles (NPs) and increased environmental deposition of NPs followed by their interactions with edible crops threaten yields. This study demonstrates the effects of aging (45 days in soil) of four NPs (ZnO, CuO, Al₂O₃, TiO₂; 3.9-34 nm) and their corresponding metal oxide bulk particles (BPs; 144-586 nm) on cucumbers (Cucumis sativus L.) cultivated in sandy-clay-loam field soil and compares these with the phytotoxic effects of readily soluble metal salts (Zn²⁺, Cu²⁺, and Al³⁺). Data revealed the cell-to-cell translocations of NPs, their attachments to outer and inner cell surfaces, nuclear membranes, and vacuoles, and their upward movements to aerial parts. Metal bioaccumulations in cucumbers were found in the order: (i) ZnO-NPs > ZnO-BPs > Zn²⁺, (ii) CuO-NPs > CuO-BPs > Cu²⁺, (iii) Al³⁺> Al₂O₃-NPs > Al₂O₃-BPs and (iv) TiO₂-NPs > TiO₂-BPs. Aging of NPs in soil for 45 days significantly enhanced metal uptake (P ≤ 0.05), for instance aged ZnO-NPs at 1 g kg^-1 increased the uptake by 20.7 % over non-aged ZnO-NPs. Metal uptakes inhibited root (RDW) and shoot (SDW) dry weight accumulations. For Cu species, maximum negative impact (%) was exhibited by Cu²⁺ (RDW:SDW = 94:65) followed by CuO-NPs (RDW:SDW = 78:34) and CuO-BPs (RDW:SDW = 27:22). Aging of NPs/BPs at 1-4 g kg^-1 further enhanced the toxic impact of tested materials on biomass accumulations and chlorophyll formation. NPs also induced membrane damage of root tissues and enhanced levels of antioxidant enzymes. The results of this study suggest that care is required when aged metal-oxide NPs of both essential (Zn and Cu) and non-essential (Al and Ti) metals interact with cucumber plants, especially, when they are used for agricultural purposes.

Ion compositions in artificial media control the impact of humic acid on colloidal behaviour, dissolution and speciation of CuO-NP

The toxicity of copper oxide nanoparticles (CuO-NP) strongly depends on their interactions with the surrounding environment, impacting their dissolution and colloidal stability. This behaviour is studied quite extensively for simplified electrolytes, but information on the behaviour of CuO-NP in more complex artificial media are lacking. In our study, we analysed the colloidal behaviour and considered the speciation of CuO-NP in pure water and three artificial media of different complexity which are used in ecotoxicology. Measurements were done over 7 days in the absence and presence of humic acid (HA) as a model organic molecule. In pure water, the addition of HA lowered the zeta potential from +11 to -41 mV, while in all artificial media, it stayed constantly at about -20 mV. The hydrodynamic diameter of CuO-NP remained unaffected by HA in pure water and seawater, while in porewater and especially in freshwater, HA suppressed strong agglomeration. In pure water, HA strongly increased dissolution to the highest observed value (3% of total Cu), while HA reduced dissolution in all artificial media. Speciation calculations revealed that cations from the media competed with Cu from the NP surface for complexing sites of the HA. This competition may have caused the reduced dissolution in the presence of ions. Furthermore, speciation calculations also suggest that ion composition drove agglomeration behaviour rather than ion concentration: agglomeration was high when divalent cations where the major interaction partner and dominant in relative terms. HA may have reduced the relative dominance and thus altered the agglomeration, aligning it in all media. Summarizing, ion composition and the presence of HA strongly drive the dissolution and agglomeration of CuO-NP in artificial media, consequently, analysing complexation can help to predict environmental behaviour and toxicity.

Copper Oxide Nanoparticle-Induced Acute Inflammatory Response and Injury in Murine Lung Is Ameliorated by Synthetic Secoisolariciresinol Diglucoside (LGM2605)

Metal-oxide nanoparticles (MO-NPs), such as the highly bioreactive copper-based nanoparticles (CuO-NPs), are widely used in manufacturing of hundreds of commercial products. Epidemiological studies correlated levels of nanoparticles in ambient air with a significant increase in lung disease. CuO-NPs, specifically, were among the most potent in a set of metal-oxides and carbons studied in parallel regarding DNA damage and cytotoxicity. Despite advances in nanotoxicology research and the characterization of their toxicity, the exact mechanism(s) of toxicity are yet to be defined. We identified chlorination toxicity as a damaging consequence of inflammation and myeloperoxidase (MPO) activation, resulting in macromolecular damage and cell damage/death. We hypothesized that the inhalation of CuO-NPs elicits an inflammatory response resulting in chlorination damage in cells and lung tissues. We further tested the protective action of LGM2605, a synthetic small molecule with known scavenging properties for reactive oxygen species (ROS), but most importantly, for active chlorine species (ACS) and an inhibitor of MPO. CuO-NPs (15 µg/bolus) were instilled intranasally in mice and the kinetics of the inflammatory response in lungs was evaluated 1, 3, and 7 days later. Evaluation of the protective action of LGM2605 was performed at 24 h post-challenge, which was selected as the peak acute inflammatory response to CuO-NP. LGM2605 was given daily via gavage to mice starting 2 days prior to the time of the insult (100 mg/kg). CuO-NPs induced a significant inflammatory influx, inflammasome-relevant cytokine release, and chlorination damage in mouse lungs, which was mitigated by the action of LGM2605. Preventive action of LGM2605 ameliorated the adverse effects of CuO-NP in lung.

Comparison of the dynamic responses of different anammox granules to copper nanoparticle stress: Antibiotic exposure history made a difference

Two types of anaerobic ammonium oxidation (anammox) seed sludge were selected to evaluate their responses to copper nanoparticles (CuNPs) exposure. Antibiotic-exposed anammox granules (R₁) were more likely to be inhibited by 5.0 mg L^-1 CuNPs than the normal anammox granules (C₁). The nitrogen removal efficiency (NRE) of C₁ decreased by 9.00% after two weeks of exposure to CuNPs, whereas that of R₁ decreased by 20.32%. Simultaneously, the abundance of Candidatus. Kuenenia decreased by 27.65% and 36.02% in C₁ and R₁ under CuNPs stress conditions, respectively. Generally, R₁ was more susceptible to CuNPs than C₁. The correlation analysis indicated that the horizontal transfer of antibiotic resistance genes and copA triggered by intI1 facilitated the generation of multiresistance in the anammox process. Moreover, the potential multiresistance mechanism of anammox bacteria was hypothesized based on previous results. The results will generate new ideas for the treatment of complex wastewater using the anammox process.

The impacts of metal-based engineered nanomaterial mixtures on microbial systems: A review

The last decade has witnessed tremendous growth in the commercial use of metal-based engineered nanomaterials (ENMs) for a wide range of products and processes. Consequently, direct and indirect release into environmental systems may no longer be considered negligible or insignificant. Yet, there is an active debate as to whether there are real risks to human or ecological health with environmental exposure to ENMs. Previous research has focused primarily on the acute effects of individual ENMs using pure cultures under controlled laboratory environments, which may not accurately reveal the ecological impacts of ENMs under real environmental conditions. The goal of this review is to assess our current understanding of ENM effects as we move from exposure of single to multiple ENMs or microbial species. For instance, are ENMs' impacts on microbial communities predicted by their intrinsic physical or chemical characteristics or their effects on single microbial populations; how do chronic ENM interactions compare to acute toxicity; does behavior under simplified laboratory conditions reflect that in environmental media; finally, is biological stress modified by interactions in ENM mixtures relative to that of individual ENM? This review summarizes key findings and our evolving understanding of the ecological effects of ENMs under complex environmental conditions on microbial systems, identifies the gaps in our current knowledge, and indicates the direction of future research.

Dissolution of copper oxide nanoparticles is controlled by soil solution pH, dissolved organic matter, and particle specific surface area

Dissolution is the primary process affecting the bioavailability and toxicity of nanoscale copper oxide (nano-CuO) to plants and soil organisms. In this study, particle morphology, organic acid, and soil properties were considered to understand the dissolution characteristics of nano-CuO in soil solutions. The results showed that the copper ions (Cu²⁺) released from spherical nano-CuO (CuO NPs), tubular nano-CuO (CuO NTs), and spherical microsized CuO (CuO MPs) in the ten soil solutions were 26.6-4194.0 μg/L, 4.90-217.1 μg/L, and 10.8-326.0 μg/L, respectively. The concentration of Cu²⁺ was negatively correlated with the pH of the soil solution and positively correlated with the contents of dissolved organic carbon (DOC), aluminum, and manganese. Multivariate stepwise regression analysis indicated that the dissolution of CuO NPs could be well predicted by pH and DOC contents of the soil solutions. In the GD soil solution (acidic), 4- and 8-fold of the DOC content amendments significantly promoted the dissolution of the three sizes of CuOs, resulting in an increase of Cu²⁺ 4.55-11.3 and 5.67-16.2 times, respectively. In the CQ soil solution (neutral), 8-fold DOC amendments increase the release of Cu²⁺ 2.13-16.6 times. While in the SD soil solution (alkaline), promoting effect on the dissolution was only observed for nano-CuOs, with Cu²⁺ elevated by factors of 1.56-4.64 and 1.38-4.48. The amendments of Al³⁺ and Mn²⁺ in soil solution increased the amounts of Cu²⁺ 1.13-4.80 and 1.02-1.46 times in the GD soil solution. In comparison, no significant promoting effects were observed in CQ and SD soil solutions due to their stronger buffering capacities. These findings offer insight into the dissolution behavior of nano-CuOs in soils and be helpful to evaluate their environmental risks.

Plant-Based Biosynthesis of Copper/Copper Oxide Nanoparticles: An Update on Their Applications in Biomedicine, Mechanisms, and Toxicity

Plants are rich in phytoconstituent biomolecules that served as a good source of medicine. More recently, they have been employed in synthesizing metal/metal oxide nanoparticles (NPs) due to their capping and reducing properties. This green synthesis approach is environmentally friendly and allows the production of the desired NPs in different sizes and shapes by manipulating parameters during the synthesis process. The most commonly used metals and oxides are gold (Au), silver (Ag), and copper (Cu). Among these, Cu is a relatively low-cost metal that is more cost-effective than Au and Ag. In this review, we present an overview and current update of plant-mediated Cu/copper oxide (CuO) NPs, including their synthesis, medicinal applications, and mechanisms. Furthermore, the toxic effects of these NPs and their efficacy compared to commercial NPs are reviewed. This review provides an insight into the potential of developing plant-based Cu/CuO NPs as a therapeutic agent for various diseases in the future.

Dietary uptake and effects of copper in Sticklebacks at environmentally relevant exposures utilizing stable isotope-labeled 65CuCl2 and 65CuO NPs

Copper oxide nanoparticles (CuO NPs) accumulating in sediment can be taken up by invertebrates that serve as prey for fish. Thus, it is likely that the latter are exposed to CuO NPs via the gut. However, to this day it is unknown if CuO NPs can be taken up via the gastrointestinal tract and if and in which tissues/organs they accumulate. To address this knowledge gap, we synthesized CuO NPs enriched in the stable isotope ⁶⁵Cu and incorporated them at low concentration (5 μg ⁶⁵Cu g^-1 ww food) into a practical diet prepared from worm homogenate, which was then fed to Three-spined Stickleback (Gasterosteus aculeatus) for 16 days. For comparison, fish were exposed to a diet spiked with a ⁶⁵CuCl₂ solution. Background Cu and newly taken up ⁶⁵Cu in fish tissues/organs including gill, stomach, intestine, liver, spleen, gonad and carcass and feces were quantified by ICP-MS. In addition, expression levels of genes encoding for proteins related to Cu uptake, detoxification and toxicity (ctr-1, gcl, gr, gpx, sod-1, cat, mta and zo-1) were measured in selected tissues using RT-qPCR. The obtained results showed that feces of fish fed ⁶⁵CuO NP-spiked diet contained important amounts of ⁶⁵Cu. Furthermore, there was no significant accumulation of ⁶⁵Cu in any of the analyzed internal organs, though ⁶⁵Cu levels were slightly elevated in liver. No significant modulation in gene expression was measured in fish exposed to ⁶⁵CuO NP-spiked diet, except for metallothionein, which was significantly upregulated in intestinal tissue compared to control fish. Altogether, our results suggests that dietary absorption efficiency of CuO NPs, their uptake across the gastrointestinal barrier into the organism, and effects on Cu-related genes is limited at low, environmentally relevant exposure doses (0.2 μg ⁶⁵Cu ^-1 fish ww day^-1).

Application of Natural Deep Eutectic Solvents for the metal nanoparticles extraction from plant tissue

The study aimed to use Natural Deep Eutectic Solvents (NADES) as an extractant of metal oxide NPs from plant material. The plant chosen for the study was radish after exposure, growing on media containing: copper(II) oxide, cerium(IV) oxide, and titanium(IV) oxide. The first step of the study was to investigate the influence of NADES on NPs. In the second step, selected NADES solvents were used as extractants of NPs present in radish after exposure. Single-particle Inductively Coupled Plasma Mass Spectrometry technique (SP-ICP-MS) was used to determine the number and size of NPs. As a result of the research, it was found that copper(II) oxide NPs, regardless of the solvent used, is not present in the extract. Only the ionic form of the element was present in the solution. Higher sized cerium(IV) oxide NPs were accumulated in the root, while smaller sized ones were found in radish leaves. The titanium(IV) oxide NPs were agglomerated and were present in a small amount in radish leaves, accumulating mainly in the root. Finally, it can be concluded that NADES allows the extraction of metal oxide NPs from the plant material.

Nanocolloids, but Not Humic Acids, Augment the Phytotoxicity of Single-Layer Molybdenum Disulfide Nanosheets

Engineered nanomaterials (ENMs), especially transition metal dichalcogenide (TMDC), have received great attention in recent years due to their advantageous properties and applications in various fields and are inevitably released into the environment during their life cycle. However, the effect of natural nanocolloids, widely distributed in the aquatic environment, on the environmental transformation and ecotoxicity of ENMs remains largely unknown. In this study, the effects of natural nanocolloids were compared to humic acid on the environmental transformation and ecotoxicity of single-layer molybdenum disulfide (SLMoS₂), a representative TMDC. SLMoS₂ with nanocolloids or humic acid (HA) enhanced their dispersion and Mo ion release in deionized water. Nanocolloids induced growth inhibition, reactive oxygen species (ROS) elevation, and cell permeability. Low-toxicity SLMoS₂ combined with nanocolloids will enhance the above adverse effects. SLMoS₂-nanocolloids induced serious damage (cell distortion and deformation), SLMoS₂ internalization, and metabolic perturbation on Chlorella vulgaris (C. vulgaris). In contrast, the addition of HA induced the growth promotion and lower ROS level, inhibited the internalization of SLMoS₂, and mitigated metabolic perturbation on C. vulgaris. This work provides insights into the effect of natural nanocolloids on the behaviors and biological risks of ENMs in aquatic environments, deserving substantial future attention.

Ageing alters the physicochemical properties of silver nanoparticles and consequently compromises their acute toxicity in mammals

Despite numerous investigations into AgNP-induced toxicity, little has been taken into consideration the potential health impacts of aged AgNPs in comparison to fresh AgNPs. In the current study, we scrutinized the potential effects of aged AgNPs in animals. We first found that AgNPs underwent morphological transformations after natural ageing in aqueous solution upon exposure to air and sunlight for 9 days, as characterized by significant aggregation with increase of particle size approximately by 2 fold. Meanwhile, dissolved Ag ions from aged AgNPs increased by 33% compared to fresh AgNPs. Strikingly, the acute exposure results showed that aged AgNPs induced lower toxicity in mice relative to fresh AgNPs. Aged AgNPs caused milder local inflammation in the peritoneal cavity of mice, as evidenced by 63% reduction of tumor necrosis factor α (TNF-α) than that induced by fresh AgNPs. The deposition mass of aged AgNPs in the liver, spleen, lung and kidney was diminished by 69%, 39%, 83% and 40%, respectively, compared to the distribution profiles in response to fresh AgNPs. Whereby, milder splenic hyperemia was observed, and no significant hepatoxicity was found. Additionally, aged AgNPs provoked milder increase of periphery leukocytes and malondialdehyde (MDA) in mice in comparison to fresh AgNPs. Taken together, this study unraveled that the ageing process elicited remarkable alterations to physicochemical properties and toxic effects as well. This study would provide new insights into the potential health impacts of AgNPs under transformation-determined exposure scenarios.

Transformation pathways and fate of engineered nanoparticles (ENPs) in distinct interactive environmental compartments: A review

The ever increasing production and use of nano-enabled commercial products release the massive amount of engineered nanoparticles (ENPs) in the environment. An increasing number of recent studies have shown the toxic effects of ENPs on different organisms, raising concerns over the nano-pollutants behavior and fate in the various environmental compartments. After the release of ENPs in the environment, ENPs interact with various components of the environment and undergoes dynamic transformation processes. This review focus on ENPs transformations in the various environmental compartments. The transformation processes of ENPs are interrelated to multiple environmental aspects. Physical, chemical and biological processes such as the homo- or hetero-agglomeration, dissolution/sedimentation, adsorption, oxidation, reduction, sulfidation, photochemically and biologically mediated reactions mainly occur in the environment consequently changes the mobility and bioavailability of ENPs. Physico-chemical characteristics of ENPs (particle size, surface area, zeta potential/surface charge, colloidal stability, and core-shell composition) and environmental conditions (pH, ionic strength, organic and inorganic colloids, temperature, etc.) are the most important parameters which regulated the ENPs environmental transformations. Meanwhile, in the environment, organisms encountered multiple transformed ENPs rather than the pristine nanomaterials due to their interactions with various environmental materials and other pollutants. Thus it is the utmost importance to study the behavior of transformed ENPs to understand their environmental fate, bioavailability, and mode of toxicity.

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.

Assessment of Cu and CuO nanoparticle ecological responses using laboratory small-scale microcosms

Copper based nanoparticles (NPs) are used extensively in industrial and commercial products as sensors, catalysts, surfactants, antimicrobials, and for other purposes. The high production volume and increasing use of copper-based NPs make their ecological risk a concern. Commonly used copper-based NPs are composed of metallic copper or copper oxide (Cu and CuO NPs); however, their environmental toxicity can vary dramatically depending on their physico-chemical properties, such as dissolution, aggregation behavior, and the generation of reactive oxygen species. Here, we investigated the NP dissolution, organismal uptake and aquatic toxicity of Cu and CuO NPs at 0, 0.1, 1, 5 or 10 mg Cu/L using a previously developed multi-species microcosm. This 5-day microcosm assay was comprised of C. reinhardtti, E. coli, D. magna, and D. rerio. We hypothesized that Cu and CuO NPs can elicit differential toxicity to the organisms due to alterations in particle dissolution and variations in organismal uptake. The actual concentrations of dissolved Cu released from the NPs were compared to ionic copper controls (CuCl₂) at the same concentrations to determine the relative contribution of particulate and dissolved Cu on organism uptake and toxicity. We found that both NPs had higher uptake in D. magna and zebrafish than equivalent ionic exposures, suggesting that both Cu-based NPs are taken up by organisms. Cu NP exposures significantly inhibited algal growth rate, D. magna survival, and zebrafish hatching while exposure to equivalent concentrations of CuCl₂ (dissolved Cu fraction) and CuO NPs did not. This indicates that Cu NPs themselves likely elicited a particle-specific mechanism of toxicity to the test organisms, or a combination effect from ionic Cu and the Cu NPs. Overall, this work was the first study to utilize a small-scale rapid assay designed to evaluate the fate and ecotoxicological impacts of Cu and CuO NPs in a mixed aquatic community.

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.

Influence of water chemistry on colloid-size Cu-based pesticides particles: A case of Cu(OH)2 commercial fungicide/bactericide

The intensive, widespread, and ever-increasing applications of Cu-based pesticides in agriculture could potentially increase environmental exposures via different routes. Unlike ionic/bulk forms, the fate, transport, and toxicity of colloid-size Cu-based pesticides are not well studied. This paper provides evaluation outcomes of granule and dispersion characterizations, stability, and dissolution of colloid-size particles of Cu(OH)₂ commercial pesticide product at a range of water chemistry. The evaluated product contained about 35% weight of metallic Cu equivalent and Cu(OH)₂ particles with sizes < 1 μm of which a fraction of nanoscale particles exist. The presence of Ca²⁺ at ionic strengths of >0.01 M and 0.001-0.2 M significantly influenced (p < 0.001) particle size (PS) and ζ-potential values, respectively at all investigated pH values. Cu dissolution at pH 5.5 was significant (p < 0.001) and exceeded Cu dissolutions at pH 7.0 by 87-90% and at pH 8.5 by 87-95% in all dispersions. The order of Cu dissolution was pH 5.5 > pH 7.0 > pH 8.5 in all dispersions. Cu dissolution was relatively reduced by 53% by increasing HA from 0 to 5 mg L^-1 and enhanced by 55% by increasing HA from 5 to 15 mg L^-1, however, the overall Cu dissolution was decreased by 27% by increasing HA from 0 to 15 mg L^-1. Thus, HAs reduced the dissolution of Cu at pH < 7. The findings provide an insight into how water chemistry influences the fate and transport of colloid-size Cu-based pesticides particles.

Effects of Precursor Concentration in Solvent and Nanomaterials Room Temperature Aging on the Growth Morphology and Surface Characteristics of Ni–NiO Nanocatalysts Produced by Dendrites Combustion during SCS

The morphology and surface characteristics of SCS(Solution Combustion Synthesis)-derived Ni–NiO nanocatalysts were studied. The ΤΕΜ results highlighted that the nanomaterial’s microstructure was modified by changing the reactants’ concentrations. The dendrites’ growth conditions were the main factors responsible for the observed changes in the nanomaterials’ crystallite size. Infrared camera measurements demonstrated a new type of combustion through dendrites. The XPS analysis revealed that the NiO structure resulted in the bridging of the oxygen structure that acted as an inhibitor of hydrogen adsorption on the catalytic surface and, consequently, the activity reduction. The RF-IGC indicated three different kinds of active sites with different energies of adsorption on the fresh catalyst and only one type on the aged catalyst. Aging of the nanomaterial was associated with changes in the microstructure of its surface by a gradual change in the chemical composition of the active centers.

Maize (Zea mays L.) root exudates modify the surface chemistry of CuO nanoparticles: Altered aggregation, dissolution and toxicity

Copper oxide nanoparticles (CuO NPs), as an antimicrobial nanomaterial, have found many applications in agriculture. Ubiquitous and complex root exudates (RE) in the plant root zone motivates the determination of how specific components of RE interact with CuO NPs. This work aims to reveal the role of maize (Zea mays L.)-derived RE and their components on the aggregation and dissolution of CuO NPs in the rhizosphere. We observed that RE significantly inhibited the aggregation of CuO NPs regardless of ionic strength and electrolyte type. In the presence of RE, the CCC of CuO NPs in NaCl shifted from 30 to 125 mM and the value in CaCl₂ shifted from 4 to 20 mM. Furthermore, this inhibition was correlated with molecular weight (MW) of RE fractions. Higher MW fraction (>10 kDa) reduced the aggregation most. We also discovered that RE significantly promoted the dissolution of CuO NPs and lower MW fraction (<3 kDa) RE mainly contributed to this process. Additionally, phytotoxicity of CuO NPs in the presence of RE and different fractions of RE was evaluated. The addition of 20 mg/L RE reduced the seedlings growth rate to 1.89% after 7 days exposure to 25 mg/L CuO NPs, which were significantly lower than the control group (4.82%). Notably, Cu accumulation in plant root tissues was significantly enhanced by 20 mg/L RE. This study provides useful insights into the interactions between RE and CuO NPs, which is of significance for the safe use of CuO NPs-based antimicrobial products in agricultural production.

The Toxicity of Nonaged and Aged Coated Silver Nanoparticles to Freshwater Alga Raphidocelis subcapitata

The transformation of coated silver nanoparticles (AgNPs) and their impacts on aquatic organisms require further study. The present study investigated the role of aging on the transformation of differently coated AgNPs and their sublethal effects on the freshwater alga Raphidocelis subcapitata. The stability of AgNPs was evaluated over 32 d, and the results indicated that transformation of AgNPs occurred during the incubation; however, coating-specific effects were observed. Fresh AgNPs increased reactive oxygen species (ROS) formation, whereas aged AgNPs induced excessive ROS generation compared with their fresh counterparts. Increased ROS levels caused increased lipid peroxidation (LPO) in treatment groups exposed to both fresh and aged NPs, although LPO was comparatively higher in algae exposed to aged AgNPs. The observed increase in catalase (CAT) activity of algal cells was attributed to early stress responses induced by excessive intracellular ROS generation, and CAT levels were higher in the aged NP treatment groups. In conclusion, AgNPs increased ROS levels and LPO in algae and caused the activation of antioxidant enzymes such as CAT. Overall, the results suggest that aging and coating of AgNPs have major impacts on AgNP transformation in media and their effects on algae. Environ Toxicol Chem 2019;38:2371-2382. © 2019 SETAC.

Interaction of zero valent copper nanoparticles with algal cells under simulated natural conditions: Particle dissolution kinetics, uptake and heteroaggregation

Some metal-based engineered nanoparticles (ENPs) undergo fast dissolution and/or aggregation when they are released in the environment. The underlying processes are controlled by psychochemical/biological parameters of the environment and the properties of the particles. In this study, we investigated the interaction between algal cells and zero valent copper nanoparticles (Cu⁰-ENPs) to elucidate how the cells influence the dissolution and aggregation kinetics of the particles and how these kinetics influence the cellular uptake of Cu. Our finding showed that the concentration of dissolved Cu ([Cu]_dissolved) in the supernatant of the culture media without algal cells was higher than the [Cu]_dissolved in the media with algal cells. In the absence of the cells, dissolved organic matter (DOC) increased the dissolution of the particle due to increasing the stability of the particles against aggregation, thus increasing the available surface area. In the presence of algae, Cu⁰-ENPs heteroaggregated with the cells. Thus, the available surface area decreased over time and this resulted in a low dissolution rate of the particles. The DOC corona on the surface of the particles increased the heteroaggregation of the particles with the cells and decreases the uptake of the particles. Our findings showed that microorganisms influence the fate of ENPs in the environment, and they do so by modifying the dissolution and aggregation kinetics of the Cu⁰-ENPs.

Impact of temperature on the physicochemical, structural and biological features of copper-silica nanocomposites

Classical wet chemical synthesis was used to fabricate a hybrid composite that contained copper nanoparticles (average size ∼1 nm), which were embedded into a silicon oxide carrier. The structural and chemical alternations in the copper-functionalized silica were investigated in systems that were sintered at 573 K, 873 K, 1173 K, and 1473 K. A general trend, which was associated with the transformation of metallic copper with a cubic structure into copper(II) oxide with a monoclinic structure in the heat-treated systems, was found. XPS and FTIR spectroscopies also revealed the presence of copper(I) oxide, which formed a shell around the CuO. SEM and TEM showed gradual densification of the hybrid system at ever higher sintering temperatures, which corresponded with the gradual copper agglomeration. A temperature of 873 K was determined to be the temperature at which amorphous silica was transformed into cristoballite and tridymite, as well as the formation of a bulk-like copper structure. In relation to the physicochemical and structural data, high antimicrobial features that had a relatively low toxicity effect on the normal human fibroblasts (NHDF) below 250 mg/L was found for the initial copper-silica composite and the samples that were sintered at 573 K. In turn, a significant decrease in the biological impact was observed in the samples that were sintered at temperatures above 573 K. As a result, the paper discusses the model of structural modifications in copper-silica nanocomposite concerning their biological impact that was developed.

Physical and chemical transformations of zirconium doped ceria nanoparticles in the presence of phosphate: Increasing realism in environmental fate and behaviour experiments

During their lifecycle, many engineered nanoparticles (ENPs) undergo significant transformations that may modify their toxicity, behaviour, and fate in the environment. Therefore, understanding the possible environmentally relevant transformations that ENPs may undergo as a result of their surroundings is becoming increasingly important. This work considers industrially produced ceria (CeO₂) and focuses on a particle library consisting of seven zirconium-doped variants (Ce_1-xZr_xO₂) where the Zr doping range is x = 0-1. The study assesses their potential transformation in the presence of environmentally relevant concentrations of phosphate. These ENPs have an important role in the operation of automotive catalysts and therefore may end up in the environment where transformations can take place. Samples were exposed to pH adjusted (c. 5.5) solutions made up of either 1 mM or 5 mM each of KH₂PO₄, citric acid and ascorbic acid and the transformed particles were characterised by means of DLS - size and zeta potential, UV/VIS, TEM, FT-IR, EDX and XRD. Exposure to the phosphate solutions resulted in chemical and physical changes in all ceria-containing samples to cerium phosphate (with the monazite structure). The transformations were dependent on time, ceria concentration in the particles (Ce:Zr ratio) and phosphate to ceria ratio. The presence of Zr within the doped samples did not inhibit these transformations, yet the pure end member ZrO₂ ENPs showed no conversion to phosphate. The quite dramatic changes in size, structure and composition observed raise important questions regarding the relevant form of the materials to investigate in ecotoxicity tests, and for regulations based on one or more dimensions in the nanoscale.

Dissolution and aggregation kinetics of zero valent copper nanoparticles in (simulated) natural surface waters: Simultaneous effects of pH, NOM and ionic strength

The combined effects of pH, dissolved organic carbon (DOC) and Ca²⁺/Mg²⁺ on the dissolution and aggregation kinetics of zero valent copper engineered nanoparticles (Cu⁰ ENPs) were investigated. The dissolution and aggregation of the particles were studied in (a) synthetic aqueous media, similar in chemistry to natural surface waters, and (b) natural surface waters samples, for up to 32 or 24 h. The DOC stabilized the particles and prevented aggregation, and thus increased the available surface area. The higher available surface area in turn accelerated the dissolution of the particles. The presence of Ca²⁺/Mg²⁺, however, changed the aggregation and the dissolution of the DOC-stabilized particles. The influence of Ca²⁺/Mg²⁺ on DOC-stabilized particles was different at different pH's. In the absence of DOC, 10 mM of Ca²⁺/Mg²⁺ induced charge reversal on the particles and caused particle stability against aggregation. This subsequently increased particles dissolution. The results obtained with regard to dissolution and aggregation of the particles in natural surface waters were compared with those determined for the synthetic waters. This comparison showed that the behavior of the particles in the natural surface waters was mostly similar to the behavior determined for media at pH 9. Overall, the current study provides some novel insights into the simultaneous effects of physicochemical parameters of water on particle stability against aggregation and dissolution, and provides data about how the processes of aggregation and dissolution of Cu⁰ ENPs interact and jointly determine the overall particle fate.

Copper release and transformation following natural weathering of nano-enabled pressure-treated lumber

Commercially available lumber, pressure-treated with micronized copper azole (MCA), has largely replaced other inorganic biocides for residential wood treatment in the USA, yet little is known about how different outdoor environmental conditions impact the release of ionic, nano-scale, or larger (micron-scale) copper from this product. Therefore, we weathered pressure treated lumber for 18 months in five different climates across the continental United States. Copper release was quantified every month and local weather conditions were recorded continuously to determine the extent to which local climate regulated the release of copper from this nano-enabled product during its use phase. Two distinct release trends were observed: In cooler, wetter climates release occurred primarily during the first few months of weathering, as the result of copper leaching from surface/near-surface areas. In warmer, drier climates, less copper was initially released due to limited precipitation. However, as the wood dried and cracked, the exposed copper-bearing surface area increased, leading to increased copper release later in the product lifetime. Single-particle-ICP-MS results from laboratory prepared MCA-wood leachate solutions indicated that a) the predominant form of released copper passed through a filter smaller than 0.45 micrometers and b) released particles were largely resistant to dissolution over the course of 6 wks. Toxicity Characteristic Leaching Procedure (TCLP) testing was conducted on nonweathered and weathered MCA-wood samples to simulate landfill conditions during their end-of-life (EoL) phase and revealed that MCA wood released <10% of initially embedded copper. Findings from this study provide data necessary to complete a more comprehensive evaluation of the environmental and human health impacts introduced through release of copper from pressure treated lumber utilizing life cycle assessment (LCA).

Chemical Stability and Transformation of Molybdenum Disulfide Nanosheets in Environmental Media

Layered transition metal dichalcogenides, including molybdenum disulfide (MoS₂), have previously been considered stable in the ambient environment due to the absence of dangling bonds in the electron-filled shells of the end chalcogen atoms. Here, we evaluate the chemical stability of MoS₂ nanosheets fabricated by chemical exfoliation (ceMoS₂) and surfactant dispersion (sMoS₂). The results demonstrate that sMoS₂ exhibits greater long-term persistence. Contrarily, ceMoS₂ underwent progressive deterioration, in which preferential oxidation of the 1T of a mixture of 1T and 2H phases was observed. The oxidative degradation of ceMoS₂ was retarded in the presence of natural organic matter (NOM), including Suwannee River natural organic matter (SRNOM) and Aldrich humic acid (ALHA), in the dark ambient condition, while the aging process of MoS₂ with co-occurring ALHA was accelerated under sunlight exposure. The observed inhibition effect on the deterioration of ceMoS₂ by NOM was mainly attributed to slower dissolution kinetics with rapid initial oxidation (i.e., forming Mo-O bonding) or carbon grafting, rather than prevention of the formation of secondary small suspended Mo-containing particles. The compiled results highlight that the environmental fate of MoS₂ nanosheets will be regulated by the combined effects of exfoliating agents and environmentally relevant factors including organic macromolecules and sunlight exposure.

Aggregation, Sedimentation, and Dissolution of Copper Oxide Nanoparticles: Influence of Low-Molecular-Weight Organic Acids from Root Exudates

The rhizosphere is an essential pathway for the uptake of metal-based nanoparticles (MNPs) by plant roots. However, the interaction between root exudates and MNPs is still unclear. In this study, we initially identified the major low-molecular-weight organic acids (LMWOAs) in the rice root exudates using hydroponics. Then, the individual LMWOAs were added to CuO nanoparticle suspensions to investigate their effects on the environmental behavior of the MNPs. The results showed that both the variety and the concentration of LMWOAs impacted the aggregation, sedimentation, and dissolution of CuO nanoparticles (NPs). Almost all LMWOAs except succinic acid inhibited the aggregation of CuO NPs by enhancing the electrostatic repulsive force between NPs. The presence of citric and oxalic acids rather than lactic acid greatly improved the stability of CuO NP suspensions, but other acids showed a low promoting and high inhibiting effect on NP sedimentation. Moreover, all the LMWOAs from root exudates facilitated the dissolution of CuO NPs with a positive dose-dependent correlation, especially formic acid. Notably, citric acid, as the most abundant LMWOAs in rice root exudates, largely determined the aggregation, sedimentation, and dissolution of CuO NPs. This study provides a better understanding on NP-plant interactions in the rhizosphere.

In the Search for Nanospecific Effects of Dissolution of Metallic Nanoparticles at Freshwater-Like Conditions: A Critical Review

Knowledge on relations between particle properties and dissolution/transformation characteristics of metal and metal oxide nanoparticles (NPs) in freshwater is important for risk assessment and product development. This critical review aims to elucidate nanospecific effects on dissolution of metallic NPs in freshwater and similar media. Dissolution rate constants are compiled and analyzed for NPs of silver (Ag), copper (Cu), copper oxide/hydroxide (CuO, Cu(OH)₂), zinc oxide (ZnO), manganese (Mn), and aluminum (Al), showing largely varying (orders of magnitude) constants when modeled using first order kinetics. An effect of small primary sizes (<15 nm) was observed, leading to increased dissolution rate constants and solubility in some cases. However, the often extensive particle agglomeration can result in reduced nanospecific effects on dissolution and also an increased uncertainty related to the surface area, a parameter that largely influence the extent of dissolution. Promising ways to model surface areas of NPs in solution using fractal dimensions and size distributions are discussed in addition to nanospecific aspects related to other processes such as corrosion, adsorption of natural organic matter (NOM), presence of capping agents, and existence of surface defects. The importance of the experimental design on the results of dissolution experiments of metal and metal oxide NPs is moreover highlighted, including the influence of ionic metal solubility and choice of particle dispersion methodology.

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.

Rhizosphere interactions between copper oxide nanoparticles and wheat root exudates in a sand matrix: Influences on copper bioavailability and uptake

The impact of copper oxide nanoparticles (CuONPs) on crop production is dependent on the biogeochemistry of Cu in the rooting zone of the plant. The present study addressed the metabolites in wheat root exudates that increased dissolution of CuONPs and whether solubility correlated with Cu uptake into the plant. Bread wheat (Triticum aestivum cv. Dolores) was grown for 10 d with 0 to 300 mg Cu/kg as CuONPs in sand, a matrix deficient in Fe, Zn, Mn, and Cu for optimum plant growth. Increased NP doses enhanced root exudation, including the Cu-complexing phytosiderophore, 2'-deoxymugineic acid (DMA), and corresponded to greater dissolution of the CuONPs. Toxicity, observed as reduced root elongation, was attributable to a combination of CuONPs and dissolved Cu complexes. Geochemical modeling predicted that the majority of the solution phase Cu was complexed with citrate at low dosing or DMA at higher dosing. Altered biogeochemistry within the rhizosphere correlated with bio-responses via exudate type, quantity, and metal uptake. Exposure of wheat to CuONPs led to dose-dependent decreases in Fe, Ca, Mg, Mn, and K in roots and shoots. The present study is relevant to growth of a commercially important crop, wheat, in the presence of CuONPs as a fertilizer, fungicide, or pollutant. Environ Toxicol Chem 2018;37:2619-2632. © 2018 SETAC.

Soil pH effects on the toxicity of zinc oxide nanoparticles to soil microbial community

We conducted an experiment with two agricultural soils with acidic and alkaline pH levels to assess the effects of zinc oxide nanoparticles (nZnO) on the bacterial community. The effect of the nZnO concentrations (0, 0.1, 1, 10, 100, 1000 mg Zn/kg soil) and contact time between nanoparticles and soil (180 days) was considered. We measured the microbial respiration rate, nitrogen transformation, enzymatic activities (dehydrogenase (DH), acidic phosphatase (ACP), and alkaline phosphatase (ALP)), and the community-level physiological profile (CLPP) soil parameters. Respiration potential and nitrogen transformation were negatively affected only at the highest nZnO concentration. The changes in enzymatic activities were very variable with time and between both soils. A stimulating effect of the nanoparticles on microbial activity was clearly shown at 30 days after the nZnO application in both soils, except for the 1000 mg/kg in calcareous soil, after which time in the latter, the functional richness of the bacterial community was reduced to virtually zero. However, values of the enzymatic activities demonstrated that there was self-adaptation of microbial communities over the study period (180 days). The nZnO 1000 mg/kg dose produced an increase in bacterial growth in the acidic soil, without apparent changes in their metabolic profiles over time. A good correlation was found between microbial respiration rates (calcareous and acidic soils) and microbial metabolic activity (acidic soil) based on extracted Zn concentrations. Our findings suggest the necessity of additional studies to examine the effects of nZnO in natural microorganism populations in soil with different pH levels for extended periods of time.