Fate Of NPs Research Articles

Assessing the size transformation of nanoplastics in natural water matrices

Understanding the stability of NPs in different aqueous environments, related with their size is crucial for assessing their potential risks. This is influenced by several factors, including pH, ionic strength, and the presence of biomolecules, or dissolved organic matter (DOM). In this study, dispersions of NPs derived from common plastic waste materials, including polystyrene (PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), and polycarbonate (PC), were synthesized by a nanoprecipitation method with sizes: 189 ± 7, 58 ± 3, 123 ± 4, 151 ± 7 and 182 ± 6 nm, respectively. Stability for a period of 14 days of these NPs was assessed in various natural water matrices. Different analytical techniques were used, including Asymmetric Flow Field-Flow Fractionation (AF4) coupled with UV–Vis and Dynamic Light Scattering (DLS) in series, batch DLS, Fourier-Transform Infrared Spectroscopy-Attenuated Total Reflection (FTIR-ATR), and Transmission Electron Microscopy (TEM). None of the studied NPs was stable in seawater and NPs were transformed in microplastics (MPs) by aggregation. PET was more prone to aggregation in all waters and PS was the most stable followed for PC, PVC and PMMA. However, bottle and tap waters maintained better the original size of NPs. For the most stable dispersion PS, the influence of heteroaggregation in tap and lagoon waters and aging from exposure to UV light in sea water were tested. In both cases, the stability over time was worse for PS. The results can contribute to a more comprehensive understanding of the fate and behaviour of NPs in natural aquatic environments, emphasizing the importance of studying a wide range of polymers.

The In Vivo Biological Fate of Protein Corona: A Comparative PET Study of the Fate of Soft and Hard Protein Corona in Healthy Animal Models.

Radiolabeling and nuclear imaging techniques are used to investigate the biodistribution patterns of the soft and hard protein corona around poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) after administration to healthy mice. Soft and hard protein coronas of 131I-labeled BSA or 131I-labeled serum are formed on PLGA NPs functionalized with either polyehtylenimine (PEI) or bovine serum albumin (BSA). The exchangeability of hard and soft corona is assessed in vitro by gamma counting exposing PLGA NPs with corona to non-labeled BSA, serum, or simulated body fluid. PEI PLGA NPs form larger and more stable coronas than BSA PLGA NPs. Soft coronas are more exchangeable than hard ones.The in vivo fate of PEI PLGA NPs coated with preformed 18F-labeled BSA hard and soft coronas is assessed by positron emission tomography (PET)following intravenous administration. While the soft corona shows a biodistribution similar to free 18F BSA with high activity in blood and kidney, the hard corona follows patterns characteristic of nanoparticles, accumulating in the lungs, liver, and spleen. These results show that in vivo fates of soft and hard corona are different, and that soft corona is more easily exchanged with proteins from the body, while hard corona is largely retained on the nanoparticle surface.

Impact of seed priming with Selenium nanoparticles on germination and seedlings growth of tomato

Poor germination and seedlings growth can lead to significant economic losses for farmers, therefore, sustainable agricultural strategies to improve germination and early growth of crops are urgently needed. The objective of this work was to evaluate selenium nanoparticles (Se NPs) as nanopriming agents for tomato (Solanum lycopersicum) seeds germinated without stress conditions in both trays and Petri dishes. Germination quality, seedlings growth, synergism-antagonism of Se with other elements, and fate of Se NPs, were determined as function of different Se NPs concentrations (1, 10 and 50 ppm). Results indicated that the germination rate in Petri dishes improved with 10 ppm, while germination trays presented the best results at 1 ppm, increasing by 10 and 32.5%, respectively. Therefore, seedlings growth was measured only in germination trays. Proline content decreased up to 22.19% with 10 ppm, while for same treatment, the total antioxidant capacity (TAC) and total chlorophyll content increased up to 38.97% and 21.28%, respectively. Antagonisms between Se with Mg, K, Mn, Zn, Fe, Cu and Mo in the seed were confirmed. In the case of seedlings, the N content decreased as the Se content increased. Transmission Electron Microscopy (TEM) imaging confirmed that Se NPs surrounded the plastids of the seed cells. By this finding, it can be inferred that Se NPs can reach the embryo, which is supported by the antagonism of Se with important nutrients involved in embryogenesis, such as K, Mg and Fe, and resulted in a better germination quality. Moreover, the positive effect of Se NPs on total chlorophyll and TAC, and the negative correlation with proline content with Se content in the seed, can be explained by Se NPs interactions with proplastids and other organelles within the cells, resulting with the highest length and fresh weight when seeds were exposed to 1 ppm.

Protein Coronas Derived from Mucus Act as Both Spear and Shield to Regulate Transferrin Functionalized Nanoparticle Transcellular Transport in Enterocytes.

The epithelial mucosa is a key biological barrier faced by gastrointestinal, intraoral, intranasal, ocular, and vaginal drug delivery. Ligand-modified nanoparticles demonstrate excellent ability on this process, but their efficacy is diminished by the formation of protein coronas (PCs) when they interact with biological matrices. PCs are broadly implicated in affecting the fate of NPs in vivo and in vitro, yet few studies have investigated PCs formed during interactions of NPs with the epithelial mucosa, especially mucus. In this study, we constructed transferrin modified NPs (Tf-NPs) as a model and explored the mechanisms and effects that epithelial mucosa had on PCs formation and the subsequent impact on the transcellular transport of Tf-NPs. In mucus-secreting cells, Tf-NPs adsorbed more proteins from the mucus layers, which masked, displaced, and dampened the active targeting effects of Tf-NPs, thereby weakening endocytosis and transcellular transport efficiencies. In mucus-free cells, Tf-NPs adsorbed more proteins during intracellular trafficking, which enhanced transcytosis related functions. Inspired by soft coronas and artificial biomimetic membranes, we used mucin as an "active PC" to precoat Tf-NPs (M@Tf-NPs), which limited the negative impacts of "passive PCs" formed during interface with the epithelial mucosa and improved favorable routes of endocytosis. M@Tf-NPs adsorbed more proteins associated with endoplasmic reticulum-Golgi functions, prompting enhanced intracellular transport and exocytosis. In summary, mucus shielded against the absorption of Tf-NPs, but also could be employed as a spear to break through the epithelial mucosa barrier. These findings offer a theoretical foundation and design platform to enhance the efficiency of oral-administered nanomedicines.

Toxicity spectrum and detrimental effects of titanium dioxide nanoparticles as an emerging pollutant: A review

Titanium dioxide nanoparticles have wide industrial –applications, due to their enhanced mechanical, physical, optical and electrical properties. TiO2-based nanomaterials are extensively used in different industries for example paper, semiconductors, paint, food, cosmetics, water purification and textile. Besides its multiple applications in different domains of life, TiO2 has been reported for its hazardous effect on ecosystems, specifically on humans and mammals. The human body may be exposed to TiO2 NPs by three pathways i.e., oral, dermal and intra-gastric pathways and get accumulated in different parts of the body like the spleen, alimentary tract, central nervous system, liver, kidney, reproductive system, cardiac muscles and may form agglomerates with other mammalian cells. Additionally, these NPs may cross blood brain barrier and induce apoptosis in human hippocampal neurons. These NPs also show genotoxic effects that might leads towards the apoptosis and chromosomal instability. It has been observed experimentally that the cytotoxic effects of TiO2 depend on their size, shape, type and rate of consumption. This paper provides comprehensive information regarding hazardous effects reported for TiO2 NPs on living organisms (animals and humans). This information will be supportive for understanding the spectrum of toxicity associated with the NPs that will be helpful in deciding the fate of TiO2 NPs.

Core-Shell Au@Nanoplastics as a Quantitative Tracer to Investigate the Bioaccumulation of Nanoplastics in Freshwater Ecosystems.

Studies on the adverse effects of nanoplastics (NPs, particle diameter <1000 nm) including physical damage, oxidative stress, impaired cell signaling, altered metabolism, developmental defects, and possible genetic damage have intensified in recent years. However, the analytical detection of NPs is still a bottleneck. To overcome this bottleneck and obtain a reliable and quantitative distribution analysis in complex freshwater ecosystems, an easily applicable NP tracer to simulate their fate and behavior is needed. Here, size- and surface charge-tunable core-shell Au@Nanoplastics (Au@NPs) were synthesized to study the environmental fate of NPs in an artificial freshwater system. The Au core enables the quantitative detection of NPs, while the polystyrene shell exhibits NP properties. The Au@NPs showed excellent resistance to environmental factors (e.g., 1% hydrogen peroxide solution, simulating gastric fluid, acids, and alkalis) and high recovery rates (>80%) from seawater, lake water, sewage, waste sludge, soil, and sediment. Both positively and negatively charged NPs significantly inhibited the growth of duckweed (Lemna minor L.) but had little effect on the growth of cyanobacteria (Microcystis aeruginosa). In addition, the accumulation of positively and negatively charged NPs in cyanobacteria occurred in a concentration-dependent manner, with positively charged NPs more easily taken up by cyanobacteria. In contrast, negatively charged NPs were more readily internalized in duckweed. This study developed a model using a core-shell Au@NP tracer to study the environmental fate and behavior of NPs in various complex environmental systems.

Protein corona formed on the TiO2 nanoparticles promotes the hydrolysis of collagen in simulated gastrointestinal fluids

Titanium dioxide nanoparticles (TiO2 NPs) could interact with proteins in foods and gastrointestinal fluids, thus changing the properties and functions of proteins. Many research articles have only studied the interactions between TiO2 NPs and digestive enzymes or the gastrointestinal fate of TiO2 NPs without considering the effect of food matrix. Therefore, the interactions between TiO2 NPs and trypsin and its effects on the digestion of collagen in vitro were investigated. Results showed that the functionalization of amino acids (Asp, and Ser) significantly harmed the adsorption of trypsin by TiO2 NPs. The fluorescence quenching and isothermal titration calorimetry confirmed that the hydrogen bond and van der Waals force played an essential role in the interactions between TiO2 NPs and trypsin. The β-sheet content of trypsin bound to TiO2 NPs decreased from 52.40% to 50.73% while the random coil content increased from 20.20% to 22.63%. Binding sites were identified by molecular docking. Additionally, the digestibility of collagen was improved in vitro in the presence of TiO2 NPs analyzed by SDS-PAGE, hydroxyproline quantification, and the antioxidation of digested products. Hydroxyproline concentration increased by nearly 25% and ABTS radical scavenging rate increased by 50%. This study provides a new insight into the impact of nanoparticles on gastrointestinal digestion.

Co-transport of biochar nanoparticles (BC NPs) and rare earth elements (REEs) in water-saturated porous media: New insights into REE fractionation

The present study investigated the co-transport behavior of three REEs3+ (La3+, Gd3+, and Yb3+) with and without biochar nanoparticles (BC NPs) in water-saturated porous media. The presence of REEs3+ enhanced the retention of BC NPs in quartz sand (QS) due to decreased electrostatic repulsion between BC NPs and QS, enhanced aggregation of BC NPs, and the contribution of straining. The distribution coefficients (KD) in packed columns in the co-transport of BC NPs and three REEs3+ were much smaller than in batch experiments due to the different hydrodynamic conditions. In addition, we, for the first time, found that REE fractionation in the solid-liquid phase occurred during the co-transport of REEs3+ in the presence and absence of BC NPs. Note that the REE fractionation during the co-transport, which is helpful for the tracing application during earth surface processes, was driven by the interaction of REEs3+ with QS and BC NPs. This study elucidates novel insights into the fate of BC NPs and REEs3+ in porous media and indicates that (i) mutual effects between BC NPs and REE3+ should be considered when BC was applied to REE contaminated aquatic and soil systems; and (ii) REE fractionation provides a useful tool for identifying the sources of coexisting substances.

Thermodynamic investigation of nanoplastic aggregation in aquatic environments

In this study, the aggregation behavior of polystyrene nanoplastics (PS NPs) in the absence or presence of oppositely charged particulate matters is systematically investigated for a wide range of electrolyte conditions. Herein, we used isothermal titration calorimetry combined with time-resolved dynamic light scattering to provide kinetic and thermodynamic insights into the NP aggregation. The thermodynamic profiles of homoaggregation and heteroaggregation were fit using an independent site and two independent sites models, respectively, demonstrating different interaction modes of both aggregation processes. We found that the contribution of solvation entropy was significant and variable in most cases, and this thermodynamic parameter was a large determinant of the thermodynamics of NP aggregation. Furthermore, the stability of PS NPs in natural water matrices was found to be correlated with ionic strength and the content of natural colloids (e.g., metal oxides and clay particles). These results point to the importance of considering the role of thermodynamic variables when studying the fate of NPs within various environmental conditions.

Role of metal-nanoparticles in farming practices: an insight.

Nanotechnology introduces revolutionary approaches for agriculture in the form of nano-based pesticides, fertilizers, sensors, weed-controlling agents, enhanced seed germination materials,etc. Even though metal-nanoparticles (NPs) have shown their potential to improve crop yield, the mode of action at the cellular level and fate in the human body and the environment are not well understood yet. Several metal-nanoparticles have been studied extensively by researchers for their active role in enhancing the rate of seed germination and crop quality augmentation which may happen due to several mechanisms such as increased porosity in nano-primed seeds inducing up-regulation of the expression of aquaporin and Reactive Oxygen Species (ROS) genes involved in water uptake, improving the root dehydrogenase activity to enhance the water absorption capability, etc. However, researchers have also demonstrated and reported the possible toxicity of NPs in the environment due to their agricultural practices. But the fate of NPs and their environmental impact are still unclear and largely vary based on several factors such as the size of NPs, coating material, mode of discharge and locations, etc.This review thoroughly focuses on the mode of action of various NPs in seed germination and accumulation, translocation through cells, and potential environmental and health risks.

Characterization and Biomedical Application Opportunities of the Nanoparticle's Protein Corona

AbstractNanoparticles (NPs) are widely used in a variety of biomedical fields, such as drug delivery systems, novel theragnostic strategies, bioimaging, and biosensing. The protein corona formed by the contact between NPs and biological liquids changes the physicochemical nanoparticle characteristics, including size, shape, and surface statement. Moreover, it affects the biological fate of NPs in organisms, for instance, pharmacokinetic processes and therapeutical efficacy. Therefore, it is necessary to comprehensively identify and quantify the properties of the nanoparticle protein corona. This review focuses on screening the milestones and latest advances of the protein corona, the interaction between NPs and the protein corona, the detection and characterization of the protein corona, and the application of the protein corona in biomedicine. The application section mainly includes three aspects: 1) novel NPs targeting design based on protein corona; 2) personalized protein corona powered precision medicine by integrating multiple strategies, i.e., proteomics and computer science; and 3) opportunities for protein coronas in nanomedicine applications. Collectively, these summaries reveal the significance of the protein corona in nanomedicine and highlight the challenges of studying protein coronas based on nanoparticle properties.

Potential application of Au core labeling for tracking Ag nanoparticles in the aquatic and biological system

The entering of silver nanoparticles (Ag NPs) in natural environments constantly increases due to their widespread production and application. While the environmental behavior, impacts, and fate of Ag NPs were critically assessed, the main challenge represents continuous tracking and quantification of Ag NPs in environmental and biological matrices. A group of labeled Ag NPs with gold cores (Au@Ag NPs) was developed for distinguishing between pristine Ag NPs and their other forms, and we comprehensively compared their physicochemical properties, environmental behavior, and biological effects with unlabeled Ag NPs. The electron transfer process from the Au core to the Ag shell gradually decreased with the increase of Ag shell thickness, then the inhibition of Ag+ release induced by the Au core was gradually alleviated, but the generation of superoxide radicals was intensified sharply. Then, the effect of the Au core on the dissolution capacity and free radicals' generation significantly altered the biological toxicity of Ag NPs, and the influence degree was related to the test organism's species. Nevertheless, the Au core retained the surface properties of Ag NPs, leading to the uptake of Au@Ag NPs, entirely consistent with the behavior of unlabeled Ag NPs. These findings confirmed that Au core labeling provides new opportunities for tracking Ag NPs in environmental and biological systems, and the exposure conditions and test organisms should be carefully assessed before employing the Au core labeling technology.

Role of nanotechnology in management of plant viral diseases

Plant viral diseases cause huge economic losses and threat to sustainable agriculture. Nanotechnology is a growing technology in agronomy for the management of plant diseases. Nanoparticles can be used as nanopesticides, drug delivery agent or carriers for existing pesticides in pest management systems. Nanoparticles increase the disease resistance of plants by activating plant defense mechanisms or by deactivating microbes. Antiviral assay of different NPs has shown excellent virucidal properties against various plant viruses. Concerns raised about the fate and long-lasting effects of NPs on plants, soil microflora, humans, and the ecosystem. NPs have beneficial as well as harmful impacts on plants and the environment. This review discusses significant studies done to manage plant viral diseases. Silver, gold, zinc, copper, magnesium, nickel, silica, and bio-compounds nanomaterials were applied to control the virus and results have been compiled to draw a picture of the problem. This discussion will address the benefits of nanotechnology in plant viral disease management and the detrimental impacts of nanotechnology on the ecosystem.

Solubility of ZnO Nanoparticles in Food Media: An Analysis Using a Novel Semiclosed Dynamic System.

Food media can affect the solubility of zinc oxide nanoparticles (ZnO NPs). Moreover, when a single digestive fluid and a three-step digestion system were applied to investigate the fate of ZnO NPs, several contradictory results were obtained. Here, we manipulated a novel semiclosed in vitro dynamic digestion system to investigate the difference in the released ionic zinc (Zn2+) content in three types of artificial fluids in the presence of different food media. The results show that there was a significant difference in the released Zn2+ content between the three different types of digestion systems in the presence of the same food media. In addition, the released Zn2+ content was significantly different when different types of food media were applied to the same digestion system. These results demonstrate that the different levels of released Zn2+ content can be ascribed to the difference in digestion systems and food media.

Fate and impact of maghemite (γ-Fe2O3) and magnetite (Fe3O4) nanoparticles in barley (Hordeum vulgare L.).

The increasing demand for food in the world has made sustainable agriculture practices even more important. Nanotechnology applications in many areas have also been used in sustainable agriculture in recent years for the purposes to improve plant yield, pest control, etc. However, ecotoxicology and environmental safety of nanoparticles must be evaluated before large-scale applications. This study comparatively explores the efficacy and fate of different iron oxide NPs (γ-Fe2O3-maghemite and Fe3O4-magnetite) on barley (Hordeum vulgare L.). Various NP doses (50, 100, and 200 mg/L) were applied to the seeds in hydroponic medium for 3 weeks. Results revealed that γ-Fe2O3 and Fe3O4 NPs significantly improved the germination rate (~37% for γ-Fe2O3; ~63% for Fe3O4), plant biomass, and pigmentation (P < 0.005). Compared to the control, the iron content of tissues gradually raised by the increasing NPs doses revealing their translocation, which is confirmed by VSM analysis as well. The findings suggest that γ-Fe2O3 and Fe3O4 NPs have great potential to improve barley growth. They can be recommended for breeding programs as nanofertilizers. However, special care should be paid before the application due to their unknown effects on other living beings.

Effects of clay minerals on the transport of nanoplastics through water-saturated porous media

Clay minerals are important constituents of porous media. To date, only little is known about the transport and retention behavior of nanoplastics in clay-containing soil. To investigate the effects of clay minerals on the mobility of nanoplastics in saturated porous media, polystyrene nanoplastics (PS-NPs) were pumped through columns packed with sand and clay minerals (kaolinite and illite) at different pH and ionic strengths (IS). Mobility of PS-NPs decreased with increasing clay content attributed to physical straining effects (smaller pore throats and more complex flow pathways). Variations in pH and IS altered the surface charges of both PS-NPs and porous media and thus affecting the interaction energy. An increase of IS from 10 mM to 50 mM NaCl decreased the maximum energy barrier and secondary minimum from 142 KBT to 84 KBT and from −0.1 KBT to −0.72 KBT, respectively. Thus, the maximum C/C0 ratio decreased from ~51% to ~0% (pH 5.9, 3% kaolinite). Among the two clay minerals, kaolinite showed a stronger inhibitory effect on PS-NPs transport compared to illite. For instance, at the same condition (3% clay content, pH 5.9, 10 mM NaCl), the (C/C0)max of PS-NPs in kaolinite was ~51%, while for illite, it was ~77%. The difference in transport inhibition was mainly attributed to amphoteric sites on the edges of kaolinite which served as favorable deposition sites at pH 5.9 (pHpzc-edge is ~2.5 for illite and ~6.5 for kaolinite). Besides, the morphology of kaolinite was more complex than illite, which may retain more PS-NPs in kaolinite. Results and conclusions from the study will provide some valuable insights to better understand the fate of NPs in the soil-aquifer system.

Heteroaggregation of different surface-modified polystyrene nanoparticles with model natural colloids

This study investigated heteroaggregation of three surface-functionalized polystyrene nanoparticles (PSNPs), i.e. negatively charged unfunctionalized nanoparticles (Bare-PS) and carboxylated nanoparticles (COOH-PS), and positively charged amino-functionalized nanoparticles (NH2-PS), with two model natural colloids, positively charged hematite and negatively charged kaolin, respectively. Heteroaggregation was conducted at a constant natural colloid concentration and variable NP/colloid concentration ratios. Electrostatic interaction was the main mechanism driving the formation of heteroaggregates. In binary systems containing hematite and Bare-PS/COOH-PS, a charge neutralization – charge inverse mechanism was observed with the increase of PSNP concentration. At NP/hemetite concentration ratios much smaller or larger than the full charge neutralization point, the primary heteroaggregates were stable, while full charge neutralization induced the formation of large secondary heteroaggregates. Large aggregates were not observed in suspensions containing kaolin and NH2-PS, as highly positively charged NH2-PS reversed surface charges of kaolin at extremely low concentrations. Heteroaggregation between PSNPs and natural colloids with the same charge is unfavorable due to strong electrostatic repulsion. In the presence of electrolytes, homoaggregation and heteroaggregation both occurred, and homoaggregation of hematite played a key role when the concentration of PSNPs was low. The presence of Suwannee River natural organic matter (SRNOM) could modify surface charges of nanoparticles, and thus affect heteroaggregation behaviors of the binary suspension. When SRNOM and electrolytes were both present, whether SRNOM inducing or hindering the stability of the binary system was a combined effect of NP/colloid concentration ratios, SRNOM concentrations, electrolyte types and ionic strength. Mechanisms extensively reported in homoaggregation such as steric hindrance and cation bridging effects between SRNOM and Ca2+ also stand for heteroaggregation. These results highlight the critical role of surface modification on the environmental behaviors of NPs, and will underpin our understanding of the fate and transport of NPs in the aquatic environment.

Interaction of zinc oxide nanoparticles with soil: Insights into the chemical and biological properties.

Widespread use of zinc oxide nanoparticles (ZnO-NPs) threatens soil, plants, terrestrial and aquatic animals. Thus, it is essential to explore the fate and behavior of NPs in soil and also its mechanism of interaction with soil microbial biodiversity to maintain soil health and quality to accomplish essential ecosystem services. With this background, the model experiment was conducted in the greenhouse to study the impact of ZnO-NPs on soil taking maize as a test crop. The X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscopy and Particles size analysis of engineered NPs confirmed that the material was ZnO-NPs (particle size--65.82nm). The application of ZnO-NPs resulted in a significant decrease in soil pH. Significantly high EC (0.13dSm-1) was recorded where ZnO-NPs were applied at the rate of 2.5mg Znkg-1 soil over control (0.12dSm-1). A significant increase in soil available phosphorus was observed on applying ZnO-NPs (15.29mgkg-1 of soil) as compared to control (11.84mgkg-1 of soil). Maximum soil available Zn (2.09mgkg-1) was recorded in ZnO-NPs-amended soil (T11) which was significantly higher than control (0.33mgkg-1) as well as treatments containing conventional zincatic fertilizers. The inhibition rates of dehydrogenase enzyme activity in the presence of 0.5mg, 1.25mg and 2.5mg ZnO-NPs per kg soil were 31.3, 46.2 and 49.7%, respectively. Soil microbial biomass carbon was significantly reduced (103.33µgg-1 soil) in soils treated with ZnO-NPs over control (111.33µgg-1 soil). Soil bacterial count was also significantly lesser (12.33 × 105CFU) in the case where 2.5mgkg-1 ZnO-NPs were applied as compared to control (21.33 × 105CFU). The corresponding decrease in fungal and actinomycetes colony count was 24.16, 37.35, 46.15% and 14.59, 17.97, 22.45% with the application of 0.5mg, 1.25mg and 2.5mg ZnO-NPs per kg soil, respectively, as compared to control. Thus, the use of ZnO-NPs resulted in an increase in soil available Zn but inhibited soil microbial activity.

The fate and long-term toxic effects of NiO nanoparticles at environmental concentration in constructed wetland: Enzyme activity, microbial property, metabolic pathway and functional genes

Although the potential threats of metallic oxide nanoparticles (MNPs) to constructed wetland (CW) have been broadly reported, limited information is available regarding the long-term impact of nickel oxide nanoparticles (NiO NPs) on CWs at the environmentally relevant concentrations. Here, we comprehensively elucidated the responses in the treatment performance, enzyme activities, microbial properties, metabolic pathways and functional genes of CWs to chronic exposure of NiO NPs (0.1 and 1 mg/L) for 120 days, with a quantitative analysis on the fate and migration of NiO NPs within CWs. Nitrogen removal evidently declined under the long-term exposure to NiO NPs. Besides, NiO NPs induced a deterioration in phosphorus removal, but gradually restored over time. The activities of dehydrogenase (DHA), phosphatase (PST), urease (URE), ammonia oxygenase (AMO) and nitrate reductase (NAR) were inhibited to some extent under NiO NPs stress. Furthermore, NiO NPs exposure reduced bacterial diversity, shifted microbial composition and obviously inhibited the transcription of the ammonia oxidizing and denitrifying functional genes. The results of nickel mass balance indicated that the major removal mechanism of NiO NPs in CWs was through substrate adsorption and plants uptake. Thus, the ecological impacts of prolonged NiO NPs exposure at environmental concentrations should not be neglected.

“Nanosize effect” in the metal-handling strategy of the bivalve Scrobicularia plana exposed to CuO nanoparticles and copper ions in whole-sediment toxicity tests

To date, the occurrence, fate and toxicity of metal-based NPs in the environment is under investigated. Their unique physicochemical, biological and optical properties, responsible for their advantageous application, make them intrinsically different from their bulk counterpart, raising the issue of their potential toxic specificity or “nanosize effect”. The aim of this study was to investigate copper bioaccumulation, subcellular distribution and toxic effect in the marine benthic species Scrobicularia plana exposed to two forms of sediment-associated copper, as nanoparticles (CuO NPs) and as soluble ions (CuCl2). Results showed that the exposure to different copper forms activated specific organism's metal handling strategies. Clams bioaccumulated soluble copper at higher concentrations than those exposed to sediment spiked with CuO NPs. Moreover, CuO NPs exposure elicited a stronger detoxification response mediated by a prompt mobilization of CuO NPs to metal-containing granules as well as a delayed induction of MT-like proteins, which conversely, sequestered soluble copper since the beginning of the exposure at levels significantly different from the control. Eventually, exposure to high concentrations of either copper form led to the same acute toxic effect (100% mortality) but the outcome was delayed in bivalves exposed to CuO NPs suggesting that the mechanisms underlying toxicity were copper form-specific. Indeed, while most of soluble copper was associated to the mitochondrial fraction suggesting an impairment of the ATP synthesis capacity at mitochondrial level, CuO NPs toxicity was most likely caused by the oxidative stress mediated by their bioaccumulation in the enzymatic and mitochondrial metabolically available fractions.