Nanoparticles in the environment: assessment using the causal diagram approach

Review on fate, transport, toxicity and health risk of nanoparticles in natural ecosystems: Emerging challenges in the modern age and solutions toward a sustainable environment

In today's era, nanoparticles (NPs) have become an integral part of human life, finding extensive applications in various fields of science, pharmacy, medicine, industry, electronics, and communication. The increasing popularity of NP usage worldwide is a testament to their tremendous potential. However, the widespread deployment of NPs unavoidably leads to their release into the environmental matrices, resulting in persistence in ecosystems and bioaccumulation in organisms. Understanding the environmental behavior of NPs poses a significant challenge due to their nanoscale size. Given the current environmental releases of NPs, known negative consequences, and the limited knowledge available for risk management, comprehending the toxicity of NPs in ecosystems is both awaiting and crucial. The present review aims to unravel the potential environmental influences of nano-scaled materials, and provides in-depth inferences of the current knowledge and understanding in this field. The review comprehensively summarizes the sources, fate, transport, toxicity, health risks, and remediation solutions associated with NP pollution in aquatic and soil ecosystems. Furthermore, it addresses the knowledge gaps and outlines further investigation priorities for the sustainable control of NP pollution in these environments. By gaining a holistic understanding of these aspects, we can work toward ensuring the responsible and sustainable use of NPs in today's fast-growing world.

Nanoparticles at the maternal-fetal interface

The increasing production of intentional and unintentional nanoparticles (NPs) has led to their accumulation in the environment as air and ground pollution. The heterogeneity of these particles primarily relies on the NP physicochemical properties (i.e., chemical composition, size, shape, surface chemistry, etc.). Pregnancy represents a vulnerable life stage for both the woman and the developing fetus. The ubiquitous nature of these NPs creates a concern for developmental fetal exposures. At the maternal-fetal interface lies the placenta, a temporary endocrine organ that facilitates nutrient and waste exchange as well as communication between maternal and fetal tissues. Recent evidence in human and animal models identifies that gestational exposure to NPs results in placental translocation leading to local effects and endocrine disruption. Currently, the mechanisms underlying placental translocation and cellular uptake of NPs in the placenta are poorly understood. The purpose of this review is to assess the current understanding of the physiochemical factors influencing NP translocation, cellular uptake, and endocrine disruption at the maternal-fetal interface within the available literature.

Roles of polysaccharides-based nanomaterials in food preservation and extension of shelf-life of food products: A review

In food production sectors, food spoilage and contamination are major issues that threaten and negatively influence food standards and safety. Several physical, chemical, and biological methods are used to extend the shelf-life of food products, but they have their limitations. Henceforth, researchers and scientists resort to novel methods to resolve these existing issues. Nanomaterials-based extension of food shelf life has broad scope rendering a broad spectrum of activity including high antioxidant and antimicrobial activity. Numerous research investigations have been made to identify the possible roles of nanoparticles in food preservation. A wide range of nanomaterials via different approaches is ultimately applied for food preservation. Among them, chemically synthesized methods have several limitations, unlike biological synthesis. However, biological synthesis protocols are quite expensive and laborious. Predominant studies demonstrated that nanoparticles can protect fruits and vegetables by preventing microbial contamination. Though several nanomaterials designated for food preservation are available, detailed knowledge of the mechanism remains unclear. Hence, this review aims to highlight the various nanomaterials and their roles in increasing the shelf life of food products. Adding to the novel market trends, nano-packaging will open new frontiers and prospects for ensuring food safety and quality.

The effects of 100 nm pure boron nanoparticles on the primary antioxidant system of Nile tilapia (Oreochromisniloticus)

In this study, the effects of 100 nm boron nanoparticles (B-NPs) on the primary antioxidant status of Nile tilapia were researched via analysis of enzyme activities and related gene expressions. This is a new study which focuses on the relationship between B-NPs and oxidative stress that contribute to the literature in terms of its scope. Fish (n = 15) for each group were exposed to three different concentrations as 5, 25 (n2) and 125 (n3) mg/L during 96 h to see the response of the primary antioxidant system. According to the results, SOD expressions differed in all treatment groups compared to the control group (P < 0.05). CAT expressions were different in 5 and 125 mg/L groups compared to control and 25 mg/L groups (P < 0.05). GPX expressions were only different in 125 mg/L group (P < 0.05). The changes in enzyme activities of SOD and CAT were significantly different in 25 mg/L groups. GPX enzyme activities were not significant (P > 0.05). TBARS concentrations in 25 mg/L group were significantly different from those in the control and 125 mg/L groups (P < 0.05).

Immunomodulatory effects of nanoparticles on dendritic cells in a model of allergic contact dermatitis: importance of PD-L2 expression

Nanoparticle (NP) skin exposure is linked to an increased prevalence of allergic contact dermatitis. In our prior studies using the mouse contact hypersensitivity (CHS) model, we reported that silica 20 nm (SiO2) NPs suppressed the allergic response and titanium dioxide NPs doped with manganese (mTiO2) exacerbated it. In this work, we conducted in vitro experiments using bone marrow-derived dendritic cells (BMDCs) to study the combinatorial effect of the potent 2,4-dinitrofluorobenzene (DNFB) hapten sensitizer with SiO2 and mTiO2 NPs on BMDC cytotoxicity, cytokine secretion and phenotype using the B7 family ligands. Results show that DNFB and mTiO2 behave similarly and exhibit proinflammatory characteristics while SiO2 promotes a naive phenotype. We observe that the B7-H3 (CD276) ligand is only expressed on CD80 + (B7-1) BMDCs. Results from adoptive transfer CHS studies, combined with BMDC phenotype analysis, point to the importance of PD-L2 expression in modulating the adaptive immune response. This work identifies metrics that can be used to predict the effects of NPs on contact allergy and to guide efforts to engineer cell-based therapies to induce hapten specific immune tolerance.

Immunomodulatory Effects of Nanoparticles on Dendritic Cells in a Model of Allergic Contact Dermatitis - Importance of PD-L2 Expression

Nanoparticle (NP) skin exposure is linked to the increased prevalence of allergic contact dermatitis. In prior studies using the mouse contact hypersensitivity (CHS) model, we reported that silica 20 nm (Si20nm) suppressed the allergic response and TiO2 doped with manganese (mTiO2) exacerbated it. In this work, we conducted in vitro experiments using bone marrow-derived dendritic cells (BMDCs) to study the combinatorial effect of the potent 2, 4-dinitrofluorobenzene (DNFB) hapten sensitizer with Si20nm and mTiO2 NPs on BMDC cytotoxicity, cytokine secretion and phenotype using the B7 family ligands. Results show that DNFB and mTiO2 behave similarly and exhibit proinflammatory characteristics while Si20nm promotes a naive phenotype. We observe that the B7-H3 (CD276) ligand is only expressed on CD80+ (B7-1) BMDC. Results from adoptive transfer CHS studies, combined with BMDC phenotype analysis, point to the importance of PD-L2 expression in modulating the adaptive immune response. This work identifies metrics that can be used to predict the effects of NPs on contact allergy and to guide efforts to engineer cell-based therapies to induce antigen specific immune tolerance.

Nanoparticle-induced immune response: Health risk versus treatment opportunity?

Nanoparticles (NPs) are not only employed in many biomedical applications in an engineered form, but also occur in our environment, in a more hazardous form. NPs interact with the immune system through various pathways and can lead to a myriad of different scenarios, ranging from their quiet removal from circulation by macrophages without any impact for the body, to systemic inflammatory effects and immuno-toxicity. In the latter case, the function of the immune system is affected by the presence of NPs. This review describes, how both the innate and adaptive immune system are involved in interactions with NPs, together with the models used to analyse these interactions. These models vary between simple 2D in vitro models, to in vivo animal models, and also include complex all human organ on chip models which are able to recapitulate more accurately the interaction in the in vivo situation. Thereafter, commonly encountered NPs in both the environment and in biomedical applications and their possible effects on the immune system are discussed in more detail. Not all effects of NPs on the immune system are detrimental; in the final section, we review several promising strategies in which the immune response towards NPs can be exploited to suit specific applications such as vaccination and cancer immunotherapy.

Nanomaterials in agriculture for plant health and food safety: a comprehensive review on the current state of agro-nanoscience

In the modern epoch, nanotechnology took forward the agriculture and food industry with new tools that promise to increase food production sustainably. It also anticipated that it would become a driving economic force shortly. Nanotechnology has the potential to reduce agricultural inputs, enrich the soil by absorbing nutrients, manage plant diseases, and detect diseases. The aim of the present review is to cover the potential aspects of nanoscience and its trend-setting appliances in modern agriculture and food production. This review focuses on the impact of various nanomaterials on plant health to improve agricultural production and its cooperative approach to food production. Nanotechnology has great potential compared to conventional approaches. The appealing path of nanotrends in the farming sector raises hopes and illuminates the route of innovative technologies to overcome various diseases in plants with an enhanced yield to meet the growing global population's need for food security.

Photoreduction behavior of Cr(VI) on oxidized carbon nanoparticles: From photocatalytic efficiency to oxygenated groups

Clarifying the reaction process and specific mechanism between variable-valence elements and oxidized carbon nanoparticles is essential to evaluate the environmental impact of carbon nanomaterials. In this study, the photocatalytic reduction of Cr(VI) on oxidized carbon nanotubes (OCNTs), oxidized graphene ribbons (OGRs), and graphene oxide sheets (GOs) was explored by batch experiments and spectroscopic analyses. The reaction efficiencies strongly depended on the number of oxygenated groups in the oxidized carbon nanoparticles. The abundant oxygenated groups enabled the GOs to exhibit the highest photocatalytic activity, followed by the OGRs and OCNTs. As a result, the photoreduction efficiency of Cr(VI) reached 96% for GOs, whereas those of OGRs and OCNTs were only 40% and 13%, respectively. In addition, different types of oxygenated groups exhibited various activities based on molecular model tests, following the sequence carboxylic > hydroxyl > carbonyl > ether > aldehyde > edge. Based on the underlying relationship between the oxygenated groups, topological structures, and mechanical strain in the carbon nanoparticles, we speculate that mechanical strain plays a critical role in the formation of oxygenated groups, thereby regulating their photocatalytic activities. The findings in this work provide novel insights into the roles of oxygenated groups and the mechanical strain of carbon nanoparticles in their environmental behavior.

The New Attempt at Modeling of the Three-Dimensional Geometry of the Epidermal Skin Layer and the Diffusion Processes of Nanomolecular Drug Carriers in Such Structures

Nanoparticles are presently considered the efficient carriers of medicals, cosmetics, and pharmaceuticals in the human organism. There is a lot of research carried out on the delivery of these materials in a non-invasive way. Such a method is very safe in times of global illnesses and pandemics. The most frequently investigated route is the approach to delivering nano-media through the skin as the result of diffusion processes. The stratum corneum, the outermost layer of skin, is the most resistive barrier to such a form of penetration. In this work, a new model is proposed to predict nanoparticles' transport through this layer. It introduces the concept of the three-dimensional model of the stratum corneum, which allows to define the skin surface area from which diffusion occurs. This structure was replaced by the single capillary, resulting from theoretical considerations. Modeling of the diffusion process of nanoparticles as the result of Brownian motion in such a capillary was performed numerically using COMSOL Multiphysics package programs. Further, using the dimensions of such a capillary, a new model of diffusion was developed in which the parameters allow to determine the effective diffusion coefficient as a function of nanoparticle size and the viscosity of a liquid. As a result, the proposed models provide a new and efficient approach to the determination of the nano-molecules' transport phenomena through the skin layer.

Exposure to low levels of photocatalytic TiO2 nanoparticles enhances seed germination and seedling growth of amaranth and cruciferous vegetables

Titanium dioxide (TiO₂) is one of the most common compounds on Earth, and it is used in natural forms or engineered bulks or nanoparticles (NPs) with increasing rates. However, the effect of TiO₂ NPs on plants remains controversial. Previous studies demonstrated that TiO₂ NPs are toxic to plants, because the photocatalytic property of TiO₂ produces biohazardous reactive oxygen species. In contrast, another line of evidence suggested that TiO₂ NPs are beneficial to plant growth. To verify this argument, in this study, we used seed germination of amaranth and cruciferous vegetables as a model system. Intriguingly, our data suggested that the controversy was due to the dosage effect. The photocatalytic activity of TiO₂ NPs positively affected seed germination and growth through gibberellins in a plant-tolerable range (0.1 and 0.2 mg/cm²), whereas overdosing (1 mg/cm²) induced tissue damage. Given that plants are the foundations of the ecosystem; these findings are useful for agricultural application, sustainable development and maintenance of healthy environments.

Nanowaste: Another Future Waste, Its Sources, Release Mechanism, and Removal Strategies in the Environment

Nanowaste is defined as waste derived from materials with at least one dimension in the 1–100 nm range. The nanomaterials containing products are considered as “nanoproducts” and they can lead to the development of nanomaterial-containing waste, also termed as “nanowaste”. The increased production and consumption of these engineered nanomaterials (ENMs) and nanoproducts that generate enormous amounts of nanowaste have raised serious concerns about their fate, behavior, and ultimate disposal in the environment. It is of the utmost importance that nanowaste is disposed of in an appropriate manner to avoid an adverse impact on human health and the environment. The unique properties of ENMs, combined with an inadequate understanding of appropriate treatment techniques for many forms of nanowaste, makes nanowaste disposal a complex task. Presently, there is a lack of available information on the optimized standards for identifying, monitoring, and managing nanowaste. Therefore, this review highlights concerns about nanowaste as future waste that need to be addressed. The review focuses on ENMs waste (in the form of NP, nanotubes, nanowires, and quantum dots) generated from the manufacture of a wide variety of nanoproducts that end up as nanowaste and adversely affect the environment. Furthermore, the review considers different types of ENMs in waste streams and environmental compartments (i.e., soil, water, and air). Detailed studies are still required to identify data gaps and implement strategies to remove and control this future waste.

Aquatic ecotoxicity of manufactured silica nanoparticles: A systematic review and meta-analysis

Manufactured silica nanoparticles are used worldwide in large volumes for a variety of applications. An exposure of environmental organisms is therefore likely, and several data on the ecotoxicology of silica nanoparticles to different organisms have been published in recent years. This systematic review compiles and assesses these studies, in order to analyse the sensitivity distribution across different organisms. On this basis, maximum acceptable environmental concentrations are suggested and potential environmental risks are discussed. 1429 papers were retrieved from the scientific literature (Scopus), the U.S. ECOTOX knowledge database. 63 studies were finally included in the review and appraised according to the nanoCRED criteria. A total of 219 ecotoxicological endpoints recorded in 38 species (7 taxonomic groups) were condensed into a species sensitivity distribution. The resulting concentration that is hazardous for a maximum of 5% of exposed species (HC05) is 130 μg/L, from which a PNEC of 30 μg/L is estimated by applying an assessment factor of 5. These concentrations are 1-3 orders of magnitudes above the concentrations modelled to occur in European aquatic ecosystems. Algae and bacteria have a comparatively low sensitivity to MSNP exposure, likely because their cell wall forms a protective barrier against nanoparticle exposure. Similarly, embryonic stages of fish also show a comparatively low sensitivity due to the protection from their chorion. However, the fish species Labeo rohita and Oncorhynchus mykiss are among the most sensitive species. The ecotoxicity of silica nanoparticles is linked to the number of hydroxyl groups on their surface, corresponding to findings from human toxicological studies. It is recommended that future ecotoxicological studies use explicit concentration-response designs, use proven biocide-free testing material, comparatively apply mass and surface area as exposure metrics, and provide important metainformation in the study report.

Surface Coating-Modulated Phytotoxic Responses of Silver Nanoparticles in Plants and Freshwater Green Algae

Silver nanoparticles (AgNPs) have been implemented in a wide range of commercial products, resulting in their unregulated release into aquatic as well as terrestrial systems. This raises concerns over their impending environmental effects. Once released into the environment, they are prone to various transformation processes that modify their reactivity. In order to increase AgNP stability, different stabilizing coatings are applied during their synthesis. However, coating agents determine particle size and shape and influence their solubility, reactivity, and overall stability as well as their behavior and transformations in the biological medium. In this review, we attempt to give an overview on how the employment of different stabilizing coatings can modulate AgNP-induced phytotoxicity with respect to growth, physiology, and gene and protein expression in terrestrial and aquatic plants and freshwater algae.

Molecular characterization of superoxide dismutase and catalase genes, and the induction of antioxidant genes under the zinc oxide nanoparticle-induced oxidative stress in air-breathing magur catfish (Clarias magur)

The deduced amino acid sequences from the complete cDNA coding sequences of three antioxidant enzyme genes (sod1, sod2, and cat) demonstrated that phylogenetically the magur catfish (Clarias magur) is very much close to other bony fishes with complete conservation of active site residues among piscine, amphibian, and mammalian species. The three-dimensional structures of three antioxidant enzyme proteins are very much similar to mammalian counterparts, thereby suggesting the functional similarities of these enzymes. Exposure to ZnO NPs resulted in an oxidative stress as evidenced by an initial sharp rise of intracellular concentrations of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) but decreased gradually at later stages. The level of glutathione (GSH) also increased gradually in all the tissues examined after an initial decrease. Biochemical and gene expression analyses indicated that the magur catfish has the ability to defend the ZnO NP-induced oxidative stress by inducing the SOD/CAT enzyme system and also the GSH-related enzymes that are mediated through the activation of various antioxidant-related genes both at the transcriptional and translational levels in various tissues. Furthermore, it appeared that the stimulation of NO, as a consequence of induction nos2 gene, under NP-induced oxidative stress serves as a modulator to induce the SOD/CAT system in various tissues of magur catfish as an antioxidant strategy. Thus, it can be contemplated that the magur catfish possesses a very efficient antioxidant defensive mechanisms to defend against the oxidative stress and also from related cellular damages during exposure to ZnO NPs into their natural environment.

Adsorption of free radical TEMPO onto Al2O3 nanoparticles and evaluation of radical scavenging activity

This study describes the adsorption of free radical TEMPO onto Al₂O₃ nanoparticles in the solvents with different polarities including DMF, methanol, acetone, THF, petroleum ether and n-hexane at ambient temperature to evaluate the radical scavenging activity. The adsorption percentage of radical is calculated by measuring the maximum adsorption intensity of the ultraviolet (UV) absorption spectrum of TEMPO in the presence and the absence of Al₂O₃ nanoparticles. The morphology of Al₂O₃ nanoparticles before and after adsorption of TEMPO is studied using transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy. The adsorption energy and other thermochemical data for the adsorption of TEMPO over different active sites of Al₂O₃ are estimated via dispersion corrected density functional theory (DFT + Disp). The donor-acceptor interactions between Al₂O₃ and TEMPO are calculated using natural bond orbital (NBO) theory. It is found that Al₂O₃ nanoparticles have efficient radical scavenging activity (RSA) in the range of 50-72%. Approximately, a linear relationship between dielectric constant of solvent and the absorption percentage of TEMPO over Al₂O₃ nanoparticles is achieved. So that with decreasing the polarity of solvent, the adsorption of TEMPO onto Al₂O₃ nanoparticles is increased. The adsorption of TEMPO over Lewis acidic sites of Al₂O₃ is more favored than Brønsted acidic and basic sites. The comparison between experimental and calculated IR spectra of TEMPO/Al₂O₃ complexes provides the good evidence for adsorption of TEMPO onto the surface of Al₂O₃ nanoparticles.

A Critical Review of the Use of Surfactant-Coated Nanoparticles in Nanomedicine and Food Nanotechnology

Surfactants, whose existence has been recognized as early as 2800 BC, have had a long history with the development of human civilization. With the rapid development of nanotechnology in the latter half of the 20th century, breakthroughs in nanomedicine and food nanotechnology using nanoparticles have been remarkable, and new applications have been developed. The technology of surfactant-coated nanoparticles, which provides new functions to nanoparticles for use in the fields of nanomedicine and food nanotechnology, is attracting a lot of attention in the fields of basic research and industry. This review systematically describes these "surfactant-coated nanoparticles" through various sections in order: 1) surfactants, 2) surfactant-coated nanoparticles, application of surfactant-coated nanoparticles to 3) nanomedicine, and 4) food nanotechnology. Furthermore, current progress and problems of the technology using surfactant-coated nanoparticles through recent research reports have been discussed.

Sub-chronic effects of AgNPs and AuNPs on Gammarus fossarum (Crustacea Amphipoda): From molecular to behavioural responses

The aim of the present study was the assessment of the sub-chronic effects of silver (AgNPs) and gold nanoparticles (AuNPs) of 40 nm primary size either stabilised with citrate (CIT) or coated with polyethylene glycol (PEG) on the freshwater invertebrate Gammarus fossarum. Silver nitrate (AgNO₃) was used as a positive control in order to study the contribution of silver ions potentially released from AgNPs on the observed effects. A multibiomarker approach was used to assess the long-term effects of AgNPs and AuNPs 40 nm on molecular, cellular, physiological and behavioural responses of G. fossarum. Specimen of G. fossarum were exposed for 15 days to 0.5 and 5 µgL^-1 of CIT and PEG AgNPs and AuNPs 40 nm in the presence of food. A significant uptake of both Ag and Au was observed in exposed animals but was under the toxic threshold leading to mortality of G. fossarum. Silver nanoparticles (CIT-AgNPs and PEG-AgNPs 40 nm) led to an up-regulation of Na⁺K⁺ATPase gene expression. An up-regulation of Catalse and Chitinase gene expressions due to exposure to PEG-AgNPs 40 nm was also observed. Gold nanoparticles (CIT and PEG-AuNPs 40 nm) led to an increase of CuZnSOD gene expression. Furthermore, both AgNPs and AuNPs led to a more developed digestive lysosomal system indicating a general stress response in G. fossarum. Both AgNPs and AuNPs 40 nm significantly affected locomotor activity of G. fossarum while no effects were observed on haemolymphatic ions and ventilation.

Ultralow Loading Ruthenium on Alumina Monoliths for Facile, Highly Recyclable Reduction of p-Nitrophenol

The pervasive use of toxic nitroaromatics in industrial processes and their prevalence in industrial effluent has motivated the development of remediation strategies, among which is their catalytic reduction to the less toxic and synthetically useful aniline derivatives. While this area of research has a rich history with innumerable examples of active catalysts, the majority of systems rely on expensive precious metals and are submicron- or even a few-nanometer-sized colloidal particles. Such systems provide invaluable academic insight but are unsuitable for practical application. Herein, we report the fabrication of catalysts based on ultralow loading of the semiprecious metal ruthenium on 2–4 mm diameter spherical alumina monoliths. Ruthenium loading is achieved by atomic layer deposition (ALD) and catalytic activity is benchmarked using the ubiquitous para-nitrophenol, NaBH4 aqueous reduction protocol. Recyclability testing points to a very robust catalyst system with intrinsic ease of handling.

Genetic and systemic toxicity induced by silver and copper oxide nanoparticles, and their mixture in Clarias gariepinus (Burchell, 1822)

Unanticipated increase in the use of silver (Ag) and copper oxide (CuO) nanoparticles (NPs) due to their antimicrobial properties is eliciting environmental health concern because of their coexistence in the aquatic environment. Therefore, we investigated the genetic and systemic toxicity of the individual NPs and their mixture (1:1) using the piscine micronucleus (MN) assay, haematological, histopathological (skin, gills and liver) and hepatic oxidative stress analyses [malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT)] in the African mud catfish, Clarias gariepinus. The fish were exposed to sublethal concentrations (6.25-100.00 mg/L) of each NP and their mixture for 28 days. Both NPs and their mixture induced significant (p < 0.05) increase in MN frequency and other nuclear abnormalities. There was significant decrease in haemoglobin concentration, red and white blood cell counts. Histopathological lesions observed include epidermal skin cells and gill lamellae hyperplasia and necrosis of hepatocytes. The levels of MDA, GSH and activities of SOD and CAT were impacted in C. gariepinus liver following the exposure to the NPs and their mixture. Interaction factor analysis of data indicates antagonistic genotoxicity and oxidative damage of the NPs mixture. These results suggest cytogenotoxic effects of Ag NPs, CuO NPs and their mixture via oxidative stress in Clarias gariepinus.

Silver nanoparticles enter the tree stem faster through leaves than through roots

A major environmental pollution problem is the release into the atmosphere of particulate matter, including nanoparticles (NPs), which causes serious hazards to human and ecosystem health, particularly in urban areas. However, knowledge about the uptake, translocation and accumulation of NPs in plant tissues is almost completely lacking. The uptake of silver nanoparticles (Ag-NPs) and their transport and accumulation in the leaves, stems and roots of three different tree species, downy oak (Quercus pubescens Willd.), Scots pine (Pinus sylvestris L.) and black poplar (Populus nigra L.), were assessed. In the experiment, Ag-NPs were supplied separately to the leaves (via spraying, the foliar treatment) and roots (via watering, the root treatment) of the three species. Uptake, transport and accumulation of Ag were investigated through spectroscopy. The concentration of Ag in the stem was higher in the foliar than in the root treatment, and in poplar more than in oak and pine. Foliar treatment with Ag-NPs reduced aboveground biomass and stem length in poplars, but not in oaks or pines. Species-specific signals of oxidative stress were observed; foliar treatment of oak caused the accumulation of H2O2 in leaves, and both foliar and root treatments of poplar led to increased O2- in leaves. Ag-NPs affected leaf and root bacteria and fungi; in the case of leaves, foliar treatment reduced bacterial populations in oak and poplar and fungi populations in pine, and in the case of roots, root treatment reduced bacteria and increased fungi in poplar. Species-specific mechanisms of interaction, transport, allocation and storage of NPs in trees were found. We demonstrated definitively that NPs enter into the tree stem through leaves faster than through roots in all of the investigated tree species.

Risk Governance of Nanomaterials: Review of Criteria and Tools for Risk Communication, Evaluation, and Mitigation

Nanotechnologies have been increasingly used in industrial applications and consumer products across several sectors, including construction, transportation, energy, and healthcare. The widespread application of these technologies has raised concerns regarding their environmental, health, societal, and economic impacts. This has led to the investment of enormous resources in Europe and beyond into the development of tools to facilitate the risk assessment and management of nanomaterials, and to inform more robust risk governance process. In this context, several risk governance frameworks have been developed. In our study, we present and review those, and identify a set of criteria and tools for risk evaluation, mitigation, and communication, the implementation of which can inform better risk management decision-making by various stakeholders from e.g., industry, regulators, and the civil society. Based on our analysis, we recommend specific methods from decision science and information technologies that can improve the existing risk governance tools so that they can communicate, evaluate, and mitigate risks more transparently, taking stakeholder perspectives and expert opinion into account, and considering all relevant criteria in establishing the risk-benefit balance of these emerging technologies to enable more robust decisions about the governance of their risks.

The impact of tomato fruits containing multi-walled carbon nanotube residues on human intestinal epithelial cell barrier function and intestinal microbiome composition

Carbon nanomaterials (CNMs) can positively regulate seed germination and enhance plant growth. However, clarification of the impact of plant organs containing absorbed CNMs on animal and human health is a critical step of risk assessment for new nano-agro-technology. In this study, we have taken a comprehensive approach to studying the effect tomato fruits derived from plants exposed to multi-walled carbon nanotubes (CNTs) have on gastrointestinal epithelial barrier integrity and their impact on the human commensal intestinal microbiota using an in vitro cell culture and batch human fecal suspension models. The effects of CNTs on selected pure cultures of Salmonella enterica Typhimurium and Lactobacillus acidophilus were also evaluated. This study demonstrated that CNT-containing fruits or the corresponding residual level of pure CNTs (0.001 μg ml-1) was not sufficient to initiate a significant change in transepithelial resistance and on gene expression of the model T-84 human intestinal epithelial cells. However, at 10 μg ml-1 concentration CNTs were able to penetrate the cell membrane and change the gene expression profile of exposed cells. Moreover, extracts from CNT-containing fruits had minimal to no effect on human intestinal microbiota as revealed by culture-based analysis and 16S rRNA sequencing.

Environmental impacts of nanomaterials

Nanotechnology is currently one of the highest priority research fields in many countries due to its immense potentiality and economic impact. Nanotechnology involves the research, development, production, and processing of structures and materials on a nanometer scale in various fields of science, technology, health care, industries, and agriculture. As such, it has contributed to the gradual restructuring of many associated technologies. However, due to the uncertainties and irregularities in shape, size, and chemical compositions, the presence of certain nanomaterials may exert adverse impacts on the environment as well as human health. Concerns have thus been raised about the destiny, transport, and transformation of nanoparticles released into the environment. A critical evaluation of the current states of knowledge regarding the exposure and effects of nanomaterials on the environment and human health is discussed in this review. Recognition on the potential advantages and unintended dangers of nanomaterials to the environment and human health is critically important to pursue their development in the future.

Recent Developments on Nanotechnology in Agriculture: Plant Mineral Nutrition, Health, and Interactions with Soil Microflora

Plant mineral nutrition is important for obtaining higher agricultural productivity to meet the future demands of the increasing global human population. It is envisaged that nanotechnology can provide sustainable solutions by replacing traditional bulk fertilizers with their nanoparticulate counterparts possessing superior properties to overcome the current challenges of bioavailability and uptake of minerals, increasing crop yield, reducing fertilizer wastage, and protecting the environment. Recent studies have shown that nanoparticles of essential minerals and nonessential elements affect plant growth, physiology, and development, depending on their size, composition, concentration, and mode of application. The current review includes the recent findings on the positive as well as negative effects that nanofertilizers exert on plants when applied via foliar and soil routes, their effects on plant associated microorganisms, and potential for controlling agricultural pests. This review suggests future research needed for the development of sustained release nanofertilizers for enhancing food production and environmental protection.

Review on nanoparticles and nanostructured materials: history, sources, toxicity and regulations

Nanomaterials (NMs) have gained prominence in technological advancements due to their tunable physical, chemical and biological properties with enhanced performance over their bulk counterparts. NMs are categorized depending on their size, composition, shape, and origin. The ability to predict the unique properties of NMs increases the value of each classification. Due to increased growth of production of NMs and their industrial applications, issues relating to toxicity are inevitable. The aim of this review is to compare synthetic (engineered) and naturally occurring nanoparticles (NPs) and nanostructured materials (NSMs) to identify their nanoscale properties and to define the specific knowledge gaps related to the risk assessment of NPs and NSMs in the environment. The review presents an overview of the history and classifications of NMs and gives an overview of the various sources of NPs and NSMs, from natural to synthetic, and their toxic effects towards mammalian cells and tissue. Additionally, the types of toxic reactions associated with NPs and NSMs and the regulations implemented by different countries to reduce the associated risks are also discussed.

The Role of Citric Acid in the Stabilization of Nanoparticles and Colloidal Particles in the Environment: Measurement of Surface Forces between Hafnium Oxide Surfaces in the Presence of Citric Acid

The interactions between colloidal particles and nanoparticles determine solution stability and the structures formed when the particles are unstable to flocculation. Therefore, knowledge of the interparticle interactions is important for understanding the transport, dissolution, and fate of particles in the environment. The interactions between particles are governed by the surface properties of the particles, which are altered when species adsorb to the surface. The important interactions in the environment are almost never those between the bare particles but rather those between particles that have been modified by the adsorption of natural organic materials. Citric acid is important in this regard not only because it is present in soil but also as a model of humic and fulvic acids. Here we have studied the surface forces between the model metal oxide surface hafnia in the presence of citric acid in order to understand the stability of colloidal particles and nanoparticles. We find that citric acid stabilizes the particles over a wide range of pH at low to moderate ionic strength. At high ionic strength, colloidal particles will flocculate due to a secondary minimum, resulting in aggregates that are dense and easily redispersed. In contrast, nanoparticles stabilized by citric acid remain stable at high ionic strengths and therefore exist in solution as individual particles; this will contribute to their dispersion in the environment and the uptake of nanoparticles by mammalian cells.

Toxicogenomics: A New Paradigm for Nanotoxicity Evaluation

The wider applications of nanoparticles (NPs) has evoked a world-wide concern due to their possible risk of toxicity in humans and other organisms. Aggregation and accumulation of NPs into cell leads to their interaction with biological macromolecules including proteins, nucleic acids and cellular organelles, which eventually induce toxicological effects. Application of toxicogenomics to investigate molecular pathway-based toxicological consequences has opened new vistas in nanotoxicology research. Indeed, genomic approaches appeared as a new paradigm in terms of providing information at molecular levels and have been proven to be as a powerful tool for identification and quantification of global shifts in gene expression. Toxicological responses of NPs have been discussed in this chapter with the aim to provide a clear understanding of the molecular mechanism of NPs induced toxicity both in in vivo and in vitro test models.

Engineered Nickel Oxide Nanoparticle Causes Substantial Physicochemical Perturbation in Plants

Concentration of engineered nickel oxide nanoparticle (NiO-NP) in nature is on the rise, owing to large scale industrial uses, which have accreted the scope of its exposure to plants, the primary producers of the ecosystem. Though an essential micronutrient for the animal system, supported by numerous studies confirming its toxicity at higher dosages, nickel oxide is graded as a human carcinogen by WHO. A few studies do depict toxicity and bioaccumulation of nickel in plants; however, interaction of NiO-NP with plants is not well-elucidated. It is known that exposure to NiO-NP can incite stress response, leading to cytotoxicity and growth retardation in some plants, but a defined work on the intricate physicochemical cellular responses and genotoxic challenges is wanting. The present study was planned to explore cytotoxicity of NiO-NP in the model plant, Allium cepa L., its internalization in the tissue and concomitant furore created in the antioxidant enzyme system of the plant. The prospect of the NiO-NP causing genotoxicity was also investigated. Detailed assessments biochemical profiles and genotoxicity potential of NiO-NP on A. cepa L. was performed and extended to four of its closest economically important relatives, Allium sativum L., Allium schoenoprasum L., Allium porrum L., and Allium fistulosum L. Growing root tips were treated with seven different concentrations of NiO-NP suspension (10-500 mg L-1), with deionised distilled water as negative control and 0.4 mM EMS solution as positive control. Study of genotoxic endpoints, like, mitotic indices (MI), chromosomal aberrations (CAs), and chromosome breaks confirmed NiO-NP induced genotoxicity in plants, even at a very low dose (10 mg L-1). That NiO-NP also perturbs biochemical homeostasis, disrupting normal physiology of the cell, was confirmed through changes in state of lipid peroxidation malonaldehyde (MDA), as well as, in oxidation marker enzymes, like catalase (CAT), super oxide dismutase (SOD), and guiacol peroxidase (POD) activities. It was evident that increase in NiO-NP concentration led to decrease in MIs in all the study materials, concomitant with a spike of stress-alleviating, antioxidant enzymes-CAT, POD, SOD, and significant increase in MDA formation. Hence, it can be confirmed that NiO-NP should be treated as an environmental hazard.

Reduced ultrafine particle levels in São Paulo's atmosphere during shifts from gasoline to ethanol use

Despite ethanol’s penetration into urban transportation, observational evidence quantifying the consequence for the atmospheric particulate burden during actual, not hypothetical, fuel-fleet shifts, has been lacking. Here we analyze aerosol, meteorological, traffic, and consumer behavior data and find, empirically, that ambient number concentrations of 7–100-nm diameter particles rise by one-third during the morning commute when higher ethanol prices induce 2 million drivers in the real-world megacity of São Paulo to substitute to gasoline use (95% confidence intervals: +4,154 to +13,272 cm⁻³). Similarly, concentrations fall when consumers return to ethanol. Changes in larger particle concentrations, including US-regulated PM2.5, are statistically indistinguishable from zero. The prospect of increased biofuel use and mounting evidence on ultrafines’ health effects make our result acutely policy relevant, to be weighed against possible ozone increases. The finding motivates further studies in real-world environments. We innovate in using econometrics to quantify a key source of urban ultrafine particles.

The biofuel ethanol has been introduced into urban transportation in many countries. Here, by measuring aerosols in São Paulo, the authors find that high ethanol prices coincided with an increase in harmful nanoparticles by a third, as drivers switched from ethanol to cheaper gasoline, showing a benefit of ethanol.

Genotoxicity of citrate-coated silver nanoparticles to human keratinocytes assessed by the comet assay and cytokinesis blocked micronucleus assay

Silver nanoparticles (AgNPs) are widely used in industrial, cosmetic, and biomedical products, and humans are frequently exposed to these products through the skin. It is widely recognized that the characteristics of AgNPs (e.g., size, coating) may influence their cytotoxic effects, but their correlation with DNA damage and mitotic disorders remains poorly explored. In this study, human keratinocytes (HaCaT cell line) were exposed to well-characterized 30 nm AgNPs coated with citrate, and their effects on viability, DNA fragmentation (assessed by the comet assay), and micronuclei (MNi) induction (assessed by the cytokinesis-block micronucleus cytome assays, CBMN) were investigated. The results showed that 10 and 40 μg/mL AgNPs decreased cell proliferation and viability, and induced a significant genetic damage. This was observed by an increase of DNA amount in comet tail, which linearly correlated with dose and time of exposure. Also, cytostaticity (increase of mononucleated cells) and MNi rates increased in treated cells. In contrast, no significant changes were observed in nucleoplasmatic bridges (NPBs) or nuclear buds (NBUDs), although NBUDs tended to increase in all conditions and periods. The cytostatic effects on HaCaT cells were also shown by the decrease of their nuclear division index. Thus, both comet and CBMN assays supported the observation that citrate-AgNPs induced genotoxic effects on HaCaT cells. Considering that AgNPs are present in a vast number of consumer products and also in multiple nanomedicine skin applications and formulations, more research is needed to determine the properties that confer less toxicity of AgNPs to different cell lines.

Toxic Effects of Engineered Nanoparticles on Living Cells

Measuring toxic effects of engineered nanoparticles on living cells would require a deep understanding of themselves by the mean of their composition, physical and chemical properties and exposure concentrations. Actually, high exposure concentrations are needed to generate quantifiable effects and to perceive accumulation above background. This chapter presents an overview on the assessment about the toxic effects of engineered nanoparticles on living cells. It consists of three main sections starting with a brief introduction, the current state of engineered nanoparticles in the environment, physical and chemical properties of some important engineered nanoparticles such as “Ag, Au, ZnO, TiO2” and the target organ toxicity of the engineered nanoparticles in several biological organisms.

Where do uncertainties reside within environmental risk assessments? Expert opinion on uncertainty distributions for pesticide risks to surface water organisms

A reliable characterisation of uncertainties can aid uncertainty identification during environmental risk assessments (ERAs). However, typologies can be implemented inconsistently, causing uncertainties to go unidentified. We present an approach based on nine structured elicitations, in which subject-matter experts, for pesticide risks to surface water organisms, validate and assess three dimensions of uncertainty: its level (the severity of uncertainty, ranging from determinism to ignorance); nature (whether the uncertainty is epistemic or aleatory); and location (the data source or area in which the uncertainty arises). Risk characterisation contains the highest median levels of uncertainty, associated with estimating, aggregating and evaluating the magnitude of risks. Regarding the locations in which uncertainty is manifest, data uncertainty is dominant in problem formulation, exposure assessment and effects assessment. The comprehensive description of uncertainty described will enable risk analysts to prioritise the required phases, groups of tasks, or individual tasks within a risk analysis according to the highest levels of uncertainty, the potential for uncertainty to be reduced or quantified, or the types of location-based uncertainty, thus aiding uncertainty prioritisation during environmental risk assessments. In turn, it is expected to inform investment in uncertainty reduction or targeted risk management action.

Metallic nickel nanoparticles and their effect on the embryonic development of the sea urchin Paracentrotus lividus

The presence of nanoparticles in many industrial applications and daily products is making it nowadays crucial to assess their impact when exposed to the environment. Metallic nickel nanoparticles (Ni NPs) are of high industrial interest due to their ability to catalyze the reversible hydration of CO2 to carbonic acid at ambient conditions. We characterized metallic Ni NPs by XRD, HRTEM and EDS and determined the solubility of free nickel ions from 3 mg/L metallic Ni NPs in seawater by ICP-MS over 96 h, which was below 3%. Further, embryonic development of the sea urchin Paracentrotus lividus was investigated for 48 h in the presence of metallic Ni NPs (0.03 mg/L to 3 mg/L), but no lethal effects were observed. However, 3 mg/L metallic Ni NPs caused a size reduction similar to 1.2 mg/L NiCl2*6 H2O. The obtained results contribute to current studies on metallic Ni NPs and point to their consequences for the marine ecosystem.

Microglial cells (BV-2) internalize titanium dioxide (TiO2) nanoparticles: toxicity and cellular responses

Because of their whitening and photocatalytic effects, titanium dioxide nanoparticles (TiO2-NPs) are widely used in daily life. These NPs can be found in paints, plastics, papers, sunscreens, foods, medicines (pills), toothpastes, and cosmetics. However, the biological effect of TiO2-NPs on the human body, especially on the central nervous system, is still unclear. Many studies have demonstrated that the brain is one of the target organs in acute or chronic TiO2-NPs toxicity. The present study aimed to investigate the effect of TiO2-NPs at different concentrations (0.1 to 200 μg/mL) on murine microglial cells (BV-2) to assess their activity on cell growth and viability, as well as their neurotoxicity. Different parameters were measured: cell viability, cell proliferation and DNA content (SubG1 peak), mitochondrial depolarization, overproduction of reactive oxygen species (especially superoxide anions), and ultrastructural changes. Results showed that TiO2-NPs induced some cytotoxic effects with a slight inhibition of cell growth. Thus, at high concentrations, TiO2-NPs were not only able to inhibit cell adhesion but also enhanced cytoplasmic membrane permeability to propidium iodide associated with a loss of mitochondrial transmembrane potential and an overproduction of superoxide anions. No induction of apoptosis based on the presence of a SubG1 peak was detected. The microscopic observations also indicated that small groups of nanosized particles and micron-sized aggregates were engulfed by the BV-2 cells and sequestered as intracytoplasmic aggregates after 24-h exposure to TiO2-NPs. Altogether, our data show that the accumulation TiO2-NPs in microglial BV-2 cells favors mitochondrial dysfunctions and oxidative stress.

Chemically synthesized CdSe quantum dots inhibit growth of human lung carcinoma cells via ROS generation

Quantum dots (QDs), semiconducting materials have potential applications in the field of electronic and biomedical applications including cancer therapy. In present study, cadmium selenide (CdSe) QDs were synthesized by chemical method. Octadecene was used as non-coordinating solvent which facilitated the formation of colloidal solutions of nanoparticles. CdSe QDs were characterized by UV-vis spectrometer and transmission electron microscope (TEM). The size measured by TEM was varied between 2-5 nm depending upon temperature. The cytotoxic activity of QDs was monitored by MTT assay, nuclear condensation, ROS activity and DNA fragmentation assay on human lung epithelial A549 cell line. Cells were treated with different concentrations of varying size of CdSe QDs for 24 h. CdSe QDs induced significant (p < 0.05) dose dependent cytotoxicity and this was comparable to the sizes of particles. Smaller particles were more cytotoxic to the large particles. Fluorescence microscopic analysis revealed that QDs induced oxidative stress generating significant ROS level and consequently, induced nuclear condensation and DNA fragmentation. Study suggested the cytotoxicity of CdSe QDs via ROS generation and DNA fragmentation depending upon particles size.

Glucose availability determines silver nanoparticles toxicity in HepG2

Background

The increasing body of evidence suggest that nanomaterials toxicity is associated with generation of oxidative stress. In this paper we investigated the role of respiration in silver nanoparticles (AgNPs) generated oxidative stress and toxicity. Since cancer cells rely on glucose as the main source of energy supply, glucose availability might be an important determinant of NPs toxicity.

Methods

AgNPs of 20 nm nominal diameter were used as a model NPs. HepG2 cells were cultured in the media with high (25 mM) or low (5.5 mM) glucose content and treated with 20 nm AgNPs. AgNPs-induced toxicity was tested by neutral red assay. Generation of H₂O₂ in mitochondria was evaluated by use of mitochondria specific protein indicator HyPer-Mito. Expression of a 77 oxidative stress related genes was assessed by qPCR. The activity of antioxidant enzymes was estimated colorimetrically by dedicated methods in cell homogenates.

Results

AgNPs-induced dose-dependent generation of H₂O₂ and toxicity was observed. Toxicity of AgNPs towards cells maintained in the low glucose medium was significantly lower than the toxicity towards cells growing in the high glucose concentration. Scarceness of glucose supply resulted in upregulation of the endogenous antioxidant defence mechanisms that in turn alleviated AgNPs dependent ROS generation and toxicity.

Conclusion

Glucose availability can modify toxicity of AgNPs via elevation of antioxidant defence triggered by oxidative stress resulted from enhanced oxidative phosphorylation in mitochondria and associated generation of ROS. Presented results strengthen the idea of strong linkage between NPs toxicity and intracellular respiration and possibly other mitochondria dependent processes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-015-0132-2) contains supplementary material, which is available to authorized users.

Accumulation of atmospheric deposition of As, Cd and Pb by bush bean plants

Bush bean (Phaseolus vulgaris) was exposed to atmospheric deposition of As, Cd and Pb in a polluted and a reference area. The atmospheric deposition of these elements was significantly related to the concentrations in leaves, stems and pods at green harvest. Surprisingly there was also a clear relation for As and Pb in the seeds at dry harvest, even though these seeds were covered by the husks. Root uptake of accumulated atmospheric deposits was not likely in such a short term experiment, as confirmed by the fact that soil pore water analysis did not reveal significant differences in trace element concentrations in the different exposure areas. For biomonitoring purposes, the leaves of bush bean are the most suitable, but also washed or unwashed pods can be used. This means that the obtained relationships are suitable to estimate the transfer of airborne trace elements in the food chain via bush bean.

Nanoparticles in food. Epigenetic changes induced by nanomaterials and possible impact on health

Disturbed epigenetic mechanisms, which developmentally regulate gene expression via modifications to DNA, histone proteins, and chromatin, have been hypothesized to play a key role in many human diseases. Recently it was shown that engineered nanoparticles (NPs), that already have a wide range of applications in various fields including food production, could dramatically affect epigenetic processes, while their ability to induce diseases remains poorly understood. Besides the obvious benefits of the new technologies, it is critical to assess their health effects before proceeding with industrial production. In this article, after surveying the applications of NPs in food technology, we review recent advances in the understanding of epigenetic pathological effects of NPs, and discuss their possible health impact with the aim of avoiding potential health risks posed by the use of nanomaterials in foods and food-packaging.

The effect of nanoparticles on plankton dynamics: a mathematical model

A simple modification of the Rosenzweig-MacArthur predator (zooplankton)-prey (phytoplankton) model with the interference of the predators by adding the effect of nanoparticles is proposed and analyzed. It is assumed that the effect of these particles has a potential to reduce the maximum physiological per-capita growth rate of the prey. The dynamics of nanoparticles is assumed to follow a simple Lotka-Volterra uptake term. Our study suggests that nanoparticle induce growth suppression of phytoplankton population can destabilize the system which leads to limit cycle oscillation. We also observe that if the contact rate of nanoparticles and phytoplankton increases, then the equilibrium densities of phytoplankton as well as zooplankton decrease. Furthermore, we observe that the depletion/removal of nanoparticles from the aquatic system plays a crucial role for the stable coexistence of both populations. Our investigation with various types of functional response suggests that Beddington functional response is the most appropriate representation of the interaction of phytoplankton-nanoparticles in comparison to other widely used functional responses.

Engineered nanomaterials in food: implications for food safety and consumer health

From the current state-of-the-art, it is clear that nanotechnology applications are expected to bring a range of benefits to the food sector aiming at providing better quality and conservation. In the meantime, a growing number of studies indicate that the exposure to certain engineered nanomaterials (ENMs) has a potential to lead to health complications and that there is a need for further investigations in order to unravel the biological outcomes of nanofood consumption. In the current review, we summarize the existing data on the (potential) use of ENMs in the food industry, information on the toxicity profiles of the commonly applied ENMs, such as metal (oxide) nanoparticles (NPs), address the potential food safety implications and health hazards connected with the consumption of nanofood. A number of health complications connected with the human exposure to ENMs are discussed, demonstrating that there is a real basis for the arisen concern not only connected with the gut health, but also with the potency to lead to systemic toxicity. The toxicological nature of hazard, exposure levels and risk to consumers from nanotechnology-derived food are on the earliest stage of investigation and this review also highlights the major gaps that need further research and regulation.

Interference of CuO nanoparticles with metal homeostasis in hepatocytes under sub-toxic conditions

Copper oxide nanoparticles (CuO-NP) were studied for their toxicity and mechanism of action on hepatocytes (HepG2), in relation to Cu homeostasis disruption. Indeed, hepatocytes, in the liver, are responsible for the whole body Cu balance and should be a major line of defence in the case of exposure to CuO-NP. We investigated the early responses to sub-toxic doses of CuO-NP and compared them to equivalent doses of Cu added as salt to see if there is a specific nano-effect related to Cu homeostasis in hepatocytes. The expression of the genes encoding the Cu-ATPase ATP7B, metallothionein 1X, heme oxygenase 1, heat shock protein 70, superoxide dismutase 1, glutamate cysteine ligase modifier subunit, metal responsive element-binding transcription factor 1 and zinc transporter 1 was analyzed by qRT-PCR. These genes are known to be involved in response to Cu, Zn and/or oxidative stresses. Except for MTF1, ATP7B and SOD1, we clearly observed an up regulation of these genes expression in CuO-NP treated cells, as compared to CuCl2. In addition, ATP7B trafficking from the Golgi network to the bile canaliculus membrane was observed in WIF-B9 cells, showing a need for Cu detoxification. This shows an increase in the intracellular Cu concentration, probably due to Cu release from endosomal CuO-NP solubilisation. Our data show that CuO-NP enter hepatic cells, most probably by endocytosis, bypassing the cellular defence mechanism against Cu, thus acting as a Trojan horse. Altogether, this study suggests that sub-toxic CuO-NP treatments induce successively a Cu overload, a Cu-Zn exchange on metallothioneins and MTF1 regulation on both Cu and Zn homeostasis.

Fabricated nanoparticles: current status and potential phytotoxic threats

Nanotechnology offers unique attributes to various industrial and consumer sectors, and has become a topic of high interest to scientific communities across the world. Our society has greatly benefitted from nanotechnology already, in that many products with novel properties and wide applicability have been developed and commercialized. However, the increased production and use of nanomaterials have raised concerns about the environmental fate and toxicological implications of nanoparticles and nanomaterials. Research has revealed that various nanomaterials may be hazardous to living organisms. Among biota, plants are widely exposed to released nanomaterials and are sensitive to their effects. The accumulation of nannmaterials in the environment is a potential threat, not only because of potential damage to plants hut also because nanoparticles may enter the food chain. Although the literature that addresses the safety of nanoproducts is growing, little is known about the mechanisms by which these materials produce toxicity on natural species, including humans. In this paper, we have reviewed the literature relevant to what phytotoxic impact fabricated nanoparticles (e.g., carbon nanotubes, metallic and metal oxide nanoparticles, and certain other nanomaterials) have on plants. Nanoparticles produce several effects on plant physiology and morphology. Nanoparticles are known to affect root structure, seed germination, and cellular metabolism. Nanoparticles inhibit growth, induce oxidative stress, morphogenetic abnormalities and produce clastogenic disturbances in several plant species. The size, shape and surface coating of NPs play an important role in determining their level of toxicity. Of course, the dose, route of administration, type of dispersion media, and environmental exposure also contribute to how toxic nanoparticles are to plants. Currently, nanotoxicity studies are only in their initial phases of development and more research will be required to identify the actual threat nanoproducts pose to the plant system. To date, data show that there is a large variation in the phytotoxicity caused by different NPs. Moreover, the studies conducted thus far have mostly relied on microscopy to detect effects. Studies that incorporate measures and analyses undertaken with more modern tools are needed. Among new data that are most urgently needed on NPs is how fabricated NPs behave once released into the environment, and how exposure to them may affect plant resistance, metabolic pathways, and plant genetic responses. In this review, we have attempted to collect, present and summarize recent findings from the literature on nanoparticle toxicity in plants. To strengthen the analysis, we propose a scheme for accessing NP toxicity. We also recommend how the potential challenges presented by increased production and release of NPs should be addressed. It is our belief and recommendation that every nanomaterial-based product be subjected to appropriate toxicity and associated assessment before being commercialized.