Ecotoxicological investigation of CeO(2) and TiO(2) nanoparticles on the soil nematode Caenorhabditis elegans using gene expression, growth, fertility, and survival as endpoints

Environmental applications and risks of engineered nanomaterials in removing petroleum oil in soil

Oil-contaminated soil posed serious threats to the ecosystems and human health. The unique and tunable properties of engineered nanomaterials (ENMs) enable new technologies for removing and repairing oil-contaminated soil. However, few studies systematically examined the linkage between the change of physicochemical properties and the removal efficiency and environmental functions (e.g., potential risk) of ENMs, which is vital for understanding the ENMs environmental sustainability and utilization as a safety product. Thus, this review briefly summarized the environmental applications of ENMs to removing petroleum oil from complex soil systems: Theoretical and practical fundamentals (e.g., excellent physicochemical properties, environmental stability, controlled release, and recycling technologies), and various ENMs (e.g., iron-based, carbon-based, and metal oxides nanomaterials) remediation case studies. Afterward, this review highlights the removing mechanism (e.g., adsorption, photocatalysis, oxidation/reduction, biodegradation) and the impact factor (e.g., nanomaterials species, natural organic matter, and soil matrix) of ENMs during the remediation process in soil ecosystems. Both positive and negative effects of ENMs on terrestrial organisms have been identified, which are mainly derived from their diverse physicochemical properties. In linking nanotechnology applications for repairing oil-contaminated soil back to the physical and chemical properties of ENMs, this critical review aims to raise the research attention on using ENMs as a fundamental guide or even tool to advance soil treatment technologies.

Evaluation of the effects of zinc oxide (ZnO NPs) nanoparticles synthesized by green synthesis on Caenorhabditis elegans

In recent years, the rapid development of nanotechnology has caused the products obtained with this technology to be used more daily. Information on the effects of these products, which provide great advantages in every respect, on human health and the environment is insufficient. It has been suggested that these nanoparticles may have toxic effects on living things, mostly in animal experiments and cell cultures. In this paper, the organism Caenorhabditis elegans (C. elegans), which contains a genome and biochemical ways highly similar to humans, is used to understand and reveal the metabolism of Zinc oxide nanoparticles (ZnO NPs) toxicological effects. The toxicological effects of ZnO NPs on C. elegans organisms were investigated and the results were evaluated in terms of environment and human health. C. elegans was exposed to commercial ZnO NPs and green synthesized ZnO NPs from Olea europaea (olive tree, OLE). LC50 values were determined by probit analysis (green synthesized ZnO NP LC5024h = 84.97 mg/L, LC5072h = 33.27 mg/L, commercial ZnO NPs LC5024h = 5.75 mg/L, LC5072h = 1.91 mg/L). When the survival times of C. elegans were evaluated by the Kaplan-Meier method, it was seen that commercial ZnO NPs were more toxic than green synthesized ZnO NPs. In MTT tests, it was clearly seen that commercial ZnO NPs and green synthesized ZnO NPs entered the cell and caused different cytotoxicity. While there was a difference between control and 0.5, 2.5, 5, 10, 25, and 50 mg/L doses in commercial ZnO NP applications, there were significant differences between control and 25, 50 mg/L concentrations in green synthesized ZnO NP applications.

Evaluating the adverse effects and mechanisms of nanomaterial exposure on longevity of C. elegans: A literature meta-analysis and bioinformatics analysis of multi-transcriptome data

Exposure to large-size particulate air pollution (PM2.5 or PM10) has been reported to increase risks of aging-related diseases and human death, indicating the potential pro-aging effects of airborne nanomaterials with ultra-fine particle size (which have been widely applied in various fields). However, this hypothesis remains inconclusive. Here, a meta-analysis of 99 published literatures collected from electronic databases (PubMed, EMBASE and Cochrane Library; from inception to June 2023) was performed to confirm the effects of nanomaterial exposure on aging-related indicators and molecular mechanisms in model animal C. elegans. The pooled analysis by Stata software showed that compared with the control, nanomaterial exposure significantly shortened the mean lifespan [standardized mean difference (SMD) = -2.30], reduced the survival rate (SMD = -4.57) and increased the death risk (hazard ratio = 1.36) accompanied by upregulation of ced-3, ced-4 and cep-1, while downregulation of ctl-2, ape-1, aak-2 and pmk-1. Furthermore, multi-transcriptome data associated with nanomaterial exposure were retrieved from Gene Expression Omnibus (GSE32521, GSE41486, GSE24847, GSE59470, GSE70509, GSE14932, GSE93187, GSE114881, and GSE122728) and bioinformatics analyses showed that pseudogene prg-2, mRNAs of abu, car-1, gipc-1, gsp-3, kat-1, pod-2, acdh-8, hsp-60 and egrh-2 were downregulated, while R04A9.7 was upregulated after exposure to at least two types of nanomaterials. Resveratrol (abu, hsp-60, pod-2, egrh-2, acdh-8, gsp-3, car-1, kat-1, gipc-1), naringenin (kat-1, egrh-2), coumestrol (egrh-2) or swainsonine/niacin/ferulic acid (R04A9.7) exerted therapeutic effects by reversing the expression levels of target genes. In conclusion, our study demonstrates the necessity to use phytomedicines that target hub genes to delay aging for populations with nanomaterial exposure.

Oxidative stress and potential effects of metal nanoparticles: A review of biocompatibility and toxicity concerns

Metal nanoparticles (M-NPs) have garnered significant attention due to their unique properties, driving diverse applications across packaging, biomedicine, electronics, and environmental remediation. However, the potential health risks associated with M-NPs must not be disregarded. M-NPs' ability to accumulate in organs and traverse the blood-brain barrier poses potential health threats to animals, humans, and the environment. The interaction between M-NPs and various cellular components, including DNA, multiple proteins, and mitochondria, triggers the production of reactive oxygen species (ROS), influencing several cellular activities. These interactions have been linked to various effects, such as protein alterations, the buildup of M-NPs in the Golgi apparatus, heightened lysosomal hydrolases, mitochondrial dysfunction, apoptosis, cell membrane impairment, cytoplasmic disruption, and fluctuations in ATP levels. Despite the evident advantages M-NPs offer in diverse applications, gaps in understanding their biocompatibility and toxicity necessitate further research. This review provides an updated assessment of M-NPs' pros and cons across different applications, emphasizing associated hazards and potential toxicity. To ensure the responsible and safe use of M-NPs, comprehensive research is conducted to fully grasp the potential impact of these nanoparticles on both human health and the environment. By delving into their intricate interactions with biological systems, we can navigate the delicate balance between harnessing the benefits of M-NPs and minimizing potential risks. Further exploration will pave the way for informed decision-making, leading to the conscientious development of these nanomaterials and safeguarding the well-being of society and the environment.

Toxicity of Three Optical Brighteners: Potential Pharmacological Targets and Effects on Caenorhabditis elegans

Optical brighteners (OBs) have become an integral part of our daily lives and culture, with a growing number of applications in various fields. Most industrially produced OBs are derived from stilbene, which has been found in environmental matrices. The main objectives for this work are as follows: first, to identify protein targets for DAST, FB-28, and FB-71, and second, to assess their effects in some behaviors physiologic of Caenorhabditis elegans. To achieve the first objective, each OB was tested against a total of 844 human proteins through molecular docking using AutoDock Vina, and affinities were employed as the main criteria to identify potential target proteins for the OB. Molecular dynamics simulations took and validated the best 25 docking results from two protein databases. The highest affinity was obtained for the Hsp70-1/DAST, CD40 ligand/FB-71, and CD40 ligand/FB-28 complexes. The possible toxic effects that OBs could cause were evaluated using the nematode C. elegans. The lethality, body length, locomotion, and reproduction were investigated in larval stage L1 or L4 of the wild-type strain N2. In addition, transgenic green fluorescent protein (GFP) strains were employed to estimate changes in relative gene expression. The effects on the inhibition of growth, locomotion, and reproduction of C. elegans nematodes exposed to DAST, FB-71, and FB-28 OBs were more noticeable with respect to lethality. Moreover, an interesting aspect in OB was increased the expression of gpx-4 and sod-4 genes associated with oxidative stress indicating a toxic response related to the generation of reactive oxygen species (ROS). In all cases, a clear concentration-response relationship was observed. It is of special attention that the use of OBs is increasing, and their different sources, such as detergents, textiles, plastics, and paper products, must also be investigated to characterize the primary emissions of OBs to the environment and to develop an adequate regulatory framework.

Subacute toxicity and endocrine-disrupting effects of Fe2O3, ZnO, and CeO2 nanoparticles on amphibian metamorphosis

This study evaluated the potential toxic and endocrine-disrupting effects of sublethal concentrations of Fe2O3, CeO2 and ZnO nanoparticles (NPs) on amphibian metamorphosis. Tadpoles were exposed to several NPs concentrations, reaching a maximum of 1000 µg/L, for up to 21 days according to the amphibian metamorphosis assay (AMA). Some standard morphological parameters, such as developmental stage (DS), hind limb length (HLL), snout-to-vent length (SVL), wet body weight (WBW), and as well as post-exposure lethality were recorded in exposed organisms on days 7 and 21 of the bioassay. Furthermore, triiodothyronine (T3), thyroxine (T4) and malondialdehyde (MDA) levels and the activities of glutathione S-transferases (GST), glutathione reductase (GR), catalase (CAT), carboxylesterase (CaE), and acetylcholinesterase (AChE) were determined in exposed tadpoles as biomarkers. The results indicate that short-term exposure to Fe2O3 NPs leads to toxic effects, both exposure periods cause toxic effects and growth inhibition for ZnO NPs, while short-term exposure to CeO2 NPs results in toxic effects and long-term exposure causes endocrine-disrupting effects. The responses observed after exposure to the tested NPs during amphibian metamorphosis suggest that they may have ecotoxicological effects and their effects should be monitored through field studies.

Characterization of oxidative damage induced by nanoparticles via mechanism-driven machine learning approaches

The wide application of TiO₂-based engineered nanoparticles (nTiO₂) inevitably led to release into aquatic ecosystems. Importantly, increasing studies have emphasized the high risks of nTiO₂ to coastal environments. Bivalves, the representative benthic filter feeders in coastal zones, acted as important roles to assess and monitor the toxic effects of nanoparticles. Oxidative damage was one of the main toxic mechanisms of nTiO₂ on bivalves, but the experimental variables/nanomaterial characteristics were diverse and the toxicity mechanism was complex. Therefore, it was very necessary to develop machine learning model to characterize and predict the potential toxicity. In this study, thirty-six machine learning models were built by nanodescriptors combined with six machine learning algorithms. Among them, random forest (RF) - catalase (CAT), k-neighbors classifier (KNN) - glutathione peroxidase (GPx), neural networks - multilayer perceptron (ANN) - glutathione s-transferase (GST), random forest (RF) - malondialdehyde (MDA), random forest (RF) - reactive oxygen species (ROS), and extreme gradient boosting decision tree (XGB) - superoxide dismutase (SOD) models performed good with high accuracy and balanced accuracy for both training sets and external validation sets. Furthermore, the best model revealed the predominant factors (exposure concentration, exposure periods, and exposure matrix) influencing the oxidative stress induced by nTiO₂. These results showed that high exposure concentrations and short exposure-intervals tended to cause oxidative damage to bivalves. In addition, gills and digestive glands could be vulnerable to nTiO₂-induced oxidative damage as tissues/organs differences were the important factors controlling MDA activity. This study provided insights into important nano-features responsible for the different indicators of oxidative stress and thereby extended the application of machine learning approaches in toxicological assessment for nanoparticles.

Caenorhabditis elegans: a model organism in the toxicity assessment of environmental pollutants

The unfavorable effects of environmental pollutants are becoming increasingly evident. In recent years, Caenorhabditis elegans (C. elegans) has been used as a powerful terrestrial model organism for environmental toxicity studies owing to its various advantages, including ease of culture, short lifespan, small size, transparent body, and well-characterized genome. In vivo bioassays and field studies can analyze and evaluate various toxic effects of the toxicants on the model organism, while emerging technologies allow profound insights into molecular disturbances underlying the observed phenotypes. In this review, we discuss the applications of C. elegans as a model organism in environmental toxicity studies and delineate apical assays such as lifespan, growth rate, reproduction, and locomotion, which are widely used in toxicity evaluation. In addition to phenotype assays, a comprehensive understanding of the toxic mode of action and mechanism can be achieved through a highly sensitive multi-omics approach, including the expression levels of genes and endogenous metabolites. Recent studies on environmental toxicity using these approaches have been summarized. This review highlights the practicality and advantages of C. elegans in evaluating the toxicity of environmental pollutants and presents the findings of recent toxicity studies performed using this model organism. Finally, we propose crucial technical considerations to escalate the appropriate use of C. elegans in examining the toxic effects of environmental pollutants.

Cerium oxide thin films: synthesis, characterization, photocatalytic activity and influence on microbial growth

The resistance of surfaces to biofouling remains a significant advantage for optical devices working in natural conditions, increasing their lifetime and reducing maintenance costs. This paper reports on the functionalities of transparent CeO₂ thin films with thicknesses between 25 and 600 nm deposited by reactive magnetron sputtering on the glass substrate. The CeO₂ photocatalytic performance exhibited an efficiency of 30% on imidacloprid degradation under 6 h of UV radiation and increased linearly with the irradiation time, suggesting a complete degradation within 48 h. The films did not alter the growth rate of the green algae Chlorella vulgaris after 72 h short-term exposure. The tested CeO₂ films proved to efficiently inhibit with high efficiency the Staphylococcus aureus biofilms and planktonic growth (reducing the counts of bacterial cells by 2 to 8 logs), demonstrating the promising potential of these materials for obtaining antimicrobial and antibiofilm surfaces, with broad applications for the biomedical, ecological and industrial fields.

CYP35 family in Caenorhabditis elegans biological processes: fatty acid synthesis, xenobiotic metabolism, and stress responses

With more than 80 cytochrome P450 (CYP) encoding genes found in the nematode Caenorhabditis elegans (C. elegans), the cyp35 genes are one of the important genes involved in many biological processes such as fatty acid synthesis and storage, xenobiotic stress response, dauer and eggshell formation, and xenobiotic metabolism. The C. elegans CYP35 subfamily consisted of A, B, C, and D, which have the closest homolog to human CYP2 family. C. elegans homologs could answer part of the hunt for human disease genes. This review aims to provide an overview of CYP35 in C. elegans and their human homologs, to explore the roles of CYP35 in various C. elegans biological processes, and how the genes of cyp35 upregulation or downregulation are influenced by biological processes, upon exposure to xenobiotics or changes in diet and environment. The C. elegans CYP35 gene expression could be upregulated by heavy metals, pesticides, anti-parasitic and anti-chemotherapeutic agents, polycyclic aromatic hydrocarbons (PAHs), nanoparticles, drugs, and organic chemical compounds. Among the cyp35 genes, cyp-35A2 is involved in most of the C. elegans biological processes regulation. Further venture of cyp35 genes, the closest homolog of CYP2 which is the largest family of human CYPs, may have the power to locate cyps gene targets, discovery of novel therapeutic strategies, and possibly a successful medical regime to combat obesity, cancers, and cyps gene-related diseases.

Multiomics analyses uncover nanoceria triggered oxidative injury and nutrient imbalance in earthworm Eisenia fetida

The toxic stress caused by nanoceria remains vague owing to the limited efforts scrutinizing its molecular mechanisms. Herein, we investigated the impacts of nanoceria on earthworm Eisenia fetida, at the molecular level using the multiomics-based profiling approaches (transcriptomics, metabolomics, and 16 S rRNA sequencing). Nanoceria (50 and 500 mg/kg) significantly increased the contents of malondialdehyde (MDA), Fe, and K in worms, suggesting oxidative injury and nutrient imbalance. This was corroborated by the transcriptomic and metabolomic analyses. Nanoceria decreased the levels of certain genes and metabolites associated with glycerolipid and glycerophospholipid metabolisms, suggesting the production of reactive oxygen species and subsequent oxidative stress. Additionally, the ABCD3 gene belonging to ABC transporter family was upregulated, facilitating Fe uptake by worms. Moreover, the higher contents of MDA, Fe, and K after exposure were tightly associated with the imbalanced intestinal flora. Specifically, a higher relative abundance of Actinobacteriota and a lower relative abundance of Proteobacteria and Patescibacteria were induced. This study, for the first time, revealed that nanoceria at nonlethal levels caused oxidative stress and nutrient imbalance of earthworms from the perspective of genes, metabolites, and gut microbiome perturbations, and also established links between the gut microbiome and the overall physiological responses of the host.

Agri-Nanotechnology and Tree Nanobionics: Augmentation in Crop Yield, Biosafety, and Biomass Accumulation

Nanomaterials (NMs) are the leading edge as an amazing class of materials that consists of at least one dimension in the range of 1–100 nm. NMs can be made with exceptional magnetic, electrical, and catalytic properties different from their bulk counterparts. We summarized unique features of NMs, their synthesis, and advances in agri-nanotechnology and cutting-edge nanobionics. The review describes advances in NMs including their applications, dosimetry to ensure biosafety, remote sensing of agro-forestry fields, nanofertilizers, and nanopesticides, and avoid post-harvest losses, gene delivery, and nanobionics. Tree nanobionics has enabled the synthesis and delivery of nanosensors, which enhance the rate of photosynthesis, detection of pathogens, and poisonous residues to ensure biosafety and biomass accumulation. Finally, we conclude by discussing challenges, future perspectives, and agro-ecological risks of using NMs.

Synchrotron XRF Analysis Identifies Cerium Accumulation Colocalized with Pharyngeal Deformities in CeO2 NP-Exposed Caenorhabditis elegans

A combination of synchrotron radiation-based elemental imaging, in vivo redox status analysis, histology, and toxic responses was used to investigate the uptake, biodistribution, and adverse effects of Ce nanoparticles (CeO₂ NP; 10 nm; 0.5-34.96 mg Ce L^-1) or Ce(NO₃)₃ (2.3-26 mg Ce L^-1) in Caenorhabditis elegans. Elemental mapping of the exposed nematodes revealed Ce uptake in the alimentary canal prior to depuration. Retention of CeO₂ NPs was low compared to that of Ce(NO₃)₃ in depurated individuals. X-ray fluorescence (XRF) mapping showed that Ce translocation was confined to the pharyngeal valve and foregut. Ce(NO₃)₃ exposure significantly decreased growth, fertility, and reproduction, caused slightly reduced fecundity. XRF mapping and histological analysis revealed severe tissue deformities colocalized with retained Ce surrounding the pharyngeal valve. Both forms of Ce activated the sod-1 antioxidant defense, particularly in the pharynx, whereas no significant effects on the cellular redox balance were identified. The CeO₂ NP-induced deformities did not appear to impair the pharyngeal function or feeding ability as growth effects were restricted to Ce(NO₃)₃ exposure. The results demonstrate the utility of integrated submicron-resolution SR-based XRF elemental mapping of tissue-specific distribution and adverse effect analysis to obtain robust toxicological evaluations of metal-containing contaminants.

A New Look at the Effects of Engineered ZnO and TiO2 Nanoparticles: Evidence from Transcriptomics Studies

Titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles (NPs) have attracted a great deal of attention due to their excellent electrical, optical, whitening, UV-adsorbing and bactericidal properties. The extensive production and utilization of these NPs increases their chances of being released into the environment and conferring unintended biological effects upon exposure. With the increasingly prevalent use of the omics technique, new data are burgeoning which provide a global view on the overall changes induced by exposures to NPs. In this review, we provide an account of the biological effects of ZnO and TiO2 NPs arising from transcriptomics in in vivo and in vitro studies. In addition to studies on humans and mice, we also describe findings on ecotoxicology-related species, such as Danio rerio (zebrafish), Caenorhabditis elegans (nematode) or Arabidopsis thaliana (thale cress). Based on evidence from transcriptomics studies, we discuss particle-induced biological effects, including cytotoxicity, developmental alterations and immune responses, that are dependent on both material-intrinsic and acquired/transformed properties. This review seeks to provide a holistic insight into the global changes induced by ZnO and TiO2 NPs pertinent to human and ecotoxicology.

Cytochromes P450 of Caenorhabditis elegans: Implication in Biological Functions and Metabolism of Xenobiotics

Caenorhabditis elegans is an important model used for many aspects of biological research. Its genome contains 76 genes coding for cytochromes P450 (P450s), and few data about the biochemical properties of those P450s have been published so far. However, an increasing number of articles have appeared on their involvement in the metabolism of xenobiotics and endobiotics such as fatty acid derivatives and steroids. Moreover, the implication of some P450s in various biological functions of C. elegans, such as survival, dauer formation, life span, fat content, or lipid metabolism, without mention of the precise reaction catalyzed by those P450s, has been reported in several articles. This review presents the state of our knowledge about C. elegans P450s.

Arrestin-Coding Genes Regulate Endocytosis, Sporulation, Pathogenicity, and Stress Resistance in Arthrobotrys oligospora

Arrestins are a family of scaffold proteins that play a crucial role in regulating numerous cellular processes, such as GPCR signaling. The Arthrobotrys oligospora arrestin family contains 12 members, which have highly conserved N-terminal and C-terminal domains. In the presence of ammonia, A. oligospora can change its lifestyle from saprotrophic to carnivorous. During this transition, the expression pattern of arrestin-coding (AoArc) genes was markedly upregulated. Therefore, we disrupted seven AoArc genes from A. oligospora to identify their functions. Although individual arrestin mutant strains display similar pathogenesis, phenotypes, and stress resistance, the fundamental data on the roles of AoArc genes in A. oligospora are obtained in this study. Membrane endocytosis in AoArc mutants was significantly reduced. Meanwhile, the capacity of trap device formation against nematodes and ammonia was impaired due to AoArc deletions. We also found that AoArc genes could regulate conidial phenotypes, cell nuclear distribution, pH response, and stress resistance. Results of qRT-PCR assays revealed that sporulation-regulated genes were affected after the deletion of AoArc genes. In particular, among the 12 arrestins, AoArc2 mediates pH signaling in the fungus A. oligospora. Notably, combined with the classical paradigm of arrestin–GPCR signal transduction, we suggest that arrestin-regulated trap formation in A. oligospora may be directly linked to the receptor endocytosis pathway.

Moroccan Bee Bread Improves Biochemical and Histological Changes of the Brain, Liver, and Kidneys Induced by Titanium Dioxide Nanoparticles

Titanium dioxide nanoparticles (TiO2) were used in various fields such as food industry, cosmetics, medicine, and agriculture. Despite the many advantages of nanotechnology, the adverse effects of nanoparticles are inevitable. The present study was conducted to evaluate the protective effect of bee bread on titanium dioxide (TiO2) nanoparticle toxicity. Male rats were randomly divided into four groups: Group 1 received daily by gavage (10 mL/kg bw) of distilled water, Group 2 received bee bread ethanolic extract (100 mg/kg bw), Group 3 received TiO2 (100 mg/kg bw) and distilled water (10 mL/kg bw), and Group 4 received TiO2 (100 mg/kg bw) and bee bread ethanolic extract (100 mg/kg bw). All treatments were given daily by gavage during 30 days. At the end of the experiment period, blood samples were collected to analyze fasting blood glucose, lipid profile (TC, TG, LDL-C, HDL-C, and VLDL-C), liver enzymes (AST, ALT, and LDH), total protein, urea, albumin, creatinine, sodium, potassium, and chloride ions. In addition, histological examinations of the kidneys, liver, and brain were investigated. The results showed that the subacute administration of TiO2 alone (100 mg/kg bw) had induced hyperglycemia (309 ± 5 mg/dL) and elevation of hepatic enzyme levels, accompanied by a change in both lipid profile and renal biomarkers as well as induced congestion and dilatation in the hepatic central vein and congestion in kidney and brain tissues. However, the cotreatment with bee bread extract restored these biochemical parameters and attenuated the deleterious effects of titanium nanoparticles on brain, liver, and kidney functions which could be due to its rich content on functional molecules. The findings of this paper could make an important contribution to the field of using bee bread as a detoxifying agent against titanium dioxide nanoparticles and other xenobiotics.

Surface Properties and Environmental Transformations Controlling the Bioaccumulation and Toxicity of Cerium Oxide Nanoparticles: A Critical Review

Increasing production and utilization of cerium oxide nanoparticles (CNPs) in recent years have raised wide concerns about their toxicity. Numerous studies have been conducted to reveal the toxicity of CNPs, but the results are sometimes contradictory. In this review, the most important factors in mediating CNPs toxicity are discussed, including (1) the roles of physicochemical properties (size, morphology, agglomeration condition, surface charge, coating and surface valence state) on CNPs toxicity; (2) the phase transfer and transformation process of CNPs in various aqueous, terrestrial, and airborne environments; and (3) reductive dissolution of CNPs core and their chemical reactions with phosphate, sulfate/S^2-, and ferrous ions. The physicochemical properties play key roles in the interactions of CNPs with organisms and consequently their environmental transformations, reactivity and toxicity assessment. Also, the speciation transformations of CNPs caused by reactions with (in)organic ligands in both environmental and biological systems would further alter their fate, transport, and toxicity potential. Thus, the toxicity mechanisms are proposed based on the physical damage of direct adsorption of CNPs onto the cell membrane and chemical inhibition (including oxidative stress and interaction of CNPs with biomacromolecules). Finally, the current knowledge gaps and further research needs in identifying the toxicological risk factors of CNPs under realistic environmental conditions are highlighted, which might improve predictions about their potential environmental influences. This review aims to provide new insights into cost-effectiveness of control options and management practices to prevent environmental risks from CNPs exposure.

Recent Developments in the Application of Nanomaterials in Agroecosystems

Nanotechnology implies the scientific research, development, and manufacture, along with processing, of materials and structures on a nano scale. Presently, the contamination of metalloids and metals in the soil has gained substantial attention. The consolidation of nanomaterials and plants in ecological management has received considerable research attention because certain nanomaterials could enhance plant seed germination and entire plant growth. Conversely, when the nanomaterial concentration is not properly controlled, toxicity will definitely develop. This paper discusses the role of nanomaterials as: (1) nano-pesticides (for improving the plant resistance against the biotic stress); and (2) nano-fertilizers (for promoting the plant growth by providing vital nutrients). This review analyzes the potential usages of nanomaterials in agroecosystem. In addition, the adverse effects of nanomaterials on soil organisms are discussed. We mostly examine the beneficial effects of nanomaterials such as nano-zerovalent iron, iron oxide, titanium dioxide, nano-hydroxyapatite, carbon nanotubes, and silver- and copper-based nanomaterials. Some nanomaterials can affect the growth, survival, and reproduction of soil organisms. A change from testing/using nanomaterials in plants for developing nanomaterials depending on agricultural requirements would be an important phase in the utilization of nanomaterials in sustainable agriculture. Conversely, the transport as well as ecological toxicity of nanomaterials should be seriously examined for guaranteeing its benign usage in agriculture.

Measurement of CeO2 Nanoparticles in Natural Waters Using a High Sensitivity, Single Particle ICP-MS

As the production and use of cerium oxide nanoparticles (CeO₂ NPs) increases, so does the concern of the scientific community over their release into the environment. Single particle inductively coupled plasma mass spectrometry is emerging as one of the best techniques for NP detection and quantification; however, it is often limited by high size detection limits (SDL). To that end, a high sensitivity sector field ICP-MS (SF-ICP-MS) with microsecond dwell times (50 µs) was used to lower the SDL of CeO₂ NPs to below 4.0 nm. Ag and Au NPs were also analyzed for reference. SF-ICP-MS was then used to detect CeO₂ NPs in a Montreal rainwater at a concentration of (2.2 ± 0.1) × 10⁸ L⁻¹ with a mean diameter of 10.8 ± 0.2 nm; and in a St. Lawrence River water at a concentration of ((1.6 ± 0.3) × 10⁹ L⁻¹) with a higher mean diameter (21.9 ± 0.8 nm). SF-ICP-MS and single particle time of flight ICP-MS on Ce and La indicated that 36% of the Ce-containing NPs detected in Montreal rainwater were engineered Ce NPs.

Are Titania Photocatalysts and Titanium Implants Safe? Review on the Toxicity of Titanium Compounds

Titanium and its compounds are broadly used in both industrial and domestic products, including jet engines, missiles, prostheses, implants, pigments, cosmetics, food, and photocatalysts for environmental purification and solar energy conversion. Although titanium/titania-containing materials are usually safe for human, animals and environment, increasing concerns on their negative impacts have been postulated. Accordingly, this review covers current knowledge on the toxicity of titania and titanium, in which the behaviour, bioavailability, mechanisms of action, and environmental impacts have been discussed in detail, considering both light and dark conditions. Consequently, the following conclusions have been drawn: (i) titania photocatalysts rarely cause health and environmental problems; (ii) despite the lack of proof, the possible carcinogenicity of titania powders to humans is considered by some authorities; (iii) titanium alloys, commonly applied as implant materials, possess a relatively low health risk; (iv) titania microparticles are less toxic than nanoparticles, independent of the means of exposure; (v) excessive accumulation of titanium in the environment cannot be ignored; (vi) titanium/titania-containing products should be clearly marked with health warning labels, especially for pregnant women and young children; (vi) a key knowledge gap is the lack of comprehensive data about the environmental content and the influence of titania/titanium on biodiversity and the ecological functioning of terrestrial and aquatic ecosystems.

Multigenerational exposure to TiO2 nanoparticles in soil stimulates stress resistance and longevity of survived C. elegans via activating insulin/IGF-like signaling

With increasing release of nanoparticles (NPs) into the environment, soil organisms likely suffer from high dose and long duration of NPs contamination, while the effect of NPs across multiple generations in soil is rarely studied. Herein, we investigated how multigenerational exposure to different crystal forms (anatase, rutile, and their mixture) of TiO₂ NPs (nTiO₂) affected the survival, behavior, physiological and biochemical traits, and lifespan of nematodes (C. elegans) in a paddy soil. The soil property changed very slightly after being spiked with nTiO₂, and the toxicities of three nTiO₂ forms were largely comparable. The nTiO₂ exposure adversely influenced the survival and locomotion of nematodes, and increased intracellular reactive oxygen species (ROS) generation. Interestingly, the toxic effect gradually attenuated and the lifespan of survived nematodes increased from the P0 to F3 generation, which was ascribed to the survivor selection and stimulatory effect. The lethal effect and the increased oxidative stress may continuously screen out offspring possessing stronger anti-stress capabilities. Moreover, key genes (daf-2, age-1, and skn-1) in the insulin/IGF-like signaling (IIS) pathway actively responded to the nTiO₂ exposure, which further optimized the selective expression of downstream genes, increased the antioxidant enzyme activities and antioxidant contents, and thereby increased the stress resistance and longevity of survived nematodes across successive generations. Our findings highlight the crucial role of bio-responses in the progressively decreased toxicity of nTiO₂, and add new knowledge on the long-term impact of soil nTiO₂ contamination.

Size-dependent effects of polystyrene plastic particles on the nematode Caenorhabditis elegans as related to soil physicochemical properties

Plastic polymers are widely used in various applications and are thus prevalent in the environment. Over time, these polymers are slowly degraded into nano- and micro-scale particles. In this study, the free-living nematode, Caenorhabditis elegans, was exposed to polystyrene particles of two different sizes (42 and 530 nm) in both liquid and soil media. The number of offspring significantly (p < 0.05) decreased at polystyrene concentrations of 100 mg/L and 10 mg/kg in liquid and soil media, respectively. In soil media, but not liquid media, C. elegans was more sensitive to the larger particles (530 nm) than the smaller particles (42 nm), and the median effective concentration (EC₅₀) values of the 42 and 530 nm-sized particles were found to be > 100 and 14.23 (8.91-22.72) mg/kg, respectively. We performed the same toxicity bioassay on five different field-soil samples with different physicochemical properties and found that the size-dependent effects were intensified in clay-rich soil samples. A principal component analysis showed that the bulk density, cation exchange capacity, clay content, and sand content were the dominant factors influencing the toxicity of the 530 nm-sized polystyrene particles. Therefore, we conclude that the soil composition has a significant effect on the toxicity induced by these 530 nm-sized polystyrene particles.

Quantum dots functionalized with gH625 attenuate QDs oxidative stress and lethality in Caenorhabditis elegans: a model system

Nanomaterials have revolutionized many scientific fields and are widely applied to address environmental problems and to develop novel health care strategies. However, their mechanism of action is still poorly understood. Several nanomaterials for medical applications are based on quantum dots (QDs). Despite their amazing physico-chemical properties, quantum dots display significant adverse effects. In the present study, the effects of QDs on the motor nervous system of nematodes Caenorhabditis elegans have been investigated as a non-mammalian alternative model. We also explored the possibility of modifying the toxicity of QDs by coating with a cell-penetrating peptide gH625 and thus we analysed the effects determined by QDs-gH625 complexes on the nematodes. With this work, we have demonstrated, by in vivo experiments, that the peptide gH625 is able to reduce the side effects of metallic nanoparticle making them more suitable for medical applications.

Effect of soil microbial feeding on gut microbiome and cadmium toxicity in Caenorhabditis elegans

Microbial community of an organism plays an important role on its fitness, including stress responses. In this study, we investigated the effect of the culturable subset of soil microbial community (SMB) on the stress response of the soil nematode Caenorhabditis elegans, upon exposure to one of the major soil contaminants, cadmium (Cd). Life history traits and the stress responses to Cd exposure were compared between SMB- and Escherichia coli strain OP50-fed worms. SMB-fed worms showed higher reproduction rates and longer lifespans. Also, the SMB-fed worms showed more tolerant response to Cd exposure. Gene expression profiling suggested that the chemical stress and immune response of worms were boosted upon SMB feeding. Finally, we investigated C. elegans gut microbial communities in the presence and absence of Cd in OP50- and SMB-fed C. elegans. In the OP50-fed worms, changes in microbial community by Cd exposure was severe, whereas in the SMB-fed worms, it was comparatively weak. Our results suggest that the SMB affects the response of C. elegans to Cd exposure and highlight the importance of the gut microbiome in host stress response.

A Multiparametric Approach to Cerium Oxide Nanoparticle Toxicity Assessment in Non-Biting Midges

Cerium oxide nanoparticles (CeO₂ NPs) are included in the Organisation for Economic Co-operation and Development (OECD) priority list of engineered nanomaterials for assessment of their environmental impact. The present study was carried out to assess the CeO₂ NP toxicity to the freshwater midge Chironomus riparius larvae at concentrations of 2.5, 25, 250, and 2500 mg of CeO₂ NP/kg of sediment. Experiments were designed to assess the prolonged exposure of midges to CeO₂ NPs while adhering to OECD test guideline 218. The following parameters were investigated: CeO₂ NP uptake by larvae, oxidative stress parameters, in vivo genotoxic effects, and life trait parameters. Inductively coupled plasma-mass spectrometry analysis showed a significant positive correlation between the concentration of CeO₂ NPs in the sediment and its uptake by the larvae. No significant mortality was observed in C. riparius, and oxidative stress was not detected. The only significantly induced sublethal effect was genotoxicity, which began to manifest at a lowest-observed-effect concentration of 25 mg kg^-1 of sediment and progressively increased at higher concentrations. Our results indicate that exposure to CeO₂ NP-contaminated freshwater sediments does not pose a risk to chironomids at environmentally realistic concentrations. However, the significant accumulation of CeO₂ NPs by chironomid larvae may pose a risk through trophic transfer to organisms further up the food chain. Environ Toxicol Chem 2019;39:131-140. © 2019 SETAC.

Behavior of cerium dioxide nanoparticles in chernozem soils at different exposure scenarios

Nowadays, widespread application of engineered nanoparticles (ENPs) inevitably leads to their release into the environment. Soils are regarded as the ultimate sink for ENPs. The study on mobility of ENPs in soils is important in the assessment of potential risks related to their toxicity. The behavior of ENPs is dependent not only on parameters of soil but also on exposure scenarios, namely, the amount of ENPs trapped in soil. In the present work, the mobility of cerium dioxide nanoparticles (nCeO₂) in soils at different exposure scenarios has been studied. The relationship between mobility of nCeO₂ and their concentration in soil in the range from 1 to 1000 μg g^-1 is evaluated. It is shown that the mobility of nCeO₂ decreases with decreasing their concentration in soil and attains the minimum value at the concentration of nCeO₂ below 10 μg g^-1. In relative terms, only about 0.1-0.2% of nCeO₂ at their concentration in soil 10-1000 μg g^-1 are mobile and can migrate in soil profile under saturated conditions. The major portion of nCeO₂ (about 99.8%) remains immobile in soil. Evidently, the vertical transport of nCeO₂ in soil profile should depend on volume of released suspensions. In the case of small or moderate wet deposition, nanoparticles will accumulate in upper soil horizons, where biological activity is highest, and affect the soil inhabitants (plant roots, earthworms, insects, microorganisms, etc.).

Caenorhabditis elegans as a tool for environmental risk assessment: emerging and promising applications for a "nobelized worm"

Caenorhabditis elegans has been an invaluable model organism in research fields such as developmental biology and neurobiology. Neurotoxicity is one of the subfields greatly profiting from the C. elegans model within biomedical context, while the corresponding potential of the organism applied to environmental studies is relevant but has been largely underexplored. Within the biomedical scope, the implication of metals and organic chemicals with pesticide activity (hereinafter designated as pesticides) in the etiology of several neurodegenerative diseases has been extensively investigated using this nematode as a primary model organism. Additionally, as a well-known experimental model bearing high sensitivity to different contaminants and representing important functional levels in soil and aquatic ecosystems, C. elegans has high potential to be extensively integrated within Environmental Risk Assessment (ERA) routines. In spite of the recognition of some regulatory agencies, this actual step has yet to be made. The purpose of this review is to discuss the major advantages supporting the inclusion of C. elegans in lower tiers of ERA. Special emphasis was given to its sensitivity to metals and pesticides, which is similar to that of other model organisms commonly used in ERA (e.g. Daphnia magna and Eisenia sp.), and to the large array of endpoints that can be tested with the species, both concerning the aquatic and the soil compartments. The inclusion of C. elegans testing may hence represent a relevant advance in ERA, providing ecologically relevant insights toward improvement of the regulatory capacity for establishing appropriate environmental protection benchmarks.

Caenorhabditis elegans as a complete model organism for biosafety assessments of nanoparticles

The number of biosafety evaluation studies of nanoparticles (NPs) using different biological models is increasing with the rapid development of nanotechnology. Thus far, nematode Caenorhabditis elegans (C. elegans), as a complete model organism, has become an important in vivo alternative assay system to assess the risk of NPs, especially at the environmental level. According to results of qualitative and quantitative analyses, it can be concluded that studies of nanoscientific research using C. elegans is persistently growing. However, the comprehensive conclusion and analysis of toxic effects of NPs in C. elegans are limited and chaotic. This review focused on the effects, especially sublethal ones, induced by NPs in C. elegans, including the development, intestinal function, immune response, neuronal function, and reproduction, as well as the underlying mechanisms of NPs causing these effects, including oxidative stress and alterations of several signaling pathways. Furthermore, we presented some factors that influence the toxic effects of NPs in C. elegans. The advantages and limitations of using nematodes in the nanotoxicology study were also discussed. Finally, we predicted that the application of C. elegans to assess long-term impacts of metal oxide NPs in the ecosystem would become a vital part of the nanoscientific research field, which provided an insight for further study.

Effects of ionic strength on physicochemical properties and toxicity of silver nanoparticles

In the environment, silver nanoparticles (AgNPs) undergo a number of potential transformations, such as aggregation, dissolution, and redox reactions. However, the transformation in ionic strength condition, as well as their related toxicity was not quite clear, especially in the in vivo system. In the present study, we comprehensively evaluated three different characteristics (ddH₂O, EPA water and K⁺ medium (KM)) mediated changes in the physical morphology of AgNPs and the alteration of the toxicity to Caenorhabditis elegans (C. elegans). Our results showed besides the changes of AgNPs behavior such as the transformation of morphological, with the transmission electron microscopy we found for the first time that smaller nanoparticles (<5 nm) appeared around the pristine AgNPs after incubation in EPA or KM for 5 days. Together with these changes, the toxicity of AgNPs to C. elegans changed significantly, showing that a higher ionic strength medium resulted in greater toxicity to C. elegans, as measured by germ cell apoptosis, brood size and lifespan. More importantly, our results indicated that the higher toxicity of AgNPs to C. elegans reproduction was probably related to the appearance of the smaller-size AgNPs in higher ionic strength media. These findings highlight that toxicity assessments for the release of nanomaterial to the environment need to be improved to assess environmental safety more accurately.

Toxicity and mechanisms of action of titanium dioxide nanoparticles in living organisms

Titanium dioxide nanoparticles (TiO₂ NPs) are one of the most widely used nanomaterials in the consumer products, agriculture, and energy sectors. Their large demand and widespread applications will inevitably cause damage to organisms and ecosystems. A better understanding of TiO₂ NP toxicity in living organisms may promote risk assessment and safe use practices of these nanomaterials. This review summarizes the toxic effects of TiO₂ NPs on multiple taxa of microorganisms, algae, plants, invertebrates, and vertebrates. The mechanism of TiO₂ NP toxicity to organisms can be outlined in three aspects: The Reactive Oxygen Species (ROS) produced by TiO₂ NPs following the induction of electron-hole pairs; cell wall damage and lipid peroxidation of the cell membrane caused by NP-cell attachment by electrostatic force owing to the large surface area of TiO₂ NPs; and TiO₂ NP attachment to intracellular organelles and biological macromolecules following damage to the cell membranes.

Sublethal Effects of Ionic and Nanogold on the Nematode Caenorhabditis elegans

The nematode Caenorhabditis elegans is used as an ecotoxicological model species in both aqueous medium and solid substrates. It is easy and of low cost to maintain in the laboratory and it produces hundreds of offspring within a short period of time. It also has a small body size (1 mm), making it possible for in vivo assays to be conducted in 12-well plates. Engineered nanomaterials (ENMs) are a class of emerging pollutants. Nanogold (nAu) is used in many consumer products and in vivo drug delivery. These materials can be released into the aquatic environment during production or discarding of consumer products. As nAu is insoluble in water, the sediment would become the final depository for the materials. It has become increasingly important to use sediment dwelling organisms to screen for possible toxicity of these ENMs. In this study C. elegans was exposed to a range of concentrations of nAu and ionic gold in M9-media, acting as a substitute for pore water. After 96-hour growth, fertility and reproduction were determined. Internal structure damage and internalisation of particles in C. elegans were determined by using SEM and CytoViva® Darkfield Imaging. From these images the nanomaterials are distributed around the oocytes in the reproductive organs, as well as the pharynx. Results obtained indicate that nAu affects reproduction more than growth due to internal gonad damage, albeit at very high exposure concentrations, indicating no toxicity at environmentally relevant concentrations. Ionic Au is more toxic than nAu and effects fertility and reproduction due to ion release. These results give more information regarding the toxicity and in vivo uptake of nAu and form part of an environmental risk assessment of ENMs.

Toxicological Effect of Metal Oxide Nanoparticles on Soil and Aquatic Habitats

Metal oxide nanoparticles (MO-NPs) with multifunctional properties are used extensively in various industries and released into the environment as industrial effluents and waste nano-products. These non-degradable, toxic MO-NPs are accumulating in the environment, debilitating the ecosystem and their biological communities. In this review article, a real-time scenario of MO-NP toxicity towards the soil and aquatic ecosystem and their mode of toxicity have been addressed in detail. The up-to-date information presented here suggests serious consideration of the consequences before random utilization of MO-NPs.

Toxicity of atrazine- and glyphosate-based formulations on Caenorhabditis elegans

Atrazine and Glyphosate are herbicides massively used in agriculture for crop protection. Upon application, they are available to the biota in different ecosystems. The aim of this research was to evaluate the toxicity of Glyphosate and Atrazine based formulations (GBF and ABF, respectively). Caenorhabditis elegans was exposed to different concentrations of each single formulation, and to the mixture. Lethality, locomotion, growth, and fertility were measured as endpoints. Effects on gene expression were monitored utilizing green fluorescence protein transgenic strains. ABF caused lethality of 12%, 15%, and 18% for 6, 60, and 600 μM, respectively, displaying a dose dependence trend. GBF produced lethality of 20%, 50%, and 100% at 0.01, 10, and 100 μM, respectively. Locomotion inhibition ranged from 21% to 89% at the lowest and maximum tested concentrations for Atrazine; whereas for Glyphosate, exposure to 10 μM inhibited 87%. Brood size was decreased by 67% and 93% after treatment to 0.06 and 6 μM Atrazine, respectively; and by 23% and 93% after exposure to 0.01 and 10 μM Glyphosate, respectively. There were no significant differences in growth. Changes in gene expression occurred in all genes, highlighting the expression of sod-1, sod-4, and gpx-4 that increased more than two-fold after exposure to 600 μM ABF and 10 μM GBF. The effects observed for the mixture of these formulations were additive for lethality, locomotion and fertility. In short, GBF, ABF, and their mixture induced several toxic responses related to oxidative stress on C. elegans.

Bioaccumulation of CeO2 Nanoparticles by Earthworms in Biochar-Amended Soil: A Synchrotron Microspectroscopy Study

The interactions of nanoparticles (NPs) with biochar and soil components may substantially influence NP availability and toxicity to biota. In the present study, earthworms ( Eisenia fetida) were exposed for 28 days to a residential or agricultural soil amended with 0-2000 mg of CeO₂ NP/kg and with biochar (produced by the pyrolysis of pecan shells at 350 and 600 °C) at various application rates [0-5% (w/w)]. After 28 days, earthworms were depurated and analyzed for Ce content, moisture content, and lipid peroxidation. The results showed minimal toxicity to the worms; however, biochar (350 or 600 °C) was the dominant factor, accounting for 94 and 84% of the variance for the moisture content and lipid peroxidation, respectively, in the exposed earthworms. For both soils with 1000 mg of CeO₂/kg at 600 °C, biochar significantly decreased the accumulation of Ce in the worm tissues. Amendment with 350 °C biochar had mixed responses on Ce uptake. Analysis by micro X-ray fluorescence (μ-XRF) and micro X-ray absorption near edge structure (μ-XANES) was used to evaluate Ce localization, speciation, and persistence in CeO₂- and biochar-exposed earthworms after depuration for 12, 48, and 72 h. Earthworms from the 500 mg of CeO₂/kg and 0% biochar treatments eliminated most Ce after a 48 h depuration period. However, in the same treatment and with 5% BC-600 (biochar pyrolysis temperature of 600 °C), ingested biochar fragments (∼50 μm) with Ce adsorbed to the surfaces were retained in the gut after 72 h. Additionally, Ce remained in earthworms from the 2000 mg of CeO₂/kg and 5% biochar treatments after depuration for 48 h. Analysis by μ-XANES showed that, within the earthworm tissues, Ce remained predominantly as Ce⁴⁺O₂, with only few regions (2-3 μm²) where it was found in the reduced form (Ce³⁺). The present findings highlight that soil and biochar properties have a significant influence in the internalization of CeO₂ NPs in earthworms; such interactions need to be considered when estimating NP fate and effects in the environment.

Toxic Effects of Bisphenol A, Propyl Paraben, and Triclosan on Caenorhabditis elegans

Bisphenol A (BPA) is a ubiquitous plasticizer which is absorbed by ingestion and dermal contact; propyl paraben (PPB) inhibits the microbiome and extends the shelf life of many personal care products, whereas triclosan (TCS) is commonly found in antiseptics, disinfectants, or additives. In this work, Caenorhabditis elegans was used as a biological model to assess the toxic effects of BPA, PPB, and TCS. The wild type strain, Bristol N2, was used in bioassays with the endpoints of lethality, growth, and reproduction; green fluorescent protein (GFP) transgenic strains with the hsp-3, hsp-4, hsp-16.2, hsp-70, sod-1, sod-4, cyp-35A4, cyp-29A2, and skn-1 genes were evaluated for their mRNA expression through fluorescence measurement; and quick Oil Red O (q ORO) was utilized to stain lipid deposits. Lethality was concentration-dependent, while TCS and PPB showed more toxicity than BPA. BPA augmented worm length, while PPB reduced it. All toxicants moderately increased the width and the width–length ratio. BPA and PPB promoted reproduction, in contrast to TCS, which diminished it. All toxicants affected the mRNA expression of genes related to cellular stress, control of reactive oxygen species, and nuclear receptor activation. Lipid accumulation occurred in exposed worms. In conclusion, BPA, PPB, and TCS alter the physiology of growth, lipid accumulation, and reproduction in C. elegans, most likely through oxidative stress mechanisms.

Uptake of TiO2 Nanoparticles into C. elegans Neurons Negatively Affects Axonal Growth and Worm Locomotion Behavior

We employ model organism Caenorhabditis elegans to effectively study the toxicology of anatase and rutile phase titanium dioxide (TiO₂) nanoparticles (NPs). The experimental results show that nematode C. elegans can take up fluorescein isothiocyanate-labeled TiO₂ NPs and that both anatase and rutile TiO₂ NPs can be detected in the cytoplasm of cultured primary neurons imaged by transmission electron microscopy. After TiO₂ NP exposure, these neurons also grow shorter axons, which may be related to the detected impeded worm locomotion behavior. Furthermore, anatase TiO₂ NPs did not affect the worm's body length; however, we determined that a concentration of 500 μg/mL of anatase TiO₂ NPs reduced the worm population by 50% within 72 h. Notably, rutile TiO₂ NPs negatively affect both the body size and worm population. Worms unable to enter the L4 larval stage explain a severe reduction in the worm population at TiO₂ NPs LC₅₀/3d. To obtain a better understanding of the cellular mechanisms involved in TiO₂ NP intoxication, DNA microarray assays were employed to determine changes in gene expression in the presence or absence of TiO₂ NP exposure. Our data reveal that three genes (with significant changes in expression levels) were related to metal binding or metal detoxification (mtl-2, C45B2.2, and nhr-247), six genes were involved in fertility and reproduction (mtl-2, F26F2.3, ZK970.7, clec-70, K08C9.7, and C38C3.7), four genes were involved in worm growth and body morphogenesis (mtl-2, F26F2.3, C38C3.7, and nhr-247), and five genes were involved in neuronal function (C41G6.13, C45B2.2, srr-6, K08C9.7, and C38C3.7).

Toxicity profile of organic extracts from Magdalena River sediments

The Magdalena River, the main river of Colombia, receives contaminated effluents from different anthropogenic activities along its path. However, the Magdalena River is used as drinking water source for approximately 30 million inhabitants, as well as a major source of fish for human consumption. Only a few studies have been conducted to evaluate the environmental and toxicological quality of the Magdalena River. To evaluate sediment toxicity, wild-type and GFP transgenic Caenorhabditis elegans were exposed to methanolic extracts, and effects on lethality, locomotion, growth, and gene expression were determined based on fluorescence spectroscopy. These biological and biochemical parameters were correlated with measured pollutant concentrations (PAHs and trace elements), identifying patterns of toxicity along the course of the river. Effects on lethality, growth, and locomotion were observed in areas influenced by industrial, gold mining, and petrochemical activities. Changes in gene expression were evident for cyp-34A9, especially in the sampling site located near an oil refinery, and at the seaport, in Barranquilla City. Body bend movements were moderately correlated with Cr and As concentrations. The expression of mtl-1, mtl-2, hsp-6, and hsp-70 were significantly associated with Pb/U, Pb, Sr, and As/Sr/Pb/U, respectively. Interestingly, toxicity of methanolic as well as aqueous extracts were more prone to be dependent on Cd, Zn, and Th. In general, ecological risk assessment showed sediments display low environmental impact in terms of evaluated metals and PAHs. Different types of waste disposal on the Magdalena River, as a result of mining, domestic, agricultural, and industrial activities, incorporate toxic pollutants in sediments, which are capable of generating a toxic response in C. elegans.

The role of charge in the toxicity of polymer-coated cerium oxide nanomaterials to Caenorhabditis elegans

This study examined the impact of surface functionalization and charge on ceria nanomaterial toxicity to Caenorhabditis elegans. The examined endpoints included mortality, reproduction, protein expression, and protein oxidation profiles. Caenorhabditis elegans were exposed to identical 2-5nm ceria nanomaterial cores which were coated with cationic (diethylaminoethyl dextran; DEAE), anionic (carboxymethyl dextran; CM), and non-ionic (dextran; DEX) polymers. Mortality and reproductive toxicity of DEAE-CeO₂ was approximately two orders of magnitude higher than for CM-CeO₂ or DEX-CeO₂. Two-dimensional gel electrophoresis with orbitrap mass spectrometry identification revealed changes in the expression profiles of several mitochondrial-related proteins and proteins that are expressed in the C. elegans intestine. However, each type of CeO₂ material exhibited a distinct protein expression profile. Increases in protein carbonyls and protein-bound 3-nitrotyrosine were also observed for some proteins, indicating oxidative and nitrosative damage. Taken together the results indicate that the magnitude of toxicity and toxicity pathways vary greatly due to surface functionalization of CeO₂ nanomaterials.

Interaction of Engineered Nanoparticles with the Agri-environment

Nanoparticles with their unique surface properties can modulate the physiological, biochemical, and physicochemical pathways, such as photosynthesis, respiration, nitrogen metabolism, and solute transport. In this context, researchers have developed a wide range of engineered nanomaterials (ENMs) for the improvement of growth and productivity by modulating the metabolic pathways in plants. This class of tailor-made materials can potentially lead to the development of a new group of agrochemical nanofertilizers. However, there are reports that engineered nanomaterials could impart phytotoxicity to edible and medicinal plants. On the contrary, there is a series of ENMs that might be detrimental when applied directly and/or indirectly to the plants. These particles can sometimes readily aggregate and dissolute in the immediate vicinity; the free ions released from the nanomatrix can cause serious tissue injury and membrane dysfunction to the plant cell through oxidative stress. On that note, thorough studies on uptake, translocation, internalization, and nutritional quality assessment must be carried out to understand ENM-plant interactions. This review critically discusses the possible beneficial or adverse aftereffect of nanofertilizers in the immediate environment to interrelate the impacts of ENMs on the crop health and food security management.

Materials and toxicological approaches to study metal and metal-oxide nanoparticles in the model organism Caenorhabditis elegans

Understanding the in vivo fate and transport of nanoparticles (NPs) is challenging, but critical. We review recent studies of metal and metal oxide NPs using the model organism Caenorhabditis elegans, summarizing major findings to date. In a joint transdisciplinary effort, we highlight underutilized opportunities offered by powerful techniques lying at the intersection of mechanistic toxicology and materials science,. To this end, we firstly summarize the influence of exposure conditions (media, duration, C. elegans lifestage) and NP physicochemical properties (size, coating, composition) on the response of C. elegans to NP treatment. Next, we focus on the techniques employed to study NP entrance route, uptake, biodistribution and fate, emphasizing the potential of extending the toolkit available with novel and powerful techniques. Next, we review findings on several NP-induced biological responses, namely transport routes and altered molecular pathways, and illustrate the molecular biology and genetic strategies applied, critically reviewing their strengths and weaknesses. Finally, we advocate the incorporation of a set of minimal materials and toxicological science experiments that will permit meta-analysis and synthesis of multiple studies in the future. We believe this review will facilitate coordinated integration of both well-established and underutilized approaches in mechanistic toxicology and materials science by the nanomaterials research community.

Toxicogenomics of iron oxide nanoparticles in the nematode C. elegans

We present a mechanistic study of the effect of iron oxide nanoparticles (SPIONs) in Caenorhabditis elegans combining a genome-wide analysis with the investigation of specific molecular markers frequently linked to nanotoxicity. The effects of two different coatings were explored: citrate, an anionic stabilizer, and bovine serum albumin, as a pre-formed protein corona. The transcriptomic study identified differentially expressed genes following an exposure to SPIONs. The expression of genes involved in oxidative stress, metal detoxification response, endocytosis, intestinal integrity and iron homeostasis was quantitatively evaluated. The role of oxidative stress was confirmed by gene expression analysis and by synchrotron Fourier Transform infrared microscopy based on the higher tissue oxidation of NP-treated animals. The observed transcriptional modulation of key signaling pathways such as MAPK and Wnt suggests that SPIONs might be endocytosed by clathrin-mediated processes, a putative mechanism of nanotoxicity which deserves further mechanistic investigations.

CeO2 nanoparticle fate in environmental conditions and toxicity on a freshwater predator species: a microcosm study

We studied the fate and toxicity of two types of CeO₂ NPs (bare or citrate-coated) in environmentally relevant conditions, using large indoor microcosms. Long-term exposure was carried out on a three-leveled freshwater trophic chain, comprising microbial communities as primary producers, chironomid larvae as primary consumers, and amphibian larvae as secondary consumers. Whereas coated NPs preferentially sedimented, bare NPs were mainly found in the water column. However, mass balance indicated low recovery (51.5%) for bare NPs, indicating possible NP loss, against 98.8% of recovery for coated NPs. NPs were rather chemically stable, with less than 4% of dissolution. Chironomid larvae ingested large amounts of NPs and were vectors of contamination for amphibian larvae. Although bioaccumulation in amphibian larvae was important (9.47 and 9.74 mg/kg for bare and coated NPs, respectively), no biomagnification occurred through the trophic chain. Finally, significant genotoxicity was observed in amphibian larvae, bare CeO₂ NPs being more toxic than citrate-coated NPs. ᅟ.

Model-based optimization of parameters for degradation reaction of an organophosphorus pesticide, paraoxon, using CeO2 nanoparticles in water media

Degradation and body surface decontamination is vital to prevent the skin penetration of paraoxon (POX), an organophosphorus pesticide, and victims poisoning. CeO₂ demonstrated a good efficacy for the degradation of POX. The aim of the study was to develop a model which includes the impact of weight of CeO₂, POX and diluent volumes on the degradation kinetics. The modelling was realized with rapid and simple experiments carried out in tubes, in aqueous diluent which contained ions in order to be in accordance with in vitro skin decontamination conditions. CeO₂ had degraded from 5% (in case of 7.5mmol of POX per gram of CeO₂) to 100% (0.002mmol of POX per gram of CeO₂) of POX. Different kinetic models were tested. Using the particle aggregation kinetic model, the simulated and experimental data were in a good accordance. It highlighted the importance of particles aggregation due to salts and consistency of the mix on the degradation efficiency of CeO₂. The model worked also really well to predict the degradation efficiency of CeO₂ powders during in vitro skin experiments. However, it did not correctly forecast with an aqueous decontaminant, containing CeO₂.

Effects of CeO2 Nanoparticles on Terrestrial Isopod Porcellio scaber: Comparison of CeO2 Biological Potential with Other Nanoparticles

Nano-sized cerium dioxide (CeO₂) particles are emerging as an environmental issue due to their extensive use in automobile industries as fuel additives. Limited information is available on the potential toxicity of CeO₂ nanoparticles (NPs) on terrestrial invertebrates through dietary exposure. In the present study, the toxic effects of CeO₂ NPs on the model soil organism Porcellio scaber were evaluated. Nanotoxicity was assessed by monitoring the lipid peroxidation (LP) level and feeding rate after 14-days exposure to food amended with nano CeO₂. The exposure concentration of 1000 μg of CeO₂ NPs g^-1 dry weight food for 14 days significantly increased both the feeding rate and LP. Thus, this exposure dose is considered the lowest observed effect dose. At higher exposure doses of 2000 and 5000 μg of CeO₂ NPs g^-1 dry weight food, NPs significantly decreased the feeding rate and increased the LP level. Comparative studies showed that CeO₂ NPs are more biologically potent than TiO₂ NPs, ZnO NPs, CuO NPs, CoFe₂O₄ NPs, and Ag NPs based on feeding rate using the same model organism and experimental setup. Based on comparative metal oxide NPs toxicities, the present results contribute to the knowledge related to the ecotoxicological effects of CeO₂ NPs in terrestrial invertebrates exposed through feeding.

Ecotoxicity of titanium silicon oxide (TiSiO4) nanomaterial for terrestrial plants and soil invertebrate species

The huge evolution of nanotechnology and the commercialization of nanomaterials (NMs) positively contributed for innovation in several industrial sectors. Facing this rapid development and the emergence of NMs in the market, the release of this nanometric sized materials in the environment and the possible impact on different ecosystem components attracted the attention of researchers in the last few years. In our study we aimed to assess the impact of titanium silicon oxide nanomaterial (nano-TiSiO4) on soil biota to estimate a risk limit for this material. In the present research a battery of standardized ecotoxicological assays aimed at evaluating a wide range of endpoints (avoidance and reproduction of earthworms and collembolans, emergence/growth of four selected terrestrial plants) were carried out, using OECD artificial soil as test substrate spiked with aqueous suspension of different concentrations of nano-TiSiO4. The results showed a maximum avoidance percentage of 40% for earthworms (Esenia andrei) at the highest concentration tested (1000mgkg(-1) soildw of nano-TiSiO4). No significant effect on the reproductive function of both invertebrate species was recorded. Nevertheless, significant phytotoxic data was registered at least for the growth of dicotyledonous plant species (Lactuca sativa and Lycopersicon lycopersicum) with EC20 values ranging between 236 and 414 mg kg(-1) soildw of nano-TiSiO4 for L. sativa dry mass and fresh mass, respectively. Further, the characterization of nano-TiSiO4 in suspensions used to spike the soil, performed by Dynamic Light Scattering, showed the formation of aggregates with important average size diameter, thus demonstrating that the toxic effects observed were likely not size dependent. A deterministic PNEC (predicted no effect concentration) for this NM of 10.02mg kg(-1) soildw of nano-TiSiO4, is suggested, while no more ecotoxicological information exists.

Distinct transcriptomic responses of Caenorhabditis elegans to pristine and sulfidized silver nanoparticles

Manufactured nanoparticles (MNP) rapidly undergo aging processes once released from products. Silver sulfide (Ag2S) is the major transformation product formed during the wastewater treatment process for Ag-MNP. We examined toxicogenomic responses of pristine Ag-MNP, sulfidized Ag-MNP (sAg-MNP), and AgNO3 to a model soil organism, Caenorhabditis elegans. Transcriptomic profiling of nematodes which were exposed at the EC30 for reproduction for AgNO3, Ag-MNP, and sAg-MNP resulted in 571 differentially expressed genes. We independently verified expression of 4 genes (numr-1, rol-8, col-158, and grl-20) using qRT-PCR. Only 11% of differentially expressed genes were common among the three treatments. Gene ontology enrichment analysis also revealed that Ag-MNP and sAg-MNP had distinct toxicity mechanisms and did not share any of the biological processes. The processes most affected by Ag-MNP relate to metabolism, while those processes most affected by sAg-MNP relate to molting and the cuticle, and the most impacted processes for AgNO3 exposed nematodes was stress related. Additionally, as observed from qRT-PCR and mutant experiments, the responses to sAg-MNP were distinct from AgNO3 while some of the effects of pristine MNP were similar to AgNO3, suggesting that effects from Ag-MNP is partially due to dissolved silver ions.