Effects of Multiple Stressors, Pristine or Sulfidized Silver Nanomaterials, and a Pathogen on a Model Soil Nematode Caenorhabditis elegans.

Previous research using the model soil nematode Caenorhabditis elegans has revealed that silver nanoparticles (AgNP) and their transformed counterpart, sulfidized AgNP (sAgNP), reduce their reproduction and survival. To expand our understanding of the environmental consequences of released NP, we examined the synergistic/antagonistic effects of AgNP and sAgNP along with AgNO3 (ionic control) on C. elegans infected with the pathogen Klebsiella pneumoniae. Individual exposures to each stressor significantly decreased nematode reproduction compared to controls. Combined exposures to equitoxic EC30 concentrations of two stressors, Ag in nanoparticulate (AgNP or sAgNP) or ionic form and the pathogen K. pneumoniae, showed a decline in the reproduction that was not significantly different compared to individual exposures of each of the stressors. The lack of enhanced toxicity after simultaneous combined exposure is partially due to Ag decreasing K. pneumoniae pathogenicity by inhibiting biofilm production outside the nematode and significantly reducing viable pathogens inside the host. Taken together, our results indicate that by hindering the ability of K. pneumoniae to colonize the nematode's intestine, Ag reduces K. pneumoniae pathogenicity regardless of Ag form. These results differ from our previous research where simultaneous exposure to zinc oxide (ZnO) NP and K. pneumoniae led to a reproduction level that was not significantly different from the controls.

Metal-Organic Framework-Enabled Sustainable Agrotechnologies: An Overview of Fundamentals and Agricultural Applications.

With aggravated abiotic and biotic stresses from increasing climate change, metal-organic frameworks (MOFs) have emerged as versatile toolboxes for developing environmentally friendly agrotechnologies aligned with agricultural practices and safety. Herein, we have explored MOF-based agrotechnologies, focusing on their intrinsic properties, such as structural and catalytic characteristics. Briefly, MOFs possess a sponge-like porous structure that can be easily stimulated by the external environment, facilitating the controlled release of agrochemicals, thus enabling precise delivery of agrochemicals. Additionally, MOFs offer the ability to remove or degrade certain pollutants by capturing them within their pores, facilitating the development of MOF-based remediation technologies for agricultural environments. Furthermore, the metal-organic hybrid nature of MOFs grants them abundant catalytic activities, encompassing photocatalysis, enzyme-mimicking catalysis, and electrocatalysis, allowing for the integration of MOFs into degradation and sensing agrotechnologies. Finally, the future challenges that MOFs face in agrotechnologies were proposed to promote the development of sustainable agriculture practices.

Pristine and Sulfidized Zinc Oxide Nanoparticles Promote the Release and Decomposition of Organic Carbon in the Legume Rhizosphere.

The effects and mechanisms of zinc oxide nanoparticles (ZnO NPs) and their aging products, sulfidized (s-) ZnO NPs, on the carbon cycling in the legume rhizosphere are still unclear. We observed that, after 30 days of cultivation, in the rhizosphere soil of Medicago truncatula, under ZnO NP and s-ZnO NP treatments, the dissolved organic carbon (DOC) concentrations were significantly increased by 1.8- to 2.4-fold compared to Zn2+ treatments, although the soil organic matter (SOM) contents did not change significantly. Compared to Zn2+ additions, the additions of NPs significantly induced the production of root metabolites such as carboxylic acids and amino acids and also stimulated the growth of microbes involved in the degradations of plant-derived and recalcitrant SOM, such as bacteria genera RB41 and Bryobacter, and fungi genus Conocybe. The bacterial co-occurrence networks indicated that microbes associated with SOM formation and decomposition were significantly increased under NP treatments. The adsorption of NPs by roots, the generation of root metabolites (e.g., carboxylic acid and amino acid), and enrichment of key taxa (e.g., RB41 and Gaiella) were the major mechanisms by which ZnO NPs and s-ZnO NPs drove DOC release and SOM decomposition in the rhizosphere. These results provide new perspectives on the effect of ZnO NPs on agroecosystem functions in soil-plant systems.

Global DNA Adenine Methylation in Caenorhabditis elegans after Multigenerational Exposure to Silver Nanoparticles and Silver Nitrate.

Multigenerational and transgenerational reproductive toxicity in a model nematode Caenorhabditis elegans has been shown previously after exposure to silver nanoparticles (Ag-NPs) and silver ions (AgNO3). However, there is a limited understanding on the transfer mechanism of the increased reproductive sensitivity to subsequent generations. This study examines changes in DNA methylation at epigenetic mark N6-methyl-2'-deoxyadenosine (6mdA) after multigenerational exposure of C. elegans to pristine and transformed-via-sulfidation Ag-NPs and AgNO3. Levels of 6mdA were measured as 6mdA/dA ratios prior to C. elegans exposure (F0) after two generations of exposure (F2) and two generations of rescue (F4) using high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS). Although both AgNO3 and Ag-NPs induced multigenerational reproductive toxicity, only AgNO3 exposure caused a significant increase in global 6mdA levels after exposures (F2). However, after two generations of rescue (F4), the 6mdA levels in AgNO3 treatment returned to F0 levels, suggesting other epigenetic modifications may be also involved. No significant changes in global DNA methylation levels were observed after exposure to pristine and sulfidized sAg-NPs. This study demonstrates the involvement of an epigenetic mark in AgNO3 reproductive toxicity and suggests that AgNO3 and Ag-NPs may have different toxicity mechanisms.

Silver contamination and its toxicity and risk management in terrestrial and aquatic ecosystems.

Silver (Ag), a naturally occurring, rare and precious metal, is found in major minerals such as cerargyrite (AgCl), pyrargyrite (Ag3SbS3), proustite (Ag3AsS3), and stephanite (Ag5SbS4). From these minerals, Ag is released into soil and water through the weathering of rocks and mining activities. Silver also enters the environment by manufacturing and using Ag compounds in electroplating and photography, catalysts, medical devices, and batteries. With >400 t of Ag NPs produced yearly, Ag NPs have become a rapidly growing source of anthropogenic Ag input in the environment. In soils and natural waters, most Ag is sorbed to soil particles and sediments and precipitated as oxides, carbonates, sulphides, chlorides and hydroxides. Silver and its compounds are toxic, and humans and other animals are exposed to Ag through inhalation of air and the consumption of Ag-contaminated food and drinking water. Remediation of Ag-contaminated soil and water sources can be achieved through immobilization and mobilization processes. Immobilization of Ag in soil and groundwater reduces the bioavailability and mobility of Ag, while mobilization of Ag in the soil can facilitate its removal. This review provides an overview of the current understanding of the sources, geochemistry, health hazards, remediation practices and regulatory mandates of Ag contamination in complex environmental settings, including soil and aquatic ecosystems. Knowledge gaps and future research priorities in the sustainable management of Ag contamination in these settings are also discussed.

Multiple stressor effects on a model soil nematode, Caenorhabditis elegans: Combined effects of the pathogen Klebsiella pneumoniae and zinc oxide nanoparticles.

Research utilizing the model soil nematode Caenorhabditis elegans has revealed that agriculturally relevant nanoparticles (NP), such as zinc oxide NP (ZnONP), cause toxicity at low concentrations and disrupt molecular pathways of pathogen resistance. However, in most nanotoxicity assessments, model organisms are exposed to a single stressor but in nature organisms are affected by multiple sources of stress, including infections, which might exacerbate or mitigate negative effects of NP exposure. Thus, to expand our understanding of the environmental consequences of released NP, this project examined the synergistic/antagonistic effects of ZnONP on C. elegans infected with a common pathogen, Klebsiella pneumoniae. Individual exposures of C. elegans to ZnONP, zinc sulfate (Zn2+ ions) or K. pneumoniae significantly decreased nematode reproduction compared to controls. To assess the combined stress of ZnONP and K. pneumoniae, C. elegans were exposed to equitoxic EC30 concentrations of ZnONP (or Zn ions) and K. pneumoniae. After the combined exposure there was no decrease in reproduction. This complete elimination of reproductive toxicity was unexpected because exposures were conducted at EC30 Zn concentrations and reproductive toxicity due to Zn should have occurred. Amelioration of the pathogen effects by Zn are partially explained by the Zn impact on the K. pneumoniae biofilm. Quantitative assessments showed that external biofilm production and estimated colony forming units (CFU) of K. pneumoniae within the nematodes were significantly decreased. Taken together, our results suggest that during the combined exposure of C. elegans to both stressors Zn in ionic or particulate form inhibits K. pneumoniae ability to colonize nematode's intestine through decreasing pathogen biofilm formation. This highlights the unpredictable nature of combined stressor effects, calling into question the utility of exposures in simplified laboratory media.

Potential Environmental and Health Implications from the Scaled-Up Production and Disposal of Nanomaterials Used in Biosensors.

Biosensors often combine biological recognition elements with nanomaterials of varying compositions and dimensions to facilitate or enhance the operating mechanism of the device. While incorporating nanomaterials is beneficial to developing high-performance biosensors, at the stages of scale-up and disposal, it may lead to the unmanaged release of toxic nanomaterials. Here we attempt to foster connections between the domains of biosensors development and human and environmental toxicology to encourage a holistic approach to the development and scale-up of biosensors. We begin by exploring the toxicity of nanomaterials commonly used in biosensor design. From our analysis, we introduce five factors with a role in nanotoxicity that should be considered at the biosensor development stages to better manage toxicity. Finally, we contextualize the discussion by presenting the relevant stages and routes of exposure in the biosensor life cycle. Our review found little consensus on how the factors presented govern nanomaterial toxicity, especially in composite and alloyed nanomaterials. To bridge the current gap in understanding and mitigate the risks of uncontrolled nanomaterial release, we advocate for greater collaboration through a precautionary One Health approach to future development and a movement towards a circular approach to biosensor use and disposal.

Bioanalytical approaches for the detection, characterization, and risk assessment of micro/nanoplastics in agriculture and food systems.

This review discusses the most recent literature (mostly since 2019) on the presence and impact of microplastics (MPs, particle size of 1 µm to 5 mm) and nanoplastics (NPs, particle size of 1 to 1000 nm) throughout the agricultural and food supply chain, focusing on the methods and technologies for the detection and characterization of these materials at key entry points. Methods for the detection of M/NPs include electron and atomic force microscopy, vibrational spectroscopy (FTIR and Raman), hyperspectral (bright field and dark field) and fluorescence imaging, and pyrolysis-gas chromatography coupled to mass spectrometry. Microfluidic biosensors and risk assessment assays of MP/NP for in vitro, in vivo, and in silico models have also been used. Advantages and limitations of each method or approach in specific application scenarios are discussed to highlight the scientific and technological obstacles to be overcome in future research. Although progress in recent years has increased our understanding of the mechanisms and the extent to which MP/NP affects health and the environment, many challenges remain largely due to the lack of standardized and reliable detection and characterization methods. Most of the methods available today are low-throughput, which limits their practical application to food and agricultural samples. Development of rapid and high-throughput field-deployable methods for onsite screening of MP/NPs is therefore a high priority. Based on the current literature, we conclude that detecting the presence and understanding the impact of MP/NP throughout the agricultural and food supply chain require the development of novel deployable analytical methods and sensors, the combination of high-precision lab analysis with rapid onsite screening, and a data hub(s) that hosts and curates data for future analysis.

FEAST of biosensors: Food, environmental and agricultural sensing technologies (FEAST) in North America.

We review the challenges and opportunities for biosensor research in North America aimed to accelerate translational research. We call for platform approaches based on: i) tools that can support interoperability between food, environment and agriculture, ii) open-source tools for analytics, iii) algorithms used for data and information arbitrage, and iv) use-inspired sensor design. We summarize select mobile devices and phone-based biosensors that couple analytical systems with biosensors for improving decision support. Over 100 biosensors developed by labs in North America were analyzed, including lab-based and portable devices. The results of this literature review show that nearly one quarter of the manuscripts focused on fundamental platform development or material characterization. Among the biosensors analyzed for food (post-harvest) or environmental applications, most devices were based on optical transduction (whether a lab assay or portable device). Most biosensors for agricultural applications were based on electrochemical transduction and few utilized a mobile platform. Presently, the FEAST of biosensors has produced a wealth of opportunity but faces a famine of actionable information without a platform for analytics.

Responses of soil bacteria and fungal communities to pristine and sulfidized zinc oxide nanoparticles relative to Zn ions.

Zinc oxide nanoparticles (ZnO NPs) are attracting much interest due to their potential toxicity and ubiquity in consumer products. However, understanding of pristine and transformed ZnO NPs impact on soil microbial communities is still limited. Here, we explored changes in the microbial communities of soils treated with pristine and sulfidized ZnO NPs (s-ZnO NPs), and their corresponding Zn ions (ZnSO4) for 30 and 90 days exposures at 100 and 500 mg Zn kg-1. The similarity in bacterial community responses was observed between ZnO NPs and s-ZnO NPs, and these Zn treatments significantly affected the bacterial communities at 90 days, which exhibited distinct patterns compared to ZnSO4. The single-time tested DTPA and H2O extractable Zn ions could not fully explain the observed ZnO NPs and s-ZnO NPs impact on bacterial communities. The two most dominant phylum Nitrospirae and Actinobacteria, associated with the reduction of NH4+-N and dissolved organic carbon, demonstrated significant changes in soils exposed to ZnO NPs and s-ZnO NPs. This suggests the potential long-term impact of transformed ZnO NPs on soil carbon and nitrogen cycling. For fungal communities, we did not find the distinct response patterns of fungal communities between nanoparticulate and ionic Zn exposures.

Dual-Functional Phosphorene Nanocomposite Membranes for the Treatment of Perfluorinated Water: An Investigation of Perfluorooctanoic Acid Removal via Filtration Combined with Ultraviolet Irradiation or Oxygenation.

Nanomaterials with tunable properties show promise because of their size-dependent electronic structure and controllable physical properties. The purpose of this research was to develop and validate environmentally safe nanomaterial-based approach for treatment of drinking water including removal and degradation of per- and polyfluorinated chemicals (PFAS). PFAS are surfactant chemicals with broad uses that are now recognized as contaminants with a significant risk to human health. They are commonly used in household and industrial products. They are extremely persistent in the environment because they possess both hydrophobic fluorine-saturated carbon chains and hydrophilic functional groups, along with being oleophobic. Traditional drinking water treatment technologies are usually ineffective for the removal of PFAS from contaminated waters, because they are normally present in exiguous concentrations and have unique properties that make them persistent. Therefore, there is a critical need for safe and efficient remediation methods for PFAS, particularly in drinking water. The proposed novel approach has also a potential application for decreasing PFAS background levels in analytical systems. In this study, nanocomposite membranes composed of sulfonated poly ether ether ketone (SPEEK) and two-dimensional phosphorene were fabricated, and they obtained on average 99% rejection of perfluorooctanoic acid (PFOA) alongside with a 99% removal from the PFOA that accumulated on surface of the membrane. The removal of PFOA accumulated on the membrane surface achieved 99% after the membranes were treated with ultraviolet (UV) photolysis and liquid aerobic oxidation.

Comparison of Nanomaterials for Delivery of Double-Stranded RNA in Caenorhabditis elegans.

RNA interference is a promising crop protection technology that has seen rapid development in the past several years. Here, we investigated polyamino acid biopolymers, inorganic nanomaterials, and hybrid organic-inorganic nanomaterials for delivery of dsRNA and efficacy of gene knockdown using the model nematode Caenorhabditis elegans. Using an oral route of delivery, we are able to approximate how nanomaterials will be delivered in the environment. Of the materials investigated, only Mg-Al layered double-hydroxide nanoparticles were effective at gene knockdown in C. elegans, reducing marker gene expression to 66.8% of that of the control at the lowest tested concentration. In addition, we identified previously unreported injuries to the mouthparts of C. elegans associated with the use of a common cell-penetrating peptide, poly-l-arginine. Our results will allow the pursuit of further research into promising materials for dsRNA delivery and also allow for the exclusion of those with little efficacy or deleterious effects.

Nanohybrid Membrane Synthesis with Phosphorene Nanoparticles: A Study of the Addition, Stability and Toxicity.

Phosphorene is a promising candidate as a membrane material additive because of its inherent photocatalytic properties and electrical conductance which can help reduce fouling and improve membrane properties. The main objective of this study was to characterize structural and morphologic changes arising from the addition of phosphorene to polymeric membranes. Here, phosphorene was physically incorporated into a blend of polysulfone (PSf) and sulfonated poly ether ether ketone (SPEEK) doping solution. Protein and dye rejection studies were carried out to determine the permeability and selectivity of the membranes. Since loss of material additives during filtration processes is a challenge, the stability of phosphorene nanoparticles in different environments was also examined. Furthermore, given that phosphorene is a new material, toxicity studies with a model nematode, Caenorhabditis elegans, were carried out to provide insight into the biocompatibility and safety of phosphorene. Results showed that membranes modified with phosphorene displayed a higher protein rejection, but lower flux values. Phosphorene also led to a 70% reduction in dye fouling after filtration. Additionally, data showed that phosphorene loss was negligible within the membrane matrix irrespective of the pH environment. Phosphorene caused toxicity to nematodes in a free form, while no toxicity was observed for membrane permeates.

Epigenetic effects induced by silver nanoparticles in Caenorhabditis elegans after multigenerational exposure.

Multigenerational effects of silver nanoparticles (Ag-NPs) on reproduction of the soil nematode Caenorhabditis elegans have been observed previously. However, mechanisms of this reproductive sensitivity are unknown. Here we examine whether epigenetic changes occur as a result of multigenerational exposure to Ag-NPs and whether such modifications can be inherited by unexposed generations. Changes at histone methylation markers, histone 3 lysine 4 dimethylation (H3K4me2) and histone 3 lysine 9 trimethylation (H3K9me3), known to affect reproduction, as well as changes in the expression of the genes encoding demethylases and methyltransferases associated with the selected markers, were investigated. We exposed C. elegans at EC30 to AgNO3, pristine Ag-NPs, and its environmentally transformed product, sulfidized Ag-NPs (sAg-NPs). Histone methylation levels at H3K4me2 increase in response to pristine Ag-NP exposure and did not recover after rescue from the exposure, suggesting transgenerational inheritance. Compared to pristine Ag-NPs, exposure to transformed sAg-NPs significantly decreased H3K4me2 and H3K9me3 levels. These changes in the histone methylation were also supported by expression of spr-5 and jmjd-2 (H3K4me2 and H3K9me3 demethylases, respectively) and set-30 (H3K4me2 methyltransferase). Our study demonstrates that multigenerational exposure to Ag-NPs induces epigenetic changes that are inherited by unexposed offspring. However, environmental transformations of Ag-NPs may also reduce toxicity via epigenetic mechanisms, such as changes at histone methylation.

Genomic mutations after multigenerational exposure of Caenorhabditis elegans to pristine and sulfidized silver nanoparticles.

Our previous study showed heritable reproductive toxicity in the nematode Caenorhabditis elegans after multigenerational exposure to AgNO3 and silver nanoparticles (Ag-NPs). The aim of this study was to determine whether such inheritable effects are correlated with induced germline mutations in C. elegans. Individual C. elegans lineages were exposed for 10 generations to equitoxic concentrations at EC30 of AgNO3, Ag-NPs, and sulfidized Ag-NPs (sAg-NPs), a predominant environmentally transformed product of pristine Ag-NPs. The mutations were detected via whole genome DNA sequencing approach by comparing F0 and F10 generations. An increase in the total number of variants, though not statistically significant, was observed for all Ag treatments and the variants were mainly contributed by single nucleotide polymorphisms (SNPs). This potentially contributed towards reproductive as well as growth toxicity shown previously after ten generations of exposure in every Ag treatment. However, despite Ag-NPs and AgNO3 inducing stronger reproductive toxicity than sAg-NPs, exposure to sAg-NPs resulted in higher mutation accumulation with significant increase in the number of transversions. Thus our results suggest that other mechanisms of inheritance, such as epigenetics, may be at play in Ag-NP- and AgNO3-induced multigenerational and transgenerational reproductive toxicity.

Uptake and Bioactivity of Chitosan/Double-Stranded RNA Polyplex Nanoparticles in Caenorhabditis elegans.

In this study, we investigated chitosan/dsRNA polyplex nanoparticles as RNAi agents in the nematode Caenorhabditis elegans. By measurement of an easily observed phenotype and uptake of fluorescently labeled dsRNA, we demonstrate that chitosan/dsRNA polyplex nanoparticles are considerably more effective at gene knockdown on a whole body concentration basis than naked dsRNA. Further, we show that chitosan/dsRNA polyplex nanoparticles introduce dsRNA into cells via a different mechanism than the canonical sid-1 and sid-2 pathway. Clathrin-mediated endocytosis is likely the main uptake mechanism. Finally, although largely reported as nontoxic, we have found that chitosan, as either polyplex nanoparticles or alone, is capable of downregulating the expression of myosin. Myosin is a critical component of growth and development in eukaryotes, and we have observed reductions in both growth rate and reproduction in chitosan exposed C. elegans. Given the increased potency, noncanonical uptake, and off-target effects that we identified, these findings highlight the need for a rigorous safety assessment of nano-RNAi products prior to deployment. Specifically, the potential adverse effects of the nanocarrier and its components need to be considered.

Toxicogenomic responses of Caenorhabditis elegans to pristine and transformed zinc oxide nanoparticles.

Manufactured nanoparticles (MNPs) undergo transformation immediately after they enter wastewater treatment streams and during their partitioning to sewage sludge, which is applied to agricultural soils in form of biosolids. We examined toxicogenomic responses of the model nematode Caenorhabditis elegans to pristine and transformed ZnO-MNPs (phosphatized pZnO- and sulfidized sZnO-MNPs). To account for the toxicity due to dissolved Zn, a ZnSO4 treatment was included. Transformation of ZnO-MNPs reduced their toxicity by nearly ten-fold, while there was almost no difference in the toxicity of pristine ZnO-MNPs and ZnSO4. This combined with the fact that far more dissolved Zn was released from ZnO- compared to pZnO- or sZnO-MNPs, suggests that dissolution of pristine ZnO-MNPs is one of the main drivers of their toxicity. Transcriptomic responses at the EC30 for reproduction resulted in a total of 1161 differentially expressed genes. Fifty percent of the genes differentially expressed in the ZnSO4 treatment, including the three metal responsive genes (mtl-1, mtl-2 and numr-1), were shared among all treatments, suggesting that responses to all forms of Zn could be partially attributed to dissolved Zn. However, the toxicity and transcriptomic responses in all MNP treatments cannot be fully explained by dissolved Zn. Two of the biological pathways identified, one essential for protein biosynthesis (Aminoacyl-tRNA biosynthesis) and another associated with detoxification (ABC transporters), were shared among pristine and one or both transformed ZnO-MNPs, but not ZnSO4. When comparing pristine and transformed ZnO-MNPs, 66% and 40% of genes were shared between ZnO-MNPs and sZnO-MNPs or pZnO-MNPs, respectively. This suggests greater similarity in transcriptomic responses between ZnO-MNPs and sZnO-MNPs, while toxicity mechanisms are more distinct for pZnO-MNPs, where 13 unique biological pathways were identified. Based on these pathways, the toxicity of pZnO-MNPs is likely to be associated with their adverse effect on digestion and metabolism.

Different patterns of colonization of Oxalis alpina in the Sky Islands of the Sonoran desert via pollen and seed flow.

Historical factors such as climatic oscillations during the Pleistocene epoch have dramatically impacted species distributions. Studies of the patterns of genetic structure in angiosperm species using molecular markers with different modes of inheritance contribute to a better understanding of potential differences in colonization and patterns of gene flow via pollen and seeds. These markers may also provide insights into the evolution of reproductive systems in plants. Oxalis alpina is a tetraploid, herbaceous species inhabiting the Sky Island region of the southwestern United States and northern Mexico. Our main objective in this study was to analyze the influence of climatic oscillations on the genetic structure of O. alpina and the impact of these oscillations on the evolutionary transition from tristylous to distylous reproductive systems. We used microsatellite markers and compared our results to a previous study using chloroplast genetic markers. The phylogeographic structure inferred by both markers was different, suggesting that intrinsic characteristics including the pollination system and seed dispersal have influenced patterns of gene flow. Microsatellites exhibited low genetic structure, showed no significant association between geographic and genetic distances, and all individual genotypes were assigned to two main groups. In contrast, chloroplast markers exhibited a strong association between geographic and genetic distance, had higher levels of genetic differentiation, and were assigned to five groups. Both types of DNA markers showed evidence of a northward expansion as a consequence of climate warming occurring in the last 10,000 years. The data from both types of markers support the hypothesis for several independent transitions from tristyly to distyly.

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.

Effects of biosolids from a wastewater treatment plant receiving manufactured nanomaterials on Medicago truncatula and associated soil microbial communities at low nanomaterial concentrations.

Concern has grown regarding engineered nanomaterials (ENMs) entering agricultural soils through the application of biosolids and their possible effects on agroecosystems, even though the ENMs are extensively transformed. The effects of exposure to biosolids containing transformation products of these ENMs at low concentrations remain largely unexplored. We examined the responses of Medicago truncatula and its symbiotic rhizobia Sinorhizobium meliloti exposed to soil amended with biosolids from WWTP containing low added concentrations of ENMs (ENM Low), bulk/dissolved metals (bulk/dissolved Low), or no metal additions (control). We targeted adding approximately 5mg/kg of Ag and 50mg/kg of Zn, and Ti. Measured endpoints included M. truncatula growth, nodulation, changes in the expression of stress response genes, uptake of metals (Ag, Zn and Ti) into shoots, and quantification of S. meliloti populations and soil microbial communities. After 30days exposure, no effects on root or shoot biomass were observed in ENM Low and bulk/dissolved Low treatments, whereas both treatments had a larger average number of nodules (5.7 and 5.57, respectively) compared to controls (0.33). There were no significant differences in either total accumulated metal or metal concentrations in shoots among the treatments. Expression of five stress-related genes (metal tolerance protein (MTP), metal transporter (MTR), peroxidase (PEROX), NADPH oxidase (NADPH) and 1-aminocyclopropane-1-carboxylate oxidase-like protein (ACC_Oxidase)) was significantly down-regulated in both bulk/dissolved Low and ENM Low treatments. However, a change in soil microbial community composition and a significant increase in total microbial biomass were observed in ENM Low relative to control. The ENM Low treatment had increased abundance of Gram-negative and anaerobic bacteria and reduced abundance of eukaryotes compared to control. The study demonstrated that although there were some subtle shifts in microbial community composition, plant health was minimally impacted by ENMs within the time frame and at the low exposure concentrations used in this study.