Engineered Nanomaterials Research Articles

Challenges and opportunities in the application of bioinspired engineered nanomaterials for the recovery of metal ions from mining industry wastewater

Heavy-metal-bearing wastewater is among the most formidable challenges the mining industry currently faces in maintaining its social license to operate. Amongst the technologies available for metal ion adsorption, bioinspired engineering nanomaterials have emerged as one which exhibits great promise. However, current processes used for the preparation of adsorbents (including nanoscale activated carbon and biochar) represent a source of adverse impacts on the environment. In contrast, the application of biogenic-nanoparticles, i.e., those derived from processes catalysed by microbiota, has received significant attention in the last few years. Coupled with this, the use of naturally occurring reagents is of major importance for the sustainability of this emerging industry. This paper analyses the life cycle assessment (LCA) of the synthesis of adsorbents derived from agricultural wastes. Moreover, rather than simply recovering the ecotoxic metals from wastewater, the potential to valorise dissolved metals into high-value metallic nanoparticle products is discussed. LCA analysis revealed that the adsorbent had some adverse impact on the environment. The agricultural wastes contributed 27.86% to global warming, 54.64% to ozone formation, 33.06% to fine particles, and 98.24% to marine eutrophication. Mining wastewater is an important, and largely currently unexploited, source of metal value. However, the often-low concentration of such metals dictates that their conversion into high-value products (such as engineered nanoparticles) is an important new research frontier. Within this the use of biosynthesis methods has emerged as having great potential due to a range of beneficial attributes, including low cost, high efficacy and/or environmental compatibility.

Nanomaterials and environmental antimicrobial resistance: Propagation and inhibition of antibiotic resistance gene flow in the soil-plant system

<p indent="0mm">The propagation of antibiotic resistance genes (ARGs), one of the emerging contaminants threatening global sanitation and health, has called for the necessity to overcome the spread of antimicrobial resistance (AMR). ARGs derived from manure is the main source of AMR in agricultural soil that can be propagated rapidly in soil-plant system and finally into food chain via horizontal gene transfer (HGT), which mainly includes three pathways mediated by mobile genetic elements (MGEs), namely, plasmid-mediated conjugation, extracellular DNA-mediated transformation, and phage- mediated transduction. The massive production and wide application of engineered nanomaterials (ENMs) and micro(nano) plastics have resulted in increasing concentrations of ENMs and micro(nano) plastics in the environment, which will eventually enter the soil and lead to migration and propagation of ARGs in soil-plant system. Bacterial pure culture studies reported that ENMs can exacerbate the dissemination of ARGs via changing intracellular reactive oxygen species (ROS), cell membrane permeability, and expression of genes related to conjugation. Moreover, ENMs and micro(nano) plastics in soil can change the soil antibiotic resistome and plant root morphology, structure and root exudates, which may affect the migration of ARB and ARGs from the rhizosphere to plants. The interactions between ENMs/micro(nano) plastics and ARGs might drive the development of multidrug resistance in soil-plant system. Although research targeting the effects of ENMs/micro(nano) plastics on the fate of ARGs is growing, an overview of biological impact and related mechanism is somehow lacking. In this review article, we systematically reviewed the interaction between ENMs/micro(nano) plastics and ARGs, especially in soil-plant system and attempted to explore the possibilities of nanotechnology to inhibit the transfer of antibiotic resistance gene flow. This review mainly covers: (1) Molecular mechanisms of ENMs and micro(nano) plastics regulating ARGs propagation. ENMs (i.e., Ag ENMs, CuO ENMs, TiO₂/Ag/GO ENMs and nano-graphene oxide) can promote ARGs propagation by accumulating intracellular reactive oxygen species (ROS), increasing cell membrane permeability and up-regulating of conjugation-related gene expression. However, CeO₂ ENMs and Fe₂O₃@MoS₂ ENMs have the potential to inhibit the propagation of ARGs via ROS elimination and down-regulating expression of HGT-related genes. (2) Influence of ENMs/micro(nano) plastics on ARGs in soil-plant system. ENMs/micro(nano) plastics can alter soil bacterial community and affect plant growth which will likely reduce the horizontal transfer of ARGs in soil by inhibiting the growth of soil microorganisms, reducing the abundance and diversity of ARB in soil, or changing the amount and composition of root exudates. (3) Application of nanotechnology on inhibiting antibiotic resistance gene flow. The regulatory mechanisms of nanotechnology on ARGs can be classified as: Inhibition of HGT, change of bacterial community composition, adsorption/degradation on ARGs and antimicrobial performance. Nanotechnology is promising for eliminating ARGs with high accuracy while its high cost and instability remain to be solved. For future study, more attention should be paid on the management of antibiotics, ARB and ARGs and the establishment of AMR risk assessment system to comprehensively assess the potential risk of AMR propagation via soil-plant-human pathways. Besides, the propagation of ARGs regulated by ENMs might be a challenge to distinguish and balance the advantages and disadvantages of ENMs in soil-plant system. Thus, it is urgent to comprehensively and systematically assess the environmental behavior and ecological risks of ENMs and micro(nano) plastics, contributing to the safe and efficient nano-based reduction of AMR.

Representing and describing nanomaterials in predictive nanoinformatics

Engineered nanomaterials (ENMs) enable new and enhanced products and devices in which matter can be controlled at a near-atomic scale (in the range of 1 to 100 nm). However, the unique nanoscale properties that make ENMs attractive may result in as yet poorly known risks to human health and the environment. Thus, new ENMs should be designed in line with the idea of safe-and-sustainable-by-design (SSbD). The biological activity of ENMs is closely related to their physicochemical characteristics, changes in these characteristics may therefore cause changes in the ENMs activity. In this sense, a set of physicochemical characteristics (for example, chemical composition, crystal structure, size, shape, surface structure) creates a unique 'representation' of a given ENM. The usability of these characteristics or nanomaterial descriptors (nanodescriptors) in nanoinformatics methods such as quantitative structure-activity/property relationship (QSAR/QSPR) models, provides exciting opportunities to optimize ENMs at the design stage by improving their functionality and minimizing unforeseen health/environmental hazards. A computational screening of possible versions of novel ENMs would return optimal nanostructures and manage ('design out') hazardous features at the earliest possible manufacturing step. Safe adoption of ENMs on a vast scale will depend on the successful integration of the entire bulk of nanodescriptors extracted experimentally with data from theoretical and computational models. This Review discusses directions for developing appropriate nanomaterial representations and related nanodescriptors to enhance the reliability of computational modelling utilized in designing safer and more sustainable ENMs.

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

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

Exploring the potential of in silico machine learning tools for the prediction of acute Daphnia magna nanotoxicity

Engineered nanomaterials (ENMs) are ubiquitous nowadays, finding their application in different fields of technology and various consumer products. Virtually any chemical can be manipulated at the nano-scale to display unique characteristics which makes them appealing over larger sized materials. As the production and development of ENMs have increased considerably over time, so too have concerns regarding their adverse effects and environmental impacts. It is unfeasible to assess the risks associated with every single ENM through in vivo or in vitro experiments. As an alternative, in silico methods can be employed to evaluate ENMs. To perform such an evaluation, we collected data from databases and literature to create classification models based on machine learning algorithms in accordance with the principles laid out by the OECD for the creation of QSARs. The aim was to investigate the performance of various machine learning algorithms towards predicting a well-defined in vivo toxicity endpoint (Daphnia magna immobilization) and also to identify which features are important drivers of D. magna in vivo nanotoxicity. Results indicated highly comparable model performance between all algorithms and predictive performance exceeding ∼0.7 for all evaluated metrics (e.g. accuracy, sensitivity, specificity, balanced accuracy, Matthews correlation coefficient, area under the receiver operator characteristic curve). The random forest, artificial neural network, and k-nearest neighbor models displayed the best performance but this was only marginally better compared to the other models. Furthermore, the variable importance analysis indicated that molecular descriptors and physicochemical properties were generally important within most models, while features related to the exposure conditions produced slightly conflicting results. Lastly, results also indicate that reliable and robust machine learning models can be generated for in vivo endpoints with smaller datasets.

Neurotoxicity of Engineered Nanomaterials: Testing Considerations.

As with toxicology in general, major challenges have emerged in its subfield neurotoxicology regarding the testing of engineered nanomaterials (ENM). This is on the one hand due to their complex physicochemical properties, like size, specific surface area, chemical composition as well as agglomeration and dissolution behavior in biological environments. On the other hand, toxicological risk assessment has faced an increasing demand for the development and implementation of non-animal alternative approaches. Regarding the investigation and interpretation of the potential adverse effects of ENM on the brain, toxicokinetic data are relatively scarce and thus hampers dose selection for in vitro neurotoxicity testing. Moreover, recent in vivo studies indicate that ENM can induce neurotoxic and behavioral effects in an indirect manner, depending on their physicochemical properties and route of exposure. Such indirect effects on the brain may proceed through the activation and spill-over of inflammatory mediators by ENM in the respiratory tract and other peripheral organs as well via ENM induced disturbance of the gut microbiome and intestinal mucus barrier. These ENM specific aspects should be incorporated into the ongoing developments of advanced in vitro neurotoxicity testing methods and strategies.

Biomarkers of nanomaterials hazard from multi-layer data

There is an urgent need to apply effective, data-driven approaches to reliably predict engineered nanomaterial (ENM) toxicity. Here we introduce a predictive computational framework based on the molecular and phenotypic effects of a large panel of ENMs across multiple in vitro and in vivo models. Our methodology allows for the grouping of ENMs based on multi-omics approaches combined with robust toxicity tests. Importantly, we identify mRNA-based toxicity markers and extensively replicate them in multiple independent datasets. We find that models based on combinations of omics-derived features and material intrinsic properties display significantly improved predictive accuracy as compared to physicochemical properties alone.

Local Scale Exposure and Fate of Engineered Nanomaterials.

Nanotechnology is a growing megatrend in industrial production and innovations. Many applications utilize engineered nanomaterials (ENMs) that are potentially released into the atmospheric environment, e.g., via direct stack emissions from production facilities. Limited information exists on adverse effects such ENM releases may have on human health and the environment. Previous exposure modeling approaches have focused on large regional compartments, into which the released ENMs are evenly mixed. However, due to the localization of the ENM release and removal processes, potentially higher airborne concentrations and deposition fluxes are obtained around the production facilities. Therefore, we compare the ENM concentrations from a dispersion model to those from the uniformly mixed compartment approach. For realistic release scenarios, we based the modeling on the case study measurement data from two TiO nanomaterial handling facilities. In addition, we calculated the distances, at which 50% of the ENMs are deposited, serving as a physically relevant metric to separate the local scale from the regional scale, thus indicating the size of the high exposure and risk region near the facility. As a result, we suggest a local scale compartment to be implemented in the multicompartment nanomaterial exposure models. We also present a computational tool for local exposure assessment that could be included to regulatory guidance and existing risk governance networks.

An analytical workflow for dynamic characterization and quantification of metal-bearing nanomaterials in biological matrices.

To assess the safety of engineered nanomaterials (ENMs) and to evaluate and improve ENMs' targeting ability for medical application, it is necessary to analyze the fate of these materials in biological media. This protocol presents a workflow that allows researchers to determine, characterize and quantify metal-bearing ENMs (M-ENMs) in biological tissues and cells and quantify their dynamic behavior at trace-level concentrations. Sample preparation methods to enable analysis of M-ENMs in a single cell, a cell layer, tissue, organ and physiological media (e.g., blood, gut content, hemolymph) of different (micro)organisms, e.g., bacteria, animals and plants are presented. The samples are then evaluated using fit-for-purpose analytical techniques e.g., single-cell inductively coupled plasma mass spectrometry, single-particle inductively coupled plasma mass spectrometry and synchrotron X-ray absorption fine structure, providing a protocol that allows comprehensive characterization and quantification of M-ENMs in biological matrices. Unlike previous methods, the protocol uses no fluorescent dyes or radiolabels to trace M-ENMs in biota and enables analysis of most M-ENMs at cellular, tissue and organism levels. The protocols can be applied by a wide variety of users depending on the intended purpose of the application, e.g., to correlate toxicity with a specific particle form, or to understand the absorption, distribution and excretion of M-ENMs. The results facilitate an understanding of the biological fate of M-ENMs and their dynamic behavior in biota. Performing the protocol may take 7-30 d, depending on which combination of methods is applied.

Comparative assessment of oxygen uptake rate of activated sludge and Escherichia coli exposed to nanomaterials.

The adverse effects of engineered nanomaterials (ENMs) on bacterial populations found in wastewater treatment plants (WWTPs) or natural systems have been studied for more than a decade, but conflicting evidence on the matter still makes it a subject of considerable concern. In this paper, the short-term exposure impact of titanium dioxide nanoparticles (nTiO2), carboxyl-functionalized multiwall carbon nanotubes (f-MWCNT), and zero-valent iron nanoparticles (nZVI) toward activated sludge and Escherichia coli (E. coli) was investigated through respiration inhibition experiments. Microorganisms were exposed to nanoparticle concentrations of 50, 100 and 200 mg/L (nTiO2, f-MWCNT) and 20, 50 and 100 mg/L (nZVI). The experiments showed that nTiO2 produced no inhibition in activated sludge or E. coli; up to 100 mg/L of nZVI did not inhibit the activated sludge respiration but 50 mg/L inhibited 24 ± 3% the respiration of E. coli and damaged its cell membrane. Activated sludge respiration was inhibited 17 ± 3% with 200 mg/L of f-MWCNT while for E. coli the inhibition was 36 ± 15% and the cell membrane was damaged with a 100 mg/L dose. Transmission electron microscopy (TEM) showed nTiO2-bacteria and nZVI-bacteria surface interaction while bacteria appeared punctured by f-MWCNT. E. coli was more susceptible than activated sludge to the nanomaterials and nZVI was more toxic than f-MWCNT for E. coli. These results demonstrated the absence of acute toxicity effects of the studied nanomaterials at those concentrations expected to occur in activated sludge facilities, and it would only be a concern in case of extremely high inputs, underscoring the resilience of WWTPs biological treatment.

Characterization of ENM Dynamic Dose-Dependent MOA in Lung with Respect to Immune Cells Infiltration.

The molecular effects of exposures to engineered nanomaterials (ENMs) are still largely unknown. In classical inhalation toxicology, cell composition of bronchoalveolar lavage (BAL) is a toxicity indicator at the lung tissue level that can aid in interpreting pulmonary histological changes. Toxicogenomic approaches help characterize the mechanism of action (MOA) of ENMs by investigating the differentially expressed genes (DEG). However, dissecting which molecular mechanisms and events are directly induced by the exposure is not straightforward. It is now generally accepted that direct effects follow a monotonic dose-dependent pattern. Here, we applied an integrated modeling approach to study the MOA of four ENMs by retrieving the DEGs that also show a dynamic dose-dependent profile (dddtMOA). We further combined the information of the dddtMOA with the dose dependency of four immune cell populations derived from BAL counts. The dddtMOA analysis highlighted the specific adaptation pattern to each ENM. Furthermore, it revealed the distinct effect of the ENM physicochemical properties on the induced immune response. Finally, we report three genes dose-dependent in all the exposures and correlated with immune deregulation in the lung. The characterization of dddtMOA for ENM exposures, both for apical endpoints and molecular responses, can further promote toxicogenomic approaches in a regulatory context.

Exposure Assessment of Silver and Gold Nanoparticles Generated During the Synthesis Process in a South African Research Laboratory.

During the synthesis of engineered nanomaterials (ENMs), various occupational exposures occur, leading to health consequences. To date, there is paucity of studies focused on modeling the deposition of nanoparticles emitted from ENMs synthesis processes. This study aimed to characterise and assess exposure to gold (AuNPs) and silver nanoparticles (AgNPs) during a synthesis process in a research laboratory in South Africa. AuNPs and AgNPs synthesis processes were monitored for an hour in a laboratory using a Scanning Mobility Particle Sizer. The monitoring was conducted at a height of 1.2–1.5 m (m) and 1.5 m away from the hood, assuming a 30 cm (cm) breathing circumference zone. Each synthesis process was monitored thrice to generate reliable point estimates, which were used to assess exposure over 8 hours. A time-weighted average concentration was calculated and compared to the derived 8-h occupational exposure limit (OEL) for AgNPs (0.19 μg/m3) and the proposed provisional nano reference value for AuNPs (20,000 particles/cm3). The Multiple-Path Particle Dosimetry model was used to calculate the deposition and retention of both AuNPs and AgNPs. NPs emitted during the synthesis process were dominant in the nuclei (79% for AuNPs and 54% for AgNPs), followed by the Aitken (12% for AuNPs and 29% for AgNPs), with fewer particles in the accumulation mode (9.2% for AuNPs and 17% for AgNPs). AuNPs and AgNPs generated during the synthesis process were determined at 1617.3 ± 102 cm3 (0.046 μg/m3) and 2,687 cm3 ± 620 (0.077 μg/m3), respectively. For the three exposure scenarios, none exceeded the occupational exposure limit for both AuNPs (provisional) and AgNPs (OEL). Workers in the synthesis laboratory are exposed to a concentration below the recommended occupational exposure limit for silver and the proposed provisional nano reference value for gold. Although, the concentrations to which laboratory workers are exposed to are below safe levels, the assessment of the lung deposition patterns indicate a high particle lung retention which raise concerns about long term safety of workers.

Pathways Related to NLRP3 Inflammasome Activation Induced by Gold Nanorods.

The widespread and increasing use of engineered nanomaterials (ENM) increases the risk of human exposure, generating concern that ENM may provoke adverse health effects. In this respect, their physicochemical characteristics are critical. The immune system may respond to ENM through inflammatory reactions. The NLRP3 inflammasome responds to a wide range of ENM, and its activation is associated with various inflammatory diseases. Recently, anisotropic ENM have become of increasing interest, but knowledge of their effects on the immune system is still limited. The objective of the study was to compare the effects of gold ENM of different shapes on NLRP3 inflammasome activation and related signalling pathways. Differentiated THP-1 cells (wildtype, ASC- or NLRP3-deficient), were exposed to PEGylated gold nanorods, nanostars, and nanospheres, and, thus, also different surface chemistries, to assess NLRP3 inflammasome activation. Next, the exposed cells were subjected to gene expression analysis. Nanorods, but not nanostars or nanospheres, showed NLRP3 inflammasome activation. ASC- or NLRP3-deficient cells did not show this effect. Gene Set Enrichment Analysis revealed that gold nanorod-induced NLRP3 inflammasome activation was accompanied by downregulated sterol/cholesterol biosynthesis, oxidative phosphorylation, and purinergic receptor signalling. At the level of individual genes, downregulation of Paraoxonase-2, a protein that controls oxidative stress, was most notable. In conclusion, the shape and surface chemistry of gold nanoparticles determine NLRP3 inflammasome activation. Future studies should include particle uptake and intracellular localization.

Dissolution Rate of Nanomaterials Determined by Ions and Particle Size under Lysosomal Conditions: Contributions to Standardization of Simulant Fluids and Analytical Methods.

Dissolution of inhaled engineered nanomaterials (ENM) under physiological conditions is essential to predict the clearance of the ENM from the lungs and to assess their biodurability and the potential effects of released ions. Alveolar macrophage (AM) lysosomes contain a pH 4.5 saline brine with enzymes and other components. Different types of artificial phagolysosomal simulant fluids (PSFs) have been developed for dissolution testing, but the consequence of using different media is not known. In this study, we tested to which extent six fundamentally different PSFs affected the ENM dissolution kinetics and particle size as determined by a validated transmission electron microscopy (TEM) image analysis. Three lysosomal simulant media were consistent with each other and with in vivo clearance. These media predict the quick dissolution of ZnO, the partial dissolution of SiO2, and the very slow dissolution of TiO2. The valid media use either a mix of organic acids (with the total concentration below 0.5 g/L, thereof citric acid below 0.15 g/L) or another organic acid (KH phthalate). For several ENM, including ZnO, BaSO4, and CeO2, all these differences induce only minor modulation of the dissolution rates. Only for TiO2 and SiO2, the interaction with specific organic acids is highly sensitive, probably due to sequestration of the ions, and can lead to wrong predictions when compared to the in vivo behavior. The media that fail on TiO2 and SiO2 dissolution use citric acid at concentrations above 5 g/L (up to 28 g/L). In the present selection of ENM, fluids, and methods, the different lysosomal simulant fluids did not induce changes of particle morphology, except for small changes in SiO2 and BaSO4 particles most likely due to ion dissolution, reprecipitation, and coalescence between neighboring particles. Based on the current evidence, the particle size by TEM analysis is not a sufficiently sensitive analytical method to deduce the rate of ENM dissolution in physiological media. In summary, we recommend the standardization of ENM dissolution testing by one of the three valid lysosomal simulant fluids with determination of the dissolution rate and halftime by the quantification of ions. This recommendation was established for a continuous flow system but may be relevant as well for static (batch) solubility testing.

Nanomaterials Induced Genotoxicity in Plant: Methods and Strategies.

In recent years, plant-nanomaterial interactions have been studied, highlighting their effects at physiological and molecular levels. Transcriptomics and proteomics studies have shown pathways and targets of nanomaterial exposure and plant response, with particular regard to abiotic stress and oxidative stress. Only little information has been reported on engineered nanomaterial (ENMs) interactions with plant genetic material, both at a genomic and organellar DNAs level. Plants can be useful experimental material, considering they both contain chloroplast and mitochondrial DNAs and several plant genomes have been completely sequenced (e.g., Arabidopsis thaliana, Solanum lycoperiscum, Allium cepa, Zea mays, etc.). In this mini review, the methods and the evidence reported in the present literature concerning the level of genotoxicity induced by ENMs exposure have been considered. Consolidated and potential strategies, which can be applied to assess the nanomaterial genotoxicity in plants, are reviewed.

ZnO/γ-Fe2O3/Bentonite: An Efficient Solar-Light Active Magnetic Photocatalyst for the Degradation of Pharmaceutical Active Compounds.

For applications related to the photocatalytic degradation of environmental contaminants, engineered nanomaterials (ENMs) must demonstrate not only a high photocatalytic potential, but also a low tendency to agglomeration, along with the ability to be easily collected after use. In this manuscript, a two-step process was implemented for the synthesis of ZnO, ZnO/Bentonite and the magnetic ZnO/γ-Fe2O3/Bentonite nanocomposite. The synthesized materials were characterized using various techniques, and their performance in the degradation of pharmaceutical active compounds (PhACs), including ciprofloxacin (CIP), sulfamethoxazole (SMX), and carbamazepine (CBZ) was evaluated under various operating conditions, namely the type and dosage of the applied materials, pH, concentration of pollutants, and their appearance form in the medium (i.e., as a single pollutant or as a mixture of PhACs). Among the materials studied, ZnO/Bentonite presented the best performance and resulted in the removal of ~95% of CIP (5 mg/L) in 30 min, at room temperature, near-neutral pH (6.5), ZnO/Bentonite dosage of 0.5 g/L, and under solar light irradiation. The composite also showed a high degree of efficiency for the simultaneous removal of CIP (~98%, 5 mg/L) and SMX (~97%, 5 mg/L) within 30 min, while a low degradation of ~5% was observed for CBZ (5 mg/L) in a mixture of the three PhACs. Furthermore, mechanistic studies using different types of scavengers revealed the formation of active oxidative species responsible for the degradation of CIP in the photocatalytic system studied with the contribution of h+ (67%), OH (18%), and ·O2− (10%), and in which holes (h+) were found to be the dominant oxidative species.

Metallic Engineered Nanomaterials and Ocular Toxicity: A Current Perspective.

The ocular surface, comprised of the transparent cornea, conjunctiva, and protective tear film, forms a protective barrier defending deeper structures of the eye from particulate matter and mechanical trauma. This barrier is routinely exposed to a multitude of naturally occurring and engineered nanomaterials (ENM). Metallic ENMs are particularly ubiquitous in commercial products with a high risk of ocular exposure, such as cosmetics and sunscreens. Additionally, there are several therapeutic uses for metallic ENMs owing to their attractive magnetic, antimicrobial, and functionalization properties. The increasing commercial and therapeutic applications of metallic ENMs come with a high risk of ocular exposure with poorly understood consequences to the health of the eye. While the toxicity of metallic ENMs exposure has been rigorously studied in other tissues and organs, further studies are necessary to understand the potential for adverse effects and inform product usage for individuals whose ocular health may be compromised by injury, disease, or surgical intervention. This review provides an update of current literature on the ocular toxicity of metallic ENMs in vitro and in vivo, as well as the risks and benefits of therapeutic applications of metallic ENMs in ophthalmology.

Impact of sulfhydryl ligands on the transformation of silver ions by molybdenum disulfide and their combined toxicity to freshwater algae

The transformation of silver ions (Ag+) mediated by engineered nanomaterials (ENMs) influences the biosafety of Ag-containing products in natural environments. Actually, modification of biomolecules to ENMs in aquatic ecosystems alters their interactions with Ag+. This study discovered that surface functionalization of glutathione (GSH, a sulfhydryl compound ubiquitous in natural waters) on molybdenum disulfide (MoS2) nanoflakes suppressed the redox reaction between 1 T components and Ag+, inhibiting the MoS2-mediated reduction of Ag+ to Ag nanoparticles (AgNPs) in aqueous phase in the dark. However, AgNPs formation (from 2.32 ± 0.35–3.25 ± 0.29 mg/L per day, pH 7.0) and oxidation of MoS2 were remarkably accelerated after GSH binding under light conditions. The dominant electron donator of MoS2 to Ag+ was transformed from the electron-hole pairs to surface ligands driven by the introduction of chromophoric groups was authenticated as the cause for the elevated Ag+ reduction. These processes also occurred between Ag+ and MoS2 at low levels (50 μg/L). Additionally, the joint algal toxicity of GSH-modified MoS2 with Ag+ was weaker than that of pristine MoS2 due to increased retention of free Ag+ and AgNPs formation. Our findings improve the understanding of the interaction between ENMs and Ag+ in aquatic ecosystems.

Environmental Fate of Metal Nanoparticles in Estuarine Environments

In the last decade, metal engineered nanomaterials (ENMs) have seen an exponential use in many critical technologies and products, as well an increasing release into the environment. Coastal ecosystems worldwide may receive ENM-polluted waters and wastes, with a consequent alteration of habitats and contamination of aquatic biota. There is a scarcity of data regarding the fate of these emerging contaminants in such environments. Open issues include the determination of the sources, the quantification of the interactions with marine sediments, the bioaccumulation pathways, the ecotoxicology on marine fauna and the identification of the principal biotic and abiotic factors that may alter metal ENMs toxicity. Little is known about their potential transference into the food web, as well toxicity features and co-stressors of single or multiple ENMs under laboratory and real environmental conditions for various taxonomic phyla. This review reports current knowledge on the ecological impact of ENMs under the complex environmental conditions of estuary systems, identifies gaps in current knowledge and provides directions for future research.

An Integrated Testing Strategy for Ecotoxicity (ITS-ECO) Assessment in the Marine Environmental Compartment using Mytilus spp.: A Case Study using Pristine and Coated CuO and TiO2 Nanomaterials.

An integrated testing strategy for ecotoxicity assessment (ITS‐ECO) was developed to aid in the hazard and fate assessment of engineered nanomaterials (ENMs) deposited in marine environments using the bivalve Mytilus spp. as a test species. The ENMs copper(II) oxide (CuO) and titanium dioxide (TiO2), either in pristine form (core) or with functionalized coatings (polyethylene glycol [PEG], carboxyl [COOH], and ammonia [NH3]) were selected as case study materials based on their production levels and use. High‐throughput in vitro testing in Tier 1 of the ITS‐ECO revealed CuO ENMs to elicit cytotoxic effects on lysosomes of hemocytes of mussels, with the hazard potential CuO PEG > CuO COOH > CuO NH3 > CuO core, whereas TiO2 ENMs were not cytotoxic. Genotoxicity in hemocytes as well as gill cells of mussels following in vivo exposure (48 h) to CuO ENMs was also seen. Longer in vivo exposures in Tier 2 (48 h–21 days) revealed subacute and chronic oxidative effects for both CuO and TiO2 ENMs, in some cases leading to lipid peroxidation (core TiO2 ENMs). In Tier 3 bioaccumulation studies, distinct patterns of uptake for Cu (predominantly in gills) and Ti (predominantly in digestive glands) and between the different core and coated ENMs were found. Clear NM‐specific and coating‐dependent effects on hazard and fate were seen. Overall, using a tiered testing approach, the ITS‐ECO was able to differentiate the hazard (acute, subacute, and chronic effects) posed by ENMs of different compositions and coatings and to provide information on fate for environmental risk assessment of these ENMs. Environ Toxicol Chem 2022;41:1390–1406. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.