Particle number-based trophic transfer of gold nanomaterials in an aquatic food chain

Effects of dissolved organic matter on the environmental behavior and toxicity of metal nanomaterials: A review

Metal nanomaterials (MNMs) have been released into the environment during their usage in various products, and their environmental behaviors directly impact their toxicity. Numerous environmental factors potentially affect the behaviors and toxicity of MNMs with dissolved organic matter (DOM) playing the most essential role. Abundant facts showing contradictory results about the effects of DOM on MNMs, herein the occurrence of DOM on the environmental process change of MNMs such as dissolution, dispersion, aggregation, and surface transformation were summarized. We also reviewed the effects of MNMs on organisms and their mechanisms in the environment such as acute toxicity, oxidative stress, oxidative damage, growth inhibition, photosynthesis, reproductive toxicity, and malformation. The presence of DOM had the potential to reduce or enhance the toxicity of MNMs by altering the reactive oxygen species (ROS) generation, dissolution, stability, and electrostatic repulsion of MNMs. Furthermore, we summarized the factors that affected different toxicity including specific organisms, DOM concentration, DOM types, light conditions, detection time, and production methods of MNMs. However, the more detailed mechanism of interaction between DOM and MNMs needs further investigation.

Tracking the Cellular Degradation of Silver Nanoparticles: Development of a Generic Kinetic Model

Understanding the degradation of nanoparticles (NPs) after crossing the cell plasma membrane is crucial in drug delivery designs and cytotoxicity assessment. However, the key factors controlling the degradable kinetics remain unclear due to the absence of a quantification model. In this study, subcellular imaging of silver nanoparticles (AgNPs) was used to determine the intracellular transfer of AgNPs, and single particle ICP-MS was utilized to track the degradation process. A cellular kinetic model was subsequently developed to describe the uptake, transfer, and degradation behaviors of AgNPs. Our model demonstrated that the intracellular degradation efficiency of AgNPs was much higher than that determined by mimicking testing, and the degradation of NPs was highly influenced by cellular factors. Specifically, deficiencies in Ca or Zn primarily decreased the kinetic dissolution of NPs, while a Ca deficiency also resulted in the retardation of NP transfer. The biological significance of these kinetic parameters was strongly revealed. Our model indicated that the majority of internalized AgNPs dissolved, with the resulting ions being rapidly depurated. The release of Ag ions was largely dependent on the microvesicle-mediated route. By changing the coating and size of AgNPs, the model results suggested that size influenced the transfer of NPs into the degradation process, whereas coating affected the degradation kinetics. Overall, our developed model provides a valuable tool for understanding and predicting the impacts of the physicochemical properties of NPs and the ambient environment on nanotoxicity and therapeutic efficacy.

Ecotoxicity and trophic transfer of metallic nanomaterials in aquatic ecosystems

Metallic nanomaterials (MNMs) possess unique properties that have led to their widespread application in fields such as electronics and medicine. However, concerns about their interactions with environmental factors and potential toxicity to aquatic life have emerged. There is growing evidence suggesting MNMs can have detrimental effects on aquatic ecosystems, and are potential for bioaccumulation and biomagnification in the food chain, posing risks to higher trophic levels and potentially humans. While many studies have focused on the general ecotoxicity of MNMs, fewer have delved into their trophic transfer within aquatic food chains. This review highlights the ecotoxicological effects of MNMs on aquatic systems via waterborne exposure or dietary exposure, emphasizing their accumulation and transformation across the food web. Biomagnification factor (BMF), the ratio of the contaminant concentration in predator to that in prey, was used to evaluate the biomagnification due to the complex nature of aquatic food chains. However, most current studies have BMF values of less than 1 indicating no biomagnification. Factors influencing MNM toxicity in aquatic environments include nanomaterial properties, ion variations, light, dissolved oxygen, and pH. The multifaceted interactions of these variables with MNM toxicity remain to be fully elucidated. We conclude with recommendations for future research directions to mitigate the adverse effects of MNMs in aquatic ecosystems and advocate for a cautious approach to the production and application of MNMs.

Critical evaluation of the potential of ICP-MS-based systems in toxicological studies of metallic nanoparticles

The extensive application of metallic nanoparticles (NPs) in several fields has significantly impacted our daily lives. Nonetheless, uncertainties persist regarding the toxicity and potential risks associated with the vast number of NPs entering the environment and human bodies, so the performance of toxicological studies are highly demanded. While traditional assays focus primarily on the effects, the comprehension of the underlying processes requires innovative analytical approaches that can detect, characterize, and quantify NPs in complex biological matrices. Among the available alternatives to achieve this information, mass spectrometry, and more concretely, inductively coupled plasma mass spectrometry (ICP-MS), has emerged as an appealing option. This work critically reviews the valuable contribution of ICP-MS-based techniques to investigate NP toxicity and their transformations during in vitro and in vivo toxicological assays. Various ICP-MS modalities, such as total elemental analysis, single particle or single-cell modes, and coupling with separation techniques, as well as the potential of laser ablation as a spatially resolved sample introduction approach, are explored and discussed. Moreover, this review addresses limitations, novel trends, and perspectives in the field of nanotoxicology, particularly concerning NP internalization and pathways. These processes encompass cellular uptake and quantification, localization, translocation to other cell compartments, and biological transformations. By leveraging the capabilities of ICP-MS, researchers can gain deeper insights into the behaviour and effects of NPs, which can pave the way for safer and more responsible use of these materials.

Nanosafety: a Perspective on Nano-Bio Interactions

Engineered nanomaterials offer numerous benefits to society ranging from environmental remediation to biomedical applications such as drug or vaccine delivery as well as clean and cost-effective energy production and storage, and the promise of a more sustainable way of life. However, as nanomaterials of increasing sophistication enter the market, close attention to potential adverse effects on human health and the environment is needed. Here a critical perspective on nanotoxicological research is provided; the authors argue that it is time to leverage the knowledge regarding the biological interactions of nanomaterials to achieve a more comprehensive understanding of the human health and environmental impacts of these materials. Moreover, it is posited that nanomaterials behave like biological entities and that they should be regulated as such.

Macronutrient and PFOS bioavailability manipulated by aeration-driven rhizospheric organic nanocapsular assembly

Ubiquitous presence of the extremely persistent pollutants, per- and polyfluoroalkyl substances, is drawing ever-increasing concerns for their high eco-environmental risks which, however, are insufficiently considered based on the assembly characteristics of those amphiphilic molecules in environment. This study investigated the re-organization and self-assembly of perfluorooctane sulfonate (PFOS) and macronutrient molecules from rhizospheric organic (RhO) matter induced with a common operation of aeration. Atomic force microscopy (AFM) with infrared spectroscopy (IR)-mapping clearly showed that, after aeration and stabilization, RhO nanocapsules (∼ 1000 nm or smaller) with a core of PFOS-protein complexes coated by "lipid-carbohydrate" layers were observed whereas the capsule structure with a lipid core surrounded by "protein-carbohydrate-protein" multilayers was obtained in the absence of PFOS. It is aeration that exerted the disassociation of pristine RhO components, after which the environmental concentration PFOS restructured the self-assembly structure in a conspicuous "disorder-to-order" transition. AFM IR-mapping analysis of faeces combined with quantification of component uptake denoted the decreased ingestion and utilization of both PFOS and proteins compared with lipids and carbohydrates when Daphnia magna were fed with RhO nanocapsules. RhO nanocapsules acted as double-edged swords via simultaneously impeding the bioaccessibility of hazardous PFOS molecules and macronutrient proteins; and the latter might be more significant, which caused a malnutrition status within merely 48 h. Elucidating the assembly structure of natural organic matter and environmental concentration PFOS, the finding of this work could be a crucial supplementation to the high-dose-dependent eco-effect investigations on PFOS.

Toxic effects and action mechanism of metal-organic framework UiO-66-NH2 in Microcystisaeruginosa

The zirconium metal-organic framework UiO-66-NH2 has garnered considerable attention for their potentials of removing environmental contaminants from water. The production and application of UiO-66-NH2 make their releases into the aquatic environment inevitable. Nevertheless, little information is available regarding its potential risk to the environment and aquatic organisms, thus limiting the evaluation of its safe and sustainable use. In this study, the ecotoxicity of UiO-66-NH2 was evaluated, specifically its impacts on growth, extracellular organic matter release, and metabolomic changes of the model phytoplankton Microcystis aeruginosa (M. aeruginosa). UiO-66-NH2 exhibited moderate effects on algal physiology including growth, viability, and photosynthetic system. At concentrations below 20 mg/L, UiO-66-NH2 induced negligible inhibition of algal growth, algal viability, and photosynthesis. In contrast, UiO-66-NH2 boosted the release of extracellular organic matter even at concentration as low as 0.02 mg/L. These findings indicated that, while no evident damage to algal cells was observed, UiO-66-NH2 was hazardous to the aquatic environment as it stimulated the release of algal toxins. Moreover, UiO-66-NH2 entered algal cells rather than adhering to the surface of M. aeruginosa as observed by the fluorescence imaging. Based on metabolic analysis, UiO-66-NH2 influenced the cyanobacteria mainly through interference with purine metabolism and ABC transporter. This study sheds light on the potential threat UiO-66-NH2 posing to microalgae, and has potential implications for its safe utilization in the environmental field.

Infiltration of freshwater food chain by nanoplastics: An examination of trophic transfer and biological impact

The contamination of freshwater by nanoplastics (NPs) poses a significant threat to various organisms. However, the influence of food factors on the NPs toxicity and the associated risks to water safety remains poorly understood. In this study, we employed highly fluorescent NPs incorporating aggregation-induced emission fluorogens to quantify and visualize the interactions of NPs with freshwater phytoplanktonic alga Chlamydomonas reinhardtii and zooplankton Daphnia magna, including the uptake of NPs by algae and daphnids, as well as gut environment responses through both waterborne and foodborne routes. NPs at environmentally relevant concentrations were capable of aggregating and internalizing in planktonic algae, thus permeating the food chain and potentially causing ecological risks. Notably, positively charged NPs exhibited greater infiltration than the negatively charged NPs. Our findings indicated that NPs had a greater tendency to accumulate in Daphnia via the food chain rather than through direct exposure to water. This was attributed to the loss of selectivity, suggesting a potential mechanism for NP accumulation in aquatic food chains. However, daphnids exposed to NPs through waterborne route exhibited more gut pH acidification, esterase activity, and gut inflammation compared to those exposed via the foodborne route. Moreover, chronic exposure to NPs through waterborne routes significantly disrupted the growth, molting, and reproduction of Daphnia compared to the foodborne group. These findings provided valuable insights into the complexities of plastic pollution on primary trophic levels in aquatic environments.

Exposure protocol for ecotoxicity testing of microplastics and nanoplastics

Despite the increasing concern about the harmful effects of micro- and nanoplastics (MNPs), there are no harmonized guidelines or protocols yet available for MNP ecotoxicity testing. Current ecotoxicity studies often use commercial spherical particles as models for MNPs, but in nature, MNPs occur in variable shapes, sizes and chemical compositions. Moreover, protocols developed for chemicals that dissolve or form stable dispersions are currently used for assessing the ecotoxicity of MNPs. Plastic particles, however, do not dissolve and also show dynamic behavior in the exposure medium, depending on, for example, MNP physicochemical properties and the medium's conditions such as pH and ionic strength. Here we describe an exposure protocol that considers the particle-specific properties of MNPs and their dynamic behavior in exposure systems. Procedure 1 describes the top-down production of more realistic MNPs as representative of MNPs in nature and particle characterization (e.g., using thermal extraction desorption-gas chromatography/mass spectrometry). Then, we describe exposure system development for short- and long-term toxicity tests for soil (Procedure 2) and aquatic (Procedure 3) organisms. Procedures 2 and 3 explain how to modify existing ecotoxicity guidelines for chemicals to target testing MNPs in selected exposure systems. We show some examples that were used to develop the protocol to test, for example, MNP toxicity in marine rotifers, freshwater mussels, daphnids and earthworms. The present protocol takes between 24 h and 2 months, depending on the test of interest and can be applied by students, academics, environmental risk assessors and industries.

Effect of Exposure Concentration and Growth Conditions on the Association of Cerium Oxide Nanoparticles with Green Algae

The increasing release of engineered nanoparticles (NPs) into aquatic ecosystems makes it crucial to understand the interactions of NPs with aquatic organisms, such as algae. In this study, the association of CeO2 NPs with unicellular algae (Raphidocelis subcapitata) and changes to the cellular elemental profile were investigated using three exposure concentrations (1, 50, and 1000 µg CeO2/L) at two different algal growth conditions-exponential and inhibited growth (1% glutaraldehyde). After a 24 h-exposure, algal suspensions were settled by gravity and CeO2-NP/algae association was analyzed by single-cell inductively coupled plasma quadrupole mass spectrometry (sc-ICP-QMS) and ICP time-of-flight MS (sc-ICP-TOFMS). Concurrent detection of the cellular fingerprint with cerium indicated NP association with algae (adsorption/uptake) and changes in the cellular elemental profiles. Less than 5% of cells were associated with NPs when exposed to 1 µg/L. For 50 µg/L exposures in growing and inhibited cell treatments, 4% and 16% of cells were associated with CeO2 NPs, respectively. ICP-TOFMS analysis made it possible to exclude cellular exudates associated with CeO2 NPs due to the cellular fingerprint. Growing and inhibited cells had different elemental profile changes following exposure to CeO2 NPs-e.g., growing cells had higher Mg and lower P contents independent of CeO2 concentration compared to inhibited cells.

Transfer of CeO2 nanoparticles between freshwater omnivorous organisms: Effect of feces and necrophagy

Transfer of CeO₂ engineered nanoparticles (NPs) through feces was investigated between two omnivorous organisms, red crucian carp (Carassius auratus red var.) and crayfish (Procambarus clarkii). Upon water exposure (5 mg/L, 7 days), the highest bioaccumulation was observed in carp gills (5.95 μg Ce/g D.W.) and crayfish hepatopancreas (648 μg Ce/g D.W.), with the bioconcentration factors (BCFs) at 0.45 and 3.61, respectively. In addition, 97.4% and 73.0% of ingested Ce were excreted by carp and crayfish, respectively. The feces of carp and crayfish were collected and fed to crayfish and carp, respectively. After feces exposure, bioconcentration was observed in both carp (BCF, 3.00) and crayfish (BCF, 4.56). After feeding crayfish with carp bodies (1.85 μg Ce/g D.W.), CeO₂ NPs were not biomagnified (biomagnification factor, 0.28). Upon water exposure, CeO₂ NPs were transformed into Ce(III) in the feces of both carp (24.6%) and crayfish (13.6%), and the transformation was stronger after subsequent feces exposure (100% and 73.7%, respectively). Feces exposure lowered histopathological damage, oxidative stress, and nutritional quality (e.g., crude proteins, microelements, amino acids) to carp and crayfish in comparison with water exposure. This research highlights the importance of feces exposure on the transfer and fate of NPs in aquatic ecosystems.

Trophic transfer of silver nanoparticles shifts metabolism in snails and reduces food safety

Food security and sustainable development of agriculture has been a key challenge for decades. To support this, nanotechnology in the agricultural sectors increases productivity and food security, while leaving complex environmental negative impacts including pollution of the human food chains by nanoparticles. Here we model the effects of silver nanoparticles (Ag-NPs) in a food chain consisting of soil-grown lettuce Lactuca sativa and snail Achatina fulica. Soil-grown lettuce were exposed to sulfurized Ag-NPs via root or metallic Ag-NPs via leaves before fed to snails. We discover an important biomagnification of silver in snails sourced from plant root uptake, with trophic transfer factors of 2.0-5.9 in soft tissues. NPs shifts from original size (55-68 nm) toward much smaller size (17-26 nm) in snails. Trophic transfer of Ag-NPs reprograms the global metabolic profile by down-regulating or up-regulating metabolites for up to 0.25- or 4.20- fold, respectively, relative to the control. These metabolites control osmoregulation, phospholipid, energy, and amino acid metabolism in snails, reflecting molecular pathways of biomagnification and pontential adverse biological effects on lower trophic levels. Consumption of these Ag-NP contaminated snails causes non-carcinogenic effects on human health. Global public health risks decrease by 72% under foliar Ag-NP application in agriculture or through a reduction in the consumption of snails sourced from root application. The latter strategy is at the expense of domestic economic losses in food security of $177.3 and $58.3 million annually for countries such as Nigeria and Cameroon. Foliar Ag-NP application in nano-agriculture has lower hazard quotient risks on public health than root application to ensure global food safety, as brought forward by the United Nations Sustainable Development Goals.

Toxicokinetics and Particle Number-Based Trophic Transfer of a Metallic Nanoparticle Mixture in a Terrestrial Food Chain

Herein, we investigated to which extent metallic nanoparticles (MNPs) affect the trophic transfer of other coexisting MNPs from lettuce to terrestrial snails and the associated tissue-specific distribution using toxicokinetic (TK) modeling and single-particle inductively coupled plasma mass spectrometry. During a period of 22 days, snails were fed with lettuce leaves that were root exposed to AgNO3 (0.05 mg/L), AgNPs (0.75 mg/L), TiO2NPs (200 mg/L), and a mixture of AgNPs and TiO2NPs (equivalent doses as for single NPs). The uptake rate constants (ku) were 0.08 and 0.11 kg leaves/kg snail/d for Ag and 1.63 and 1.79 kg leaves/kg snail/d for Ti in snails fed with NPs single- and mixture-exposed lettuce, respectively. The elimination rate constants (ke) of Ag in snails exposed to single AgNPs and mixed AgNPs were comparable to the corresponding ku, while the ke for Ti were lower than the corresponding ku. As a result, single TiO2NP treatments as well as exposure to mixtures containing TiO2NPs induced significant biomagnification from lettuce to snails with kinetic trophic transfer factors (TTFk) of 7.99 and 6.46. The TTFk of Ag in the single AgNPs treatment (1.15 kg leaves/kg snail) was significantly greater than the TTFk in the mixture treatment (0.85 kg leaves/kg snail), while the fraction of Ag remaining in the body of snails after AgNPs exposure (36%) was lower than the Ag fraction remaining after mixture exposure (50%). These results indicated that the presence of TiO2NPs inhibited the trophic transfer of AgNPs from lettuce to snails but enhanced the retention of AgNPs in snails. Biomagnification of AgNPs from lettuce to snails was observed in an AgNPs single treatment using AgNPs number as the dose metric, which was reflected by the particle number-based TTFs of AgNPs in snails (1.67, i.e., higher than 1). The size distribution of AgNPs was shifted across the lettuce-snail food chain. By making use of particle-specific measurements and fitting TK processes, this research provides important implications for potential risks associated with the trophic transfer of MNP mixtures.

Investigating the Cellular Uptake of Model Nanoplastics by Single-Cell ICP-MS

A synthetic route to producing gold-doped environmentally relevant nanoplastics and a method for the rapid and high-throughput qualitative investigation of their cellular interactions have been developed. Polyethylene (PE) and polyvinyl chloride (PVC) nanoparticles, doped with ultrasmall gold nanoparticles, were synthesized via an oil-in-water emulsion technique as models for floating and sedimenting nanoplastics, respectively. Gold nanoparticles were chosen as a dopant as they are considered to be chemically stable, relatively easy to obtain, interference-free for elemental analysis, and suitable for bio-applications. The suitability of the doped particles for quick detection via inductively coupled plasma mass spectrometry (ICP-MS), operating in single-cell mode (scICP-MS), was demonstrated. Specifically, the method was applied to the analysis of nanoplastics in sizes ranging from 50 to 350 nm, taking advantage of the low limit of detection of single-cell ICP-MS for gold nanoparticles. As an initial proof of concept, gold-doped PVC and PE nanoplastics were employed to quantify the interaction and uptake of nanoplastics by the RAW 264.7 mouse macrophage cell line, using scICP-MS and electron microscopy. Macrophages were chosen because their natural biological functions would make them likely to internalize nanoplastics and, thus, would produce samples to verify the test methodology. Finally, the method was applied to assess the uptake by CaCo-2 human intestinal cells, this being a more relevant model for humanexposure to those nanoplastics that are potentially available in the food chain. For both case studies, two concentrations of nanoplastics were employed to simulate both standard environmental conditions and exceptional circumstances, such as pollution hotspot areas.

Insights into eco-corona formation and its role in the biological effects of nanomaterials from a molecular mechanisms perspective

Broad application of nanotechnology inevitably results in the release of nanomaterials (NMs) into the aquatic environment, and the negative effects of NMs on aquatic organisms have received much attention. Notably, in the natural aquatic environment, ubiquitous ecological macromolecules (i.e., natural organic matter, extracellular polymeric substances, proteins, and metabolites) can easily adsorb onto the surfaces of NMs and form an "eco-corona". As most NMs have such an eco-corona modification, the properties of their eco-corona significantly determine the fate and ecotoxicity of NMs in the natural aquatic ecosystem. Therefore, it is of great importance to understand the role of the eco-corona to evaluate the environmental risks NMs pose. However, studies on the mechanism of eco-corona formation and its resulting nanotoxicity on aquatic organisms, especially at molecular levels, are rare. This review systemically summarizes the mechanisms of eco-corona formation by several typical ecological macromolecules. In addition, the similarities and differences in nanotoxicity between pristine and corona-coated NMs to aquatic organisms at different trophic levels were compared. Finally, recent findings about potential mechanisms on how NM coronas act on aquatic organisms are discussed, including cellular internalization, oxidative stress, and genotoxicity. The literature shows that 1) the formation of an eco-corona on NMs and its biological effect highly depend on both the composition and conformation of macromolecules; 2) both feeding behavior and body size of aquatic organisms at different trophic levels result in different responses to corona-coated NMs; 3) genotoxicity can be used as a promising biological endpoint for evaluating the role of eco-coronas in natural waters. This review provides informative insight for a better understanding of the role of eco-corona plays in the nanotoxicity of NMs to aquatic organisms which will aid the safe use of NMs.

Internalization of the Metal-Organic Framework MIL-101(Cr)-NH2 by a Freshwater Alga and Transfer to Zooplankton

The common metal-organic framework (MOF) MIL-101(Cr)-NH₂ has attracted considerable attention due to its great potential applications in the environmental field. Nevertheless, its behavior and fate in aquatic systems are unknown. This study quantified and visualized the interactions of MIL-101(Cr)-NH₂ with the freshwater phytoplanktonic alga Chlamydomonas reinhardtii and its potential trophic transfer to zooplankton. The unicellular alga absorbed and accumulated the MOF by surface attachment, forming agglomerates and eventually cosettling out from water. Bioimaging revealed that MIL-101(Cr)-NH₂ was internalized by the algal cells and mainly occurred in the pyrenoid. Without algae in a freshwater system, MIL-101(Cr)-NH₂ was ingested by Daphnia magna, showing steadily increasing concentrations approaching 1-9% of dry body weight. Addition of algae substantially suppressed D. magna uptake of MIL-101(Cr)-NH₂ by 63.8-97.9%. Such inhibition could be explained by the competitive uptake of MOF by the algae and the inductive effects of algal food on MOF elimination by D. magna. The MOF (≤1 mg/L) ingested by D. magna was centered in the gut regions, whereas large MOF or algae-MOF aggregates were adsorbed onto the carapace and appendages, including the antennae, at 10 mg/L. Overall, the algae were the major targets for MIL-101(Cr)-NH₂, with nearly all algal cells settling out at 10 mg/L within 24 h. The possibility of trophic transfer of MIL-101(Cr)-NH₂ to D. magna in aquatic systems with algae present was limited due to its low accumulation potential and short retention time in D. magna.

Bioaccumulation of CuO nanomaterials in rainbow trout: Influence of exposure route and particle shape

The bioaccumulation potential of spherical and rod-shaped CuO nanomaterials (NMs) was assessed in rainbow trout (Oncorhynchus mykiss) exposed via water and diet following the OECD Test Guideline No. 305. Fish were exposed via diet to both NMs at concentrations of 70 and 500 mg Cu/kg for 15 days, followed by 44 days of depuration. For water-borne exposure, only the rod-shaped CuO NMs were tested at 0.08 and 0.8 mg Cu/L for 28 days, followed by 14 days of depuration. The concentration of Cu was determined in fish whole body to derive biomagnification and bioconcentration factors (BMF and BCF). Different tissues were sampled to investigate the total Cu biodistribution and target organs as well as the particle number-based bioaccumulation of CuO NMs. Estimated BMF and BCF values were below the thresholds of concern. However, shape and route influenced depuration. Following dietary exposure, there was a higher depuration of Cu from fish exposed to the rod-shaped compared to the spherical CuO NMs. A higher depuration was also observed for rod-shaped CuO NMs following the dietary exposure compared the aqueous one. Despite the much higher dietary exposure concentrations of rod-shape CuO NMs, similar Cu body burdens were reached via water. Cu was found in particulate form in different tissues. Although these NMs had a low bioaccumulation potential, differences in distribution and elimination patterns of Cu were observed depending on the exposure route and particle shape. Careful consideration of the most relevant exposure route is needed when designing a bioaccumulation experiment for testing NMs.

Removal of emerging pollutants from the environment: From bioadsorbents to nanoparticle-based systems

In the Call for Papers corresponding to this Virtual Special Issue (VSI), the Editors indicated that, as is well known, emerging pollutants include a variety of substances that pose remarkable risks for the environment and public health. In fact, emerging pollutants are considered a matter of concern deserving increasing efforts to elucidate their occurrence, fate, repercussions, and alternatives to their removal from the various environmental compartments where they can be found after spreading as contaminants. Also, the Editors commented that, among the various alternatives that can be considered for achieving their successful removal, some of them are based on the use of sorbent materials, and, specifically, bioadsorbents, which are attractive due to the efficacy and low cost associated with some of them. Another alternative is related to the utilization of nanoparticle-based systems, which may be considered a promising field of research in this way. In both cases, obtaining new research results, as well as designing and programming new ways of going steps ahead in the investigation of both kinds of materials, would be key objectives. According to the previous considerations, the Editors of the VSI invited researchers having new data concerning these aspects to submit manuscripts with experimental results, discussion, reflections and prospective related to their work. With the Special Issue closed, the number of submissions received was 83, with 40 high-quality works being accepted for publication, increasing the overall knowledge on this topic by providing results that we are sure will be of value for the scientific community and the society.

Environmental Implications Associated with the Development of Nanotechnology: From Synthesis to Disposal

Nanotechnology remains under continuous development. The unique, fascinating, and tunable properties of nanomaterials make them interesting for diverse applications in different fields such as medicine, agriculture, and remediation. However, knowledge about the risks associated with nanomaterials is still poorly known and presents variable results. Furthermore, the interaction of nanomaterials with biological systems and the environment still needs to be clarified. Moreover, some issues such as toxicity, bioaccumulation, and physicochemical transformations are found to be dependent on several factors such as size, capping agent, and shape, making the comparisons even more complex. This review presents a comprehensive discussion about the consequences of the use and development of nanomaterials regarding their potential risks to the environment as well as human and animal health. For this purpose, we reviewed the entire production chain from manufacturing, product development, applications, and even product disposal to raise the important implications at each stage. In addition, we present the recent developments in terms of risk management and the recycling of nanomaterials. Furthermore, the advances and limitations in the legislation and characterization of nanomaterials are also discussed.

Submicron Plastic Adsorption by Peat, Accumulation in Sphagnum Mosses and Influence on Bacterial Communities in Peatland Ecosystems

The smallest fraction of plastic pollution, submicron plastics (SMPs <1 μm) are expected to be ubiquitous in the environment. No information is available about SMPs in peatlands, which have a key role in sequestering carbon in terrestrial ecosystems. It is unknown how these plastic particles might behave and interact with (micro)organisms in these ecosystems. Here, we show that the chemical composition of polystyrene (PS) and poly(vinyl chloride) (PVC)-SMPs influenced their adsorption to peat. Consequently, this influenced the accumualtion of SMPs by Sphagnum moss and the composition and diversity of the microbial communities in peatland. Natural organic matter (NOM), which adsorbs from the surrounding water to the surface of SMPs, decreased the adsorption of the particles to peat and their accumulation by Sphagnum moss. However, the presence of NOM on SMPs significantly altered the bacterial community structure compared to SMPs without NOM. Our findings show that peatland ecosystems can potentially adsorb plastic particles. This can not only impact mosses themselves but also change the local microbial communities.

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.

Extraction and Quantification of Nanoparticulate Mercury in Natural Soils

Nanoparticulate mercury (Hg-NPs) are ubiquitous in nature. However, the lack of data on their concentration in soils impedes reliable risk assessments. This is due to the analytical difficulties resulting from low ambient Hg concentrations and background interferences of heterogeneous soil components. Here, coupled to single particle inductively coupled plasma-mass spectrometry (spICP-MS), a standardized protocol was developed for extraction and quantification of Hg-NPs in natural soils with a wide range of properties. High particle number-, particle mass-, and total mass-based recoveries were obtained for spiked HgS-NPs (74-120%). Indigenous Hg-NPs across soils were within 10⁷-10¹¹ NPs g^-1, corresponding to 3-40% of total Hg on a mass basis. Metacinnabar was the primary Hg species in extracted samples from the Wanshan mercury mining site, as characterized by X-ray absorption spectroscopy and transmission electron microscopy. In agreement with the spICP-MS analysis, electron microscopy revealed comparable size distribution for nanoparticles larger than 27 nm. These indigenous Hg-NPs contributed to 5-65% of the measured methylmercury in soils. This work paves the way for experimental determinations of indigenous Hg-NPs in natural soils, which is critical to understand the biogeochemical cycling of mercury and thereby the methylation processes governing the public exposure to methylmercury.

Occurrence of Silver-containing Particles in Rat Brains upon Intranasal Exposure of Silver Nanoparticles

The widespread application of silver nanomaterials raises health concerns due to the adverse effects that can be associated with silver nanoparticles (AgNPs) exposure. AgNPs can be introduced into human bodies via inhalation, either intentionally (intranasal administration of AgNPs) or unintentionally (environmental pollution, accidental release, or occupational exposure). Recent studies have shown that intranasal exposure of experimental animals to AgNPs can lead to the accumulation of silver (Ag) in brain tissues. However, there is little information available concerning what forms of Ag (particulate and ionic) exist in brain tissues. This study aimed to investigate whether particulate Ag exists in rat brains following intranasal exposure of AgNPs at 1 mg/kg/day using multiple analytical techniques. The results demonstrated that Ag-containing particles were presented in AgNPs-exposed rat brains, accounting for 20.2%- 68.1% of the total Ag. The mass concentrations of Ag-containing particles in brain tissues increased with exposure time but only decreased by 37.5% after elimination for 4 weeks upon exposure cessation. The size of Ag-containing particles identified in rat brains was larger than the original AgNPs. The Ag-containing particles identified in the rat brain were composed of multiple elements, including Ag, sulfur (S), selenium (Se) with atomic percentages of 45.8%, 37.5%, 16.7% respectively. The finding highlighted the occurrence and accumulation of transformed AgNPs containing S and Se in rat brains after intranasal exposure to AgNPs, implying potential risks for brain health.

Chemical composition and particle size influence the toxicity of nanoscale plastic debris and their co-occurring benzo(α)pyrene in the model aquatic organisms Daphnia magna and Danio rerio

Little is known about how particle chemical composition and size might influence the toxicity of nanoscale plastic debris (NPD) and their co-occurring chemicals. Herein, we investigate the toxicity of 3 × 10¹⁰ particles/L polyethylene (PE, 50 nm), polypropylene (PP, 50 nm), polystyrene (PS, 200 and 600 nm), and polyvinyl chloride (PVC, 200 nm) NPD and their co-occurring benzo(a)pyrene (BaP) to Daphnia magna and Danio rerio. During the 21 days of exposure to PE 50 nm and PS 200 nm, the number of broods produced by D. magna decreased compared to other treatments. Exposure to BaP alone did not produce any effects on the reproduction of the daphnids, however, the mixture of BaP with PS (200 or 600 nm) or with PE (50 nm) reduced the number of broods. Exposure of D. rerio embryos to PE 50 nm, PS 200 nm, and PS 600 nm led to a delay in the hatching. The presence of PS 200 nm and PVC 200 nm eliminated the effects of BaP on the hatching rate of zebrafish. Our findings suggest that data generated for the toxicity of one type of NPD, e.g. PVC or PS may not be extrapolated to other types of NPD.