Impact of multi-walled carbon nanotubes on aquatic species

Escaping the ESKAPE pathogens: A review on antibiofilm potential of nanoparticles

ESKAPE pathogens, a notorious consortium comprising Enterococcusfaecium, Staphylococcusaureus, Klebsiellapneumoniae, Acinetobacterbaumannii, Pseudomonasaeruginosa, and Enterobacter species, pose formidable challenges in healthcare settings due to their multidrug-resistant nature. The increasing global cases of antimicrobial-resistant ESKAPE pathogens are closely related to their remarkable ability to form biofilms. Thus, understanding the unique mechanisms of antimicrobial resistance of ESKAPE pathogens and the innate resilience of biofilms against traditional antimicrobial agents is important for developing innovative strategies to establish effective control methods against them. This review offers a thorough analysis of biofilm dynamics, with a focus on the general mechanisms of biofilm formation, the significant contribution of persister cells in the resistance mechanisms, and the recurrence of biofilms in comparison to planktonic cells. Additionally, this review highlights the potential strategies of nanoparticles for managing biofilms in the ESKAPE group of pathogens. Nanoparticles, with their unique physicochemical properties, provide promising opportunities for disrupting biofilm structures and improving antimicrobial effectiveness. The review has explored interactions between nanoparticles and biofilms, covering a range of nanoparticle types such as metal, metal-oxide, surface-modified, and functionalized nanoparticles, along with organic nanoparticles and nanomaterials. The additional focus of this review also encompasses green synthesis techniques of nanoparticles that involve plant extract and supernatants from bacterial and fungal cultures as reducing agents. Furthermore, the use of nanocomposites and nano emulsions in biofilm management of ESKAPE is also discussed. To conclude, the review addresses the current obstacles and future outlooks in nanoparticle-based biofilm management, stressing the necessity for further research and development to fully exploit the potential of nanoparticles in addressing biofilm-related challenges.

Assessments of carbon nanotubes toxicities in zebrafish larvae using multiple physiological and molecular endpoints

In recent years, carbon nanotubes (CNTs) have become one of the most promising materials for the technology industry. However, due to the extensive usage of these materials, they may be released into the environment, and cause toxicities to the organism. Here, their acute toxicities in zebrafish embryos and larvae were evaluated by using various assessments that may provide us with a novel perspective on their effects on aquatic animals. Before conducting the toxicity assessments, the CNTs were characterized as multiwall carbon nanotubes (MWCNTs) functionalized with hydroxyl and carboxyl groups, which improved their solubility and dispersibility. Based on the results, abnormalities in zebrafish behaviors were observed in the exposed groups, indicated by a reduction in tail coiling frequency and alterations in the locomotion as the response toward photo and vibration stimuli that might be due to the disruption in the neuromodulatory system and the formation of reactive oxygen species (ROS) by MWCNTs. Next, based on the respiratory rate assay, exposed larvae consumed more oxygen, which may be due to the injuries in the larval gill by the MWCNTs. Finally, even though no irregularity was observed in the exposed larval cardiac rhythm, abnormalities were shown in their cardiac physiology and blood flow with significant downregulation in several cardiac development-related gene expressions. To sum up, although the following studies are necessary to understand the exact mechanism of their toxicity, the current study demonstrated the environmental implications of MWCNTs in particularly low concentrations and short-term exposure, especially to aquatic organisms.

Tissue distribution, placental transfer and excretion of silver nanoparticles in pregnant rats after a single oral dose

A quantitative assessment of silver nanoparticles (AgNPs) in fluids and some organs of pregnant rats as well as their fetal blood were carried out in this study. A single oral dose (1mg/kg) of AgNPs with a size range of 4-20 nm was administered to pregnant rats on the 19th of gestation. Five groups were euthanized after 10 min, 1, 6, 12, and 24 hr as well as the control group. Total Silver (Ag) contents were measured in bloods (maternal and fetal) and several organs using Inductive Coupled Plasma Optical Emission Spectroscopy (ICP-OES) followed by acid digestion. In maternal blood, AgNPs were found to increase time-dependently after 12 and 24 hr into 0.135 and 0.224 μg/ml, but it was slightly higher in fetal blood (0.32 and 0.31 μg/ml) after 10 min and 1 hr. In other samples: kidneys, liver, spleen, placenta, and uterus the data indicated that NPs were rapidly absorbed from the dosing site (gastrointestinal tract) as evidenced by the detection of Ag in the analyzed samples (fluids and tissues). On the other hand, the cumulative percentages of excretion level in urine was 8.25% which was higher than in feces (4.77%) after 24 hr. These findings indicate the ability of AgNPs to accumulate in pregnant rats and transfer to their fetus imposing adverse outcomes and male formation. Thus, further investigations must be followed for direct and/or indirect exposure to such NPs before decision for their practices.

A cohesive effort to assess the suitability and disparity of carbon nanotubes for water treatment

Population growth, industrialization, and the extensive use of chemicals in daily life have all contributed to an increase in waste generation and an intensified release of organic pollutants into the aquatic environment. To ensure the quality of water (including natural resources), the removal of these pollutants from wastewater has become a challenging task for scientific community. Conventional physical, chemical, and biological treatment methods are commonly used in combinations and are not very effective. Recently, carbon nanotubes (CNTs) emerged as the most reliable and adaptable choice for efficient water treatment due to their extraordinary material properties appearing as a single-step solution for water treatment. High surface area, exceptional porosities, hollow and layered structures, and ease of chemical activation and functionalization are some properties which makes it excellent adsorption material. Hence, this review paper discusses the recent advances in the synthesis, purification, and functionalization of CNTs for water and wastewater treatment. In addition, this study also also provides a quick overview of CNTs-based advance technologies employed in water treatment and carefully assesses the benefits versus risks during large-scale water treatment. Furthermore, it concludes that identified risks to the environment and human health cannot be easily ignored and strict regulatory requirements are a must for producing low-cost innoxious CNTs.

In situ boron-doped cellulose-based biochar for effective removal of neonicotinoids: Adsorption mechanism and safety evaluation

Biochar materials have been widely employed for adsorption of pollutants, which necessitates further consideration of their efficiency and safety in environmental remediation. In this study, a porous biochar (AC) was prepared through the combination of hydrothermal carbonization and in situ boron doping activation to effectively adsorb neonicotinoids. The adsorption process was shown to be a spontaneous endothermic physical adsorption process, where the predominant interaction forces between the acetamiprid and AC were electrostatic and hydrophobic interactions. The maximum adsorption capacity was 227.8 mg g^-1for acetamiprid and the safety of AC was verified by simulating the situation where the aquatic organism (D. magna) was exposed to the combined system (AC & neonicotinoids). Interestingly, AC was observed to reduce the acute toxicity of neonicotinoids owing to the reduced bioavailability of acetamiprid in D. magna and the newly generated expression of cytochrome p450. Thus, it enhanced the metabolism and detoxification response in D. magna, which reducing the biological toxicity of acetamiprid. This study not only demonstrates the potential application of AC from a safety perspective, but also provides insight into the combined toxicity caused by biochar after adsorption of pollutants at the genomic level, which fills the gap in related research.

A workflow to investigate the impacts of weathered multi-walled carbon nanotubes to the mud snail Lymnaea stagnalis

Although the development and application of nanomaterials is a growing industry, little data is available on the ecotoxicological effects on aquatic organisms. Therefore, we set up a workflow to address the potential uptake of weathered multi-walled carbon nanotubes (wMWCNTs) by a model organism, the pulmonary mud snail Lymnaea stagnalis (L. stagnalis), which plays an important role in the food web. It represents a suitable organism for this approach because as a grazer it potentially ingests large amounts of sedimented wMWCNTs. As food source for L. stagnalis, benthic biofilm was investigated by the use of a transmission electron microscope (TEM) and a scanning electron microscope (SEM) after exposure with wMWCNTs. In addition, isotopic labeling was applied with ¹⁴C-wMWCNTs (0.1 mg/L) to quantify fate, behavior, and enrichment of ¹⁴C-wMWCNTs in benthic biofilm and in L. stagnalis. Enrichment in benthic biofilm amounted to 529.0 µg wMWCNTs/g dry weight and in L. stagnalis to 79.6 µg wMWCNTs/g dry weight. A bioconcentration factor (BCF) for L. stagnalis was calculated (3500 L/kg). We demonstrate the accumulation of wMWCNTs (10 mg/L) in the digestive tract of L. stagnalis in an effect study. Moreover, the physiological markers glycogen and triglycerides as indicators for the physiological state, as well as the RNA/DNA ratio as growth indicator, were examined. No significant differences between exposed and control animals were analyzed for glycogen and triglycerides after 24 days of exposure, but a decreasing trend is recognizable for triglycerides. In contrast, the significant reduction in the RNA/DNA ratio of L. stagnalis indicated an inhibition of growth with a following recovery after depuration. The described workflow enables a comprehensive determination of the fate and the behavior of wMWCNTs specifically and in general all kinds of CNTs in the aquatic environment and therefore contributes to a holistic risk assessment of wMWCNTs.

Transgenic zebrafish larvae as a non-rodent alternative model to assess pro-inflammatory (neutrophil) responses to nanomaterials

Hazard studies for nanomaterials (NMs) commonly assess whether they activate an inflammatory response. Such assessments often rely on rodents, but alternative models are needed to support the implementation of the 3Rs principles. Zebrafish (Danio rerio) offer a viable alternative for screening NM toxicity by investigating inflammatory responses. Here, we used non-protected life stages of transgenic zebrafish (Tg(mpx:GFP)ⁱ¹¹⁴) with fluorescently-labeled neutrophils to assess inflammatory responses to silver (Ag) and zinc oxide (ZnO) NMs using two approaches. Zebrafish were exposed to NMs via water following a tail fin injury, or NMs were microinjected into the otic vesicle. Zebrafish were exposed to NMs at 3 days post-fertilization (dpf) and neutrophil accumulation at the injury or injection site was quantified at 0, 4, 6, 8, 24, and 48 h post-exposure. Zebrafish larvae were also exposed to fMLF, LTB₄, CXCL-8, C5a, and LPS to identify a suitable positive control for inflammation induction. Aqueous exposure to Ag and ZnO NMs stimulated an enhanced and sustained neutrophilic inflammatory response in injured zebrafish larvae, with a greater response observed for Ag NMs. Following microinjection, Ag NMs stimulated a time-dependent neutrophil accumulation in the otic vesicle which peaked at 48 h. LTB₄ was identified as a positive control for studies investigating inflammatory responses in injured zebrafish following aqueous exposure, and CXCL-8 for microinjection studies that assess responses in the otic vesicle. Our findings support the use of transgenic zebrafish to rapidly screen the pro-inflammatory effects of NMs, with potential for wider application in assessing chemical safety (e.g. pharmaceuticals).

Microcystis aeruginosa's exposure to an antagonism of nanoplastics and MWCNTs: The disorders in cellular and metabolic processes

Nanoplastics and carbon nanotubes (CNTs) is one of the emerging environmental contaminants and a widely used engineering nanomaterial, and their biological toxicity has been frequently studied. However, there has been no research on the combined exposure of these two totally different shape nanoparticles. To explore their potential threat to freshwater ecosystems, Microcystis aeruginosa (M. aeruginosa) was exposed to concentration gradients of polystyrene nanoplastics (Nano-PS) and multi-walled carbon nanotubes (MWCNTs). The physiological analysis and whole-transcriptome sequencing were integrated to certify the cytotoxicity. As the physiological results showed, the low concentration (5 mg/L) of these two nanoparticles showed a stimulation on the growth (6.49%-12.2%) and photosynthesis (0-7.6%), and the coexposure was slightly higher than individuals. However, other concentrations showed inhibitory effect, especially at high concentration (50 mg/L), and all physical signs and electron microscope images showed obvious cytotoxicity. Compared with the individuals, the coexposure showed an antagonistic effect induced by the heterogeneous agglomeration which decreased the surface toxicity and the contact with algae of nanomaterials. Transcriptome results showed that coexposure treatment had the fewest differential genes, and the primary effects embodied in the disturbances of cellular and metabolic processes which were superior to the individuals. In the 50 mg/L Nano-PS, the translation process was significantly disordered, and MWCNTs could disrupted the photosynthesis, multiple metabolism processes, membrane transport, and translation. These findings demonstrated the aquatic toxic mechanism from cellular and metabolic processes of Nano-PS and MWCNTs for M. aeruginosa and provided valuable data for environmental risk assessment of them.

Nanoparticles induced embryo-fetal toxicity

Applications of nanomaterials cause a general concern on their toxicity when they intentionally (such as in medicine) or unintentionally (environment exposure) enter into the human body. As a special subpopulation, pregnant women are more susceptible to nanoparticle (NP)-induced toxicity. More importantly, prenatal exposures may affect the entire life of the fetus. Through blood circulation, NPs may cross placental barriers and enter into fetus. A cascade of events, such as damage in placental barriers, generation of oxidative stress, inflammation, and altered gene expression, may induce delayed or abnormal fetal development. The physicochemical properties of NPs, exposure time, and other factors directly affect nanotoxicity in pregnant populations. Even though results from animal studies cannot directly extrapolate to humans, compelling evidence has already shown that, for pregnant women, caution must be taken when dealing with nanomedicines or NP pollutants.

Comparative developmental toxicity of iron oxide nanoparticles and ferric chloride to zebrafish (Danio rerio) after static and semi-static exposure

Iron oxide nanoparticles (IONPs) are used in several medical and environmental applications, but their mechanism of action and hazardous effects to early developmental stages of fish remain unknown. Thus, the present study aimed to assess the developmental toxicity of citrate-functionalized IONPs (γ-Fe₂O₃ NPs), in comparison with its dissolved counterpart, in zebrafish (Danio rerio) after static and semi-static exposure. Embryos were exposed to environmental concentrations of both iron forms (0.3, 0.6, 1.25, 2.5, 5 and 10 mg L^-1) during 144 h, jointly with negative control group. The interaction and distribution of both Fe forms on the external chorion and larvae surface were measured, following by multiple biomarker assessment (mortality, hatching rate, neurotoxicity, cardiotoxicity, morphological alterations and 12 morphometrics parameters). Results showed that IONPs were mainly accumulated on the zebrafish chorion, and in the digestive system and liver of the larvae. Although the IONPs induced low embryotoxicity compared to iron ions in both exposure conditions, these nanomaterials induced sublethal effects, mainly cardiotoxic effects (reduced heartbeat, blood accumulation in the heart and pericardial edema). The semi-static exposure to both iron forms induced high embryotoxicity compared to static exposure, indicating that the nanotoxicity to early developmental stages of fish depends on the exposure system. This is the first study concerning the role of the exposure condition on the developmental toxicity of IONPs on fish species.

Establishing structure-property-hazard relationships for multi-walled carbon nanotubes: the role of aggregation, surface charge, and oxidative stress on embryonic zebrafish mortality

Increasing use of carbon nanotubes (CNTs) in consumer and industrials goods increases their potential release, and subsequent risks to environmental and human health. Therefore, it is becoming ever more important that CNTs are designed to reduce or eliminate hazards and that hazard assessment methodologies are robust. Here, oxygen-functionalized multi-walled CNTs (O-MWCNTs), modified under varying redox conditions, were assessed for toxic potential using the zebrafish (Danio rerio) embryo model. Multiple physicochemical properties (e.g., MWCNT aggregate size, morphology, and rate; surface charge and oxygen concentration; and reactive oxygen species (ROS) generation) were characterized and related to zebrafish embryo mortality through the use of multivariate statistical methods. Of these properties, surface charge and aggregate morphology emerged as the greatest predictors of embryo mortality. Interestingly, ROS generation was not significantly correlated to observed mortality, contrary to prior predictions by nanotoxicology researchers. This suggests that the mechanism of MWCNT-induced mortality of embryonic zebrafish is physical, driven by electrostatic and shape effects, both of which are related to nanomaterial aggregation. This raises the importance of rigorously considering aggregation during aqueous-based nanotoxicology assays as nanomaterial aggregation can affect perceived nanomaterial toxicity. As such, future nanotoxicity studies relying on aqueous media must sufficiently consider nanomaterial aggregation.

The zebrafish embryotoxicity test (ZET) for nanotoxicity assessment: from morphological to molecular approach

Nanotechnology and use of nanomaterials (NMs) improve life quality, economic growth and environmental health. However, the increasing production and use of NMs in commercial products has led to concerns about their potential toxicity on human and environment health, as well as its toxicological classification and regulation. In this context, there is an urgent need to standardize and validate procedures for nanotoxicity testing. Since the zebrafish embryotoxicity test (ZET) has been indicated as a suitable approach for the toxicity assessment of traditional and emergent pollutants, the aim of this review is to summarize the existing literature on embryotoxic and teratogenic effects of NMs on zebrafish. In addition, morphological changes in zebrafish embryos induced by NMs were classified in four reaction models, allowing classification of the mode of action and toxicity of different types of NM. Revised data showed that the interaction and bioaccumulation of NMs on zebrafish embryos were associated to several toxic effects, while the detoxification process was limited. In general, NMs induced delayed hatching, circulatory changes, pigmentation and tegumentary alterations, musculoskeletal disorders and yolk sac alterations on zebrafish embryos. Recommendations for nanotoxicological tests are given, including guidance for future research. This review reinforces the use of the ZET as a suitable approach to assess the health risks of NM exposure.

Biological response and developmental toxicity of zebrafish embryo and larvae exposed to multi-walled carbon nanotubes with different dimension

The development and use of nanomaterials are increasing significantly. Among nanomaterials, carbon nanotubes are of particular interest due to its distinctive physicochemical properties. This material composed of sheets of graphite has very high thermal conductivity, metallic-type electrical conductivity, stiffness, toughness and unique ability to bond to itself in an extended network with extraordinary strength. Its application in the industry is continuously growing, which could lead to the accumulation in the environment and a consequent impact on both humans and ecosystems. Considering that environmental systems are dynamic, it is difficult to predict the risks associated with the release of nanomaterials to the environment. Bioindicators are useful tools as primary signals of environmental risk, and their responses reveal the organism and ecosystem health.

In the present study, we evaluated the impact of multi-walled carbon nanotubes with different dimensions and agglomeration pattern on zebrafish embryo and larvae; mainly, studies were focused on physiological and behavioral responses. In embryos, measurements were hatching rate, morphology changes, and viability. In larvae, locomotor activity, heart rate, innate inflammatory response, general and tissue-specific morphology were measured. MWCNT-S (short, wide and mostly dispersed) caused depression of the locomotor activity of larvae, indicating an alteration of the central nervous system, and depression of neutrophil migration activity. MWCNT-L (long, thin and agglomerated) caused malformations during larval development, a decrease of neutrophil migration and alteration of cardiac rhythm. Results obtained for both carbon nanotubes were different, highlighting the importance of dimensions of the same nanomaterial, and also the kind of agglomeration and shape adopted, for the toxic effects on organisms.

Let's get small (and smaller): Combining zebrafish and nanomedicine to advance neuroregenerative therapeutics

Several key attributes of zebrafish make them an ideal model system for the discovery and development of regeneration promoting therapeutics; most notably their robust capacity for self-repair which extends to the central nervous system. Further, by enabling large-scale drug discovery directly in living vertebrate disease models, zebrafish circumvent critical bottlenecks which have driven drug development costs up. This review summarizes currently available zebrafish phenotypic screening platforms, HTS-ready neurodegenerative disease modeling strategies, zebrafish small molecule screens which have succeeded in identifying regeneration promoting compounds and explores how intravital imaging in zebrafish can facilitate comprehensive analysis of nanocarrier biodistribution and pharmacokinetics. Finally, we discuss the benefits and challenges attending the combination of zebrafish and nanoparticle-based drug optimization, highlighting inspiring proof-of-concept studies and looking toward implementation across the drug development community.

Relation between biophysical properties of nanostructures and their toxicity on zebrafish

In recent years, the use of commercial nanoparticles in different industry and health fields has increased exponentially. However, the uncontrolled application of nanoparticles might present a potential risk to the environment and health. Toxicity of these nanoparticles is usually evaluated by a fast screening assay in zebrafish (Danio rerio). The use of this vertebrate animal model has grown due to its small size, great adaptability, high fertilization rate and fast external development of transparent embryos. In this review, we describe the toxicity of different micro- and nanoparticles (carbon nanotubes, dendrimers, emulsions, liposomes, metal nanoparticles, and solid lipid nanoparticles) associated to their biophysical properties using this model. The main biophysical properties studied are size, charge and surface potential due to their impact on the environment and health effects. The review also discusses the correlation of the effects of the different nanoparticles on zebrafish. Special focus is made on morphological abnormalities, altered development and abnormal behavior. The last part of the review debates changes that should be made in future directions in order to improve the use of the zebrafish model to assess nanotoxicity.

Toxicity Evaluation of New Engineered Nanomaterials in Zebrafish

The effect of the nanoparticles on the marine organisms, depends on their size, chemical composition, surface structure, solubility and shape. In order to take advantage from their activity, preserving the surrounding environment from a possible pollution, we are trying to trap the nanoparticles into new nanomaterials. The nanomaterials tested were synthesized proposing a ground-breaking approach by an upside-down vision of the Au/TiO2 nano-system to avoid the release of nanoparticles. The system was synthesized by wrapping Au nanoparticles with a thin layer of TiO2. The non-toxicity of the nano-system was established by testing the effect of the material on zebrafish larvae. Danio rerio o zebrafish was considered an excellent model for the environmental biomonitoring of aquatic environments and the Zebrafish Embryo Toxicity Test (ZFET) is considered an alternative method of animal test. For this reason zebrafish larvae were exposed to different concentrations of nanoparticles of TiO2 and Au and new nanomaterials. As biomarkers of exposure, we evaluated the expression of metallothioneins by immunohistochemistry analysis and western blotting analysis also. The results obtained by toxicity test showed that neither mortality as well as sublethal effects were induced by the different nanomaterials and nanoparticles tested. Only zebrafish larvae exposed to free Au nanoparticles showed a different response to anti-MT antibody. In fact, the immunolocalization analysis highlighted an increase of the metallothioneins synthesis.

Effects of multi-walled carbon nanotube (MWCNT) on antioxidant depletion, the ERK signaling pathway, and copper bioavailability in the copepod (Tigriopus japonicus)

Multi-walled carbon nanotubes (MWCNTs) are nanoparticles widely applicable in various industrial fields. However, despite the usefulness of MWCNTs in industry, their oxidative stress-induced toxicity, combined toxicity with metal, and mitogen-activated protein kinase (MAPK) activation have not been widely investigated in marine organisms. We used the intertidal copepod Tigriopus japonicus as a test organism to demonstrate the adverse effects induced by MWCNTs in aquatic test organisms. The dispersion of the MWCNTs in seawater was maintained over 48 h without aggregation. MWCNTs caused a decrease in acute copper toxicity compared to the copper-only group in response to 20 and 100 mg/L MWCNTs, but not in response to 4 mg/L MWCNT, indicating that MWCNT may suppress acute copper toxicity. Reactive oxygen species (ROS) and enzymatic activities of glutathione S-transferase (GST) and catalase were significantly down-regulated in response to 100 mg/L MWCNT exposure. Glutathione (GSH) and glutathione reductase (GR) activity did not change significantly, indicating that MWCNTs may cause failure of the antioxidant system in T. japonicus. However, MWCNT induced extracellular signal-regulated kinase (ERK) activation without p38 and c-jun NH2-terminal kinase (JNK) activation, suggesting that ERK activation plays a key role in cell signaling pathways downstream of CNT exposure. This suggests that this pathway can be used as a biomarker for CNT exposure in T. japonicus. This study provides a better understanding of the cellular-damage response to MWCNTs.

Impact of single-walled carbon nanotubes on the embryo: a brief review

Carbon nanotubes (CNTs) are considered one of the most interesting materials in the 21st century due to their unique physiochemical characteristics and applicability to various industrial products and medical applications. However, in the last few years, questions have been raised regarding the potential toxicity of CNTs to humans and the environment; it is believed that the physiochemical characteristics of these materials are key determinants of CNT interaction with living cells and hence determine their toxicity in humans and other organisms as well as their embryos. Thus, several recent studies, including ours, pointed out that CNTs have cytotoxic effects on human and animal cells, which occur via the alteration of key regulator genes of cell proliferation, apoptosis, survival, cell-cell adhesion, and angiogenesis. Meanwhile, few investigations revealed that CNTs could also be harmful to the normal development of the embryo. In this review, we will discuss the toxic role of single-walled CNTs in the embryo, which was recently explored by several groups including ours.

Toxicity assessment and bioaccumulation in zebrafish embryos exposed to carbon nanotubes suspended in Pluronic® F-108

Carbon nanotubes (CNTs) are often suspended in Pluronic® surfactants by sonication, which may confound toxicity studies because sonication of surfactants can create degradation products that are toxic to mammalian cells. Here, we present a toxicity assessment of Pluronic® F-108 with and without suspended CNTs using embryonic zebrafish as an in vivo model. Pluronic® sonolytic degradation products were toxic to zebrafish embryos just as they were to mammalian cells. When the toxic Pluronic® fragments were removed, there was little effect of pristine multi-walled CNTs (pMWNTs), carboxylated MWNTs (cMWNTs) or pristine single-walled carbon nanotubes (pSWNTs) on embryo viability and development, even at high concentrations. A gel electrophoretic method coupled with Raman imaging was developed to measure the bioaccumulation of CNTs by zebrafish embryos, and dose-dependent uptake of CNTs was observed. These data indicate that embryos accumulate pMWNTs, cMWNTs and pSWNTs yet there is very little embryo toxicity.

Gestational nanomaterial exposures: microvascular implications during pregnancy, fetal development and adulthood

Air pollution particulate matter and engineered nanomaterials are encompassed in the broad definition of xenobiotic particles. While the effects of perinatal air pollution exposure have been investigated, elucidation of outcomes associated with nanomaterial exposure, the focus of this review, is still in its infancy. As the potential uses of nanomaterials, and therefore exposures, increase exponentially so does the need for thorough evaluation. Up to this point, the majority of research in the field of cardiovascular nanotoxicology has focused on the coronary and vascular reactions to pulmonary exposures in young adult, healthy, male models; however, as intentional and unintentional contacts persist, the non-pulmonary risks to under-represented populations become a critical concern. Development of the maternal-fetal circulation during successful mammalian gestation is one of the most unusual complex, dynamic, and acutely demanding physiological systems. Fetal development in a hostile gestational environment can lead to systemic alterations, which may encourage adult disease. Therefore, the purpose of this review is to highlight the few knowns associated with gestational engineered nanomaterial exposure segmented by physiological periods of development or systemic targets: preconception and maternal, gestational, fetal and progeny (Abstract figure). Overall, the limited studies currently available provide compelling evidence of maternal, fetal and offspring dysfunctions after engineered nanomaterial exposure. Understanding the mechanisms associated with these multigenerational effects may allow pregnant women to safely reap the benefits of nanotechnology-enabled products and assist in the implementation of exposure controls to protect the mother and fetus allowing for development of safety by design for engineered nanomaterials.

Toward safer multi-walled carbon nanotube design: Establishing a statistical model that relates surface charge and embryonic zebrafish mortality

Given the increased utility and lack of consensus regarding carbon nanotube (CNT) environmental and human health hazards, there is a growing demand for guidelines that inform safer CNT design. In this study, the zebrafish (Danio rerio) model is utilized as a stable, sensitive biological system to evaluate the bioactivity of systematically modified and comprehensively characterized multi-walled carbon nanotubes (MWNTs). MWNTs were treated with strong acid to introduce oxygen functional groups, which were then systematically thermally reduced and removed using an inert temperature treatment. While 25 phenotypic endpoints were evaluated at 24 and 120 hours post-fertilization (hpf), high mortality at 24 hpf prevented further resolution of the mode of toxicity leading to mortality. Advanced multivariate statistical methods are employed to establish a model that identifies those MWNT physicochemical properties that best estimate the probability of observing an adverse outcome. The physicochemical properties considered in this study include surface charge, percent surface oxygen, dispersed aggregate size and morphology and electrochemical activity. Of the five physicochemical properties, surface charge, quantified as the point of zero charge (PZC), was determined as the best predictor of mortality at 24 hpf. From a design perspective, the identification of this property-hazard relationship establishes a foundation for the development of design guidelines for MWNTs with reduced hazard.

Acute toxicity comparison of single-walled carbon nanotubes in various freshwater organisms

While the commercialization of single-walled carbon nanotubes (SWCNTs) is rapidly expanding, the environmental impact of this nanomaterial is not well understood. Therefore, the present study evaluates the acute aquatic toxicity of SWCNTs towards two freshwater microalgae (Raphidocelis subcapitata and Chlorella vulgaris), a microcrustacean (Daphnia magna), and a fish (Oryzias latipes) based on OECD test guidelines (201, 202, and 203). According to the results, the SWCNTs inhibited the growth of the algae R. subcapitata and C. vulgaris with a median effective concentration (EC₅₀) of 29.99 and 30.96 mg/L, respectively, representing “acute category 3” in the Globally Harmonized System (GHS) of classification and labeling of chemicals. Meanwhile, the acute toxicity test using O. latipes and D. magna did not show any mortality/immobilizing effects up to a concentration of 100.00 mg/L SWCNTs, indicating no hazard category in the GHS classification. In conclusion, SWCNTs were found to induce acute ecotoxicity in freshwater microalgae, yet not in D. magna and medaka fish.

In vitro and in vivo toxicology of bare and PEGylated fluorescent carbonaceous nanodots in mice and zebrafish: the potential relationship with autophagy

The toxicity of CDs in mice and zebrafish and the potential relationship between toxicity and autophagy was evaluated.

Speciation of metal(loid)s in environmental samples by X-ray absorption spectroscopy: a critical review

Element specificity is one of the key factors underlying the widespread use and acceptance of X-ray absorption spectroscopy (XAS) as a research tool in the environmental and geo-sciences. Independent of physical state (solid, liquid, gas), XAS analyses of metal(loid)s in complex environmental matrices over the past two decades have provided important information about speciation at environmentally relevant interfaces (e.g. solid-liquid) as well as in different media: plant tissues, rhizosphere, soils, sediments, ores, mineral process tailings, etc. Limited sample preparation requirements, the concomitant ability to preserve original physical and chemical states, and independence from crystallinity add to the advantages of using XAS in environmental investigations. Interpretations of XAS data are founded on sound physical and statistical models that can be applied to spectra of reference materials and mixed phases, respectively. For spectra collected directly from environmental matrices, abstract factor analysis and linear combination fitting provide the means to ascertain chemical, bonding, and crystalline states, and to extract quantitative information about their distribution within the data set. Through advances in optics, detectors, and data processing, X-ray fluorescence microprobes capable of focusing X-rays to micro- and nano-meter size have become competitive research venues for resolving the complexity of environmental samples at their inherent scale. The application of μ-XANES imaging, a new combinatorial approach of X-ray fluorescence spectrometry and XANES spectroscopy at the micron scale, is one of the latest technological advances allowing for lateral resolution of chemical states over wide areas due to vastly improved data processing and detector technology.

Bioaccumulation and ecotoxicity of carbon nanotubes

Carbon nanotubes (CNT) have numerous industrial applications and may be released to the environment. In the aquatic environment, pristine or functionalized CNT have different dispersion behavior, potentially leading to different risks of exposure along the water column. Data included in this review indicate that CNT do not cross biological barriers readily. When internalized, only a minimal fraction of CNT translocate into organism body compartments. The reported CNT toxicity depends on exposure conditions, model organism, CNT-type, dispersion state and concentration. In the ecotoxicological tests, the aquatic organisms were generally found to be more sensitive than terrestrial organisms. Invertebrates were more sensitive than vertebrates. Single-walled CNT were found to be more toxic than double-/multi-walled CNT. Generally, the effect concentrations documented in literature were above current modeled average environmental concentrations. Measurement data are needed for estimation of environmental no-effect concentrations. Future studies with benchmark materials are needed to generate comparable results. Studies have to include better characterization of the starting materials, of the dispersions and of the biological fate, to obtain better knowledge of the exposure/effect relationships.

Effects of nanotoxicity on female reproductivity and fetal development in animal models

The extensive application of nanomaterials in industry, medicine and consumer products has raised concerns about their potential toxicity. The female population is particularly vulnerable and deserves special attention because toxicity in this group may impact both female reproductivity and fetal development. Mouse and zebrafish models each have their own unique features and studies using these models to examine the potential toxicity of various nanoparticles are compared and summarized in this review. Several nanoparticles exhibit detrimental effects on female reproductivity as well as fetal development, and these adverse effects are related to nanoparticle composition, surface modification, dose, exposure route and animal species. Limited studies on the mechanisms of nanotoxicity are also documented and reviewed herein.

Evaluation of biotargeting and ecotoxicity of Co²⁺-containing nanoscale polymeric complex by applying multi-marker approach in bivalve mollusk Anodonta cygnea

Cobalt (Co(2+)) is present in many nanoscaled materials created for various applications. The key goal of our study was to develop sensitive approaches for assessing the bio-risks associated with using novel Co(2+)-containing nanoscaled polymeric complex (Co-NC). Freshwater bivalve mollusk Anodonta cygnea (Unionidae) was subjected to 14 d action of the developed Co-NC, as well as of Co(2+) applied in the corresponding concentration (50 μg L(-1)) or polymeric substance (PS). All experimental groups under study have demonstrated signs of toxic targeting, notably changes in DNA characteristics, oxidative stress (with particularities in each exposed group) and activation of anaerobiosis (Co(2+) and Co-NC). However, the group exposed to Co-NC showed some advantages that can be related to the activation of metallothionein (MT) function (increase in the level of MT-related SH-groups (MT-SH)): low level of oxyradical formation, no increase in protein carbonylation and vitellogenin-like proteins concentration unlike in Co(2+) and PS exposed groups. On the other hand, Co(2+) increased metal (Co, Cu, Zn and Cd) binding to MT (MT-Me) without changes in MT-SH level jointly with activation of oxyradical formation and apoptosis and decreasing of lysosomal membrane stability. PS per se initiated unbalanced changes in activities of the biotransformation enzymes ethoxyresorufin-O-deethylase and glutathione-S-transferase. Thus, Co(2+) complexing with the developed PS prevented bio-toxic effects of free Co(2+) ions and PS per se, at least in the studied hydrobiont. The MT-SH was the main distinguishing index of Co-NC group selected by classification and regression tree analysis.

The primacy of physicochemical characterization of nanomaterials for reliable toxicity assessment: a review of the zebrafish nanotoxicology model

Engineered nanomaterials (ENMs) have become increasingly prevalent in the past two decades in academic, medical, commercial, and industrial settings. The unique properties imbued with nanoparticles, as the physiochemical properties change from the bulk material to the surface atoms, present unique and often challenging characteristics that larger macromolecules do not possess. While nanoparticle characteristics are indeed exciting for unique chemistries, surface properties, and diverse applications, reports of toxicity and environmental impacts have tempered this enthusiasm and given cause for an exponential increase for concomitant nanotoxicology assessment. Currently, nanotoxicology is a steadily growing with new literature and studies being published more frequently than ever before; however, the literature reveals clear, inconsistent trends in nanotoxicological assessment. At the heart of this issue are several key problems including the lack of validated testing protocols and models, further compounded by inadequate physicochemical characterization of the nanomaterials in question and the seminal feedback loop of chemistry to biology back to chemistry. Zebrafish (Danio rerio) are emerging as a strong nanotoxicity model of choice for ease of use, optical transparency, cost, and high degree of genomic homology to humans. This review attempts to amass all contemporary nanotoxicology studies done with the zebrafish and present as much relevant information on physicochemical characteristics as possible. While this report is primarily a physicochemical summary of nanotoxicity studies, we wish to strongly emphasize that for the proper evolution of nanotoxicology, there must be a strong marriage between the physical and biological sciences. More often than not, nanotoxicology studies are reported by groups dominated by one discipline or the other. Regardless of the starting point, nanotoxicology must be seen as an iterative process between chemistry and biology. It is our sincere hope that the future will introduce a paradigm shift in the approach to nanotoxicology with multidisciplinary groups for data analysis to produce predictive and correlative models for the end goal of rapid preclinical development of new therapeutics into the clinic or insertion into environmental protection.

Environmental and health effects of nanomaterials in nanotextiles and façade coatings

Engineered nanomaterials (ENM) are expected to hold considerable potential for products that offer improved or novel functionalities. For example, nanotechnologies could open the way for the use of textile products outside their traditional fields of applications, for example, in the construction, medical, automobile, environmental and safety technology sectors. Consequently, nanotextiles could become ubiquitous in industrial and consumer products in future. Another ubiquitous field of application for ENM is façade coatings. The environment and human health could be affected by unintended release of ENM from these products. The product life cycle and the product design determine the various environmental and health exposure situations. For example, ENM unintentionally released from geotextiles will probably end up in soils, whereas ENM unintentionally released from T-shirts may come into direct contact with humans and end up in wastewater. In this paper we have assessed the state of the art of ENM effects on the environment and human health on the basis of selected environmental and nanotoxicological studies and on our own environmental exposure modeling studies. Here, we focused on ENM that are already applied or may be applied in future to textile products and façade coatings. These ENM's are mainly nanosilver (nano-Ag), nano titanium dioxide (nano-TiO(2)), nano silica (nano-SiO(2)), nano zinc oxide (nano-ZnO), nano alumina (nano-Al(2)O(3)), layered silica (e.g. montmorillonite, Al(2)[(OH)(2)/Si(4)O(10)]nH(2)O), carbon black, and carbon nanotubes (CNT). Knowing full well that innovators have to take decisions today, we have presented some criteria that should be useful in systematically analyzing and interpreting the state of the art on the effects of ENM. For the environment we established the following criteria: (1) the indication for hazardous effects, (2) dissolution in water increases/decreases toxic effects, (3) tendency for agglomeration or sedimentation, (4) fate during waste water treatment, and (5) stability during incineration. For human health the following criteria were defined: (1) acute toxicity, (2) chronic toxicity, (3) impairment of DNA, (4) crossing and damaging of tissue barriers, (5) brain damage and translocation and effects of ENM in the (6) skin, (7) gastrointestinal or (8) respiratory tract. Interestingly, some ENM might affect the environment less severely than they might affect human health, whereas the case for others is vice versa. This is especially true for CNT. The assessment of the environmental risks is highly dependent on the respective product life cycles and on the amounts of ENM produced globally.

Low doses of pristine and oxidized single-wall carbon nanotubes affect mammalian embryonic development

Several in vitro and in vivo studies suggest local and systemic effects following exposure to carbon nanotubes. No data are available, however, on their possible embryotoxicity in mammals. In this study, we tested the effect of pristine and oxidized single-wall carbon nanotubes (SWCNTs) on the development of the mouse embryo. To this end, SWCNTs (from 10 ng to 30 μg/mouse) were administered to female mice soon after implantation (postcoital day 5.5); 10 days later, animals were sacrificed, and uteri, placentas, and fetuses examined. A high percentage of early miscarriages and fetal malformations was observed in females exposed to oxidized SWCNTs, while lower percentages were found in animals exposed to the pristine material. The lowest effective dose was 100 ng/mouse. Extensive vascular lesions and increased production of reactive oxygen species (ROS) were detected in placentas of malformed but not of normally developed fetuses. Increased ROS levels were likewise detected in malformed fetuses. No increased ROS production or evident morphological alterations were observed in maternal tissues. No fetal and placental abnormalities were ever observed in control animals. In parallel, SWCNT embryotoxicity was evaluated using the embryonic stem cell test (EST), a validated in vitro assay developed for predicting embryotoxicity of soluble chemical compounds, but never applied in full to nanoparticles. The EST predicted the in vivo data, identifying oxidized SWCNTs as the more toxic compound.

Review: Do engineered nanoparticles pose a significant threat to the aquatic environment?

Nanotechnology is a rapidly growing industry of global economic importance, exploiting the novel characteristics of materials manufactured at the nanoscale. The properties of engineered nanoparticles (ENPs) that make them useful in a wide range of industrial applications, however, have led to concerns regarding their potential impact on human and environmental health. The aquatic environment is particularly at risk of exposure to ENPs, as it acts as a sink for most environmental contaminants. This paper critically evaluates what is currently known about sources and discharge of ENPs to the aquatic environment and how the physicochemical characteristics of ENPs affect their fate and behaviour and thus availability for uptake into aquatic organisms, and assesses reported toxicological effects. Having reviewed the ecotoxicological information, the conclusion is that whilst there are data indicating some nanoparticles have the potential to induce harm in exposed aquatic organisms, there is insufficient evidence for harm, for known/modelled environmental concentrations for almost all ENPs considered. This conclusion, however, must be balanced by the fact that there are significant gaps in our understanding on the fate and behaviour of ENPs in the aquatic environment. Greater confidence in the assessments on ENP impacts in aquatic systems to enable effective comparisons across studies urgently requires more standardised approaches for ENP hazard identification, and critically, more thorough characterisations on the exposed particles. There is also an urgent need for the advancement of tools and techniques that can accurately quantify and visualise uptake of nanoparticles into biological tissues.

Possibilities and limitations of modeling environmental exposure to engineered nanomaterials by probabilistic material flow analysis

Information on environmental concentrations is needed to assess the risks that engineered nanomaterials (ENM) may pose to the environment. In this study, predicted environmental concentrations (PEC) were modeled for nano-TiO2, carbon nanotubes (CNT) and nano-Ag for Switzerland. Based on a life-cycle perspective, the model considered as input parameters the production volumes of the ENMs, the manufacturing and consumption quantities of products containing those materials, and the fate and pathways of ENMs in natural and technical environments. Faced with a distinct scarcity of data, we used a probabilistic material flow analysis model, treating all parameters as probability distributions. The modeling included Monte Carlo and Markov Chain Monte Carlo simulations as well as a sensitivity and uncertainty analysis. The PEC values of the ENMs in the different environmental compartments vary widely due to different ENM production volumes and different life cycles of the nanoproducts. The use of ENM in products with high water relevance leads to higher water and sediment concentrations for nano-TiO2 and nano-Ag, compared to CNTs, where smaller amounts of ENM reach the aquatic compartments. This study also presents a sensitivity analysis and a comprehensive discussion of the uncertainties of the simulation results and the limitations of the used approach. To estimate potential risks, the PEC values were compared to the predicted-no-effect concentrations (PNEC) derived from published data. The risk quotients (PEC/PNEC) for nano-TiO2 and nano-Ag were larger than one for treated wastewater and much smaller for all other environmental compartments (e.g., water, sediments, soils). We conclude that probabilistic modeling is very useful for predicting environmental concentrations of ENMs given the current lack of substantiated data.

Potential for occupational exposure to engineered carbon-based nanomaterials in environmental laboratory studies

BACKGROUND

The potential exists for laboratory personnel to be exposed to engineered carbon-based nanomaterials (CNMs) in studies aimed at producing conditions similar to those found in natural surface waters [e.g., presence of natural organic matter (NOM)].

OBJECTIVE

The goal of this preliminary investigation was to assess the release of CNMs into the laboratory atmosphere during handling and sonication into environmentally relevant matrices.

METHODS

We measured fullerenes (C60), underivatized multiwalled carbon nanotubes (raw MWCNT), hydroxylated MWCNT (MWCNT-OH), and carbon black (CB) in air as the nanomaterials were weighed, transferred to beakers filled with reconstituted freshwater, and sonicated in deionized water and reconstituted freshwater with and without NOM. Airborne nanomaterials emitted during processing were quantified using two hand-held particle counters that measure total particle number concentration per volume of air within the nanometer range (10-1,000 nm) and six specific size ranges (300-10,000 nm). Particle size and morphology were determined by transmission electron microscopy of air sample filters.

DISCUSSION

After correcting for background particle number concentrations, it was evident that increases in airborne particle number concentrations occurred for each nanomaterial except CB during weighing, with airborne particle number concentrations inversely related to particle size. Sonicating nanomaterial-spiked water resulted in increased airborne nanomaterials, most notably for MWCNT-OH in water with NOM and for CB.

CONCLUSION

Engineered nanomaterials can become airborne when mixed in solution by sonication, especially when nanomaterials are functionalized or in water containing NOM. This finding indicates that laboratory workers may be at increased risk of exposure to engineered nanomaterials.