Interactions of oxidized multiwalled carbon nanotube with cadmium on zebrafish cell line: The influence of two co-exposure protocols on in vitro toxicity tests

Carbon nanotubes and nanofibers seen as emerging threat to fish: Historical review and trends

Since the discovery of the third allotropic carbon form, carbon-based one-dimensional nanomaterials (1D-CNMs) became an attractive and new technology with different applications that range from electronics to biomedical and environmental technologies. Despite their broad application, data on environmental risks remain limited. Fish are widely used in ecotoxicological studies and biomonitoring programs. Thus, the aim of the current study was to summarize and critically analyze the literature focused on investigating the bioaccumulation and ecotoxicological impacts of 1D-CNMs (carbon nanotubes and nanofibers) on different fish species. In total, 93 articles were summarized and analyzed by taking into consideration the following aspects: bioaccumulation, trophic transfer, genotoxicity, mutagenicity, organ-specific toxicity, oxidative stress, neurotoxicity and behavioral changes. Results have evidenced that the analyzed studies were mainly carried out with multi-walled carbon nanotubes, which were followed by single-walled nanotubes and nanofibers. Zebrafish (Danio rerio) was the main fish species used as model system. CNMs' ecotoxicity in fish depends on their physicochemical features, functionalization, experimental design (e.g. exposure time, concentration, exposure type), as well as on fish species and developmental stage. CNMs' action mechanism and toxicity in fish are associated with oxidative stress, genotoxicity, hepatotoxicity and cardiotoxicity. Overall, fish are a suitable model system to assess the ecotoxicity of, and the environmental risk posed by, CNMs.

TiO2-MWCNT nanohybrid: Cytotoxicity, protein corona formation and cellular internalisation in RTG-2 fish cell line

Titanium dioxide nanoparticles-multiwalled carbon nanotubes (TiO_2-MWCNT) nanohydrid has an enhanced photocatalytic activity across the visible light with promising applications in environmental remediation, solar energy devices and antimicrobial technologies. However, it is necessary to evaluate the toxicological effects of TiO_2-MWCNT towards safe and sustainable development of nanohybrids. In this work, we studied the cytotoxicity, protein corona formation and cellular internalisation of TiO_2-MWCNT on fibroblasts derived from gonadal rainbow trout tissue (RTG-2) for the first time. This nanohydrid did not show any toxicity effect on RTG-2 cells up to 100 mg L^-1 after 24 h of exposure as monitored by alamar blue, neutral red and trypan blue assays (in presence or absence of foetal bovine serum, FBS). Futhermore, cryo-transmission electron microscopy analysis demonstrated that TiO₂ particles is attached on nanotube surface after FBS-protein corona formation in cell culture medium. Raman spectroscopy imaging showed that TiO_2-MWCNT can be internalised by RTG-2 cells. This work is a novel contribution towards better understanding the nanobiointeractions of nanohydrids linked to their in vitro effects on fish cells in aquatic nanoecotoxicology.

In vitro comparative cytotoxic assessment of pristine and carboxylic functionalized multiwalled carbon nanotubes on LN18 cells

Multiwalled carbon nanotubes (MWCNTs) have been used in biomedical applications due to their ability to enter the cells. Carboxylic functionalization of MWCNT (MWCNT-COOH) is used to mitigate the toxicity of MWCNTs. Our study focuses on comparing the toxicity of MWCNT and MWCNT-COOH on the neuronal cells, LN18. Concentrations of 5, 10, 20, and 40 µg ml-1 were used for the study, and cytotoxicity was determined at 0, 1, 3, 6, 12, 24, and 48 h of incubation. Cell viability was assessed by Trypan Blue, MTT, and Live dead cell assays, and the oxidative stress produced was determined by reactive oxygen species (ROS) and Lipid peroxidation assays. MWCNT-COOH showed higher cell viability than MWCNT for 20 and 40 µg ml-1 at 24 and 48 h. This was also visually observed in the live dead cell imaging. However, at 48 h, the morphology of the cells appeared more stretched for all the concentrations of MWCNT and MWCNT-COOH in comparison to the control. A significant amount of ROS production can also be observed at the same concentration and time. Viability and oxidative stress results together revealed that MWCNT-COOH is less toxic when compared to MWCNT at longer incubation periods and higher concentrations. However, otherwise, the effect of both are comparable. A concentration of 5-10 µg ml-1 is ideal while using MWCNT and MWCNT-COOH as the toxicity is negligible. These findings can further be extended to various functionalizations of MWCNT for wider applications.

Concentration- and time-dependence toxicity of graphene oxide (GO) and reduced graphene oxide (rGO) nanosheets upon zebrafish liver cell line

Graphene oxide (GO) and reduced graphene oxide (rGO) are carbon-based nanomaterials that have a wide range of applicability. Therefore, it is expected that their residual traces reach the aquatic environment, accumulate, and interact with its different compartments and the biota living in them. The concentration- and time-dependency response to GO and rGO in aquatic organisms are still poorly known. In the present study, the effects of GO and rGO on zebrafish hepatocytes were investigated using in vitro assays performed with established liver cell lines from zebrafish (ZFL). GO and rGO nanosheets were applied on ZFL cells at a concentration range of 1-100 µg mL^-1 for 24 and 72 h. The internalization of GO and rGO nanosheets, reactive oxygen species (ROS) production, cell viability, and cell death were evaluated. The internalization of GO increased as the concentrations of GO increased. The rGO nanosheets were smaller than GO nanosheets, and their hydrophobic characteristic favors their interaction with the cell membrane. However, the rGO nanosheets were not observed in the uptake assay. Exposure for 72 h was found to cause harmful effects in ZFL cells, causing higher ROS production in cells exposed to rGO and stopping cell replication. Nevertheless, GO did not stop cell replication, but exposed cells had higher levels of apoptosis and necrosis. After 72 h, both GO and rGO were toxic, but with different mechanisms of toxicity.

Multi-walled carbon nanotubes impact on the enantioselective bioaccumulation and toxicity of the chiral insecticide bifenthrin to zebrafish (Danio rerio)

The effects of different multi-walled carbon nanotubes on the enantioselective bioaccumulation and toxicity of the chiral pesticide bifenthrin to zebrafish were investigated in this work. The results showed that MWCNTs and MWCNTs-COOH did not affect the preferential bioaccumulation of 1R-cis-BF in zebrafish following exposure to cis-BF enantiomers for 28 days, but which increased cis-BF accumulation amount by 1.03-1.48 times. Further research demonstrated that the genes related to immunity, endocrine activity and neurotoxicity showed enantioselective expression in different zebrafish tissues, and sex-specific differences were observed. The levels of c-fos, th, syn2a, 17β-hsd and cc-chem were expressed as 1.09-2.84 times higher in females and males treated with 1R-cis-BF than in the 1S-cis-BF-treated groups. However, in the presence of MWCNTs or MWCNTs-COOH, c-fos, th, syn2a, 17β-hsd and cc-chem levels were expressed as 1.53-14.92 times higher in females and males treated with 1S-cis-BF than in 1R-cis-BF-treated groups, which indicated that enantioselective expression was altered. The effects of different types of MWCNTs on the enantioselective bioaccumulation and toxicity of BF in zebrafish have little difference. In summary, the presence of MWCNTs or MWCNTs-COOH increased the impact of BF on zebrafish. Therefore, the risks posed by coexisting nanomaterials and chiral pesticides in aquatic environments should be considered.

The influence of salinity on the toxicity of remediated seawater

Mercury (Hg) is one of the most hazardous pollutants, due to its toxicity, biological magnification and worldwide persistence in aquatic systems. Thus, new efficient nanotechnologies (e.g. graphene oxide functionalized with polyethyleneimine (GO-PEI)) have been developed to remove this metal from the water. Aquatic environments, in particular transitional systems, are also subjected to disturbances resulting from climate change, such as salinity shifts. Salinity is one of the most relevant factors that influences the distribution and survival of aquatic species such as mussels. To our knowledge, no studies assessed the ecotoxicological impairments induced in marine organisms exposed to remediate seawater (RSW) under different salinity levels. For this, the focus of the present study was to evaluate the effects of seawater previously contaminated with Hg and remediated with GO-PEI, using the species Mytilus galloprovincialis, maintained at three different salinities (30, 20 and 40). The results obtained demonstrated similar histopathological and metabolic alterations, oxidative stress and neurotoxicity in mussels under RSW treatment at stressful salinity conditions (20 and 40) in comparison to control salinity (30). On the other hand, the present findings revealed toxicological effects including cellular damage and histopathological impairments in mussels exposed to Hg contaminated seawater in comparison to non-contaminated ones, at each salinity level. Overall, these results confirm the high efficiency of GO-PEI to sorb Hg from water with no noticeable toxic effects even under different salinities, leading to consider it a promising eco-friendly approach to remediate contaminated water.

Metallic nanoparticle contamination from environmental atmospheric particulate matter in the last slab of the trophic chain: Nanocrystallography, subcellular localization and toxicity effects

Atmospheric particulate material (PM) from mining and steel industries comprises several metallic contaminants. PM₁₀ samples collected in a Brazilian region with a recognized influence of the steel and iron pelletizing industries were used to investigate metallic nanoparticle incorporation into human fibroblast cells (MRC-5). MRC-5 cells were exposed to 0 (control, ultrapure water), 2.5, 5, 10, 20 and 40 μg PM₁₀ mL^-1, for 24 h. Cytotoxic and genotoxic dose-response effects were observed on lysosome and DNA structure, and concentrations high as 20 and 40 μg PM₁₀ mL^-1 induced elevated cell death. Ultrastructure analyses showed aluminosilicate, iron, and the emerging metallic contaminants titanium, bismuth, and cerium nanoparticles were incorporated into lung cells, in which the nanocrystallography analysis indicated the bismuth as Bi₂O₃. All internalized metallic nanoparticles were free and unbound in the cytoplasm and nucleus thereby indicating bioavailability and potential interaction to biological processes and cellular structures. Pearson's correlation analysis showed Fe, Ni, Al, Cr, Pb and Hg as the main cytotoxic elements which are associated with the stainless steel production. The presence of internalized nanoparticles in human lung cells exposed to environmental atmospheric matter highlights the need for a greater effort by regulatory agencies to understand their potential damage and hence the need for future regulation, especially of emerging metallic contaminants.

Magnetic Mesoporous Silica Nanorods Loaded with Ceria and Functionalized with Fluorophores for Multimodal Imaging

Multifunctional magnetic nanocomposites based on mesoporous silica have a wide range of potential applications in catalysis, biomedicine, or sensing. Such particles combine responsiveness to external magnetic fields with other functionalities endowed by the agents loaded inside the pores or conjugated to the particle surface. Different applications might benefit from specific particle morphologies. In the case of biomedical applications, mesoporous silica nanospheres have been extensively studied while nanorods, with a more challenging preparation, have attracted much less attention despite the positive impact on the therapeutic performance shown by seminal studies. Here, we report on a sol-gel synthesis of mesoporous rodlike silica particles of two distinct lengths (1.4 and 0.9 μm) and aspect ratios (4.7 and 2.2) using Pluronic P123 as a structure-directing template and rendering ∼1 g of rods per batch. Iron oxide nanoparticles have been synthesized within the pores yielding maghemite (γ-Fe₂O₃) nanocrystals of elongated shape (∼7 nm × 5 nm) with a [110] preferential orientation along the rod axis and a superparamagnetic character. The performance of the rods as T₂-weighted MRI contrast agents has also been confirmed. In a subsequent step, the mesoporous silica rods were loaded with a cerium compound and their surface was functionalized with fluorophores (fluorescamine and Cyanine5) emitting at λ = 525 and 730 nm, respectively, thus highlighting the possibility of multiple imaging modalities. The biocompatibility of the rods was evaluated in vitro in a zebrafish (Danio rerio) liver cell line (ZFL), with results showing that neither long nor short rods with magnetic particles caused cytotoxicity in ZFL cells for concentrations up to 50 μg/ml. We advocate that such nanocomposites can find applications in medical imaging and therapy, where the influence of shape on performance can be also assessed.

Citrullinated vimentin mediates development and progression of lung fibrosis

The mechanisms by which environmental exposures contribute to the pathogenesis of lung fibrosis are unclear. Here, we demonstrate an increase in cadmium (Cd) and carbon black (CB), common components of cigarette smoke (CS) and environmental particulate matter (PM), in lung tissue from subjects with idiopathic pulmonary fibrosis (IPF). Cd concentrations were directly proportional to citrullinated vimentin (Cit-Vim) amounts in lung tissue of subjects with IPF. Cit-Vim amounts were higher in subjects with IPF, especially smokers, which correlated with lung function and were associated with disease manifestations. Cd/CB induced the secretion of Cit-Vim in an Akt1- and peptidylarginine deiminase 2 (PAD2)-dependent manner. Cit-Vim mediated fibroblast invasion in a 3D ex vivo model of human pulmospheres that resulted in higher expression of CD26, collagen, and α-SMA. Cit-Vim activated NF-κB in a TLR4-dependent fashion and induced the production of active TGF-β1, CTGF, and IL-8 along with higher surface expression of TLR4 in lung fibroblasts. To corroborate ex vivo findings, mice treated with Cit-Vim, but not Vim, independently developed a similar pattern of fibrotic tissue remodeling, which was TLR4 dependent. Moreover, wild-type mice, but not PAD2^-/- and TLR4 mutant (MUT) mice, exposed to Cd/CB generated high amounts of Cit-Vim, in both plasma and bronchoalveolar lavage fluid, and developed lung fibrosis in a stereotypic manner. Together, these studies support a role for Cit-Vim as a damage-associated molecular pattern molecule (DAMP) that is generated by lung macrophages in response to environmental Cd/CB exposure. Furthermore, PAD2 might represent a promising target to attenuate Cd/CB-induced fibrosis.

Effects of multiwalled carbon nanotubes co-exposure with cadmium on zebrafish cell line: Metal uptake and accumulation, oxidative stress, genotoxicity and cell cycle

Carbon nanotubes presence in the environment increases every year because of exponential industrial production around the world. In aquatic environments, carbon nanotubes can interact with other pollutants based on their adsorbent surface chemistry properties. Heavy metal ions represent one of the biggest concerns in water resources nowadays due to anthropogenic activities, in which cadmium (Cd) is one of the most harmful metal for aquatic organisms. This study investigated the influence of two co-exposure protocols differing by the order of interaction of oxidized multiwalled carbon nanotubes (ox-MWCNT) with Cd in zebrafish liver cell line (ZFL). The ox-MWCNT was characterized, Cd content in culture medium and uptake by cells were quantified using ICP-MS and, the reactive oxygen species (ROS), the biotransformation enzymes activity of phase I and II as well as the antioxidants defenses and oxidative damage were analyzed. The effects on the cell cycle were investigated by flow cytometry and DNA damage by comet assay. The exposure to ox-MWCNT alone decreased the activity of catalase, glutathione peroxidase, and glutathione S-transferase and altered the cell cycle with a reduction of cells in the G2/M phase. Cd exposure alone decreased the activity of catalase and glutathione S-transferase, increased ROS, metallothionein, and lipid peroxidation content and causes genotoxicity in the cells. Despite different incubation protocol, the co-exposure ox-MWCNT-Cd increased the Cd content in ZFL cells after 24 h exposure, increased ROS production and DNA damage without differences between them. Our results showed the modulation of ox-MWCNT on Cd effects and contributed to future co-exposure toxicity investigations and nanosafety regulations involving carbon nanomaterials and aquatic pollutants.

Removal of polycyclic aromatic hydrocarbon (PAH)-contaminated sediments by persulfate oxidation and determination of degradation product cytotoxicity based on HepG2 and ZF4 cell lines

This study evaluated the use of magnetite (Fe₃O₄), carbon black (CB), and Fe₃O₄-CB composites activated by persulfate (PS) at circumneutral pH to oxidize polycyclic aromatic hydrocarbons (PAHs) in marine sediments. In addition, the in vitro cytotoxic activity and apoptotic response of the obtained degradation products were investigated. Chemical analyses showed that the total PAH concentration was 26,263 ng/g for sediment samples from an industrial port area. Highly toxic BaP was the main contributor to the TEQ in sediments. Source analyses demonstrated that the PAHs in the sediment were derived from coal combustion. In this study, we found that the PS oxidation processes effectively degrade PAHs at concentration levels of 1.7 × 10^-5 M at pH 6.0. The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay was employed to assess the cytotoxicity of the PAH degradation products before and after Fe₃O₄/PS, CB/PS, and Fe₃O₄-CB/PS oxidation treatment using a human hepatoma carcinoma cell line (HepG2) and a zebrafish (Danio rerio) embryonic cell line (ZF4). Each sample extract showed a marked dose-related response, with the cell viability reduced by 82% in the case of HepG2 and 58% in the case of ZF4 at 100 μg/mL after the Fe₃O₄-CB/PS process. The PAH degradation products had different effects on the cell morphologies of the two cell lines. The results suggested that the ZF4 cell model is more sensitive than HepG2 to the toxicity of the PAH samples.

Does salinity variation increase synergistic effects of triclosan and carbon nanotubes on Mytilus galloprovincialis? Responses on adult tissues and sperms

The use of carbon nanotubes (CNTs) is rapidly increasing and several scientific studies have addressed their toxicological properties. However, only a very small number of publications have deal with the interaction between CNTs and other molecules. Triclosan (TCS) is an antibacterial agent used in personal care and household products. Commonly detected in aquatic ecosystems, there is a strong evidence that aquatic biota is sensitive to this compound. Aside from emergent pollutants, aquatic organisms are continuously subjected to abiotic variations including salinities. Therefore, the main goal of the present study was to better understand how physio-chemical interactions of CNTs with TCS under different salinity levels (37, 28 and 19) affect the mussel species Mytilus galloprovincialis through the evaluation of biochemical alterations on gametes (sperms) and adult tissues, providing more ecologically relevant information on organisms' responses. The results showed toxicological effects in terms of sperm metabolic activity and intracellular reactive oxygen species production as well as cellular damage and alteration of metabolic capacity at the adult's stage when exposed to both contaminants acting alone and in combination, under tested salinities. Moreover, when the mussels were exposed to the combination of both contaminants, they showed major toxic impacts on both assessed biological levels (adult tissues and sperms) especially under control salinity. This suggests that toxicity upon mixture exposure compared to single-substance exposure may impair mussels' populations, affecting reproduction success and growth.

Antagonistic effects of multi-walled carbon nanotubes and BDE-47 in zebrafish (Danio rerio): Oxidative stress, apoptosis and DNA damage

In natural environments, organisms are often exposed to several environmental pollutants at any one time, and the potential effects of such co-exposures on human and environmental health are of considerable concern. It is thought that multi-walled carbon nanotubes (MWCNTs) may interact with other pollutants in aquatic systems and induce considerably different effects compared with exposure to a single contaminant. The objective of this study was to evaluate the potential acute combined effects of mixtures of MWCNTs and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on embryonic development stages, oxidative stress, apoptosis and DNA damage in developing zebrafish (Danio rerio). The embryos were treated with BDE-47 (5, 10, and 50 μg/L) and MWCNTs (50 mg/L), either combined or individually, for 96 h. Following exposure, BDE-47 induced significant acute toxicity, while the MWCNTs exhibited slight toxicity. When compared with BDE-47-only exposure, the inhibited growth induced by BDE-47 was weakened in the presence of MWCNTs. Similarly, the levels of oxidative stress biomarkers (reactive oxygen species, superoxide dismutase, catalase activities and malondialdehyde), apoptosis (apoptosis rate, caspase-3 and caspase-9 activities) and DNA damage (comet assay and comet olive tails) decreased in the presence of MWCNTs compared to those exposed to BDE-47 alone. These results demonstrate that MWCNTs can weaken the developmental inhibition, oxidative stress, apoptosis and DNA damage induced by BDE-47 in the early stages of zebrafish development.

Integrative transcriptome analysis and discovery of signaling pathways involved in the protective effects of curcumin against oxidative stress in tilapia hepatocytes

Summer outbreaks of the hepatobiliary syndrome in fish impose a heavy burden on aquaculture in China. Curcumin is a polyphenol with antioxidant activity that has been used to protect the health of fish livers, but the mechanism underlying its protective effect is unclear. In this study, an in vitro model of hepatocyte oxidative damage in Oreochromis niloticus was established using H₂O₂. Treatment with 5 mM H₂O₂ for 2.5 h markedly reduced cell viability and antioxidant activity and elevated lactate dehydrogenase (LDH) activity, indicating conditions that can be used to establish an oxidative stress model. Under H₂O₂ stress, curcumin pretreatment significantly maintained cell viability, reduced malondialdehyde (MDA) levels, and increased superoxide dismutase (SOD) activity. RNA-seq results showed that acute H₂O₂ treatment resulted in minor changes in gene expression, whereas curcumin changed the expression profile and affected cytochrome P450 (Cyp 450), glutathione (GSH) metabolism, and the peroxisome proliferator-activated receptor (PPAR) signaling pathway. Several critical antioxidant defense signaling pathways were identified, and altered expression was confirmed by q-PCR. These results indicate that curcumin might upregulate PPAR expression by increasing Cyp2J2 expression. Further experiments showed that curcumin can upregulate the Nrf2-Keap1 signaling pathway at the transcriptional level, and this upregulation can induce downstream defense genes, including glutamate cysteine ligase catalytic subunit(GCLC) and glutamate cysteine ligase modifier subunit (GCLM), and thereby promote GSH synthesis and the expression of related antioxidases. This study might shed light on the effects of curcumin on the prevention and alleviation of liver diseases in fish.

Interference of goethite in the effects of glyphosate and Roundup® on ZFL cell line

Goethite (α-FeOOH) brings important perspectives in environmental remediation, as, due to its physicochemical properties, this iron oxide can adsorb a wide variety of compounds, including glyphosate. This study aimed to evaluate the effects of goethite nanoparticles (NPs), glyphosate (Gly), Roundup® (Rd), and co-exposures (Gly + NPs and Rd + NPs) on zebrafish liver cell line (ZFL). ZFL cells were exposed to NPs (1, 10, and 100 mg L-1), Gly (3.6 mg L-1), Rd (10 mg L-1), and co-exposures (Gly + NPs and Rd + NPs), or only to saline for 1, 6, and 12 h. Cell viability was assessed by Trypan blue, MTT, and neutral red assays. The generation of reactive oxygen species and total antioxidant capacity were also determined, while genotoxicity was quantified by the comet assay. Both NPs and Rd in isolation produced cytotoxic effects at 6 h and genotoxic effects at 1 and 6 h. Rd + NPs resulted in synergistic effects, intensifying the toxicity. Cells exposed to Gly did not present toxic effects and Gly + NPs resulted in the suppression of toxic effects observed for NPs. The presence of other components in Roundup® seems to favor its toxicity compared to the active ingredient. In conclusion, according to the in vitro model, the concentrations used were not safe for the ZFL lineage.

Carbon Nanotubes Modulate Activity of Cytotoxic Compounds via a Trojan Horse Mechanism

Carbon nanotubes (CNTs) are an emerging drug delivery system, but their success is thwarted by potential toxicity concerns. In vitro and in vivo studies imply toxic potential of CNTs, but their potential to influence toxicity of coadministered compounds still remains elusive. Therefore, the present study was conducted to determine the effect of multiwalled CNTs (MWCNTs) on the toxicity of cytotoxic compounds in macrophage (RAW 264.7), lung epithelial (A549), and breast cancer (MCF-7) cell lines. The results suggest that hydrophilicity/lipophilicity of the compounds is a critical parameter. The correlation between log P and enhanced cytotoxic activity followed an inverted U-shaped curve and log P close to 1 exhibited the highest increase in cytotoxicity. Further, the increase in cytotoxicity of drug/MWCNT combinations was proportional to the degree of cellular uptake of MWCNTs. A mathematical model was developed and validated with a test set of compounds. These results suggest that MWCNTs act as a "Trojan horse" for increased intracellular delivery of drugs resulting in enhanced cytotoxic activity.

Monobutyl phthalate (MBP) can dysregulate the antioxidant system and induce apoptosis of zebrafish liver

In this paper, the acute toxicity of monobutyl phthalate (MBP), the main hydrolysis product of dibutyl phthalate, on adult zebrafish liver antioxidant system was studied. Compared the toxicity effect of MBP and DBP by histopathology and apoptosis experiments, we speculated that the toxic effects of DBP on animals may be caused by its metabolite MBP. The results indicated that the antioxidant Nrf2-Keap1 pathway was insufficient to resist MBP-induced hepatotoxicity and led to an imbalance of membrane ion homeostasis and liver damage. Decreased cell viability, significant tissue lesions and early hepatocyte apoptosis were observed in the zebrafish liver in MBP exposure at high concentration (10 mg/L). The activities of antioxidant enzymes and ATPases in zebrafish liver were inhibited with increased malondialdehyde (MDA) content and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. Integrated biomarker response (IBR) calculation results indicated that MBP mainly inhibited catalase (CAT) activity. Simultaneously, the expression of antioxidant-related genes (SOD, CAT, GPx, Nrf2, HO-1) was down-regulated, while apoptosis-related genes (p53, bax, cas3) were significantly up-regulated.

Characteristic synergistic cytotoxic effects toward cells in graphene oxide dressing with cadmium and copper ions

The increasing applications of graphene oxide (GO) in bio-medicine, environment and other fields enhance the exposure possibility of human beings to GO. Studies have been performed to address the in vitro toxicity of GO; however, little information on the in vivo biological consequence of GO with other common disasters is available, especially when cells are co-exposed to GO and common metal ions. To explore the influence and possible mechanisms of such co-exposure scenarios, a series of tests of cell viability, membrane integrity, reactive oxygen species (ROS), cell morphology, and Cd²⁺ distribution, were conducted. The results showed that the synergistic toxic mechanisms of GO and Cd²⁺, initiated from the adhesion of GO on HeLa cells, and followed by the recruitment of Cd²⁺ ions around the cell membrane, impaired the membrane integrity, morphology and adhesion capability, and triggered cell toxicity. The synergistic toxic mechanism of GO and Cu²⁺ mainly correlated to ROS, while no obvious relationship with membrane integrity was observed. The findings are envisaged to facilitate the application of GO in biology and related fields.

Multi-walled carbon nanotubes upregulate mitochondrial gene expression and trigger mitochondrial dysfunction in primary human bronchial epithelial cells

Nanomaterials are a relatively new class of materials that acquire novel properties based on their reduced size. While these materials have widespread use in consumer products and industrial applications, the potential health risks associated with exposure to them remain to be fully characterized. Carbon nanotubes are among the most widely used nanomaterials and have high potential for human exposure by inhalation. These nanomaterials are known to penetrate the cell membrane and interact with intracellular molecules, resulting in a multitude of documented effects, including oxidative stress, genotoxicity, impaired metabolism, and apoptosis. While the capacity for carbon nanotubes to damage nuclear DNA has been established, the effect of exposure on mitochondrial DNA (mtDNA) is relatively unexplored. In this study, we investigated the potential of multi-walled carbon nanotubes (MWCNTs) to impair mitochondrial gene expression and function in human bronchial epithelial cells (BECs). Primary BECs were exposed to sub-cytotoxic doses (up to 3 μg/ml) of MWCNTs for 5 d and assessed for changes in expression of all mitochondrial protein-coding genes, heteroplasmies, and insertion/deletion mutations (indels). Exposed cells were also measured for cytotoxicity, metabolic function, mitochondrial abundance, and mitophagy. We found that MWCNTs upregulated mitochondrial gene expression, while significantly decreasing oxygen consumption rate and mitochondrial abundance. Confocal microscopy revealed induction of mitophagy by 2 hours of exposure. Mitochondrial DNA heteroplasmy and insertion/deletion mutations were not significantly affected by any treatment. We conclude that carbon nanotubes cause mitochondrial dysfunction that leads to mitophagy in exposed BECs via a mechanism unrelated to its reported genotoxicity.

Aggregation of oxidized multi-walled carbon nanotubes: Interplay of nanomaterial surface O-functional groups and solution chemistry factors

The fast-growing production and application of carbon nanotube (CNT) materials in a variety of industrial products inevitably lead to their release to wastewater and surface water. CNT would experience oxidization in wastewater treatment plant due to the presence of large amount of disinfectants, such as H₂O₂ and O₃, which in turn affects the environmental fates and risks of CNT. In this study, oxidized CNT materials (O-CNTs) were prepared by treating CNT with H₂O₂/UV and O₃ (denoting as H₂O₂-CNT and O₃-CNT, respectively). A variety of characterizations indicated that oxygen containing groups were generated on CNT surface upon the oxidation, and the O/C ratio increased in the order of pristine CNT < H₂O₂-CNT < O₃-CNT. In the presence of Na⁺, K⁺ and Mg²⁺, the O-CNTs displayed better colloidal stability than the pristine CNT, and the stability increased with the oxidation degree (indicated by O/C ratio). This could be explained by the more negative surface charge and stronger hydrophilicity of the O-CNTs. Unexpectedly, in the presence of Ca²⁺, the most oxidized O₃-CNT exhibited the poorest colloidal stability. The abundant carboxyl groups in O₃-CNT provided effective binding sites for cation bridging effect through Ca²⁺ and led to stronger aggregation. Increasing pH was more favorable to disperse CNTs (both O-CNT and pristine CNT) in the presence of Na⁺, but much less effective in inhibiting the aggregation of O₃-CNT in presence of Ca²⁺. This could be explained by the stronger cation bridging effect due to enhanced deprotonation the -COOH groups at higher pH conditions. The calculated Hamaker constants of the CNTs decreased with the oxidation degree, implying that there was lower van der Waals force between the O-CNTs. The Derjaguin-Landau-Verwey-Overbeek (DLVO) calculation confirmed that O-CNTs had to overcome higher energy barrier and thus showed better colloidal stability than the pristine CNT in the presence of Na⁺.

Interaction of graphene oxide with cell culture medium: Evaluating the fetal bovine serum protein corona formation towards in vitro nanotoxicity assessment and nanobiointeractions

The interaction of single-layer graphene oxide (SLGO) and multi-layered graphene oxide (MLGO) with a cell culture medium (i.e. DMEM) was studied by evaluating fetal bovine serum (FBS) protein corona formation towards in vitro nanotoxicity assessment and nanobiointeractions. SLGO and MLGO exhibited different colloidal behavior in the culture medium, which was visualized by cryogenic transmission electron microscopy in situ analysis. Exploring proteomics and bioinformatics tools, 394 and 290 proteins were identified on the SLGO and MLGO hard corona compositions, respectively. From this amount, 115 proteins were exclusively detected on the SLGO and merely 11 on MLGO. SLGO enriched FBS proteins involved in metabolic processes and signal transduction, while MLGO enriched proteins involved in cellular development/structure, and lipid transport/metabolic processes. Such a distinct corona profile is due to differences on surface chemistry, aggregation behavior and the surface area of GO materials. Hydrophilic interactions were found to play a greater role in protein adsorption by MLGO than SLGO. Our results point out implications for in vitro studies of graphene oxide materials concerning the effective dose delivered to cells and corona bioactivity. Finally, we demonstrated the importance of integrating conventional and modern techniques thoroughly to understand the GO-FBS complexes towards more precise, reliable and advanced in vitro nanotoxicity assessment.