Potential toxicity of Graphene (Oxide) quantum dots to human intestinal fatty acid binding protein (HIFABP) via obstructing the protein's openings.

Graphene quantum dots (GQDs) have garnered significant attention across numerous fields due to their ultrasmall size and exceptional properties. However, their extensive applications may lead to environmental exposure and subsequent uptake by humans. Yet, conflicting reports exist regarding the potential toxicity of GQDs based on experimental investigations. Therefore, a comprehensive understanding of GQD biosafety requires further microscopic and molecular-level investigations. In this study, we employed molecular dynamics (MD) simulations to explore the interactions between GQDs and graphene oxide quantum dots (GOQDs) with a protein model, the human intestinal fatty acid binding protein (HIFABP), that plays a crucial role in mediating the carrier of fatty acids in the intestine. Our MD simulation results reveal that GQDs can be adsorbed on the opening of HIFABP, which serves as an entrance for the fatty acid molecules into the protein's interior cavity. This adsorption has the potential to obstruct the opening of HIFABP, leading to the loss of its normal biological function and ultimately resulting in toxicity. The adsorption of GQDs is driven by a combination of van der Waals (vdW), π-π stacking, cation-π, and hydrophobic interactions. Similarly, GOQDs also exhibit the ability to block the opening of HIFABP, thereby potentially causing toxicity. The blockage of GOQDs to HIFABP is guided by a combination of vdW, Coulomb, π-π stacking, and hydrophobic interactions. These findings not only highlight the potential harmful effects of GQDs on HIFABP but also elucidate the underlying molecular mechanism, which provides crucial insights into GQD toxicology.

GO promotes detoxification of nicosulfuron in sweet corn by enhancing photosynthesis, chlorophyll fluorescence parameters, and antioxidant enzyme activity.

Although graphene oxide (GO) has extensive recognized application prospects in slow-release fertilizer, plant pest control, and plant growth regulation, the incorporation of GO into nano herbicides is still in its early stages of development. This study selected a pair of sweet corn sister lines, nicosulfuron (NIF)-resistant HK301 and NIF-sensitive HK320, and sprayed them both with 80 mg kg-1 of GO-NIF, with clean water as a control, to study the effect of GO-NIF on sweet corn seedling growth, photosynthesis, chlorophyll fluorescence, and antioxidant system enzyme activity. Compared to spraying water and GO alone, spraying GO-NIF was able to effectively reduce the toxic effect of NIF on sweet corn seedlings. Compared with NIF treatment, 10 days after of spraying GO-NIF, the net photosynthetic rate (A), stomatal conductance (Gs), transpiration rate (E), photosystem II photochemical maximum quantum yield (Fv/Fm), photochemical quenching coefficient (qP), and photosynthetic electron transfer rate (ETR) of GO-NIF treatment were significantly increased by 328.31%, 132.44%, 574.39%, 73.53%, 152.41%, and 140.72%, respectively, compared to HK320. Compared to the imbalance of redox reactions continuously induced by NIF in HK320, GO-NIF effectively alleviated the observed oxidative pressure. Furthermore, compared to NIF treatment alone, GO-NIF treatment effectively increased the activities of superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in both lines, indicating GO induced resistance to the damage caused by NIF to sweet corn seedlings. This study will provides an empirical basis for understanding the detoxification promoting effect of GO in NIF and analyzing the mechanism of GO induced allogeneic detoxification in cells.

Impacts of graphene oxide contamination on a food web: Threats to somatic and reproductive health of organisms.

Contamination of aquatic food webs with nanomaterials poses a significant ecological and human health challenge. Ingestion of nanomaterials alongside food disrupts digestion and impairs physiological processes, with potential consequences for organism fitness and survival. Complex interactions between nanomaterials and biota further exacerbate the issue, influencing life-history strategies and ecosystem dynamics. Accumulation of nanomaterials within autotrophic and detritus-based food webs raises concerns about biomagnification, especially for top-level consumers and seafood-dependent human populations. Understanding the extent and impact of nanomaterial contamination on aquatic biota is crucial for effective mitigation strategies. To address this challenge, we conducted a comprehensive study evaluating the bioaccumulation effects of graphene oxide (GO), a commonly used nanomaterial, within an aquatic food chain. Using a gnotobiotic freshwater microcosm, we investigated the effects of micro- and nano-scale GO sheets on key organisms: green algae (Chlorella vulgaris), brine shrimp (Artemia salina), and zebrafish (Danio rerio). Two feeding regimes, direct ingestion and trophic transfer, were employed to assess GO uptake and transfer within the food web. Direct exposure involved individual organisms being exposed to either nano- or micro-scale GO sheets, while trophic transfer involved a sequential exposure pathway: algae exposed to GO sheets, artemias feeding on the algae, and zebrafish consuming the artemias. Our study provides critical insights into nanomaterial contamination in aquatic ecosystems. Physicochemical properties of GO sheets, including ζ-potential and dispersion, were influenced by salt culture media, resulting in aggregation under salt conditions. Microscopic imaging confirmed the bioaccumulation of GO sheets within organisms, indicating prolonged exposure and potential long-term effects. Notably, biodistribution analysis in zebrafish demonstrated the penetration of nano-sized GO into the intestinal wall, signifying direct interaction with vital organs. Exposure to GO resulted in increased zebrafish mortality and impaired reproductive performance, particularly through trophic transfer. These findings emphasize the urgent need to address nanomaterial contamination in aquatic food webs to protect ecosystem components and human consumers. Our study highlights the importance of developing effective mitigation strategies to preserve the integrity of aquatic ecosystems, ensure resource sustainability, and safeguard human well-being. In conclusion, our study provides crucial insights into the impact of nanomaterial pollution on aquatic biota. By recognizing the challenges posed by nanomaterial contamination and implementing targeted interventions, we can mitigate the adverse effects, preserving the integrity of aquatic ecosystems and safeguarding human health.

Potential toxicity of carbonaceous nanomaterials on aquatic organisms and their alleviation strategies: A review.

Carbonaceous nanomaterials (CNMs) are widely used in electronics, biomedicine, agriculture, environmental remediation, and catalysis due to their excellent biocompatibility, high reactivity, and high specific surface area. However, the extensive applications of CNMs cause their inevitable release into water, which may result in toxic effects on the aquatic ecological environment and organisms. CNMs can cause lipid peroxidation damage and neurotoxicity in aquatic organisms, affecting embryo hatching and larval morphology. The effects of CNMs on aquatic organisms vary depending on their structures and physicochemical properties, as well as the species, age, and tolerance of the tested organisms. The above uncertainties have increased the difficulty of exploring the impact of carbonaceous nanomaterials on the toxicity of aquatic organisms to a certain extent. Solving these issues is of great significance and reference value for promoting the research and safe utilization of carbon nanomaterials. Therefore, a systematic review of the effects of potential toxicity of carbonaceous nanomaterials on aquatic organisms and their alleviation strategies is needed. This paper firstly summarizes the toxic effects of commonly used CNMs (i.e., carbon nanotubes, graphene, and fullerene) on different aquatic organisms, which include developmental toxicity, behavioral and metabolic toxicity, reproductive toxicity, and organ toxicity. Then the main mechanisms of CNMs to aquatic organisms are further explored, and the methods to reduce the toxicity of CNMs are also summarized. Finally, the current challenges and future perspectives for studying CNM toxicity to aquatic organisms are proposed.

Chronic environmental level exposure to perfluorooctane sulfonate overshadows graphene oxide to induce apoptosis through activation of the ROS-p53-caspase pathway in marine medaka Oryzias melastigma.

The widespread occurrence of perfluorooctane sulfonate (PFOS) and the mass production and application of graphene oxide (GO) lead to their inevitable release and interaction in the environment, which may enhance associated toxic impacts on aquatic organisms. This study elucidates the induction of apoptosis by 60-day chronic single and mixture exposures to environmentally relevant levels of PFOS (0.5 µg/L and 5 µg/L) and GO (1 mg/L) in adult marine medaka Oryzias melastigma. Results showed a significant increase (p < 0.05) in reactive oxygen species (ROS) levels, the apoptotic positive rate in livers, and activities of caspases 3, 8, and 9 in all treated groups compared to the control. PFOS individual and PFOS-GO combined exposures significantly impacted fish growth, upregulated expressions of six apoptosis-related genes including p53, apaf1, il1b, tnfa, bcl2l1, bax, as well as enriched cell cycle and p53 signaling pathways (transcriptomic analysis) related to apoptosis compared to control group. Besides higher ROS production, GO also had a higher binding affinity to proteins than PFOS, especially to caspase 8 as revealed by molecular docking. Overall, PFOS induced ROS-p53-caspase apoptosis pathway through multi-gene regulation during single or mixture exposure, while GO single exposure induced apoptosis through tissue damage and ROS-caspase pathway activation and direct docking with caspase 8 to activate the caspase cascade. Under co-exposure, the PFOS-induced apoptotic pathway overshadowed the GO-induced pathway, due to competition for limited active sites on caspases. These findings will contribute to a better understanding of the apoptosis mechanism and ecological risks of nanomaterials and per- and polyfluoroalkyl substances in marine ecosystems.

Human Multi-Lineage Liver Organoid Model Reveals Impairment of CYP3A4 Expression upon Repeated Exposure to Graphene Oxide.

Three-dimensional hepatic cell cultures can provide an important advancement in the toxicity assessment of nanomaterials with respect to 2D models. Here, we describe liver organoids (LOs) obtained by assembling multiple cell lineages in a fixed ratio 1:1:0.2. These are upcyte® human hepatocytes, UHHs, upcyte® liver sinusoidal endothelial cells, LSECs, and human bone marrow-derived mesenchymal stromal cells, hbmMSCs. The structural and functional analyses indicated that LOs reached size stability upon ca. 10 days of cultivation (organoid maturation), showing a surface area of approximately 10 mm2 and the hepatic cellular lineages, UHHs and LSECs, arranged to form both primitive biliary networks and sinusoid structures, alike in vivo. LOs did not show signs of cellular apoptosis, senescence, or alteration of hepatocellular functions (e.g., dis-regulation of CYP3A4 or aberrant production of Albumin) for the entire culture period (19 days since organoid maturation). After that, LOs were repeatedly exposed for 19 days to a single or repeated dose of graphene oxide (GO: 2-40 µg/mL). We observed that the treatment did not induce any macroscopic signs of tissue damage, apoptosis activation, and alteration of cell viability. However, in the repeated dose regimen, we observed a down-regulation of CYP3A4 gene expression. Notably, these findings are in line with recent in vivo data, which report a similar impact on CYP3A4 when mice were repeatedly exposed to GO. Taken together, these findings warn of the potential detrimental effects of GO in real-life exposure (e.g., occupational scenario), where its progressive accumulation is likely expected. More in general, this study highlights that LOs formed by many cell lineages can enable repeated exposure regimens (suitable to mimic accumulation); thus, they can be suitably considered alternative or complementary in vitro systems to animal models.

Studies of the interaction of graphene oxide (GO) with endothelial cells under static and flow conditions.

Graphene oxide, due to its unique properties, has several potential applications in biomedicine, especially as a drug carrier. Despite emerging studies on its cytotoxicity and uptake into cells, there are still gaps in knowledge on this area. When analyzing the internalization of nanomaterials, many different factors must be considered, including particle size, surface modifications, and interactions with biological fluids that can change their properties. In the present study, we evaluated the effects of graphene oxide fractions in different sizes and samples incubated in human serum on endothelial cells (HUVECs). In addition, the study was conducted in both macroscale and microscale using Cell-on-a-Chip technology to better replicate in vivo conditions. Our findings indicate that samples incubated with serum reduce the efficiency of fraction uptake into cells. It was also observed that the uptake efficiency of graphene oxide (GO) fractions is higher in the microscale (in more real to in vivo environment) compared to the macroscale. Our research has shown that in order to determine the correct interaction of new materials into mammalian cells, it is necessary to take into account many different biochemical and physical factors.

TRPA1 nanovesicle-conjugated receptonics for rapid biocide screening.

Although biocides are important materials in modern society and help protect human health and the environment, increasing exposure to combined biocides can cause severe side effects in the human body, such as lung fibrosis. In this study, we developed a receptonics system to screen for biocides in combined household chemical products based on biocides. The system contains transient receptor potential ankyrin 1 (TRPA1) nanovesicles (NVs) to sense biocides based on pain receptors and a side-gated field-effect transistor (SGFET) using a single-layer graphene (SLG) micropattern channel. The binding affinities between the TRPA1 receptor and the various biocides were estimated by performing biosimulation and using a calcium ion (Ca2+) assay, and the sensitivity of the system was compared with that of TRPA1 NV receptonics systems. Based on the results of the TRPA1 NV receptonics system, the antagonistic and potentiation effects of combined biocides and household chemical products depended on the concentration. Finally, the TRPA1 NV receptonics system was applied to screen for biocides in real products, and its performance was successful. Based on these results, the TRPA1 NV receptonics system can be utilized to perform risk evaluations and identify biocides in a simple and rapid manner.

Involvement of ahr-dependent Cyp1a detoxification activity, oxidative stress and inflammatory regulation in response to graphene oxide exposure in rainbow trout (Oncorhynchus mykiss).

Graphene oxide (GO) is a very attractive material for use in a vast number of applications. However, before its widespread use, it is important to consider potential issues related to environmental safety to support its safe application. The aim of this study was to investigate effects on fish (rainbow trout) following GO exposure. Using both an in vitro approach with the RTL W1 rainbow trout liver cell line, and in vivo exposures, following OECD TG 203, disturbances at the cellular level as well as in the gills and liver tissue of juvenile trout were assessed. In RTL W1 cells, a time and concentration-dependent loss in cell viability, specifically plasma membrane integrity and lysosomal function, was observed after 96 h of exposure to GO at concentrations ≥18.75 mg/L. Additionally, increased reactive oxygen species (ROS) levels were evidenced at concentrations ≥18.75 mg/L, and an enhancement of metabolic activity was noted with concentrations ≥4.68 mg/L. In vivo exposures to GO did not provoke mortality in rainbow trout juveniles following 96 h exposure but led to histological alterations in gills and liver tissues, induction of enzymatic detoxification activities in the liver, as well as aryl hydrocarbon receptor (ahr)-cytochrome P450 1a (cyp1a) gene expression downregulation, and upregulation of pro-inflammatory cytokines il1b and il8 at GO concentrations ≥9.89 mg/L.

In silico mechanistic insights of ecofriendly synthesized AgNPs, SeNPs, rGO and Ag&SeNPs@rGONM's for biological applications and its toxicity evaluation using Artemia salina.

The present study focused on Rosmarinus officinalis Linn. leaves extract (ROE) mediated synthesis of silver nanoparticles (AgNPs), selenium nanoparticles (SeNPs), reduced graphene oxide (rGO) and silver and selenium nanoparticles decorated on rGO nanomaterials (Ag&SeNPs@rGONM's) for its antibacterial and antifungal in silico mechanistic insight applications. In addition, the toxicity of the synthesized nanomaterials was evaluated using Artemia salina. The formation of AgNPs, SeNPs, rGO and Ag&SeNPs@rGONM's was completed within 1.0, 140, 120 and 144 h, respectively. Various optical and microscopic examinations were evident in the nanomaterial's synthesis. Further, the average size and stability of the synthesized nanomaterials were conformed through dynamic light scattering (DLS) and zeta potential analyzer, respectively. The synthesized Ag&SeNPs@rGONM's were pronounced promising results against Gram-negative bacteria of Escherichia coli and the results achieved from the route of entry and action, reactive oxygen species (ROS), and antioxidant nature of nanoparticles were evidence of its properties. Computational studies further supported these findings, indicating much of the phytochemicals present in ROE well interact with the bacterial surface proteins. Similarly, the synthesized Ag&SeNPs@rGONM's was effective against Fusarium graminearum and Alternaria alternata in a dose dependent manner than its original nanomaterials. In addition, the docking study also confirmed that rosmarinic acid and caffeic acid prominently interacted with the fungal proteins. Interestingly, Ag&SeNPs@rGONM's pronounced less toxic effect compared to AgNPs and SeNPs against Artemia salina, which shows its biocompatibility.

Graphene powders as new contact nanopesticides: Revealing key parameters on their insecticidal activity for stored product insects.

The overuse and reliance on pesticides has caused insects to develop resistance with global concerns. To address this problem extensive research is directed to find new and sustainable alternatives using chemical-free and resistance-free solutions for pest control. This paper presents a comprehensive investigation of the insecticidal properties of several types of industrially produced graphene powder materials such as graphene and graphene oxide (GO) with micro- and nano size and different structural and chemical properties as new contact nanopesticides against three major stored grain insects: the rice weevil Sitophilus oryzae (L.), the lesser grain borer, Rhyzopertha dominica (F.)˙ and the larger grain borer, Prostephanus truncatus Horn. Bioassays were performed using different concentrations, i.e., 0, 100, 500 and 1000 ppm of graphene powders on the mortality of selected adult insects recorded after 3, 7, 14, and 21 days of exposure and progeny production after 65 days. Results showed that graphene oxide (GO) has no insecticidal efficacy while graphene powders with nano-size particles showed significantly enhanced insecticidal performance compared to micron-size graphene powders. The observed insecticidal effects are explained by the higher probability that nano-sized graphene particles adhere on the insect body compared to large particles. The mortality is proposed as the result of physical mode of action of attached graphene nanoparticles causing stronger interruption of the protective cuticle layer, gas respiratory functions and faster mortality. The findings of this study revealed that it is important to select graphene materials with optimal structural and interfacial properties to achieve the highest insecticidal performance in potential development of a new generation of sustainable insecticides.

A novel "cells-on-particles" cytotoxicity testing platform in vitro: design, characterization, and validation against engineered nanoparticle aerosol.

The presented research introduces the "Cells-on-Particles" integrated aerosol sampling and cytotoxicity testing in vitro platform, which allows for the direct assessment of the biological effects of captured aerosol particles on a selected cell type without the need for extraction or resuspension steps. By utilizing particles with unaltered chemical and physical properties, the method enables simple and fast screening of biological effects on specific cell types, making it a promising tool for assessing the cytotoxicity of particulate matter in ambient and occupational air. Platforms fabricated from cellulose acetate (CA) and poly[ε]caprolactone (PCL) were proven to be biocompatible and promoted the attachment and growth of the human bronchial epithelial cell line BEAS-2B. The PCL platforms were exposed to simulated occupational aerosols of silver, copper, and graphene oxide nanoparticles. Each nanoparticle type exhibited different and dose-dependent cytotoxic effects on cells, evidenced by reduced cell viability and distinct, particle type-dependent gene expression patterns. Notably, copper nanoparticles were identified as the most cytotoxic, and graphene oxide the least. Comparing the "Cells-on-Particles" and submerged exposure ("Particles-on-Cells") testing strategies, BEAS-2B cells responded to selected nanoparticles in a comparable manner, suggesting the developed testing system could be proposed for further evaluation with more complex environmental aerosols. Despite limitations, including particle agglomeration and the need for more replicates to address variability, the "Cells-on-Particles" platform enables effective detection of toxicity induced by relatively low levels of nanoparticles, demonstrating good sensitivity and a relatively simpler procedure compared to standard 2D cell exposure methods.

Graphene Oxide Nanosheets Toxicity in Mice Is Dependent on Protein Corona Composition and Host Immunity.

Two-dimension graphene oxide (GO) nanosheets with high and low serum protein binding profiles (high/low hard-bound protein corona/HChigh/low) are used in this study as model materials and screening tools to investigate the underlying roles of the protein corona on nanomaterial toxicities in vivo. We proposed that the in vivo biocompatibility/nanotoxicity of GO is protein corona-dependent and host immunity-dependent. The hypothesis was tested by injecting HChigh/low GO nanosheets in immunocompetent ICR/CD1 and immunodeficient NOD-scid II2rγnull mice and performed histopathological and hematological evaluation studies on days 1 and 14 post-injection. HClow GO induced more severe acute lung injury compared to HChigh GO in both immunocompetent and immunodeficient mice, with the effect being particularly pronounced in immunocompetent animals. Additionally, HClow GO caused more significant liver injury in both types of mice, with immunodeficient mice being more susceptible to its hepatotoxic effects. Moreover, administration of HClow GO resulted in increased hematological toxicity and elevated levels of serum pro-inflammatory cytokines in immunocompromised and immunocompetent mice, respectively. Correlation studies were conducted to explore the impact of distinct protein corona compositions on resulting toxicities in both immunocompetent and immunodeficient mice. This facilitated the identification of consistent patterns, aligning with those observed in vitro, thus indicating a robust in vitro-in vivo correlation. This research will advance our comprehension of how hard corona proteins interact with immune cells, leading to toxicity, and will facilitate the development of improved immune-modulating nanomaterials for therapeutic purposes.

Soil application of graphitic carbon nitride nanosheets alleviate cadmium toxicity by altering subcellular distribution, chemical forms of cadmium and improving nitrogen availability in soybean (Glycine max L.).

Cadmium (Cd)-contamination impairs biological nitrogen fixation in legumes (BNF), threatening global food security. Innovative strategies to enhance BNF and improve plant resistance to Cd are therefore crucial. This study investigates the effects of graphitic carbon nitride nanosheets (g-C3N4 NSs) on soybean (Glycine max L.) in Cd contaminated soil, focusing on Cd distribution, chemical forms and nitrogen (N) fixation. Soybean plants were treated with 100 mg kg-1 g-C3N4 NSs, with or without 10 mg kg-1 Cd for 4 weeks. Soil addition of g-C3N4 NSs alleviated Cd toxicity and promote soybean growth via scavenging Cd-mediated oxidative stress and improving photosynthesis. Compared to Cd treatment, g-C3N4 NSs increased shoot and root dry weights under Cd toxicity by 49.5% and 63.4%, respectively. g-C3N4 NSs lowered Cd content by 35.7%-54.1%, redistributed Cd subcellularly by increasing its proportion in the cell wall and decreasing it in soluble fractions and organelles, and converted Cd from high-toxicity to low-toxicity forms. Additionally, g-C3N4 NSs improved the soil N cycle, stimulated nodulation, and increased the N-fixing capacity of nodules, thus increasing N content in shoots and roots by 12.4% and 43.2%, respectively. Mechanistic analysis revealed that g-C3N4 NSs mitigated Cd-induced loss of endogenous nitric oxide in nodules, restoring nodule development. This study highlights the potential of g-C3N4 NSs for remediating Cd-contaminated soil, reducing Cd accumulation, and enhancing plant growth and N fixation, offering new insights into the use of carbon nanomaterials for soil improvement and legume productivity under metal(loid)s stress.

Combination therapy enhances efficacy and overcomes toxicity of metal-based anti-diabetic agent.

BACKGROUND AND PURPOSE: Metal-based therapeutic agents are limited by the required concentration of metal-based agents. Hereby, we determined if combination with 17ß-oestradiol (E2) could reduce such levels and the therapy still be effective in type 2 diabetes mellitus (T2DM). EXPERIMENTAL APPROACH: The metal-based agent (vanadyl acetylacetonate [VAC])- 17ß-oestradiol (E2) combination is administered using the membrane-permeable graphene quantum dots (GQD), the vehicle, to form the active GQD-E2-VAC complexes, which was characterized by fluorescence spectra, infrared spectra and X-ray photoelectron spectroscopy. In db/db type 2 diabetic mice, the anti-diabetic effects of GQD-E2-VAC complexes were evaluated using blood glucose levels, oral glucose tolerance test (OGTT), serum insulin levels, homeostasis model assessment (homeostasis model assessment of insulin resistance [HOMA-IR] and homeostasis model assessment of ß-cell function [HOMA-ß]), histochemical assays and western blot. KEY RESULTS: In diabetic mice, GQD-E2-VAC complex had comprehensive anti-diabetic effects, including control of hyperglycaemia, improved insulin sensitivity, correction of hyperinsulinaemia and prevention of ß-cell loss. Co-regulation of thioredoxin interacting protein (TXNIP) activation by the combination of metal complex and 17ß-oestradiol contributed to the enhanced anti-diabetic effects. Furthermore, a potent mitochondrial protective antioxidant, coniferaldehyde, significantly potentiates the protective effects of GQD-E2-VAC complexes. CONCLUSION AND IMPLICATIONS: A metal complex-E2 combinatorial approach achieved simultaneously the protection of ß cells and insulin enhancement at an unprecedented low dose, similar to the daily intake of dietary metals in vitamin supplements. This study demonstrates the positive effects of combination and multi-modal therapies towards type 2 diabetes treatment.

Alleviative effects of C60 fullerene nanoparticles on arsenate transformation and toxicity to Danio rerio.

Widely-used C60 fullerene nanoparticles (C60) result in their release into the aquatic environment, which may affect the distribution and toxicity of pollutants such as arsenic (As), to aquatic organism. In this study, arsenate (As(V)) accumulation, speciation and subcellular distribution was determined in Danio rerio (zebrafish) intestine, head and muscle tissues in the presence of C60. Meanwhile we compared how single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), graphene oxide (GO) and graphene (GN) nanoparticles alter the behaviors of As(V). Results showed that C60 significantly inhibited As accumulation and toxicity in D. rerio, due to a decrease in total As and monomethylarsonic acid (MMA) and As(V) species concentrations, a lower relative distribution in the metal-sensitive fraction (MSF). It was attributed that C60 may coat As(V) ion channels and consequently, affect the secretion of digestive enzymes in the gut, favoring As excretion and inhibiting As methylation. Similarly, MWCNTs reduced the species concentration of MMA and As(V) in the intestines, low GSH (glutathione) contents in the intestine. Due to the disparity of other carbon-based nanomaterial morphologies, SWCNTs, GO and GN exhibited the various effects on the toxicity of As(V). In addition, the possible pathway of arsenobetaine (AsB) biosynthesis included migration from the intestine to muscle in D. rerio, with the precursor of AsB likely to be 2-dimethylarsinylacetic acid (DMAA). The results of this study suggest that C60 is beneficial for controlling As(V) pollution and reducing the impact of As(V) biogeochemical cycles throughout the ecosystem.

Unveiling Versatile Applications and Toxicity Considerations of Graphitic Carbon Nitride.

Metal-free, low-cost, organic photocatalytic graphitic carbon nitride (g-C3N4) has become a promising and impressive material in numerous scientific fields due to its unique physical and chemical properties. As a semiconductor with a suitable band gap of ~2.7 eV, g-C3N4 is an active photocatalytic material even after irradiation with visible light. However, information regarding the toxicity of g-C3N4 is not extensively documented and there is not a comprehensive understanding of its potential adverse effects on human health or the environment. In this context, the term "toxicity" can be perceived in both a positive and a negative light, depending on whether it serves as a benefit or poses a potential risk. This review shows the applications of g-C3N4 in sensorics, electrochemistry, photocatalysis, and biomedical approaches while pointing out the potential risks of its toxicity, especially in human and environmental health. Finally, the future perspective of g-C3N4 research is addressed, highlighting the need for a comprehensive understanding of the toxicity of this material to provide safe and effective applications in various fields.

Molecular characterization and transcriptional response of Lactuca sativa seedlings to co-exposure to graphene nanoplatelets and titanium dioxide nanoparticles.

The widespread use of nanomaterials in agriculture may introduce multiple engineered nanoparticles (ENPs) into the environment, posing a combined risk to crops. However, the precise molecular mechanisms explaining how plant tissues respond to mixtures of individual ENPs remain unclear, despite indications that their combined toxicity differs from the summed toxicity of the individual ENPs. Here, we used a variety of methods including physicochemical, biochemical, and transcriptional analyses to examine the combined effects of graphene nanoplatelets (GNPs) and titanium dioxide nanoparticles (TiO2 NPs) on hydroponically exposed lettuce (Lactuca sativa) seedlings. Results indicated that the presence of GNPs facilitated the accumulation of Ti as TiO2 NPs in the seedling roots. Combined exposure to GNPs and TiO2 NPs caused less severe oxidative damage in the roots compared to individual exposures. Yet, GNPs and TiO2 NPs alone and in combination did not cause oxidative damage in the shoots. RNA sequencing data showed that the mixture of GNPs and TiO2 NPs led to a higher number of differentially expressed genes (DEGs) in the seedlings compared to exposure to the individual ENPs. Moreover, the majority of the DEGs encoding superoxide dismutase displayed heightened expression levels in the seedlings exposed to the combination of GNPs and TiO2 NPs. The level of gene ontology (GO) enrichment in the seedlings exposed to the mixture of GNPs and TiO2 NPs was found to be greater than the level of GO enrichment observed after exposure to isolated GNPs or TiO2 NPs. Furthermore, the signaling pathways, specifically the "MAPK signaling pathway-plant" and "phenylpropanoid biosynthesis," exhibited a close association with oxidative stress. This study has provided valuable insights into the molecular mechanisms underlying plant resistance against multiple ENPs.

Microbial response to the chronic toxicity effect of graphene and graphene oxide nanomaterials within aerobic granular sludge systems.

Nanomaterials present in wastewater can pose a significant threat to aerobic granular sludge (AGS) systems. Herein, we found that compared to graphene nanomaterials (G-NMs), the long-term presence (95 days) of graphene oxide nanomaterials (GO-NMs) resulted in an increased proliferation of filamentous bacteria, poorer sedimentation performance (SVI30 of 74.1 mL/g) and smaller average particle size (1224.4 µm) of the AGS. In particular, the GO-NMs posed a more significant inhibitory effect to the total nitrogen removal efficiency of AGS (decreased by 14.3 %), especially for the denitrification process. The substantial accumulation of GO-NMs within the sludge matrix resulted in a higher level of reactive oxygen species in AGS compared to G-NMs, thereby inducing lactate dehydrogenase release, and enhancing superoxide oxidase and catalase activities. Such excessive oxidative stress could potentially result in a significant reduction in the activity of nitrogen metabolism enzymes (e.g., nitrate reductase and nitrite reductase) and the expression of key functional genes (e.g., nirS and nirK). Altogether, compared to G-NMs, prolonged exposure to GO-NMs had a more significant chronic toxicity effect on AGS systems. These findings implied that the presence of G-NMs and GO-NMs is a hidden danger to biological nitrogen removal and should receive more attention.

Microplastics with different functional groups modulate cellular and molecular mechanisms of reduced graphene oxide toxicity on the green microalga, Scenedesmus obliquus.

Even though microplastics (MPs) and graphene nanomaterials (GNMs) have demonstrated individual toxicity towards aquatic organisms, the knowledge gap lies in the lack of understanding regarding their combined toxicity. The difference between the combined toxicity of MPs and GNMs, in contrast to their individual toxicities, and furthermore, the elucidation of the mechanism of this combined toxicity are scientific questions that remain to be addressed. In this study, we examined the individual and combined toxicity of three polystyrene microplastics (MPs) with different functional groups-unmodified, carboxyl-modified (COOH-), and amino-modified (NH2-) MPs-in combination with reduced graphene oxide (RGO) on the freshwater microalga Scenedesmus obliquus. More importantly, we explored the cellular and molecular mechanisms responsible for the observed toxicity. The results indicated that the growth inhibition toxicity of RGO, either alone or in combination with the three MPs, against S. obliquus increased gradually with higher particle concentrations. The mitigating effect of MPs-NH2 on RGO-induced toxicity was most significant at a higher concentration, surpassing the effect of unmodified MPs. However, the MPs-COOH did not exhibit a substantial impact on the toxicity of RGO. Unmodified MPs and MPs-COOH aggravated the inhibition effects of RGO on the cell membrane integrity and oxidative stress-related biomarkers. Additionally, MPs-COOH exhibited a stronger inhibition effect on RGO-induced biomarkers compared to unmodified MPs. In contrast, the MPs-NH2 alleviated the inhibition effect of RGO on the biomarkers. Furthermore, the presence of differently functionalized MPs did not significantly affect RGO-induced oxidative stress and photosynthesis-related gene expression in S. obliquus, indicating a limited ability to modulate RGO genotoxicity at the molecular level. These findings can offer a more accurate understanding of the combined risks posed by these micro- and nano-materials and assist in designing more effective mitigation strategies.