Transcriptomic response and perturbation of toxicity pathways in zebrafish larvae after exposure to graphene quantum dots (GQDs)

Graphene oxide quantum dots (GOQDs) induce behavioral disorders via the disturbance of kynurenine pathway in zebrafish larvae

The emergence of graphene quantum dots (GQDs) expands the use of graphene derivatives in nanomedicine for its direct therapeutic applications in treating neurodegeneration, inflammation, metabolic dysfunction, and among others. Nevertheless, the biosafety assessment of GQDs remains deficient mostly because of the diverse surface characteristics of the nanoparticles. Our prior work demonstrated that GQDs can induce strong thigmotactic effects in zebrafish larvae over a wide range of concentrations, yet the underlying metabolic mechanisms remain largely unknown. In this study, we conducted a further exploration about graphene oxide quantum dots (GOQDs) for its potential neurotoxic effect on the behaviors of zebrafish larvae by combining neurotransmitter-targeted metabolomics with locomotion analysis. After continuous exposure to a concentration gradient of GOQDs (12.5 - 25 - 50 - 100 - 200 μg/mL) for 7 days, the thigmotactic activities of zebrafish larvae were observed across all exposure concentrations relative to the control group, while the basal locomotor activities, including distance moved and average velocity, were significantly changed by low concentrations of GOQDs. Targeted metabolomics was performed using zebrafish larvae at 7 days post-fertilization (dpf) that were exposed to 12.5 and 200 μg/mL, both of which were found to perturb the kynurenine pathway by regulating the levels of kynurenine, 3-hydroxyanthranilic acid (3-HAA), and quinolinic acid (QA). Furthermore, the thigmotaxis of larval fish induced by GOQDs during exposure could be counteracted by supplementing Ro-61-8048, an agonist acting on kynurenine 3-monooxygenase (KMO). In conclusion, our study establishes the involvement of the kynurenine pathway in GOQDs-induced thigmotaxis, which is independent of the transcriptional modulation of glutamate receptor families.

Quantum dots as advanced nanomaterials for food quality and safety applications: A comprehensive review and future perspectives

The importance of food quality and safety lies in ensuring the best product quality to meet consumer demands and public health. Advanced technologies play a crucial role in minimizing the risk of foodborne illnesses, contamination, drug residue, and other potential hazards in food. Significant materials and technological advancements have been made throughout the food supply chain. Among them, quantum dots (QDs), as a class of advanced nanomaterials with unique physicochemical properties, are progressively demonstrating their value in the field of food quality and safety. This review aims to explore cutting-edge research on the different applications of QDs in food quality and safety, including encapsulation of bioactive compounds, detection of food analytes, food preservation and packaging, and intelligent food freshness indicators. Moreover, the modification strategies and potential toxicities of diverse QDs are outlined, which can affect performance and hinder applications in the food industry. The findings suggested that QDs are mainly used in analyte detection and active/intelligent food packaging. Various food analytes can be detected using QD-based sensors, including heavy metal ions, pesticides, antibiotics, microorganisms, additives, and functional components. Moreover, QD incorporation aided in improving the antibacterial and antioxidant activities of film/coatings, resulting in extended shelf life for packaged food. Finally, the perspectives and critical challenges for the productivity, toxicity, and practical application of QDs are also summarized. By consolidating these essential aspects into this review, the way for developing high-performance QD-based nanomaterials is presented for researchers and food technologists to better capitalize upon this technology in food applications.

Potential adverse outcome pathway (AOP) of emamectin benzoate mediated cardiovascular toxicity in zebrafish larvae (Danio rerio)

Emamectin benzoate (EMB) is an efficient insecticide which widely used as an anthelmintic drug additive in aquaculture fish. However, its extensive use has resulted in widespread pollution in the aquatic environment. Previous studies have identified the potential developmental and neurotoxic effects of EMB, however, systematic studies pertaining to the cardiovascular toxic effects of EMB on fish are scarce. In this study, zebrafish embryos were exposed to EMB at concentrations of 0, 0.1, 0.25, 0.5, 1, 2, 4, and 8 mg/L for 3 days, aiming to investigate the cardiovascular toxic effects of EMB via examining morphology, cardiac function, and vascular development phenotypes. It revealed that EMB exposure led to marked deteriorated effects, including adverse effects on mortality, hatching rate, and general morphological traits, such as malformation, heart rate, body length, and eye area, in zebrafish embryos/larvae. Furthermore, EMB exposure resulted in abnormal cardiac function and vascular development, triggering neutrophil migration and aggregation toward the pericardial and dorsal vascular regions, and finalized apoptosis in the zebrafish heart region, these phenomena were further deciperred by the transcriptome analysis that the Toll-like receptor pathway, P53 pathway, and apoptotic pathway were significantly affected by EMB exposure. Moreover, the molecular docking and aspirin anti-inflammatory rescue assays indicated that TLR2 and TLR4 might be the potential targets of EMB. Taken together, our study provides preliminary evidence that EMB may induce apoptosis by affecting inflammatory signaling pathways and eventually lead to abnormal cardiovascular development in zebrafish. This study provides a simple toxicological AOP framework for safe pesticide use and management strategies.

Exploring the potential and safety of quantum dots in allergy diagnostics

Biomedical investigations in nanotherapeutics and nanomedicine have recently intensified in pursuit of new therapies with improved efficacy. Quantum dots (QDs) are promising nanomaterials that possess a wide array of advantageous properties, including electronic properties, optical properties, and engineered biocompatibility under physiological conditions. Due to these characteristics, QDs are mainly used for biomedical labeling and theranostic (therapeutic-diagnostic) agents. QDs can be functionalized with ligands to facilitate their interaction with the immune system, specific IgE, and effector cell receptors. However, undesirable side effects such as hypersensitivity and toxicity may occur, requiring further assessment. This review systematically summarizes the potential uses of QDs in the allergy field. An overview of the definition and development of QDs is provided, along with the applications of QDs in allergy studies, including the detection of allergen-specific IgE (sIgE), food allergens, and sIgE in cellular tests. The potential treatment of allergies with QDs is also described, highlighting the toxicity and biocompatibility of these nanodevices. Finally, we discuss the current findings on the immunotoxicity of QDs. Several favorable points regarding the use of QDs for allergy diagnosis and treatment are noted.

The Potentiating Effect of Graphene Oxide on the Arylhydrocarbon Receptor (AhR)-Cytochrome P4501A (Cyp1A) System Activated by Benzo(k)fluoranthene (BkF) in Rainbow Trout Cell Line

The increasing use of graphene oxide (GO) will result in its release into the environment; therefore, it is essential to determine its final fate and possible metabolism by organisms. The objective of this study was to assess the possible role of the aryl hydrocarbon receptor (AhR)-dependent cytochrome P4501A (Cyp1A) detoxification activities on the catabolism of GO. Our hypothesis is that GO cannot initially interact with the AhR, but that after an initial degradation caused by other mechanisms, small fractions of GO could activate the AhR, inducing Cyp1A. The environmental pollutant benzo(k)fluoranthene (BkF) was used for the initial activation of the AhR in the rainbow trout (Oncorhynchus mykiss) cell line RTL-W1. Pre-, co-, and post-exposure experiments with GO were performed and Cyp1A induction was monitored. The strong stimulation of Cyp1A observed in cells after exposure to GO, when BkF levels were not detected in the system, suggests a direct action of GO. The role of the AhR was confirmed by a blockage of the observed effects in co-treatment experiments with αNF (an AhR antagonist). These results suggest a possible role for the AhR and Cyp1A system in the cellular metabolism of GO and that GO could modulate the toxicity of environmental pollutants.

Lights and Dots toward Therapy-Carbon-Based Quantum Dots as New Agents for Photodynamic Therapy

The large number of deaths induced by carcinoma and infections indicates that the need for new, better, targeted therapy is higher than ever. Apart from classical treatments and medication, photodynamic therapy (PDT) is one of the possible approaches to cure these clinical conditions. This strategy offers several advantages, such as lower toxicity, selective treatment, faster recovery time, avoidance of systemic toxic effects, and others. Unfortunately, there is a small number of agents that are approved for usage in clinical PDT. Novel, efficient, biocompatible PDT agents are, thus, highly desired. One of the most promising candidates is represented by the broad family of carbon-based quantum dots, such as graphene quantum dots (GQDs), carbon quantum dots (CQDs), carbon nanodots (CNDs), and carbonized polymer dots (CPDs). In this review paper, these new smart nanomaterials are discussed as potential PDT agents, detailing their toxicity in the dark, and when they are exposed to light, as well as their effects on carcinoma and bacterial cells. The photoinduced effects of carbon-based quantum dots on bacteria and viruses are particularly interesting, since dots usually generate several highly toxic reactive oxygen species under blue light. These species are acting as bombs on pathogen cells, causing various devastating and toxic effects on those targets.

Graphene quantum dots (GQDs) induce thigmotactic effect in zebrafish larvae via modulating key genes and metabolites related to synaptic plasticity

Graphene quantum dots (GQDs) recently gain much attention for its medicinal values in treating diseases such as neurodegeneration and inflammations. However, owing to the high permeability of GQDs across the blood-brain barrier, whether its retention in the central nervous system (CNS) perturbs neurobehaviors remains less reported. In the study, the locomotion of zebrafish larvae (Danio rerio) was fully evaluated when administrated by two GQDs in a concentration gradient, respectively as reduced-GQDs (R-GQDs): 150, 300, 600, 1200, and 2400 g/L, and graphene oxide QDs (GOQDs): 60, 120, 240, 480, and 960 g/L. After exposure, the larvae were kept for locomotion analysis within one week's depuration. Substantial data showed that the basal locomotor activity of zebrafish larvae was not significantly changed by both two GQDs at low concentrations while weakened greatly with the increase of concentrations, and the total ATP levels of zebrafish larvae were also found to decrease significantly when exposed to the highest concentrations of GQDs. Next, the thigmotactic effect was observed to be remarkably induced in larvae by both two GQDs at any concentrations during exposure, and remained strong in larvae treated by high concentrations of R-GQDs after 7 days' depuration. To be noted, we found that GQDs affected the synaptic plasticity via downregulating the mRNA levels of NMDA and AMPA receptor family members as well as the total glutamine levels in zebrafish larvae. Together, our study presented robust data underlying the locomotor abnormalities aroused by GQDs in zebrafish larvae and indicated the potential adverse effects of GQDs on synaptic plasticity.

Progress on the toxicity of quantum dots to model organism-zebrafish

In vivo toxicological studies are currently necessary to analyze the probable dangers of quantum dots (QDs) to the environment and human safety, due to the fast expansion of QDs in a range of applications. Because of its high fecundity, cost-effectiveness, well-defined developmental phases, and optical transparency, zebrafish has long been considered the "gold standard" for biosafety assessment of chemical substances and pollutants. In this review, the advantages of using zebrafish in QD toxicity assessment were explored. Then, the target organ toxicities such as developmental toxicity, immunotoxicity, cardiovascular toxicity, neurotoxicity, and hepatotoxicity were summarized. The hazardous effects of different QDs, including cadmium-containing QDs like CdTe, CdSe, and CdSe/ZnS, as well as cadmium-free QDs like graphene QDs (GQDs), graphene oxide QDs (GOQDs), and others, were emphasized and described in detail, as well as the underlying mechanisms of QDs generating these effects. Furthermore, general physicochemical parameters determining QD-induced toxicity in zebrafish were introduced, such as chemical composition and surface coating/modification. The limitations and special concerns of using zebrafish in QD toxicity studies were also mentioned. Finally, we predicted that the utilization of high-throughput screening assays and omics, such as transcriptome sequencing, proteomics, and metabolomics will be popular topic in nanotoxicology.

An overview of quantum dots-induced immunotoxicity and the underlying mechanisms

Quantum dots (QDs) have bright luminescence and excellent photostability. New synthesis techniques and strategies also enhance QDs properties for specific applications. With the continuous expansion of the applications, QDs-mediated immunotoxicity has become a major concern. The immune system has been confirmed to be an important target organ of QDs and is sensitive to QDs. Herein, review immunotoxic effects caused by QDs and the underlying mechanisms. Firstly, QDs exposure-induced modulation in immune cell maturation and differentiation is summarized, especially pre-exposed dendritic cells (DCs) and their regulatory roles in adaptive immunity. Cytokines are usually recognized as biomarkers of immunotoxicity, therefore, variation of cytokines mediated by QDs is also highlighted. Moreover, the activation of the complement system induced by QDs is discussed. Accumulated results have suggested that QDs disrupt the immune response by regulating intracellular oxidative stress (reactive oxygen species) levels, autophagy formation, and expressions of pro-inflammatory mediators. Furthermore, several signalling pathways play a key role in the disruption. Finally, some difficulties worthy of further consideration are proposed. Because there are still challenges in biomedical and clinical applications, this review hopes to provide information that could be useful in exploring the mechanisms associated with QD-induced immunotoxicity.

Adverse reproductive and developmental consequences of quantum dots

Quantum dots (QDs), with a size of 1-10 nm, are luminescent semiconductor nanocrystals characterized by a shell-core structure. Notably, QDs have potential application in bioimaging owing to their higher fluorescence performance than conventional fluorescent dyes. To date, QDs has been widely used in photovoltaic devices, supercapacitors, electrocatalysis, photocatalysis. In recent years, scientists have focused on whether the use of QDs can interfere with the reproductive and developmental processes of organisms, resulting in serious population and community problems. In this study, we first analyze the possible reproductive and development toxicity of QDs. Next, we summarize the possible mechanisms underlying QDs' interference with reproduction and development, including oxidative stress, altered gametogenesis and fetal development gene expression, autophagy and apoptosis, and release of metal ions. Thereafter, we highlight some potential aspects that can be used to eliminate or reduce QDs toxicity. Based on QDs' unique physical and chemical properties, a comprehensive range of toxicity test data is urgently needed to build structure-activity relationship to quickly evaluate the ecological safety of each kind of QDs.

Photoluminescent carbon dots (PCDs) from sour apple: a biocompatible nanomaterial for preventing UHMWPE wear-particle induced osteolysis via modulating Chemerin/ChemR23 and SIRT1 signaling pathway and its bioimaging application

Photoluminescent nanomaterials have been widely employed in several biological applications both in vitro and in vivo. For the first time, we report a novel application of sour apple-derived photoluminescent carbon dots (PCDs) for reducing ultra-high molecular weight polyethylene (UHMWPE) wear particle-induced osteolysis using mouse calvarial model. Generally, aseptic prosthetic loosening seems to be a significant postoperative problem for artificial joints replacement, which is mainly contributed by UHMWPE-induced osteolysis. Hence, inhibiting osteoclastic bone-resorption could minimize UHMWPE-induced osteolysis for implant loosening. Prior to osteolysis studies, the prepared sour apple-derived PCDs were employed for bioimaging application. As expected, the prepared PCDs effectively inhibited the UHMWPE particle-induced osteoclastogenesis in vitro. The PCDs treatment effectively inhibited the UHMWPE-induced osteoclast differentiation, F-actin ring pattern, and bone resorption in vitro. Also, the PCDs reduced the UHMWPE-induced ROS stress as well as the expression level of pro-inflammatory cytokines, including TNF-α, IL-1, IL-6, and IL-8. Further, the qPCR and western blot results hypothesized that PCDs inhibited the UHMWPE wear particle-induced osteolysis through suppressing chemerin/ChemR23 signaling and NFATc1 pathway, along with upregulation of SIRT1 expression. Overall, these findings suggest that the synthesized PCDs could be a potential therapeutic material for minimizing UHMWPE particle-induced periprosthetic osteolysis to avoid postoperative complications.

Multi-walled carbon nanotubes inhibit potential detoxification of dioxin-mediated toxicity by blocking the nuclear translocation of aryl hydrocarbon receptor

Despite numerous studies on effects of environmental accumulation of nano-pollutants, the influence of nanoparticles on the biological perturbations of coexisting pollutants in the environment remained unknown. The present study aimed at elucidating the perturbations of six environmental nanoparticles on detoxification of dioxin-induced toxicity at cellular level. We discovered that there was no remarkable difference in the cell uptake and intracellular distributions of these six nanoparticles. However, they have different effects on the detoxification of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD). Multi-walled carbon nanotubes (MWCNTs) inhibited the translocation of aryl hydrocarbon receptor (AhR) from cytosol to the nucleus, leading to the downregulation of cytochrome P450 family 1 subfamily A member 1 (CYP1A1) and inhibition of detoxification function. These findings demonstrate that MWCNTs can impact the potential detoxification of dioxin-induced toxicity through modulating AhR signaling pathway. Co-exposures to MWCNTs and dioxin may cause even more toxicity than single exposure to dioxin or MWCNTs alone.

Recent advances in the hybridization of cellulose and carbon nanomaterials: Interactions, structural design, functional tailoring, and applications

Due to the good biocompatibility and flexibility of cellulose and the excellent optical, electronic, as well as mechanical properties of carbon nanomaterials (CNMs), cellulose/CNM hybrid materials have been widely synthesized and used in energy storage, sensors, adsorption, biomedicine, and many other fields. In this review, we present recent advances (2016-current) in the design, structural design, functional tailoring and various applications of cellulose/CNM hybrid materials. For this aim, first the interactions between cellulose and CNMs for promoting the formation of cellulose/CNM materials are analyzed, and then the hybridization between cellulose with various CNMs for tailoring the structures and functions of hybrid materials is introduced. Further, abundant applications of cellulose/CNM hybrid materials in various fields are presented and discussed. This comprehensive review will be helpful for readers to understand the functional design and facile synthesis of cellulose-based nanocomposites, and to promote the high-performance utilization and sustainability of biomass materials in the future.

Assessing the Environmental Effects Related to Quantum Dot Structure, Function, Synthesis and Exposure

Quantum dots (QDs) are engineered semiconductor nanocrystals with unique fluorescent, quantum confinement, and quantum yield properties, making them valuable in a range of commercial and consumer imaging, display, and lighting technologies. Production and usage of QDs are increasing, which increases the probability of these nanoparticles entering the environment at various phases of their life cycle. This review discusses the major types and applications of QDs, their potential environmental exposures, fates, and adverse effects on organisms. For most applications, release to the environment is mainly expected to occur during QD synthesis and end-product manufacturing since encapsulation of QDs in these devices prevents release during normal use or landfilling. In natural waters, the fate of QDs is controlled by water chemistry, light intensity, and the physicochemical properties of QDs. Research on the adverse effects of QDs primarily focuses on sublethal endpoints rather than acute toxicity, and the differences in toxicity between pristine and weathered nanoparticles are highlighted. A proposed oxidative stress adverse outcome pathway framework demonstrates the similarities among metallic and carbon-based QDs that induce reactive oxygen species formation leading to DNA damage, reduced growth, and impaired reproduction in several organisms. To accurately evaluate environmental risk, this review identifies critical data gaps in QD exposure and ecological effects, and provides recommendations for future research. Future QD regulation should emphasize exposure and sublethal effects of metal ions released as the nanoparticles weather under environmental conditions. To date, human exposure to QDs from the environment and resulting adverse effects has not been reported.

Transcriptome and in silico approaches provide new insights into the mechanism of male reproductive toxicity induced by chronic exposure to DEHP

Di-(2-ethylhexyl) phthalate (DEHP) can affect the male reproductive system in vertebrates, but the underlying molecular mechanism is still elusive. Therefore, in this study, we aimed to dig the in-depth mechanism of DEHP-induced reproductive toxicity on male zebrafish via testicular transcriptome using embryo exposed at the environmentally relevant concentration (ERC) of 100 μg/L for 111 days. Moreover, our results were further confirmed via in silico technique and bioassay experimental in vitro (cell lines) and in vivo (zebrafish). The results showed DEHP exposure could affect male spermatogenesis, altered gonad histology, and reduced egg fertilization rate. Transcriptome analysis identified 1879 significant differentially expressed genes enriched in the exposure group. Twenty-seven genes related to three pathways of reproduction behavior were further validated by qPCR. In silico molecular docking revealed that DEHP and its metabolism bind to the zebrafish progesterone receptor (Pgr), suggesting the potential disruption of DEHP to the normal Pgr signaling. To further validate it, a wild-type Pgr plasmid and its mutants on specific binding sites were constructed. The transfection and microinjection experiment demonstrated that these binding sites mutations of Pgr affected the expression levels of male reproductive toxicity. Taken together, our study provided new insight into the molecular mechanisms of male reproductive toxicity induced by DEHP, and Pgr may serve as an important target binding by DEHP pollution, which needs further study in the future.

Cytotoxicity and transcriptome changes triggered by CuInS2/ZnS quantum dots in human glial cells

As a newly developed cadmium-free quantum dot (QD), CuInS₂/ZnS has great application potential in many fields, but its biological safety has not been fully understood. In this study, the in vitro toxicity of CuInS₂/ZnS QDs on U87 human glioma cell line was explored. The cells were treated with different concentrations of QDs (12.5, 25, 50 and 100 μg/mL), and the uptake of QDs by the U87 cells was detected by fluorescence imaging and flow cytometry. The cell viability was observed by MTT assay, and the gene expression profile was analyzed by transcriptome sequencing. These results showed that QDs could enter the cells and mainly located in the cytoplasm. The uptake rate was over 90 % when the concentration of QDs reached 25 μg/mL. The cell viability (50 and 100 μg/mL) increased at 24 h (P < 0.05), but no significant difference after 48 h and 72 h treatment. The results of differential transcription showed that coding RNA accounted for the largest proportion (62.15 %), followed by long non-coding RNA (18.65 %). Total 220 genes were up-regulated and 1515 genes were down-regulated, and significantly altered gene functions included nucleosome, chromosome-DNA binding, and chromosome assembly. In conclusion, CuInS₂/ZnS QDs could enter U87 cells, did not reduce the cell viability, but would obviously alter the gene expression profile. These findings provide valuable information for a proper understanding of the toxicity risk of CuInS₂/ZnS QD and promote the rational utilization of QDs in the future.

Turning waste into wealth: facile and green synthesis of carbon nanodots from pollutants and applications to bioimaging

In an effort to turn waste into wealth, Reactive Red 2 (RR2), a common and refractory organic pollutant in industrial wastewater, has been employed for the first time as a precursor to synthesize carbon nanodots (CNDs) by a facile, green and low-cost route, without utilization of any strong acids or other oxidizers. The detailed characterizations have confirmed that the synthesized CNDs exhibit good water dispersibility, with a mean particle size of 2.43 nm and thickness of 1-3 layers. Importantly, the excellent fluorescence properties and much reduced biotoxicity of the CNDs confer its potential applications in further biological imaging, which has been successfully verified in both in vitro (cell culture) and in vivo (zebrafish) model systems. Thus, it is demonstrated that the synthesized CNDs exhibit nice biocompatibility and fluorescence properties for bioimaging. This work not only provides a novel economical and environmentally friendly approach in recycling a chemical pollutant, but also greatly promotes the potential application of CNDs in biological imaging.

Increased lipid peroxidation by graphene quantum dots induces ferroptosis in macrophages

Graphene quantum dots (GQDs) are an excellent tool for theranostics, and are widely used in nanomedical applications. The biosafety of GQDs has received abundant attention, but their latent toxicological mechanisms remain inadequately understood. To investigate the cellular and molecular mechanisms underlying graphene-mediated changes, quantitative proteomics and untargeted lipidomics were integrated. We discovered that glutathione peroxidase 4 as a key regulator of ferroptosis, was down-regulated at the protein level by GQDs. Lipidomics profiling with features of ferroptosis was identified in GQDs-treated RAW264.7 macrophages. Furthermore, GQDs exposure was associated with reduced levels of GSH and increased lipid peroxidation. Overexpression of GPX4 in RAW264.7 cells and pre-treatment of a ferroptosis inhibitor Ferrostatin-1 (Fer-1) not only suppressed cell death, but also alleviated lipid peroxidation. Taken together, our results indicated that GQDs exposure induced ferroptosis in RAW264.7 macrophages, and provided essential data for biosafety evaluations of GQDs.

Physiological and molecular responses in halotolerant Dunaliella salina exposed to molybdenum disulfide nanoparticles

Molybdenum disulfide nanoparticles (MoS₂ NPs) has emerged as the promising nanomaterial with a wide array of applications in the biomedical, industrial and environmental field. However, the potential effect of MoS₂ NPs on marine organisms has yet to be reported. In this study, the effect of MoS₂ NPs on the physiological index, subcellular morphology, transcriptomic profiles of the marine microalgae Dunaliella salina was investigated for the first time. exhibited "doping-like" effects on marine microalgae; Growth stimulation was 193.55%, and chlorophyll content increased 1.61-fold upon the addition of 50 μg/L MoS₂ NPs. Additionally, exposure to MoS₂ NPs significantly increased the protein and carbohydrate content by 2.03- and 1.56-fold, respectively. The antioxidant system was activated as well to eliminate the adverse influence of reactive oxygen species (ROS). Transcriptomic analysis revealed that genes involved in porphyrin synthesis, glycolysis/gluconeogenesis, tricarboxylic acid cycle and DNA replication were upregulated upon MoS₂ NPs exposure, which supports the mechanistic role of MoS₂ NPs in improving cellular growth and photosynthesis. The "doping-like" effects on marine algae suggest that the low concentration of MoS₂ NPs might change the rudimentary ecological composition in the ocean.

Identification of potential circRNA-miRNA-mRNA regulatory networks in response to graphene quantum dots in microglia by microarray analysis

Along with the increasing application of graphene quantum dots (GQDs) in the fields of biomedicine and neuroscience, it is important to assess the probably adverse effects of GQDs in the central nervous system (CNS) but their underlying toxic mechanisms is still unclear. In this study, we evaluate the molecular mechanisms associated with circular RNAs (circRNAs) of nitrogen-doped GQDs (N-GQDs) and amino-functionalized GQDs (A-GQDs) damaging the cell viability and cellular structure in microglia by an integrative analysis of RNA microarray. The differentially expressed circRNA (DEcircRNAs)-miRNA- differentially expressed mRNA (DEmRNAs) regulatory networks were conducted in BV2 microglial cells treated with 25 µg/mL N-GQDs, 100 µg/mL N-GQDs and 100 µg/mL A-GQDs. Based on that, the protein-coding genes in each ceRNA network were collected to do bio-functional analysis to evaluate signaling pathways that were indirectly mediated by circRNAs. Some pathways that could play indispensable roles in the neurotoxicity of N-GQDs or both two kinds of GQDs were found. Low-dosed N-GQDs exposure mainly induced inflammatory action in microglia, while high-dosed N-GQDs and A-GQDs exposure both affect olfactory transduction and GABAergic synapse. Meanwhile, several classical signaling pathways, including mTOR, ErbB and MAPK, could make diverse contributions to the neurotoxicity of both two kinds of GQDs. These circRNAs could be toxic biomarkers or protective targets in neurotoxicity of GQDs. More importantly, they emphasized the necessity of comprehensive analysis of latent molecular mechanisms through epigenetics approaches in biosafety assessment of graphene-based nanomaterials.

PEGylated CuInS2/ZnS quantum dots inhibit neurite outgrowth by downregulating the NGF/p75NTR/MAPK pathway

The widespread application of cadmium-free CuInS₂/ZnS QDs has raised great concern regarding their potential toxicity to humans. To date, toxicological data related to CuInS₂/ZnS QDs are scarce. Neurons play extraordinary roles in regulating the activities of organs and systems, and serious consequences occur when neurons are damaged. Currently, the potential toxicity of CuInS₂/ZnS QDs on neurons has not been fully elucidated. Here, we investigate the neurotoxicity of PEGylated CuInS₂/ZnS (CuInS₂/ZnS-PEG) QDs on neuron-like PC12 cells. We found that CuInS₂/ZnS-PEG QDs were taken up by PC12 cells, but at a concentration range from 0 to 100 μg/mL, they did not affect the survival rate of the PC12 cells. In addition, we found that CuInS₂/ZnS-PEG QDs significantly inhibited neurite outgrowth from and the differentiation of PC12 cells in the presence of NGF, while COOH-modified CuInS₂/ZnS QDs or free PEG did not have a similar effect. Further studies showed that CuInS₂/ZnS-PEG QDs obviously downregulated the expression of low-affinity NGF receptor (p75^NTR) and subsequently negatively regulated the downstream MAPK cascade by dephosphorylating ERK1/2 and AKT. Taken together, these results suggest that CuInS₂/ZnS-PEG QDs disturb NGF signal transduction from external stimuli to relevant internal signals, thus affecting normal biological processes such as neurite outgrowth and cell differentiation.

Physiological effect of colloidal carbon quantum dots on Bursaphelenchus xylophilus

Bursaphelenchus xylophilus (B. xylophilus) is a dangerous plant pest which could result in Pine Wild Disease (PWD).

Cytotoxicity and Immune Dysfunction of Dendritic Cells Caused by Graphene Oxide

Graphene, known as “black gold”, has important applications in various fields. In previous studies, it has been proved that graphene oxide (GO) which is a derivative of graphene has low toxicity. However, the immunotoxicity of GO has not been fully elucidated. In this work, we used DC2.4 cell line to investigate the in vitro immunotoxicity of two types of GO, mono-layer GO (mono-GO) and multi-layer GO (multi- GO). We found that mono-GO had less effect on cell viability than multi-GO, but both mono-GO and multi-GO significantly induced the generation of ROS in DC2.4 cells. Interestingly, mono-GO caused DC2.4 cells to aggregate, thus changed the cell morphology significantly. However, no similar influence occurred for multi-GO. In addition, the results showed that these two GOs obviously enhance the release of TNF-α by DC2.4 cells with and without LPS stimulation. GO did not affect the level of IL-6 released from DC2.4 cells, but multi-GO promoted the release of IL-6 while mono-GO inhibited the production of IL-6 when cells were in response to LPS stimulation. Whole-transcriptome sequencing analysis found some immune-related differentially expressed genes including H2-DMb1, Ncbp3, Oas2, Men1, Fas, Cd320, Cd244, and Tinagl1 which are engaged in the immune system process. These results suggested that both mono-GO and multi-GO are immunotoxic to DC2.4 cells, which provides important basis for subsequent biological and clinical medical applications.

Induction of ferroptosis in response to graphene quantum dots through mitochondrial oxidative stress in microglia

BACKGROUND

Graphene quantum dots (GQDs) provide a bright prospect in the biomedical application because they contain low-toxic compounds and promise imaging of deep tissues and tiny vascular structures. However, the biosafety of this novel QDs has not been thoroughly evaluated, especially in the central nervous system (CNS). The microarray analysis provides a hint that nitrogen-doped GQDs (N-GQDs) exposure could cause ferroptosis in microglia, which is a novel form of cell death dependent on iron overload and lipid peroxidation.

RESULTS

The cytosolic iron overload, glutathione (GSH) depletion, excessive reactive oxygen species (ROS) production and lipid peroxidation (LPO) were observed in microglial BV2 cells treated with N-GQDs, which indicated that N-GQDs could damage the iron metabolism and redox balance in microglia. The pre-treatments of a specific ferroptosis inhibitor Ferrostatin-1 (Fer-1) and an iron chelater Deferoxamine mesylate (DFO) not only inhibited cell death, but also alleviated iron overload, LPO and alternations in ferroptosis biomarkers in microglia, which were caused by N-GQDs. When assessing the potential mechanisms of N-GQDs causing ferroptosis in microglia, we found that the iron content, ROS generation and LPO level in mitochondria of BV2 cells all enhanced after N-GQDs exposure. When the antioxidant ability of mitochondria was increased by the pre-treatment of a mitochondria targeted ROS scavenger MitoTEMPO, the ferroptotic biological changes were effectively reversed in BV2 cells treated with N-GQDs, which indicated that the N-GQDs-induced ferroptosis in microglia could be attributed to the mitochondrial oxidative stress. Additionally, amino functionalized GQDs (A-GQDs) elicited milder redox imbalance in mitochondria and resulted in less ferroptotic effects than N-GQDs in microglia, which suggested a slight protection of amino group functionalization in GQDs causing ferroptosis.

CONCLUSION

N-GQDs exposure caused ferroptosis in microglia via inducing mitochondrial oxidative stress, and the ferroptotic effects induced by A-GQDs were milder than N-GQDs when the exposure method is same. This study will not only provide new insights in the GQDs-induced cell damage performed in multiple types of cell death, but also in the influence of chemical modification on the toxicity of GQDs.

Revisiting the cytotoxicity of quantum dots: an in-depth overview

Recently, medical research has been shifting its focus to nanomedicine and nanotherapeutics in the pursuit of drug development research. Quantum dots (QDs) are a critical class of nanomaterials due to their unique properties, which include optical, electronic, and engineered biocompatibility in physiological environments. These properties have made QDs an attractive biomedical resource such that they have found application as both in vitro labeling and in vivo theranostic (therapy-diagnostic) agents. Considerable research has been conducted exploring the suitability of QDs in theranostic applications, but the cytotoxicity of QDs remains an obstacle. Several types of QDs have been investigated over the past decades, which may be suitable for use in biomedical applications if the barrier of cytotoxicity can be resolved. This review attempts to report and analyze the cytotoxicity of the major QDs along with relevant related aspects.

Antimicrobial Activity and Mechanism of Functionalized Quantum Dots

An essential characteristic of quantum dots (QDs) is their antimicrobial activity. Compared with conventional antibiotics, QDs not only possess photoluminescence properties for imaging and photodynamic therapy but also have high structural stability. To enhance their antimicrobial efficiency, QDs usually are functionalized by polymers, including poly(ethylene glycol), polyethyleneimine, and poly-l-lysine. Also, QDs conjugated with polymers, such as poly(vinylpyrrolidone) and polyvinylidene fluoride, are prepared as antimicrobial membranes. The main antimicrobial mechanisms of QDs are associated with inducing free radicals, disrupting cell walls/membranes, and arresting gene expression. The different mechanisms from traditional antibiotics allow QDs to play antimicrobial roles in multi-drug-resistant bacteria and fungi. Since the toxicity of the QDs on animal cells is relatively low, they have broad application in antimicrobial research as an effective alternative of traditional antibiotics.

Toxicity and chronic effects of deltamethrin exposure on zebrafish (Danio rerio) as a reference model for freshwater fish community

In this study zebrafish specimens were exposed for 15 days to 0.25, 0.5, 1 and 2 μg L^-1 non-lethal concentrations of deltamethrin (DM) knowing that is the active compound in insecticides used on agricultural crops. They were investigated important issues resulted during the chronic exposure with DM: effects on aggressive behavior and swimming performances knowing that is a high neurotoxic compound; toxicity on nervous system investigated on telencephalon, optic tectum and cerebellum; activity of PCNA, p53 and TUNEL as toxicity markers in immunocytochemistry of the histological samples; changes of elements concentrations in the fish body and their role in detoxification of DM. This scenario investigated the harmful effects of this compound for freshwater fish communities. The aggressive behavior significantly increased and remained constant for the concentration 0.5 μg L^-1. They were not evidences in changing of anxiety level and swimming performances. The nervous system suffered significant damage for all studied concentrations and confirmed the changes in the behavior. Selenium concentration in the body decreased and may be involved in the detoxification processes.

Developmental neurotoxicity and immunotoxicity induced by graphene oxide in zebrafish embryos

Graphene oxide (GO) has emerged as the worldwide promising candidate for biomedical application, such as for drug delivery, bio-sensing and anti-cancer therapy. This study was focused on the zebrafish and RAW264.7 cell line as in vivo and in vitro models to assess the potential developmental neurotoxicity and immunotoxicity of GO. No obvious acute developmental toxicity was observed upon treatments with 0.01, 0.1, and 1 μg/mL GO for five consecutive days. However, decreased hatching rate, increased malformation rate, heart beat rate and hypoactivity of locomotor behavior were detected when exposed to 10 μg/mL GO. Also, RT-PCR analysis revealed that expressions of genes related to the nervous system were up-regulated. The potential risk of GO for developmental neurotoxicity may be ascribed to the high level of oxidative stress induced by high concentration of GO. Most importantly, the mRNA levels of immune response associated genes, such as interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-α (TNFα), interferon-γ (IFN-γ) were significantly increased under environmental concentration exposure. The activation of pro-inflammatory immune response was also observed in macrophage cell line. Taken together, our results demonstrated that immunotoxicity is a sensitive indicator for assessment of bio-compatibility of GO.

Nitrogen-doped graphene quantum dots (N-GQDs) perturb redox-sensitive system via the selective inhibition of antioxidant enzyme activities in zebrafish

Graphene quantum dots (GQDs) are well-known for its potential applications for bioimaging, biosensor, and drug carrier in biomedicine. GQDs are well characteristic of intrinsic peroxidase-like catalytic activity, which is proven effective in scavenging the free radicals, such assuperoxide anion, hydrogen peroxide, and hydroxyl radical. GQDs are also well praised for its low in vivo and in vitro toxicity. Here, we found that nitrogen-doped GQDs (N-GQDs) can strongly disturb redox-sensitive system via the selective inhibition of endogenous antioxidant enzyme activities in zebrafish. The enzyme activities or transcription levels of a battery of hemoproteins including catalase (CAT), superoxide dismutase (SOD), respiratory chain complex I, complex Ⅲ, hemoglobin (Hb), and myeloperoxidase (MPO), were significantly suppressed by N-GQDs. We also found that N-GQDs activated the cytochrome P450 monooxygenase (e.g. cyp1a) and the associated aryl-hydrocarbon receptor repressors (ahrr1 and ahrr2) in zebrafish embryos. Compared to the ultrasmall graphene oxide (USGO), N-GQDs exhibited stronger fluorescent permeability and tissue-specific bio-accumulative effects. Taken together, our findings highlighted that exposure to N-GQDs can disrupt endogenous antioxidant enzyme activities, possibly via the competitive inhibition of electron transfer process. Our results in this study provided solid data for biosafety evaluations of various types of GQDs, and created an alert for the future biomedical applications of N-GQDs.

Graphene-based advanced nanoplatforms and biocomposites from environmentally friendly and biomimetic approaches

Environmentally friendly and biomimetic approaches to fabricate graphene-based advanced nanoplatforms and biocomposites for biomedical applications are summarized in this review.