Genotoxic response and damage recovery of macrophages to graphene quantum dots

Recent breakthroughs in graphene quantum dot-enhanced sonodynamic and photodynamic therapy

Water-soluble graphene quantum dots (GQDs) have recently exhibited considerable potential for diverse biomedical applications owing to their exceptional optical and chemical properties. However, the pronounced heterogeneity in the composition, size, and morphology of GQDs poses challenges for a comprehensive understanding of the intricate correlation between their structural attributes and functional properties. This variability also introduces complexities in scaling the production processes and addressing safety considerations. Light and sound have firmly established their role in clinical applications as pivotal energy sources for minimally invasive therapeutic interventions. Given the limited penetration depth of light, photodynamic therapy (PDT) predominantly targets superficial conditions such as dermatological disorders, head and neck malignancies, ocular ailments, and early-stage esophageal cancer. Conversely, ultrasound-based sonodynamic therapy (SDT) capitalizes on its superior ability to propagate and focus ultrasound within biological tissues, enabling a diverse range of therapeutic applications, including the management of gliomas, breast cancer, hematological tumors, and modulation of the blood-brain barrier (BBB). Considering the advancements in theranostic and precision therapies, reevaluating these conventional energy sources and their associated sensitizers is imperative. This review introduces three prevalent treatment modalities that harness light and sound stimuli: PDT, SDT, and a synergistic approach that integrates PDT and SDT. This study delineated the therapeutic dynamics and contemporary designs of sensitizers tailored to these modalities. By exploring the historical context of the field and elucidating the latest design strategies, this review underscores the pivotal role of GQDs in propelling the evolution of PDT and SDT. This aspires to stimulate researchers to develop "multimodal" therapies integrating both light and sound stimuli.

Graphene Quantum Dots Nonmonotonically Influence the Horizontal Transfer of Extracellular Antibiotic Resistance Genes via Bacterial Transformation

Graphene quantum dots (GQDs) coexist with antibiotic resistance genes (ARGs) in the environment. Whether GQDs influence ARG spread needs investigation, since the resulting development of multidrug-resistant pathogens would threaten human health. This study investigates the effect of GQDs on the horizontal transfer of extracellular ARGs (i.e., transformation, a pivotal way that ARGs spread) mediated by plasmids into competent Escherichia coli cells. GQDs enhance ARG transfer at lower concentrations, which are close to their environmental residual concentrations. However, with further increases in concentration (closer to working concentrations needed for wastewater remediation), the effects of enhancement weaken or even become inhibitory. At lower concentrations, GQDs promote the gene expression related to pore-forming outer membrane proteins and the generation of intracellular reactive oxygen species, thus inducing pore formation and enhancing membrane permeability. GQDs may also act as carriers to transport ARGs into cells. These factors result in enhanced ARG transfer. At higher concentrations, GQD aggregation occurs, and aggregates attach to the cell surface, reducing the effective contact area of recipients for external plasmids. GQDs also form large agglomerates with plasmids and thus hindering ARG entrance. This study could promote the understanding of the GQD-caused ecological risks and benefit their safe application.

The stereoselective toxicity of dinotefuran to Daphnia magna: A systematic assessment from reproduction, behavior, oxidative stress and digestive function

Dinotefuran is a promising neonicotinoid insecticide with chiral structure. In the present study, the stereoselective toxicity of dinotefuran to Daphnia magna (D. magna) was studied. The present result showed that S-dinotefuran inhibited the reproduction of D. magna at 5.0 mg/L. However, both R-dinotefuran and S-dinotefuran had no genotoxicity to D. magna. Additionally, neither R-dinotefuran nor S-dinotefuran had negative influences on the motor behavior of D. magna. However, S-dinotefuran inhibited the feeding behavior of D. magna at 5.0 mg/L. Both R-dinotefuran and S-dinotefuran induced oxidative stress effect in D. magna after exposure. R-dinotefuran significantly activated the activities of superoxide dismutase (SOD) and glutathione S-transferase (GST), while S-dinotefuran showed the opposite effect. S-dinotefuran had more obvious activation effect on the acetylcholinesterase (AchE) activity and trypsin activity compared to R-dinotefuran. The transcriptome sequencing results showed that S-dinotefuran induced more DEGs in D. magna, and affected the normal function of ribosome. The DEGs were mainly related to the synthesis and metabolism of biomacromolecules, indicating the binding mode between dinotefuran enantiomer and biomacromolecules were different. Additionally, the present result indicated that the digestive enzyme activity and digestive gene expression levels in D. magna were greatly enhanced to cope with the inhibition of S-dinotefuran on the feeding.

Activation of KLF6 by titanate nanofibers and regulatory roles of KLF6 on ATF3 in the endothelial monolayer and mouse aortas

Although titanium (Ti)-based nanomaterials (NMs) were traditionally considered as biologically inert materials, it was recently reported that Ti-based NMs induce adverse vascular effects by inhibiting Kruppel-like factor 2 (KLF2) and/or KLF4, vasoprotective KLFs with well-documented regulatory activity in NO signaling. However, the potential roles of other KLFs are not clear. KLF6 was recently identified as an important KLF involved in regulating endothelial dysfunction, inflammation, and angiogenesis, therefore, this study investigated the influence of titanate nanofibers (TiNFs) on KLF6-mediated events. Ingenuity pathway analysis (IPA) showed that TiNFs altered the expression of a panel of KLF6-related genes: KLF6-mediated gene ontology (GO) terms were altered, categories including cytokine-mediated signaling pathways, transcription factor (TF) functions and membrane-bound organelles. Additionally, RT-PCR confirmed that TiNFs increased KLF6 activating transcription factor 3 (ATF3), a TF involved in endoplasmic reticulum (ER) stress, and ELISA confirmed the increase of soluble monocyte chemotactic protein 1 (sMCP-1), a KLF6-related inflammatory cytokine. Interestingly, the activation of klf6, atf3 and C-C motif chemokine ligand 2 (ccl2; mcp-1 encoding gene) was observed in aortas of mice following one-time intravenous injection but not intratracheal instillation of TiNFs (100 μg per mouse), indicating a need for direct contact with NMs to activate klf6-mediated pathways in vivo. In endothelial cells, KLF6 knockdown inhibited the expression of ATF3 but not CCL2, suggesting the regulatory role of KLF6 in ATF3 expression. Overall, this study uncovered a previously unknown role of KLF6 in TiNF-induced vascular effects both in vitro and in vivo.

The DNA damage potential of quantum dots: Toxicity, mechanism and challenge

Quantum dots (QDs) are semiconductor nanoparticles (1-10 nm) with excellent optical and electrical properties. As QDs show great promise for applications in fields such as biomedicine, their biosafety is widely emphasized. Therefore, studies on the potential 'nanotoxicity' of QDs in genetic material are warranted. This review summarizes and discusses recent reports derived from different cell lines or animal models concerning the effects of QDs on genetic material. QDs could induce many types of genetic material damage, which subsequently triggers a series of cellular adverse outcomes, including apoptosis, cell cycle arrest and senescence. However, the individual biological and ecological significance of the genotoxicity of QDs is not yet clear. In terms of mechanisms of genotoxicity, QDs can damage DNA either through their own nanomorphology or through the released metal ions. It also includes the reactive oxygen species generation, inflammation and failure of DNA damage repair. Notably, apoptosis may lead to false positive results in genotoxicity tests. Finally, given the different uses of QDs and the interference of the physicochemical properties of QDs on the test method, genotoxicity testing of QDs should be different from traditional toxic compounds, which requires further research.

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.

Genotoxicity of Graphene-Based Materials

Graphene-based materials (GBMs) are a broad family of novel carbon-based nanomaterials with many nanotechnology applications. The increasing market of GBMs raises concerns on their possible impact on human health. Here, we review the existing literature on the genotoxic potential of GBMs over the last ten years. A total of 50 articles including in vitro, in vivo, in silico, and human biomonitoring studies were selected. Graphene oxides were the most analyzed materials, followed by reduced graphene oxides. Most of the evaluations were performed in vitro using the comet assay (detecting DNA damage). The micronucleus assay (detecting chromosome damage) was the most used validated assay, whereas only two publications reported results on mammalian gene mutations. The same material was rarely assessed with more than one assay. Despite inhalation being the main exposure route in occupational settings, only one in vivo study used intratracheal instillation, and another one reported human biomonitoring data. Based on the studies, some GBMs have the potential to induce genetic damage, although the type of damage depends on the material. The broad variability of GBMs, cellular systems and methods used in the studies precludes the identification of physico-chemical properties that could drive the genotoxicity response to GBMs.

Nanomaterials-based photosensitizers and delivery systems for photodynamic cancer therapy

The increasing cancer morbidity and mortality requires the development of high-efficiency and low-toxicity anticancer approaches. In recent years, photodynamic therapy (PDT) has attracted much attention in cancer therapy due to its non-invasive features and low side effects. Photosensitizer (PS) is one of the key factors of PDT, and its successful delivery largely determines the outcome of PDT. Although a few PS molecules have been approved for clinical use, PDT is still limited by the low stability and poor tumor targeting capacity of PSs. Various nanomaterial systems have shown great potentials in improving PDT, such as metal nanoparticles, graphene-based nanomaterials, liposomes, ROS-sensitive nanocarriers and supramolecular nanomaterials. The small molecular PSs can be loaded in functional nanomaterials to enhance the PS stability and tumor targeted delivery, and some functionalized nanomaterials themselves can be directly used as PSs. Herein, we aim to provide a comprehensive understanding of PDT, and summarize the recent progress of nanomaterials-based PSs and delivery systems in anticancer PDT. In addition, the concerns of nanomaterials-based PDT including low tumor targeting capacity, limited light penetration, hypoxia and nonspecific protein corona formation are discussed. The possible solutions to these concerns are also discussed.

Respiratory exposure to graphene quantum dots causes fibrotic effects on lung, liver and kidney of mice

Graphene quantum dots (GQDs), as a novel graphene-based nanoparticle, presented a bright prospect in fields of biomedicine due to their excellent optical property. However, the biosafety assessment of GQDs is far behind their rapid development, which could restrict their wilder applications. This study focused on the potential adverse effects of two kinds of promising GQDs, i.e. nitrogen-doping graphene quantum dots (N-GQDs) and amino-modified graphene quantum dot (A-GQDs) on primary target organs of GNMs, including lung, liver and kidney. The intranasal instillation used here was to imitate the respiratory exposure of GQDs that is a commonly exposure route of GQDs in the environment. Although no severe damages associated with general health occurred in mice treated with GQDs, the fibrosis evidenced by statistically significant increases in the area of collagen I and TGF-ß1 and p-Smad3 expressions were observed in the lung, liver and kidney tissues. Interestingly, the fibrotic effect induced by GQDs could be effectively alleviated by a ferroptosis-specific inhibitor, which demonstrated a close relationship of fibrosis and ferroptosis. This study not only provides new insights on the toxicity mechanisms of GQDs, but also offers some efficient ways to control toxicity of GQDs, like dosage threshold and small molecular drugs.

Integrating transcriptome and physiological analyses to elucidate the molecular responses of buckwheat to graphene oxide

With the increasing application of nanomaterials, evaluation of the phytotoxicity of nanoparticles has attracted considerable interest. Buckwheat is an economically pseudocereal crop, which is a potential model for investigating the response of plants to hazardous materials. In this study, the response of buckwheat to graphene oxide (GO) was investigated by integrating physiological and transcriptome analysis. GO can penetrate into buckwheat root and stem, and high concentrations of GO inhibited seedlings growth. High concentration of GO improved ROS production and regulated the activities and gene expression of oxidative enzymes, which implying GO may affect plant growth via regulating ROS detoxification. Root and stem exhibit distinct transcriptomic responses to GO, and the GO-responsive genes in stem are more enriched in cell cycle and epigenetic regulation. GO inhibited plant hormone biosynthesis and signaling by analyzing the expression data. Additionally, 97 small secreted peptides (SSPs) encoding genes were found to be involved in GO response. The gene expression of 111 transcription factor (TFs) and 43 receptor-like protein kinases (RLKs) were regulated by GO, and their expression showed high correlation with SSPs. Finally, the TFs-SSPs-RLKs signaling networks in regulating GO response were proposed. This study provides insights into the molecular responses of plants to GO.

Transcriptomic-based toxicological investigations of graphene oxide with modest cytotoxicity to human umbilical vein endothelial cells: changes of Toll-like receptor signaling pathways

The wide uses of graphene oxide (GO) lead to the contact of GO with vascular systems, so it is necessary to investigate the toxicological effects of GO to endothelial cells. Recently, we reported that GO of small lateral size (<500 nm) was relatively biocompatible to human umbilical vein endothelial cells (HUVECs), but recent studies by using omics-techniques revealed that nanomaterials (NMs) even without acute cytotoxicity might induce other toxicological effects. This study investigated the effects of GO on HUVECs based on RNA-sequencing and bioinformatics analysis. Even after exposure to 100 μg/ml GO, the cellular viability of HUVECs was higher than 70%. Furthermore, 25 μg/ml GO was internalized but did not induce ultrastructural changes or intracellular superoxide. These results combined indicated GO's relatively high biocompatibility. However, by analyzing the most significantly altered Gene Ontology terms and Kyoto Encyclopedia of Gene and Genomes pathways, we found that 25 μg/ml GO altered pathways related to immune systems' functions and the responses to virus. We further verified that GO exposure significantly decreased Toll-like receptor 3 and interleukin 8 proteins, indicating an immune suppressive effect. However, THP-1 monocyte adhesion was induced by GO with or without the presence of inflammatory stimulus lipopolysaccharide. We concluded that GO might inhibit the immune responses to virus in endothelial cells at least partially mediated by the inhibition of TLR3. Our results also highlighted a need to investigate the toxicological effects of NMs even without acute cytotoxicity by omics-based techniques.

Direct and Indirect Genotoxicity of Graphene Family Nanomaterials on DNA-A Review

Graphene family nanomaterials (GFNs), including graphene, graphene oxide (GO), reduced graphene oxide (rGO), and graphene quantum dots (GQDs), have manifold potential applications, leading to the possibility of their release into environments and the exposure to humans and other organisms. However, the genotoxicity of GFNs on DNA remains largely unknown. In this review, we highlight the interactions between DNA and GFNs and summarize the mechanisms of genotoxicity induced by GFNs. Generally, the genotoxicity can be sub-classified into direct genotoxicity and indirect genotoxicity. The direct genotoxicity (e.g., direct physical nucleus and DNA damage) and indirect genotoxicity mechanisms (e.g., physical destruction, oxidative stress, epigenetic toxicity, and DNA replication) of GFNs were summarized in the manuscript, respectively. Moreover, the influences factors, such as physicochemical properties, exposure dose, and time, on the genotoxicity of GFNs are also briefly discussed. Given the important role of genotoxicity in GFNs exposure risk assessment, future research should be conducted on the following: (1) developing reliable testing methods; (2) elucidating the response mechanisms associated with genotoxicity in depth; and (3) enriching the evaluation database regarding the type of GFNs, applied dosages, and exposure times.

Endocytosis of abiotic nanomaterials and nanobiovectors: Inhibition of membrane trafficking

Humans are exposed to nanoscopical nanobiovectors (e.g. coronavirus SARS-CoV-2) as well as abiotic metal/carbon-based nanomaterials that enter cells serendipitously or intentionally. Understanding the interactions of cell membranes with these abiotic and biotic nanostructures will facilitate scientists to design better functional nanomaterials for biomedical applications. Such knowledge will also provide important clues for the control of viral infections and the treatment of virus-induced infectious diseases. In the present review, the mechanisms of endocytosis are reviewed in the context of how nanomaterials are uptaken into cells. This is followed by a detailed discussion of the attributes of man-made nanomaterials (e.g. size, shape, surface functional groups and elasticity) that affect endocytosis, as well as the different human cell types that participate in the endocytosis of nanomaterials. Readers are then introduced to the concept of viruses as nature-derived nanoparticles. The mechanisms in which different classes of viruses interact with various cell types to gain entry into the human body are reviewed with examples published over the last five years. These basic tenets will enable the avid reader to design advanced drug delivery and gene transfer nanoplatforms that harness the knowledge acquired from endocytosis to improve their biomedical efficacy. The review winds up with a discussion on the hurdles to be addressed in mimicking the natural mechanisms of endocytosis in nanomaterials design.

A critical review on genotoxicity potential of low dimensional nanomaterials

Low dimensional nanomaterials (LDNMs) have earned attention among researchers as they exhibit a larger surface area to volume and quantum confinement effect compared to high dimensional nanomaterials. LDNMs, including 0-D and 1-D, possess several beneficial biomedical properties such as bioimaging, sensor, cosmetic, drug delivery, and cancer tumors ablation. However, they threaten human beings with the adverse effects of cytotoxicity, carcinogenicity, and genotoxicity when exposed for a prolonged time in industry or laboratory. Among different toxicities, genotoxicity must be taken into consideration with utmost importance as they inherit DNA related disorders causing congenital disabilities and malignancy to human beings. Many researchers have performed NMs' genotoxicity using various cell lines and animal models and reported the effect on various physicochemical and biological factors. In the present work, we have compiled a comparative study on the genotoxicity of the same or different kinds of NMs. Notwithstanding, we have included the classification of genotoxicity, mechanism, assessment, and affecting factors. Further, we have highlighted the importance of studying the genotoxicity of LDNMs and signified the perceptions, future challenges, and possible directives in the field.

How macrophages respond to two-dimensional materials: a critical overview focusing on toxicity

With wider use of graphene-based materials and other two-dimensional (2 D) materials in various fields, including electronics, composites, biomedicine, etc., 2 D materials can trigger undesired effects at cellular, tissue and organ level. Macrophages can be found in many organs. They are one of the most important cells in the immune system and they are relevant in the study of nanomaterials as they phagocytose them. Nanomaterials have multi-faceted effects on phagocytic immune cells like macrophages, showing signs of inflammation in the form of pro-inflammatory cytokine or reactive oxidation species production, or upregulation of activation markers due to the presence of these foreign bodies. This review is catered to researchers interested in the potential impact and toxicity of 2 D materials, particularly in macrophages, focusing on few-layer graphene, graphene oxide, graphene quantum dots, as well as other promising 2 D materials containing molybdenum, manganese, boron, phosphorus and tungsten. We describe applications relevant to the growing area of 2 D materials research, and the possible risks of ions and molecules used in the production of these promising 2 D materials, or those produced by the degradation and dissolution of 2 D materials.

Graphene Quantum Dots Disrupt Embryonic Stem Cell Differentiation by Interfering with the Methylation Level of Sox2

The tremendous potential for graphene quantum dots (GQDs) in biomedical applications has led to growing concerns of their health risks in human beings. However, present studies mainly focused on oxidative stress, apoptosis, and other general toxicity effects; the knowledge on the developmental toxicity and the related regulatory mechanisms is still far from sufficient. Our study revealed the development retardation of mouse embryonic stem cells (mESCs) caused by GQDs with a novel DNA methylation epigenetic mechanism. Specifically, GQDs were internalized into cells mainly via energy-dependent endocytosis, and a significant fraction of internalized GQDs remained in the cells even after a 48-h clearance period. Albeit with unobservable cytotoxicity or any influences on cell pluripotency, significant retardation was found in the in vitro differentiation of the mESCs into embryoid bodies (EBs) with the upregulation of Sox2 levels in GQD pretreatment groups. Importantly, this effect could be contributed by GQD-induced inhibition in CpG methylation of Sox2 through altering methyltransferase and demethyltransferase transcriptional expressions, and the demethyltransferase inhibitor, bobcat339 hydrochloride, reduced GQD-induced upregulation of Sox2. The current study first demonstrated that GQDs compromised the differentiation program of the mESCs, potentially causing development retardation. Exposure to this nanomaterial during gestation or early developmental period would cause adverse health risks and is worthy of more attention.

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.

Transcriptomic analysis suggested the involvement of impaired lipid droplet biogenesis in graphene oxide-induced cytotoxicity in human umbilical vein endothelial cells

Previous studies revealed that direct contact with graphene oxide (GO) induced cytotoxic effects, but the importance of involvement of metabolic pathways, in particular lipid metabolism pathways, might be overlooked. In this study, human umbilical vein endothelial cells (HUVECs) were exposed to GO with large size (denoted as GO-L) or small size (denoted as GO-S), and transcriptomics were used to understand the mechanisms of cytotoxicity of GO at systemic levels. It was shown that GO-L more significantly induced cytotoxicity compared with GO-S. Transcriptomic analysis revealed that compared with GO-S, GO-L had larger impact on gene ontology terms related with mitochondrial function as well as Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related with cell death and growth. But GO-S showed greater influence on KEGG pathways related with lipid metabolism. Both types of GO showed minimal impact on oxidative stress but increased de novo lipogenesis protein fatty acid synthase (FASN). However, only GO-S significantly promoted acyl-CoA synthetase 3 (ACSL3), a key enzyme responsible for esterification of free fatty acids and lipid droplet biogenesis. Not surprisingly, GO-L but not GO-S impaired lipid droplet biogenesis, and increasing lipid levels by oleic acid or α-linolenic acid reduced the cytotoxicity of GO-L to HUVECs. Combined, the results from this study suggested that impaired lipid droplet biogenesis was involved in GO-induced cytotoxicity in HUVECs, and inducing lipid droplet biogenesis could prevent the cytotoxicity of GO.

Toxicity of different types of quantum dots to mammalian cells in vitro: An update review

Currently, there are a great quantity type of quantum dots (QDs) that has been developed by researchers. Depending on the core material, they can be roughly divided into cadmium, silver, indium, carbon and silicon QDs. And studies on the toxicity of QDs are also increasing rapidly, but in vivo tests in model animals fail to reach a consistent conclusion. Therefore, we review the literatures dealing with the cytotoxicity of QDs in mammalian cells in vitro. After a short summary of the application characteristics of five types of QDs, the fate of QDs in cells will be discussed, ranging from the uptake, transportation, sublocation and excretion. A substantial part of the review will be focused on in vitro toxicity, in which the type of QDs is combined with their adverse effect and toxic mechanism. Because of their different luminescent properties, different subcellular fate, and different degree of cytotoxicity, we provide an overview on the balance of optical stability and biocompatibility of QDs and give a short outlook on future direction of cytotoxicology of QDs.

Genotoxicity of Nanomaterials: Advanced In Vitro Models and High Throughput Methods for Human Hazard Assessment-A Review

Changes in the genetic material can lead to serious human health defects, as mutations in somatic cells may cause cancer and can contribute to other chronic diseases. Genotoxic events can appear at both the DNA, chromosomal or (during mitosis) whole genome level. The study of mechanisms leading to genotoxicity is crucially important, as well as the detection of potentially genotoxic compounds. We consider the current state of the art and describe here the main endpoints applied in standard human in vitro models as well as new advanced 3D models that are closer to the in vivo situation. We performed a literature review of in vitro studies published from 2000-2020 (August) dedicated to the genotoxicity of nanomaterials (NMs) in new models. Methods suitable for detection of genotoxicity of NMs will be presented with a focus on advances in miniaturization, organ-on-a-chip and high throughput methods.

DNA-damage and cell cycle arrest initiated anti-cancer potency of super tiny carbon dots on MCF7 cell line

While carbon-based materials have spearheaded numerous breakthroughs in biomedicine, they also have procreated many logical concerns on their overall toxicity. Carbon dots (CDs) as a respectively new member have been extensively explored in nucleus directed delivery and bioimaging due to their intrinsic fluorescence properties coupled with their small size and surface properties. Although various in vitro/in vivo studies have shown that CDs are mostly biocompatible, sufficient information is lacking regarding genotoxicity of them and underlying mechanisms. This study aims to analyze the real-time cytotoxicity of super tiny CDs (2.05 ± 0.22 nm) on human breast cancer cells (MCF7) and human primary dermal fibroblast cell cultures (HDFa) by xCELLigence analysis system for further evaluating their genotoxicity and clastogenicity to evaluate the anti-tumor potential of CDs on breast adenocarcinoma. As combined with flow cytometry studies, comet assay and cytokinesis-block micronucleus assay suggest that the CDs can penetrate to the cell nuclei, interact with the genetic material, and explode DNA damage and G0/G1 phase arrest in cancer cells even at very low concentrations (0.025 ppm) which provide a strong foundation for the design of potentially promising CD-based functional nanomaterials for DNA-damage induced treatment in cancer therapy.

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.

Antioxidant Activity of Graphene Quantum Dots Prepared in Different Electrolyte Environments

Antioxidants can reduce or inhibit damage such as oxidative decay caused by elevated levels of free radicals. Therefore, pursuing antioxidants with excellent properties has attracted more and more attention. Graphene quantum dots (GQDs) are considered a promising material because of their good free radical scavenging activity, low toxicity, and excellent water solubility. However, their scavenging efficiency, antioxidant mechanism, and effective control methods need to be improved. Herein, in order to further reveal the antioxidant mechanism of GQDs, the role of electrolytes in improving the antioxidant activity of GQDs is explored. In addition, 1,1-diphenyl-2-picrazine (DPPH∙), hydroxyl (∙OH), and superoxide (∙O₂⁻) free radicals are used to evaluate the antioxidant activity of the as-prepared GQDs. Combined with transmission electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, and cyclic volt–ampere characteristic curves, the effects of an electrolytic environment on the surface functional groups, charge transfer capability, and defect states of GQDs are obtained. The antioxidant mechanism of GQDs and how to improve their antioxidant activity are further elucidated.