Modeling better in vitro models for the prediction of nanoparticle toxicity: a review

Applications of 3D organoids in toxicological studies: a comprehensive analysis based on bibliometrics and advances in toxicological mechanisms

A mechanism exploration is an important part of toxicological studies. However, traditional cell and animal models can no longer meet the current needs for in-depth studies of toxicological mechanisms. The three-dimensional (3D) organoid derived from human embryonic stem cells (hESC) or induced pluripotent stem cells (hiPSC) is an ideal experimental model for the study of toxicological effects and mechanisms, which further recapitulates the human tissue microenvironment and provides a reliable method for studying complex cell-cell interactions. This article provides a comprehensive overview of the state of the 3D organoid technology in toxicological studies, including a bibliometric analysis of the existing literature and an exploration of the latest advances in toxicological mechanisms. The use of 3D organoids in toxicology research is growing rapidly, with applications in disease modeling, organ-on-chips, and drug toxicity screening being emphasized, but academic communications among countries/regions, institutions, and research scholars need to be further strengthened. Attempts to study the toxicological mechanisms of exogenous chemicals such as heavy metals, nanoparticles, drugs and organic pollutants are also increasing. It can be expected that 3D organoids can be better applied to the safety evaluation of exogenous chemicals by establishing a standardized methodology.

Nanozyme as a rising star for metabolic disease management

Nanozyme, characterized by outstanding and inherent enzyme-mimicking properties, have emerged as highly promising alternatives to natural enzymes owning to their exceptional attributes such as regulation of oxidative stress, convenient storage, adjustable catalytic activities, remarkable stability, and effortless scalability for large-scale production. Given the potent regulatory function of nanozymes on oxidative stress and coupled with the fact that reactive oxygen species (ROS) play a vital role in the occurrence and exacerbation of metabolic diseases, nanozyme offer a unique perspective for therapy through multifunctional activities, achieving essential results in the treatment of metabolic diseases by directly scavenging excess ROS or regulating pathologically related molecules. The rational design strategies, nanozyme-enabled therapeutic mechanisms at the cellular level, and the therapies of nanozyme for several typical metabolic diseases and underlying mechanisms are discussed, mainly including obesity, diabetes, cardiovascular disease, diabetic wound healing, and others. Finally, the pharmacokinetics, safety analysis, challenges, and outlooks for the application of nanozyme are also presented. This review will provide some instructive perspectives on nanozyme and promote the development of enzyme-mimicking strategies in metabolic disease therapy.

Epigallocatechin gallate alleviated the in vivo toxicity of ZnO nanoparticles to mouse intestine

To evaluate the oral toxicity of nanoparticles (NPs), it is necessary to consider the interactions between NPs and nutrient molecules. Recently, we reported that epigallocatechin gallate (EGCG), a healthy component in green tea, alleviated the toxicity of ZnO NPs to 3D Caco-2 spheroids in vitro. The present study investigated the combined effects of EGCG and ZnO NPs to mice in vivo. Mice were administrated with 35 or 105 mg/kg bodyweight ZnO NPs with or without the presence of 80 mg/kg bodyweight EGCG via gastric route, once a day, for 21 days, and the influences of EGCG on the toxicity of ZnO NPs to intestine were investigated. We found that EGCG altered the colloidal properties of ZnO NPs both in water and artificial intestine juice. As expected, ZnO NPs induced toxicological effects, such as decreased bodyweight, higher Chiu's scores, and ultrastructural changes in intestine, whereas EGCG alleviated these effects. Combined exposure to EGCG and ZnO NPs also changed trace element levels in mouse intestine. For example, the levels of Ti, Co, and Ni were only significantly elevated after co-exposure to EGCG and ZnO NPs, and Fe levels were only significantly decreased by ZnO NPs. Western blot analysis suggested that tight junction (TJ) and endoplasmic reticulum (ER) proteins were elevated by ZnO NPs, but EGCG inhibited this trend. Combined, these data suggested that gastric exposure to ZnO NPs induced intestinal damage, trace element imbalance, and TJ/ER protein expression in mouse intestine, whereas EGCG alleviated these effects of ZnO NPs.

Understanding PFAS toxicity through cell culture metabolomics: Current applications and future perspectives

Per- and polyfluoroalkyl substances (PFAS), ubiquitous environmental contaminants, pose significant challenges to ecosystems and human health. While cell cultures have emerged as new approach methodologies (NAMs) in ecotoxicity research, metabolomics is an emerging technique used to characterize the small-molecule metabolites present in cells and to understand their role in various biological processes. Integration of metabolomics with cell cultures, known as cell culture metabolomics, provides a novel and robust tool to unravel the complex molecular responses induced by PFAS exposure. In vitro testing also reduces reliance on animal testing, aligning with ethical and regulatory imperatives. The current review summarizes key findings from recent studies utilizing cell culture metabolomics to investigate PFAS toxicity, highlighting alterations in metabolic pathways, biomarker identification, and the potential linkages between metabolic perturbations. Additionally, the paper discusses different types of cell cultures and metabolomics methods used for studies of environmental contaminants and particularly PFAS. Future perspectives on the combination of metabolomics with other advanced technologies, such as single-cell metabolomics (SCM), imaging mass spectrometry (IMS), extracellular flux analysis (EFA), and multi-omics are also explored, which offers a holistic understanding of environmental contaminants. The synthesis of current knowledge and identification of research gaps provide a foundation for future investigations that aim to elucidate the complexities of PFAS-induced cellular responses and contribute to the development of effective strategies for mitigating their adverse effects on human health.

State of the Art of Silica Nanoparticles: An Overview on Biodistribution and Preclinical Toxicity Studies

Over the past few years, nanoparticles have drawn particular attention in designing and developing drug delivery systems due to their distinctive advantages like improved pharmacokinetics, reduced toxicity, and specificity. Along with other successful nanosystems, silica nanoparticles (SNPs) have shown promising effects for therapeutic and diagnostic purposes. These nanoparticles are of great significance owing to their modifiable surface with various ligands, tunable particle size, and large surface area. The rate and extent of degradation and clearance of SNPs depend on factors such as size, shape, porosity, and surface modification, which directly lead to varying toxic mechanisms. Despite SNPs' enormous potential for clinical and pharmaceutical applications, safety concerns have hindered their translation into the clinic. This review discusses the biodistribution, toxicity, and clearance of SNPs and the formulation-related factors that ultimately influence clinical efficacy and safety for treatment. A holistic view of SNP safety will be beneficial for developing an enabling SNP-based drug product.

The uses of zebrafish (Danio rerio) as an in vivo model for toxicological studies: A review based on bibliometrics

An in vivo model is necessary for toxicology. This review analyzed the uses of zebrafish (Danio rerio) in toxicology based on bibliometrics. Totally 56,816 publications about zebrafish from 2002 to 2023 were found in Web of Science Core Collection, with Toxicology as the top 6 among all disciplines. Accordingly, the bibliometric map reveals that "toxicity" has become a hot keyword. It further reveals that the most common exposure types include acute, chronic, and combined exposure. The toxicological effects include behavioral, intestinal, cardiovascular, hepatic, endocrine toxicity, neurotoxicity, immunotoxicity, genotoxicity, and reproductive and transgenerational toxicity. The mechanisms include oxidative stress, inflammation, autophagy, and dysbiosis of gut microbiota. The toxicants commonly evaluated by using zebrafish model include nanomaterials, arsenic, metals, bisphenol, and dioxin. Overall, zebrafish provide a unique and well-accepted model to investigate the toxicological effects and mechanisms. We also discussed the possible ways to address some of the limitations of zebrafish model, such as the combination of human organoids to avoid species differences.

Mutuality of epigenetic and nanoparticles: two sides of a coin

Nowadays nanoparticles (NPs) due to their multidimensional applications in enormous different fields, has become an exciting research topic. In particular, they could attract a noticeable interest as drug deliver with increased bioavailability, therapeutic efficacy and drug specificity. Epigenetic can be considered as a complex network of molecular mechanism which are engaged in gene expression and have a vital role in regulation of environmental effects on ethology of different disorders like neurological disorders, cancers and cardiovascular diseases. For many of them epigenetic therapy was proposed although its application accompanied with limitations, due to drug toxicity. In this review we evaluate two aspects to epigenetic in the field of NPs: firstly, the role of epigenetic in regulation of nanotoxicity and secondly application of NPs as potential carriers for epidrugs.

Magnetic graphene oxide nanocomposites induce cytotoxicity in ADSCs via GPX4 regulating ferroptosis

Magnetic graphene oxide nanocomposites (MGO NPs) have been widely studied in biomedical applications. However, their cytotoxicity and underlying mechanisms remain unclear. In this study, the biosafety of MGO NPs was investigated, and the mechanism involved in ferroptosis was further explored. MGO can produce cytotoxicity in ADSCs, which is dependent on their concentration. Ferroptosis was involved in MGO NP-induced ADSC survival inhibition by increasing total ROS and lipid ROS accumulation as well as regulating the expression levels of ferroptosis-related genes and proteins. GPX4 played a critical role in the MGO NP-induced ADSC ferroptosis process, and overexpressing GPX4 suppressed ferroptosis to increase cell survival. This study provides a theoretical basis for the biosafety management of MGO NPs used in the field of biomedical treatment.

Exposure to MoS2 nanosheets or bulk activated Kruppel-like factor 4 in 3D Caco-2 spheroids in vitro and mouse intestines in vivo

MoS₂ nanosheets (NSs) are novel 2D nanomaterials (NMs) being used in many important fields. Recently, we proposed the need to evaluate the influences of NMs on Kruppel-like factors (KLFs) even if these materials are relatively biocompatible. In this study, we investigated the influences of MoS₂ NSs or bulk on KLF4 signaling pathway in 3D Caco-2 spheroids in vitro and mouse intestines in vivo. Through the analysis of our previous RNA-sequencing data, we found that exposure to MoS₂ NSs or bulk activated KLF4 expression in 3D Caco-2 spheroids. Consistently, these materials also activated KLF4-related gene ontology (GO) terms and down-regulated a panel of KLF4-downstream genes. To verify these findings, we repeatedly exposed mice to MoS₂ NSs or bulk materials via intragastrical administration (1 mg/kg bodyweight, once a day, for 4 days). It was shown that oral exposure to these materials decreased bodyweight, leading to relatively higher organ coefficients. As expected, exposure to both types of materials increased Mo elements as well as other trace elements, such as Zn, Fe, and Mn in mouse intestines. The exposure also induced morphological changes of intestines, such as shortening of intestinal villi and decreased crypt depth, which may result in decreased intestinal lipid staining. Consistent with RNA-sequencing data, we found that material exposure increased KLF4 protein staining in mouse intestines and decreased two KLF4 downstream proteins, namely extracellular signal-regulated kinase (ERK) and serine/threonine kinase (AKT). We concluded that MoS₂ materials were capable to activate KLF4-signaling pathway in intestines both in vivo and in vitro.

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.

Advantages and Potential Benefits of Using Organoids in Nanotoxicology

Organoids are microtissues that recapitulate the complex structural organization and functions of tissues and organs. Nanoparticles have several specific properties that must be considered when replacing animal models with in vitro studies, such as the formation of a protein corona, accumulation, ability to overcome tissue barriers, and different severities of toxic effects in different cell types. An increase in the number of articles on toxicology research using organoid models is related to an increase in publications on organoids in general but is not related to toxicology-based publications. We demonstrate how the quantitative assessment of toxic changes in the structure of organoids and the state of their cell collections provide more valuable results for toxicological research and provide examples of research methods. The impact of the tested materials on organoids and their differences are also discussed. In conclusion, we highlight the main challenges, the solution of which will allow researchers to approach the replacement of in vivo research with in vitro research: biobanking and standardization of the structural characterization of organoids, and the development of effective screening imaging techniques for 3D organoid cell organization.

Recent advances of nanotechnology in COVID 19: A critical review and future perspective

The global anxiety and economic crisis causes the deadly pandemic coronavirus disease of 2019 (COVID 19) affect millions of people right now. Subsequently, this life threatened viral disease is caused due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, morbidity and mortality of infected patients are due to cytokines storm syndrome associated with lung injury and multiorgan failure caused by COVID 19. Thereafter, several methodological advances have been approved by WHO and US-FDA for the detection, diagnosis and control of this wide spreadable communicable disease but still facing multi-challenges to control. Herein, we majorly emphasize the current trends and future perspectives of nano-medicinal based approaches for the delivery of anti-COVID 19 therapeutic moieties. Interestingly, Nanoparticles (NPs) loaded with drug molecules or vaccines resemble morphological features of SARS-CoV-2 in their size (60–140 nm) and shape (circular or spherical) that particularly mimics the virus facilitating strong interaction between them. Indeed, the delivery of anti-COVID 19 cargos via a nanoparticle such as Lipidic nanoparticles, Polymeric nanoparticles, Metallic nanoparticles, and Multi-functionalized nanoparticles to overcome the drawbacks of conventional approaches, specifying the site-specific targeting with reduced drug loading and toxicities, exhibit their immense potential. Additionally, nano-technological based drug delivery with their peculiar characteristics of having low immunogenicity, tunable drug release, multidrug delivery, higher selectivity and specificity, higher efficacy and tolerability switch on the novel pathway for the prevention and treatment of COVID 19.

The uses of transcriptomics and lipidomics indicated that direct contact with graphene oxide altered lipid homeostasis through ER stress in 3D human brain organoids

The potential uses of graphene-based nanomaterials (NMs) in various fields lead to the concern about their neurotoxicity, considering that graphene-based NMs are capable to cross blood brain barrier (BBB) and enter central nervous system (CNS). Although previous studies reported the possibility of graphene-based NM exposure to alter lipid homeostasis in animals or cultured neurons, recent studies suggested the need to use 3D human brain organoids for mechanism-based toxicological studies as this model might better recapitulate the complex human brains. Herein, we used multi-omics techniques to investigate the mechanisms of graphene oxide (GO) on lipid homeostasis in a novel 3D brain organoid model. We found that 50 μg/mL GO induced cytotoxicity but not superoxide. RNA-sequencing data showed that 50 μg/mL GO significantly up-regulated and down-regulated 80 and 121 genes, respectively. Furthermore, we found that GO exposure altered biological molecule metabolism pathways including lipid metabolism. Consistently, lipidomics data supported dose-dependent alteration of lipid profiles by GO in 3D brain organoids. Interestingly, co-exposure to GO and endoplasmic reticulum (ER) stress inhibitor 4-phenylbutyric acid (4-PBA) decreased most of the lipid classes compared with the exposure of GO only. We further verified that exposure to GO promoted ER stress marker GRP78 proteins, which in turn activated IRE1α/XBP-1 axis, and these changes were partially or completely inhibited by 4-PBA. These results proved that direct contact with GO disrupted lipid homeostasis through the activation of ER stress. As 3D brain organoids resemble human brains, these data might be better extrapolated to humans.

Precision Nanotoxicology in Drug Development: Current Trends and Challenges in Safety and Toxicity Implications of Customized Multifunctional Nanocarriers for Drug-Delivery Applications

The dire need for the assessment of human and environmental endangerments of nanoparticulate material has motivated the formulation of novel scientific tools and techniques to detect, quantify, and characterize these nanomaterials. Several of these paradigms possess enormous possibilities for applications in many of the realms of nanotoxicology. Furthermore, in a large number of cases, the limited capabilities to assess the environmental and human toxicological outcomes of customized and tailored multifunctional nanoparticles used for drug delivery have hindered their full exploitation in preclinical and clinical settings. With the ever-compounded availability of nanoparticulate materials in commercialized settings, an ever-arising popular debate has been egressing on whether the social, human, and environmental costs associated with the risks of nanomaterials outweigh their profits. Here we briefly review the various health, pharmaceutical, and regulatory aspects of nanotoxicology of engineered multifunctional nanoparticles in vitro and in vivo. Several aspects and issues encountered during the safety and toxicity assessments of these drug-delivery nanocarriers have also been summarized. Furthermore, recent trends implicated in the nanotoxicological evaluations of nanoparticulate matter in vitro and in vivo have also been discussed. Due to the absence of robust and rigid regulatory guidelines, researchers currently frequently encounter a larger number of challenges in the toxicology assessment of nanocarriers, which have also been briefly discussed here. Nanotoxicology has an appreciable and significant part in the clinical translational development as well as commercialization potential of nanocarriers; hence these aspects have also been touched upon. Finally, a brief overview has been provided regarding some of the nanocarrier-based medicines that are currently undergoing clinical trials, and some of those which have recently been commercialized and are available for patients. It is expected that this review will instigate an appreciable interest in the research community working in the arena of pharmaceutical drug development and nanoformulation-based drug delivery.

Toxicity of metal-based nanoparticles: Challenges in the nano era

With the rapid progress of nanotechnology, various nanoparticles (NPs) have been applicated in our daily life. In the field of nanotechnology, metal-based NPs are an important component of engineered NPs, including metal and metal oxide NPs, with a variety of biomedical applications. However, the unique physicochemical properties of metal-based NPs confer not only promising biological effects but also pose unexpected toxic threats to human body at the same time. For safer application of metal-based NPs in humans, we should have a comprehensive understanding of NP toxicity. In this review, we summarize our current knowledge about metal-based NPs, including the physicochemical properties affecting their toxicity, mechanisms of their toxicity, their toxicological assessment, the potential strategies to mitigate their toxicity and current status of regulatory movement on their toxicity. Hopefully, in the near future, through the convergence of related disciplines, the development of nanotoxicity research will be significantly promoted, thereby making the application of metal-based NPs in humans much safer.

Graphdiyne-Related Materials in Biomedical Applications and Their Potential in Peripheral Nerve Tissue Engineering

Graphdiyne (GDY) is a new member of the family of carbon-based nanomaterials with hybridized carbon atoms of sp and sp², including α, β, γ, and (6,6,12)-GDY, which differ in their percentage of acetylene bonds. The unique structure of GDY provides many attractive features, such as uniformly distributed pores, highly π-conjugated structure, high thermal stability, low toxicity, biodegradability, large specific surface area, tunable electrical conductivity, and remarkable thermal conductivity. Therefore, GDY is widely used in energy storage, catalysis, and energy fields, in addition to biomedical fields, such as biosensing, cancer therapy, drug delivery, radiation protection, and tissue engineering. In this review, we first discuss the synthesis of GDY with different shapes, including nanotubes, nanowires, nanowalls, and nanosheets. Second, we present the research progress in the biomedical field in recent years, along with the biodegradability and biocompatibility of GDY based on the existing literature. Subsequently, we present recent research results on the use of nanomaterials in peripheral nerve regeneration (PNR). Based on the wide application of nanomaterials in PNR and the remarkable properties of GDY, we predict the prospects and current challenges of GDY-based materials for PNR.

Simulating human gastrointestinal motility in dynamic in vitro models

The application of dynamic in vitro gastrointestinal (GI) models has grown in popularity to understand the impact of food structure and composition on human health. Given that GI motility is integral to digestion and absorption, a predictive in vitro model should faithfully replicate the motility patterns and motor functions in vivo. In this review, typical characteristics of gastric and small intestinal motility in humans as well as the biomechanical and hydrodynamic events pertinent to gut motility are summarized. The simulation of GI motility in the presently existing dynamic in vitro models is discussed from an engineering perspective and categorized into hydraulic, piston/probe-driven, roller-driven, pneumatic, and other systems. Each system and its representative models are evaluated in terms of their motility patterns, the key hydrodynamic characteristics concerning gut motility, their performance in simulating the key physiological events, and their ability to establish in vitro-in vivo correlations. Practical Application: The review paper provided useful information in the design of dynamic GI models and the simulation of human gastric and small intestinal motility which are important for understanding food and health.

Biomimetic Keratin-Coated Gold Nanoparticles for Photo-Thermal Therapy in a 3D Bioprinted Glioblastoma Tumor Model

Before entering human clinical studies to evaluate their safety and effectiveness, new drugs and novel medical treatments are subject to extensive animal testing that are expensive and time-consuming. By contrast, advanced technologies enable the development of animal-free models that allow the efficacy of innovative therapies to be studied without sacrificing animals, while providing helpful information and details. We report on the powerful combination of 3D bioprinting (3DB) and photo-thermal therapy (PTT) applications. To this end, we realize a 3DB construct consisting of glioblastoma U87-MG cells in a 3D geometry, incorporating biomimetic keratin-coated gold nanoparticles (Ker-AuNPs) as a photo-thermal agent. The resulting plasmonic 3DB structures exhibit a homogeneous cell distribution throughout the entire volume while promoting the localization of Ker-AuNPs within the cells. A 3D immunofluorescence assay and transmission electron microscopy (TEM) confirm the uniform distribution of fluorescent-labeled Ker-AuNPs in the volume and their capability to enter the cells. Laser-assisted (λ = 532 nm) PTT experiments demonstrate the extraordinary ability of Ker-AuNPs to generate heating, producing the highest temperature rise of about 16 °C in less than 2 min.

Design, Synthesis, and Antitumor Evaluation of Novel Mono-Carbonyl Curcumin Analogs in Hepatocellular Carcinoma Cell

Curcumin is a polyphenolic natural product that has promising anticancer properties. However, its clinical utility is limited by its chemical instability and poor metabolic properties. In this paper, a series of new curcumin analogs were synthesized and found to be potent antiproliferative agents against the HepG2 cell line by MTT assay. In general, Group B with single ketone and group C with chalcone were markedly more cytotoxic than group A with diketone. Compound B5 was found as the most potent analog (IC₅₀ = 11.33 μM) compared to curcumin (IC₅₀ = 32.83 μM) and the mechanism of its cytotoxicity was investigated. The result of the wound healing assay indicated B5 strong potential to suppress HepG2 cell migration in a dose- and time-dependent manner. Subsequent assays (including JC-1 staining, Bcl-2, and caspase 3 protein levels by Western blotting) confirmed that B5 exposure induced apoptosis in HepG2 cells. Curcumin-induced comprehensive transcriptomes profile, Western blotting, molecular docking, and molecular dynamics analysis showed that the mechanism may relate to the regulation of cellular metabolic process and the expression of AKT protein. Taken together, we could conclude that curcumin and its analogs induced HepG2 cell proliferation, migration, and apoptosis via AKT signaling pathway and the mitochondrial death pathway. This study could lay the foundation for optimizing curcumin and provide valuable information for finding novel anti-HCC drugs.

Nutrient molecule corona: An update for nanomaterial-food component interactions

The adsorption of biological molecules to nanomaterials (NMs) will significantly impact NMs' behavior in complex microenvironments. Previously we proposed the need to consider the interactions between food components and NMs for the evaluation of oral toxicity of NMs. This review updated this concept as nutrient molecule corona, that the adsorption of nutrient molecules alters the uptake of nutrient molecules and/or NMs, as well as the signaling pathways to induce a combined toxicity due to the biologically active nature of nutrient molecules. Even with the presence of protein corona, nutrient molecules may still bind to NMs to change the identities of NMs in vivo. Furthermore, this review proposed the binding of excessive nutrient molecules to NMs to induce a combined toxicity under pathological conditions such as metabolic diseases. The structures of nutrient molecules and physicochemical properties of NMs determine nutrient molecule corona formation, and these aspects should be considered to limit the unwanted effects brought by nutrient molecule corona. In conclusion, similar to other biological molecule corona, the formation of nutrient molecule corona due to the presence of food components or excessive nutrient molecules in pathophysiological microenvironments will alter the behaviors of NMs.

Intratracheal instillation of graphene oxide decreases anti-virus responses and lipid contents via suppressing Toll-like receptor 3 in mouse livers

Recent studies revealed a causal relationship between Toll-like receptors (TLRs) and lipid droplet biogenesis. Interestingly, it has been reported before that nanomaterials (NMs) were capable to modulate TLRs, but it remains unclear if NMs could affect lipid levels via TLR signaling pathways. In this study, we investigated the influences of airway exposure to graphene oxide (GO) on TLR3 signaling pathways and lipid levels in mouse livers. Intratracheal instillation of GO (0.1, 1, and 5 mg/kg, once a day, totally 5 days) induced inflammatory cell infiltrations as indicated by hematoxylin-eosin (H&E) staining and fibrosis as indicated by Masson staining in lungs, accompanying with decreased TLR3 proteins. Consistently, a TLR3-regulated anti-virus protein, namely interferon induced protein with tetratricopeptide repeats 1 (IFIT1), as well as two TLR3-regulated lipid proteins, namely radical S-adenosyl methionine domain containing 2 (RSAD2) and perilipin 2 (PLIN2), were decreased in lungs. The protein levels of interferon-β in serum were also decreased. In livers, GO exposure induced disorganization of liver cells but not fibrosis. In agreement with the trends observed in lungs, TLR3, IFIT1, RSAD2, and PLIN2 proteins were decreased in livers. As a possible consequence, GO exposure dose-dependently decreased lipid levels in livers as indicated by oil red O and BODIPY 493/503 staining. We concluded that airway exposure to GO decreased anti-virus responses and lipid levels in mouse livers via the suppression of TLR3.

STAT3-EMT axis in tumors: modulation of cancer metastasis, stemness and therapy response

Epithelial-to-mesenchymal transition (EMT) mechanism is responsible for metastasis of tumor cells and their spread to various organs and tissues of body, providing undesirable prognosis. In addition to migration, EMT increases stemness and mediates therapy resistance. Hence, pathways involved in EMT regulation should be highlighted. STAT3 is an oncogenic pathway that can elevate growth rate and migratory ability of cancer cells and induce drug resistance. The inhibition of STAT3 signaling impairs cancer progression and promotes chemotherapy-mediated cell death. Present review focuses on STAT3 and EMT interaction in modulating cancer migration. First of all, STAT3 is an upstream mediator of EMT and is able to induce EMT-mediated metastasis in brain tumors, thoracic cancers and gastrointestinal cancers. Therefore, STAT3 inhibition significantly suppresses cancer metastasis and improves prognosis of patients. EMT regulators such as ZEB1/2 proteins, TGF-β, Twist, Snail and Slug are affected by STAT3 signaling to stimulate cancer migration and invasion. Different molecular pathways such as miRNAs, lncRNAs and circRNAs modulate STAT3/EMT axis. Furthermore, we discuss how STAT3 and EMT interaction affects therapy response of cancer cells. Finally, we demonstrate targeting STAT3/EMT axis by anti-tumor agents and clinical application of this axis for improving patient prognosis.

Nanosafety: An Evolving Concept to Bring the Safest Possible Nanomaterials to Society and Environment

The use of nanomaterials has been increasing in recent times, and they are widely used in industries such as cosmetics, drugs, food, water treatment, and agriculture. The rapid development of new nanomaterials demands a set of approaches to evaluate the potential toxicity and risks related to them. In this regard, nanosafety has been using and adapting already existing methods (toxicological approach), but the unique characteristics of nanomaterials demand new approaches (nanotoxicology) to fully understand the potential toxicity, immunotoxicity, and (epi)genotoxicity. In addition, new technologies, such as organs-on-chips and sophisticated sensors, are under development and/or adaptation. All the information generated is used to develop new in silico approaches trying to predict the potential effects of newly developed materials. The overall evaluation of nanomaterials from their production to their final disposal chain is completed using the life cycle assessment (LCA), which is becoming an important element of nanosafety considering sustainability and environmental impact. In this review, we give an overview of all these elements of nanosafety.

The uses of 3D human brain organoids for neurotoxicity evaluations: A review

Neurotoxicity studies aim at understanding the toxic effects and mechanisms of toxicants to human central nervous systems (CNS). However, human brains are the most complex organs, whereas the most commonly used models, such as 2D cell cultures and animal brains, are probably too simple to predict the responses of human brains. Embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs)-based 3D human brain organoids hold unprecedented promise for the understanding of neurodevelopment and brain disease development. This review summarizes recent advances of using 3D human brain organoids for neurotoxicity studies. Comparative studies showed that 3D human brain organoids could support the findings obtained by animal or cohort studies, indicating that 3D human brain organoids are reliable models to evaluate the developmental neurotoxicity. 3D human brain organoids have been used to understand the toxicological mechanisms by using both conventional toxicological methods to investigate the signaling pathway changes as well as single cell RNA-sequencing to understand the neuron diversity. Some studies also used brain organoids carrying gene mutations or with virus infections to understand the toxicological responses of brains under diseased conditions. Although there are still limitations associated, 3D human brain organoids are promising tools for future neurotoxicity studies.

Effects of epigallocatechin gallate on the stability, dissolution and toxicology of ZnO nanoparticles

Previously we reported the cytoprotective effects of polyphenols rich in hydroxyl groups against ZnO nanoparticles (NPs). This study used RNA-sequencing to evaluate the toxicity of ZnO NPs and epigallocatechin gallate (EGCG) to 3D Caco-2 spheroids. EGCG altered the colloidal stability of ZnO NPs, shown as the changes of atomic force microscopic height, solubility in cell culture medium, and hydrodynamic sizes. EGCG almost completely reversed ZnO NP-induced cytotoxicity, and consistently, alleviated ZnO NP-induced gene ontology (GO) terms and genes related with apoptosis. EGCG also modestly decreased intracellular Zn ions and changed GO terms and genes related with endocytosis/exocytosis in ZnO NP-exposed spheroids. Meanwhile, EGCG changed ZnO NP-induced alteration of GO terms and genes related with the functions of mitochondria, endoplasmic reticulum and lysosomes. We concluded that EGCG alleviated the cytotoxicity of ZnO NPs to 3D Caco-2 spheroids by altering NPs' colloidal properties and the pathways related with internalization and organelle dysfunction.

TiO2 nanosheets promote the transformation of vascular smooth muscle cells into foam cells in vitro and in vivo through the up-regulation of nuclear factor kappa B subunit 2

Titanium dioxide (TiO₂) nanomaterials have been shown to promote atherosclerosis through endothelial dysfunction. This study investigated the toxicity of TiO₂ nanosheets (NSs) to vascular smooth muscle cells (VSMCs), one of the pivotal cells involved in all stages of atherosclerosis. Only a high concentration of TiO₂ NSs (128 μg/mL) modestly induced cytotoxicity by decreasing thiols. RNA-sequencing data revealed that 64 μg/mL TiO₂ NSs significantly down-regulated 94 genes and up-regulated 174 genes, respectively. Gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to SMC function and lipid metabolism were altered. TiO₂ NSs increased nuclear factor kappa B subunit 2 (NFKB2), which led to a decrease in VSMC marker actin alpha 2, smooth muscle (ACTA2). On the other hand, macrophage marker CD36 and fatty acid synthase (FASN) proteins were increased. Additionally, TiO₂ NSs induced inflammatory cytokines and lipid accumulation, and these effects were curtailed by NFKB inhibitor - triptolide. Furthermore, repeated TiO₂ NS injection (5 mg/kg BW, once a day for 5 continuous days) into ICR mice led to increased NFKB2, CD36 and FASN, with a decreased ACTA2. Our results suggested that TiO₂ NSs promoted the transformation of VSMCs into foam cells through the up-regulation of NFKB2.

Nanoparticle-Induced m6A RNA Modification: Detection Methods, Mechanisms and Applications

With the increasing application of nanoparticles (NPs) in medical and consumer applications, it is necessary to ensure their safety. As m⁶A (N⁶-methyladenosine) RNA modification is one of the most prevalent RNA modifications involved in many diseases and essential biological processes, the relationship between nanoparticles and m⁶A RNA modification for the modulation of these events has attracted substantial research interest. However, there is limited knowledge regarding the relationship between nanoparticles and m⁶A RNA modification, but evidence is beginning to emerge. Therefore, a summary of these aspects from current research on nanoparticle-induced m⁶A RNA modification is timely and significant. In this review, we highlight the roles of m⁶A RNA modification in the bioimpacts of nanoparticles and thus elaborate on the mechanisms of nanoparticle-induced m⁶A RNA modification. We also summarize the dynamic regulation and biofunctions of m⁶A RNA modification. Moreover, we emphasize recent advances in the application perspective of nanoparticle-induced m⁶A RNA modification in medication and toxicity of nanoparticles to provide a potential method to facilitate the design of nanoparticles by deliberately tuning m⁶A RNA modification.

Graphene oxide links alterations of anti-viral signaling pathways with lipid metabolism via suppressing TLR3 in vascular smooth muscle cells

Vascular smooth muscle cells (VSMCs), the main cells constructing blood vessels, are important in the regulation of the pathophysiology of vascular systems; however, relatively few studies have investigated the influence of nanomaterials (NMs) on VSMCs.

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.

The cytotoxicity of zinc oxide nanoparticles to 3D brain organoids results from excessive intracellular zinc ions and defective autophagy

Although the neurotoxicity of ZnO nanoparticles (NPs) has been evaluated in animal and nerve cell culture models, these models cannot accurately mimic human brains. Three-dimensional (3D) brain organoids based on human-induced pluripotent stem cells have been developed to study the human brains, but this model has rarely been used to evaluate NP neurotoxicity. We used 3D brain organoids that express cortical layer proteins to investigate the mechanisms of ZnO NP-induced neurotoxicity. Cytotoxicity caused by high levels of ZnO NPs (64 μg/mL) correlated with high intracellular Zn ion levels but not superoxide levels. Exposure to a non-cytotoxic concentration of ZnO NPs (16 μg/mL) increased the autophagy-marker proteins LC3B-II/I but decreased p62 accumulation, whereas a cytotoxic concentration of ZnO NPs (64 μg/mL) decreased LC3B-II/I proteins but did not affect p62 accumulation. Fluorescence micro-optical sectioning tomography revealed that 64 μg/mL ZnO NPs led to decreases in LC3B proteins that were more obvious at the outer layers of the organoids, which were directly exposed to the ZnO NPs. In addition to reducing LC3B proteins in the outer layers, ZnO NPs increased the number of micronuclei in the outer layers but not the inner layers (where LC3B proteins were still expressed). Adding the autophagy flux inhibitor bafilomycin A1 to ZnO NPs increased cytotoxicity and intracellular Zn ion levels, but adding the autophagy inducer rapamycin only slightly decreased cellular Zn ion levels. We conclude that high concentrations of ZnO NPs are cytotoxic to 3D brain organoids via defective autophagy and intracellular accumulation of Zn ions.

Comparison of P25 and nanobelts on Kruppel-like factor-mediated nitric oxide pathways in human umbilical vein endothelial cells

Recently, we reported that titanium dioxide (TiO₂ ) materials activated endothelial cells via Kruppel-like factor (KLF)-mediated nitric oxide (NO) dysfunction, but the roles of physical properties of materials are not clear. In this study, we prepared nanobelts from P25 particles and compared their adverse effects to human umbilical vein endothelial cells (HUVECs). TiO₂ nanobelts had belt-like morphology but comparable surface areas as P25 particles. When applied to HUVECs, P25 particles or nanobelts did not induce cytotoxicity, although nanobelts were much more effective to increase intracellular Ti element concentrations compared the same amounts of P25 particles. Only nanobelts significantly induced THP-1 adhesion onto HUVECs. Consistently, nanobelts were more significant to induce the expression of intracellular adhesion molecule-1 (ICAM1) and the release of soluble ICAM-1 (sICAM-1), indicating that nanobelts were more potent to induce endothelial activation in vitro. As the mechanisms for endothelial activation, both P25 and nanobelts reduced the generation of intracellular NO as well as the expression of NO regulators KLF2 and KLF4. Combined, the results from this study indicated that the different morphologies of P25 particles and nanobelts only changed their internalization into HUVECs but showed minimal impact on KLF-mediated NO signaling pathways.

Autophagy up-regulated by MEK/ERK promotes the repair of DNA damage caused by aflatoxin B1

Aflatoxin B1 (AFB1), a kind of mycotoxin, exerts its cytotoxicity by increasing the oxidative damage of target organs, especially the liver. In vivo and in vitro experiments were carried out to elucidate the toxic mechanism of AFB1. The results of MTT, cloning-formation, flow cytometry, immunocytochemistry, Reverse transcription PCR (RT-PCR) and western blot showed that AFB1 activated NOX2 gp91 phox, inhibited proliferation and migration, and blocked cell cycle at G0/G1 period of HHL-5 cells. Autophagy promoted the repair of NOX2-dependent DNA damage. NOX2/gp91 phox mainly activates MEK/ERK pathway and then up-regulates autophagy. In vivo experiments have shown that AFB1 (0.75 mg/kg daily orally, 4 weeks) had no significant changes in the size and shape of the liver in mice. However, these treatments lead to structural abnormalities of hepatocytes and DNA damage. In summary, AFB1 caused intracellular oxidative stress and DNA damage, NOX2/gp91-phox activates the MEK/ERK pathway, and upregulated autophagy to promote the repair of DNA damage. We concluded that by increasing the level of autophagy, the ability of anti-AFB1 toxicity of liver can be increased.

Comparison of multi-walled carbon nanotubes and halloysite nanotubes on lipid profiles in human umbilical vein endothelial cells

Tubular nanomaterials (NMs), such as multi-walled carbon nanotubes (MWCNTs) and halloysite nanotubes (HNTs), may be used in biomedicine, but previous studies showed that MWCNTs induced toxicity to endothelial cells (ECs). However, the influence of tubular NMs on EC lipid profiles has gained little attention, probably because ECs are not traditionally considered to be involved in regulating lipid homeostasis. This study compared the different effects of MWCNTs and HNTs on lipid profile changes in human umbilical vein ECs (HUVECs). The results showed that MWCNTs but not HNTs of the same mass concentrations induced cytotoxicity, ultrastuctural changes and intracellular thiol depletion. Meanwhile, only MWCNTs promoted lipid accumulation due to the induction of ER stress leading to up-regulation of fatty acid synthase (FASN). Interestingly, lipidomics results showed that the main lipid classes induced by MWCNTs but not HNTs were ceramide (Cer) and phosphatidylinositol (PI), with most of the lipid classes unaltered or even decreased after NM exposure. Then, extra Cer and PI were added to explore the implications of increase of these lipids. Adding Cer promoted the cytotoxicity of MWCNTs to HUVECs, indicating the lipotoxic role of Cer. Whereas adding PI partially increased intracellular NO and decreased interleukin-6 (IL-6) release due to MWCNT exposure, indicating the signaling role of PI. These results indicated novel roles of lipid dysfunction in NM-induced toxicity to ECs, even though ECs are not the professional cells for controlling lipid homeostasis.

Effect of magnetic graphene oxide on cellular behaviors and osteogenesis under a moderate static magnetic field

The biological behaviors of magnetic graphene oxide (MGO) in a static magnetic field (SMF) are unknown. The current study is to investigate the cellular behaviors, osteogenesis and the mechanism in BMSCs treated with MGO combined with an SMF. Results showed that the synthetic MGO particles were bio-compatible and could significantly improve the osteogenesis of BMSCs under SMFs, as verified by elevated alkaline phosphatase activity, mineralized nodule formation, and expressions of mRNA and protein levels. Under SMF at the same intensity, the addition of graphene oxide to Fe₃O₄ could increase the osteogenic ability of BMSCs. The Wnt/β-catenin pathway was indicated to be related to the MGO-driven osteogenic behavior of the BMSCs under SMF. Taken together, our findings suggested that MGO under an SMF could promote osteogenesis in BMSCs through the Wnt/β-catenin pathway and hence should attract more attention for practical applications in bone tissue regeneration.

A Tissue-Engineered Tracheobronchial In Vitro Co-Culture Model for Determining Epithelial Toxicological and Inflammatory Responses

Translation of novel inhalable therapies for respiratory diseases is hampered due to the lack of in vitro cell models that reflect the complexity of native tissue, resulting in many novel drugs and formulations failing to progress beyond preclinical assessments. The development of physiologically-representative tracheobronchial tissue analogues has the potential to improve the translation of new treatments by more accurately reflecting in vivo respiratory pharmacological and toxicological responses. Herein, advanced tissue-engineered collagen hyaluronic acid bilayered scaffolds (CHyA-B) previously developed within our group were used to evaluate bacterial and drug-induced toxicity and inflammation for the first time. Calu-3 bronchial epithelial cells and Wi38 lung fibroblasts were grown on either CHyA-B scaffolds (3D) or Transwell® inserts (2D) under air liquid interface (ALI) conditions. Toxicological and inflammatory responses from epithelial monocultures and co-cultures grown in 2D or 3D were compared, using lipopolysaccharide (LPS) and bleomycin challenges to induce bacterial and drug responses in vitro. The 3D in vitro model exhibited significant epithelial barrier formation that was maintained upon introduction of co-culture conditions. Barrier integrity showed differential recovery in CHyA-B and Transwell® epithelial cultures. Basolateral secretion of pro-inflammatory cytokines to bacterial challenge was found to be higher from cells grown in 3D compared to 2D. In addition, higher cytotoxicity and increased basolateral levels of cytokines were detected when epithelial cultures grown in 3D were challenged with bleomycin. CHyA-B scaffolds support the growth and differentiation of bronchial epithelial cells in a 3D co-culture model with different transepithelial resistance in comparison to the same co-cultures grown on Transwell® inserts. Epithelial cultures in an extracellular matrix like environment show distinct responses in cytokine release and metabolic activity compared to 2D polarised models, which better mimic in vivo response to toxic and inflammatory stimuli offering an innovative in vitro platform for respiratory drug development.

A comparative study of toxicity of graphdiyne and graphene oxide to human umbilical vein endothelial cells

The success of graphene oxide (GO) has attracted extensive research interests in developing novel 2D nanomaterials (NMs). Graphdiyne (GDY) is a new member of carbon-based 2D NMs possessing sp- and sp² -hybridized carbon atoms. However, the toxicity of GDY is less investigated as GO. In this study, we compared the toxicity of GDY and GO with human umbilical vein endothelial cells (HUVECs). Exposure to up to 100-μg/ml GDY and GO induced cytotoxicity, but there was no statistically significant difference between GDY and GO. At noncytotoxic concentration, 25-μg/ml GDY or GO led to the internalization of NMs, typically in cytoplasm but not in nuclei. Only GO but not GDY significantly increased THP-1 adhesion onto NM-exposed HUVECs. Meanwhile, compared with GDY, GO more effectively promoted the release of soluble intracellular cell adhesion molecule-1 (sICAM-1), indicating the differential effects of GDY and GO on endothelial activation. Neither GDY nor GO induced intracellular superoxide. However, GO significantly promoted the expression of endoplasmic reticulum (ER) stress genes activating transcription factor 4 (ATF4) and X-box binding protein 1 spliced (XBP-1s), as well pyroptosis genes NLR family pyrin domain containing 3 (NLRP3) and gasdermin D (GSDMD), whereas GDY did not show this effect. The results suggested that GDY and GO could be internalized into HUVECs leading to cytotoxic effects. However, GO was more potent to activate endothelial activation probably due to the activation of ER stress and pyroptosis genes.

Potential roles of Kruppel-like factors in mediating adverse vascular effects of nanomaterials: A review

The development of nanotechnology leads to the exposure of human beings to nanomaterials (NMs), and there is a health concern about the adverse vascular effects of NMs. Current data from epidemiology, controlled human exposure, and animal studies suggested that exposure to NMs could induce cardiopulmonary effects. In support of in vivo findings, in vitro studies showed that direct contact of vascular cells with NMs could induce endothelial cell (EC) activation and promote macrophage foam cell formation, although only limited studies showed that NMs could damage vascular smooth muscle cells and promote their phenotypic switch. It has been proposed that NMs induced adverse vascular effects via different mechanisms, but it is still necessary to understand the upstream events. Kruppel-like factors (KLFs) are a set of C2H2 zinc finger transcription factors (TFs) that can regulate various aspects of vascular biology, but currently, the roles of KLF2 in mediating the adverse vascular effects of NMs have gained little attention by toxicologists. This review summarized current knowledge about the adverse vascular effects of NMs and proposed the potential roles of KLFs in mediating these effects based on available data from toxicological studies as well as the current understanding about KLFs in vascular biology. Finally, the challenges in investigating the role of KLFs in vascular toxicology were also summarized. Considering the important roles of KLFs in vascular biology, further studies are needed to understand the influence of NMs on KLFs and the downstream events.

Three-Dimensional in vitro Models of Healthy and Tumor Brain Microvasculature for Drug and Toxicity Screening

Tissue vascularization is essential for its oxygenation and the homogenous diffusion of nutrients. Cutting-edge studies are focusing on the vascularization of three-dimensional (3D) in vitro models of human tissues. The reproduction of the brain vasculature is particularly challenging as numerous cell types are involved. Moreover, the blood-brain barrier, which acts as a selective filter between the vascular system and the brain, is a complex structure to replicate. Nevertheless, tremendous advances have been made in recent years, and several works have proposed promising 3D in vitro models of the brain microvasculature. They incorporate cell co-cultures organized in 3D scaffolds, often consisting of components of the native extracellular matrix (ECM), to obtain a micro-environment similar to the in vivo physiological state. These models are particularly useful for studying adverse effects on the healthy brain vasculature. They provide insights into the molecular and cellular events involved in the pathological evolutions of this vasculature, such as those supporting the appearance of brain cancers. Glioblastoma multiform (GBM) is the most common form of brain cancer and one of the most vascularized solid tumors. It is characterized by a high aggressiveness and therapy resistance. Current conventional therapies are unable to prevent the high risk of recurrence of the disease. Most of the new drug candidates fail to pass clinical trials, despite the promising results shown in vitro. The conventional in vitro models are unable to efficiently reproduce the specific features of GBM tumors. Recent studies have indeed suggested a high heterogeneity of the tumor brain vasculature, with the coexistence of intact and leaky regions resulting from the constant remodeling of the ECM by glioma cells. In this review paper, after summarizing the advances in 3D in vitro brain vasculature models, we focus on the latest achievements in vascularized GBM modeling, and the potential applications for both healthy and pathological models as platforms for drug screening and toxicological assays. Particular attention will be paid to discuss the relevance of these models in terms of cell-cell, cell-ECM interactions, vascularization and permeability properties, which are crucial parameters for improving in vitro testing accuracy.

Comparison of cytotoxicity of Ag/ZnO and Ag@ZnO nanocomplexes to human umbilical vein endothelial cells in vitro

Novel metal and metal oxide-based nanocomplexes are being developed due to their superior properties compared with nanoparticles (NPs) based on single composition. In this study, we synthesized Ag-coated ZnO (Ag/ZnO) and Ag-doped ZnO (Ag@ZnO) NPs. The cytotoxicity and mechanisms associated with the synthesized NPs were investigated to understand the influence of Ag positions on biocompatibility of the NPs. After exposure to human umbilical vein endothelial cells (HUVECs), Ag/ZnO, Ag@ZnO, and ZnO NPs all significantly induced cytotoxicity, but the cytotoxic effects of Ag/ZnO and Ag@ZnO NPs were more modest in comparison with ZnO NPs. At cytotoxic concentrations, all NPs significantly induced intracellular Zn ions, which suggested a role of excessive Zn ions on cytotoxicity of NPs. All types of NPs significantly induced the expression of endoplasmic reticulum (ER) stress genes including DNA damage-inducible transcript 3 (DDIT3), X-box binding protein 1 (XBP-1), and ER to nucleus signaling 1 (ERN1), but Ag/ZnO and Ag@ZnO NPs were less effective to induce DDIT3 and XBP-1 expression compared with ZnO NPs. Not surprisingly, only ZnO NPs significantly induced the expression of caspase 3. Combined, the results from this study showed that Ag/ZnO and Ag@ZnO NPs were less cytotoxic and less potent to induce ER stress gene expression compared with ZnO NPs, but there were no significant differences between Ag/ZnO and Ag@ZnO NPs. Our results may provide novel understanding about the biocompatibility of Ag-ZnO nanocomplexes.

Near-infrared emission Cu, N-doped carbon dots for human umbilical vein endothelial cell labeling and their biocompatibility in vitro

Quantum dots (QDs) are luminescent semiconductor nanomaterials (NMs) with various biomedical applications, but the high toxicity associated with traditional QDs, such as Cd-based QDs, limits their uses in biomedicine. As such, the development of biocompatible metal-free QDs has gained extensive research interests. In this study, we synthesized near-infrared emission Cu, N-doped carbon dots (CDs) with optimal emission at 640 nm and a fluorescence quantum yield of 27.1% (in N,N-dimethylformamide [DMF]) by solvothermal method using o-phenylenediamine and copper acetate monohydrate. We thoroughly characterized the CDs and showed that they were highly fluorescent and stable under different conditions, although in highly acidic (pH = 1-2) or alkaline (pH = 12-13) solutions, a redshift or blueshift of fluorescence emission peak of Cu, N-doped CDs was also observed. When exposed to human umbilical vein endothelial cells (HUVECs), Cu, N-doped CDs only significantly induced cytotoxicity at very high concentrations (100 or 200 μg/ml), but their cytotoxicity appeared to be comparable with carbon black (CB) nanoparticles (NPs) at the same mass concentrations. As the mechanisms, 200 μg/ml Cu, N-doped CDs and CB NPs promoted endoplasmic reticulum (ER) stress proteins IRE1α and chop, leading to increased cleaved caspase 3/pro-caspase 3 ratio, but CB NPs were more effective. At noncytotoxic concentration (50 μg/ml), Cu, N-doped CDs successfully labeled HUVECs. In summary, we successfully prepared highly fluorescent and relatively biocompatible CDs to label HUVECs in vitro.