Evaluation of toxicity of halloysite nanotubes and multi-walled carbon nanotubes to endothelial cells in vitro and blood vessels in vivo

Effects of multi-walled carbon nanotubes and halloysite nanotubes on plasma lipid profiles and autophagic lipolysis pathways in mouse aortas and hearts

Multi-walled carbon nanotubes (MWCNTs) and halloysite nanotubes (HNTs) are widely used tubular-structured nanomaterials (NMs), but their cardiovascular effects are not clear. This study compared the effects of MWCNTs and HNTs on lipid profiles in mouse plasma and gene expression profiles in aortas and hearts. Mice were intravenously injected with 50 μg NMs, once a day, for 5 days. Then, the plasma was collected for lipidomics analysis, and aortas and hearts were collected for RNA-sequencing analysis. While MWCNTs or HNTs did not induce obvious pathological changes in aortas or hearts, the lipid profiles in mouse plasma were altered. Further analysis revealed that MWCNTs more effectively upregulated sphingolipids and sterol lipids, whereas HNTs more effectively upregulated glycerophospholipids and fatty acyls. Consistently, RNA-sequencing data indicated that MWCNTs and HNTs altered signaling pathways related with lipid synthesis and metabolism, as well as those related with endoplasmic reticulum, lysosomes and autophagy, more significantly in aortas than in hearts. We further verified the changes of proteins involved in autophagic lipolysis, that MWCNTs were more effectively to suppress the autophagic biomarker LC3, whereas HNTs were more effectively to affect lipid metabolism proteins. These results may provide novel understanding about the influences of MWCNTs and HNTs on lipid profiles and lipid signaling pathways in cardiovascular systems. Importantly, previous studies considered HNTs as biocompatible materials, but the results from this study suggested that both MWCNTs and HNTs were capable to affect lipid profiles and autophagic lipolysis pathways in cardiovascular systems, although their exact influences were different.

The Horizons of Medical Mineralogy: Structure-Bioactivity Relationship and Biomedical Applications of Halloysite Nanoclay

Medical mineralogy explores the interactions between natural minerals and living organisms such as cells, tissues, and organs and develops therapeutic and diagnostic applications in drug delivery, medical devices, and healthcare materials. Many minerals (especially clays) have been recognized for pharmacological activities and therapeutic potential. Halloysite clay (Chinese medicine name: Chishizhi), manifested as one-dimensional aluminum silicate nanotubes (halloysite nanotubes, HNTs), has gained applications in hemostasis, wound repair, gastrointestinal diseases, tissue engineering, detection and sensing, cosmetics, and daily chemicals formulations. Various biomedical applications of HNTs are derived from hollow tubular structures, high mechanical strength, good biocompatibility, bioactivity, and unique surface characteristics. This natural nanomaterial is safe, abundantly available, and may be processed with environmentally safe green chemistry methods. This review describes the structure and physicochemical properties of HNTs relative to bioactivity. We discuss surface area, porosity and surface defects, hydrophilicity, heterogeneity and charge of external and internal surfaces, as well as biosafety. The paper provides comprehensive guidance for the development of this tubule nanoclay and its advanced biomedical applications for clinical diagnosis and therapy.

Effects of Halloysite Nanotubes and Multi-walled Carbon Nanotubes on Kruppel-like Factor 15-Mediated Downstream Events in Mouse Hearts After Intravenous Injection

Halloysite nanotubes (HNTs) are nanomaterials (NMs) derived from natural clays and have been considered as biocompatible NMs for biomedical uses. However, the cardiovascular toxicity of HNTs has not been thoroughly investigated. In this study, we compared the cardiotoxicity of HNTs and multi-walled carbon nanotubes (MWCNTs), focusing on the changes in Kruppel-like factor (KLF)-mediated signaling pathways. Mice were intravenously injected with 50 µg NMs, once a day, for 5 days, and then mouse hearts were removed for experiments. While HNTs or MWCNTs did not induce obvious pathological changes, RNA-sequencing data suggested the alterations of KLF gene expression. We further confirmed an increase of Klf15 positive cells, accompanied by changes in Klf15-related gene ontology (GO) terms. We noticed that most of the changed GO terms are related with the regulation of gene expression, and we confirmed that the NMs increased myoneurin (Mynn) but decreased snail family transcriptional repressor 1 (Snai1), two transcription factors (TFs) related with Klf15. Besides, the changed GO terms also include metal ion binding and positive regulation of glucose import, and we verified an increase of phosphoenolpyruvate carboxykinase 1 (Pck1) and insulin receptor (Insr). However, HNTs and MWCNTs only showed minimal impact on cell death signaling pathways, and no increase in apoptotic sites was observed after NM treatment. We concluded that intravenous administration of HNTs and MWCNTs activated a protective TF, namely Klf15 in mouse aortas, to alter gene expression and signaling pathways related with metal ion binding and glucose import.

Micropatterning of biologically derived surfaces with functional clay nanotubes

Micropatterning of biological surfaces performed via assembly of nano-blocks is an efficient design method for functional materials with complex organic-inorganic architecture. Halloysite clay nanotubes with high aspect ratios and empty lumens have attracted widespread interest for aligned biocompatible composite production. Here, we give our vision of advances in interfacial self-assembly techniques for these natural nanotubes. Highly ordered micropatterns of halloysite, such as coffee rings, regular strips, and concentric circles, can be obtained through high-temperature evaporation-induced self-assembly in a confined space and shear-force brush-induced orientation. Assembly of these clay nanotubes on biological surfaces, including the coating of human or animal hair, wool, and cotton, was generalized with the indication of common features. Halloysite-coated microfibers promise new approaches in cotton and hair dyeing, medical hemostasis, and flame-retardant tissue applications. An interfacial halloysite assembly on oil microdroplets (Pickering emulsion) and its core-shell structure (functionalization with quantum dots) was described in comparison with microfiber nanoclay coatings. In addition to being abundantly available in nature, halloysite is also biosafe, which makes its spontaneous surface micropatterning prospective for high-performance materials, and it is a promising technique with potential for an industrial scale-up.

Recent advances in natural nanoclay for diagnosis and therapy of cancer: A review

Cancer is still one of the deadliest diseases, and diagnosing and treating it effectively remains difficult. As a result, advancements in earlier detection and better therapies are urgently needed. Conventional chemotherapy induces chemoresistance, has non-specific toxicity, and has a meager efficacy. Natural materials like nanosized clay mineral formations of various shapes (platy, tubular, spherical, and fibrous) with tunable physicochemical, morphological, and structural features serve as potential templates for these. As multifunctional biocompatible nanocarriers with numerous applications in cancer research, diagnosis, and therapy, their submicron size, individual morphology, high specific surface area, enhanced adsorption ability, cation exchange capacity, and multilayered organization of 0.7-1 nm thick single sheets have attracted significant interest. Kaolinite, halloysite, montmorillonite, laponite, bentonite, sepiolite, palygorskite, and allophane are the most typical nanoclay minerals explored for cancer. These multilayered minerals can function as nanocarriers to effectively carry a variety of anticancer medications to the tumor site and improve their stability, dispersibility, sustained release, and transport. Proteins and DNA/RNA can be transported using nanoclays with positive and negative surfaces. The platform for phototherapeutic agents can be nanoclays. Clays with bio-functionality have been developed using various surface engineering techniques, which could help treat cancer. The promise of nanoclays as distinctive crystalline materials with applications in cancer research, diagnostics, and therapy are examined in this review.

Influences of lysine-specific demethylase 1 inhibitors on NO synthase-Kruppel-like factor pathways in human endothelial cells in vitro and zebrafish (Danio rerio) larvae in vivo

Lysine-specific demethylase 1 (LSD1) inhibitors are being developed for cancer therapy, but their bioeffects on vasculatures are not clear. In this study, we compared the influences of ORY-1001 (an LSD1 inhibitor being advanced into clinical trials) and 199 (a novel LSD1 inhibitor recently developed by us) to human umbilical vein endothelial cells (HUVECs) in vitro and further verified the bioeffects of ORY-1001 to zebrafish (Danio rerio) larvae in vivo. The results showed that up to 10 μM ORY-1001 or 199 did not significantly affect the cellular viability of HUVECs but substantially reduced the release of inflammatory interleukin-8 (IL-8) and IL-6. The signaling molecule in vasculatures, NO, was also increased in HUVECs. As the mechanism, the protein levels of endothelial NO synthase (eNOS) or p-eNOS, and their regulators Kruppel-like factor 2 (KLF2) or KLF4, were also increased after drug treatment. In vivo, 24 h treatment with up to 100 nM ORY-1001 reduced blood speed without changing morphologies or locomotor activities in zebrafish larvae. ORY-1001 treatment reduced the expression of il8 but promoted the expression of klf2a and nos in the zebrafish model. These data show that LSD1 inhibitors were not toxic but capable to inhibit inflammatory responses and affect the function of blood vessels through the up-regulation of the NOS-KLF pathway.

Halloysite nanotubes-cellulose ether based biocomposite matrix, a potential sustained release system for BCS class I drug verapamil hydrochloride: Compression characterization, in-vitro release kinetics, and in-vivo mechanistic physiologically based pharmacokinetic modeling studies

This study investigated the ability of natural nanotubular clay mineral (Halloysite) and cellulose ether based biocomposite matrix as a controlled release agent for Verapamil HCl (BCS Class-I). Drug-loaded halloysite was prepared and tablet formulations were designed by varying amount of hydroxy propyl methyl cellulose (HPMC K4M). Physical characterization was carried out using SEM, FTIR, and DSC. Tabletability profiles were evaluated using USP1062 guidelines. Drug release kinetics were studied, and physiologically based pharmacokinetic (PBPK) modeling was performed. Compressed tablets possess satisfactory yield pressure of 625 MPa with adequate hardness and disintegration within 30 min. The initial release of the drug was due to surface drug on tablets, while the prolonged release at later time points (around 80 % drug release at 12 h) were due to halloysite loading. The FTIR spectra exhibited electrostatic attraction between the positively charged drug and the negatively charged Si-O-Si functional group of halloysite, while the thermogram showed Verapamil HCl melting point at ~146 °C with enthalpy change of -126.82 J/g. PBPK modeling exhibited PK parameters of optimized matrix formulation (VER-HNT3%) comparable to in vivo data. The study effectively demonstrated the potential of prepared biocomposite matrix as a commercially viable oral release modifying agent for highly soluble drugs.

Clay Nanotubes Loaded with Diazepam or Xylazine Permeate the Brain through Intranasal Administration in Mice

The blood-brain barrier (BBB) is an obstacle to the permeation of most therapeutic drugs into the brain, limiting treatments for neurological disorders. Drugs loaded within nanocarriers that pass through the BBB can overcome this limitation. Halloysite consists of naturally occurring biocompatible clay nanotubes of 50 nm diameter and 15 nm lumen, allowing the loading and sustained release of loaded drugs. These have demonstrated the ability to transport loaded molecules into cells and organs. We propose to use halloysite nanotubes as a "nano-torpedo" for drug delivery through the BBB due to their needle-like shape. To determine if they can cross the BBB using a non-invasive, clinically translatable route of administration, we loaded halloysite with either diazepam or xylazine and delivered these intranasally to mice daily over six days. The sedative effects of these drugs were observed in vestibulomotor tests conducted at two, five, and seven days after the initial administration. Behavioral tests were conducted 3.5 h after administration to show that the effects were from halloysite/delivered drugs and not from the drug alone. As expected, the treated mice performed more poorly than the sham, drug alone, and halloysite-vehicle-treated mice. These results confirm that halloysite permeates the BBB to deliver drugs when administered intranasally.

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.

Engineering design of asymmetric halloysite/chitosan/collagen sponge with hydrophobic coating for high-performance hemostasis dressing

Uncontrolled massive hemorrhage is a crucial cause of death, and developing efficient hemostatic materials are of great medical importance. Herein, we prepared a halloysite-chitosan-collagen composite sponge by directional freeze-drying method and coating the sponge by hydrophobic polydimethylsiloxane coating for rapid and effective hemostasis. The aligned channel structure of the sponge with a pore size of ~30 μm was beneficial for the transport of blood. Morphology and spectrum results suggested that chitosan and collagen are capable of adsorbing on the outer surface of HNTs due to the hydrogen bonding and electrostatic attractions. The directional freeze-dried sponge absorbed the majority of the blood within 10 s, and that process essentially completed in 30 s, which are faster than its non-directional counterpart. The composite sponges exhibited high antibacterial properties towards E. coli and S. aureus, and they are non-cytotoxic towards mouse fibroblasts and have high hemocompatibility. The hemostatic dressing avoided unnecessary blood loss because of excessive blood absorption. In vivo experiments of rats also confirmed the ability of the asymmetric sponges to rapidly clot and reduce reducing blood loss. This work developed a high-performance and hemostatic dressing by material design and processing technique, which shows a promising application in wound healing.

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

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

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.

Temperature-responsive and biocompatible nanocarriers based on clay nanotubes for controlled anti-cancer drug release

Administration of temperature-responsive drug carriers that release anticancer drugs at high temperatures can benefit hyperthermia therapies because of the synergistic effect of anticancer drug molecules and high temperature on killing the cancer cells. In this study, we design and characterize a new temperature-responsive nanocarrier based on a naturally occurring and biocompatible clay mineral, halloysite nanotubes. Poly(N-isopropylacrylamide) brushes were grown on the surface of halloysite nanotubes using a combination of mussel-inspired dopamine polymerization and surface-initiated atom transfer radical polymerization. The chemical structure of the hybrid materials was investigated using X-ray photoelectron spectroscopy, thermogravimetric analysis and energy-dispersive X-ray spectroscopy. The hybrid material was shown to have a phase transition temperature of about 32 °C, corresponding to a 40 nm thick polymer layer surrounding the nanotubes. Cell studies suggested that grafting of poly(N-isopropylacrylamide) brushes on the polydopamine-modified halloysite nanotubes suppresses the cytotoxicity caused by the polydopamine interlayer and drug release studies on nanotubes loaded with doxorubicin showed that thanks to the poly(N-isopropylacrylamide) brushes a temperature-dependent drug release is observed. Finally, a fluorescent dye molecule was covalently attached to the polymer-grafted nanotubes and stimulated emission depletion nanoscopy was used to confirm the internalization of the nanotubes in HeLa cells.

Environmental Implications Associated with the Development of Nanotechnology: From Synthesis to Disposal

Nanotechnology remains under continuous development. The unique, fascinating, and tunable properties of nanomaterials make them interesting for diverse applications in different fields such as medicine, agriculture, and remediation. However, knowledge about the risks associated with nanomaterials is still poorly known and presents variable results. Furthermore, the interaction of nanomaterials with biological systems and the environment still needs to be clarified. Moreover, some issues such as toxicity, bioaccumulation, and physicochemical transformations are found to be dependent on several factors such as size, capping agent, and shape, making the comparisons even more complex. This review presents a comprehensive discussion about the consequences of the use and development of nanomaterials regarding their potential risks to the environment as well as human and animal health. For this purpose, we reviewed the entire production chain from manufacturing, product development, applications, and even product disposal to raise the important implications at each stage. In addition, we present the recent developments in terms of risk management and the recycling of nanomaterials. Furthermore, the advances and limitations in the legislation and characterization of nanomaterials are also discussed.

Evaluation of cytotoxicity and biodistribution of mesoporous carbon nanotubes (pristine/-OH/-COOH) to HepG2 cells in vitro and healthy mice in vivo

Mesoporous carbon nanotubes (mCNTs) hold great promise interests, owing to their superior nano-platform properties for biomedicine. To fully utilize this potential, the toxicity and biodistribution of pristine and surface-modified mCNTs (-OH/-COOH) should preferentially be addressed. The results of cell viability suggested that pristine mCNTs induced cell death in a concentration-dependent manner. As evidence of reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase (SOD), pristine mCNTs induced noticeable redox imbalance. ^99mTc tracing data suggested that the cellular uptake of pristine mCNTs posed a concentrate-dependent and energy-dependent manner via macropinocytotic and clathrin-dependent pathways, and the main accumulated organs were lung, liver and spleen. With OH modification, the ROS generation, MDA deposition and SOD consumption were evidently reduced compared with the pristine mCNTs at 24/48 h high-dose exposure. With COOH modification, the modified mCNTs only showed a significant difference in SOD consumption at 24/48 h exposure, but there was no significant difference in the measurement of ROS and MDA. The internalization mechanism and organ distribution of modified mCNTs were basically invariant. Together, our study provides evidence that mCNTs and the modified mCNTs all could induce oxidative damage and thereby impair cells. ^99mTc-mCNTs can effectively trace the distribution of nanotubes in vivo.

Where Is Nano Today and Where Is It Headed? A Review of Nanomedicine and the Dilemma of Nanotoxicology

Worldwide nanotechnology development and application have fueled many scientific advances, but technophilic expectations and technophobic demands must be counterbalanced in parallel. Some of the burning issues today are the following: (1) Where is nano today? (2) How good are the communication and investment networks between academia/research and governments? (3) Is there any spotlight application for nanotechnology? Nanomedicine is a particular arm of nanotechnology within the healthcare landscape, focused on diagnosis, treatment, and monitoring of emerging (such as coronavirus disease 2019, COVID-19) and contemporary (including diabetes, cardiovascular diseases, neurodegenerative disorders, and cancer) diseases. However, it may only represent the bright side of the coin. In fact, in the recent past, the concept of nanotoxicology has emerged to address the dark shadows of nanomedicine. The nanomedicine field requires more nanotoxicological studies to identify undesirable effects and guarantee safety. Here, we provide an overall perspective on nanomedicine and nanotoxicology as central pieces of the giant puzzle of nanotechnology. First, the impact of nanotechnology on education and research is highlighted, followed by market trends and scientific output tendencies. In the next section, the nanomedicine and nanotoxicology dilemma is addressed through the interplay of in silico, in vitro, and in vivo models with the support of omics and microfluidic approaches. Lastly, a reflection on the regulatory issues and clinical trials is provided. Finally, some conclusions and future perspectives are proposed for a clearer and safer translation of nanomedicines from the bench to the bedside.

Prokaryotic and eukaryotic toxicity of halloysite decorated with photoactive nanoparticles

The development of new approaches to treat the growing antibiotic resistance of pathogenic bacterial species is an important task to ensure the future safety of society. Utilization of irradiation of different wavelengths together with nanostructured materials based on metal containing nanoparticles may result in synergetic antibacterial effects. In this paper we aim to show the main conceptions of light-assisted bacteria deactivation techniques and prospects of application of natural clay nanotubes as a carrier for scalable photoactive antibacterial nanomaterials. Halloysite aluminosilicate nanotubes (ca 50 nm diameter, ca. 1.0 μm length) are safe and biocompatible natural materials produced in tons. Their application as a template or a carrier for metal nanoparticles, QDs and organic compounds has already found application in biomedical research, cosmetics, polymers, coatings, catalysis and related applications. Here, we show the toxicity of halloysite decorated with photoactive nanoparticles on prokaryotic and eukaryotic cells. The formation of light active nanostructured materials with this clay as the base is a promising tool for solving the problem of the antibiotic resistance of microorganisms.

Vascular toxicity of multi-walled carbon nanotubes targeting vascular endothelial growth factor

Multiwalled carbon nanotubes (MWCNTs) are currently widely used and are expected to be used as drug carriers and contrast agents in clinical practice. Previous studies mainly focused on their lung toxicity; therefore, their effects on the vascular endothelium are unclear. In this study, a human angiogenesis array was used to determine the effect of MWCNTs on the expression profile of angiogenic factors in endothelial cells and to clarify the role of vascular endothelial growth factor (VEGF) in MWCNT-induced endothelial cell injury at the cellular and animal levels. The results indicated that MWCNTs (20-30 nm and 30-50 nm) could enter endothelial cells and disrupt human umbilical vein endothelial cell (HUVECs) activity in a concentration-dependent manner. MWCNTs disrupted the tube formation ability and cell migration function of HUVECs. The results from a Matrigel Plug experiment in mice showed that angiogenesis in the MWCNT experimental group was significantly reduced. The results of a protein chip analysis indicated that VEGF expression in the MWCNT treatment group was decreased, a finding that was validated by ELISA results. The protein expression levels of AKT and eNOS in the MWCNT treatment group were significantly decreased; the administration of recombinant VEGF significantly alleviated the migration ability and tube formation ability of endothelial cells injured by MWCNTs, upregulated the protein expression of AKT and eNOS, and increased the number of neovascularization in mice in the MWCNT treatment group. This study demonstrated that MWCNTs affect angiogenesis via the VEGF-Akt-eNOS axis which can be rescued by VEGF endothelial treatment.

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.

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.

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.

Application of Antioxidants as an Alternative Improving of Shelf Life in Foods

Oxidation is the main problem in preserving food products during storage. A relatively novel strategy is the use of antioxidant-enriched edible films. Antioxidants hinder reactive oxygen species, which mainly affect fats and proteins in food. At present, these films have been improved by the addition of micro- and nanoliposomes coated with carbohydrate polymers, which are not hazardous for human health and can be ingested without risk. The liposomes are loaded with different antioxidants, and their effects are observed as a longer storage time of the food product. The synergy of these methodologies and advances can lead to the displacement of the protective packaging used currently, which would result in food products with functional properties added by the films, an increase in shelf life, and an improvement to the environment by reducing the amount of waste.

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.

Preclinical developments of natural-occurring halloysite clay nanotubes in cancer therapeutics

The natural world holds useful resources that can be exploited to design effective therapeutic approaches. Ready-to-use tubular nanoclays, such as halloysite clay nanotubes (HNTs), are widely available, cost-effective, and sustainable submicron crystalline materials that have been showing great potential towards chronic multifactorial and malignant diseases, standing out as a promising anticancer nanotherapeutic strategy. Currently, several preclinical studies have reported the application of HNTs in cancer research, diagnosis, monitoring, and therapeutics. This groundbreaking review highlights the preclinical knowledge hitherto collected concerning the application of HNTs towards cancer therapy. Despite their reproducibility issues, HNTs were used as nanoarchitectonic platforms for the delivery of conventional chemotherapeutic, natural-occurring, biopharmaceutical, and phototherapeutic anticancer agents in a wide range of in vitro and in vivo solid cancer models. Overall, in different types of cancer mice models, the intratumoral and intravenous administration of HNTs-based nanoplatforms induced tumor growth inhibition without causing significant toxic effects. Such evidence raises a relevant question: does the therapeutic benefit of the parenteral administration of HNTs in cancer outweigh their potential toxicological risk? To answer this question further long-term absorption-distribution-metabolism-excretion studies in healthy and cancer animal models need to be performed. In cancer therapeutics, HNTs are envisaged as promising platforms for cancer multi-agent therapy, enabling the combination of different therapeutic modalities. Furthermore, HNTs might constitute suitable nanotheranostic platforms. Nevertheless, to confirm the potential and safety of the application of HNTs as nanodelivery systems for cancer therapy, it is necessary to perform in-depth in vivo pharmacokinetics and pharmacodynamic studies to further the translation to clinical trials.

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.

Multi-walled carbon nanotubes decrease neuronal NO synthase in 3D brain organoids

Multi-walled carbon nanotubes (MWCNTs) might induce the dysfunction of neuronal NO synthase (nNOS) and impair the function of brains. But to the best of our knowledge, this conclusion was made by using laboratory animals or conventional nerve cell cultures; however, these models might not reflect the complex conditions of human brains. Recently, the development of 3D brain organoids (also known as organotypic cultures) derived from human induced pluripotent stem cells (iPSCs) provides a platform to investigate the behaviors of human brains in vitro. In this study, we investigated the toxicity of MWCNTs to 3D brain organoids which expressed the cortical layer markers. It was shown that MWCNTs induced cytotoxicity to 3D brain organoids but not in dose-dependent manner. Exposure to high level of MWCNTs (64 μg/mL) reduced the levels of intracellular NO but increased superoxide. As the mechanism, 64 μg/mL MWCNTs significantly reduced the protein level of nNOS. The nNOS regulators nuclear factor kappa-B (NF-κB) proteins were significantly induced by MWCNTs, whereas Kruppel-like factor 4 (KLF4) proteins were reduced particularly after exposure to low level of MWCNTs (16 μg/mL). The results from fluorescence micro-optical sectioning tomography (MOST) confirmed the decrease of nNOS proteins, not only at the out-layers that directly contacted MWCNTs, but also at the inner-layers. Combined, our results suggested that MWCNTs could decrease nNOS activity by inducing oxidative stress and modulating NF-κB-KLF4 pathway. This study also showed the potential of 3D brain organoids in mechanism-based toxicology studies.

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.