Inhibition of inhaled halloysite nanotube toxicity by trehalose through enhanced autophagic clearance of p62

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.

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.

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.

Inhibition of Pro-Survival Autophagy Induced by Rare-Earth Nanocomposites for Promoting Photothermal Therapy of Visualized Tumors

Manipulation of autophagic processes has emerged as a promising strategy for synergizing nanoagent-mediated photothermal therapy (PTT). Most of the current studies focus on improving PTT efficacy by inhibiting pro-survival autophagy induced by the heat generated from the photothermal process. However, autophagy induced by the nanoagents is usually ignored, which may weaken the effect of autophagy-mediated efficacy improvement in PTT if induced autophagy is pro-death. Therefore, this work aims at developing a nanoagent that is able to induce heat-synergetic pro-survival autophagy to optimize the efficacy of PTT. An approach is developed to coat carbon layer, polyethylenimine (PEI), and folic acid (FA) on NaYF₄ :Er,Yb,Nd@NaNdF₄ (DCNPs@C@PEI@FA, DCPF) nanoparticles successively, giving access to the nanoagent to induce pro-survival autophagy. The synthetic imaging-guided photothermal nanoagent displays outstanding targeting ability and biocompatibility based on the surface modification of PEI and FA. By using an autophagy inhibitor chloroquine, a conspicuously synergistic effect on DCPF-mediated PTT in vitro and in vivo tumor models (HeLa) is achieved. A promising strategy is presented here to enhance the efficacy of imaging-guided PTT by modulating the autophagy induced by the nanoagent.

Laboratory investigation of pollutant emissions and PM2.5 toxicity of underground coal fires

Widespread underground coal fires (UCFs) release large amounts of pollutants, thus leading to air pollution and health impacts. However, this topic has not been widely investigated, especially regarding the potential health hazards. We quantified the pollutant emissions and analyzed the physicochemical properties of UCF PM_2.5 in a laboratory study of coal smoldering under a simulated UCF background. The emission factors of CO₂, CO, and PM_2.5 were 2489 ± 35, 122 ± 9, 12.90 ± 1.79 g/kg, respectively. UCF PM_2.5 are carbonaceous particles with varied morphology and complex composition, including heavy metals, silica and polycyclic aromatic hydrocarbons (PAHs). The main PAHs components were those with 2-4 rings. Benzoapyrene (BaP) and indeno[1,2, 3-cd]pyrene (IcdP) were important contributors to the carcinogenesis of these PAHs. We quantitatively evaluate the toxicity of inhaled UCF PM_2.5 using a nasal inhalation exposure system. The target organs of UCF PM_2.5 are lungs, liver, and kidneys. UCF PM_2.5 presented an enriched chemical composition and induced inflammation and oxidative stress, which together mediated multiple organ injury. Long-term PM_2.5 metabolism is the main cause of persistent toxicity, which might lead to long-term chronic diseases. Therefore, local authorities should recognize the importance and effects of UCF emissions, especially PM_2.5, to establish control and mitigation measures.

Architectural design of core-shell nanotube systems based on aluminosilicate clay

A nanoarchitectural approach to the design of functional nanomaterials based on natural aluminosilicate nanotubes and their catalysis, and practical applications are described in this paper. We focused on the buildup of hybrid core-shell systems with metallic or organic molecules encased in aluminosilicate walls, and nanotube templates for structured silica and zeolite preparation. The basis for such an architectural design is a unique Al₂O₃/SiO₂ dual chemistry of 50 nm diameter halloysite tubes. Their structure and site dependent properties are well combined with biocompatibility, environmental safety, and abundant availability, which makes the described functional systems scalable for industrial applications. In these organic/ceramic hetero systems, we outline drug, dye and chemical inhibitor loading inside the clay nanotubes, accomplished with their silane or amphiphile molecule surface modifications. For metal-ceramic tubule composites, we detailed the encapsulation of 2-5 nm Au, Ru, Pt, and Ag particles, Ni and Co oxides, NiMo, and quantum dots of CdZn sulfides into the lumens or their attachment at the outside surface. These metal-clay core-shell nanosystems show high catalytic efficiency with increased mechanical and temperature stabilities. The combination of halloysite nanotubes with mesoporous MCM-41 silica allowed for a synergetic enhancement of catalysis properties. Finally, we outlined the clay nanotubes' self-assembly into organized arrays with orientation and ordering similar to nematic liquid crystals, and these systems are applicable for life-related applications, such as petroleum spill bioremediation, antimicrobial protection, wound healing, and human hair coloring.

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.

Toxicological Evaluations in Macrophages and Mice Acutely and Chronically Exposed to Halloysite Clay Nanotubes Functionalized with Polystyrene

Halloysite clay nanotubes (HNTs) have been proposed as highly biocompatible for several biomedical applications. Various polymers have been used to functionalize HNTs, but scarce information exists about polystyrene for this purpose. This work evaluated polystyrene-functionalized HNTs (FHNTs) by comparing its effects with non-FHNTs and innocuous talc powder on in vitro and in vivo models. Monocyte-derived human or murine macrophages and the RAW 264.7 cell line were treated with 0.01, 0.1, 1, and 100 μg mL^-1 FHNTs, HNTs, or talc to evaluate the cytotoxic and cytokine response. Our results show that nanoclays did not cause cytotoxic damage to macrophages. Only the 100 μg mL^-1 concentration induced slight proinflammatory cytokine production at short exposure, followed by an anti-inflammatory response that increases over time. CD1 mice treated with a single dose of 1, 2.5, or 5 mg Kg^-1 of FHNTs or HNTs by oral and inhalation routes caused aluminum accumulation in the kidneys and lungs, without bodily signs of distress or histopathological changes in any treated mice, evaluated at 48 h and 30 days post-treatment. Nanoclay administration simultaneously by four different parenteral routes (20 mg Kg^-1) or the combination of administration routes (parenteral + oral or parenteral + inhalation; 25 mg Kg^-1) showed accumulation on the injection site and slight surrounding inflammation 30 days post-treatment. CD1 mice chronically exposed to HNTs or FHNTs in the bedding material (ca 1 mg) throughout the parental generation and two successive inbred generations for 8 months did not cause any inflammatory process or damage to the abdominal organs and the reproductive system of the mice of any of the generations, did not affect the number of newborn mice and their survival, and did not induce congenital malformations in the offspring. FHNTs showed a slightly less effect than HNTs in all experiments, suggesting that functionalization makes them less cytotoxic. Doses of up to 25 mg Kg^-1 by different administration routes and permanent exposure to 1 mg of HNTs or FHNTs for 8 months seem safe for CD1 mice. Our in vivo and in vitro results indicate that nanoclays are highly biocompatible, supporting their possible safe use for future biomedical and general-purpose applications.

Biodistribution of Quantum Dots-Labelled Halloysite Nanotubes: A Caenorhabditis elegans In Vivo Study

Halloysite is a promising building block in nanoarchitectonics of functional materials, especially in the development of novel biomaterials and smart coatings. Understanding the behavior of materials produced using halloysite nanotubes within living organisms is essential for their safe applications. In this study, quantum dots of different compositions were synthesized on the surface of modified clay nanotubes, and the biodistribution of this hybrid material was monitored within Caenorhabditis elegans nematodes. The influence of the modification agent as well as the particles’ composition on physicochemical properties of hybrid nanomaterials was investigated. Several microscopy techniques, such as fluorescence and dark-field microscopy, were compared in monitoring the distribution of nanomaterials in nematodes’ organisms. The effects of QDs-halloysite composites on the nematodes’ life cycle were investigated in vivo. Our fluorescent hybrid probes induced no acute toxic effects in model organisms. The stable fluorescence and low toxicity towards the organisms suggest that the proposed synthesis procedure yields safe nanoarchitectonic materials that will be helpful in monitoring the behavior of nanomaterials inside living cells and organisms.

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

Nanomaterials (NMs) with tubular structures, such as halloysite nanotubes (HNTs), have potential applications in biomedicine. Although the biocompatibility of HNTs has been investigated before, the toxicity of HNTs to blood vessels is rarely systemically evaluated. Herein, we compared the toxicity of HNTs and multi-walled carbon nanotubes (MWCNTs) to human umbilical vein endothelial cells (HUVECs) in vitro and blood vessels of mice in vivo. HUVECs internalized HNTs and MWCNTs, but the uptake of HNTs was not obviously changed by clathrin inhibitor. Exposure to NMs decreased cellular viability, activated apoptotic proteins and up-regulated adhesion molecules, including soluble vascular cell adhesion molecule 1 (sVCAM-1) and VCAM-1. As the mechanisms, NMs decreased NO levels, eNOS mRNA and eNOS/p-eNOS proteins. Meanwhile, NMs promoted intracellular ROS and autophagy dysfunction, shown as decreased protein levels of LC3, beclin-1 and ATG5. The eNOS regulator Kruppel-like factor 4 (KLF4) was inhibited, but another eNOS regulator KLF4 was surprisingly up-regulated. Under in vivo conditions, ICR mice intravenously injected with NMs (50 μg/mouse, once a day for 5 days) showed an increased percentage of neutrophils, monocytes and basophils. Meanwhile, autophagy dysfunction, eNOS uncoupling, activation of apoptotic proteins and alteration of KLF proteins were also observed in mouse aortas. All of the toxic effects were more pronounced for MWCNTs in comparison with HNTs based on the same mass concentrations. Our results may provide novel insights about the toxicity of NMs with tubular structures to blood vessels. Considering the toxicological data reported here, HNTs are probably safer nanocarriers compared with MWCNTs.

Naturally derived nano- and micro-drug delivery vehicles: halloysite, vaterite and nanocellulose

We discuss prospects for halloysite nanotubes, vaterite crystals and nanocellulose to enter the market of biomaterials for drug delivery and tissue engineering, and their potential for economically viable production from abundant natural sources.

Pro-Death or Pro-Survival: Contrasting Paradigms on Nanomaterial-Induced Autophagy and Exploitations for Cancer Therapy

Autophagy is a critical lysosome-mediated cellular degradation process for the clearance of damaged organelles, obsolete proteins, and invading pathogens and plays important roles in the pathogenesis and treatment of human diseases including cancer. While not a cell death process per se, autophagy is nevertheless intimately linked to a cell's live/die decision. Basal autophagy, operating constitutively at low levels in essentially every mammalian cell, is vital for maintaining cellular homeostasis and promotes cell survival. On the other hand, elevated level of autophagy is frequently observed in cells responding to a physical, chemical, or biological stress. This "induced" autophagy, a hallmark under a variety of pathological and pathophysiological conditions, may be either pro-death or pro-survival, two contrasting paradigms for cell fate determination. Research in our laboratory and other groups around the world over the last 15 years has revealed nanomaterials as a unique class of autophagy inducers, with the capability of elevating the cellular autophagy to extremely high levels. In this Account we focus on the contrasting cell fate decision impacted by nanomaterial-induced autophagy. First, we give a brief introduction to nanomaterial-induced autophagy and summarize our current understanding on how it affects a cell's live/die decision. Autophagy induced by nanomaterials, in most cases, promotes cell death, but a significant number of nanomaterials are also able to elicit pro-survival autophagy. Although not a common feature, some nanomaterials may induce pro-death autophagy in one cell type while eliciting pro-survival autophagy in a different cell type. The ability to control the level of the induced autophagy, and furthermore its pro-death/pro-survival nature, is critically important for nanomedicine. Second, we discuss several possible mechanistic insights on the pro-death/pro-survival decision for nanomaterial-induced autophagy. "Disrupted" autophagic processes, with a "block" or perhaps "diversion" at the various stages, may be a characteristic hallmark for nanomaterial-induced autophagy, rendering it intrinsically pro-death in nature. On the other hand, autophagy-mediated upregulation and activation of pro-survival factors or signaling pathways, overriding the intrinsic pro-death nature, may be a common mechanism for nanomaterial-induced pro-survival autophagy. In addition, cargo degradation and reactive oxygen species may also play important roles in the pro-death/pro-survival decision impacted by nanomaterial-induced autophagy. Finally, we focus on the situation where nanomaterials induce autophagy in cancer cells and summarize the different strategies in exploiting the pro-death or pro-survival nature of nanomaterial-induced autophagy to enhance the various modalities of cancer therapy, including direct cancer cell killing, chemotherapy and radiotherapy, photothermal therapy, and integrated diagnosis and therapy. While the details vary, the basic principle is simple and straightforward. If the induced autophagy is pro-death, maximize it. Otherwise, inhibit it. Effective exploitation of nanomaterial-induced autophagy has the potential to become a new weapon in our ever-increasing arsenal to fight cancer, particularly difficult-to-treat and drug-resistant cancer.

Evolution of Hair Treatment and Care: Prospects of Nanotube-Based Formulations

A new approach for hair treatment through coating with nanotubes loaded with drugs or dyes for coloring is suggested. This coating is produced by nanotube self-assembly, resulting in stable 2-3 µm thick layers. For medical treatment such formulations allow for sustained long-lasting drug delivery directly on the hair surface, also enhanced in the cuticle openings. For coloring, this process allows avoiding a direct hair contact with dye encased inside the clay nanotubes and provides a possibility to load water insoluble dyes from an organic solvent, store the formulation for a long time in dried form, and then apply to hair as an aqueous nanotube suspension. The described technique works with human and other mammal hairs and halloysite nanoclay coating is resilient against multiple shampoo washing. The most promising, halloysite tubule clay, is a biocompatible natural material which may be loaded with basic red, blue, and yellow dyes for optimized hair color, and also with drugs (e.g., antilice care-permethrin) to enhance the treatment efficiency with sustained release. This functionalized nanotube coating may have applications in human medical and beauty formulations, as well as veterinary applications.