Silver nanoparticles induce tight junction disruption and astrocyte neurotoxicity in a rat blood-brain barrier primary triple coculture model

Sodium Selenite Ameliorates Silver Nanoparticles Induced Vascular Endothelial Cytotoxic Injury by Antioxidative Properties and Suppressing Inflammation Through Activating the Nrf2 Signaling Pathway

Silver nanoparticles (AgNP) are the dominant nanomaterials in commercial products and the medical field, but the widespread occurrence of AgNP has become a global threat to human health. Growing studies indicate that AgNP exposure can induce vascular endothelial toxicity by excessive oxidative stress and inflammation, which is closely related to cardiovascular disease (CVD), but the potential intrinsic mechanism remains poorly elucidated. Thus, it has been crucial to control the toxicological effects of AgNP in order to improve their safety and increase the outcome of their applications.Multiple researches have demonstrated that sodium selenite (Se) possesses the capability to counteract the toxicity of AgNP, but the functional role of Se in AgNP-induced CVD is largely unexplored. The aim of this study was to explore the potential protective effect of Se on AgNP-induced vascular endothelial lesion and elucidate the underlying mechanisms. An in vivo model of toxicity in animals was established by the instillation of 200 µL of AgNP into the trachea of rats both with (0.2 mg/kg/day) and without Se treated. In vitro experiments, human umbilical vein endothelial cells (HUVECs) were incubated with AgNP (0.3 µg/mL ) and Se for a duration of 24 h. Utilizing transmission electron microscopy, we observed that the internalization of AgNP-induced endothelial cells was desquamated from the internal elastic lamina, the endoplasmic reticulum was dilated, and the medullary vesicle formed. Se treatment reduced the levels of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), inhibited the release of pro-inflammatory cytokines (specifically tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6), improved endothelial cell permeability, integrity, and dysfunction, and prevented damage to the aortic endothelium caused by AgNP. Importantly, we found that Se showed the capacity against AgNP with biological functions in guiding the intracellular reactive oxygen species (ROS) scavenging and meanwhile exhibiting anti-inflammation effects. Se supplementation decreased the intracellular ROS release and suppressed NOD-like receptor protein 3 (NLRP3) and nuclear factor kappa-B (NF-κB) mediated inflammation within AgNP-intoxicated rats and HUVECs. The anti-oxidant stress and anti-inflammatory effects of Se were at least partly dependent on nuclear factor erythroid 2-related factor 2 (Nrf2). Overall, our results indicated that the protectiveness of Se against AgNP-induced vascular endothelial toxicity injury was at least attributed to the inhibition of oxidative ROS and pro-inflammatory NF-κB/NLRP3 inflammasome by activating the Nrf2 and antioxidant enzyme (HO-1) signal pathway.

Controlling nanoparticle-induced endothelial leakiness with the protein corona

Understanding nanoparticle-cell interaction is essential for advancing research in nanomedicine and nanotoxicology. Apart from the transcytotic pathway mediated by cellular recognition and energetics, nanoparticles (including nanomedicines) may harness the paracellular route for their transport by inducing endothelial leakiness at cadherin junctions. This phenomenon, termed as NanoEL, is correlated with the physicochemical properties of the nanoparticles in close association with cellular signalling, membrane mechanics, as well as cytoskeletal remodelling. However, nanoparticles in biological systems are transformed by the ubiquitous protein corona and yet the potential effect of the protein corona on NanoEL remains unclear. Using confocal fluorescence microscopy, biolayer interferometry, transwell, toxicity, and molecular inhibition assays, complemented by molecular docking, here we reveal the minimal to significant effects of the anionic human serum albumin and fibrinogen, the charge neutral immunoglobulin G as well as the cationic lysozyme on negating gold nanoparticle-induced endothelial leakiness in vitro and in vivo. This study suggests that nanoparticle-cadherin interaction and hence the extent of NanoEL may be partially controlled by pre-exposing the nanoparticles to plasma proteins of specific charge and topology to facilitate their biomedical applications.

Noradrenaline release from the locus coeruleus shapes stress-induced hippocampal gene expression

Exposure to an acute stressor triggers a complex cascade of neurochemical events in the brain. However, deciphering their individual impact on stress-induced molecular changes remains a major challenge. Here, we combine RNA sequencing with selective pharmacological, chemogenetic, and optogenetic manipulations to isolate the contribution of the locus coeruleus-noradrenaline (LC-NA) system to the acute stress response in mice. We reveal that NA release during stress exposure regulates a large and reproducible set of genes in the dorsal and ventral hippocampus via β-adrenergic receptors. For a smaller subset of these genes, we show that NA release triggered by LC stimulation is sufficient to mimic the stress-induced transcriptional response. We observe these effects in both sexes, and independent of the pattern and frequency of LC activation. Using a retrograde optogenetic approach, we demonstrate that hippocampus-projecting LC neurons directly regulate hippocampal gene expression. Overall, a highly selective set of astrocyte-enriched genes emerges as key targets of LC-NA activation, most prominently several subunits of protein phosphatase 1 (Ppp1r3c, Ppp1r3d, Ppp1r3g) and type II iodothyronine deiodinase (Dio2). These results highlight the importance of astrocytic energy metabolism and thyroid hormone signaling in LC-mediated hippocampal function and offer new molecular targets for understanding how NA impacts brain function in health and disease.

Assessing cytotoxicity and endoplasmic reticulum stress in human blood-brain barrier cells due to silver and copper oxide nanoparticles

In recent years, it has been generally accepted that metal-based nanoparticles (NPs) may induce stress in the endoplasmic reticulum (ER), a key organelle where protein folding occurs. We examined ER stress in immortalized human cerebral microvascular cells (hCMEC/D3) after exposure to silver-NPs (Ag-NPs)- and copper oxide-NPs (CuO-NPs) induced toxicity at < 10 nm and < 40 nm or < 50 nm diameters, respectively. In cytotoxicity assessments, cells were exposed to different CuO-NPs (5-400 µg/mL) or Ag-NPs (1-10 µg/mL) concentration ranges for 24 h and 72 h, and tetrazole salt reduction assays (EZ4U) were performed. Also, Ag-NP or CuO-NP effects on cell proliferation, apoptosis (caspase 3/7 assays), and ER stress and cell morphology were evaluated. In ER stress assessments, RNA-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), inositol-requiring enzyme 1 (IRE1a), and others stress factor mRNA levels were determined after 24 h treatment using Real-Time PCR. Increased stress sensors (IRE1a, PERK, and ATF6) mRNA levels were observed after exposure to Ag-NPs (< 10 and < 40 nm) or CuO-NPs (< 50 nm). We investigated the expression of tight junction (TJ) proteins (barrier junctions) and showed that both types of NP reduced of OCLN gene expression. Morphological changes were observed after Ag-NP or CuO-NP exposure using holotomographic microscopy. Our data suggest that Ag- and CuO-NPs should undergo future in vitro and in vivo toxicology studies, especially for downstream biomedical application and occupational risk assessments.

Suppression of sonic hedgehog pathway-based proliferation in glioblastoma cells by small-size silver nanoparticles in vitro

Glioblastomas (GBs) are one of the most aggressive and invasive intracranial cancers. Recently, it has been postulated that, among other factors, the hedgehog (HH) pathway may be a key factor in this phenomenon. Moreover, it has been reported that small-size silver nanoparticles (AgNPs) are characterized by a high cytotoxic effect towards GBs. However, their effect on the sonic hedgehog (SHH) pathway has never been demonstrated in any cancer cells. Therefore, the aim of the present study was to evaluate the impact of the anti-proliferative properties of 5-nm AgNPs on the SHH pathway in the GB cell line (U-87MG) in vitro. The results showed a time- and dose-dependent decrease in the metabolic activity in the U-87MG cells treated with AgNPs, with IC50 reaching 30.41 and 21.16 µg/mL after 24 h and 48 h, respectively, followed by an increase in the intracellular reactive oxygen species (ROS) level. The co-treatment of the cells with AgNPs and Robotnikinin (SHH inhibitor) abolished and/or strengthened the effect of AgNPs, especially on the SHH mRNA levels and on the PCNA, PTCH1, Gli1, and SUFU protein levels. Interestingly, no changes in the level of ERK1/2, Akt, and SRC kinase protein expression were detected, suggesting a direct impact of AgNPs and/or ROS on the inhibition of the canonical SHH pathway. However, more studies are needed due to the increase in the mTOR protein expression after the treatment of the cells with AgNPs, as in the Robotnikinin treatment. In conclusion, small-size AgNPs are able to inhibit the proliferation of GB cells in vitro by suppressing the canonical SHH pathway.

Determinants and mechanisms of inorganic nanoparticle translocation across mammalian biological barriers

Biological barriers protect delicate internal tissues from exposures to and interactions with hazardous materials. Primary anatomical barriers prevent external agents from reaching systemic circulation and include the pulmonary, gastrointestinal, and dermal barriers. Secondary barriers include the blood-brain, blood-testis, and placental barriers. The tissues protected by secondary barriers are particularly sensitive to agents in systemic circulation. Neurons of the brain cannot regenerate and therefore must have limited interaction with cytotoxic agents. In the testis, the delicate process of spermatogenesis requires a specific milieu distinct from the blood. The placenta protects the developing fetus from compounds in the maternal circulation that would impair limb or organ development. Many biological barriers are semi-permeable, allowing only materials or chemicals, with a specific set of properties, that easily pass through or between cells. Nanoparticles (particles less than 100 nm) have recently drawn specific concern due to the possibility of biological barrier translocation and contact with distal tissues. Current evidence suggests that nanoparticles translocate across both primary and secondary barriers. It is known that the physicochemical properties of nanoparticles can affect biological interactions, and it has been shown that nanoparticles can breach primary and some secondary barriers. However, the mechanism by which nanoparticles cross biological barriers has yet to be determined. Therefore, the purpose of this review is to summarize how different nanoparticle physicochemical properties interact with biological barriers and barrier products to govern translocation.

Potentially toxic elements in the brains of people with multiple sclerosis

Potentially toxic elements such as lead and aluminium have been proposed to play a role in the pathogenesis of multiple sclerosis (MS), since their neurotoxic mechanisms mimic many of the pathogenetic processes in MS. We therefore examined the distribution of several potentially toxic elements in the autopsied brains of people with and without MS, using two methods of elemental bio-imaging. Toxicants detected in the locus ceruleus were used as indicators of past exposures. Autometallography of paraffin sections from multiple brain regions of 21 MS patients and 109 controls detected inorganic mercury, silver, or bismuth in many locus ceruleus neurons of both groups, and in widespread blood vessels, oligodendrocytes, astrocytes, and neurons of four MS patients and one control. Laser ablation-inductively coupled plasma-mass spectrometry imaging of pons paraffin sections from all MS patients and 12 controls showed that combinations of iron, silver, lead, aluminium, mercury, nickel, and bismuth were present more often in the locus ceruleus of MS patients and were located predominantly in white matter tracts. Based on these results, we propose that metal toxicants in locus ceruleus neurons weaken the blood-brain barrier, enabling multiple interacting toxicants to pass through blood vessels and enter astrocytes and oligodendroglia, leading to demyelination.

Toxic implications of silver nanoparticles on the central nervous system: A systematic literature review

Silver nanoparticles have many medical and commercial applications, but their effects on human health are poorly understood. They are used extensively in products of daily use, but little is known about their potential neurotoxic effects. A xenobiotic metal, silver, has no known physiological significance in the human body as a trace metal. Biokinetics of silver nanoparticles indicates its elimination from the body via urine and feces route. However, a substantial amount of evidence from both in vitro and in vivo experimental research unequivocally establish the fact of easier penetration of smaller nanoparticles across the blood-brain barrier to enter in brain and thereby interaction with cellular components to induce neurotoxic effects. Toxicological effects of silver nanoparticles rely on the degree of exposure, particle size, surface coating, and agglomeration state as well as the type of cell or organism used to evaluate its toxicity. This review covers pertinent facts and the present state of knowledge about the neurotoxicity of silver nanoparticles reviewing the impacts on oxidative stress, neuroinflammation, mitochondrial function, neurodegeneration, apoptosis, and necrosis. The effect of silver nanoparticles on the central nervous system is a topic of growing interest and concern that requires immediate consideration.

Overcoming the blood-brain barrier for the therapy of malignant brain tumor: current status and prospects of drug delivery approaches

Besides the broad development of nanotechnological approaches for cancer diagnosis and therapy, currently, there is no significant progress in the treatment of different types of brain tumors. Therapeutic molecules crossing the blood-brain barrier (BBB) and reaching an appropriate targeting ability remain the key challenges. Many invasive and non-invasive methods, and various types of nanocarriers and their hybrids have been widely explored for brain tumor treatment. However, unfortunately, no crucial clinical translations were observed to date. In particular, chemotherapy and surgery remain the main methods for the therapy of brain tumors. Exploring the mechanisms of the BBB penetration in detail and investigating advanced drug delivery platforms are the key factors that could bring us closer to understanding the development of effective therapy against brain tumors. In this review, we discuss the most relevant aspects of the BBB penetration mechanisms, observing both invasive and non-invasive methods of drug delivery. We also review the recent progress in the development of functional drug delivery platforms, from viruses to cell-based vehicles, for brain tumor therapy. The destructive potential of chemotherapeutic drugs delivered to the brain tumor is also considered. This review then summarizes the existing challenges and future prospects in the use of drug delivery platforms for the treatment of brain tumors.

In Vitro Models of Biological Barriers for Nanomedical Research

Nanoconstructs developed for biomedical purposes must overcome diverse biological barriers before reaching the target where playing their therapeutic or diagnostic function. In vivo models are very complex and unsuitable to distinguish the roles plaid by the multiple biological barriers on nanoparticle biodistribution and effect; in addition, they are costly, time-consuming and subject to strict ethical regulation. For these reasons, simplified in vitro models are preferred, at least for the earlier phases of the nanoconstruct development. Many in vitro models have therefore been set up. Each model has its own pros and cons: conventional 2D cell cultures are simple and cost-effective, but the information remains limited to single cells; cell monolayers allow the formation of cell–cell junctions and the assessment of nanoparticle translocation across structured barriers but they lack three-dimensionality; 3D cell culture systems are more appropriate to test in vitro nanoparticle biodistribution but they are static; finally, bioreactors and microfluidic devices can mimicking the physiological flow occurring in vivo thus providing in vitro biological barrier models suitable to reliably assess nanoparticles relocation. In this evolving context, the present review provides an overview of the most representative and performing in vitro models of biological barriers set up for nanomedical research.

Recent Advances and Mechanistic Insights into Antibacterial Activity, Antibiofilm Activity, and Cytotoxicity of Silver Nanoparticles

The substantial increase in multidrug-resistant (MDR) pathogenic bacteria is a major threat to global health. Recently, the Centers for Disease Control and Prevention reported possibilities of greater deaths due to bacterial infections than cancer. Nanomaterials, especially small-sized (size ≤10 nm) silver nanoparticles (AgNPs), can be employed to combat these deadly bacterial diseases. However, high reactivity, instability, susceptibility to fast oxidation, and cytotoxicity remain crucial shortcomings for their uptake and clinical application. In this review, we discuss various AgNPs-based approaches to eradicate bacterial infections and provide comprehensive mechanistic insights and recent advances in antibacterial activity, antibiofilm activity, and cytotoxicity (both in vitro and in vivo) of AgNPs. The mechanistic of antimicrobial activity involves four steps: (i) adhesion of AgNPs to cell wall/membrane and its disruption; (ii) intracellular penetration and damage; (iii) oxidative stress; and (iv) modulation of signal transduction pathways. Numerous factors affecting the bactericidal activity of AgNPs such as shape, size, crystallinity, pH, and surface coating/charge have also been described in detail. The review also sheds light on antimicrobial photodynamic therapy and the role of AgNPs versus Ag⁺ ions release in bactericidal activities. In addition, different methods of synthesis of AgNPs have been discussed in brief.

Advances in Non-Animal Testing Approaches towards Accelerated Clinical Translation of Novel Nanotheranostic Therapeutics for Central Nervous System Disorders

Nanotheranostics constitute a novel drug delivery system approach to improving systemic, brain-targeted delivery of diagnostic imaging agents and pharmacological moieties in one rational carrier platform. While there have been notable successes in this field, currently, the clinical translation of such delivery systems for the treatment of neurological disorders has been limited by the inadequacy of correlating in vitro and in vivo data on blood-brain barrier (BBB) permeation and biocompatibility of nanomaterials. This review aims to identify the most contemporary non-invasive approaches for BBB crossing using nanotheranostics as a novel drug delivery strategy and current non-animal-based models for assessing the safety and efficiency of such formulations. This review will also address current and future directions of select in vitro models for reducing the cumbersome and laborious mandate for testing exclusively in animals. It is hoped these non-animal-based modelling approaches will facilitate researchers in optimising promising multifunctional nanocarriers with a view to accelerating clinical testing and authorisation applications. By rational design and appropriate selection of characterised and validated models, ranging from monolayer cell cultures to organ-on-chip microfluidics, promising nanotheranostic particles with modular and rational design can be screened in high-throughput models with robust predictive power. Thus, this article serves to highlight abbreviated research and development possibilities with clinical translational relevance for developing novel nanomaterial-based neuropharmaceuticals for therapy in CNS disorders. By generating predictive data for prospective nanomedicines using validated in vitro models for supporting clinical applications in lieu of requiring extensive use of in vivo animal models that have notable limitations, it is hoped that there will be a burgeoning in the nanotherapy of CNS disorders by virtue of accelerated lead identification through screening, optimisation through rational design for brain-targeted delivery across the BBB and clinical testing and approval using fewer animals. Additionally, by using models with tissue of human origin, reproducible therapeutically relevant nanomedicine delivery and individualised therapy can be realised.

Ovarian toxicity of nanoparticles

The ovary is a highly important organ for female reproduction. The main functions include sex steroid hormone synthesis, follicular development, and achievement of oocyte meiotic and development competence for proper fertilization. Nanoparticle (NP) exposure is becoming unavoidable because of its wide use in different products, including cosmetics, food, health, and personal care products. Studies examining different nonreproductive tissues or systems have shown that characteristics such as the size, shape, core material, agglomeration, and dissolution influence the effects of NPs. However, most studies evaluating NP-mediated reproductive toxicity have paid little or no attention to the influence of the physicochemical characteristics of NP on the observed effects. As accumulating evidence indicates that NP may reach the ovary to impair proper functions, this review summarizes the available data on NP accumulation in ovarian tissue, as well as data describing toxicity to ovarian functions, including sex steroid hormone production, follicular development, oocyte quality, and fertility. Due to their toxicological relevance, this review also describes the main physicochemical characteristics involved in NP toxicity and the importance of considering NP physicochemical characteristics as factors influencing the ovarian toxicity of NPs. Finally, this review summarizes the main mechanisms of toxicity described in ovarian cells.

Effects of metal nanoparticles on tight junction-associated proteins via HIF-1α/miR-29b/MMPs pathway in human epidermal keratinocytes

Background

The increasing use of metal nanoparticles in industry and biomedicine raises the risk for unintentional exposure. The ability of metal nanoparticles to penetrate the skin ranges from stopping at the stratum corneum to passing below the dermis and entering the systemic circulation. Despite the potential health risks associated with skin exposure to metal nanoparticles, the mechanisms underlying the toxicity of metal nanoparticles on skin keratinocytes remain unclear. In this study, we proposed that exposure of human epidermal keratinocytes (HaCaT) to metal nanoparticles, such as nickel nanoparticles, dysregulates tight-junction associated proteins by interacting with the HIF-1α/miR-29b/MMPs axis.

Methods

We performed dose-response and time-response studies in HaCaT cells to observe the effects of Nano-Ni or Nano-TiO₂ on the expression and activity of MMP-2 and MMP-9, and on the expression of tight junction-associated proteins, TIMP-1, TIMP-2, miR-29b, and HIF-1α. In the dose-response studies, cells were exposed to 0, 10, or 20 μg/mL of Nano-Ni or Nano-TiO₂ for 24 h. In the time-response studies, cells were exposed to 20 μg/mL of Nano-Ni for 12, 24, 48, or 72 h. After treatment, cells were collected to either assess the expression of mRNAs and miR-29b by real-time PCR or to determine the expression of tight junction-associated proteins and HIF-1α nuclear accumulation by Western blot and/or immunofluorescent staining; the conditioned media were collected to evaluate the MMP-2 and MMP-9 activities by gelatin zymography assay. To further investigate the mechanisms underlying Nano-Ni-induced dysregulation of tight junction-associated proteins, we employed a HIF-1α inhibitor, CAY10585, to perturb HIF-1α accumulation in one experiment, and transfected a miR-29b-3p mimic into the HaCaT cells before Nano-Ni exposure in another experiment. Cells and conditioned media were collected, and the expression and activities of MMPs and the expression of tight junction-associated proteins were determined as described above.

Results

Exposure of HaCaT cells to Nano-Ni resulted in a dose-dependent increase in the expression of MMP-2, MMP-9, TIMP-1, and TIMP-2 and the activities of MMP-2 and MMP-9. However, exposure of cells to Nano-TiO₂ did not cause these effects. Nano-Ni caused a dose-dependent decrease in the expression of miR-29b and tight junction-associated proteins, such as ZO-1, occludin, and claudin-1, while Nano-TiO₂ did not. Nano-Ni also caused a dose-dependent increase in HIF-1α nuclear accumulation. The time-response studies showed that Nano-Ni caused significantly increased expressions of MMP-2 at 24 h, MMP-9 at 12, 24, and 48 h, TIMP-1 from 24 to 72 h, and TIMP-2 from 12 to 72 h post-exposure. The expression of miR-29b and tight junction-associated proteins such as ZO-1, occludin, and claudin-1 decreased as early as 12 h post-exposure, and their levels declined gradually over time. Pretreatment of cells with a HIF-1α inhibitor, CAY10585, abolished Nano-Ni-induced miR-29b down-regulation and MMP-2/9 up-regulation. Introduction of a miR-29b-3p mimic into HaCaT cells by transfection before Nano-Ni exposure ameliorated Nano-Ni-induced increased expression and activity of MMP-2 and MMP-9 and restored Nano-Ni-induced down-regulation of tight junction-associated proteins.

Conclusion

Our study herein demonstrated that exposure of human epidermal keratinocytes to Nano-Ni caused increased HIF-1α nuclear accumulation and increased transcription and activity of MMP-2 and MMP-9 and down-regulation of miR-29b and tight junction-associated proteins. Nano-Ni-induced miR-29b down-regulation was through Nano-Ni-induced HIF-1α nuclear accumulation. Restoration of miR-29b level by miR-29b-3p mimic transfection abolished Nano-Ni-induced MMP-2 and MMP-9 activation and down-regulation of tight junction-associated proteins. In summary, our results demonstrated that Nano-Ni-induced dysregulation of tight junction-associated proteins in skin keratinocytes was via HIF-1α/miR-29b/MMPs pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00405-2.

Cellular, Molecular and Biochemical Impacts of Silver Nanoparticles on Rat Cerebellar Cortex

BACKGROUND

The excessive exposure to silver nanoparticles (Ag-NPs) has raised concerns about their possible risks to the human health. The brain is a highly vulnerable organ to nano-silver harmfulness. The aim of this work was to evaluate the impacts of Ag-NPs exposure on the cerebellar cortex of rats.

METHODS

Rats were assigned to: Control, vehicle control and Ag-NP-exposed groups (at doses of 10 mg and 30 mg/kg/day). Samples were processed for light and electron microscopy examinations. Immunohistochemical localization of c-Jun N-terminal kinase (JNK), nuclear factor kappa beta (NF-κB) and calbindin D28k (CB) proteins was performed. Analyses of expression of DNA damage inducible transcript 4 (Ddit4), flavin containing monooxygenase 2 (FMO2) and thioredoxin-interacting protein (Txnip) genes were done. Serum levels of inflammatory cytokines were also measured.

RESULTS

Ag-NPs enhanced apoptosis as evident by upregulation of Ddit4 gene expressions and JNK protein immune expressions. Alterations of redox homeostasis were verified by enhancement of Txnip and FMO2 gene expressions, favoring the activation of inflammatory responses by increasing NF-κB protein immune expressions and serum inflammatory mediator levels. Another cytotoxic effect was the reduction of immune expressions of the calcium regulator CB.

CONCLUSION

Ag-NPs exposure provoked biochemical, cellular and molecular changes of rat cerebellar cortex in a dose-dependent manner.

Developmental Neurotoxicity Screening for Nanoparticles Using Neuron-Like Cells of Human Umbilical Cord Mesenchymal Stem Cells: Example with Magnetite Nanoparticles

Metallic nanoparticles (NPs), as iron oxide NPs, accumulate in organs, cross the blood-brain barrier and placenta, and have the potential to elicit developmental neurotoxicity (DNT). Human stem cell-derived in vitro models may provide more realistic platforms to study NPs effects on neural cells, and to obtain relevant information on the potential for early or late DNT effects in humans. Primary neuronal-like cells (hNLCs) were generated from mesenchymal stem cells derived from human umbilical cord lining and the effects caused by magnetite (Fe₃O₄NPs, 1-50 μg/mL) evaluated. Neuronal differentiation process was divided into stages: undifferentiated, early, mid- and fully-differentiated (from day-2 to 8 of induction) based on different neuronal markers and morphological changes over time. Reduction in neuronal differentiation induction after NP exposure was observed associated with NP uptake: β-tubulin III (β-Tub III), microtubule-associated protein 2 (MAP-2), enolase (NSE) and nestin were downregulated (10-40%), starting from 25 μg/mL at the early stage. Effects were exacerbated at higher concentrations and persisted up to 8 days without cell morphology alterations. Adenosine triphosphate (ATP) and caspase-3/7 activity data indicated Fe₃O₄NPs-induced cell mortality in a concentration-dependent manner and increases of apoptosis: effects appeared early (from day-3), started at low concentrations (≥5 μg/mL) and persisted. This new human cell-based model allows different stages of hNLCs to be cultured, exposed to NPs/chemicals, and analyzed for different endpoints at early or later developmental stage.

Astrocytes Are More Vulnerable than Neurons to Silicon Dioxide Nanoparticle Toxicity in Vitro

Some studies have shown that silicon dioxide nanoparticles (SiO₂-NPs) can reach different regions of the brain and cause toxicity; however, the consequences of SiO₂-NPs exposure on the diverse brain cell lineages is limited. We aimed to investigate the neurotoxic effects of SiO₂-NP (0–100 µg/mL) on rat astrocyte-rich cultures or neuron-rich cultures using scanning electron microscopy, Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR), FTIR microspectroscopy mapping (IQ mapping), and cell viability tests. SiO₂-NPs were amorphous particles and aggregated in saline and culture media. Both astrocytes and neurons treated with SiO₂-NPs showed alterations in cell morphology and changes in the IR spectral regions corresponding to nucleic acids, proteins, and lipids. The analysis by the second derivative revealed a significant decrease in the signal of the amide I (α-helix, parallel β-strand, and random coil) at the concentration of 10 µg/mL in astrocytes but not in neurons. IQ mapping confirmed changes in nucleic acids, proteins, and lipids in astrocytes; cell death was higher in astrocytes than in neurons (10–100 µg/mL). We conclude that astrocytes were more vulnerable than neurons to SiO₂-NPs toxicity. Therefore, the evaluation of human exposure to SiO₂-NPs and possible neurotoxic effects must be followed up.

Silver nanoparticles: Synthesis, medical applications and biosafety

Silver nanoparticles (AgNPs) have been one of the most attractive nanomaterials in biomedicine due to their unique physicochemical properties. In this paper, we review the state-of-the-art advances of AgNPs in the synthesis methods, medical applications and biosafety of AgNPs. The synthesis methods of AgNPs include physical, chemical and biological routes. AgNPs are mainly used for antimicrobial and anticancer therapy, and also applied in the promotion of wound repair and bone healing, or as the vaccine adjuvant, anti-diabetic agent and biosensors. This review also summarizes the biological action mechanisms of AgNPs, which mainly involve the release of silver ions (Ag+), generation of reactive oxygen species (ROS), destruction of membrane structure. Despite these therapeutic benefits, their biological safety problems such as potential toxicity on cells, tissue, and organs should be paid enough attention. Besides, we briefly introduce a new type of Ag particles smaller than AgNPs, silver Ångstrom (Å, 1 Å = 0.1 nm) particles (AgÅPs), which exhibit better biological activity and lower toxicity compared with AgNPs. Finally, we conclude the current challenges and point out the future development direction of AgNPs.

Nanotechnology as a Platform for the Development of Injectable Parenteral Formulations: A Comprehensive Review of the Know-Hows and State of the Art

Within recent decades, the development of nanotechnology has made a significant contribution to the progress of various fields of study, including the domains of medical and pharmaceutical sciences. A substantially transformed arena within the context of the latter is the development and production of various injectable parenteral formulations. Indeed, recent decades have witnessed a rapid growth of the marketed and pipeline nanotechnology-based injectable products, which is a testimony to the remarkability of the aforementioned contribution. Adjunct to the ability of nanomaterials to deliver the incorporated payloads to many different targets of interest, nanotechnology has substantially assisted to the development of many further facets of the art. Such contributions include the enhancement of the drug solubility, development of long-acting locally and systemically injectable formulations, tuning the onset of the drug’s release through the endowment of sensitivity to various internal or external stimuli, as well as adjuvancy and immune activation, which is a desirable component for injectable vaccines and immunotherapeutic formulations. The current work seeks to provide a comprehensive review of all the abovementioned contributions, along with the most recent advances made within each domain. Furthermore, recent developments within the domains of passive and active targeting will be briefly debated.

Neurotoxicology of Nanomaterials

The remarkable advances coming about through nanotechnology promise to revolutionize many aspects of modern life; however, these advances come with a responsibility for due diligence to ensure that they are not accompanied by adverse consequences for human health or the environment. Many novel nanomaterials (having at least one dimension <100 nm) could be highly mobile if released into the environment and are also very reactive, which has raised concerns for potential adverse impacts including, among others, the potential for neurotoxicity. Several lines of evidence led to concerns for neurotoxicity, but perhaps none more than observations that inhaled nanoparticles impinging on the mucosal surface of the nasal epithelium could be internalized into olfactory receptor neurons and transported by axoplasmic transport into the olfactory bulbs without crossing the blood-brain barrier. From the olfactory bulb, there is concern that nanomaterials may be transported deeper into the brain and affect other brain structures. Of course, people will not be exposed to only engineered nanomaterials, but rather such exposures will occur in a complex mixture of environmental materials, some of which are incidentally generated particles of a similar inhalable size range to engineered nanomaterials. To date, most experimental studies of potential neurotoxicity of nanomaterials have not considered the potential exposure sources and pathways that could lead to exposure, and most studies of nanomaterial exposure have not considered potential neurotoxicity. Here, we present a review of potential sources of exposures to nanoparticles, along with a review of the literature on potential neurotoxicity of nanomaterials. We employ the linked concepts of an aggregate exposure pathway (AEP) and an adverse outcome pathway (AOP) to organize and present the material. The AEP includes a sequence of key events progressing from material sources, release to environmental media, external exposure, internal exposure, and distribution to the target site. The AOP begins with toxicant at the target site causing a molecular initiating event and, like the AEP, progress sequentially to actions at the level of the cell, organ, individual, and population. Reports of nanomaterial actions are described at every key event along the AEP and AOP, except for changes in exposed populations that have not yet been observed. At this last stage, however, there is ample evidence of population level effects from exposure to ambient air particles that may act similarly to engineered nanomaterials. The data give an overall impression that current exposure levels may be considerably lower than those reported experimentally to be neurotoxic. This impression, however, is tempered by the absence of long-term exposure studies with realistic routes and levels of exposure to address concerns for chronic accumulation of materials or damage. Further, missing across the board are "key event relationships", which are quantitative expressions linking the key events of either the AEP or the AOP, making it impossible to quantitatively project the likelihood of adverse neurotoxic effects from exposure to nanomaterials or to estimate margins of exposure for such relationships.

Adaptive changes induced by noble-metal nanostructures in vitro and in vivo

The unique features of noble-metal nanostructures (NMNs) are leading to unprecedented expansion of research and exploration of their application in therapeutics, diagnostics and bioimaging fields. With the ever-growing applications of NMNs, both therapeutic and environmental NMNs are likely to be exposed to tissues and organs, requiring careful studies towards their biological effects in vitro and in vivo. Upon NMNs exposure, tissues and cells may undergo a series of adaptive changes both in morphology and function. At the cellular level, the accumulation of NMNs in various subcellular organelles including lysosomes, endoplasmic reticulum, Golgi apparatus, mitochondria, and nucleus may interfere with their functions, causing changes in a variety of cellular functions, such as digestion, protein synthesis and secretion, energy metabolism, mitochondrial respiration, and proliferation. In animals, retention of NMNs in metabolic-, respiratory-, immune-related, and other organs can trigger significant physiological and pathological changes to these organs and influence their functions. Exploring how NMNs interact with tissues and cells and the underlying mechanisms are of vital importance for their future applications. Here, we illustrate the characteristics of NMNs-induced adaptive changes both in vitro and in vivo. Potential strategies in the design of NMNs are also discussed to take advantage of beneficial adaptive changes and avoid unfavorable changes for the proper implementation of these nanoplatforms.

Crossing Biological Barriers by Engineered Nanoparticles

Engineered nanoparticles (ENPs) may cause toxicity if they cross various biological barriers and are accumulated in vital organs. Which factors affect barrier crossing efficiency of ENPs are crucial to understand. Here, we present strong data showing that various nanoparticles crossed biological barriers to enter vital animal organs and cause toxicity. We also point out that physicochemical properties of ENPs, modifications of ENPs in biofluid, and physiological and pathological conditions of the body all affect barrier crossing efficiency. We also summarized our limited understanding of the related mechanisms. On the basis of this summary, major research gaps and direction of further efforts are then discussed.

Hazard characterization of silver nanoparticles for human exposure routes

Silver nanoparticles (AgNPs) have been widely used for a multitude of applications without full comprehensive knowledge regarding their safety. In particular, lack of data on hazard characterization may lead to uncertainties regarding potential human health risk. To provide the foundation for human health risk assessment of AgNPs, this study evaluates existing hazard characterization data, including reported pharmacokinetics, symptoms, and their corresponding dose-response relationships. Human equivalent relationships are also provided by extrapolation from animal dose-response relationships. From the data analyzed, it appears that AgNPs may persist for long periods (from days to years) in the human body. It was found that AgNP toxicity on traditional major targets of exogenous substances were generally underestimated. Some omissions of toxicity on sensitive systems in the AgNP toxicity assessment require attention, such as reprotoxicity and neurotoxicity. The necessity of the establishment of toxicity tests specifically for nanomaterials is highlighted. The scientific basis of a toxicity testing strategy is advised by this study, which paves the way for the monitoring and regulation of the ENP utilization in various industries.

The role of sex in particle-induced inflammation and injury

The use of engineered nanomaterials within various applications such as medicine, electronics, and cosmetics has been steadily increasing; therefore, the rate of occupational and environmental exposures has also increased. Inhalation is an important route of exposure to nanomaterials and has been shown to cause various respiratory diseases in animal models. Human lung disease frequently presents with a sex/gender-bias in prevalence or severity, but investigation of potential sex-differences in the adverse health outcomes associated with nanoparticle inhalation is greatly lacking. Only ~20% of basic research in the general sciences use both male and female animals and a substantial percentage of these do not address differences between sexes within their analyses. This has prevented researchers from fully understanding the impact of sex-based variables on health and disease, particularly the pathologies resulting from the inhalation of particles. The mechanisms responsible for sex-differences in respiratory disease remain unclear, but could be related to a number of variables including sex-differences in hormone signaling, lung physiology, or respiratory immune function. By incorporating sex-based analysis into respiratory nanotoxicology and utilizing human data from other relevant particles (e.g., asbestos, silica, particulate matter), we can improve our understanding of sex as a biological variable in nanoparticle exposures. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

A Role for Nanoparticles in Treating Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the main causes of disability in children and young adults, as well as a significant concern for elderly individuals. Depending on the severity, TBI can have a long-term impact on the quality of life for survivors of all ages. The primary brain injury can result in severe disability or fatality, and secondary brain damage can increase the complexities in cellular, inflammatory, neurochemical, and metabolic changes in the brain, which can last decades post-injury. Thus, survival from a TBI is often accompanied by lifelong disabilities. Despite the significant morbidity, mortality, and economic loss, there are still no effective treatment options demonstrating an improved outcome in a large multi-center Phase III trial, which can be partially attributed to poor target engagement of delivered therapeutics. Thus, there is a significant unmet need to develop more effective delivery strategies to overcome the biological barriers that would otherwise inhibit transport of materials into the brain to prevent the secondary long-term damage associated with TBI. The complex pathology of TBI involving the blood-brain barrier (BBB) has limited the development of effective therapeutics and diagnostics. Therefore, it is of great importance to develop novel strategies to target the BBB. The leaky BBB caused by a TBI may provide opportunities for therapeutic delivery via nanoparticles (NP). The focus of this review is to provide a survey of NP-based strategies employed in preclinical models of TBI and to provide insights for improved NP based diagnostic or treatment approaches. Both passive and active delivery of various NPs for TBI are discussed. Finally, potential therapeutic targets where improved NP-mediated delivery could increase target engagement are identified with the overall goal of providing insight into open opportunities for NP researchers to begin research in TBI.

Comparative study of in vitro effects of different nanoparticles at non-cytotoxic concentration on the adherens junction of human vascular endothelial cells

Background

Effects of different nanoparticles (NPs) exposure at acutely non-cytotoxic concentrations are particularly worthy to figure out, compare, and elucidate.

Objective

To investigate and compare the effect of a small library of NPs at non-cytotoxic concentration on the adherens junction of human umbilical vein endothelial cells (HUVECs), obtaining new insights of NPs safety evaluation.

Materials and methods

The HUVECs layer was exposed to NPs including gold (Au), platinum (Pt), silica (SiO₂), titanium dioxide (TiO₂), ferric oxide (Fe₂O₃), oxidized multi-walled carbon nanotubes, with different surface chemistry and size distribution. Cellular uptake of NPs was observed by transmission electron microscopy. and the cytotoxicity was determined by Cell Counting Kit-8 assay. The NP-induced variation of intracellular reactive oxygen species (ROS) and catalase (CAT) activity was measured using the probe of 2'7'-dichlorodihydr fluorescein diacetate and a CAT analysis kit, respectively. The level of VE-cadherin of HUVECs was analyzed by Western blot, and the loss of adherens junction was observed with laser confocal microscopy.

Results

The acutely non-cytotoxic concentrations of different NPs were determined and applied to HUVECs. The NPs increased the level of intracellular ROS and the activity of CAT to different degrees, depending on the characteristics. At the same time, the HUVECs lost their adherens junction protein VE-cadherin and gaps were formed between the cells. The NP-induced oxidative stress and gap formation could be rescued by the supplementary N-acetylcysteine in the incubation.

Conclusion

The increase of intracellular ROS and CAT activity was one common effect of NPs, even at the non-cytotoxic concentration, and the degree was dependent on the composition, surface chemistry, and size distribution of the NP. The effect led to the gap formation between the cells, while could be rescued by the antioxidant. Therefore, the variation of adherens junction between endothelial cells was suggested to evaluate for NPs when used as therapeutics and diagnostics.

The neurotoxicity induced by engineered nanomaterials

Engineered nanomaterials (ENMs) have been widely used in various fields due to their novel physicochemical properties. However, the use of ENMs has led to an increased exposure in humans, and the safety of ENMs has attracted much attention. It is universally acknowledged that ENMs could enter the human body via different routes, eg, inhalation, skin contact, and intravenous injection. Studies have proven that ENMs can cross or bypass the blood-brain barrier and then access the central nervous system and cause neurotoxicity. Until now, diverse in vivo and in vitro models have been developed to evaluate the neurotoxicity of ENMs, and oxidative stress, inflammation, DNA damage, and cell death have been identified as being involved. However, due to various physicochemical properties of ENMs and diverse study models in existing studies, it remains challenging to establish the structure-activity relationship of nanomaterials in neurotoxicity. In this paper, we aimed to review current studies on ENM-induced neurotoxicity, with an emphasis on the molecular and cellular mechanisms involved. We hope to provide a rational material design strategy for ENMs when they are applied in biomedical or other engineering applications.

Bactericidal and Cytotoxic Properties of Silver Nanoparticles

Silver nanoparticles (AgNPs) can be synthesized from a variety of techniques including physical, chemical and biological routes. They have been widely used as nanomaterials for manufacturing cosmetic and healthcare products, antimicrobial textiles, wound dressings, antitumor drug carriers, etc. due to their excellent antimicrobial properties. Accordingly, AgNPs have gained access into our daily life, and the inevitable human exposure to these nanoparticles has raised concerns about their potential hazards to the environment, health, and safety in recent years. From in vitro cell cultivation tests, AgNPs have been reported to be toxic to several human cell lines including human bronchial epithelial cells, human umbilical vein endothelial cells, red blood cells, human peripheral blood mononuclear cells, immortal human keratinocytes, liver cells, etc. AgNPs induce a dose-, size- and time-dependent cytotoxicity, particularly for those with sizes ≤10 nm. Furthermore, AgNPs can cross the brain blood barrier of mice through the circulation system on the basis of in vivo animal tests. AgNPs tend to accumulate in mice organs such as liver, spleen, kidney and brain following intravenous, intraperitoneal, and intratracheal routes of administration. In this respect, AgNPs are considered a double-edged sword that can eliminate microorganisms but induce cytotoxicity in mammalian cells. This article provides a state-of-the-art review on the synthesis of AgNPs, and their applications in antimicrobial textile fabrics, food packaging films, and wound dressings. Particular attention is paid to the bactericidal activity and cytotoxic effect in mammalian cells.

Prolonged Exposure to Silver Nanoparticles Results in Oxidative Stress in Cerebral Myelin

Currently, silver nanoparticles (AgNPs) are frequently used in a wide range of medical and consumer products. Substantial usage of AgNPs is considered to create substantive risks to both the environment and the human health. Since there is increasing evidence that the main mechanism of toxicity of AgNPs relates to oxidative stress, in the current study we investigate oxidative stress-related biochemical parameters in myelin isolated from adult rat brain subjected to a low dose of AgNPs. Animals were exposed for 2 weeks to 0.2 mg/kg b.w. of small (10 nm) AgNPs stabilized in citrate buffer or silver citrate established as a control to compare the effects of particulate and ionic forms of silver. We observe enhanced peroxidation of lipids and decreased concentrations of protein and non-protein –SH groups in myelin membranes. Simultaneously, expression of superoxide dismutase, a free radical scavenger, is increased whereas the process of protein glutathionylation, being a cellular protective mechanism against irreversible oxidation, is found to be inefficient. Results indicate that oxidative stress-induced alterations in myelin membranes may be the cause of ultrastructural disturbances in myelin sheaths.

Comparing the role of Ginkgolide B and Ginkgolide K on cultured astrocytes exposed to oxygen‑glucose deprivation

Ginkgolide B (GB) and ginkgolide K (GK) are two main active monomers of ginkgolides that present a unique group of diterpenes found naturally in the leaves of the Ginkgo biloba tree. Astrocytes are the most abundant cell type within the central nervous system (CNS) and serve essential roles in maintaining healthy brain function. The present study compared the biological effects of GB and GK on astrocytes exposed to oxygen-glucose deprivation (OGD). The results demonstrated that GB and GK exhibit many different actions. The level of the platelet-activating factor (PAF) was elevated on astrocytes exposed to OGD, and inhibited by GB and GK treatment. Although GB and GK inhibited the expression of p-NF-κB/p65, GK exerted stronger anti-inflammatory and antioxidant effects on astrocytes exposed to OGD than GB by inhibiting interleukin (IL)-6 and tumor necrosis factor-α, and inducing IL-10 and the nuclear factor-erythroid 2-related factor 2/HO-1 signaling pathway. When compared with GB treatment, GK treatment maintained high levels of phosphoinositide 3-kinase/phosphorylated-protein kinase B expression, and induced a marked upregulation of Wnt family member 1 and brain derived neurotrophic factor, indicating that GK, as a natural plant compound, may have more attractive prospects for clinical application in the treatment of neurological disorders than GB.

Noninvasive Brain Tumor Imaging Using Red Emissive Carbonized Polymer Dots across the Blood-Brain Barrier

Surgical resection is recognized as a mainstay in the therapy of malignant brain tumors. In clinical practice, however, surgeons face great challenges in identifying the tumor boundaries due to the infiltrating and heterogeneous nature of neoplastic tissues. Contrast-enhanced magnetic resonance imaging (MRI) is extensively used for defining the brain tumor in clinic. Disappointingly, the commercially available (MR) contrast agents show the transient circulation lifetime and poor blood-brain barrier (BBB) permeability, which seriously hamper their abilities in tumor visualization. In this work, red fluorescent carbonized polymer dots (CPDs) were systematically investigated with respect to their BBB-penetration ability. In summary, CPDs possess long excitation/emission wavelengths, low toxicity, high photostability, and excellent biocompatibility. CPDs exhibit high internalization in glioma cells in time- and dose-dependent procedures, and internalized CPDs locate mainly in endolysosomal structures. In vitro and in vivo studies confirmed the BBB permeability of CPDs, contributing to the early stage diagnosis of brain disorders and the noninvasive visualization of the brain tumor without compromised BBB. Furthermore, owing to the high tumor to normal tissue ratio of CPDs under ex vivo conditions, our nanoprobe holds the promise to guide brain-tumor resection by real-time fluorescence imaging during surgery.

Silica nanoparticle exposure during the neonatal period impairs hippocampal precursor proliferation and social behavior later in life

Introduction

Silica nanoparticles (SiO₂-NPs) are currently among the most widely used nanomaterials, but their potentially adverse effects on brain development remain unknown. The developing brain is extremely sensitive to NP neurotoxicity during the early postnatal period.

Materials and methods

Herein, we investigated the effects of SiO₂-NPs (doses of 10, 20, or 50 mg with a particle size of ~91 nm, equivalent to aerosol mass concentrations 55.56, 111.11, and 277.78 mg/m³, respectively) exposure from postnatal day (P) 1 to P7 on hippocampal precursor proliferation at P8 and long-term neurobehavior in adults.

Results

SiO₂-NP exposure resulted in inflammatory cell infiltration in lung tissue, microglia over-activation in the hippocampal dentate gyrus (DG), and decreased hippocampal precursor proliferation in the DG-subgranular zone at P8. Moreover, after exposure to 20 mg of SiO_2-NPs, mice exhibited social interaction deficits and slight anxiety-like behaviors in adulthood, but this exposure did not induce locomotor activity impairment, depression-like behavior, or short-term memory impairment.

Discussion

These findings suggest that early-age SiO₂-NP exposure induced inflammation and inhibited precursor proliferation in the DG in a dose-dependent manner, which might be related to the social dysfunction observed in adulthood.

Reduced Zebrafish Transcriptome Atlas toward Understanding Environmental Neurotoxicants

Transcriptomic approaches monitoring gene responses at genome-scale are increasingly used in toxicological research and help to clarify the molecular mechanisms of adverse effects caused by environmental toxicants. However, their applications for chemical assessment are hampered due to high expenses required and more importantly the lack of in-depth data mining and mechanistic perspectives. Here, we described a reduced transcriptome atlas (RTA) approach which integrates transcriptomic data sets and a comprehensive panel of genes generated to represent neurogenesis and the early neuronal development of zebrafish, to determine the potential neurodevelopmental toxicities of environmental chemicals. Transcriptomic data sets of 74 chemicals and 736 related gene expression profiles were integrated resulting in 135 exposure signatures. Chemical prioritization demonstrated four sets of hits to be neurotoxic: neuro-active chemicals (representatively, Valproic acid, VPA and Carbamazepine, CAR), xenoestrogens (Bisphenol A, BPA; Genistein, GEN; 17-α ethinylestradiol, EE2), microcystins (cyanopeptolin, CP1020; microcystin-LR, MCLR) and heavy metals (AgNO₃, AgNPs). The enriched biological pathways and processes were distinct among the four sets, while the overlapping functional enrichments were observed within each set, for example, over 25% differentially expressed genes and four of top five KEGG pathways were shared between VPA and CAR. Furthermore, gene expression index (GEI) analysis demonstrated that a gene panel with 300 genes was sufficient to effectively characterize and cluster chemicals and therefore offer an efficient and cost-effective tool for the prioritization of neurotoxicants. Thus, the RTA approach provides novel insights into the understanding of the in-depth molecular mechanisms of environmental neurotoxicants and can be used as an indication for potential adverse outcomes.

Carbon Nanotubes and Other Engineered Nanoparticles Induced Pathophysiology on Mesothelial Cells and Mesothelial Membranes

Nanoparticles have great potential for numerous applications due to their unique physicochemical properties. However, concerns have been raised that they may induce deleterious effects on biological systems. There is accumulating evidence that, like asbestos, inhaled nanomaterials of >5 μm and high aspect ratio (3:1), particularly rod-like carbon nanotubes, may inflict pleural disease including mesothelioma. Additionally, a recent set of case reports suggests that inhalation of polyacrylate/nanosilica could in part be associated with inflammation and fibrosis of the pleura of factory workers. However, the adverse outcomes of nanoparticle exposure to mesothelial tissues are still largely unexplored. In that context, the present review aims to provide an overview of the relevant pathophysiological implications involving toxicological studies describing effects of engineered nanoparticles on mesothelial cells and membranes. In vitro studies primarily emphasize on simulating cellular uptake and toxicity of nanotubes on benign or malignant cell lines. On the other hand, in vivo studies focus on illustrating endpoints of serosal pathology in rodent animal models. From a molecular aspect, some nanoparticle categories are shown to be cytotoxic and genotoxic after acute treatment, whereas chronic incubation may lead to malignant-like transformation. At an organism level, a number of fibrous shaped nanotubes are related with features of chronic inflammation and MWCNT-7 is the only type to consistently inflict mesothelioma.

Gut Dysbiosis and Neurobehavioral Alterations in Rats Exposed to Silver Nanoparticles

Due to their antimicrobial properties, silver nanoparticles (AgNPs) are being used in non-edible and edible consumer products. It is not clear though if exposure to these chemicals can exert toxic effects on the host and gut microbiome. Conflicting studies have been reported on whether AgNPs result in gut dysbiosis and other changes within the host. We sought to examine whether exposure of Sprague-Dawley male rats for two weeks to different shapes of AgNPs, cube (AgNC) and sphere (AgNS) affects gut microbiota, select behaviors, and induces histopathological changes in the gastrointestinal system and brain. In the elevated plus maze (EPM), AgNS-exposed rats showed greater number of entries into closed arms and center compared to controls and those exposed to AgNC. AgNS and AgNC treated groups had select reductions in gut microbiota relative to controls. Clostridium spp., Bacteroides uniformis, Christensenellaceae, and Coprococcus eutactus were decreased in AgNC exposed group, whereas, Oscillospira spp., Dehalobacterium spp., Peptococcaeceae, Corynebacterium spp., Aggregatibacter pneumotropica were reduced in AgNS exposed group. Bacterial reductions correlated with select behavioral changes measured in the EPM. No significant histopathological changes were evident in the gastrointestinal system or brain. Findings suggest short-term exposure to AgNS or AgNC can lead to behavioral and gut microbiome changes.

Silver nanoparticles reduce brain inflammation and related neurotoxicity through induction of H2S-synthesizing enzymes

Silver nanoparticles (AgNP) are known to penetrate into the brain and cause neuronal death. However, there is a paucity in studies examining the effect of AgNP on the resident immune cells of the brain, microglia. Given microglia are implicated in neurodegenerative disorders such as Parkinson's disease (PD), it is important to examine how AgNPs affect microglial inflammation to fully assess AgNP neurotoxicity. In addition, understanding AgNP processing by microglia will allow better prediction of their long term bioreactivity. In the present study, the in vitro uptake and intracellular transformation of citrate-capped AgNPs by microglia, as well as their effects on microglial inflammation and related neurotoxicity were examined. Analytical microscopy demonstrated internalization and dissolution of AgNPs within microglia and formation of non-reactive silver sulphide (Ag2S) on the surface of AgNPs. Furthermore, AgNP-treatment up-regulated microglial expression of the hydrogen sulphide (H2S)-synthesizing enzyme cystathionine-γ-lyase (CSE). In addition, AgNPs showed significant anti-inflammatory effects, reducing lipopolysaccharide (LPS)-stimulated ROS, nitric oxide and TNFα production, which translated into reduced microglial toxicity towards dopaminergic neurons. Hence, the present results indicate that intracellular Ag2S formation, resulting from CSE-mediated H2S production in microglia, sequesters Ag+ ions released from AgNPs, significantly limiting their toxicity, concomitantly reducing microglial inflammation and related neurotoxicity.

Hydrothermal synthesis of nitrogen-doped carbon dots with real-time live-cell imaging and blood-brain barrier penetration capabilities

Nitrogen-doped carbon dots (N-CDs) were synthesized using a one-pot hydrothermal treatment with citric acid in the presence of polyethylenimine. Transmission electron microscopy analysis revealed that the N-CDs were monodispersed and quasi-spherical with an average size of ~2.6 nm. Under ultraviolet irradiation the N-CDs emitted a strong blue luminescence with a quantum yield as high as 51%. Moreover, the N-CDs exhibited a negligible cytotoxicity and could be applied as efficient nanoprobes for real-time imaging of live cells. In addition, the ability of the N-CDs to cross the blood–brain barrier (BBB) in a concentration-dependent manner was demonstrated using an in vitro BBB model. Therefore, these PEI-passivated N-CDs with real-time live-cell imaging and BBB-penetration capabilities hold promise for traceable drug delivery to the brain.