Engineered Nanomaterials for Immunomodulation: A Review

The immune system usually provides a defense against invading pathogenic microorganisms and any other particulate contaminants. Nonetheless, it has been recently reported that nanomaterials can evade the immune system and modulate immunological responses due to their unique physicochemical characteristics. Consequently, nanomaterial-based activation of immune components, i.e., neutrophils, macrophages, and other effector cells, may induce inflammation and alter the immune response. Here, it is essential to distinguish the acute and chronic modulations triggered by nanomaterials to determine the possible risks to human health. Nanomaterials size, shape, composition, surface charge, and deformability are factors controlling their uptake by immune cells and the resulting immune responses. The exterior corona of molecules adsorbed over nanomaterials surfaces also influences their immunological effects. Here, we review current nanoengineering trends for targeted immunomodulation with an emphasis on the design, safety, and potential toxicity of nanomaterials. First, we describe the characteristics of engineered nanomaterials that trigger immune responses. Then, the biocompatibility and immunotoxicity of nanoengineered particles are debated, because these factors influence applications. Finally, future nanomaterial developments in terms of surface modifications, synergistic approaches, and biomimetics are discussed.

Drug Self-Aggregation into Nano-Entities Has the Potential to Induce Immune Responses

The free-state solution behaviors of small molecules profoundly affect their respective properties. It is becoming more obvious that compounds can adopt a three-phase equilibrium when placed in an aqueous solution, among soluble-lone molecule form, self-assembled aggregate form (nano-entities), and solid precipitate form. Recently, correlations have emerged between the existence of self-assemblies into drug nano-entities and unintended side effects. This report describes our pilot study involving a selection of drugs and dyes to explore if there may be a correlation between the existence of drug nano-entities and immune responses. We first implement practical strategies for detecting the drug self-assemblies using a combination of nuclear magnetic resonance (NMR), dynamic light scattering (DLS), transmission electron microscopy (TEM), and confocal microscopy. We then used enzyme-linked immunosorbent assays (ELISA) to monitor the modulation of immune responses on two cellular models, murine macrophage and human neutrophils, upon exposure to the drugs and dyes. The results suggest that exposure to some aggregates correlated with an increase in IL-8 and TNF-α in these model systems. Given this pilot study, further correlations merit pursuing on a larger scale given the importance and potential impact of drug-induced immune-related side effects.

Interaction between iron oxide nanoparticles (IONs) and primary human immune cells: An up-to-date review of the literature

Nanotechnology has been gaining more and more momentum lately and the potential use of nanomaterials such as nanoparticles (NPs) continues to grow in a variety of activity sectors. Among the NPs, iron oxide nanoparticles (IONs) have retained an increasing interest from the scientific community and industrials due to their superparamagnetic properties allowing their use in many fields, including medicine. However, some undesired effects of IONs and potential risk for human health are becoming increasingly reported in several studies. Although many in vivo studies reported that IONs induce immunotoxicity in different animal models, it is not clear how IONs can alter the biology of primary human immune cells. In this article, we will review the works that have been done regarding the interaction between IONs and primary immune cells. This review also outlines the importance of using primary immune cells in risk assessment of NPs as a reliable strategy for encouraging non-animal studies approaches, to determine risks that might affect the human immune system following different exposure scenarios. Taken all together, the reported observations help to get a more global picture on how IONs alter the human immune system especially the fact that inflammation, known to involve several immune cell types, is frequently reported as an undesired effect of IONs.

Functional responsiveness of in vitro-aged human neutrophils

Elimination of apoptotic neutrophils by macrophages is as a major step for the resolution of inflammation. However, the fate and the cellular functionality of neutrophils aged in the absence of macrophages are not well documented. Herein, freshly isolated human neutrophils were aged for several days in vitro and then stimulated with agonists for determining their cell responsiveness. In vitro-aged neutrophils were still able to generate reactive oxygen species after 48 h, exert phagocytosis after 72 h, and increase their adhesion onto a cell substratum after 48 h. These data demonstrate that a portion of neutrophils cultivated for several days in vitro are still able to exert biological functions. This opens the possibility that, during inflammation, neutrophils may still respond to agonists, a condition that is likely to occur in vivo when they are not efficiently eliminated by efferocytosis.

Toxicological Aspects, Safety Assessment, and Green Toxicology of Silver Nanoparticles (AgNPs)—Critical Review: State of the Art

In recent years, research on silver nanoparticles (AgNPs) has attracted considerable interest among scientists because of, among other things, their alternative application to well-known medical agents with antibacterial properties. The size of the silver nanoparticles ranges from 1 to 100 nm. In this paper, we review the progress of research on AgNPs with respect to the synthesis, applications, and toxicological safety of AgNPs, and the issue of in vivo and in vitro research on silver nanoparticles. AgNPs’ synthesis methods include physical, chemical, and biological routes, as well as “green synthesis”. The content of this article covers issues related to the disadvantages of physical and chemical methods, which are expensive and can also have toxicity. This review pays special attention to AgNP biosafety concerns, such as potential toxicity to cells, tissues, and organs.

Nanotechnological advancements in the brain tumor therapy: a novel approach

Nanotechnological advancements over the past few years have led to the development of newer treatment strategies in brain cancer therapy which leads to the establishment of nano oncology. Nanostructures with high specificity, are best suitable to penetrate the blood-brain barrier (BBB). Their desired physicochemical properties, such as small sizes, shape, higher surface area to volume ratio, distinctive structural features, and the possibility to attach various substances on their surface transform them into potential transport carriers able to cross various cellular and tissue barriers, including the BBB. The review emphasizes nanotechnology-based treatment strategies for the exploration of brain tumors and highlights the current progress of different nanomaterials for the effective delivery of drugs for brain tumor therapy.

Impact of ultra-small silver nanoparticles of 2 nm (AgNP2) on neutrophil biology: AgNP2 alter the actin cytoskeleton and induce karyorrhexis by a mitogen-activated protein kinase-dependent mechanism in vitro and transitorily attract neutrophils in vivo

Silver (Ag) is known as an antibacterial agent and there is a growing interest to use silver nanoparticles (AgNPs) in a variety of medical applications and other sectors. Some studies reported that one of the undesired effects of AgNPs is inflammation and that these NPs can alter the biology of neutrophils. Since it is commonly accepted that the more NPs are small, the more toxic they are the aim of this study was to determine the impact of ultra-small silver nanoparticles of 2 nm (AgNP₂) on the biology of neutrophils, key player cells in inflammation. We report that AgNP₂ are potent neutrophil activators as they rapidly induce actin polymerization and dismantling the actin network. Although AgNP₂ are not necrotic for neutrophils and do not induce ROS production, kinetic studies reveal that AgNP₂ are rapid inducer of apoptosis. Pyknosis (mainly 1-2 large nuclear dots) was observed after only 1h of treatment followed by karyorrhexis (several small dots) and by a complete nuclear dissolution leading to anuclear neutrophils after 6h. These observations are not associated with the release of silver ions since treatment of neutrophils with 1-50 μg/ml AgNO₃ (as a source of Ag⁺) did not induce any apparent changes. AgNP₂ induce p38 and Erk-1/2 mitogen-activated protein kinase (MAPK) and although karyorrhexis was markedly reversed by MAPK inhibitors, the cell nuclei remain with a pyknotic-like phenotype but do not return to the characteristic polylobed nucleus. Using the murine air pouch model of inflammation AgNP₂ were found to induce a neutrophil influx. Our data indicate that AgNP₂ are potent neutrophil activators targeting the actin cytoskeleton and the mechanism involved for inducing apoptosis is rapid, complex, and partially includes MAPK pathways. Therefore, the ultra-small AgNP₂ are more potent than larger ones for inducing apoptosis and they can transitorily attract neutrophils in vivo.

Interaction between iron oxide nanoparticles (Fe3O4 NPs) and human neutrophils: Evidence that Fe3O4 NPs possess some pro-inflammatory activities

Iron oxide nanoparticles (Fe₃O₄ NPs) are important for different medical applications. However, potential toxicity has been reported and several parameters must still be studied to reach highest therapeutic efficacy with minimal undesired effects. Inflammation is one of the most reported undesired effects of NP exposure in a variety of inflammatory models and conflicting data exist regarding whether Fe₃O₄ NPs possess pro- or anti-inflammatory activities. The aim of this study was to determine the direct effect of Fe₃O₄ NPs on the biology of neutrophil, a key player cell in inflammation. Freshly isolated human neutrophils were incubated in vitro with Fe₃O₄ NPs, and several functions have been studied. Using transmission electronic microscopy, Fe₃O₄ NPs were found to be ingested by neutrophils. These NPs do not induce a respiratory burst by themselves, but they increase the ability of neutrophils to adhere onto human endothelial cells as well as enhance phagocytosis. An antibody array approach revealed that Fe₃O₄ NPs induce the production of some cytokines, including the chemokine IL-8 (CXCL8), which was confirmed by ELISA. Fe₃O₄NPs were found to delay spontaneous neutrophil apoptosis regardless of sex of the donor. Using a pharmacological approach, we demonstrate that Fe₃O₄ NPs delay apoptosis by a de novo protein synthesis-dependent mechanism and via different cell signalling pathways. The data indicate that Fe₃O₄ NPs can alter the biology of human neutrophils and that they possess some pro-inflammatory effects, particularly based on their capacity to delay apoptosis and to induce the production of pro-inflammatory cytokines. Therefore, Fe₃O₄ NPs can regulate inflammation by targeting human neutrophil functions.

Cancer Therapy by Silver Nanoparticles: Fiction or Reality?

As an emerging new class, metal nanoparticles and especially silver nanoparticles hold great potential in the field of cancer biology. Due to cancer-specific targeting, the consequently attenuated side-effects and the massive anti-cancer features render nanoparticle therapeutics desirable platforms for clinically relevant drug development. In this review, we highlight those characteristics of silver nanoparticle-based therapeutic concepts that are unique, exploitable, and achievable, as well as those that represent the critical hurdle in their advancement to clinical utilization. The collection of findings presented here will describe the features that distinguish silver nanoparticles from other anti-cancer agents and display the realistic opportunities and implications in oncotherapeutic innovations to find out whether cancer therapy by silver nanoparticles is fiction or reality.

Synergistic effects of silver nanoparticles and cisplatin in combating inflammation and hyperplasia of airway stents

Anti-inflammatory and antihyperplasia activities are essential requirements for the successful use of airway stents. In this work, silver nanoparticles (AgNPs) and cisplatin (DDP) were combined in a synergistic modification strategy to improve the surface function of airway stents. Using polycaprolactone (PCL) as a drug carrier, a dual-functional PCL-AgNPs-DDP fiber film-coated airway stent was fabricated by electrospinning. The physicochemical and biological properties of the obtained fiber films were examined. The ATR-FTIR, XPS, SEM-EDS and TEM results suggested that AgNPs and DDP could be successfully immobilized onto the airway stent surface. The drug release and surface degradation results revealed that AgNPs and DDP can undergo sustained release from films for 30 d, and the weight loss was approximately 50% after 35 d. In addition, the dual-functional fiber film suppressed human embryonic lung fibroblast growth and exhibited excellent antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. Furthermore, the effectiveness of the dual-functional fiber film-coated airway stent was evaluated by application to the trachea of New Zealand rabbits. The in vivo results indicated that PCL-AgNPs-DDP fiber film-coated airway stent can significantly inhibit granulation tissue formation and collagen deposition, reduced the expression of IL-8, TNF-α, IL-1α, PCNA, α-SMA and CD68, and ultimately achieved anti-inflammatory and antihyperplasia effects. Hence, this study provides a dual-functional surface-coated airway stent to address the clinical complications associated with respiratory tract inflammation and granulation tissue hyperplasia, thus inhibiting tracheal stenosis.

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This study provides a dual-functional PCL-AgNPs-DDP nanofiber film-coated airway stent.

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The airway stent processes antibacterial activity and suppress CCC-HPF-1 growth.

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The stent inhibits tracheal stenosis by antiinflammatory and antihyperplasia treatment.

Protective Role of Flavonoids against Intestinal Pro-Inflammatory Effects of Silver Nanoparticles

Silver nanoparticles (AgNP) have been increasingly incorporated into food-related and hygiene products for their unique antimicrobial and preservative properties. The consequent oral exposure may then result in unpredicted harmful effects in the gastrointestinal tract (GIT), which should be considered in the risk assessment and risk management of these materials. In the present study, the toxic effects of polyethyleneimine (PEI)-coated AgNP (4 and 19 nm) were evaluated in GIT-relevant cells (Caco-2 cell line as a model of human intestinal cells, and neutrophils as a model of the intestinal inflammatory response). This study also evaluated the putative protective action of dietary flavonoids against such harmful effects. The obtained results showed that AgNP of 4 and 19 nm effectively induced Caco-2 cell death by apoptosis with concomitant production of nitric oxide, irrespective of the size. It was also observed that AgNP induced human neutrophil oxidative burst. Interestingly, some flavonoids, namely quercetin and quercetagetin, prevented the deleterious effects of AgNP in both cell types. Overall, the data of the present study provide a first insight into the promising protective role of flavonoids against the potentially toxic effects of AgNP at the intestinal level.

Evaluating the Apoptotic Cell Death Modulatory Activity of Nanoparticles in Men and Women Neutrophils and Eosinophils

Apoptosis is an important cell death mechanism for the resolution of inflammation. Neutrophil spontaneous apoptosis rates were reported to be slightly different in men and women and to be modulated by female sex hormones. The aim of this study was to determine whether different nanoparticles (NPs) will alter the neutrophil and eosinophil apoptotic rates differently in men and women. Using the antiapoptotic cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) and the proapoptotic plant lectin Viscum album agglutinin-I (VAA-I) as controls, we found that these factors respectively delay and induce apoptosis in both neutrophils and eosinophils with apoptotic rates remarkably similar in both sexes. The polyamidoamine (PAMAM) dendrimers of generation 0 (G0) and G3 slightly, but not significantly, accelerate neutrophil apoptosis regardless of sex. Zinc oxide (ZnO), titanium dioxide (TiO₂), cerium dioxide (CeO₂), and palladium (Pd) but not platinum (Pt) NPs were found to significantly delay neutrophil apoptosis. When results were compared between men and women, only ZnO and Pd NPs were found to significantly delay neutrophil apoptosis in men while ZnO, TiO₂, CeO₂, and Pt NPs inhibit apoptosis in women neutrophils. In eosinophils, G3, but not G0 NPs, significantly accelerate apoptosis in women. ZnO, Pt, and Pd NPs significantly delay eosinophil apoptosis but only in women. Unlike neutrophils, TiO₂ and CeO₂ NPs did not significantly delay eosinophil apoptosis. We propose that future studies aiming at determining potential effect NPs on cellular biological processes should incorporate a sex-based analysis based on the differences reported here studying the impact of NPs on human granulocyte apoptosis.

Neutrophil and Nanoparticles Delivery to Tumor: Is It Going to Carry That Weight?

The application of cell carriers for transporting nanodrugs to the tumor draws much attention as the alternative to the passive drug delivery. In this concept, the neutrophil (NΦ) is of special interest as this cell is able to uptake nanoparticles (NPs) and cross the vascular barrier in response to tumor signaling. There is a growing body of literature describing NP-NΦ interactions in vitro and in vivo that demonstrates the opportunity of using these cells to improve the efficacy of cancer therapy. However, a number of conceptual and technical issues need to be resolved for translating the technology into clinics. The current review summarizes the recent advances and challenges associated with NP-NΦ interactions, with the special focus on the complex interplay between the NP internalization pathways and the modulation of NΦ activity, and its potential consequences for nanodrug delivery.

Pollen-Mimetic Metal-Organic Frameworks with Tunable Spike-Like Nanostructures That Promote Cell Interactions to Improve Antigen-Specific Humoral Immunity

The exine capsules of pollen particles exhibit a variety of characteristic surface morphologies that promote their cell interactions; their use as antigen carriers for vaccination has been proposed. However, the allergy-causing substances in pollen particles may not all be removed, even by vigorous chemical treatments. To resolve this issue, this work develops systemic approaches for synthesizing pollen-mimetic metal-organic frameworks (MOFs), which comprise aluminum (Al) ions and an organic linker (2-aminoterephthalic acid), with tunable spike-like nanostructures on their surfaces. The as-synthesized MOFs act not only as a delivery vehicle that carries a model antigen (ovalbumin, OVA) but also as an adjuvant (Al). Scanning and transmission electron microscopies images reveal that the aspect ratio of the nanospikes that are grown on the MOFs can be controlled. A higher aspect ratio of the nanospikes on the MOFs is associated with greater cell attachment and faster and more efficient phagocytosis in cells, which results in greater expressions of pro-inflammatory cytokines. Consequently, a more robust immune response against the antigen of interest is elicited. These findings have broad implications for the rational design of the future antigen/adjuvant-presenting particles for vaccination.

Silver Nanoparticles Induce Neutrophil Extracellular Traps Via Activation of PAD and Neutrophil Elastase

Silver nanoparticles (AgNPs) are widely used in various fields because of their antimicrobial properties. However, many studies have reported that AgNPs can be harmful to both microorganisms and humans. Reactive oxygen species (ROS) are a key factor of cytotoxicity of AgNPs in mammalian cells and an important factor in the immune reaction of neutrophils. The immune reactions of neutrophils include the expulsion of webs of DNA surrounded by histones and granular proteins. These webs of DNA are termed neutrophil extracellular traps (NETs). NETs allow neutrophils to catch and destroy pathogens in extracellular spaces. In this study, we investigated how AgNPs stimulate neutrophils, specifically focusing on NETs. Freshly isolated human neutrophils were treated with 5 or 100 nm AgNPs. The 5 nm AgNPs induced NET formation, but the 100 nm AgNPs did not. Subsequently, we investigated the mechanism of AgNP-induced NETs using known inhibitors related to NET formation. AgNP-induced NETs were dependent on ROS, peptidyl arginine deiminase, and neutrophil elastase. The result in this study indicates that treatment of 5 nm AgNPs induce NET formation through histone citrullination by peptidyl arginine deiminase and histone cleavage by neutrophil elastase.

Silver nanoparticles induced cytotoxicity in HT22 cells through autophagy and apoptosis via PI3K/AKT/mTOR signaling pathway

With the widespread application and inevitable environmental exposure, silver nanoparticles (AgNPs) can be accumulated in various organs. More serious concerns are raised on the biological safety and potential toxicity of AgNPs in the central nervous system (CNS), especially in the hippocampus. This study aimed to investigate the biological effects and the role of PI3K/AKT/mTOR signaling pathway in AgNPs mediated cytotoxicity using the mouse hippocampal neuronal cell line (HT22 cells). AgNPs reduced cell viability and induced membrane leakage in a dose-dependent manner, determined by the MTT and LDH assay. In doses of 25, 50, 100 μg mL^-1 for 24 h, AgNPs promoted the excessive production of reactive oxygen species (ROS) and caused the oxidative stress in HT22 cells. AgNPs induced autophagy, determined by the transmission electron microscopy observation, upregulation of LC3 II/I and downregulation of p62 expression levels. The mechanistic investigation showed that the PI3K/AKT/mTOR signaling pathway was activated by phosphorylation, which was enrolled in an AgNP-induced autophagy process. AgNPs could further trigger the apoptosis by upregulation of caspase-3 and Bax and downregulation of Bcl-2 in HT22 cells. These results revealed AgNP-induced cytotoxicity in HT22 cells, which was mediated by autophagy and apoptosis via the PI3K/AKT/mTOR signaling pathway. The study could provide the experimental evidence and explanation for the potential neurotoxicity triggered by AgNPs in vitro.

Biomaterial-Driven Immunomodulation: Cell Biology-Based Strategies to Mitigate Severe Inflammation and Sepsis

Inflammation is an essential component of a wide variety of disease processes and oftentimes can increase the deleterious effects of a disease. Finding ways to modulate this essential immune process is the basis for many therapeutics under development and is a burgeoning area of research for both basic and translational immunology. In addition to developing therapeutics for cellular and molecular targets, the use of biomaterials to modify innate and adaptive immune responses is an area that has recently sparked significant interest. In particular, immunomodulatory activity can be engineered into biomaterials to elicit heightened or dampened immune responses for use in vaccines, immune tolerance, or anti-inflammatory applications. Importantly, the inherent physicochemical properties of the biomaterials play a significant role in determining the observed effects. Properties including composition, molecular weight, size, surface charge, and others affect interactions with immune cells (i.e., nano-bio interactions) and allow for differential biological responses such as activation or inhibition of inflammatory signaling pathways, surface molecule expression, and antigen presentation to be encoded. Numerous opportunities to open new avenues of research to understand the ways in which immune cells interact with and integrate information from their environment may provide critical solutions needed to treat a variety of disorders and diseases where immune dysregulation is a key inciting event. However, to elicit predictable immune responses there is a great need for a thorough understanding of how the biomaterial properties can be tuned to harness a designed immunological outcome. This review aims to systematically describe the biological effects of nanoparticle properties-separate from additional small molecule or biologic delivery-on modulating innate immune cell responses in the context of severe inflammation and sepsis. We propose that nanoparticles represent a potential polypharmacological strategy to simultaneously modify multiple aspects of dysregulated immune responses where single target therapies have fallen short for these applications. This review intends to serve as a resource for immunology labs and other associated fields that would like to apply the growing field of rationally designed biomaterials into their work.

Silver nanoparticle immunomodulatory potential in absence of direct cytotoxicity in RAW 264.7 macrophages and MPRO 2.1 neutrophils

Engineered nanomaterials (ENM) are being used in a wide range of consumer products and pharmaceuticals; hence, there is an increasing risk for human exposure and potential adverse outcomes. The immune system, vital in host defense and protection against environmental agents, is typically initiated and executed by innate effector immune cells including macrophages and neutrophils. Previous literature has reported the immune system as a major target of ENM toxicity; however, there is inconsistency regarding the immunotoxicity of ENM. This could be attributed to differences in ENM physicochemical properties, cellular models examined, biocorona formation, etc. Thus, the current study examined the toxicity and immunomodulatory effects of silver nanoparticles (AgNP), one of the most utilized ENM in consumer and medical products, in two key innate immune cell models, e.g. RAW 264.7 cells (macrophages) and differentiated MPRO 2.1 cells (promyelocytes/neutrophils). The results showed that despite a generation of reactive oxygen species, exposure to 20 nm citrate-coated AgNP was not associated with major oxidative damage, inflammatory responses, nor cytotoxicity. Nevertheless, and most importantly, pre-exposure to the AgNP for 24 h enhanced RAW 264.7 cell phagocytic ability as well as the release of inflammatory cytokine interleukin-6 in response to lipopolysaccharide (LPS). In MPRO 2.1 cells, AgNP pre-exposure also resulted in enhanced phagocytic ability; however, these cells manifest reduced cell degranulation (elastase release) and oxidative burst in response to phorbol myristate acetate (PMA). Taken together, these findings indicated to us that exposure to AgNP, despite not being directly (cyto)toxic to these cells, had the potential to alter immune cell responses. The findings underscore the import of assessing immune cell function post-exposure to ENM beyond the standard endpoints such as oxidative stress and cytotoxicity. In addition, these findings further illustrate the importance of understanding the underlying molecular mechanisms of ENM-cellular interactions, particularly in the immune system.

Manilkara zapota (L.) P. Royen Leaf Extract Derived Silver Nanoparticles Induce Apoptosis in Human Colorectal Carcinoma Cells Without Affecting Human Lymphocytes or Erythrocytes

Plant-derived synthesis of silver nanoparticles (AgNPs) has found wide biomedical applications including cancer cure. This report deals with biosynthesis of silver nanoparticles (MZLAgNPs) employing leaf extracts of Manilkara zapota (L.) under optimized conditions. Characterization of MZLAgNPs using UV-Vis spectroscopy, FTIR, XRD, and FESEM analyses revealed that the particles were predominantly spherical averaging 24 nm in size. Their cellular effects were assessed by MTT assay, fluorescence, and scanning electron microscopy of cells stained with propidium iodide, acridine orange/ethidium bromide, and annexin V-FITC to visualize signs of apoptosis. Evaluation of cell proliferation by clonogenic assay, wound healing ability by scratch assay and cell cycle distribution by flow-cytometry was also carried out. Apoptosis-related gene expressions were analyzed by RTq-PCR and western blot analysis. MZLAgNPs selectively inhibited growth of colorectal carcinoma HCT116, HeLa, and non-small lung carcinoma A549 cells, dose-dependently with IC₅₀ concentrations of 8, 16, and 29 μg/mL respectively, following 72-h treatment, without affecting growth of normal human lymphocytes and erythrocytes. Apoptosis induction was observed by fluorescence and scanning electron microscopy. Overproduction of reactive oxygen species (ROS), reduction of mitochondrial membrane potential, upregulation of apoptotic-related genes - PUMA, cas-3, cas-8, cas-9, and BAX, expression of caspase 3, and occurrence of PARP cleavage were observed in MZLAgNPs/cisplatin treated cells. Taken together, our results clearly demonstrate the therapeutic potential of biogenic MZLAgNPs as an effective agent for killing colorectal carcinoma cells by apoptosis induction.

The Effects of Gene × Environment Interactions on Silver Nanoparticle Toxicity in the Respiratory System

Silver nanoparticles (AgNP) are used in multiple applications but primarily in the manufacturing of antimicrobial products. AgNP toxicity in the respiratory system is well characterized, but few in vitro or in vivo studies have evaluated the effects of interactions between host genetic and acquired factors or gene × environment interactions (G × E) on AgNP toxicity in the respiratory system. The primary goal of this article is to review host genetic and acquired factors identified across in vitro and in vivo studies and prioritize those necessary for defining exposure limits to protect all populations. The impact of these exposures and the work being done to address the current limited protections are also discussed. Future research on G × E effects on AgNP toxicity is warranted and will assist with informing regulatory or recommended exposure limits that enforce special protections for all populations to AgNP exposures in occupational settings.

Th2 cytokine bias induced by silver nanoparticles in peripheral blood mononuclear cells of common bottlenose dolphins (Tursiops truncatus)

BACKGROUND

Silver nanoparticles (AgNPs) have been widely used in many commercial products due to their excellent antibacterial ability. The AgNPs are released into the environment, gradually accumulate in the ocean, and may affect animals at high trophic levels, such as cetaceans and humans, via the food chain. Hence, the negative health impacts caused by AgNPs in cetaceans are of concern. Cytokines play a major role in the modulation of immune system and can be classified into two types: Th1 and Th2. Th1/Th2 balance can be evaluated by the ratios of their polarizing cytokines (i.e., interferon [IFN]-γ/Interleukin [IL]-4), and animals with imbalanced Th1/Th2 response may become more susceptible to certain kinds of infection. Therefore, the present study evaluated the in vitro cytokine responses of cetacean peripheral blood mononuclear cells (cPBMCs) to 20 nm citrate-AgNPs (C-AgNP20) by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR).

METHODS

Blood samples were collected from six captive common bottlenose dolphins (Tursiops truncatus). The cPBMCs were isolated and utilized for evaluating the in vitro cytokine responses. The cytokines evaluated included IL-2, IL-4, IL-10, IL-12, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α. The geometric means of two housekeeping genes (HKGs), glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and β2-microglobulin (B2M), of each sample were determined and used to normalize the mRNA expression levels of target genes.

RESULTS

The ratio of late apoptotic/necrotic cells of cPBMCs significantly increased with or without concanavalin A (ConA) stimulation after 24 h of 10 µg/ml C-AgNP20 treatment. At 4 h of culture, the mRNA expression level of IL-10 was significantly decreased with 1 µg/ml C-AgNP20 treatment. At 24 h of culture with 1 µg/ml C-AgNP20, the mRNA expression levels of all cytokines were significantly decreased, with the exceptions of IL-4 and IL-10. The IFN-γ/IL-4 ratio was significantly decreased at 24 h of culture with 1 µg/ml C-AgNP20 treatment, and the IL-12/IL-4 ratio was significantly decreased at 4 or 24 h of culture with 0.1 or 1 µg/ml C-AgNP20 treatment, respectively. Furthermore, the mRNA expression level of TNF-α was significantly decreased by 1 µg/ml C-AgNP20 after 24 h of culture.

DISCUSSION

The present study demonstrated that the sublethal dose of C-AgNP20 (≤1 µg/ml) had an inhibitory effect on the cytokine mRNA expression levels of cPBMCs with the evidence of Th2 cytokine bias and significantly decreased the mRNA expression level of TNF-α. Th2 cytokine bias is associated with enhanced immunity against parasites but decreased immunity to intracellular microorganisms. TNF-α is a contributing factor for the inflammatory response against the infection of intracellular pathogens. In summary, our data indicate that C-AgNP20 suppresses the cellular immune response and thereby increases the susceptibility of cetaceans to infection by intracellular microorganisms.

Silver nanoparticles promote the emergence of heterogeneic human neutrophil sub-populations

Neutrophil surveillance is central to nanoparticle clearance. Silver nanoparticles (AgNP) have numerous uses, however conflicting evidence exists as to their impact on neutrophils and whether they trigger damaging inflammation. Neutrophil’s importance in innate defence and regulating immune networks mean it’s essential we understand AgNP’s impact on neutrophil function. Human neutrophil viability following AgNP or Ag Bulk treatment was analysed by flow cytometry and AnV/PI staining. Whilst AgNP exposure did not increase the total number of apoptotic neutrophils, the number of late apoptotic neutrophils was increased, suggesting AgNP increase transit through apoptosis. Mature (CD16^bright/CD62L^bright), immature (CD16^dim/CD62L^bright) and apoptotic (CD16^dim/CD62L^dim) neutrophil populations were evident within isolated neutrophil preparations. AgNP exposure significantly reduced CD62L staining of CD16^bright/CD62L^bright neutrophils, and increased CD16 staining of CD16^dim/CD62L^bright populations, suggesting AgNPs trigger neutrophil activation and maturation, respectively. AgNP exposure dramatically increased IL-8, yet not classical pro-inflammatory cytokine release, suggesting AgNP triggers neutrophil activation, without pro-inflammation or damaging, necrotic cell death. For the first time, we show AgNPs differentially affect distinct sub-populations of circulating human neutrophils; activating mature neutrophils with the emergence of CD16^bright/CD62L^dim neutrophils. This may stimulate particle clearance without harmful inflammation, challenging previous assumptions that silver nanomaterials induce neutrophil toxicity and damaging inflammatory responses.

Comparative cytotoxicity and apoptotic pathways induced by nanosilver in human liver HepG2 and L02 cells

Silver nanoparticles are used in many commercial products in daily life. Exposure to nanosilver has hepatotoxic effects in animals. This study investigated the cytotoxicity associated with polyvinylpyrrolidone-coated nanosilver (23.44 ± 4.92 nm in diameter) exposure in the human hepatoma cell line (HepG2) and normal hepatic cell line (L02), and the molecular mechanisms induced by nanosilver in HepG2 cells. Nanosilver, in doses of 20-160 μg mL^-1 for 24 and 48 h, reduced cell viability in a dose- and time-dependent manner and induced cell membrane leakage and mitochondria injury in both cell lines; these effects were more pronounced in HepG2 cells than in L02 cells. Intracellular oxidative stress was documented by reactive oxygen species (ROS) being generated in HepG2 cells but not in L02 cells, an effect possibly due to differential uptake of nanosilver by cancer cells and normal cells. In HepG2 cells, apoptosis was documented by finding that ROS triggered a decrease in mitochondrial membrane potential, an increase in cytochrome c release, activation of caspase 3 and caspase 9, and a decrease in the ratio of Bcl-2/Bax. Furthermore, nanosilver activated the Fas death receptor pathway by downregulation of nuclear factor-κB and activation of caspase 8 and caspase 3. These results suggest that apoptosis induced by nanosilver in HepG2 cells is mediated via a mitochondria-dependent pathway and the Fas death receptor pathway. These findings provide toxicological and mechanistic information that can help in assessing the effects of nanosilver in biological systems, including the potential for anticancer activities.

Immunotoxicity of Silver Nanoparticles (AgNPs) on the Leukocytes of Common Bottlenose Dolphins (Tursiops truncatus)

Silver nanoparticles (AgNPs) have been extensively used and are considered as an emerging contaminant in the ocean. The environmental contamination of AgNPs is expected to increase greatly over time, and cetaceans, as the top ocean predators, will suffer the negative impacts of AgNPs. In the present study, we investigate the immunotoxicity of AgNPs on the leukocytes of cetaceans using several methods, including cytomorphology, cytotoxicity, and functional activity assays. The results reveal that 20 nm Citrate-AgNPs (C-AgNP₂₀) induce different cytomorphological alterations and intracellular distributions in cetacean polymorphonuclear cells (cPMNs) and peripheral blood mononuclear cells (cPBMCs). At high concentrations of C-AgNP₂₀ (10 and 50 μg/ml), the time- and dose-dependent cytotoxicity in cPMNs and cPBMCs involving apoptosis is demonstrated. C-AgNP₂₀ at sub-lethal doses (0.1 and 1 μg/ml) negatively affect the functional activities of cPMNs (phagocytosis and respiratory burst) and cPBMCs (proliferative activity). The current study presents the first evidence of the cytotoxicity and immunotoxicity of AgNPs on the leukocytes of cetaceans and improves our understanding of environmental safety concerning AgNPs. The dose-response data of AgNPs on the leukocytes of cetaceans are invaluable for evaluating the adverse health effects in cetaceans and for proposing a conservation plan for marine mammals.

Dependence of Nanoparticle Toxicity on Their Physical and Chemical Properties

Studies on the methods of nanoparticle (NP) synthesis, analysis of their characteristics, and exploration of new fields of their applications are at the forefront of modern nanotechnology. The possibility of engineering water-soluble NPs has paved the way to their use in various basic and applied biomedical researches. At present, NPs are used in diagnosis for imaging of numerous molecular markers of genetic and autoimmune diseases, malignant tumors, and many other disorders. NPs are also used for targeted delivery of drugs to tissues and organs, with controllable parameters of drug release and accumulation. In addition, there are examples of the use of NPs as active components, e.g., photosensitizers in photodynamic therapy and in hyperthermic tumor destruction through NP incorporation and heating. However, a high toxicity of NPs for living organisms is a strong limiting factor that hinders their use in vivo. Current studies on toxic effects of NPs aimed at identifying the targets and mechanisms of their harmful effects are carried out in cell culture models; studies on the patterns of NP transport, accumulation, degradation, and elimination, in animal models. This review systematizes and summarizes available data on how the mechanisms of NP toxicity for living systems are related to their physical and chemical properties.

Combining CXCR4-targeted and nontargeted nanoparticles for effective unassisted in vitro magnetic hyperthermia

The use of targeted nanoparticles for magnetic hyperthermia (MHT) increases MHT selectivity, but often at the expense of its effectiveness. Consequently, targeted MHT is typically used in combination with other treatment modalities. This work describes an implementation of a highly effective monotherapeutic in vitro MHT treatment based on two populations of magnetic particles. Cells were sequentially incubated with two populations of magnetic particles: nonfunctionalized superparamagnetic nanoparticles and anti-CXCR4-functionalized particles. After removing the excess of free particles, an alternating magnetic field (AMF) was applied to produce MHT. The induced cytotoxicity was assessed at different time-points after AMF application. Complete loss of cell viability was observed 72 h after MHT when the iron loading of the anti-CXCR4-functionalized particles was boosted by that of a nontargeted population. Additionally, induction of necrosis resulted in more efficient cell death than did induction of apoptosis. Achieving a uniquely high effectiveness in monotherapeutic MHT demonstrates the potential of this approach to achieve complete loss of viability of cancer cells while avoiding the side effects of dual-treatment strategies that use MHT only as a sensitizing therapy.

Activation of human eosinophils with palladium nanoparticles (Pd NPs): importance of the actin cytoskeleton in Pd NPs-induced cellular adhesion

Palladium (Pd) is known to be released into the environment in the fine and ultrafine (at the nanoscale) airborne particle fractions mainly from automobile catalytic converters leading to an increase human exposure to this noble metal. It was reported that Pd can induce allergic reactions in individuals exposed to it via different ways. Some studies reported an increased number of eosinophils into airways following NP exposure in vivo in rodent models of allergies and inflammation. Knowing the importance of eosinophils in allergies, asthma and other lung diseases, it is surprising to observe that the direct effect of Pd at the nanoscale in eosinophils has been poorly documented. The aim of this study was to determine how Pd NPs will affect the biology of human eosinophils. Characterization of Pd NPs by dynamic light scattering indicates the presence of some aggregates when suspended in diverse solutions used here for the different experiments. Pd NPs did not significantly induce cell necrosis and apoptosis in eosinophils (0.5-150μg/ml) as assessed by trypan blue exclusion assay, flow cytometry after staining with FITC-annexin V and propidium iodide and by morphological observations by optical microscopy. PD NPs, unlike the positive controls, did not induce reactive oxygen species (ROS) but were found to target the actin cytoskeleton, since actin was differently re-located intracellularly when compared to untreated cells as determined by fluorescence microscopy. Clearly, Pd NPs were found to increase adhesion of eosinophils onto human endothelial EA.hy926 cells. Using cytochalasin D, a cell-permeable and potent inhibitor of actin polymerization, this ability to increase adhesion was drastically reversed. Our results indicate that Pd NPs can target the cytoskeleton and increase the adhesion of human eosinophils by an actin-dependent mechanism. These findings show that human eosinophils can be activated by Pd NPs emphasizing the importance of fully investigating how these NPs could alter the biology of human cells involved in allergies, asthma and other lung diseases as well as in various other inflammatory disorders.

WITHDRAWN: Titanium dioxide nanoparticles induce human eosinophil adhesion onto endothelial EA.hy926 cells via activation of phosphoinositide 3-kinase/Akt cell signalling pathway

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Nanoparticle impact on innate immune cell pattern-recognition receptors and inflammasomes activation

Nanotechnology-based strategies can dramatically impact the treatment, prevention and diagnosis of a wide range of diseases. Despite the unprecedented success achieved with the use of nanomaterials to address unmet biomedical needs and their particular suitability for the effective application of a personalized medicine, the clinical translation of those nanoparticulate systems has still been impaired by the limited understanding on their interaction with complex biological systems. As a result, unexpected effects due to unpredicted interactions at biomaterial and biological interfaces have been underlying the biosafety concerns raised by the use of nanomaterials. This review explores the current knowledge on how nanoparticle (NP) physicochemical and surface properties determine their interactions with innate immune cells, with particular attention on the activation of pattern-recognition receptors and inflammasome. A critical perspective will additionally address the impact of biological systems on the effect of NP on immune cell activity at the molecular level. We will discuss how the understanding of the NP-innate immune cell interactions can significantly add into the clinical translation by guiding the design of nanomedicines with particular effect on targeted cells, thus improving their clinical efficacy while minimizing undesired but predictable toxicological effects.

Cytotoxicity and genotoxicity of nanosilver in stable GADD45α promoter-driven luciferase reporter HepG2 and A549 cells

OBJECTIVES

The intense commercial application of silver nanoparticles (AgNPs) has been raising concerns about their potential adverse health effects to human. This study aimed to explore the potency of AgNPs to induce GADD45α gene, an important stress sensor, and its relationships with the cytotoxicity and genotoxicity elicited by AgNPs.

METHODS

Two established HepG2 and A549 cell lines containing the GADD45α promoter-driven luciferase reporter were treated with increasing concentrations of AgNPs for 48 hours. After the treatment, transcriptional activation of GADD45α indicated by luciferase activity, cell viability, cell cycle arrest, and levels of genotoxicity were determined. The uptake and intracellular localization of AgNPs, cellular Ag doses as well as Ag⁺ release were also detected.

RESULTS

AgNPs could activate GADD45α gene at the transcriptional level as demonstrated by the dose-dependent increases in luciferase activity in both the reporter cells. The relative luciferase activity was greater than 12× the control level in HepG2-luciferase cells at the highest concentration tested where the cell viability decreased to 17.0% of the control. These results was generally in accordance with the positive responses in cytotoxicity, cell cycle arrest of Sub G1 and G2/M phase, Olive tail moment, micronuclei frequency, and the cellular Ag content.

CONCLUSIONS

The cytotoxicity and genotoxicity of AgNPs seems to occur mainly via particles uptake and the subsequent liberation of ions inside the cells. And furthermore, the GADD45α promoter-driven luciferase reporter cells, especially the HepG2-luciferase cells, could provide a new and valuable tool for predicting nanomaterials genotoxicity in humans.

Evaluation of the in vitro and in vivo proinflammatory activities of gold (+) and gold (-) nanoparticles

OBJECTIVE AND DESIGN

The aim of this study was to determine potential effects of gold (+) and gold (-) nanoparticles, AuNP(+) and AuNP(-), on neutrophil biology.

MATERIAL OR SUBJECTS

Freshly isolated human neutrophils were used for the in vitro aspects and CD-1 mice were used in the in vivo murine air pouch model of acute neutrophilic inflammation.

TREATMENT

Human neutrophils were treated with the indicated concentrations of AuNP(+) or AuNP(-) in vitro and mice received 100 or 500 µg/ml AuNP(+) or AuNP(-) into air pouches.

METHODS

Cellular uptake of AuNP by neutrophils was confirmed by transmission electron microscopy and the ability of the NP to modulate apoptosis, gelatinase activity, and chemokine production and chemotaxis was determined by cytology, zymography, ELISArray, antibody array, and ELISA and by a micro-chemotaxis chamber, respectively. In vivo, exudates were harvested after 6 h to determine the leukocyte infiltration to detect the production of several cytokines by an antibody array approach and ELISA. One-way analysis of variance was used for statistical analysis.

RESULTS

AuNP possess proinflammatory activities in vitro and induce mainly a neutrophil influx in vivo, albeit at different degrees.

CONCLUSIONS

AuNP(+) and AuNP(-) should be added as new candidates into a growing list of NP having proinflammatory activities by themselves.

Mechanistic understanding of nanoparticles' interactions with extracellular matrix: the cell and immune system

Extracellular matrix (ECM) is an extraordinarily complex and unique meshwork composed of structural proteins and glycosaminoglycans. The ECM provides essential physical scaffolding for the cellular constituents, as well as contributes to crucial biochemical signaling. Importantly, ECM is an indispensable part of all biological barriers and substantially modulates the interchange of the nanotechnology products through these barriers. The interactions of the ECM with nanoparticles (NPs) depend on the morphological characteristics of intercellular matrix and on the physical characteristics of the NPs and may be either deleterious or beneficial. Importantly, an altered expression of ECM molecules ultimately affects all biological processes including inflammation. This review critically discusses the specific behavior of NPs that are within the ECM domain, and passing through the biological barriers. Furthermore, regenerative and toxicological aspects of nanomaterials are debated in terms of the immune cells-NPs interactions.

Activation of human AML14.3D10 eosinophils by nanoparticles: Modulatory activity on apoptosis and cytokine production

Eosinophilic inflammation is frequently observed in response to nanoparticle (NP) exposure in airway rodent models of allergies where the number of eosinophils is increased in lungs. Despite this, it is surprising that the potential cytotoxic effect of NP, as well as their direct role on eosinophils is poorly documented. The present study investigated how different NP can alter the biology of the human eosinophilic cell line AML14.3D10. It was found that among NP forms of CeO2, ZnO, TiO2, and nanosilver of 20 nm (AgNP20) or 70 nm (AgNP70) diameters, only ZnO and AgNP20 induced apoptosis. Caspases-7 and -9 were not activated by the tested NP while caspase-3 was activated by AgNP20 only. However, both ZnO and AgNP20 induced cytoskeletal breakdown as evidenced by the cleavage of lamin B1. Using an ELISArray approach for the simultaneous detection of several analytes (cytokines/chemokines), it was found that only ZnO and AgNP20 increased the production of different analytes including the potent pro-inflammatory CXCL8 (IL-8) chemokine. From the data here, we conclude that toxic effects of some NP could be observed in human eosinophil-like cells and that this could be related, at least partially, by induction of apoptosis and production of cytokines and chemokines involved in inflammation. The results of this study also indicate that distinct NP do not activate similarly human eosinophils, since ZnO and AgNP20 induce apoptosis and cytokine production while others such as TiO2, CeO2, and AgNP70 do not.

Human eosinophils are direct targets to nanoparticles: Zinc oxide nanoparticles (ZnO) delay apoptosis and increase the production of the pro-inflammatory cytokines IL-1β and IL-8

Zinc oxide NPs (ZnO) have been recently proposed as novel candidates for the treatment of allergic inflammatory diseases. Paradoxically, recent data suggested that ZnO could cause eosinophilic airway inflammation in rodents. Despite the above observations, there are currently no studies reporting direct interaction between a given NP and human eosinophils themselves. In this study, freshly isolated human eosinophils were incubated with ZnO and several cellular functions were studied. We found that ZnO delay human eosinophil apoptosis, partially by inhibiting caspases and by preventing caspase-4 and Bcl-xL degradation. ZnO do not induce production of reactive oxygen species but increase de novo protein synthesis. In addition, ZnO were found to increase the production of the proinflammatory IL-1β and IL-8 cytokines. Using a pharmacological approach, we demonstrated that inhibition of caspase-1 reversed the ability of ZnO to induce IL-1β and IL-8 production, whereas inhibition of caspase-4 only reversed that of IL-8. Our results indicate the necessity of conducting studies to determine the potential of using NP as nanotherapies, particularly in diseases in which eosinophils may be involved. We conclude that, indeed, human eosinophils represent potential new direct targets to NPs, ZnO in the present case.

Peptides conjugated to silver nanoparticles in biomedicine – a “value-added” phenomenon

This review presents a glimpse of the various aspects of nanoparticles, in particular silver nanoparticles and their conjugation to peptides, thus opening an avenue for new discoveries in nanomaterials.

Size-dependent cytotoxicity of silver nanoparticles in human neutrophils assessed by multiple analytical approaches

AIMS

Silver nanoparticles (AgNPs) have emerged as an important class of nanomaterials with a wide range of industrial and medical applications. The assessment of AgNPs' biological effects in the human organism is therefore essential to evaluate the impact of these nanomaterials in public health and reassure the ratio benefit/risk. In the present study, the effect of polyvinyl pyrrolidone (PVP)-coated AgNPs with distinct sizes (10 and 50nm) on neutrophils' oxidative burst and toxicity were tested.

MAIN METHODS

The effect of AgNPs on human neutrophils viability was evaluated by trypan blue, neutral red and propidium iodide methods. The measurement of neutrophils' oxidative burst was performed using the probe dihydrorhodamine 123. The cytomorphological alterations of human neutrophils exposed to AgNPs were evaluated by optical microscopy and transmission electron microscopy.

KEY FINDINGS

It was observed that PVP-coated AgNPs are toxic to human neutrophils being the 10nm AgNPs more toxic than the 50nm AgNPs. The smallest AgNPs lead to membrane damage, impaired lysosomal activity and induce neutrophils' oxidative burst. Despite the production of reactive species, the toxicity of AgNPs is not NADPH oxidase-dependent.

SIGNIFICANCE

These data indicate that AgNPs are toxic to human neutrophils in concentration-, time- and size-dependent manner, but independent of NADPH oxidase activation.

Silver nanoparticles of 70 nm and 20 nm affect differently the biology of human neutrophils

The influence of size of nanoparticles (NP), especially in regard to pulmonary toxicity, has been widely investigated. In general, NP with smaller diameters are more pro-inflammatory in vivo, at least in terms of neutrophil influx. Nevertheless, the influence of size of NP on polymorphonuclear neutrophil (PMN) cell biology is poorly documented. In the study here, it was decided to determine if AgNP with a diameter of 70 nm (AgNP70) will alter the biology of human PMN similarly to AgNP20 previously reported to induce apoptosis and inhibit de novo protein synthesis. The results here indicated that, in contrast to AgNP20, AgNP70 delayed PMN apoptosis. However, both AgNP20 and AgNP70 inhibited de novo protein synthesis. Both forms of AgNP did not significantly increase reactive oxygen species (ROS) production, but AgNP20 significantly increased the cell production of the CXCL8 chemokine (IL-8). In addition, AgNP20, but not AgNP70, induced the release of albumin and matrix metalloproteinase-9 (MMP-9/gelatinase B) into culture supernatants. Consistent with this latter observation, gelatinase activity was increased by AgNP20, as assessed by zymography. From these outcomes, it is concluded that two NP with different initial diameters can possess similar - as well as distinct - biological properties in modulating human PMN functions. These outcomes are testimony to the complexity of the modes of action of NP at the cellular level.

Phytofabrication of bioinduced silver nanoparticles for biomedical applications

Synthesis of nanomaterials holds infinite possibilities as nanotechnology is revolutionizing the field of medicine by its myriad applications. Green synthesis of nanoparticles has become the need of the hour because of its eco-friendly, nontoxic, and economic nature. In this study, leaf extract of Rosa damascena was used as a bioreductant to reduce silver nitrate, leading to synthesis of silver nanoparticles (AgNPs) in a single step, without the use of any additional reducing or capping agents. The synthesized nanoparticles were characterized by the use of UV-visible spectroscopy, fourier transform infrared spectroscopy, dynamic light scattering, transmission electron microscopy, and field emission scanning electron microscopy. Time-dependent synthesis of AgNPs was studied spectrophotometrically. Synthesized AgNPs were found to possess flower-like spherical structure where individual nanoparticles were of 16 nm in diameter, whereas the agglomerated AgNPs were in the range of 60–80 nm. These biologically synthesized AgNPs exhibited significant antibacterial activity against Gram-negative bacterial species but not against Gram-positive ones (Escherichia coli and Bacillus cereus). Anti-inflammatory and analgesic activities were studied on a Wistar rat model to gauge the impact of AgNPs for a probable role in these applications. AgNPs tested positive for both these activities, although the potency was less as compared to the standard drugs.

Antibacterial Plasma Polymer Films Conjugated with Phospholipid Encapsulated Silver Nanoparticles

Medical device associated infections are a persistent medical problem which has not found a comprehensive solution yet. Over the last decades, there have been intense research efforts toward developing antibacterial coatings that could potentially improve medical outcomes. Silver nanoparticles have attracted a great deal of attention as a potent alternative to conventional antibiotics. Herein, we present a biologically inspired approach to synthesize phospholipid encapsulated silver nanoparticles and their surface immobilization to a functional plasma polymer interlayer to generate antibacterial coatings. The antibacterial efficacy of the coatings was evaluated against three medically relevant pathogens including the Gram-positive Staphylococcus aureus and Staphylococcus epidermidis, and the Gram-negative Pseudomonas aeruginosa. The innate immune response to the coatings was assessed in vitro using primary bone marrow derived macrophages (BMDM). Any potential cytotoxicity was studied with primary human dermal fibroblasts (HDFs). Overall, the coatings had excellent inhibition of bacterial growth. We also observed reduced expression of pro-inflammatory cytokines from BMDM which suggests a reduced inflammatory response. The combined properties of coatings developed in this study may make them a good candidate for application on medical devices such as catheters and wound dressings.

Silver nanoparticles rapidly induce atypical human neutrophil cell death by a process involving inflammatory caspases and reactive oxygen species and induce neutrophil extracellular traps release upon cell adhesion

Inflammation is one of the major toxic effects reported in response to in vitro or in vivo nanoparticle (NP) exposure. Among engineered NPs, silver nanoparticles (AgNPs) are very attractive for the development of therapeutic strategies, especially because of their antimicrobial properties. In humans, neutrophils, key players in inflammation, are the most abundant blood leukocytes that spontaneously undergo apoptosis, a central cell death mechanism regulating inflammation. The aim of this study was to evaluate the effect of AgNPs on neutrophil apoptosis. Transmission electronic microscopy reveals that AgNPs rapidly penetrate inside neutrophils. AgNPs induced atypical cell death where the cell volume increased and the cell surface expression of CD16 remained unaltered unlike apoptotic neutrophils where cell shrinkage and loss of CD16 are typically observed. The AgNP-induced atypical cell death is distinct from necrosis and reversed by a pancaspase inhibitor or by inhibitors of the inflammatory caspase-1 and caspase-4. In addition, AgNPs induced IL-1β production inhibited by caspase-1 and caspase-4 inhibitors and also induced caspase-1 activity. Reactive oxygen species (ROS) production was increased by AgNPs and the atypical cell death was inhibited by the antioxidant n-acetylcysteine. Under similar experimental conditions, adhesion of neutrophils leads to neutrophil extracellular trap (NET) release induced by AgNPs. However, this process was not reversed by caspase inhibitors. We conclude that AgNPs rapidly induced an atypical cell death in neutrophils by a mechanism involving caspase-1, -4 and ROS. However, in adherent neutrophils, AgNPs induced NET release and, therefore, are novel agents able to trigger NET release.

Cytotoxicity and apoptosis induced by silver nanoparticles in human liver HepG2 cells in different dispersion media

Silver nanoparticles (Ag NPs) have been widely used in medical and healthcare products owing to their unique antibacterial activities. However, their safety for humans and the environment has not yet been established. This study evaluated the cellular proliferation and apoptosis of Ag NPs suspended in different solvents using human liver HepG2 cells. The ionization of Ag NPs in different dispersion media [deionized water, phosphate-buffered saline (PBS), saline and cell culture] was measured using an Ag ion selective electrode. The MTT assay was used to examine the cell proliferation activities. The effects of Ag NPs on cell cycle, induction of apoptosis, production of reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were analyzed using flow cytometry. The degree of Ag NPs ionization differed with dispersion media, with the concentrations of silver ions in deionized water being the highest in all suspensions. Ag NPs could inhibit the viability of HepG2 cells in a time- and concentration-dependent manner. Ag NPs (40, 80 and 160 µg ml(-1)) exposure could cause cell-cycle arrest in the G2/M phase, significantly increasing the apoptosis rate and ROS generation, and decreasing the MMP in HepG2 cells more sensitive to deionized water than in cell culture. These results suggested that the cellular toxicological mechanism of Ag NPs might be related to the oxidative stress of cells by the generation of ROS, leading to mitochondria injury and induction of apoptosis. It also implies that it is important to assess the physicochemical properties of NPs in the media where the biological toxicity tests are performed.

Silver nanoparticles induce degradation of the endoplasmic reticulum stress sensor activating transcription factor-6 leading to activation of the NLRP-3 inflammasome

In the past decade, the increasing amount of nanoparticles (NP) and nanomaterials used in multiple applications led the scientific community to investigate the potential toxicity of NP. Many studies highlighted the cytotoxic effects of various NP, including titanium dioxide, zinc oxide, and silver nanoparticles (AgNP). In a few studies, endoplasmic reticulum (ER) stress was found to be associated with NP cytotoxicity leading to apoptosis in different cell types. In this study, we report for the first time that silver nanoparticles of 15 nm (AgNP15), depending on the concentration, induced different signature ER stress markers in human THP-1 monocytes leading to a rapid ER stress response with degradation of the ATF-6 sensor. Also, AgNP15 induced pyroptosis and activation of the NLRP-3 inflammasome as demonstrated by the processing and increased activity of caspase-1 and secretion of IL-1β and ASC (apoptosis-associated speck-like protein containing a CARD domain) pyroptosome formation. Transfection of THP-1 cells with siRNA targeting NLRP-3 decreased the AgNP15-induced IL-1β production. The absence of caspase-4 expression resulted in a significant reduction of pro-IL-1β. However, caspase-1 activity was significantly higher in caspase-4-deficient cells when compared with WT cells. Inhibition of AgNP15-induced ATF-6 degradation with Site-2 protease inhibitors completely blocked the effect of AgNP15 on pyroptosis and secretion of IL-1β, indicating that ATF-6 is crucial for the induction of this type of cell death. We conclude that AgNP15 induce degradation of the ER stress sensor ATF-6, leading to activation of the NLRP-3 inflammasome regulated by caspase-4 in human monocytes.

Nanoparticle–blood interactions: the implications on solid tumour targeting

This review examines nanoparticle–blood interactions, their implications on solid tumour targeting, and provides an outlook to guide future nanoparticle design.