Amorphous silica nanoparticles size-dependently aggravate atopic dermatitis-like skin lesions following an intradermal injection

High inflammatory cytokines gene expression can be detected in workers with prolonged exposure to silver and silica nanoparticles in industries

Occupational health must be strictly considered in industries particularly in nanoparticle factories where workers were exposed to different types of chemicals. We measured the serum levels of inflammatory cytokines in workers who developed skin lesions after exposure to silver and silica nanoparticles. Using a questionnaire in this cross-sectional study, we identified 110 workers in nanoparticle industries who were exposed to silver and silica nanoparticles. We also included 40 healthy subjects as controls from the administrative department of the same factories who were not exposed to nanoparticles. Peripheral blood samples used to measure the mRNA levels of inflammatory cytokines by qRT-PCR. In comparison with the control group, the workers who developed skin lesions had significantly higher levels of interleukin IL4, IL6, IL8, and TNF-α, particularly after two or three decades of exposure to silver and silica nanoparticles. Participants who were exposed to silver had higher levels of IL6 and IL8 compared with those who were exposed to silica. Necessary measures must be considered to protect workers in nanoparticle industries against the potential toxic effects of these compounds. Our network pharmacology study suggests corresponding biochemical pathways for these disorders.

The size-dependent in vivo toxicity of amorphous silica nanoparticles: A systematic review

The extensive application of amorphous silica nanoparticles (aSiNPs) in recent years has resulted in unavoidable human exposure in daily life, thus raising widespread concerns regarding the safety of aSiNPs on human health. The particle size is one of the important characteristics of nanomaterials that could influence their toxicity. For the reason that particles with smaller sizes possess larger surface area, which may lead to higher surface activity and biological reactivity. However, due to the complexity of experimental conditions and biological systems, the relationship between the particle size and the toxic effect of aSiNPs remains unclear. Therefore, this systematic review aims to investigate how particle size influences the toxic effect of aSiNPs in vivo and to analyze the relevant experimental factors affecting the size-dependent toxicity of aSiNPs in vivo. We found that 83.8% of 35 papers included in the present review came to the conclusion that smaller-sized aSiNPs exhibited stronger toxicity, though a few papers (6 papers) put forward different opinions. The reasons for smaller aSiNPs manifested greater toxicity were summarized. In addition, certain important experimental factors could influence the size-dependent effects and in vivo toxicity of aSiNPs, such as the synthesis method of aSiNPs, disperse medium of aSiNPs, administration route of aSiNPs, species or strain of experimental animals, sex of experimental animals, aggregation/agglomeration and protein corona of aSiNPs.

Emerging nanotechnology backed formulations for the management of atopic dermatitis

Atopic dermatitis is a prevalent chronic skin inflammation affecting 2.1 to 4.1% of adults globally. The complexity of its pathogenesis and the relapsing nature make it challenging to treat. Current treatments follow European Academy of Dermatology and Venerology guidelines, but advanced cases with recurring lesions lack effective therapies. To address this gap, researchers are exploring nanotechnology for targeted drug delivery. Nanoparticles offer benefits such as improved drug retention, stability, controlled release and targeted delivery through the disrupted epidermal barrier. This integrated review evaluates the current state of AD treatment and highlights the potential of novel nano-formulations as a promising approach to address the disease.

Mechanistic insights into silica nanoparticle-allergen interactions on antigen presenting cell function in the context of allergic reactions

The incorporation of nanomaterials into consumer products has substantially increased in recent years, raising concerns about their safety. The inherent physicochemical properties of nanoparticles allow them to cross epithelial barriers and gain access to immunocompetent cells. Nanoparticles in cosmetic products can potentially interact with environmental allergens, forming a protein corona, and together penetrate through damaged skin. Allergen-nanoparticle interactions may influence the immune response, eventually resulting in an adverse or beneficial outcome in terms of allergic reactivity. This study determines the impact of silica nanoparticle-allergen interactions on allergic sensitization by studying the major molecular mechanisms affecting allergic responses. The major birch pollen allergen Bet v 1 was chosen as a model allergen and the birch pollen extract as a comparator. Key events in immunotoxicity including allergen uptake, processing, presentation, expression of costimulatory molecules and cytokine release were studied in human monocyte-derived dendritic cells. Using an in vivo sensitization model, murine Bet v 1-specific IgG and IgE levels were monitored. Upon the interaction of allergens with silica nanoparticles, we observed an enhanced uptake of the allergen by macropinocytosis, improved proteolytic processing, and presentation concomitant with a propensity to increase allergen-specific IgG2a and decrease IgE antibody levels. Together, these events suggest that upon nanoparticle interactions the immune response is biased towards a type 1 inflammatory profile, characterized by the upregulation of T helper 1 (Th1) cells. In conclusion, the interaction of the birch pollen allergen with silica nanoparticles will not worsen allergic sensitization, a state of type 2-inflammation, but rather seems to decrease it by skewing towards a Th1-dominated immune response.

Recent Trends in Nanocarriers for the Management of Atopic Dermatitis

BACKGROUND

Atopic dermatitis (AD) is a pruritic inflammatory skin condition with increasing global prevalence, almost affecting 15% to 30% of children and 5% of adults. AD results due to a complex interaction between the impaired skin barrier function, allergens, and immunological cells. Topical corticosteroids or calcineurin inhibitors in the form of creams or ointments are the mainstay of therapy, but they have low skin penetration and skin barrier repair efficiency.

OBJECTIVE

The above limitations of conventional dosage forms have motivated the development of nanoformulations of drugs for improved penetration and deposition in the skin for better management of AD.

METHODS

Databases, such as Pubmed, Elsevier, and Google Scholar, were reviewed for the investigations or reviews published related to the title.

RESULTS

The present review discusses the advantages of nanoformulations for the management of AD. Further, it also discusses the various types of topically investigated nanoformulations, i.e., polymeric nanoparticles, inorganic nanoparticles, solid lipid nanoparticles, liposomes, ethosomes, transfersomes, cubosomes, and nanoemulsion for the management of atopic dermatitis. In addition, it also discusses advancements in nanoformulations, such as nanofibres, nanosponges, micelles, and nanoformulations embedded textiles development for the management of AD.

CONCLUSION

The nanoformulations of drugs can be a better alternative for the topical management of AD with enhanced skin penetration and deposition of drugs with reduced systemic side effects and better patient compliance.

Nanoparticles for Topical Application in the Treatment of Skin Dysfunctions-An Overview of Dermo-Cosmetic and Dermatological Products

Nanomaterials (NM) arouse interest in various fields of science and industry due to their composition-tunable properties and the ease of modification. They appear currently as components of many consumer products such as sunscreen, dressings, sports clothes, surface-cleaning agents, computer devices, paints, as well as pharmaceutical and cosmetics formulations. The use of NPs in products for topical applications improves the permeation/penetration of the bioactive compounds into deeper layers of the skin, providing a depot effect with sustained drug release and specific cellular and subcellular targeting. Nanocarriers provide advances in dermatology and systemic treatments. Examples are a non-invasive method of vaccination, advanced diagnostic techniques, and transdermal drug delivery. The mechanism of action of NPs, efficiency of skin penetration, and potential threat to human health are still open and not fully explained. This review gives a brief outline of the latest nanotechnology achievements in products used in topical applications to prevent and treat skin diseases. We highlighted aspects such as the penetration of NPs through the skin (influence of physical-chemical properties of NPs, the experimental models for skin penetration, methods applied to improve the penetration of NPs through the skin, and methods applied to investigate the skin penetration by NPs). The review summarizes various therapies using NPs to diagnose and treat skin diseases (melanoma, acne, alopecia, vitiligo, psoriasis) and anti-aging and UV-protectant nano-cosmetics.

Greater Plasma Protein Adsorption on Mesoporous Silica Nanoparticles Aggravates Atopic Dermatitis

Purpose

The protein corona surrounding nanoparticles has attracted considerable attention as it induces subsequent inflammatory responses. Although mesoporous silica nanoparticles (MSN) are commonly used in medicines, cosmetics, and packaging, the inflammatory effects of the MSN protein corona on the cutaneous system have not been investigated till date.

Methods

We examined the greater plasma protein adsorption on MSN leads to serious inflammatory reactions in Dermatophagoides farinae extract (DFE)-induced mouse atopic dermatitis (AD)-like skin inflammation because of increased uptake by keratinocytes.

Results

We compare the AD lesions induced by MSN and colloidal (non-porous) silica nanoparticles (CSN), which exhibit different pore architectures but similar dimensions and surface chemistry. MSN-corona treatment of severe skin inflammation in a DFE-induced in vivo AD model greatly increases mouse ear epidermal thickness and infiltration of immune cells compared with the CSN-corona treatment. Moreover, MSN-corona significantly increase AD-specific immunoglobulins, serum histamine, and Th1/Th2/Th17 cytokines in the ear and lymph nodes. MSN-corona induce more severe cutaneous inflammation than CSN by significantly decreasing claudin-1 expression.

Conclusion

This study demonstrates the novel impact of the MSN protein corona in inducing inflammatory responses through claudin-1 downregulation and suggests useful clinical guidelines for MSN application in cosmetics and drug delivery systems.

Studies on safety and efficacy of particles containing a mixture of hydroxyapatite–argentum–titanium oxide (HAT) and sheets coated with HAT particles to be used in masks to improve nasal allergy: II. Cellular, in vivo, and clinical studies

Purpose

We report the manufacture of particles containing a mixture of hydroxyapatite–argentum–titanium oxide (HAT), followed by attachment to nonwoven polyester fabrics to produce HAT-coated sheets (HATS) for use in masks. The purpose of the present study was to perform cellular, in vivo, and clinical studies to further examine the safety of HATS for use in masks to improve nasal allergy.

Methods

Reverse mutation tests for HAT were performed using five bacterial strains. A cellular toxicity test was performed using a Chinese hamster cell line incubated with the HATS extracts. Skin reactions after intradermal administration were examined in rabbits. Skin sensitization tests in guinea pigs were performed using the HATS extracts. HAT was administered to the nasal cavity and conjunctival sac of the rabbits. An oral administration study was performed in rats. Finally, a human skin patch test was performed using the HATS.

Results

Reverse mutation tests showed negative results. The cellular toxicity test showed that the HATS extract had moderate cytotoxicity. The intradermal skin reaction and skin sensitization tests were all negative. The administration of HAT to the nasal cavity and intraocular administration showed negative results. No toxicity was observed after oral administration of HAT powder up to a dose of 2000 mg/kg. Finally, the skin patch test result was negative.

Conclusion

Although HAT showed moderate cytotoxicity, in vivo results indicated that HAT is safe because it does not come in direct contact with cells in normal usage, and HATS is safe when used in masks.

Skin interaction, permeation, and toxicity of silica nanoparticles: Challenges and recent therapeutic and cosmetic advances

Silica nanoparticles (SNPs) received more attention with the emergence of nanotechnology with the aim and promise of becoming innovative drug delivery systems. They have been fulfilling this objective with excellence and nowadays they play a central role in biomedical applications. New SNPs application routes are being explored such as the epidermal, dermal, and transdermal routes. With that, novel models of synthesis, functionalization, and applications constantly appear. However, it is essential that such innovations are accompanied by in-depth studies on permeation, biodistribution, metabolization, and elimination of the generated by-products. Such studies are still incipient, if not rare. This article reviews significant findings on SNPs and their skin interactions. An extensive literature review on SNPs synthesis and functionalization methodologies was performed, as well as on the skin characteristics, skin permeation mechanisms, and in vivo toxicity assessments. Furthermore, studies of the past 5 years on the main therapeutic and cosmetic products employing SNPs, with greater emphasis on in vivo and ex vivo studies were included.

Immunotoxicity of nanomaterials in health and disease: Current challenges and emerging approaches for identifying immune modifiers in susceptible populations

Nanosafety assessment has experienced an intense era of research during the past decades driven by a vivid interest of regulators, industry, and society. Toxicological assays based on in vitro cellular models have undergone an evolution from experimentation using nanoparticulate systems on singular epithelial cell models to employing advanced complex models more realistically mimicking the respective body barriers for analyzing their capacity to alter the immune state of exposed individuals. During this phase, a number of lessons were learned. We have thus arrived at a state where the next chapters have to be opened, pursuing the following objectives: (1) to elucidate underlying mechanisms, (2) to address effects on vulnerable groups, (3) to test material mixtures, and (4) to use realistic doses on (5) sophisticated models. Moreover, data reproducibility has become a significant demand. In this context, we studied the emerging concept of adverse outcome pathways (AOPs) from the perspective of immune activation and modulation resulting in pro-inflammatory versus tolerogenic responses. When considering the interaction of nanomaterials with biological systems, protein corona formation represents the relevant molecular initiating event (e.g., by potential alterations of nanomaterial-adsorbed proteins). Using this as an example, we illustrate how integrated experimental-computational workflows combining in vitro assays with in silico models aid in data enrichment and upon comprehensive ontology-annotated (meta)data upload to online repositories assure FAIRness (Findability, Accessibility, Interoperability, Reusability). Such digital twinning may, in future, assist in early-stage decision-making during therapeutic development, and hence, promote safe-by-design innovation in nanomedicine. Moreover, it may, in combination with in silico-based exposure-relevant dose-finding, serve for risk monitoring in particularly loaded areas, for example, workplaces, taking into account pre-existing health conditions. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Echinochrome A Treatment Alleviates Atopic Dermatitis-like Skin Lesions in NC/Nga Mice via IL-4 and IL-13 Suppression

Atopic dermatitis (AD) is a chronic inflammatory skin disease in which skin barrier dysfunction leads to dryness, pruritus, and erythematous lesions. AD is triggered by immune imbalance and oxidative stress. Echinochrome A (Ech A), a natural pigment isolated from sea urchins, exerts antioxidant and beneficial effects in various inflammatory disease models. In the present study, we tested whether Ech A treatment alleviated AD-like skin lesions. We examined the anti-inflammatory effect of Ech A on 2,4-dinitrochlorobenzene (DNCB)-induced AD-like lesions in an NC/Nga mouse model. AD-like skin symptoms were induced by treatment with 1% DNCB for 1 week and 0.4% DNCB for 5 weeks in NC/Nga mice. The results showed that Ech A alleviated AD clinical symptoms, such as edema, erythema, and dryness. Treatment with Ech A induced the recovery of epidermis skin lesions as observed histologically. Tewameter^® and Corneometer^® measurements indicated that Ech A treatment reduced transepidermal water loss and improved stratum corneum hydration, respectively. Ech A treatment also inhibited inflammatory-response-induced mast cell infiltration in AD-like skin lesions and suppressed the expression of proinflammatory cytokines, such as interferon-γ, interleukin-4, and interleukin-13. Collectively, these results suggest that Ech A may be beneficial for treating AD owing to its anti-inflammatory effects.

Submicron silica particles have cytotoxicities on hepatocellular carcinoma, non-small cell lung cancer and breast cancer by unified regulating the XLOC_001659/miR-98-5p/MAP3K2-mediated pathway

The cytotoxicities of silica (SiO₂s) particles against cancers are still controversial. In this study, the purchased submicron silica particles (SM-SiO₂s) were identified by transmission electron microscopy and energy dispersive spectrometer, and it showed potent cytotoxicities on hepatocellular carcinoma (HCC), non-small cell lung cancer (NSCLC) and breast cancer (BC), which ranked the top in the incidence among the tumor types. Through the microarray assay on long noncoding RNAs (lncRNAs) from the SM-SiO₂s-treated HCC, NSCLC and BC cells, followed by Venn analysis, we found that a series of lncRNAs were significantly regulated by SM-SiO₂s, among of which XLOC_001659 was mostly decreased. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay confirmed that XLOC_001659 could be decreased in all the SM-SiO₂s-treated HCC, NSCLC and BC cells, coupled to inhibited cell proliferation. Further, XLOC_001659 was recognized as a miR-98-5p sponge and therefore modulates the "pro-inflammatory tumor promoter" MAP3K2 expressions. The XLOC_001659/miR-98-5p/MAP3K2 axis uniformly mediated the regulation of SM-SiO₂s on proliferation of HCC, NSCLC and BC cells. Further clinical experiments demonstrated that XLOC_001659 was negatively correlated with miR-98-5p level and positively correlated with MAP3K2 level, and XLOC_001659/miR-98-5p/MAP3K2 axis was significantly associated with progressions and prognosis in HCC, NSCLC and BC patients. These results provide a new clue for the anti-tumor mechanism of SM-SiO₂s and a new way for drug development by using SM-SiO2s.

Surgical Wound Complications after Knee Cruciate Ligament Reconstruction in Patients with Atopic Dermatitis

Atopic dermatitis (AD), sometimes referred to as eczema, is a common skin disease, and skin barrier dysfunction and immunological disorders are well recognized. However, surgical wound complications after orthopaedic surgery in patients with AD have not been described. This study aimed to report four patients with AD who developed foreign body reactions to FiberWire sutures with or without surgical wound infection (SSI) after knee cruciate ligament reconstruction (CLR). The mean age was 19.8 (range, 16-25) years, and patients 1 and 3 underwent reconstructions of the posterior and anterior cruciate ligament, respectively. At a mean of 7.5 (range, 4-10) weeks postoperatively, discharge from the surgical wound at the tibial side of the fixed graft was identified. All patients were treated with continuous saline lavage and antibiotics; however, their wounds did not heal. Second-look arthroscopy and hardware removal were performed at a mean 12.2 (range, 9-15) months postoperatively. Proliferated granulation tissue surrounding the FiberWire was identified. Intraoperative wound cultures were negative in three of the four patients. Histological examination of the tissues adjacent to the FiberWire revealed a foreign body reaction. All wounds healed immediately after the second surgery. In addition to SSI, foreign body reactions are more likely to occur in patients with AD than in those without AD. Preoperative management of AD by dermatologists and consideration of appropriate suture materials are mandatory to reduce surgical wound complications after knee CLR in patients with AD.

Oral intake of silica nanoparticles exacerbates intestinal inflammation

Nanoparticles, i.e., particles with a diameter of ≤100 nm regardless of their composing material, are added to various foods as moisturizers, coloring agents, and preservatives. Silicon dioxide (SiO2, silica) nanoparticles in particular are widely used as food additives. However, the influence of SiO2 nanoparticle oral consumption on intestinal homeostasis remains unclear. The daily intake of 10-nm-sized SiO2 nanoparticles exacerbates dextran sulfate sodium (DSS)-induced colitis, whereas the daily intake of 30-nm-sized SiO2 nanoparticles has no influence on intestinal inflammation. The exacerbation of colitis induced by consuming 10-nm-sized SiO2 nanoparticles was abolished in mice deficient in apoptosis-associated speck-like protein containing a CARD (ASC). Our study indicates that the oral intake of small SiO2 nanoparticles poses a risk for worsening intestinal inflammation through activation of the ASC inflammasome.

Trends in nanoformulations for atopic dermatitis treatment

INTRODUCTION

Immunological skin dysfunctions trigger the synthesis and release of inflammatory cytokines, which induce recurrent skin inflammation associated with chronic itching, inefficient barrier behavior, and reduced skin hydration. These features characterize a multifactorial chronic inflammatory disease atopic dermatitis (AD). AD therapy includes anti-inflammatory drugs and immunosuppressors as well as non-pharmacological alternatives such as emollients, moisturizers, and lipids (ceramides, phospholipids) for modulating the skin hydration and the barrier repair. However, these treatments are inconvenient with low drug skin penetration and insufficient maintenance on the application site.

AREAS COVERED

Nanotechnology-based therapies can be a great strategy to overcome these limitations. Considering the particular skin morphological organization, SC lipid matrix composition, and immunological functions/features related to nanocarriers, this review focuses on recent developments of nanoparticulate systems (polymeric, lipid-based, inorganic) as parent or hybrid systems including their chemical composition, physico-chemical and biopharmaceutical properties, and differential characteristics that evaluate them as new effective drug-delivery systems for AD treatment.

EXPERT OPINION

Despite the several innovative formulations, research in nanotechnology-based carriers should address specific aspects such as the use of moisturizers associated to pharmacological therapies, toxicity studies, scale-up production processes and the nanocarrier influence on immunological response. These approaches will help researchers choose the most appropriate nanocarrier system and widen nanomedicine applications and commercialization.

Engineered Nanomaterials and Type I Allergic Hypersensitivity Reactions

Type I allergic hypersensitivity disorders (atopy) including asthma, atopic dermatitis, allergic rhinitis, and food allergy are on the rise in developed and developing countries. Engineered nanomaterials (ENMs) span a large spectrum of material compositions including carbonic, metals, polymers, lipid-based, proteins, and peptides and are being utilized in a wide range of industries including healthcare and pharmaceuticals, electronics, construction, and food industry, and yet, regulations for the use of ENMs in consumer products are largely lacking. Prior evidence has demonstrated the potential of ENMs to induce and/or aggravate type I allergic hypersensitivity responses. Furthermore, previous studies have shown that ENMs could directly interact with and activate key T-helper 2 (Th2) effector cell types (such as mast cells) and the complement system, which could result in pseudoallergic (non-IgE-mediated) hypersensitivity reactions. Nevertheless, the underlying molecular mechanisms of ENM-mediated induction and/or exacerbation of type I immune responses are poorly understood. In this review, we first highlight key examples of studies that have demonstrated inherent immunomodulatory properties of ENMs in the context of type I allergic hypersensitivity reactions, and most importantly, we attempt to put together the potential molecular mechanisms that could drive ENM-mediated stimulation and/or aggravation of type I allergic hypersensitivity responses.

Metal nanomaterials: Immune effects and implications of physicochemical properties on sensitization, elicitation, and exacerbation of allergic disease

The recent surge in incorporation of metallic and metal oxide nanomaterials into consumer products and their corresponding use in occupational settings have raised concerns over the potential for metals to induce size-specific adverse toxicological effects. Although nano-metals have been shown to induce greater lung injury and inflammation than their larger metal counterparts, their size-related effects on the immune system and allergic disease remain largely unknown. This knowledge gap is particularly concerning since metals are historically recognized as common inducers of allergic contact dermatitis, occupational asthma, and allergic adjuvancy. The investigation into the potential for adverse immune effects following exposure to metal nanomaterials is becoming an area of scientific interest since these characteristically lightweight materials are easily aerosolized and inhaled, and their small size may allow for penetration of the skin, which may promote unique size-specific immune effects with implications for allergic disease. Additionally, alterations in physicochemical properties of metals in the nano-scale greatly influence their interactions with components of biological systems, potentially leading to implications for inducing or exacerbating allergic disease. Although some research has been directed toward addressing these concerns, many aspects of metal nanomaterial-induced immune effects remain unclear. Overall, more scientific knowledge exists in regards to the potential for metal nanomaterials to exacerbate allergic disease than to their potential to induce allergic disease. Furthermore, effects of metal nanomaterial exposure on respiratory allergy have been more thoroughly-characterized than their potential influence on dermal allergy. Current knowledge regarding metal nanomaterials and their potential to induce/exacerbate dermal and respiratory allergy are summarized in this review. In addition, an examination of several remaining knowledge gaps and considerations for future studies is provided.

Surface area- and mass-based comparison of fine and ultrafine nickel oxide lung toxicity and augmentation of allergic response in an ovalbumin asthma model

Background: The correlation of physico-chemical properties with mechanisms of toxicity has been proposed as an approach to predict the toxic potential of the vast number of emerging nanomaterials. Although relationships have been established between properties and the acute pulmonary inflammation induced by nanomaterials, properties' effects on other responses, such as exacerbation of respiratory allergy, have been less frequently explored.Methods: In this study, the role of nickel oxide (NiO) physico-chemical properties in the modulation of ovalbumin (OVA) allergy was examined in a murine model. Results: 181 nm fine (NiO-F) and 42 nm ultrafine (NiO-UF) particles were characterized and incorporated into a time course study where measured markers of pulmonary injury and inflammation were associated with NiO particle surface area. In the OVA model, exposure to NiO, irrespective of any metric was associated with elevated circulating total IgE levels. Serum and lung cytokine levels were similar with respect to NiO surface area. The lower surface area was associated with an enhanced Th2 profile, whereas the higher surface area was associated with a Th1-dominant profile. Surface area-normalized groups also exhibited similar alterations in OVA-specific IgE levels and lung neutrophil number. However, lung eosinophil number and allergen challenge-induced alterations in lung function related more to particle size, wherein NiO-F was associated with an increased enhanced pause response and NiO-UF was associated with increased lung eosinophil burden.Conclusions: Collectively, these findings suggest that although NiO surface area correlates best with acute pulmonary injury and inflammation following respiratory exposure, other physico-chemical properties may contribute to the modulation of immune responses in the lung.

Conjugation of a Small-Molecule TLR7 Agonist to Silica Nanoshells Enhances Adjuvant Activity

Stimulation of Toll-like receptors (TLRs) and/or NOD-like receptors on immune cells initiates and directs immune responses that are essential for vaccine adjuvants. The small-molecule TLR7 agonist, imiquimod, has been approved by the FDA as an immune response modifier but is limited to topical application due to its poor pharmacokinetics that causes undesired adverse effects. Nanoparticles are increasingly used with innate immune stimulators to mitigate side effects and enhance adjuvant efficacy. In this study, a potent small-molecule TLR7 agonist, 2-methoxyethoxy-8-oxo-9-(4-carboxybenzyl)adenine (1V209), was conjugated to hollow silica nanoshells (NS). Proinflammatory cytokine (IL-6, IL-12) release by mouse bone-marrow-derived dendritic cells and human peripheral blood mononuclear cells revealed that the potency of silica nanoshells-TLR7 conjugates (NS-TLR) depends on nanoshell size and ligand coating density. Silica nanoshells of 100 nm diameter coated with a minimum of ∼6000 1V209 ligands/particle displayed 3-fold higher potency with no observed cytotoxicity when compared to an unconjugated TLR7 agonist. NS-TLR activated the TLR7-signaling pathway, triggered caspase activity, and stimulated IL-1β release, while neither unconjugated TLR7 ligands nor silica shells alone produced IL-1β. An in vivo murine immunization study, using the model antigen ovalbumin, demonstrated that NS-TLR increased antigen-specific IgG antibody induction by 1000× with a Th1-biased immune response, compared to unconjugated TLR7 agonists. The results show that the TLR7 ligand conjugated to silica nanoshells is capable of activating an inflammasome pathway to enhance both innate immune-stimulatory and adjuvant potencies of the TLR7 agonist, thereby broadening applications of innate immune stimulators.

Amorphous silicon dioxide nanoparticles modulate immune responses in a model of allergic contact dermatitis

Amorphous silicon dioxide nanoparticles (SiNPs) are ubiquitous, and they are currently found in cosmetics, drugs, and foods. Biomedical research is also focused on using these nanoparticles as drug delivery and bio-sensing platforms. Due to the high potential for skin exposure to SiNPs, research into the effect of topical exposure on both healthy and inflammatory skin models is warranted. While we observe only minimal effects of SiNPs on healthy mouse skin, there is an immunomodulatory effect of these NPs in a model of allergic contact dermatitis. The effect appears to be mediated partly by keratinocytes and results in decreases in epidermal hyperplasia, inflammatory cytokine release, immune cell infiltration, and a subsequent reduction in skin swelling. Additional research is required to further our mechanistic understanding and to validate the extent of this immunomodulatory effect in human subjects in order to assess the potential prophylactic use of SiNPs for treating allergic skin conditions.

EspA-loaded mesoporous silica nanoparticles can efficiently protect animal model against enterohaemorrhagic E. coli O157: H7

In the present study, the application of mesoporous silica nanoparticles (MSNPs) loaded with recombinant EspA protein, an immunogen of enterohaemorrhagic E. coli, was investigated in the case of BALB/c mice immunization against the bacterium. MSNPs of 96.9 ± 15.9 nm in diameter were synthesized using template removing method. The immunization of mice was carried out orally and subcutaneously. Significant immune responses to the antigen were observed for the immunized mice when rEspA-loaded MSNPs were administered in both routes in comparison to that of the antigen formulated using a well-known adjuvant, i.e. Freund's. According to the titretitre of serum IL-4, the most potent humoral responses were observed when the mice were immunized subcutaneously with antigen-loaded MSNPs (244, 36 and 14 ng/dL of IL-4 in the serum of mice immunized subcutaneously or orally by antigen-loaded MSNPs, and subcutaneously by Freund's adjuvant formulated-antigen, respectively). However, the difference in serum IgG and serum IgA was not significant in mice subcutaneously immunized with antigen-loaded MSNPs and mice immunized with Freund's adjuvant formulated-antigen. Finally, the immunized mice were challenged orally by enterohaemorrhagic E. coli cells. The amount of bacterial shedding was significantly reduced in faecesfaeces of the animals immunized by antigen-loaded MSNPs in both subcutaneous and oral routes.

Role of Endocrine-Disrupting Engineered Nanomaterials in the Pathogenesis of Type 2 Diabetes Mellitus

Nanotechnology has enabled the development of innovative technologies and products for several industrial sectors. Their unique physicochemical and size-dependent properties make the engineered nanomaterials (ENMs) superior for devising solutions for various research and development sectors, which are otherwise unachievable by their bulk forms. However, the remarkable advantages mediated by ENMs and their applications have also raised concerns regarding their possible toxicological impacts on human health. The actual issue stems from the absence of systematic data on ENM exposure-mediated health hazards. In this direction, a comprehensive exploration on the health-related consequences, especially with respect to endocrine disruption-related metabolic disorders, is largely lacking. The reasons for the rapid increase in diabetes and obesity in the modern world remain largely unclear, and epidemiological studies indicate that the increased presence of endocrine disrupting chemicals (EDCs) in the environment may influence the incidence of metabolic diseases. Functional similarities, such as mimicking natural hormonal actions, have been observed between the endocrine-disrupting chemicals (EDCs) and ENMs, which supports the view that different types of NMs may be capable of altering the physiological activity of the endocrine system. Disruption of the endocrine system leads to hormonal imbalance, which may influence the development and pathogenesis of metabolic disorders, particularly type 2 diabetes mellitus (T2DM). Evidence from many in vitro, in vivo and epidemiological studies, suggests that ENMs generally exert deleterious effects on the molecular/hormonal pathways and the organ systems involved in the pathogenesis of T2DM. However, the available data from several such studies are not congruent, especially because of discrepancies in study design, and therefore need to be carefully examined before drawing meaningful inferences. In this review, we discuss the outcomes of ENM exposure in correlation with the development of T2DM. In particular, the review focuses on the following sub-topics: (1) an overview of the sources of human exposure to NMs, (2) systems involved in the uptake of ENMs into human body, (3) endocrine disrupting engineered nanomaterials (EDENMs) and mechanisms underlying the pathogenesis of T2DM, (4) evidence of the role of EDENMs in the pathogenesis of T2DM from in vitro, in vivo and epidemiological studies, and (5) conclusions and perspectives.

Immune responses to engineered nanomaterials: current understanding and challenges

Engineered nanomaterials (ENM) are utilized in many applications due to their unique physicochemical properties. The increasing use of ENMs in consumer products raises concerns of potential adverse effects in humans and the environment. A common outcome of exposure (intentional, environmental or occupational) to ENMs is altered immune responses including inflammation, hypersensitivity, and immunosuppression. ENMs have been shown to interact with the immune system through key effector cells (i.e. mast cells and antigen presenting cells) or via complement activation leading to consequences to both innate and adaptive immunity. Further, upon introduction into a biological system, ENMs are rapidly coated with proteins, lipids and other macromolecules forming a biocorona which impacts immune cell and complement responses. In this current opinion, we highlight key studies and challenges in understanding cellular mechanisms of ENM-mediated immunomodulation and toxicity.

Immunomodulatory Effects of Nanoparticles on Skin Allergy

In recent years there has been considerable effort to understand the interaction of nanomaterials with the skin. In this study we use an in vivo mouse model of allergic contact dermatitis to investigate how nanoparticles (NPs) may alter allergic responses in skin. We investigate a variety of NPs that vary in size, charge and composition. Results show that small (<200 nm) negative and neutral charged NPs exhibit an immunosuppressive effect but that positively charged NPs do not. Confocal imaging suggests positively charged NPs may penetrate skin to a lesser extent and thereby are less able interact with and alter the local immune responses. Interestingly, negatively charged silica (20 nm) NPs suppress allergic response to two chemically distinct sensitizers; 1-fluoro-2, 4-dinitrobenzene and 2-deoxyurushiol. Skin wiping and NP application time studies suggest that the immunomodulatory mechanism is not due solely to the blocking of sensitizer adduct formation in skin. Results suggest that NPs modulate early immune events that impact mast cell degranulation. Our study shows for the first time the potential to modulate the elicitation phase of the allergic response which depends on the NP charge and composition. These finding can be used to inform the design topical therapeutics to mitigate allergic responses in skin.

Human Scavenger Receptor A1-Mediated Inflammatory Response to Silica Particle Exposure Is Size Specific

The application of nanotechnology in the health care setting has many potential benefits; however, our understanding of the interactions between nanoparticles and our immune system remains incomplete. Although many of the biological effects of nanoparticles are negatively correlated with particle size, some are clearly size specific and the mechanisms underlying these size-specific biological effects remain unknown. Here, we examined the pro-inflammatory effects of silica particles in THP-1 cells with respect to particle size; a large overall size range with narrow intervals between particle diameters (particle diameter: 10, 30, 50, 70, 100, 300, and 1,000 nm) was used. Secretion of the pro-inflammatory cytokines interleukin (IL)-1β and tumor necrosis factor (TNF)-α induced by exposure to the silica particles had a bell-shaped distribution, where the maximal secretion was induced by silica nanoparticles with a diameter of 50 nm and particles with smaller or larger diameters had progressively less effect. We found that blockade of IL-1β secretion markedly inhibited TNF-α secretion, suggesting that IL-1β is upstream of TNF-α in the inflammatory cascade induced by exposure to silica particles, and that the induction of IL-1β secretion was dependent on both the NLRP3 inflammasome and on uptake of the silica particles into the cells via endocytosis. However, a quantitative analysis of silica particle uptake showed that IL-1β secretion was not correlated with the amount of silica particles taken up by the cells. Further investigation revealed that the induction of IL-1β secretion and uptake of silica nanoparticles with diameters of 50 or 100 nm, but not of 10 or 1,000 nm, was dependent on scavenger receptor (SR) A1. In addition, of the silica particles examined, only those with a diameter of 50 nm induced strong IL-1β secretion via activation of Mer receptor tyrosine kinase, a signal mediator of SR A1. Together, our results suggest that the SR A1-mediated pro-inflammatory response is dependent on ligand size and that both SR A1-mediated endocytosis and receptor-mediated signaling are required to produce the maximal pro-inflammatory response to exposure to silica particles.

Nano-safety Research: Examining the Associations among the Biological Effects of Nanoparticles and Their Physicochemical Properties and Kinetics

In the past decade, nanotechnology has advanced rapidly, and many products containing nanoparticles are now an important part of our daily lives. Despite our increasing exposure to nanoparticles, however, information regarding the absorption, distribution, metabolism, excretion, and toxicity of nanoparticles remains limited. In this review, we introduce our group's ongoing research into the biological effects and toxicities of nanoparticles, which we broadly refer to as "nano-safety research." In addition to determining the biological effects of nanoparticles and elucidating the underlying mechanisms of those effects, we are also exploring the associations among the physicochemical properties and kinetics of nanoparticles. Furthermore, we are currently developing a battery of biomarkers that we hope will be used to predict the biological effects of nanoparticles during the early stages of development. Our research provides valuable basic information on the safety of nanoparticles. We hope that this information will be used for the development of better assessments of nanoparticles safety and for the creation of more appropriate regulations to ensure not only the safety but also the sustainability of nanotechnology.

Identifying a size-specific hazard of silica nanoparticles after intravenous administration and its relationship to the other hazards that have negative correlations with the particle size in mice

Many of the beneficial and toxic biological effects of nanoparticles have been shown to have a negative correlation with particle size. However, few studies have demonstrated biological effects that only occur at specific nanoparticle sizes. Further elucidation of the size-specific biological effects of nanoparticles may reveal not only unknown toxicities, but also novel benefits of nanoparticles. We used surface-unmodified silica particles with a wide range of diameters and narrow size intervals between the diameters (10, 30, 50, 70, 100, 300, and 1000 nm) to investigate the relationship between particle size and acute toxicity after intravenous administration in mice. Negative correlations between particle size and thrombocytopenia, liver damage, and lethal toxicity were observed. However, a specific size-effect was observed for the severity of hypothermia, where silica nanoparticles with a diameter of 50 nm induced the most severe hypothermia. Further investigation revealed that this hypothermia was mediated not by histamine, but by platelet-activating factor, and it was independent of the thrombocytopenia and the liver damage. In addition, macrophages/Kupffer cells and platelets, but not neutrophils, play a critical role in the hypothermia. The present results reveal that silica nanoparticles have particle size-specific toxicity in mice, suggesting that other types of nanoparticles may also have biological effects that only manifest at specific particle sizes. Further study of the size-specific effects of nanoparticles is essential for safer and more effective nanomedicines.

Allergic Responses Induced by the Immunomodulatory Effects of Nanomaterials upon Skin Exposure

Over the past decade, a vast array of nanomaterials has been created through the development of nanotechnology. With the increasing application of these nanomaterials in various fields, such as foods, cosmetics, and medicines, there has been concern about their safety, that is, nanotoxicity. Therefore, there is an urgent need to collect information about the biological effects of nanomaterials so that we can exploit their potential benefits and design safer nanomaterials, while avoiding nanotoxicity as a result of inhalation or skin exposure. In particular, the immunomodulating effect of nanomaterials is one of most interesting aspects of nanotoxicity. However, the immunomodulating effects of nanomaterials through skin exposure have not been adequately discussed compared with the effects of inhalation exposure, because skin penetration by nanomaterials is thought to be extremely low under normal conditions. On the other hand, the immunomodulatory effects of nanomaterials via skin may cause severe problems for people with impaired skin barrier function, because some nanomaterials could penetrate the deep layers of their allergic or damaged skin. In addition, some studies, including ours, have shown that nanomaterials could exhibit significant immunomodulating effects even if they do not penetrate the skin. In this review, we summarize our current knowledge of the allergic responses induced by nanomaterials upon skin exposure. First, we discuss nanomaterial penetration of the intact or impaired skin barrier. Next, we describe the immunomodulating effects of nanomaterials, focusing on the sensitization potential of nanomaterials and the effects of co-exposure of nanomaterials with substances such as chemical sensitizers or allergens, on the onset of allergy, following skin exposure. Finally, we discuss the potential mechanisms underlying the immunomodulating effects of nanomaterials by describing the involvement of the protein corona in the interaction of nanomaterials with biological components and by presenting recent data about the adjuvant effects of well-characterized particle adjuvant, aluminum salt, as an example of immunomodulatory particulate.

Enhancement of ovalbumin-specific Th1, Th2, and Th17 immune responses by amorphous silica nanoparticles

Nanomaterials present in cosmetics and food additives are used for industrial applications. However, their safety profile is unclear. Amorphous silica nanoparticles (nSPs) are a widely used nanomaterial and have been shown to induce inflammatory cytokines following intratracheal administration in mice. The current study investigated the adjuvant effect of nSP30 (nSP with a diameter of 33 nm) on T helper (Th)1, Th2, and Th17 immune responses as well as immunoglobulin (Ig) levels in mice. BALB/c mice were intraperitoneally administered ovalbumin (OVA) with or without varying doses and varying sizes of nSPs. The adjuvant effect of nSPs was investigated by measuring OVA-specific IgG antibodies in sera, OVA-specific proliferative responses of splenocytes, and the production of Th1, Th2, and Th17 cytokines. Aluminum hydroxide was used as a positive adjuvant control. Anti-OVA IgG production, splenocyte proliferative responses, and secretion of IFN-γ, IL-2, IL-4, IL-5, and IL-17 were increased significantly in mice receiving a combined injection of nSP30 (30 or 300 µg) with OVA compared with OVA alone or a combined injection with nSP30 (3 µg). The responses were nSP30 dose-dependent. When different sized nSPs were used (with 30, 100, and 1000 nm diameters), the responses to OVA were enhanced and were size-dependent. The smaller sized nSP particles had a greater adjuvant effect. nSPs appear to exert a size-dependent adjuvant effect for Th1, Th2, and Th17 immune responses. Understanding the mechanisms of nSP adjuvanticity might lead to the development of novel vaccine adjuvants and therapies for allergic diseases caused by environmental factors.

Development of novel drug delivery systems using phage display technology for clinical application of protein drugs

Attempts are being made to develop therapeutic proteins for cancer, hepatitis, and autoimmune conditions, but their clinical applications are limited, except in the cases of drugs based on erythropoietin, granulocyte colony-stimulating factor, interferon-alpha, and antibodies, owing to problems with fundamental technologies for protein drug discovery. It is difficult to identify proteins useful as therapeutic seeds or targets. Another problem in using bioactive proteins is pleiotropic actions through receptors, making it hard to elicit desired effects without side effects. Additionally, bioactive proteins have poor therapeutic effects owing to degradation by proteases and rapid excretion from the circulatory system. Therefore, it is essential to establish a series of novel drug delivery systems (DDS) to overcome these problems. Here, we review original technologies in DDS. First, we introduce antibody proteomics technology for effective selection of proteins useful as therapeutic seeds or targets and identification of various kinds of proteins, such as cancer-specific proteins, cancer metastasis-related proteins, and a cisplatin resistance-related protein. Especially Ephrin receptor A10 is expressed in breast tumor tissues but not in normal tissues and is a promising drug target potentially useful for breast cancer treatment. Moreover, we have developed a system for rapidly creating functional mutant proteins to optimize the seeds for therapeutic applications and used this system to generate various kinds of functional cytokine muteins. Among them, R1antTNF is a TNFR1-selective antagonistic mutant of TNF and is the first mutein converted from agonist to antagonist. We also review a novel polymer-conjugation system to improve the in vivo stability of bioactive proteins. Site-specific PEGylated R1antTNF is uniform at the molecular level, and its bioactivity is similar to that of unmodified R1antTNF. In the future, we hope that many innovative protein drugs will be developed by combining these technologies.

Cutaneous exposure to agglomerates of silica nanoparticles and allergen results in IgE-biased immune response and increased sensitivity to anaphylaxis in mice

Background

The skin is a key route of human exposure to nanomaterials, which typically occurs simultaneously with exposure to other chemical and environmental allergen. However, little is known about the hazards of nanomaterial exposure via the skin, particularly when accompanied by exposure to other substances.

Results

Repeated topical treatment of both ears and the shaved upper back of NC/Nga mice, which are models for human atopic dermatitis (AD), with a mixture of mite extract and silica nanoparticles induced AD-like skin lesions. Measurements of ear thickness and histologic analyses revealed that cutaneous exposure to silica nanoparticles did not aggravate AD-like skin lesions. Instead, concurrent cutaneous exposure to mite allergens and silica nanoparticles resulted in the low-level production of allergen-specific IgGs, including both the Th2-related IgG1 and Th1-related IgG2a subtypes, with few changes in allergen-specific IgE concentrations and in Th1 and Th2 immune responses. In addition, these changes in immune responses increased the sensitivity to anaphylaxis. Low-level IgG production was induced when the mice were exposed to allergen–silica nanoparticle agglomerates but not when the mice exposed to nanoparticles applied separately from the allergen or to well-dispersed nanoparticles.

Conclusions

Our data suggest that silica nanoparticles themselves do not directly affect the allergen-specific immune response after concurrent topical application of nanoparticles and allergen. However, when present in allergen-adsorbed agglomerates, silica nanoparticles led to a low IgG/IgE ratio, a key risk factor of human atopic allergies. We suggest that minimizing interactions between nanomaterials and allergens will increase the safety of nanomaterials applied to skin.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-015-0095-3) contains supplementary material, which is available to authorized users.

The Janus kinase inhibitor JTE-052 improves skin barrier function through suppressing signal transducer and activator of transcription 3 signaling

BACKGROUND

Barrier disruption and the resulting continuous exposure to allergens are presumed to be responsible for the development of atopic dermatitis (AD). However, the mechanism through which skin barrier function is disrupted in patients with AD remains unclear.

OBJECTIVES

Taking into account the fact that the TH2 milieu impairs keratinocyte terminal differentiation, we sought to clarify our hypothesis that the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway plays a critical role in skin barrier function and can be a therapeutic target for AD.

METHODS

We analyzed the mechanism of keratinocyte differentiation using a microarray and small interfering RNA targeting STATs. We studied the effect of the JAK inhibitor JTE-052 on keratinocyte differentiation using the human skin equivalent model and normal human epidermal keratinocytes. We applied topical JAK inhibitor onto NC/Nga mice, dry skin model mice, and human skin grafted to immunocompromised mice.

RESULTS

IL-4 and IL-13 downregulated genes involved in keratinocyte differentiation. STAT3 and STAT6 are involved in keratinocyte differentiation and chemokine production by keratinocytes, respectively. Topical application of the JAK inhibitor suppressed STAT3 activation and improved skin barrier function, permitting increases in levels of terminal differentiation proteins, such as filaggrin, and natural moisturizing factors in models of AD and dry skin and in human skin.

CONCLUSION

STAT3 signaling is a key element that regulates keratinocyte differentiation. The JAK inhibitor can be a new therapeutic tool for the treatment of disrupted barrier function in patients with AD.

Protein corona changes mediated by surface modification of amorphous silica nanoparticles suppress acute toxicity and activation of intrinsic coagulation cascade in mice

Recently, nanomaterial-mediated biological effects have been shown to be governed by the interaction of nanomaterials with some kinds of proteins in biological fluids, and the physical characteristics of the nanomaterials determine the extent and type of their interactions with proteins. Here, we examined the relationships between the surface properties of amorphous silica nanoparticles with diameters of 70 nm (nSP70), their interactions with some proteins in biological fluids, and their toxicity in mice after intravenous administration. The surface modification of nSP70 with amino groups (nSP70-N) prevented acute lethality and abnormal activation of the coagulation cascade found in the nSP70-treated group of mice. Since our previous study showed that coagulation factor XII played a role in the nSP70-mediated abnormal activation of the coagulation cascade, we examined the interaction of nSP70 and nSP70-N with coagulation factor XII. Coagulation factor XII bonded to the surface of nSP70 to a greater extent than that observed for nSP70-N, and consequently more activation of coagulation factor XII was observed for nSP70 than for nSP70-N. Collectively, our results suggest that controlling the interaction of nSP70 with blood coagulation factor XII by modifying the surface properties would help to inhibit the nSP70-mediated abnormal activation of the blood coagulation cascade.

Value of phagocyte function screening for immunotoxicity of nanoparticles in vivo

Nanoparticles (NPs) present in the environment and in consumer products can cause immunotoxic effects. The immune system is very complex, and in vivo studies are the gold standard for evaluation. Due to the increased amount of NPs that are being developed, cellular screening assays to decrease the amount of NPs that have to be tested in vivo are highly needed. Effects on the unspecific immune system, such as effects on phagocytes, might be suitable for screening for immunotoxicity because these cells mediate unspecific and specific immune responses. They are present at epithelial barriers, in the blood, and in almost all organs. This review summarizes the effects of carbon, metal, and metal oxide NPs used in consumer and medical applications (gold, silver, titanium dioxide, silica dioxide, zinc oxide, and carbon nanotubes) and polystyrene NPs on the immune system. Effects in animal exposures through different routes are compared to the effects on isolated phagocytes. In addition, general problems in the testing of NPs, such as unknown exposure doses, as well as interference with assays are mentioned. NPs appear to induce a specific immunotoxic pattern consisting of the induction of inflammation in normal animals and aggravation of pathologies in disease models. The evaluation of particle action on several phagocyte functions in vitro may provide an indication on the potency of the particles to induce immunotoxicity in vivo. In combination with information on realistic exposure levels, in vitro studies on phagocytes may provide useful information on the health risks of NPs.

Overview about the localization of nanoparticles in tissue and cellular context by different imaging techniques

The increasing interest and recent developments in nanotechnology pose previously unparalleled challenges in understanding the effects of nanoparticles on living tissues. Despite significant progress in in vitro cell and tissue culture technologies, observations on particle distribution and tissue responses in whole organisms are still indispensable. In addition to a thorough understanding of complex tissue responses which is the domain of expert pathologists, the localization of particles at their sites of interaction with living structures is essential to complete the picture. In this review we will describe and compare different imaging techniques for localizing inorganic as well as organic nanoparticles in tissues, cells and subcellular compartments. The visualization techniques include well-established methods, such as standard light, fluorescence, transmission electron and scanning electron microscopy as well as more recent developments, such as light and electron microscopic autoradiography, fluorescence lifetime imaging, spectral imaging and linear unmixing, superresolution structured illumination, Raman microspectroscopy and X-ray microscopy. Importantly, all methodologies described allow for the simultaneous visualization of nanoparticles and evaluation of cell and tissue changes that are of prime interest for toxicopathologic studies. However, the different approaches vary in terms of applicability for specific particles, sensitivity, optical resolution, technical requirements and thus availability, and effects of labeling on particle properties. Specific bottle necks of each technology are discussed in detail. Interpretation of particle localization data from any of these techniques should therefore respect their specific merits and limitations as no single approach combines all desired properties.

Engineered nanomaterial exposure and the risk of allergic disease

PURPOSE OF REVIEW

Although the production and use of engineered nanomaterials (ENMs) is rapidly increasing, we lack sufficient knowledge regarding their capacity to induce and/or promote allergic disease. As novel ENMs are being developed and used for biomedical applications, such as drug delivery, it will be critical to understand the relationship between physicochemical properties of ENMs and possible mechanisms of immunomodulation.

RECENT FINDINGS

Cellular studies and a few animal studies have begun to examine the immunomodulatory effects of ENM exposure that may be predictive of developing allergic reactions. Specifically, the effects of direct ENM exposure on key immune cells recognized to facilitate allergic disease has been evaluated and will be discussed. However, few studies have reported specific physicochemical properties of ENMs that initiate allergic immune responses. Although limited, these descriptive studies point to the induction of cellular mechanisms that are well known to promote allergic disease.

SUMMARY

The limited data currently available suggest that there is a potential risk for the development of allergic responses following exposure to ENMs. As more ENMs are developed for consumer products and nanomedicines, further study on their potential for adverse immune interactions will be necessary for safe implementation of these novel materials.

Intestinal absorption and biological effects of orally administered amorphous silica particles

Although amorphous silica nanoparticles are widely used in the production of food products (e.g., as anticaking agents), there is little information available about their absorption and biological effects after oral exposure. Here, we examined the in vitro intestinal absorption and in vivo biological effects in mice of orally administered amorphous silica particles with diameters of 70, 300, and 1,000 nm (nSP70, mSP300, and mSP1000, respectively) and of nSP70 that had been surface-modified with carboxyl or amine groups (nSP70-C and nSP70-N, respectively). Analysis of intestinal absorption by means of the everted gut sac method combined with an inductively coupled plasma optical emission spectrometer showed that the intestinal absorption of nSP70-C was significantly greater than that of nSP70. The absorption of nSP70-N tended to be greater than that of nSP70; however, the results were not statistically significant. Our results indicate that silica nanoparticles can be absorbed through the intestine and that particle diameter and surface properties are major determinants of the degree of absorption. We also examined the biological effects of the silica particles after 28-day oral exposure in mice. Hematological, histopathological, and biochemical analyses showed no significant differences between control mice and mice treated with the silica particles, suggesting that the silica nanoparticles evaluated in this study are safe for use in food production.

Nanomedicine strategies for targeting skin inflammation

Topical treatment of skin diseases is an attractive strategy as it receives high acceptance from patients, resulting in higher compliance and therapeutic outcomes. Recently, the use of variable nanocarriers for dermal application has been widely explored, as they offer several advantages compared with conventional topical preparations, including higher skin penetration, controlled and targeted drug delivery and the achievement of higher therapeutic effects. This article will focus on skin inflammation or dermatitis as it is one of the most common skin problems, describing the different types and causes of dermatitis, as well as the typical treatment regimens. The potential use of nanocarriers for targeting skin inflammation and the achievement of higher therapeutic effects using nanotechnology will be explored.

Silica nanoparticles induce autophagy and autophagic cell death in HepG2 cells triggered by reactive oxygen species

Silica nanoparticles (SNPs) are becoming favorable carriers for drug delivery or gene therapy, and in turn, the toxic effect of SNPs on biological systems is gaining attention. Currently, autophagy is recognized as an emerging toxicity mechanism triggered by nanomaterials, yet there have been scarcely research about the mechanisms of autophagy and autophagic cell death associated with SNPs. In this study, we verified the activation of SNPs-induced autophagy via the MDC-staining and LC3-I/LC3-II conversion, resulted in a dose-dependent manner. The typically morphological characteristics (autophagosomes and autolysosomes) of the autophagy process were observed in TEM ultrastructural analysis. In addition, the autophagic cell death was evaluated by cellular co-staining assay. And the underlying mechanisms of autophagy and autophagic cell death were performed using the intracellular ROS detection, autophagy inhibitor and ROS scavenger. Results showed that the elevated ROS level was in line with the increasing of autophagy activation, while both the 3-MA and NAC inhibitors effectively suppressed the autophagy and cell death induced by SNPs. In summary, our findings demonstrated that the SNPs-induced autophagy and autophagic cell death were triggered by the ROS generation in HepG2 cells, suggesting that exposure to SNPs could be a potential hazardous factor for maintaining cellular homeostasis.

Effect of silica particle size on macrophage inflammatory responses

Amorphous silica particles, such as nanoparticles (<100 nm diameter particles), are used in a wide variety of products, including pharmaceuticals, paints, cosmetics, and food. Nevertheless, the immunotoxicity of these particles and the relationship between silica particle size and pro-inflammatory activity are not fully understood. In this study, we addressed the relationship between the size of amorphous silica (particle dose, diameter, number, and surface area) and the inflammatory activity (macrophage phagocytosis, inflammasome activation, IL-1β secretion, cell death and lung inflammation). Irrespective of diameter size, silica particles were efficiently internalized by mouse bone marrow-derived macrophages via an actin cytoskeleton-dependent pathway, and induced caspase-1, but not caspase-11, activation. Of note, 30 nm-1000 nm diameter silica particles induced lysosomal destabilization, cell death, and IL-1β secretion at markedly higher levels than did 3000 nm-10000 nm silica particles. Consistent with in vitro results, intra-tracheal administration of 30 nm silica particles into mice caused more severe lung inflammation than that of 3000 nm silica particles, as assessed by measurement of pro-inflammatory cytokines and neutrophil infiltration in bronchoalveolar lavage fluid of mice, and by the micro-computed tomography analysis. Taken together, these results suggest that silica particle size impacts immune responses, with submicron amorphous silica particles inducing higher inflammatory responses than silica particles over 1000 nm in size, which is ascribed not only to their ability to induce caspase-1 activation but also to their cytotoxicity.

Perturbation of physiological systems by nanoparticles

Nanotechnology is having a tremendous impact on our society. However, societal concerns about human safety under nanoparticle exposure may derail the broad application of this promising technology. Nanoparticles may enter the human body via various routes, including respiratory pathways, the digestive tract, skin contact, intravenous injection, and implantation. After absorption, nanoparticles are carried to distal organs by the bloodstream and the lymphatic system. During this process, they interact with biological molecules and perturb physiological systems. Although some ingested or absorbed nanoparticles are eliminated, others remain in the body for a long time. The human body is composed of multiple systems that work together to maintain physiological homeostasis. The unexpected invasion of these systems by nanoparticles disturbs normal cell signaling, impairs cell and organ functions, and may even cause pathological disorders. This review examines the comprehensive health risks of exposure to nanoparticles by discussing how nanoparticles perturb various physiological systems as revealed by animal studies. The potential toxicity of nanoparticles to each physiological system and the implications of disrupting the balance among systems are emphasized.

AHAPS-functionalized silica nanoparticles do not modulate allergic contact dermatitis in mice

Allergic contact dermatitis (ACD) is a common skin disease in people and may become a potential site of exposure to nanoparticles (NP). Silica nanoparticles (SiO2-NP) possess a promising potential for various medical and non-medical applications, including normal and diseased skin as target organs. However, it has been shown that negatively charged SiO2-NP may act as proinflammatory adjuvant in allergic diseases. The effect of topical SiO2-NP exposure on preexisting ACD has not been studied to date although this reflects a common in vivo situation. Of particular interest are the potential effects of positively charged N-(6-aminohexyl)-aminopropyltrimethoxysilane (AHAPS)-functionalized SiO2-NP which are promising candidates for delivery systems, including gene delivery into the skin. Here, the effects of such AHAPS-functionalized SiO2-NP (55 ± 6 nm in diameter) were studied in an oxazolone-induced ACD model in SKH1 mice and compared to ACD mice treated with vehicle only. The clinical course of the disease was assessed by monitoring of the transepidermal water loss (TEWL) and the erythema. In histologic and morphometric analyses, the distribution of particles, the degree of inflammation, epidermal thickness, and the inflammatory infiltrate were characterized and quantified by standard and special histological stains as well as immunohistochemistry for CD3+ lymphocytes. To assess possible systemic effects, serum immunoglobulin E (IgE) was determined by enzyme-linked immunosorbent assay. Following administration of AHAPS-SiO2-NP for five consecutive days, no effects were observed in all clinical, histologic, morphometric, and molecular parameters investigated. In conclusion, positively charged AHAPS-SiO2-NP seem not to affect the course of ACD during exposure for 5 days.