Environmental, health and safety issues: Nanoparticles in the real world

Hazard profiling of a combinatorial library of zinc oxide nanoparticles: Ameliorating light and dark toxicity through surface passivation

Zinc oxide (ZnO) is one of the high-volume production nanoparticles (NPs) currently used in a wide range of consumer and industrial goods. The inevitable seepage into environmental matrices and the photoactive nature of ZnO NPs warrants hazard profiling under environmentally related conditions. In this paper, the influence of simulated solar light (SSL) on dissolution behaviour and phototoxicity of ZnO NPs was studied using a combinatorial library of ZnO NPs with different sizes, surface coatings, dopant chemistry, and aspect ratios in a fish cell line (BF2) and zebrafish embryos. Generally, the cytotoxicity and embryo mortality increased when exposed concomitantly to SSL and ZnO NPs. The increase in toxic potential of ZnO NPs during SSL exposure concurred with release of Zn ions and ROS generation. Surface modification of NPs with poly(methacrylic acid) (PMAA), silica or serum coating decreased toxicity and ZnO with serum coating was the only NP that had no significant effect on any of the cytotoxicity parameters when tested under both dark and SSL conditions. Results from our study show that exposure to light could increase the toxic potential of ZnO NPs to environmental lifeforms and mitigation of ZnO NP toxicity is possible through modifying the surface chemistry.

Plant Extract-Based Synthesis of Metallic Nanomaterials, Their Applications, and Safety Concerns

Nanotechnology has attracted the attention of researchers from different scientific fields because of the escalated properties of nanomaterials compared with the properties of macromolecules. Nanomaterials can be prepared through different approaches involving physical and chemical methods. The development of nanomaterials through plant-based green chemistry approaches is more advantageous than other methods from the perspectives of environmental safety, animal, and human health. The biomolecules and metabolites of plants act as reducing and capping agents for the synthesis of metallic green nanomaterials. Plant-based synthesis is a preferred approach as it is not only cost-effective, easy, safe, clean, and eco-friendly but also provides pure nanomaterials in high yield. Since nanomaterials have antimicrobial and antioxidant potential, green nanomaterials synthesized from plants can be used for a variety of biomedical and environmental remediation applications. Past studies have focused mainly on the overall biogenic synthesis of individual or combinations of metallic nanomaterials and their oxides from different biological sources, including microorganisms and biomolecules. Moreover, from the viewpoint of biomedical applications, the literature is mainly focusing on synthetic nanomaterials. Herein, we discuss the extraction of green molecules and recent developments in the synthesis of different plant-based metallic nanomaterials, including silver, gold, platinum, palladium, copper, zinc, iron, and carbon. Apart from the biomedical applications of metallic nanomaterials, including antimicrobial, anticancer, diagnostic, drug delivery, tissue engineering, and regenerative medicine applications, their environmental remediation potential is also discussed. Furthermore, safety concerns and safety regulations pertaining to green nanomaterials are also discussed. This article is protected by copyright. All rights reserved.

Risk assessment on-a-chip: a cell-based microfluidic device for immunotoxicity screening

Nanomaterials are widely used in industrial and clinical settings due to their unique physical and chemical properties. However, public health and environmental concerns have emerged owing to their undesired toxicity and ability to trigger immune responses. This paper presents the development of a microfluidic-based cell biochip device that enables the administration of nanoparticles under laminar flow to cells of the immune system to assess their cytotoxicity. The exposure of human B lymphocytes to 10 nm silver nanoparticles under fluid flow led to a 3-fold increase in toxicity compared to static conditions, possibly indicating enhanced cell-nanoparticle interactions. To investigate whether the administration under flow was the main contributing factor, we compared and validated the cytotoxicity of the same nanoparticles in different platforms, including the conventional well plate format and in-house fabricated microfluidic devices under both static and dynamic flow conditions. Our results suggest that commonly employed static platforms might not be well-suited to perform toxicological screening of nanomaterials and may lead to an underestimation of cytotoxic responses. The simplicity of the developed flow system makes this setup a valuable tool to preliminary screen nanomaterials.

Molecular and cellular cues governing nanomaterial-mucosae interactions: from nanomedicine to nanotoxicology

Mucosal tissues constitute the largest interface between the body and the surrounding environment and they regulate the access of molecules, supramolecular structures, particulate matter, and pathogens into it. All mucosae are characterized by an outer mucus layer that protects the underlying cells from physicochemical, biological and mechanical insults, a mono-layered or stratified epithelium that forms tight junctions and controls the selective transport of solutes across it and associated lymphoid tissues that play a sentinel role. Mucus is a gel-like material comprised mainly of the glycoprotein mucin and water and it displays both hydrophilic and hydrophobic domains, a net negative charge, and high porosity and pore interconnectivity, providing an efficient barrier for the absorption of therapeutic agents. To prolong the residence time, absorption and bioavailability of a broad spectrum of active compounds upon mucosal administration, mucus-penetrating and mucoadhesive particles have been designed by tuning the chemical composition, the size, the density, and the surface properties. The benefits of utilizing nanomaterials that interact intimately with mucosae by different mechanisms in the nanomedicine field have been extensively reported. To ensure the safety of these nanosystems, their compatibility is evaluated in vitro and in vivo in preclinical and clinical trials. Conversely, there is a growing concern about the toxicity of nanomaterials dispersed in air and water effluents that unintentionally come into contact with the airways and the gastrointestinal tract. Thus, deep understanding of the key nanomaterial properties that govern the interplay with mucus and tissues is crucial for the rational design of more efficient drug delivery nanosystems (nanomedicine) and to anticipate the fate and side-effects of nanoparticulate matter upon acute or chronic exposure (nanotoxicology). This review initially overviews the complex structural features of mucosal tissues, including the structure of mucus, the epithelial barrier, the mucosal-associated lymphatic tissues and microbiota. Then, the most relevant investigations attempting to identify and validate the key particle features that govern nanomaterial-mucosa interactions and that are relevant in both nanomedicine and nanotoxicology are discussed in a holistic manner. Finally, the most popular experimental techniques and the incipient use of mathematical and computational models to characterize these interactions are described.

Analysis of the Direct and Indirect Effects of Nanoparticle Exposure on Microglial and Neuronal Cells In Vitro

Environmental or biomedical exposure to nanoparticles (NPs) can results in translocation and accumulation of NPs in the brain, which can lead to health-related problems. NPs have been shown to induce toxicity to neuronal cells through several direct mechanisms, but only a few studies have also explored the indirect effects of NPs, through consequences due to the exposure of neighboring cells to NPs. In this study, we analysed possible direct and indirect effects of NPs (polyacrylic acid (PAA) coated cobalt ferrite NP, TiO2 P25 and maghemite NPs) on immortalized mouse microglial cells and differentiated CAD mouse neuronal cells in monoculture (direct toxicity) or in transwell co-culture system (indirect toxicity). We showed that although the low NP concentrations (2-25 µg/mL) did not induce changes in cell viability, cytokine secretion or NF-κB activation of microglial cells, even low NP concentrations of 10 µg/mL can affect the cells and change their secretion of protein stress mediators. These can in turn influence neuronal cells in indirect exposure model. Indirect toxicity of NPs is an important and not adequately assessed mechanism of NP toxicity, since it not only affects cells on the exposure sites, but through secretion of signaling mediators, can also affect cells that do not come in direct contact with NPs.

Insights into the effect of cerium oxide nanoparticle on microalgal degradation of sulfonamides

Nanoparticles have been commercially used worldwide; however, there is a lack of information of their environmental impacts and ecotoxicity. In this study, the effect of cerium oxide nanoparticle (CeO₂NP) on a green microalga Scenedesmus obliquus, and microalgal biodegradation of four sulfonamides (sulfamethazine, sulfamethoxazole, sulfadiazine, and sulfamethoxazole) was investigated. There is insignificant inhibition of microalgal growth induced by CeO₂NP; however, it substantially influenced the expression of genes involved in key cellular metabolic activities of S. obliquus. For example, genes involved in photosynthetic activity (psbA) and energy production (ATPF0C) were downregulated with exposure to CeO₂NP. The low concentrations of CeO₂NP improved microalgal degradation of sulfonamides. This may be because of the upregulated genes encoding hydrogenase and oxidoreductase. The exploration of this study has provided a new understanding of the environmental impacts of CeO₂NP on microalgae-based biotechnologies for treatment of wastewater containing emerging organic contaminants.

Toxicity mechanisms of selected engineered nanoparticles on human neural cells in vitro

Environmental exposure to nanoparticles (NPs) has significantly increased in the last decades, mostly due to increased environmental pollution and frequent use of NP containing consumer products. Such NPs may enter our body and cause various health-related problems. The brain is a particularly problematic accumulation site due to its physiological and anatomical restrictions. Several mechanisms of NP neurotoxicity have already been identified, however not enough is known especially regarding toxicity of engineered/industrial NPs. The focus of this in vitro study was on analysis of neurotoxicity of different engineered NPs, with which we come into contact in our daily lives; SiO₂ NPs, food grade (FG) TiO₂ NPs, TiO₂ P25 and silver NPs as examples of industrial NPs, and polyacrylic acid (PAA) coated cobalt ferrite NPs as an example of biomedical NPs. All short term exposure experiments (24-72 h) were performed on SH-SY5Y human neuroblastoma cell line in vitro using higher (25-50 μg/ml) as well as lower (2-10 μg/ml), concentrations that are more relevant for in vivo NPs exposure. We show that NPs can cause neurotoxicity through different mechanisms, such as membrane damage, cell cycle interference, ROS formation and accumulation of autophagosomes, depending on their physico-chemical properties and stability in physiological media. Low, in vivo achievable concentrations of NPs induced only minor or no changes in vitro, however prolonged exposure and accumulation in vivo could negatively affect the cells. This was also shown in case of autophagy dysfunction for TiO₂ P25 NPs and decrease of cell viability for TiO₂ FG NPs, which were only evident after 72 h of incubation.

Transcriptome Reveals the Rice Response to Elevated Free Air CO2 Concentration and TiO2 Nanoparticles

Increasing CO₂ levels are speculated to change the effects of engineered nanomaterials in soil and on plant growth. How plants will respond to a combination of elevated CO₂ and nanomaterials stress has rarely been investigated, and the underlying mechanism remains largely unknown. Here, we conducted a field experiment to investigate the rice (Oryza sativa L. cv. IIyou) response to TiO₂ nanoparticles (nano-TiO₂, 0 and 200 mg kg^-1) using a free-air CO₂ enrichment system with different CO₂ levels (ambient ∼370 μmol mol^-1 and elevated ∼570 μmol mol^-1). The results showed that elevated CO₂ or nano-TiO₂ alone did not significantly affect rice chlorophyll content and antioxidant enzyme activities. However, in the presence of nano-TiO₂, elevated CO₂ significantly enhanced the rice height, shoot biomass, and panicle biomass (by 9.4%, 12.8%, and 15.8%, respectively). Furthermore, the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that genes involved in photosynthesis were up-regulated while most genes associated with secondary metabolite biosynthesis were down-regulated in combination-treated rice. This indicated that elevated CO₂ and nano-TiO₂ might stimulate rice growth by adjusting resource allocation between photosynthesis and metabolism. This study provides novel insights into rice responses to increasing contamination under climate change.

Highly integrated nanocomposites of RGO/TiO2 nanotubes for enhanced removal of microbes from water

Highly integrated nanocomposite of Graphene oxide (GO) and its derivatives with metal oxides is essential for enhanced performance for various applications. Tuning the morphology is an important aspect during nanomaterials synthesis; this has an amplifying influence upon physicochemical properties of advanced functional materials. In this research work, GO/TiO₂ nanotube composites have been successfully synthesized via alkaline hydrothermal treatment method by augmenting GO layers with two different phases of TiO₂ (anatase and rutile) nanoparticles, followed by the hydrothermal treatment that also have caused reduction of GO to reduced GO (RGO). The morphology of the as-prepared samples appeared to be nanotubes with a large aspect ratio (length to diameter). The synthesized materials have been characterized using various techniques to determine their morphological and functional properties. Large surface area (158 m²/g) nanotube composites found accountable as effective disinfectant for water containing microorganisms. The antimicrobial activity of the synthesized composites was examined by disk diffusion method and optical density for bacterial growth using two different bacterial species; Escherichia Coli (E.coli, Gram-negative) and Staphylococcus Aureus (Methicillin-resistant Staphylococcus aureus, Gram-positive). The antibacterial study revealed that, the anatase phase RGO/TiO₂ nanotube composites manifested appreciable effect on both bacteria as compared to rutile phase RGO/TiO₂ nanotubecomposite.

Advanced Functional Fibrous Materials for Enhanced Thermoregulating Performance

The concept of thermoregulating textiles capable of providing personal thermal management property (PTM) has attracted significant attention in recent years. It is considered as an emerging approach to promote the comfort and general well-being of wearers and also to mitigate the energy consumption load for indoor living space conditioning. Regulating the heat exchange between human body and environment has been the core subject of many studies on introducing the PTM functionality to textiles. This work provides an overview of the latest literature, summarizing the recent innovations and state-of-the-art approaches of controlling the heat gain and loss of textiles. To this end, methods to control the fundamental aspects of heat gain and loss of fabrics such as using near-infrared reflective materials and conductive nanomaterials, designing photonic structures of fabrics, and engineering nanoporous structures for passive cooling and heating effects will be discussed. Moreover, specific attention is given to the application of phase change materials in textiles, their integration methods, and the associated mechanisms. Several commercial methods such as adapting the innovative designs, introducing moisture management capability, and using air/liquid thermoregulating systems will also be discussed. This review article provides a clear picture of the concept of thermoregulating textiles and recommends some future research trajectories for this emerging field.

A repertoire of biomedical applications of noble metal nanoparticles

The emerging properties of noble metal nanoparticles are attracting huge interest from the translational scientific community. In this feature article, we highlight recent advances in the adaptation of noble metal nanomaterials and their biomedical applications in therapeutics, diagnostics and sensing.

The effects of predicted environmentally relevant concentrations of ZnO nanoparticles on the behavior of Gallus gallus domesticus (Phasianidae) chicks

The toxicity of ZnO nanoparticles (NPs) has been the subject of several investigations; however, concentrations much higher than the ones potentially found in the environment are often tested. In addition, groups of animals such as birds have not been used as model in studies in this field, fact that creates an important ecotoxicological gap in them. The aim of the present study is to investigate the effects of the exposure to environmentally relevant concentrations of ZnO nanoparticles on the anti-predatory behavior of chicks (Gallus gallus domesticus). The test animals were daily exposed to an environmentally relevant concentration of ZnO nanoparticles (0.245 mg kg^-1) and to a toxic concentration of it (245.26 mg kg^-1) through intraperitoneal injection for two days. We set a control group for comparison purposes. According to our results, ZnO nanoparticles did not affect the locomotor activity of, and did not cause anxiolytic or anxiogenic effect on, birds in the open field test. However, based on the lowest cluster score recorded during the social aggregation test, chicks exposed to ZnO nanoparticles failed to recognize the grunt of a hawk (Rupornis magnirostris) as predatory threat. Only birds in the control group recognized the test snake (Pantherophis guttatus) as potential predator. The higher Zn concentration in the brains of animals exposed to ZnO nanoparticles evidenced the capacity of these nanomaterials to cross the blood-brain barrier, even at low concentrations. This blood-brain barrier crossing could have affected the structures or neuronal mechanisms that modulate the defensive response of birds. Assumingly, even the minimal exposure to low concentrations of ZnO nanoparticles can affect birds. Our outcomes corroborate previous studies about the biological risks of water surface contamination by metal-based nanomaterials.

Inactivation of Pure Bacterial Biofilms by Impaction of Aerosolized Consumer Products Containing Nanoparticulate Metals

The ability of nanotechnology-enabled consumer sprays to inactivate bacteria has direct health implications. This research investigated the ability of six nanosilver-based consumer sprays to inactivate bacteria. We determined the minimal inhibitory concentrations (MICs) of the products by an agar dilution method, collected particles released from sprays onto bacterial films using impactors, and determined metal concentrations in the products using ICPMS. Also, the size of silver nanoparticles in the products' suspensions was determined using single particle (sp)ICPMS. Two of the six nanoproducts inhibited growth of Escherichia coli and Bacillus atrophaeus bacteria (MICs of 40,000 and 160,000 ppm). Collection of particles aerosolized from these two products onto films of the same bacteria inhibited bacterial growth; however, the mass concentration deposited onto bacterial films was lower than the MICs. Furthermore, these two nanoproducts had the lowest silver concentrations compared to the other four nanosilver products. Yet, they had the smallest nanosilver particles: mean size of ~20 to 30 nm vs. ~45 nm for the other products. Their suspensions were more acidic (pH ~3-5) and had higher concentrations of zinc and magnesium compared to other products. This research illustrates that some consumer nanoproducts have antibacterial potential and may affect our microbiota. Yet, the inactivation potential cannot solely be presumed based on the nanosilver presence and concentration in the product; the final nanoproduct's form, including its matrix, must be considered. As nanomaterials are increasingly incorporated into consumer goods, this research highlights the need to investigate final-form consumer nanoproducts and their potential to affect our microbial environment.

Zinc oxide nanoparticles in predicted environmentally relevant concentrations leading to behavioral impairments in male swiss mice

Although the potential neurotoxic effects from the exposure to zinc oxide nanoparticles (ZnO NPs) on humans and on experimental models have been reported in previous studies, the effects from the exposure to environmentally relevant concentrations of them remain unclear. Thus, the aim of the present study is to investigate the effects from the exposure to environmentally relevant concentrations of ZnO NPs on the behavior of male Swiss mice. The animals were daily exposed to environmentally relevant concentrations of ZnO NPs (5.625×10^-5mgkg^-1) at toxic level (300mgkg^-1) through intraperitoneal injection for five days; a control group was set for comparison purposes. Positive control groups (clonazepam and fluoxetine) and a baseline group were included in the experimental design to help analyzing the behavioral tests (open field, elevated plus maze and forced swim tests). Although we did not observe any behavioral change in the animals subjected to the elevated plus maze and forced swim tests, our data evidence the anxiogenic behavior of animals exposed to the two herein tested ZnO NPs concentrations in the open field test. The animals stayed in the central part of the apparatus and presented lower locomotion ratio in the central quadrants/total of locomotion during this test. It indicates that the anxiogenic behavior was induced by ZnO NP exposure, because it leads to Zn accumulation in the brain. Thus, the current study is the first to demonstrate that the predicted environmentally relevant ZnO NPs concentration induces behavioral changes in mammalian experimental models. Our results corroborate previous studies that have indicated the biological risks related to the water surface contamination by metal-based nanomaterials.

Is Neurotoxicity of Metallic Nanoparticles the Cascades of Oxidative Stress?

With the rapid development of nanotechnology, metallic (metal or metal oxide) nanoparticles (NPs) are widely used in many fields such as cosmetics, the food and building industries, and bio-medical instruments. Widespread applications of metallic NP-based products increase the health risk associated with human exposures. Studies revealed that the brain, a critical organ that consumes substantial amounts of oxygen, is a primary target of metallic NPs once they are absorbed into the body. Oxidative stress (OS), apoptosis, and the inflammatory response are believed to be the main mechanisms underlying the neurotoxicity of metallic NPs. Other studies have disclosed that antioxidant pretreatment or co-treatment can reverse the neurotoxicity of metallic NPs by decreasing the level of reactive oxygen species, up-regulating the activities of antioxidant enzymes, decreasing the proportion of apoptotic cells, and suppressing the inflammatory response. These findings suggest that the neurotoxicity of metallic NPs might involve a cascade of events following NP-induced OS. However, additional research is needed to determine whether NP-induced OS plays a central role in the neurotoxicity of metallic NPs, to develop a comprehensive understanding of the correlations among neurotoxic mechanisms and to improve the bio-safety of metallic NP-based products.

Boiling Method-Based Zinc Oxide Nanorods for Enhancement of Adipose-Derived Stem Cell Proliferation

Adipose-derived stem cells (ASCs) are typically expanded to acquire large numbers of cells for therapeutic applications. Diverse stimuli such as sphingosylphosphocholine and vitamin C have been used to increase the production yield and regenerative potential of ASCs. In the present study, we hypothesized that ZnO nanorods have promising potential for the enhancement of ASC proliferation. ZnO nanorods were prepared using three different methods: grinding and boiling at low temperature with and without surfactant. The physicochemical properties of the nanorods such as their crystallinity, morphology, size, and solvent compatibility were evaluated, and then, the ability of the synthesized ZnO nanorods to enhance ASC proliferation was investigated. Scanning electron microscopy images of all of the ZnO powders showed rod-shaped nanoflakes with lengths of 200-500 nm. Notably, although ZnO-G produced by the grinding method was well dispersed in ethanol, atomic force microscopy images of dispersions of both ZnO-B from boiling methods and ZnO-G indicated the presence of clusters of ZnO nanorods. In contrast, ZnO-B was freely dispersible in 5% dextrose of water and dimethyl sulfoxide, whereas ZnO-G and ZnO-M, produced by boiling with ethanolamine, were not. All three types of ZnO nanorods increased the proliferation of ASCs in a dose-dependent manner. These results collectively suggest that ZnO nanorods have promising potential for use as an agent for the enhancement of ASC proliferation.

APTES-modified nanosilica--but neither APTES nor nanosilica--inhibits endothelial cell growth via arrest of cell cycle at G1 phase

The adverse effects of nanomaterials on the living system have attracted considerable attention in the past few years. Such effects may come from either the core nanomaterials or the chemical agents used to modify the nanomaterials - the latter being largely overlooked. In a free form, these modifying agents might have little impact on living cells; however, they may exhibit distinct biological effects when they assemble into a larger dimension. Here, we report that (3-aminopropyl)triethoxysilane - a small molecule compound ubiquitously employed to functionalise nanosilica surface - could decrease the viability of human umbilical vein endothelial cells when it was grafted onto the nanosilica surface. However, intriguingly, such effect was not found in 3-aminopropyl)triethoxysilane itself, the unmodified silica nanoparticles or the 3-aminopropyl)triethoxysilane-modified microparticles. Change of surface charge was excluded as a cause and apoptosis was not observed. Nevertheless, the 3-aminopropyl)triethoxysilane-modified nanoparticles could exclusively arrest cell cycle at G1 phase. Our findings suggest that substances could gain 'new' functions at the nanoscale, which may not be found in their larger or smaller counterparts. Understanding of such effects will provide critical insights for better evaluation and thus safer use of nanomaterials, in particular those having been pre-modified with other agents.

Nanomaterials in consumer products: a challenging analytical problem

Many products used in everyday life are made with the assistance of nanotechnologies. Cosmetic, pharmaceuticals, sunscreen, powdered food are only few examples of end products containing nano-sized particles (NPs), generally added to improve the product quality. To evaluate correctly benefits vs. risks of engineered nanomaterials and consequently to legislate in favor of consumer's protection, it is necessary to know the hazards connected with the exposure levels. This information implies transversal studies and a number of different competences. On analytical point of view the identification, quantification and characterization of NPs in food matrices and in cosmetic or personal care products pose significant challenges, because NPs are usually present at low concentration levels and the matrices, in which they are dispersed, are complexes and often incompatible with analytical instruments that would be required for their detection and characterization. This paper focused on some analytical techniques suitable for the detection, characterization and quantification of NPs in food and cosmetics products, reports their recent application in characterizing specific metal and metal-oxide NPs in these two important industrial and market sectors. The need of a characterization of the NPs as much as possible complete, matching complementary information about different metrics, possible achieved through validate procedures, is what clearly emerges from this research. More work should be done to produce standardized materials and to set-up methodologies to determine number-based size distributions and to get quantitative date about the NPs in such a complex matrices.

Effects of aspect ratio (AR) and specific surface area (SSA) on cytotoxicity and phototoxicity of ZnO nanomaterials

With growing interests in the applications of high aspect ratio (AR) ZnO nanomaterials (NMs), their potential toxicity to human health and nature environment remains a critical concern because these NMs have extremely large specific surface area (SSA) that could dramatically enhance interactions between NMs and surrounding molecules. In addition, originated to their intrinsic photocatalytical activity, ZnO NMs may induce phototoxicity under environmentally UV exposure. In this paper, ZnO spheres, grains, rods and needles with increasing AR (from 1.1 to 17.8) and various SSA (from 2.0 m(2) g(-1) to 27.4 m(2) g(-1)) were used to study the influence of AR and SSA on viabilities of WIL2-NS human lymphoblastoid cells in both dark and UV conditions. In dark, SSA was the main influencing factor for toxicity of NMs with low AR (spheres, grains and rods) and smaller SSA leads to higher cell viability. However, ZnO needles with the smallest SSA did not further enhance cell viability which may be possibly attributed to its high AR. Cell viability measured under UV irradiation did not show evident relationship with SSA or AR, but indicated that lower photocatalytic activity could mitigate phototoxicity.

Facile preparation of Chevreul's salt (Cu2SO3·CuSO3·2H2O) mesocrystalline microspheres and their high photocatalytic activity

Cu₂SO₃·CuSO₃·2H₂O mesocrystalline microspheres with excellent photocatalytic performance, composed of sub-microparticles in an oriented fashion, are synthesized by a facile method.

Lab-on-a-chip-based high-throughput screening of the genotoxicity of engineered nanomaterials

The continuous increasing of engineered nanomaterials (ENMs) in our environment, their combinatorial diversity, and the associated genotoxic risks, highlight the urgent need to better define the possible toxicological effects of ENMs. In this context, we present a new high-throughput screening (HTS) platform based on the cytokinesis-block micronucleus (CBMN) assay, lab-on-chip cell sorting, and automated image analysis. This HTS platform has been successfully applied to the evaluation of the cytotoxic and genotoxic effects of silver nanoparticles (AgNPs) and silica nanoparticles (SiO2NPs). In particular, our results demonstrate the high cyto- and genotoxicity induced by AgNPs and the biocompatibility of SiO2NPs, in primary human lymphocytes. Moreover, our data reveal that the toxic effects are also dependent on size, surface coating, and surface charge. Most importantly, our HTS platform shows that AgNP-induced genotoxicity is lymphocyte sub-type dependent and is particularly pronounced in CD2+ and CD4+ cells.

The gut wall provides an effective barrier against nanoparticle uptake

BACKGROUND

The omnipresence of nanoparticles (NPs) in numerous goods has led to a constant risk of exposure and inadvertent uptake for humans. This situation calls for thorough investigation of the consequences of NP intake. As the vast mucosa of the human gastrointestinal tract represents an attractive site of entry, we wanted to take a look on the fate that ingested NPs suffer in the gut. As a model to investigate NP uptake we used the isolated perfused rat small intestine. Differently sized fluorescent latex particles were used as exemplary anthropogenic NPs.

RESULTS

The particles were administered as bolus into the isolated intestine, and samples from the luminal, vascular and lymphatic compartments were collected over time. NP amounts in the different fluids were determined by fluorescence measurements. No particles could be detected in the vascular and lymphatic system. By contrast a major amount of NPs was found in luminal samples. Yet, a substantial share of particles could not be recovered in the fluid fractions, indicating a sink function of the intestinal tissue for NPs. A histological examination of the gut revealed that virtually no particles adhered to the epithelium or resided in the tissue, the bulk of particles seemed to be trapped in the mucus lining the gut tube. When this mucus was dissolved and removed from the gut almost the entire amount of particles missing could be recovered: over 95% of the given NPs were present in the two fractions, the luminal samples and the dissolved mucus. To foster NP uptake via an extended interaction time with the epithelium, the intestinal peristalsis was decelerated and the duration of the experiment was prolonged. Even under those conditions, no particle fluorescence was detected in the vascular and lymphatic samples.

CONCLUSION

We could show that after intestinal exposure with a large dose of NPs the vast majority of NPs did obviously not come into contact with the epithelium but was either directly discarded from the gut or trapped in mucus. The healthy small intestinal tract evidently provides an effective barrier against NP uptake whereby the mucus film seems to play an important role.

Ultrasonic phosphate bonding of nanoparticles

Low intensity ultrasound-induced radicals interact with surface adsorbed orthophosphate to bond nanoparticles with high mechanical strength and surface area. Dissimilar materials could be bonded to form robust metallic, ceramic, and organic composite microparticles. 3D nanostructures of a hydrated and amorphous electrocatalyst with carbon nanotubes were also constructed which exceeded the resistance-limited efficiency of 2D electrodes.

Development of structure-activity relationship for metal oxide nanoparticles

Nanomaterial structure-activity relationships (nano-SARs) for metal oxide nanoparticles (NPs) toxicity were investigated using metrics based on dose-response analysis and consensus self-organizing map clustering. The NP cellular toxicity dataset included toxicity profiles consisting of seven different assays for human bronchial epithelial (BEAS-2B) and murine myeloid (RAW 264.7) cells, over a concentration range of 0.39-100 mg L(-1) and exposure time up to 24 h, for twenty-four different metal oxide NPs. Various nano-SAR building models were evaluated, based on an initial pool of thirty NP descriptors. The conduction band energy and ionic index (often correlated with the hydration enthalpy) were identified as suitable NP descriptors that are consistent with suggested toxicity mechanisms for metal oxide NPs and metal ions. The best performing nano-SAR with the above two descriptors, built with support vector machine (SVM) model and of validated robustness, had a balanced classification accuracy of ~94%. An applicability domain for the present data was established with a reasonable confidence level of 80%. Given the potential role of nano-SARs in decision making, regarding the environmental impact of NPs, the class probabilities provided by the SVM nano-SAR enabled the construction of decision boundaries with respect to toxicity classification under different acceptance levels of false negative relative to false positive predictions.

Quantifying and imaging engineered nanomaterials in vivo: challenges and techniques

Quantifying and imaging the engineered nanomaterials (ENMs) in vivo can provide information on the bio-distribution and fate of ENMs in living systems. A necessary amount of in vivo quantitative data is indispensable to verify the extrapolation from in vitro tests, to modify the predictive models of ENM exposure, and to underpin the risk management strategy for ENMs. However, it remains a challenge to quantitatively assess the bio-distribution of ENMs under realistic exposure, their long-term deposition (especially in non-targeted tissues), their passage across the natural barriers, and the impacts of nano-bio interactions on their in vivo behaviors. Some commonly used techniques for in vivo ENM quantification, such as electron microscopy, fluorescence-based detection, atomic spectroscopy, radiotracing, and techniques basing on synchrotron radiation are reviewed, and their technical characteristics, the state of the art, limitations, and future prospects are addressed.

Polyoxometalate-stabilized, water dispersible Fe₂Pt magnetic nanoparticles

Magnetic Fe2Pt core-shell nanoparticles with 2 nm cores were synthesized with a monolayer coating of silicotungstate Keggin clusters. The core-shell composition is substantiated by structural analysis performed using high-resolution scanning transmission electron microscopy (HR-STEM) and small angle X-ray scattering (SAXS) in a liquid suspension. The molecular metal oxide cluster shell introduces an enhanced dispersibility of the magnetic Fe-Pt core-shell nanoparticles in aqueous media and thereby opens up new routes to nanoparticle bio-functionalization, for example, using pre-functionalized polyoxometalates.

Characterization of physicochemical properties of ivy nanoparticles for cosmetic application

Background

Naturally occurring nanoparticles isolated from English ivy (Hedera helix) have previously been proposed as an alternative to metallic nanoparticles as sunscreen fillers due to their effective UV extinction property, low toxicity and potential biodegradability.

Methods

This study focused on analyzing the physicochemical properties of the ivy nanoparticles, specifically, those parameters which are crucial for use as sunscreen fillers, such as pH, temperature, and UV irradiation. The visual transparency and cytotoxicity of ivy nanoparticles were also investigated comparing them with other metal oxide nanoparticles.

Results

Results from this study demonstrated that, after treatment at 100°C, there was a clear increase in the UV extinction spectra of the ivy nanoparticles caused by the partial decomposition. In addition, the UVA extinction spectra of the ivy nanoparticles gradually reduced slightly with the decrease of pH values in solvents. Prolonged UV irradiation indicated that the influence of UV light on the stability of the ivy nanoparticle was limited and time-independent. Compared to TiO₂ and ZnO nanoparticles, ivy nanoparticles showed better visual transparency. Methylthiazol tetrazolium assay demonstrated that ivy nanoparticles exhibited lower cytotoxicity than the other two types of nanoparticles. Results also suggested that protein played an important role in modulating the three-dimensional structure of the ivy nanoparticles.

Conclusions

Based on the results from this study it can be concluded that the ivy nanoparticles are able to maintain their UV protective capability at wide range of temperature and pH values, further demonstrating their potential as an alternative to replace currently available metal oxide nanoparticles in sunscreen applications.

Sulfidation of silver nanoparticles: natural antidote to their toxicity

Nanomaterials are highly dynamic in biological and environmental media. A critical need for advancing environmental health and safety research for nanomaterials is to identify physical and chemical transformations that affect the nanomaterial properties and their toxicity. Silver nanoparticles, one of the most toxic and well-studied nanomaterials, readily react with sulfide to form Ag(0)/Ag2S core-shell particles. Here, we show that sulfidation decreased silver nanoparticle toxicity to four diverse types of aquatic and terrestrial eukaryotic organisms (Danio rerio (zebrafish), Fundulus heteroclitus (killifish), Caenorhabditis elegans (nematode worm), and the aquatic plant Lemna minuta (least duckweed)). Toxicity reduction, which was dramatic in killifish and duckweed even for low extents of sulfidation (about 2 mol % S), is primarily associated with a decrease in Ag(+) concentration after sulfidation due to the lower solubility of Ag2S relative to elemental Ag (Ag(0)). These results suggest that even partial sulfidation of AgNP will decrease the toxicity of AgNPs relative to their pristine counterparts. We also show that, for a given organism, the presence of chloride in the exposure media strongly affects the toxicity results by affecting Ag speciation. These results highlight the need to consider environmental transformations of NPs in assessing their toxicity to accurately portray their potential environmental risks.

Size influences the cytotoxicity of poly (lactic-co-glycolic acid) (PLGA) and titanium dioxide (TiO(2)) nanoparticles

The aim of this study is to uncover the size influence of poly (lactic-co-glycolic acid) (PLGA) and titanium dioxide (TiO(2)) nanoparticles on their potential cytotoxicity. PLGA and TiO(2) nanoparticles of three different sizes were thoroughly characterized before in vitro cytotoxic tests which included viability, generation of reactive oxygen species (ROS), mitochondrial depolarization, integrity of plasma membrane, intracellular calcium influx and cytokine release. Size-dependent cytotoxic effect was observed in both RAW264.7 cells and BEAS-2B cells after cells were incubated with PLGA or TiO(2) nanoparticles for 24 h. Although PLGA nanoparticles did not trigger significantly lethal toxicity up to a concentration of 300 μg/ml, the TNF-α release after the stimulation of PLGA nanoparticles should not be ignored especially in clinical applications. Relatively more toxic TiO(2) nanoparticles triggered cell death, ROS generation, mitochondrial depolarization, plasma membrane damage, intracellular calcium concentration increase and size-dependent TNF-α release, especially at a concentration higher than 100 μg/ml. These cytotoxic effects could be due to the size-dependent interaction between nanoparticles and biomolecules, as smaller particles tend to adsorb more biomolecules. In summary, we demonstrated that the ability of protein adsorption could be an important paradigm to predict the in vitro cytotoxicity of nanoparticles, especially for low toxic nanomaterials such as PLGA and TiO(2) nanoparticles.

Titanium dioxide nanoparticles activate the ATM-Chk2 DNA damage response in human dermal fibroblasts

The use of nanoparticles in consumer products increases their prevalence in the environment and the potential risk to human health. Although recent studies have shown in vivo and in vitro toxicity of titanium dioxide nanoparticles (nano-TiO2), a more detailed view of the underlying mechanisms of this response needs to be established. Here, the effects of nano-TiO2 on the DNA damage response and DNA replication dynamics were investigated in human dermal fibroblasts. Specifically, the relationship between nano-TiO2 and the DNA damage response pathways regulated by ATM/Chk2 and ATR/Chk1 was examined. The results show increased phosphorylation of H2AX, ATM, and Chk2 after exposure. In addition, nano-TiO2 inhibited the overall rate of DNA synthesis and frequency of replicon initiation events in DNA-combed fibres. Taken together, these results demonstrate that exposure to nano-TiO2 activates the ATM/Chk2 DNA damage response pathway.

Size of TiO(2) nanoparticles influences their phototoxicity: an in vitro investigation

To uncover the size influence of TiO(2) nanoparticles on their potential toxicity, the cytotoxicity of different-sized TiO(2) nanoparticles with and without photoactivation was tested. It was demonstrated that without photoactivation, TiO(2) nanoparticles were inert up to 100 μg/ml. On the contrary, with photoactivation, the toxicity of TiO(2) nanoparticles significantly increased, which correlated well with the specific surface area of the particles. Our results also suggest that the generation of hydroxyl radicals and reactive oxygen species (ROS)-mediated damage to the surface-adsorbed biomolecules could be the two major reasons for the cytotoxicity of TiO(2) nanoparticles after photoactivation. Higher ROS generation from smaller particles was detected under both biotic and abiotic conditions. Smaller particles could adsorb more proteins, which was confirmed by thermogravimetric analysis. To further investigate the influence of the generation of hydroxyl radicals and adsorption of protein, poly (ethylene-alt-maleic anhydride) (PEMA) and chitosan were used to coat TiO(2) nanoparticles. The results confirmed that surface coating of TiO(2) nanoparticles could reduce such toxicity after photoactivation, by hindering adsorption of biomolecules and generation of hydroxyl radical (·OH) during photoactivation.

Quantitative characterization of nanoparticles in blood by transmission electron microscopy with a window-type microchip nanopipet

Transmission electron microscopy (TEM) is a unique and powerful tool for observation of nanoparticles. However, due to the uneven spatial distribution of particles conventionally dried on copper grids, TEM is rarely employed to evaluate the spatial distribution of nanoparticles in aqueous solutions. Here, we present a microchip nanopipet with a narrow chamber width for sorting nanoparticles from blood and preventing the aggregation of the particles during the drying process, enabling quantitative analysis of their aggregation/agglomeration states and the particle concentration in aqueous solutions. This microchip is adaptable to all commercial TEM holders. Such a nanopipet proves to be a simple and convenient sampling device for TEM image-based quantitative characterization.