In vitro cytotoxicity of oxide nanoparticles: comparison to asbestos, silica, and the effect of particle solubility

Cellular internalization of silver nanoparticles in gut epithelia of the estuarine polychaete Nereis diversicolor

Silver nanoparticles (AgNPs) are widely used which may result in environmental impacts, notably within aquatic ecosystems. As estuarine sediments are sinks for numerous pollutants, but also habitat and food for deposit feeders such as Nereis diversicolor, ingested sediments must be investigated as an important route of uptake for NPs. N. diversicolor were fed sediment spiked with either citrate capped AgNPs (30 ± 5 nm) or aqueous Ag for 10 days. Postexposure AgNPs were observed in the lumen of exposed animals, and three lines of evidence indicated direct internalization of AgNPs into the gut epithelium. With TEM, electron-dense particles resembling AgNPs were observed associated with the apical plasma membrane, in endocytotic pits and in endosomes. Energy dispersive X-ray analysis (EDX) confirmed the presence of Ag in these particles, which were absent in controls. Subcellular fractionation revealed that Ag accumulated from AgNPs was predominantly associated with inorganic granules, organelles, and the heat denatured proteins; whereas dissolved Ag was localized to the metallothionein fraction. Collectively, these results indicate separate routes of cellular internalization and differing in vivo fates of Ag delivered in dissolved and NP form. For AgNPs an endocytotic pathway appears to be a key route of cellular uptake.

Stöber Synthesis of Nitric Oxide-Releasing S-Nitrosothiol-Modified Silica Particles

We report the synthesis of S-nitrosothiol-modified silica particles capable of nitric oxide (NO) release. The thiol precursor modification to form S-nitrosothiol NO donors was introduced into the silica network via co-condensation of mercaptosilane and alkoxysilane precursors. Both the concentrations of reactants (i.e., water, ammonia, and silane) and the silane feed rate into the reaction proved important in the yield of monodisperse, spherical particles with tunable diameters ranging from 241-718 nm. Subsequent nitrosation resulted in NO storage approaching ~4.40 μmol NO mg(-1), as determined by total NO release. Behaving similar to low molecular weight S-nitrosothiol NO donors, the NO release from the macromolecular silica vehicles was influenced by light, temperature, and metal ions.

Impact of dietary gold nanoparticles in zebrafish at very low contamination pressure: the role of size, concentration and exposure time

The impact of a daily ration of food containing gold nanoparticles (AuNPs) of two sizes (12 and 50 nm) was investigated in the zebrafish Danio rerio at very low doses (from 36-106 ng gold/fish/day). AuNP exposure resulted in various dysfunctions at the sub cellular scale, and AuNP concentration in food, AuNP size and exposure duration modulated the observed adverse effects. Indeed, we showed alteration of genome composition using a RAPD-PCR genotoxicity test as the number of hybridization sites of the RAPD probes was significantly modified after AuNP exposure. Moreover, the expression of genes involved in DNA repair, detoxification processes, apoptosis, mitochondrial metabolism and oxidative stress was also modulated in response to AuNP contamination. Mitochondrial dysfunctions appeared in brain and muscle for both tested doses (40 and 100 ng gold/fish/day), but gold accumulation in fish tissues could only be observed in the case of the highest exposure dose.

Interaction of spherical silica nanoparticles with neuronal cells: size-dependent toxicity and perturbation of calcium homeostasis

The effects of Stöber silica nanoparticles on neuronal survival, proliferation, and on the underlying perturbations in calcium homeostasis are investigated on the well-differentiated neuronal cell line GT1-7. The responses to nanoparticles 50 and 200 nm in diameter are compared. The 50-nm silica affects neuronal survival/proliferation in a dose-dependent way, by stimulating apoptotic processes. In contrast, the 200-nm silica does not show any toxic effect even at relatively high concentrations (292 μg mL−1). To identify the mechanisms underlying these effects, the changes in intracellular calcium concentration elicited by acute and chronic administration of the two silica nanoparticles are analyzed. The 50-nm silica at toxic concentrations generates huge and long-lasting increases in intracellular calcium, whereas the 200-nm silica only induces transient signals of much lower amplitude. These findings provide the first evidence that silica nanoparticles can induce toxic effects on neuronal cells in a size-dependent way, and that these effects are related to the degree of perturbation of calcium homeostasis.

Multicomponent folate-targeted magnetoliposomes: design, characterization, and cellular uptake

Folate-targeted cationic magnetoliposomes (FTMLs) have been prepared with coencapsulated doxorubicin (DOX) and anionic superparamagnetic iron oxide (SPIO) nanoparticles (NPs) with 5 nm γ-Fe(2)O(3) cores and 16 nm hydrodynamic diameters. NP encapsulation (89%) was confirmed by cryogenic transmission electron microscopy (TEM), and the presence of the oppositely charged NPs did not cause liposome aggregation. The FTMLs had an average diameter of 174 ± 53 nm and existed as unilamellar and cup-shaped liposomes, which was attributed to dissimilar lipid packing parameters and the presence of PEG-lipids. A 3-fold increase in DOX release was achieved over 2 hours when the encapsulated SPIO NPs were heated by an alternating current electromagnetic field operating at radio frequencies (RF). Results with human cervical cancer cells (HeLa), which have been shown to exhibit high folate receptor (FR) expression, confirmed FTML surface binding and cellular uptake. In contrast, no uptake was observed for lower FR-expressing human breast carcinoma cells (ZR-75-1).

FROM THE CLINICAL EDITOR

This study discusses the design and cellular uptake of multifunctional folate-targeted cationic magnetoliposomes enabling doxorubicin delivery and SPIO labeling.

Size effects on adsorption of hematite nanoparticles on E. coli cells

Adsorption of engineered nanoparticles (NPs) onto bacterial cells is critical for quantifying nanobio interactions as well as toxicokinetic properties of NPs. The purpose of this work was to study adsorption of hematite (α-Fe(2)O(3)) NPs onto Escherichia coli cells and to determine the particle size effects on the adsorption kinetics. Adsorption of large NPs (76 and 98 nm) on cells reached equilibrium faster (within 30-40 min) than small NPs (approximately 60-90 min). The adsorption rates in mg Fe/(L · s) decreased in the order of 98 nm > 76 nm > 53 nm > 26 nm. However, adsorption rates expressed as the number of adsorbed hematite NPs per unit cell surface area in #/(m2 · s) were faster for small NPs than those for large NPs. To interpret the size effects on adsorption kinetics, the Extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory was combined with interfacial force boundary layer (IFBL) theory. The computed adsorption rates for different sizes had excellent agreement with the experimental data, and they explained that that faster kinetics for smaller NPs could be attributed to faster particle mobility and lower energy barriers in the total interaction energy. This study lays the groundwork for quantifying the kinetic behavior of NPs interacting with microbial cells, and the results provide insight into adsorption processes at the nanoscale.

Cytotoxicity and oxidative stress induced by different metallic nanoparticles on human kidney cells

Background

Some manufactured nanoparticles are metal-based and have a wide variety of applications in electronic, engineering and medicine. Until now, many studies have described the potential toxicity of NPs on pulmonary target, while little attention has been paid to kidney which is considered to be a secondary target organ. The objective of this study, on human renal culture cells, was to assess the toxicity profile of metallic nanoparticles (TiO₂, ZnO and CdS) usable in industrial production. Comparative studies were conducted, to identify whether particle properties impact cytotoxicity by altering the intracellular oxidative status.

Results

Nanoparticles were first characterized by size, surface charge, dispersion and solubility. Cytotoxicity of NPs was then evaluated in IP15 (glomerular mesangial) and HK-2 (epithelial proximal) cell lines. ZnO and CdS NPs significantly increased the cell mortality, in a dose-dependent manner. Cytotoxic effects were correlated with the physicochemical properties of NPs tested and the cell type used. Analysis of reactive oxygen species and intracellular levels of reduced and oxidized glutathione revealed that particles induced stress according to their composition, size and solubility. Protein involved in oxidative stress such as NF-κb was activated with ZnO and CdS nanoparticles. Such effects were not observed with TiO₂ nanoparticles.

Conclusion

On glomerular and tubular human renal cells, ZnO and CdS nanoparticles exerted cytotoxic effects that were correlated with metal composition, particle scale and metal solubility. ROS production and oxidative stress induction clearly indicated their nephrotoxic potential.

Nanomaterial interactions with and trafficking across the lung alveolar epithelial barrier: implications for health effects of air-pollution particles

Studies on the health effects of air-pollution particles suggest that injury may result from inhalation of airborne ultrafine particles (<100 nm in diameter). Engineered nanomaterials (<100 nm in at least one dimension) may also be harmful if inhaled. Nanomaterials deposited on the respiratory epithelial tract are thought to cross the air-blood barrier, especially via the expansive alveolar region, into the systemic circulation to reach end organs (e.g., myocardium, liver, pancreas, kidney, and spleen). Since ambient ultrafine particles are difficult to track, studies of defined engineered nanomaterials have been used to obtain valuable information on how nanomaterials interact with and traffic across the air-blood barrier of mammalian lungs. Since specific mechanistic information on how nanomaterials interact with the lung is difficult to obtain using in vivo or ex vivo lungs due to their complex anatomy, in vitro alveolar epithelial models have been of considerable value in determining nanomaterial-lung interactions. In this review, we provide information on mechanisms underlying lung alveolar epithelial injury caused by various nanomaterials and on nanomaterial trafficking across alveolar epithelium that may lead to end-organ injury.

Review: Do engineered nanoparticles pose a significant threat to the aquatic environment?

Nanotechnology is a rapidly growing industry of global economic importance, exploiting the novel characteristics of materials manufactured at the nanoscale. The properties of engineered nanoparticles (ENPs) that make them useful in a wide range of industrial applications, however, have led to concerns regarding their potential impact on human and environmental health. The aquatic environment is particularly at risk of exposure to ENPs, as it acts as a sink for most environmental contaminants. This paper critically evaluates what is currently known about sources and discharge of ENPs to the aquatic environment and how the physicochemical characteristics of ENPs affect their fate and behaviour and thus availability for uptake into aquatic organisms, and assesses reported toxicological effects. Having reviewed the ecotoxicological information, the conclusion is that whilst there are data indicating some nanoparticles have the potential to induce harm in exposed aquatic organisms, there is insufficient evidence for harm, for known/modelled environmental concentrations for almost all ENPs considered. This conclusion, however, must be balanced by the fact that there are significant gaps in our understanding on the fate and behaviour of ENPs in the aquatic environment. Greater confidence in the assessments on ENP impacts in aquatic systems to enable effective comparisons across studies urgently requires more standardised approaches for ENP hazard identification, and critically, more thorough characterisations on the exposed particles. There is also an urgent need for the advancement of tools and techniques that can accurately quantify and visualise uptake of nanoparticles into biological tissues.

Hazardous phytotoxic nature of cobalt and zinc oxide nanoparticles assessed using Allium cepa

The increasing use of nanotechnology requires the clarification of the behavior and the effects of nanoparticles (NPs) as they are released into the environment. This study was to investigate the phytotoxicity of cobalt and zinc oxide NPs using the roots of Allium cepa (onion bulbs) as an indicator organism. The effects of cobalt and zinc oxide NPs on the root elongation, root morphology, and cell morphology of a plant, as well as their adsorption potential, were determined through the hydroponic culturing of A. cepa. A. cepa roots were treated with dispersions of the cobalt and zinc oxide NPs having three different concentrations (5, 10, and 20 μg ml(-1)). With increasing concentrations of the NPs, the elongation of the roots was severely inhibited by both the cobalt and the zinc oxide NPs as compared to that in the control plant (untreated A. cepa roots). Massive adsorption of cobalt oxide NPs into the root system was responsible for the phytotoxicity. Zinc oxide NPs caused damage because of their severe accumulation in both the cellular and the chromosomal modules, thus signifying their highly hazardous phytotoxic nature.

The phagocytosis and toxicity of amorphous silica

BACKGROUND

Inhalation of crystalline silica is known to cause an inflammatory reaction and chronic exposure leads to lung fibrosis and can progress into the disease, silicosis. Cultured macrophages bind crystalline silica particles, phagocytose them, and rapidly undergo apoptotic and necrotic death. The mechanism by which particles are bound and internalized and the reason particles are toxic is unclear. Amorphous silica has been considered to be a less toxic form, but this view is controversial. We compared the uptake and toxicity of amorphous silica to crystalline silica.

METHODOLOGY/PRINCIPAL FINDINGS

Amorphous silica particles are phagocytosed by macrophage cells and a single internalized particle is capable of killing a cell. Fluorescent dextran is released from endo-lysosomes within two hours after silica treatment and Caspase-3 activation occurs within 4 hours. Interestingly, toxicity is specific to macrophage cell lines. Other cell types are resistant to silica particle toxicity even though they internalize the particles. The large and uniform size of the spherical, amorphous silica particles allowed us to monitor them during the uptake process. In mCherry-actin transfected macrophages, actin rings began to form 1-3 minutes after silica binding and the actin coat disassembled rapidly following particle internalization. Pre-loading cells with fluorescent dextran allowed us to visualize the fusion of phagosomes with endosomes during internalization. These markers provided two new ways to visualize and quantify particle internalization. At 37 °C the rate of amorphous silica internalization was very rapid regardless of particle coating. However, at room temperature, opsonized silica is internalized much faster than non-opsonized silica.

CONCLUSIONS/SIGNIFICANCE

Our results indicate that amorphous and crystalline silica are both phagocytosed and both toxic to mouse alveolar macrophage (MH-S) cells. The pathway leading to apoptosis appears to be similar in both cases. However, the result suggests a mechanistic difference between FcγRIIA receptor-mediated and non-opsonized silica particle phagocytosis.

Inflammatory and cytotoxic responses of an alveolar-capillary coculture model to silica nanoparticles: comparison with conventional monocultures

Background

To date silica nanoparticles (SNPs) play an important role in modern technology and nanomedicine. SNPs are present in various materials (tyres, electrical and thermal insulation material, photovoltaic facilities). They are also used in products that are directly exposed to humans such as cosmetics or toothpaste. For that reason it is of great concern to evaluate the possible hazards of these engineered particles for human health. Attention should primarily be focussed on SNP effects on biological barriers. Accidentally released SNP could, for example, encounter the alveolar-capillary barrier by inhalation. In this study we examined the inflammatory and cytotoxic responses of monodisperse amorphous silica nanoparticles (aSNPs) of 30 nm in size on an in vitro coculture model mimicking the alveolar-capillary barrier and compared these to conventional monocultures.

Methods

Thus, the epithelial cell line, H441, and the endothelial cell line, ISO-HAS-1, were used in monoculture and in coculture on opposite sides of a filter membrane. Cytotoxicity was evaluated by the MTS assay, detection of membrane integrity (LDH release), and TER (Transepithelial Electrical Resistance) measurement. Additionally, parameters of inflammation (sICAM-1, IL-6 and IL-8 release) and apoptosis markers were investigated.

Results

Regarding toxic effects (viability, membrane integrity, TER) the coculture model was less sensitive to apical aSNP exposure than the conventional monocultures of the appropriate cells. On the other hand, the in vitro coculture model responded with the release of inflammatory markers in a much more sensitive fashion than the conventional monoculture. At concentrations that were 10-100fold less than the toxic concentrations the apically exposed coculture showed a release of IL-6 and IL-8 to the basolateral side. This may mimic the early inflammatory events that take place in the pulmonary alveoli after aSNP inhalation. Furthermore, a number of apoptosis markers belonging to the intrinsic pathway were upregulated in the coculture following aSNP treatment. Analysis of the individual markers indicated that the cells suffered from DNA damage, hypoxia and ER-stress.

Conclusion

We present evidence that our in vitro coculture model of the alveolar-capillary barrier is clearly advantageous compared to conventional monocultures in evaluating the extent of damage caused by hazardous material encountering the principle biological barrier in the lower respiratory tract.

Nanosilver induces minimal lung toxicity or inflammation in a subacute murine inhalation model

Background

There is increasing interest in the environmental and health consequences of silver nanoparticles as the use of this material becomes widespread. Although human exposure to nanosilver is increasing, only a few studies address possible toxic effect of inhaled nanosilver. The objective of this study was to determine whether very small commercially available nanosilver induces pulmonary toxicity in mice following inhalation exposure.

Results

In this study, mice were exposed sub-acutely by inhalation to well-characterized nanosilver (3.3 mg/m³, 4 hours/day, 10 days, 5 ± 2 nm primary size). Toxicity was assessed by enumeration of total and differential cells, determination of total protein, lactate dehydrogenase activity and inflammatory cytokines in bronchoalveolar lavage fluid. Lungs were evaluated for histopathologic changes and the presence of silver. In contrast to published in vitro studies, minimal inflammatory response or toxicity was found following exposure to nanosilver in our in vivo study. The median retained dose of nanosilver in the lungs measured by inductively coupled plasma - optical emission spectroscopy (ICP-OES) was 31 μg/g lung (dry weight) immediately after the final exposure, 10 μg/g following exposure and a 3-wk rest period and zero in sham-exposed controls. Dissolution studies showed that nanosilver did not dissolve in solutions mimicking the intracellular or extracellular milieu.

Conclusions

Mice exposed to nanosilver showed minimal pulmonary inflammation or cytotoxicity following sub-acute exposures. However, longer term exposures with higher lung burdens of nanosilver are needed to ensure that there are no chronic effects and to evaluate possible translocation to other organs.

Comparative pulmonary toxicity of inhaled nickel nanoparticles; role of deposited dose and solubility

In this pilot study, we investigated which physicochemical properties of nickel hydroxide nanoparticles (nano-NH) were mainly responsible in inducing pulmonary toxicity. First, we studied the role of nickel ions solubilized from nano-NH by comparing the toxic effects of nano-NH to those of readily soluble nickel sulfate nanoparticles (nano-NS). Additionally, to test whether there was a non-specific stress response due to particle morphology, we compared the toxicity of nano-NH with that of carbon nanoparticles (nano-C) and titanium dioxide nanoparticles (nano-Ti), both of which had similar physical properties such as particle size and shape, to nano-NH. We exposed mice to each type of nanoparticles for 4?h via a whole-body inhalation system and examined oxidative stress and inflammatory responses in the lung. We also determined the lung burden and clearance of Ni following nano-NH and nano-NS exposures. The results showed that lung deposition of nano-NH was significantly greater than that of nano-NS and nano-NH appeared to have stronger inflammogenic potential than nano-NS even when lung Ni burden taken into consideration. This suggests that the toxicity of nano-NH is not driven solely by released Ni ions from deposited nano-NH particles. However, it is unlikely that the greater toxic potential of nano-NH is attributable to a generic stress response from any nanoparticle exposure, since nano-C and nano-Ti did not elicit toxic responses similar to those of nano-NH. These results indicate that the observed pulmonary toxicity by inhaled nano-NH were chemical-specific and deposited dose and solubility are key factors to understand toxicity induced by nano-NH.

Cytotoxic, genotoxic and pro-inflammatory effects of zinc oxide nanoparticles in human nasal mucosa cells in vitro

Despite increasing application of zinc oxide nanoparticles (ZnO-NPs) for industrial purposes, data about potential toxic properties is contradictory. The current study focused on the cyto- and genotoxicity of ZnO-NPs in comparison to ZnO powder in primary human nasal mucosa cells cultured in the air-liquid interface. Additionally, IL-8 secretion as a marker for pro-inflammatory effects was measured. Particle morphology and intracellular distribution were evaluated by transmission electron microscopy (TEM). ZnO-NPs were transferred into the cytoplasm in 10% of the cells, whereas an intranuclear distribution could only be observed in 1.5%. While no cyto- or genotoxicity could be seen for ZnO powder in the dimethylthiazolyl-diphenyl-tetrazolium-bromide (MTT) test, the trypan blue exclusion test, and the single-cell microgel electrophoresis (comet) assay, cytotoxic effects were shown at a ZnO-NP concentration of 50 μg/ml (P<0.01). A significant enhancement in DNA damage was observed starting from ZnO-NP concentrations of 10 μg/ml (P<0.05) in comparison to the control. IL-8 secretion into the basolateral culture medium was increased at ZnO-NP concentrations of 5 μg/ml (P<0.05), as shown by ELISA. Our data indicates cyto- and genotoxic properties as well as a pro-inflammatory potential of ZnO-NPs in nasal mucosa cells. Thus, caution should be taken concerning their industrial and dermatological application. Additionally, further investigation on repetitive NP exposure is needed to estimate the impact of repair mechanisms.

Rat mesothelioma cell proliferation requires p38δ mitogen activated protein kinase and C/EBP-α

Pleural malignant mesothelioma is a rare but deadly tumour mainly induced by asbestos inhalation. Despite the ban of asbestos in 1990 in 52 countries, mesothelioma cases still increase worldwide. In pleural mesothelioma, p38 mitogen activated protein kinases (MAPK) have been suggested to play a major role in carcinogenesis and aggressiveness of tumours. The aim of this study was to determine the role of the different four p38 MAPK isoforms and their effect on proliferation together with the underlying signalling pathways in a rat pleural mesothelioma cell line. Rat pleural mesothelioma cells were stimulated with platelet-derived growth factor (PDGF)-BB and/or transforming growth factor beta (TGF)-β. MAPK and transcription factor expression and activation was monitored in the cytosol and nucleus by immuno-blotting. Proliferation was determined by manual cell count and siRNAs were used to control MAPK and transcription factor expression and action. Only PDGF-BB, but not TGF-β1 induced proliferation via activated Erk1/2 and p38 MAPK. The p38α and δ isoforms were expressed in the cytosol, and upon activation p38δ translocated into the nucleus, while p38α remained in the cytosol. No other p38 isoform was expressed by rat mesothelioma cells. C/EBP-α was found in both the cytosol and the nucleus, while C/EBP-β was not expressed at all. PDGF-BB induced proliferation was suppressed by down-regulation of either Erk1/2, or p38δ MAPK, or C/EBP-α. Furthermore, TGF-β inhibited PDGF-BB induced proliferation by interruption of p38 MAPK signalling. From this rat model, we conclude that in pleural mesothelioma, p38δ in C/EBP-α mediate proliferation and thus may represent new targets in mesothelioma therapy.

Synthesis of isotopically modified ZnO nanoparticles and their potential as nanotoxicity tracers

Understanding the behavior of engineered nanoparticles in the environment and within organisms is perhaps the biggest obstacle to the safe development of nanotechnologies. Reliable tracing is a particular issue for nanoparticles such as ZnO, because Zn is an essential element and a common pollutant thus present at elevated background concentrations. We synthesized isotopically enriched (89.6%) with a rare isotope of Zn (67Zn) ZnO nanoparticles and measured the uptake of 67Zn by L. stagnalis exposed to diatoms amended with the particles. Stable isotope technique is sufficiently sensitive to determine the uptake of Zn at an exposure equivalent to lower concentration range (<15 μg g(-1)). Without a tracer, detection of newly accumulated Zn is significant at Zn exposure concentration only above 5000 μg g(-1) which represents some of the most contaminated Zn conditions. Only by using a tracer we can study Zn uptake at a range of environmentally realistic exposure conditions.

Toxicological Issues of Nanoparticles Employed in Photocatalysis

A huge amount of different nanomaterials is nowadays on the market used for various specific applications. Some nanomaterials such as TiO

Hence these materials are used for many applications, e.g., for self-cleaning and antibacterial coatings on different surfaces and for the purification of wastewater where the cleaning can be induced by simple exposure to sunlight. Because of the frequent use of these nanoparticles it is important to investigate the life cycles of these nanostructured materials as well as their environmental impact and their toxicity to animals and humans.

This review first gives a short overview about nanotechnology and nanotechnological products as well as about photocatalysis and semiconductors used in this field. We then discuss the need for a new technology named nanotoxicology and the problems occurring when investigating the toxic potential of nanomaterials as well as the life cycle of nanomaterials. Furthermore, we focus on the environmental impact of TiO

Zinc oxide nanoparticles in modern sunscreens: an analysis of potential exposure and hazard

Sunscreens containing metal oxide nanoparticles appear transparent on the skin and provide excellent protection against sunburn caused by UV radiation. While it is likely that nanoparticles remain on the surface of the skin of healthy adult humans, and thus are considered safe for use in sunscreens, there has been no comprehensive assessment of the impact on human health from exposure to the metal oxide nanoparticles destined for use in sunscreens, either in the workplace during the manufacturing process, in long-term use across a range of skin conditions, or upon release into the broader environment, either accidentally or consequent of normal sunscreen use. In this review, we focus on zinc oxide nanoparticles destined for use in modern sunscreens, and discuss the potential for human exposure and the health hazard at each stage of their manufacture and use. We highlight where there is a need for further research.

Metal-based nanoparticles and their toxicity assessment

Nanoparticles (NPs) can potentially cause adverse effects on organ, tissue, cellular, subcellular, and protein levels due to their unusual physicochemical properties (e.g., small size, high surface area to volume ratio, chemical composition, crystallinity, electronic properties, surface structure reactivity and functional groups, inorganic or organic coatings, solubility, shape, and aggregation behavior). Metal NPs, in particular, have received increasing interest due to their widespread medical, consumer, industrial, and military applications. However, as particle size decreases, some metal-based NPs are showing increased toxicity, even if the same material is relatively inert in its bulk form (e.g., Ag, Au, and Cu). NPs also interact with proteins and enzymes within mammalian cells and they can interfere with the antioxidant defense mechanism leading to reactive oxygen species generation, the initiation of an inflammatory response and perturbation and destruction of the mitochondria causing apoptosis or necrosis. As a result, there are many challenges to overcome before we can determine if the benefits outweigh the risks associated with NPs.

Analysis of antimicrobial silver nanoparticles synthesized by coastal strains of Escherichia coli and Aspergillus niger

The present study investigated the extracellular biosynthesis of antimicrobial silver nanoparticles by Escherichia coli AUCAS 112 and Aspergillus niger AUCAS 237 derived from coastal mangrove sediment of southeast India. Both microbial species were able to produce silver nanoparticles, as confirmed by X-ray diffraction spectrum. The nanoparticles synthesized were mostly spherical, ranging in size from 5 to 20 nm for E. coli and from 5 to 35 nm for A. niger, as evident by transmission electron microscopy. Fourier transform spectroscopy revealed prominent peaks corresponding to amides I and II, indicating the presence of a protein for stabilizing the nanoparticles. Electrophoretic analysis revealed the presence of a prominent protein band with a molecular mass of 45 kDa for E. coli and 70 kDa for A. niger. The silver nanoparticles inhibited certain clinical pathogens, with antibacterial activity being more distinct than antifungal activity. The antimicrobial activity of E. coli was more pronounced than that of A. niger and was enhanced with the addition of polyvinyl alcohol as a stabilizing agent. This work highlighted the possibility of using microbes of coastal origin for synthesis of antimicrobial silver nanoparticles.

Effect of sonication and serum proteins on copper release from copper nanoparticles and the toxicity towards lung epithelial cells

Abstract Different methodological settings can influence particle characteristics and toxicity in nanotoxicology. The aim of this study was to investigate how serum proteins and sonication of Cu nanoparticle suspensions influence the properties of the nanoparticles and toxicological responses on human lung epithelial cells. This was investigated by using methods for particle characterization (photon correlation spectroscopy and TEM) and Cu release (atomic absorption spectroscopy) in combination with assays for analyzing cell toxicity (MTT-, trypan blue- and Comet assay). The results showed that sonication of Cu nanoparticles caused decreased cell viability and increased Cu release compared to non-sonicated particles. Furthermore, serum in the cell medium resulted in less particle agglomeration and increased Cu release compared with medium without serum, but no clear difference in toxicity was detected. Few cells showed intracellular Cu nanoparticles due to fast release/dissolution processes of Cu. In conclusion; sonication can affect the toxicity of nanoparticles.

Zinc oxide nanoparticles for selective destruction of tumor cells and potential for drug delivery applications

IMPORTANCE OF THE FIELD

Metal oxide nanoparticles, including zinc oxide, are versatile platforms for biomedical applications and therapeutic intervention. There is an urgent need to develop new classes of anticancer agents, and recent studies demonstrate that ZnO nanomaterials hold considerable promise.

AREAS COVERED IN THIS REVIEW

This review analyzes the biomedical applications of metal oxide and ZnO nanomaterials under development at the experimental, preclinical and clinical levels. A discussion regarding the advantages, approaches and limitations surrounding the use of metal oxide nanoparticles for cancer applications and drug delivery is presented. The scope of this article is focused on ZnO, and other metal oxide nanomaterial systems, and their proposed mechanisms of cytotoxic action, as well as current approaches to improve their targeting and cytotoxicity against cancer cells.

WHAT THE READER WILL GAIN

This review aims to give an overview of ZnO nanomaterials in biomedical applications.

TAKE HOME MESSAGE

Through a better understanding of the mechanisms of action and cellular consequences resulting from nanoparticles interactions with cells, the inherent toxicity and selectivity of ZnO nanoparticles against cancer may be improved further to make them attractive new anticancer agents.

Assessment of uptake and toxicity of fluorescent silica nanoparticles in zebrafish (Danio rerio) early life stages

In this study, we determined uptake and toxicity of fluorescent core-shell silica nanoparticles (FSNP) in early life stages of zebrafish. For this purpose fluorescent Ru@SiO2 nanoparticles with average size of ∼200 nm encapsulating [Ru(bpy)3](2+)Cl2 dye (excitation wavelength λ(exci)=488 nm), and Cy5.5@SiO2 with average size of ∼60 nm (λ(exci)=700 nm) were synthesized. The FSNP were highly luminescent. Field emission SEM analysis showed monodispersed dual-shell Ru@SiO2 nanoparticles of ∼200 nm size. Zebrafish embryos were exposed less than 6h post-fertilization (hpf) to the ∼60 and ∼200 nm FSNP at concentrations between 0.0025 and 200mg/L in 24-well plates for up to 96 hpf. The concentrations were analysed using an Fourier transform infra-red (FTIR) technique. Uptake of FSNP by embryos was monitored using transmission and confocal fluorescence microscopy. Toxicity was assessed by mortality, hatching time and success, and by morphological alterations. The ∼60 and ∼200 nm-sized FSNP and/or aggregates were adsorbed on the chorion of eggs. Uptake and translocation in embryos was not observed, but nanoparticle uptake not detectable by confocal microscopy may have occurred. Hatching time and hatching success were not affected. No mortality or deformities occurred. These nanoparticles and/or aggregates mainly accumulate on the chorion of embryos and exhibit no overt embryotoxicity.

Role of the dissolved zinc ion and reactive oxygen species in cytotoxicity of ZnO nanoparticles

With large-scale production and wide application of nanoscale ZnO, its health hazard has attracted extensive worldwide attention. In this study, cytotoxicity of different sized and shaped ZnO nanoparticles in mouse macrophage Ana-1 was investigated. And contribution of dissolved Zn(2+) and ROS in toxicity of ZnO particles was analyzed. The results indicated that ZnO particles manifested dose-dependent toxic effect on Ana-1 cells without size-dependence, and the particles shape may impact cytotoxicity of ZnO particles. When the concentration of dissolved Zn(2+) tended to equilibrium in the complete cell medium, the zinc ion concentration was approximately 10 μg/ml, inducing about 50% cell death, which was close to the cytotoxicity of ZnCl(2) (IC(50)=13.33 μg Zn/ml). The Zn(2+) concentration had significant correlations with cell viability and LDH level induced by the supernatant of ZnO particle suspensions (incubation at 37°C for 24h). Thus, the dissolved Zn(2+) played the main role in toxic effect of ZnO particles. Moreover, ROS generation assays demonstrated that ZnO particles produced intrinsically a small quantity of ROS, intracellular ROS was mainly produced after ZnO particles or the dissolved Zn(2+) entered into the cells. Although intracellular ROS had significant correlations with cell viability and LDH induced by ZnO particles, intracellular ROS may not be a major factor in cytotoxicity of ZnO nanoparticles, but the cytotoxic response.

Genotoxicity and cytotoxicity of zinc oxide and titanium dioxide in HEp-2 cells

Aims: The rapidly growing industrial and medical use of nanomaterials, especially zinc oxide and titanium dioxide, has led to growing concerns about their toxicity. Accordingly, the intrinsic genotoxic and cytotoxic potential of these nanoparticles have been evaluated. Materials & methods: Using a HEp-2 cell line, cytotoxicity was tested along with mitochondrial activity and neutral red uptake assays. The genotoxic potential was determined using the Comet and the cytokinesis-blocked micronucleus assays. In addition, tyrosine phosphorylation events were investigated. Results & conclusion: We found concentration- and time-dependent cytotoxicity and an increase in DNA and cytogenetic damage with increasing nanoparticle concentrations. Mainly for zinc oxide, genotoxicity was clearly associated with an increase in tyrosine phosphorylation. Our results suggest that both types of nanoparticles can be genotoxic over a range of concentrations without being cytotoxic.

Hard shell gas-filled contrast enhancement particles for colour Doppler ultrasound imaging of tumors

Hollow hard shell particles of 200 nm and 2 micron diameter with a 10 nm thick porous silica shell have been synthesized using polystyrene templates and a sol-gel process. The template ensures than the hollow particles are monodispersed, while the charged silica surface ensures that they remain suspended in solution for weeks. When filled with perfluorocarbon gas, the particles behave as an efficient contrast agent for colour Doppler ultrasound imaging in human breast tissue. The silica shell provides unique properties compared to conventional soft shell particles employed as ultrasound contrast agents: uniform size control, strong adsorption to tissue and cells immobilizing particles at the tissue injection site, a long imaging lifetime, and a silica surface that can be easily modified with biotargeting ligands or small molecules to adjust the surface charge and polarity.

Assessing iron oxide nanoparticle toxicity in vitro: current status and future prospects

The in vitro labeling of stem or therapeutic cells with engineered nanoparticles with the aim of transplanting these cells into live animals and, for example, noninvasively monitoring their migration, is a hot topic in nanomedicine research. It is of crucial importance that cell–nanoparticle interactions are studied in depth in order to exclude any negative effects of the cell labeling procedure. To date, many disparate results can be found in the literature regarding nanoparticle toxicity due to the great versatility of different parameters investigated. In the present work, an overview is presented of different types of nanomaterials, focusing mostly on iron oxide nanoparticles, developed for biomedical research. The difficulties in assessing nanoparticle-mediated toxicity are discussed, an overview of some of the problems encountered using commercial (dextran-coated) iron oxide nanoparticles is presented, several key parameters are highlighted and novel methods suggested – emphasizing the importance of intracellular nanoparticle degradation and linking toxicity data to functional (i.e., cell-associated) nanoparticle levels, which could help to advance any progress in this highly important research topic.

Potential toxicity of superparamagnetic iron oxide nanoparticles (SPION)

Superparamagnetic iron oxide nanoparticles (SPION) are being widely used for various biomedical applications, for example, magnetic resonance imaging, targeted delivery of drugs or genes, and in hyperthermia. Although, the potential benefits of SPION are considerable, there is a distinct need to identify any potential cellular damage associated with these nanoparticles. Besides focussing on cytotoxicity, the most commonly used determinant of toxicity as a result of exposure to SPION, this review also mentions the importance of studying the subtle cellular alterations in the form of DNA damage and oxidative stress. We review current studies and discuss how SPION, with or without different surface coating, may cause cellular perturbations including modulation of actin cytoskeleton, alteration in gene expression profiles, disturbance in iron homeostasis and altered cellular responses such as activation of signalling pathways and impairment of cell cycle regulation. The importance of protein-SPION interaction and various safety considerations relating to SPION exposure are also addressed.

Nitric oxide-releasing silica nanoparticle inhibition of ovarian cancer cell growth

Although the potent antitumor activity of nitric oxide (NO) supports its promise as an antineoplastic agent, effective and selective delivery and action on tumor and not normal cells remains a limiting factor. Nanoparticle-based delivery of NO has been considered as one approach to overcome these limitations. Therefore, we determined the utility of NO delivery using silica nanoparticles and evaluated their antitumor efficacy against human ovarian tumor and nontumor cells. The NO-releasing nanoparticles exhibited enhanced growth inhibition of ovarian tumor cells when compared to both control nanoparticles and a previously reported small molecule NO donor, PYRRO/NO. In addition, the NO-releasing nanoparticles showed greater inhibition of the anchorage-independent growth of tumor-derived and Ras-transformed ovarian cells. Confocal microscopy analysis revealed that fluorescently labeled NO-releasing nanoparticles entered the cytosol of the cell and localized to late endosomes and lysosomes. Furthermore, we observed a nanoparticle size dependency on efficacy against normal versus transformed ovarian cells. Our study provides the first application of nanoparticle-derived NO as an antitumor therapy and merits future studies examining nanoparticle formulation for in vivo applications.