In vitro toxicity of nanoparticles in BRL 3A rat liver cells

This study was undertaken to address the current deficient knowledge of cellular response to nanosized particle exposure. The study evaluated the acute toxic effects of metal/metal oxide nanoparticles proposed for future use in industrial production methods using the in vitro rat liver derived cell line (BRL 3A). Different sizes of nanoparticles such as silver (Ag; 15, 100 nm), molybdenum (MoO(3); 30, 150 nm), aluminum (Al; 30, 103 nm), iron oxide (Fe(3)O(4); 30, 47 nm), and titanium dioxide (TiO(2); 40 nm) were evaluated for their potential toxicity. We also assessed the toxicity of relatively larger particles of cadmium oxide (CdO; 1 microm), manganese oxide (MnO(2); 1-2 microm), and tungsten (W; 27 microm), to compare the cellular toxic responses with respect to the different sizes of nanoparticles with different core chemical compositions. For toxicity evaluations, cellular morphology, mitochondrial function (MTT assay), membrane leakage of lactate dehydrogenase (LDH assay), reduced glutathione (GSH) levels, reactive oxygen species (ROS), and mitochondrial membrane potential (MMP) were assessed under control and exposed conditions (24h of exposure). Results showed that mitochondrial function decreased significantly in cells exposed to Ag nanoparticles at 5-50 microg/ml. However, Fe(3)O(4), Al, MoO(3) and TiO(2) had no measurable effect at lower doses (10-50 microg/ml), while there was a significant effect at higher levels (100-250 microg/ml). LDH leakage significantly increased in cells exposed to Ag nanoparticles (10-50 microg/ml), while the other nanoparticles tested displayed LDH leakage only at higher doses (100-250 microg/ml). In summary the Ag was highly toxic whereas, MoO(3) moderately toxic and Fe(3)O(4), Al, MnO(2) and W displayed less or no toxicity at the doses tested. The microscopic studies demonstrated that nanoparticle-exposed cells at higher doses became abnormal in size, displaying cellular shrinkage, and an acquisition of an irregular shape. Due to toxicity of silver, further study conducted with reference to its oxidative stress. The results exhibited significant depletion of GSH level, reduced mitochondrial membrane potential and increase in ROS levels, which suggested that cytotoxicity of Ag (15, 100 nm) in liver cells is likely to be mediated through oxidative stress.

In vitro cytotoxicity of nanoparticles in mammalian germline stem cells

Gametogenesis is a complex biological process that is particularly sensitive to environmental insults such as chemicals. Many chemicals have a negative impact on the germline, either by directly affecting the germ cells, or indirectly through their action on the somatic nursing cells. Ultimately, these effects can inhibit fertility, and they may have negative consequences for the development of the offspring. Recently, nanomaterials such as nanotubes, nanowires, fullerene derivatives (buckyballs), and quantum dots have received enormous national attention in the creation of new types of analytical tools for biotechnology and the life sciences. Despite the wide application of nanomaterials, there is a serious lack of information concerning their impact on human health and the environment. Thus, there are limited studies available on toxicity of nanoparticles for risk assessment of nanomaterials. The purpose of this study was to assess the suitability of a mouse spermatogonial stem cell line as a model to assess nanotoxicity in the male germline in vitro. The effects of different types of nanoparticles on these cells were evaluated by light microscopy, and by cell proliferation and standard cytotoxicity assays. Our results demonstrate a concentration-dependent toxicity for all types of particles tested, whereas the corresponding soluble salts had no significant effect. Silver nanoparticles were the most toxic while molybdenum trioxide (MoO(3)) nanoparticles were the least toxic. Our results suggest that this cell line provides a valuable model with which to assess the cytotoxicity of nanoparticles in the germ line in vitro.

Using nano-QSAR to predict the cytotoxicity of metal oxide nanoparticles

It is expected that the number and variety of engineered nanoparticles will increase rapidly over the next few years, and there is a need for new methods to quickly test the potential toxicity of these materials. Because experimental evaluation of the safety of chemicals is expensive and time-consuming, computational methods have been found to be efficient alternatives for predicting the potential toxicity and environmental impact of new nanomaterials before mass production. Here, we show that the quantitative structure-activity relationship (QSAR) method commonly used to predict the physicochemical properties of chemical compounds can be applied to predict the toxicity of various metal oxides. Based on experimental testing, we have developed a model to describe the cytotoxicity of 17 different types of metal oxide nanoparticles to bacteria Escherichia coli. The model reliably predicts the toxicity of all considered compounds, and the methodology is expected to provide guidance for the future design of safe nanomaterials.

Toxicity of metal oxide nanoparticles in mammalian cells

Along with existing and emerging use of nanoscale materials, growing concerns have arisen about their unintentional health and environmental impact. The objective of the ongoing study was to assess the toxicity profile of metal oxide nanoparticles proposed for use in industrial production methodology. Metal oxide nanoparticles used in this study included TiO2, ZnO, Fe3O4, Al2O3, and CrO3 with particle sizes ranging from 30 to 45 nm. Cellular morphology, mitochondrial function, membrane leakage of lactate dehydrogenase (LDH), permeability of plasma membrane, and apoptosis were assessed under controlled and exposed conditions (2 to 72 h of exposure). The microscopic studies demonstrated that nanoparticle-exposed Neuro-2A cells (especially ZnO) at doses >100 microg/mL became abnormal in size, displaying cellular shrinkage, and detachment from the surface of flasks. Mitochondrial function decreased significantly in the cells exposed to ZnO at 50 to 100 microg/mL. However, Fe3O4, Al2O3, and TiO2 had no measurable effect on the cells until the concentrations reached greater than 200 microg/mL. LDH leakage significantly increased in the cells exposed to ZnO (50 to 100 microg/mL), while other nanoparticles tested displayed LDH leakage only at higher doses (>200 microg/mL). Flow cytometer tests showed that apoptosis took place in cells exposed to ZnO nanoparticles. More cells became necrotic as the concentrations increased.

Characterization of biophysical and metabolic properties of cells labeled with superparamagnetic iron oxide nanoparticles and transfection agent for cellular MR imaging

PURPOSE

To evaluate the effect of using the ferumoxides-poly-l-lysine (PLL) complex for magnetic cell labeling on the long-term viability, function, metabolism, and iron utilization of mammalian cells.

MATERIALS AND METHODS

PLL was incubated with ferumoxides for 60 minutes, incompletely coating the superparamagnetic iron oxide (SPIO) through electrostatic interactions. Cells were coincubated overnight with the ferumoxides-PLL complex, and iron uptake, cell viability, apoptosis indexes, and reactive oxygen species formation were evaluated. The disappearance or the life span of the detectable iron nanoparticles in cells was also evaluated. The iron concentrations in the media also were assessed at different time points. Data were expressed as the mean +/- 1 SD, and one-way analysis of variance and the unpaired Student t test were used to test for significant differences.

RESULTS

Intracytoplasmic nanoparticles were stained with Prussian blue when the ferumoxides-PLL complex had magnetically labeled the human mesenchymal stem and HeLa cells. The long-term viability, growth rate, and apoptotic indexes of the labeled cells were unaffected by the endosomal incorporation of SPIO, as compared with these characteristics of the nonlabeled cells. In nondividing human mesenchymal stem cells, endosomal iron nanoparticles could be detected after 7 weeks; however, in rapidly dividing cells, intracellular iron had disappeared by five to eight divisions. A nonsignificant transient increase in reactive oxygen species production was seen in the human mesenchymal stem and HeLa cell lines. Labeled human mesenchymal stem cells did not differentiate to other lineage. A significant increase in iron concentration was observed in both the human mesenchymal stem and HeLa cell media at day 7.

CONCLUSION

Magnetic cellular labeling with the ferumoxides-PLL complex had no short- or long-term toxic effects on tumor or stem cells.

Efficient magnetic cell labeling with protamine sulfate complexed to ferumoxides for cellular MRI

Recently, there have been several reports using various superparamagnetic iron oxide (SPIO) nanoparticles to label mammalian cells for monitoring their temporal and spatial migration in vivo by magnetic resonance imaging (MRI). The purpose of this study was to evaluate the efficiency and toxicity of labeling cells using 2 commercially available Food and Drug Administration (FDA)-approved agents, ferumoxides, a suspension of dextran-coated SPIO used as an MRI contrast agent, and protamine sulfate, conventionally used to reverse heparin anticoagulation but also used ex vivo as a cationic transfection agent. After labeling of human mesenchymal stem cells (MSCs) and hematopoietic (CD34+) stem cells and other mammalian cells with ferumoxides-protamine sulfate complexes (FE-Pro), cellular toxicity, functional capacity, and quantitative cellular iron incorporation were determined. FE-Pro-labeled cells demonstrated no short- or long-term toxicity, changes in differentiation capacity of the stem cells, or changes in phenotype when compared with unlabeled cells. Efficient labeling with FE-Pro was observed with iron content per cell varying between 2.01 +/- 0.1 pg for CD34+ cells and 10.94 +/- 1.86 pg for MSCs with 100% of cells labeled. Cell labeling using these agents should facilitate the translation of this method to clinical trials for evaluation of trafficking of infused or transplanted cells by MRI.

Targeting thioredoxin reductase is a basis for cancer therapy by arsenic trioxide

Arsenic trioxide (ATO) is an effective cancer therapeutic drug for acute promyelocytic leukemia and has potential anticancer activity against a wide range of solid tumors. ATO exerts its effect mainly through elevated oxidative stress, but the exact molecular mechanism remains elusive. The thioredoxin (Trx) system comprising NADPH, thioredoxin reductase (TrxR), and Trx and the glutathione (GSH) system composed of NADPH, glutathione reductase, and GSH supported by glutaredoxin are the two electron donor systems that control cellular proliferation, viability, and apoptosis. Recently, the selenocysteine-dependent TrxR enzyme has emerged as an important molecular target for anticancer drug development. Here, we have discovered that ATO irreversibly inhibits mammalian TrxR with an IC(50) of 0.25 microM. Both the N-terminal redox-active dithiol and the C-terminal selenothiol-active site of reduced TrxR may participate in the reaction with ATO. The inhibition of MCF-7 cell growth by ATO was correlated with irreversible inactivation of TrxR, which subsequently led to Trx oxidation. Furthermore, the inhibition of TrxR by ATO was attenuated by GSH, and GSH depletion by buthionine sulfoximine enhanced ATO-induced cell death. These results strongly suggest that the ATO anticancer activity is by means of a Trx system-mediated apoptosis. Blocking cancer cell DNA replication and repair and induction of oxidative stress by the inhibition of both Trx and GSH systems are suggested as cancer chemotherapeutic strategies.

Microbial toxicity of metal oxide nanoparticles (CuO, NiO, ZnO, and Sb2O3) to Escherichia coli, Bacillus subtilis, and Streptococcus aureus

In this study, the microbial toxicities of metal oxide nanoparticles were evaluated for Escherichia coli, Bacillus subtilis, and Streptococcus aureus in laboratory experiments. The nanoparticles tested were CuO, NiO, ZnO, and Sb(2)O(3). The metal oxide nanoparticles were dispersed thoroughly in a culture medium, and the microorganisms were cultivated on Luria-Bertani agar plates containing different concentrations of metal oxide nanoparticles. The bacteria were counted in terms of colony forming units (CFU). The CFU was reduced in a culture medium containing metal oxide NP, and the dose-response relationship was characterized. CuO nanoparticles were found to be the most toxic among the tested nanoparticles, followed by ZnO (except S. aureus), NiO, and Sb(2)O(3) nanoparticles. We determined that the intrinsic toxic properties of heavy metals are also associated with the toxicity of metal oxide nanoparticles. Ion toxicity was also evaluated to determine the effects of metal ions dissolved from metal oxide NPs, and the toxicity induced from the dissolved ions was determined to be negligible herein. To the best of our knowledge, this is the first study of the toxicity of NiO and Sb(2)O(3) NPs on microorganisms. We also discuss the implications of our findings regarding the effects of the intrinsic toxic properties of heavy metals, and concluded that the apparent toxicities of metal oxide NPs can largely be understood as a matter of particle toxicity.

Size-, composition- and shape-dependent toxicological impact of metal oxide nanoparticles and carbon nanotubes toward bacteria

Ecotoxicological effects of nanoparticles (NP) are still poorly documented while their commercialization for industrial and household applications increases. The aim of this study was to evaluate the influence of physicochemical characteristics on metal oxide NP and carbon nanotubes toxicological effects toward bacteria. Two strains of bacteria, Cupriavidus metallidurans CH34 and Escherichia coli MG1655 were exposed to TiO(2) or Al(2)O(3) NP or to multiwalled-carbon nanotubes (MWCNT). Particular attention was paid on optimizing NP dispersion to obtain nonagglomerated suspensions. Our results show that NP toxicity depends on their chemical composition, size, surface charge, and shape but not on their crystalline phase. MWCNT toxicity does not depend on their purity. Toxicity also depends on the bacterial strain: E. coli MG1655 is sensitive to NP, whereas C. metallidurans CH34 is not. Interestingly, NP are accumulated in both bacterial strains, and association between NP and bacteria is necessary for bacterial death to occur. NP may then represent a danger for the environment, causing the disappearance of some sensitive bacterial strains such as E. coli MG1655, but also being mobilized by nonsensitive strains such as C. metallidurans CH34 and transported through the whole ecosystem.

Using mineral trioxide aggregate as a pulp-capping material

This study examined the dental pulp responses in monkeys to mineral trioxide aggregate, or MTA, and a calcium hydroxide preparation when used as pulp-capping materials. After the pulps of 12 mandibular incisors were exposed with a No. 1 round bur, they were capped with either MTA or the calcium hydroxide preparation. After five months, the authors noted no pulpal inflammation in five of six samples capped with MTA, and all six pulps in this group had a complete dentin bridge. In contrast, all of the pulps capped with the calcium hydroxide preparation showed pulpal inflammation, and bridge formation occurred in only two samples. Based on these results, it appears that MTA has the potential to be used as a pulp-capping material during vital pulp therapy.

Crucial Role of Lateral Size for Graphene Oxide in Activating Macrophages and Stimulating Pro-inflammatory Responses in Cells and Animals

Graphene oxide (GO) is increasingly used in biomedical applications because it possesses not only the unique properties of graphene including large surface area and flexibility but also hydrophilicity and dispersibility in aqueous solutions. However, there are conflicting results on its biocompatibility and biosafety partially due to large variations in physicochemical properties of GO, and the role of these properties including lateral size in the biological or toxicological effects of GO is still unclear. In this study, we focused on the role of lateral size by preparing a panel of GO samples with differential lateral sizes using the same starting material. We found that, in comparison to its smaller counterpart, larger GO showed a stronger adsorption onto the plasma membrane with less phagocytosis, which elicited more robust interaction with toll-like receptors and more potent activation of NF-κB pathways. By contrast, smaller GO sheets were more likely taken up by cells. As a result, larger GO promoted greater M1 polarization, associated with enhanced production of inflammatory cytokines and recruitment of immune cells. The in vitro results correlated well with local and systemic inflammatory responses after GO administration into the abdominal cavity, lung, or bloodstream through the tail vein. Together, our study delineated the size-dependent M1 induction of macrophages and pro-inflammatory responses of GO in vitro and in vivo. Our data also unearthed the detailed mechanism underlying these effects: a size-dependent interaction between GO and the plasma membrane.

The Interaction of Manganese Nanoparticles with PC-12 Cells Induces Dopamine Depletion

This investigation was designed to determine whether nano-sized manganese oxide (Mn-40 nm) particles would induce dopamine (DA) depletion in a cultured neuronal phenotype, PC-12 cells, similar to free ionic manganese (Mn(2+)). Cells were exposed to Mn-40 nm, Mn(2+) (acetate), or known cytotoxic silver nanoparticles (Ag-15 nm) for 24 h. Phase-contrast microscopy studies show that Mn-40 nm or Mn(2+) exposure did not greatly change morphology of PC-12 cells. However, Ag-15 nm and AgNO(3) produce cell shrinkage and irregular membrane borders compared to control cells. Further microscopic studies at higher resolution demonstrated that Mn-40 nm nanoparticles and agglomerates were effectively internalized by PC-12 cells. Mitochondrial reduction activity, a sensitive measure of particle and metal cytotoxicity, showed only moderate toxicity for Mn-40 nm compared to similar Ag-15 nm and Mn(2+) doses. Mn-40 nm and Mn(2+) dose dependently depleted DA and its metabolites, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), while Ag-15 nm only significantly reduced DA and DOPAC at concentrations of 50 mug/ml. Therefore, the DA depletion of Mn-40 nm was most similar to Mn(2+), which is known to induce concentration-dependent DA depletion. There was a significant increase (> 10-fold) in reactive oxygen species (ROS) with Mn-40 nm exposure, suggesting that increased ROS levels may participate in DA depletion. These results clearly demonstrate that nanoscale manganese can deplete DA, DOPAC, and HVA in a dose-dependent manner. Further study is required to evaluate the specific intracellular distribution of Mn-40 nm nanoparticles, metal dissolution rates in cells and cellular matrices, if DA depletion is induced in vivo, and the propensity of Mn nanoparticles to cross the blood-brain barrier or be selectively uptaken by nasal epithelium.

Improved In Vitro and In Vivo Biocompatibility of Graphene Oxide through Surface Modification: Poly(Acrylic Acid)-Functionalization is Superior to PEGylation

The unique physicochemical properties of two-dimensional (2D) graphene oxide (GO) could greatly benefit the biomedical field; however, recent research demonstrated that GO could induce in vitro and in vivo toxicity. We determined the mechanism of GO induced toxicity, and our in vitro experiments revealed that pristine GO could impair cell membrane integrity and functions including regulation of membrane- and cytoskeleton-associated genes, membrane permeability, fluidity and ion channels. Furthermore, GO induced platelet depletion, pro-inflammatory response and pathological changes of lung and liver in mice. To improve the biocompatibility of pristine GO, we prepared a series of GO derivatives including aminated GO (GO-NH2), poly(acrylamide)-functionalized GO (GO-PAM), poly(acrylic acid)-functionalized GO (GO-PAA) and poly(ethylene glycol)-functionalized GO (GO-PEG), and compared their toxicity with pristine GO in vitro and in vivo. Among these GO derivatives, GO-PEG and GO-PAA induced less toxicity than pristine GO, and GO-PAA was the most biocompatible one in vitro and in vivo. The differences in biocompatibility were due to the differential compositions of protein corona, especially immunoglobulin G (IgG), formed on their surfaces that determine their cell membrane interaction and cellular uptake, the extent of platelet depletion in blood, thrombus formation under short-term exposure and the pro-inflammatory effects under long-term exposure. Overall, our combined data delineated the key molecular mechanisms underlying the in vivo and in vitro biological behaviors and toxicity of pristine GO, and identified a safer GO derivative that could be used for future applications.

Testing metal-oxide nanomaterials for human safety

Nanomaterials can display distinct biological effects compared with bulk materials of the same chemical composition. The physico-chemical characterization of nanomaterials and their interaction with biological media are essential for reliable studies and are reviewed here with a focus on widely used metal oxide and carbon nanomaterials. Available rat inhalation and cell culture studies compared to original results suggest that hazard potential is not determined by a single physico-chemical property but instead depends on a combination of material properties. Reactive oxygen species generation, fiber shape, size, solubility and crystalline phase are known indicators of nanomaterials biological impact. According to these properties the summarized hazard potential decreases in the order multi-walled carbon nanotubes >> CeO(2), ZnO > TiO(2) > functionalized SiO(2) > SiO(2), ZrO(2), carbon black. Enhanced understanding of biophysical properties and cellular effects results in improved testing strategies and enables the selection and production of safe materials.

Mineral trioxide aggregate: a review of the constituents and biological properties of the material

This paper reviews the literature on the constituents and biocompatibility of mineral trioxide aggregate (MTA). A Medline search was conducted. The first publication on the material was in November 1993. The Medline search identified 206 papers published from November 1993 to August 2005. Specific searches on constituents and biocompatibility of mineral trioxide aggregate, however, yielded few publications. Initially all abstracts were read to identify which fitted one of the two categories required for this review, constituents or biocompatibility. Based on this assessment and a review of the papers, 13 were included in the constituent category and 53 in the biocompatibility category. Relatively few articles addressed the constituents of MTA, whilst cytological evaluation was the most widely used biocompatibility test.

Metal oxide nanoparticles induce unique inflammatory footprints in the lung: important implications for nanoparticle testing

BACKGROUND

Metal oxide nanoparticles (NPs) have been widely used in industry, cosmetics, and biomedicine.

OBJECTIVES

We examined hazards of several well-characterized high production volume NPs because of increasing concern about occupational exposure via inhalation.

METHODS

A panel of well-characterized NPs [cerium oxide (CeO₂NP), titanium dioxide (TiO₂NP), carbon black (CBNP), silicon dioxide (SiO₂NP), nickel oxide (NiONP), zinc oxide (ZnONP), copper oxide (CuONP), and amine-modified polystyrene beads] was instilled into lungs of rats. We evaluated the inflammation potencies of these NPs 24 hr and 4 weeks postinstillation. For NPs that caused significant inflammation at 24 hr, we then investigated the characteristics of the inflammation. All exposures were carried out at equal-surface-area doses.

RESULTS

Only CeO₂NP, NiONP, ZnONP, and CuONP were inflammogenic to the lungs of rats at the high doses used. Strikingly, each of these induced a unique inflammatory footprint both acutely (24 hr) and chronically (4 weeks). Acutely, patterns of neutrophil and eosinophil infiltrates differed after CeO₂NP, NiONP, ZnONP, and CuONP treatment. Chronic inflammatory responses also differed after 4 weeks, with neutrophilic, neutrophilic/lymphocytic, eosinophilic/fibrotic/granulomatous, and fibrotic/granulomatous inflammation being caused respectively by CeO₂NP, NiONP, ZnONP, and CuONP.

CONCLUSION

Different types of inflammation imply different hazards in terms of pathology, risks, and risk severity. In vitro testing could not have differentiated these complex hazard outcomes, and this has important implications for the global strategy for NP hazard assessment. Our results demonstrate that NPs cannot be viewed as a single hazard entity and that risk assessment should be performed separately and with caution for different NPs.

Preclinical safety and pharmacokinetic profile of ferumoxtran-10, an ultrasmall superparamagnetic iron oxide magnetic resonance contrast agent

OBJECTIVES

This report presents an overview of preclinical data available on ferumoxtran-10, an ultrasmall superparamagnetic iron oxide nanoparticular contrast agent proposed for lymph node magnetic resonance imaging.

MATERIALS AND METHODS

Pharmacokinetic, safety pharmacology, single- and repeat-dose toxicity, reproduction toxicity, and genotoxicity studies were performed with ferumoxtran-10 given intravenously (bolus injection) in mice, rats, rabbits, dogs, and monkeys.

RESULTS

Ferumoxtran-10 was taken up by macrophages, mostly in liver, spleen, and lymph nodes, within 24 hours after bolus injection and underwent progressive metabolism. Toxicity was observed only at very high exposure levels and mainly was linked to a massive iron load after repeated injections. Ferumoxtran-10 was not mutagenic but was teratogenic in rats and rabbits.

DISCUSSION

The preclinical pharmacokinetic and safety profile of ferumoxtran-10 appears to be satisfactory in view of its proposed use as a single-dose diagnostic agent in human for MR imaging of lymph nodes.

Biological interactions of carbon-based nanomaterials: From coronation to degradation

Carbon-based nanomaterials including carbon nanotubes, graphene oxide, fullerenes and nanodiamonds are potential candidates for various applications in medicine such as drug delivery and imaging. However, the successful translation of nanomaterials for biomedical applications is predicated on a detailed understanding of the biological interactions of these materials. Indeed, the potential impact of the so-called bio-corona of proteins, lipids, and other biomolecules on the fate of nanomaterials in the body should not be ignored. Enzymatic degradation of carbon-based nanomaterials by immune-competent cells serves as a special case of bio-corona interactions with important implications for the medical use of such nanomaterials. In the present review, we highlight emerging biomedical applications of carbon-based nanomaterials. We also discuss recent studies on nanomaterial 'coronation' and how this impacts on biodistribution and targeting along with studies on the enzymatic degradation of carbon-based nanomaterials, and the role of surface modification of nanomaterials for these biological interactions.

FROM THE CLINICAL EDITOR

Advances in technology have produced many carbon-based nanomaterials. These are increasingly being investigated for the use in diagnostics and therapeutics. Nonetheless, there remains a knowledge gap in terms of the understanding of the biological interactions of these materials. In this paper, the authors provided a comprehensive review on the recent biomedical applications and the interactions of various carbon-based nanomaterials.

Toxicity of metal oxide nanoparticles: mechanisms, characterization, and avoiding experimental artefacts

Metal oxide nanomaterials are widely used in practical applications and represent a class of nanomaterials with the highest global annual production. Many of those, such as TiO2 and ZnO, are generally considered non-toxic due to the lack of toxicity of the bulk material. However, these materials typically exhibit toxicity to bacteria and fungi, and there have been emerging concerns about their ecotoxicity effects. The understanding of the toxicity mechanisms is incomplete, with different studies often reporting contradictory results. The relationship between the material properties and toxicity appears to be complex and diifficult to understand, which is partly due to incomplete characterization of the nanomaterial, and possibly due to experimental artefacts in the characterization of the nanomaterial and/or its interactions with living organisms. This review discusses the comprehensive characterization of metal oxide nanomaterials and the mechanisms of their toxicity.

Ultrasmall superparamagnetic iron oxides (USPIOs): a future alternative magnetic resonance (MR) contrast agent for patients at risk for nephrogenic systemic fibrosis (NSF)?

Gadolinium (Gd) based contrast agents (GBCAs) in magnetic resonance imaging (MRI) are used in daily clinical practice and appear safe in most patients; however, nephrogenic systemic fibrosis (NSF) is a recently recognized severe complication associated with GBCAs. It affects primarily patients with renal disease, such as stage 4 or 5 chronic kidney disease (CKD; glomerular filtration rate <30 ml/min per 1.73 m(2)), acute kidney injury, or kidney and liver transplant recipients with kidney dysfunction. Contrast-enhanced MRI and computed tomography (CT) scans provide important clinical information and influence patient management. An alternative contrast agent is needed to obtain adequate imaging results while avoiding the risk of NSF in this vulnerable patient group. One potential alternative is ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, which provide enhancement characteristics similar to GBCAs. We review our experience in approximately 150 patients on the potential benefits of the USPIOs ferumoxtran-10 and ferumoxytol. We focus on central nervous system (CNS) MRI but also review imaging of other vascular beds. Safety studies, including USPIO administration (ferumoxytol) as iron supplement therapy in CKD patients on and not on dialysis, suggest that decreased kidney function does not alter the safety profile. We conclude that for both CNS MR imaging and MR angiography, USPIO agents like ferumoxytol are a viable option for patients at risk for NSF.

Cytotoxicity of four root end filling materials

Leakage and scanning electron microscopic studies have shown that a mineral trioxide aggregate (MTA) used as root end filling material permits significantly less leakage and has better adaptation than other commonly used root end filling materials. Because these materials are in contact with the periradicular tissues, their cytotoxicity should be evaluated before in vivo tests. Using the agar overlay and radiochromium methods, the cytotoxicity of amalgam, Super EBA, IRM, and the MTA was evaluated. Statistical analysis of the data from the agar overlay technique shows that freshly mixed and set amalgam were significantly less toxic than the rest of tested materials (p< 0.00005). Fresh and set MTA ranked second when tested for cytotoxicity with this technique. Similar statistical tests revealed a significant statistical difference between the toxicity of freshly mixed and set materials after 24 h of incubation with radiochromium-labeled mouse L929 cells. The degree of cytotoxicity of fresh and set materials was MTA least toxic followed by amalgam, Super EBA, and IRM. Based on the results of the cell culture methods used in this study it appears that MTA is a potential root end filling material and warrants further in vivo evaluations.

Where does the toxicity of metal oxide nanoparticles come from: The nanoparticles, the ions, or a combination of both?

The toxicity of metal oxide nanoparticles (NPs) has aroused great concern over the past few years. However, there still remains the question whether the toxicity of the metal oxide NPs originates from the released ions or the NPs themselves. In this study, the metal ion release of CuO, Fe2O3, ZnO, Co3O4, Cr2O3, and NiO NPs in aqueous media was investigated, and their contributions to the metal oxide NPs' inhibition on the bioluminescence of Photobacterium phosphoreum were studied. It was found that the ions release of the metal oxide NPs in aqueous media was complex, depending on both the dissolution and adsorption processes of the metal oxide NPs. The relationships between the metal oxide NPs' antibacterial effects and their released metal ions could be divided into three categories: (1) the ZnO NPs' antibacterial effect was due solely to the released Zn(2+); (2) the CuO NPs' antibacterial effect originated from both the released Cu(2+),and the CuO particles; and (3) the antibacterial effects of Fe2O3, Co3O4, Cr2O3, and NiO NPs were caused by the NPs themselves. Our findings suggest that the ions release and their contributions to the NPs' toxicity should be considered in the toxicity evaluations of the metal oxide NPs.

Efficacy of simple short-term in vitro assays for predicting the potential of metal oxide nanoparticles to cause pulmonary inflammation

BACKGROUND

There has been concern regarding risks from inhalation exposure to nanoparticles (NPs). The large number of particles requiring testing means that alternative approaches to animal testing are needed.

OBJECTIVES

We set out to determine whether short-term in vitro assays that assess intrinsic oxidative stress potential and membrane-damaging potency of a panel of metal oxide NPs can be used to predict their inflammogenic potency.

METHODS

For a panel of metal oxide NPs, we investigated intrinsic free radical generation, oxidative activity in an extracellular environment, cytotoxicity to lung epithelial cells, hemolysis, and inflammation potency in rat lungs. All exposures were carried out at equal surface area doses.

RESULTS

Only nickel oxide (NiO) and alumina 2 caused significant lung inflammation when instilled into rat lungs at equal surface area, suggesting that these two had extra surface reactivity. We observed significant free radical generation with 4 of 13 metal oxides, only one of which was inflammogenic. Only 3 of 13 were significantly hemolytic, two of which were inflammogenic.

CONCLUSIONS

Potency in generating free radicals in vitro did not predict inflammation, whereas alumina 2 had no free radical activity but was inflammogenic. The hemolysis assay was correct in predicting the proinflammatory potential of 12 of 13 of the particles examined. Using a battery of simple in vitro tests, it is possible to predict the inflammogenicity of metal oxide NPs, although some false-positive results are likely. More research using a larger panel is needed to confirm the efficacy and generality of this approach for metal oxide NPs.

Covalent functionalization of graphene oxide with biocompatible poly(ethylene glycol) for delivery of paclitaxel

Graphene oxide (GO), a novel 2D nanomaterial prepared by the oxidation of natural graphite, has been paid much attention in the area of drug delivery due to good biocompatibility and low toxicity. In the present work, 6-armed poly(ethylene glycol) was covalently introduced into the surface of GO sheets via a facile amidation process under mild conditions, making the modified GO, GO-PEG (PEG: 65 wt %, size: 50-200 nm), stable and biocompatible in physiological solution. This nanosized GO-PEG was found to be nontoxic to human lung cancer A549 and human breast cancer MCF-7 cells via cell viability assay. Furthermore, paclitaxel (PTX), a widely used cancer chemotherapy drug, was conjugated onto GO-PEG via π-π stacking and hydrophobic interactions to afford a nanocomplex of GO-PEG/PTX with a relatively high loading capacity for PTX (11.2 wt %). This complex could quickly enter into A549 and MCF-7 cells evidenced by inverted fluorescence microscopy using Fluorescein isothiocyanate as a probe, and it also showed remarkably high cytotoxicity to A549 and MCF-7 cells in a broad range of concentration of PTX and time compared to free PTX. This kind of nanoscale drug delivery system on the basis of PEGylated GO may find potential application in biomedicine.