Consumer exposures to laser printer-emitted engineered nanoparticles: A case study of life-cycle implications from nano-enabled products

Abstract

It is well established that printers emit nanoparticles during their operation. To-date, however, the physicochemical and toxicological characterization of “real world” printer-emitted nanoparticles (PEPs) remains incomplete, hampering proper risk assessment efforts. Here, we investigate our earlier hypothesis that engineered nanomaterials (ENMs) are used in toners and ENMs are released during printing (consumer use). Furthermore, we conduct a detailed physicochemical and morphological characterization of PEPs in support of ongoing toxicological assessment. A comprehensive suite of state of the art analytical methods and tools was employed for the physicochemical and morphological characterization of 11 toners widely utilized in printers from major printer manufacturers and their PEPs. We confirmed that a number of ENMs incorporated into toner formulations (e.g. silica, alumina, titania, iron oxide, zinc oxide, copper oxide, cerium oxide, carbon black among others) and released into the air during printing. All evaluated toners contained large amounts of organic carbon (OC, 42–89%), metals/metal oxides (1–33%), and some elemental carbon (EC, 0.33–12%). The PEPs possess a composition similar to that of toner and contained 50–90% OC, 0.001–0.5% EC and 1–3% metals. While the chemistry of the PEPs generally reflected that of their toners, considerable differences are documented indicative of potential transformations taking place during consumer use (printing). We conclude that: (i) Routine incorporation of ENMs in toners classifies them as nano-enabled products (NEPs); (ii) These ENMs become airborne during printing; (iii) The chemistry of PEPs is complex and it reflects that of the toner and paper. This work highlights the importance of understanding life-cycle (LC) nano-EHS implications of NEPs and assessing real world exposures and associated toxicological properties rather than focusing on “raw” materials used in the synthesis of an NEP.     

纳米材料表观遗传学效应的研究进展

随着纳米科技的发展和纳米材料的广泛应用,人们暴露于纳米材料的机会日益增多,对其所引起的表观遗传学效应的研究也逐渐增多。纳米材料介导的体外表观遗传学效应与其种类、性质和处理条件等有关。纳米银可使细胞基因组整体甲基化水平升高且具有浓度效应关系;氧化锌、氧化钛和结晶型二氧化硅纳米颗粒会降低基因组整体甲基化水平;碳纳米管(NT)仅发现有特异基因甲基化作用。同时,DNA甲基化酶的水平也受纳米材料影响。纳米材料介导的组蛋白修饰作用多为乙酰化和磷酸化,并受到其电荷和存在状态(晶体,非晶体)的影响。对于纳米材料诱导的微RNA(miRNA)表达变化的研究,多采用高通量方法,差异表达的miRNA结果异质性大,且会受到纳米材料粒径、表面电荷、处理时间和浓度的影响。在体实验仅有纳米材料介导的甲基化和miRNA表达水平相关的研究,且多为长期重复暴露实验,除与体外实验结果相似外,还发现了纳米材料所致甲基化水平改变具有可逆性和组织特异性,对幼龄大鼠和(或)小鼠的效应更强。尽管近年来发表了许多有关纳米材料表观遗传学效应的研究,但有些结果还不确定,其是否具有可遗传性仍有待研究。本文综述了纳米材料对DNA甲基化、组蛋白修饰和miRNA表达水平的影响,希望能为纳米材料表观遗传学效应的研究提供参考。     

The potential exposure and hazards of copper nanoparticles: A review

Copper is an essential element for metabolism in plants and animals. In its nanoform, copper has found various applications, thus increasing potential environmental exposure. Released nanoparticles in the environment undergo various transformation processes while bioaccumulation and toxicity of copper nanoparticles have been demonstrated in plants and animals. This toxicity is thought to be a combined effect of intracellular particles and the release of dissolved copper ions. Oxidative stress responses have been studied in copper nanoparticle induced effects as well as other pathways to cytotoxicity. The antimicrobial potential of copper nanoparticles makes them excellent components for application in biomedicine and more recently, they have been investigated for applications as drug delivery agents in cancer therapy. These properties of copper nanoparticles necessitate a thorough review and understanding of toxic mechanisms of action and the associated implications of exposure to human and environmental health.     

Assessment of the toxic potential of engineered metal oxide nanomaterials using an acellular model: citrated rat blood plasma

Citrated Sprague–Dawley rat blood plasma was used as a biologically relevant exposure medium to assess the acellular toxic potential of two metal oxide engineered nanomaterials (ENMs), zinc oxide (nZnO), and cerium oxide (nCeO₂). Plasma was incubated at 37?°C for up to 48?h with ENM concentrations ranging between 0 and 200?mg/L. The degree of ENM-induced oxidation was assessed by assaying for reactive oxygen species (ROS) levels using dichlorofluorescein (DCF), pH, ferric reducing ability of plasma (FRAP), lipase activity, malondialdehyde (MDA), and protein carbonyls (PC). Whereas previous in vitro studies showed linear-positive correlations between ENM concentration and oxidative damage, our results suggested that low concentrations were generally pro-oxidant and higher concentrations appeared antioxidant or protective, as indicated by DCF fluorescence trends. nZnO and nCeO₂ also affected pH in a manner dependent on concentration and elemental composition; higher nZnO concentrations maintained a more alkaline pH, while nCeO₂ tended to decrease pH. No other biomarkers of oxidative damage (FRAP, MDA, PC, lipase activity) showed changes at any ENM concentration or time-point tested. Differential dissolution of the two ENMs was also observed, where as much as ～31.3% of nZnO was instantaneously dissolved to Zn^2+?and only negligible nCeO₂ was degraded. The results suggest that the direct oxidative potential of nZnO and nCeO₂ in citrated rat blood plasma is low, and that a physiological or immune response is needed to generate appreciable damage biomarkers. The data also highlight the need for careful consideration when selecting a model for assessing ENM toxicity.     

In vitro intestinal toxicity of copper oxide nanoparticles in rat and human cell models

Abstract

Human oral exposure to copper oxide nanoparticles (NPs) may occur following ingestion, hand-to-mouth activity, or mucociliary transport following inhalation. This study assessed the cytotoxicity of Cupric (II) oxide (CuO) and Cu₂O-polyvinylpyrrolidone (PVP) coated NPs and copper ions in rat (intestine epithelial cells; IEC-6) and human intestinal cells, two- and three-dimensional models, respectively. The effect of pretreatment of CuO NPs with simulated gastrointestinal (GI) fluids on IEC-6 cell cytotoxicity was also investigated. Both dose- and time-dependent decreases in viability of rat and human cells with CuO and Cu₂O-PVP NPs and Cu²⁺ ions was observed. In the rat cells, CuO NPs had greater cytotoxicity. The rat cells were also more sensitive to CuO NPs than the human cells. Concentrations of H₂O₂ and glutathione increased and decreased, respectively, in IEC-6 cells after a 4-h exposure to CuO NPs, suggesting the formation of reactive oxygen species (ROS). These ROS may have damaged the mitochondrial membrane of the IEC-6 cells causing a depolarization, as a dose-related loss of a fluorescent mitochondrial marker was observed following a 4-h exposure to CuO NPs. Dissolution studies showed that Cu₂O-PVP NPs formed soluble Cu whereas CuO NPs essentially remained intact. For GI fluid-treated CuO NPs, there was a slight increase in cytotoxicity at low doses relative to non-treated NPs. In summary, copper oxide NPs were cytotoxic to rat and human intestinal cells in a dose- and time-dependent manner. The data suggests Cu₂O-PVP NPs are toxic due to their dissolution to Cu ions, whereas CuO NPs have inherent cytotoxicity, without dissolving to form Cu ions.     

Toxicity of copper oxide and basic copper carbonate nanoparticles after short-term oral exposure in rats

Copper oxide (CuO) nanoparticles (NPs) and copper carbonate nanoparticles (Cu₂CO₃(OH)₂ NPs have applications as antimicrobial agents and wood preservatives: an application that may lead to oral ingestion via hand to mouth transfer. Rats were exposed by oral gavage to CuO NPs and Cu₂CO₃(OH)₂ NPs for five consecutive days with doses from 1 to 512?mg/kg and 4 to 128?mg/kg per day, respectively, and toxicity was evaluated at days 6 and 26. Both CuO NPs and Cu₂CO₃(OH)₂ NPs induced changes in hematology parameters, as well as clinical chemistry markers (e.g. increased alanine aminotransferase, ALT) indicative of liver damage For CuO NPs histopathological alterations were observed in bone marrow, stomach and liver mainly consisting of an inflammatory response, ulceration, and degeneration. Cu₂CO₃(OH)₂ NPs induced morphological alterations in the stomach, liver, intestines, spleen, thymus, kidneys, and bone marrow. In spleen and thymus lymphoid, depletion was noted that warrants further immunotoxicological evaluation. The NPs showed partial dissolution in artificial simulated stomach fluids, while in intestinal conditions, the primary particles simultaneously shrank and agglomerated into large structures. This means that both copper ions and the particulate nanoforms should be considered as potential causal agents for the observed toxicity. For risk assessment, the lowest bench mark dose (BMD) was similar for both NPs for the serum liver enzyme AST (an indication of liver toxicity), being 26.2?mg/kg for CuO NPs and 30.8?mg/kg for Cu₂CO₃(OH)₂ NPs. This was surprising since the histopathology evidence demonstrates more severe organ damage for Cu₂CO₃(OH)₂ NPs than for CuO NPs.     

A comparative study of the toxicological aspects of vanadium pentoxide and vanadium oxide nanoparticles

Abstract

Indiscriminate use of vanadium oxide nanoparticles (NPs) in steel industries and their release during combustion of fossil fuels makes it essential to study their toxic potential. Herein, we assessed the toxicological effects of two types of in-house synthesized vanadium oxide NPs in Wistar rats exposed to NPs through inhalation route. V₂O₅ and VO₂ NPs exhibited rod and spherical symmetry, respectively with a mean diameter of 50?±?20 and 30?±?10?nm. Assessment of bronchoalveolar lavage fluid parameters demonstrated that VO₂ NP-exposed animals had higher levels of lactate dehydrogenase, gamma-glutamyl transpeptidase and alkaline phosphatase as compared to V₂O₅ NP-exposed animals. The levels of oxidative stress markers malondialdehyde and reduced glutathione also indicated higher toxic potential of VO₂ NPs. Moreover, after 7-day recovery, the levels of the above parameters were closer to normal levels only in V₂O₅-exposed animals. Interestingly, histopathological and immune-histopathology analysis (TNF-α) of lung tissue showed higher damage and inflammatory response in VO₂ NP-exposed animals, which persisted even after 7 days of recovery period. Surprisingly, the carcinogenic potential of vanadium oxide NPs came into light which was indicated by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay as well as the decreased levels of p53 and Bax, in lung tissue of NP-exposed animals. Notably, the physiochemical characterization of NPs, especially the shape and the size, play a central role in shaping the toxicity of these NPs and thus should be extensively evaluated for outlining the regulatory guidelines.     

Comparative study of cytotoxicity, oxidative stress and genotoxicity induced by four typical nanomaterials: the role of particle size, shape and composition

Although the biological effects of some nanomaterials have already been assessed, information on toxicity and possible mechanisms of various particle types are insufficient. Moreover, the role of particle properties in the toxic reaction remains to be fully understood. In this paper, we aimed to explore the interrelationship between particle size, shape, chemical composition and toxicological effects of four typical nanomaterials with comparable properties: carbon black (CB), single wall carbon nanotube, silicon dioxide (SiO(2)) and zinc dioxide (ZnO) nanoparticles. We investigated the cytotoxicity, genotoxicity and oxidative effects of particles on primary mouse embryo fibroblast cells. As observed in the methyl thiazolyl tetrazolium (MTT) and water-soluble tetrazolium (WST) assays, ZnO induced much greater cytotoxicity than non-metal nanoparticles. This was significantly in accordance with intracellular oxidative stress levels measured by glutathione depletion, malondialdehyde production, superoxide dismutase inhibition as well as reactive oxygen species generation. The results indicated that oxidative stress may be a key route in inducing the cytotoxicity of nanoparticles. Compared with ZnO nanoparticles, carbon nanotubes were moderately cytotoxic but induced more DNA damage determined by the comet assay. CB and SiO(2) seemed to be less effective. The comparative analysis demonstrated that particle composition probably played a primary role in the cytotoxic effects of different nanoparticles. However, the potential genotoxicity might be mostly attributed to particle shape.     

Synthesis of silver and copper oxide nanoparticles using Myristica fragrans fruit extract: Antimicrobial and catalytic applications

The pericarp of Myristica fragrans fruit extract was utilized for a low cost, eco-friendly synthesis of silver (AgNPs) and copper oxide (CuONPs) nanoparticles. The aqueous fruit extract of the plant was used as reducing and stabilizing agents for this preparation. Characterization of the biosynthesized nanoparticles was carried out using UV–Vis spectroscopy, FTIR spectroscopy and X-Ray Diffraction studies. Morphology and size of the particles was observed using Field-Emission Scanning Electron Microscopy (FESEM) and High Resolution Transmission Electron Microscopy (HRTEM). The copper and silver nanoparticles show Surface Plasmon Resonance (SPR) band at 360 and 478 nm respectively in the UV–Vis spectrum. It was observed that size of the synthesized copper oxide and silver nanoparticles are in the range 10–50 nm. The presence of copper and silver elements was confirmed from their respective EDS spectrum. Involvement of phytochemicals in the stabilization and reduction of the nanoparticles was confirmed by FTIR spectroscopy. CuONPs exhibited catalytic activity in 1,3-dipolar cycloaddition reaction between azides and terminal alkynes to form 1,2,3-triazoles. Silver nanoparticle possesses good antibacterial activity against multidrug human pathogens Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis. The present study focuses on the utilization of the less economic part of Myristica fragrans fruit's pericarp for the preparation of copper oxide and silver nanoparticles which have good catalytic and antibacterial activities.     

In vitro toxicological assessment of iron oxide,aluminium oxide and copper nanoparticles in prokaryotic and eukaryotic cell types

Metallic nanoparticles (NPs) have a variety of applications in different industries including pharmaceutical industry where these NPs are used mainly for image analysis and drug delivery. The increasing interest in nanotechnology is largely associated with undefined risks to the human health and to the environment. Therefore, in the present study cytotoxic and genotoxic effects of iron oxide, aluminium oxide and copper nanoparticles were evaluated using most commonly used assays i.e. Ames assay, in vitro cytotoxicity assay, micronucleus assay and comet assay. Cytotoxicity to bacterial cells was assessed in terms of colony forming units by using Escherichia coli (gram negative) and Bacillus subtilis (gram positive). Ames assay was carried out using two bacterial strains of Salmonella typhimurium TA98 and TA100. Genotoxicity of these NPs was evaluated following exposure to monkey kidney cell line, CHS-20. No cytotoxic and genotoxic effects were observed for iron oxide, and aluminium oxide NPs. Copper NPs were found mutagenic in TA98 and in TA100 and also found cytotoxic in dose dependent manner. Copper NPs induced significant (p?相似文献   

Cell damage induced by copper: An explant model to study anemone cells

Sea anemones are benthic organisms, of low mobility and can be directly affected by water pollution. This work studied the defense mechanisms and DNA damage caused by copper toxicity in cells from the anemone Bunodosoma cangicum. For this, exposure of anemones cells were held, kept in primary culture through explant of podal disk to copper (7.8 and 15.6 μg/L), and the control group, for 6 and 24 h. Cytotoxicity was seen through the viability and cell number, MXR phenotype through the accumulation of rhodamine-B, ROS generation by H₂DCF-DA and DNA damage by comet assay. The results obtained show that there is a drop in viability and number of cells, especially after exposure of 24 h in 15.6 μg/L. There is an induction of the MXR activity only at 7.8 μg/L for 24 h. As for ROS, there is an increase in the generation of reactive species in greatest concentration of copper for 6 h, and in both for 24 h, which leads to oxidative stress, which culminates with a DNA damage. What was evidenced by the increase of the tail size, % DNA presented and moment of tail. Therefore, the copper represents an adversity to the anemones cells, being cytotoxic and genotoxic.     

In vitro comparative cytotoxicity study of aminated polystyrene,zinc oxide and silver nanoparticles on a cervical cancer cell line

Nanoparticles use in nano-biotechnology applications have increased significantly with Aminated polystyrene amine (AmPs NP), Zinc oxide (ZnO NP), and Silver (Ag NP) nanoparticles utilized in wide variety of consumer products. This has presented a number of concerns due to their increased exposure risks and associated toxicity on living systems. Changes in the structural and physicochemical properties of nanoparticles can lead to changes in biological activities. This study investigates, compares, and contrasts the potential toxicity of AmPs, ZnO and Ag NPs on an in vitro model (HeLa cells) and assesses the associated mechanism for their corresponding cytotoxicity relative to the surface material. It was noted that NPs exposure attributed to the reduction in cell viability and high-level induction of oxidative stress. All three test particles were noted to induce ROS to varying degrees which is irrespective of the attached surface group. Cell cycle analysis indicated a G2/M phase cell arrest, with the corresponding reduction in G0/G1 and S phase cells resulting in caspase-mediated apoptotic cell death. These findings suggest that all three NPs resulted in the decrease in cell viability, increase intracellular ROS production, induce cell cycle arrest at the G2/M phase and finally result in cell death by caspase-mediated apoptosis, which is irrespective of their differences in physiochemical properties and attached surface groups.     

In vitro investigation of immunomodulatory effects caused by engineered inorganic nanoparticles – the impact of experimental design and cell choice

This study describes immunomodulatory effects of small inorganic nanoparticles and the impact of experimental design therein. Gold, cobalt oxide and iron oxide nanoparticles were synthesized in solution under conditions that ensured monodispersed and stable particles in solvents and when diluted in cell culture medium. Particles and solvents were tested for their cytotoxic and cytokine regulatory effects on immortalized and primary human lung epithelial cells in the absence and presence of the pro-inflammatory cytokine TNF-α. The particle-suspensions and solvents were not cytotoxic, but a significant effect on cytokine induction due to the chemical solvents was observed, although these are routinely used in nanoparticles synthesis. Significant immunomodulatory effects of some particle types on the immortalized epithelial cells were observed, these effects were more pronounced in primary epithelial cells. In conclusion, the solvent used to prepare the nanoparticles and the choice of cell type can affect the outcome of nanotoxicological studies.     

Toxicity of silver and copper to Cucurbita pepo: Differential effects of nano and bulk-size particles

The phytotoxicity of bulk and nanoparticle Cu and Ag was directly compared. NP Ag reduced biomass and transpiration by 66–84% when compared with bulk Ag. The Ag ion concentration was 4.4–10‐times greater in NP than bulk particle solutions. The Cu ion concentration was 1.4–4.4‐times greater in bulk than NP amended solutions. Humic acid (50 mg/L) decreased the ion content of bulk Cu solution by 38–42% but increased ion Cu content of NP solutions by 1.4–2.9 times. Bulk and NP Cu were highly phytotoxic; growth and transpiration were reduced by 60–70% relative to untreated controls. NP Cu phytotoxicity was unaffected by solution type, but humic acid (50 mg/L) completely alleviated phytotoxicity caused by bulk Cu. The data demonstrate differential toxicity of Ag NP relative to bulk Ag. The finding that humic acid and solution chemistry differentially impact bulk and NP behavior highlights the importance of evaluating nanoparticles under environmentally relevant conditions. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.     

In vitro immunotoxicological assessment of a potent microbicidal nanocomposite based on graphene oxide and silver nanoparticles

Graphene oxide (GO) and silver nanoparticles (AgNPs) can be formed into a hybrid nanomaterial, known as GOAg nanocomposite, which presents high antibacterial activity. The successful translation of this nanomaterial into medical use depends on critical information about its toxicological profile. In keeping with a Safe-by-design approach, we evaluated the immunotoxicity of GOAg using J774 and primary murine macrophages. The interaction between GOAg and macrophages was investigated with a scanning electron microscope (SEM). High-throughput technologies were employed to evaluate cell viability, apoptosis/necrosis, mitochondrial depolarization and lipid peroxidation. The inflammogenicity of nanomaterials was predicted after quantification of the cytokines IL-1β, TNF-α and IL-10 before and after stimulation with interferon-γ (IFN-γ). The ratio between CD80 and CD206 macrophage populations were also estimated. In addition, the production of nitric oxide (NO) was investigated. SEM surveys revealed the potential of GOAg to induce frustrated phagocytosis. GOAg induced a dose-dependent mitochondrial depolarization, apoptosis and lipid peroxidation to J774 macrophages. GOAg toxicity was not modified in an inflammatory microenvironment, but its toxicity was within the range of concentrations used in bacterial inactivation. GOAg did not induce primary macrophages to significantly produce inflammatory cytokines, and previous macrophage stimulation did not enhance GOAg inflammogenicity. Additionally, the pristine nanomaterials and GOAg do not shift macrophages polarization towards M1. Sublethal concentrations of GOAg did not impair macrophages NO production. Finally, we suggest options for improvement of GOAg nanocomposite in ways that may help minimize its possible adverse outcomes to human health.     

Pulmonary toxicity and kinetic study of Cy5.5-conjugated superparamagnetic iron oxide nanoparticles by optical imaging

Recent advances in the development of nanotechnology and devices now make it possible to accurately deliver drugs or genes to the lung. Magnetic nanoparticles can be used as contrast agents, thermal therapy for cancer, and be made to concentrate to target sites through an external magnetic field. However, these advantages may also become problematic when taking into account safety and toxicological factors. This study demonstrated the pulmonary toxicity and kinetic profile of anti-biofouling polymer coated, Cy5.5-conjugated thermally cross-linked superparamagnetic iron oxide nanoparticles (TCL-SPION) by optical imaging. Negatively charged, 36 nm-sized, Cy5.5-conjugated TCL-SPION was prepared for optical imaging probe. Cy5.5-conjugated TCL-SPION was intratracheally instilled into the lung by a non-surgical method. Cy5.5-conjugated TCL-SPION slightly induced pulmonary inflammation. The instilled nanoparticles were distributed mainly in the lung and excreted in the urine via glomerular filtration. Urinary excretion was peaked at 3 h after instillation. No toxicity was found under the concentration of 1.8 mg/kg and the half-lives of nanoparticles in the lung and urine were estimated to be about 14.4 ± 0.54 h and 24.7 ± 1.02 h, respectively. Although further studies are required, our results showed that Cy5.5-conjugated TCL-SPION can be a good candidate for use in pulmonary delivery vehicles and diagnostic probes.     

Green synthesis of zinc oxide nanoparticles: A review of the synthesis methodology and mechanism of formation

Zinc oxide is of significant importance for many industries due to its versatile properties, which have been enhanced with the production of this material in the nanoscale. Nonetheless, the increase in concerns related to environmental impact has led to the development of eco-friendly processes for its production. Recent interest in obtaining metal and metal oxide nanoparticles using biological approaches has been reported in the literature. This method was termed ‘green synthesis’ as it is a less hazardous process than chemical and physical synthesis methods currently used in the industry to obtain these nanomaterials. Zinc oxide nanoparticles have been successfully obtained by green synthesis using different biological substrates. However, large scale production using green synthesis approaches remains a challenge due to the complexity of the biological extracts that poses a barrier onto the elucidation of the reactions and mechanism of formation that occur during the synthesis. Hence, the current review includes a summary of the different sources of biological substrates and methodologies applied to the green synthesis of zinc oxide nanoparticles and the impact on their properties. This work also describes the advances on the understanding of the mechanism routes reported in the literature.     

In vitro cytotoxicity of superparamagnetic iron oxide nanoparticles on neuronal and glial cells. Evaluation of nanoparticle interference with viability tests

Superparamagnetic iron oxide nanoparticles (ION) have attracted great interest for use in several biomedical fields. In general, they are considered biocompatible, but little is known of their effects on the human nervous system. The main objective of this work was to evaluate the cytotoxicity of two ION (magnetite), coated with silica and oleic acid, previously determining the possible interference of the ION with the methodological procedures to assure the reliability of the results obtained. Human neuroblastoma SHSY5Y and glioblastoma A172 cells were exposed to different concentrations of ION (5–300 µg ml^–1), prepared in complete and serum‐free cell culture medium for three exposure times (3, 6 and 24 h). Cytotoxicity was evaluated by means of the MTT, neutral red uptake and alamar blue assays. Characterization of the main physical–chemical properties of the ION tested was also performed. Results demonstrated that both ION could significantly alter absorbance readings. To reduce these interferences, protocols were modified by introducing additional washing steps and cell‐free systems. Significant decreases in cell viability were observed for both cell lines in specific conditions by all assays. In general, oleic acid‐coated ION were less cytotoxic than silica‐coated ION; besides, a serum‐protective effect was observed for both ION studied and cell lines. These results contribute to increase the knowledge of the potential harmful effects of ION on the human nervous system. Understanding these effects is essential to establish satisfactory regulatory policies on the safe use of magnetite nanoparticles in biomedical applications. Copyright © 2015 John Wiley & Sons, Ltd.