In the last decade, the nanotechnology advancement has developed a plethora of novel and intriguing nanomaterial application in many sectors, including research and medicine. However, many risks have been highlighted in their use, particularly related to their unexpected toxicity in vitro and in vivo experimental models. This paper proposes an overview concerning the cell death modalities induced by the major nanomaterials.
1. Introduction
Nanotechnologies are emerging for important new applications of nanomaterials in various fields. Nanomaterials are defined as substances which have one or more external dimension in the nanoscale (1–100 nm). Nanomaterials, especially nanoparticles and nanofibres, show higher physical and chemical activities per unit weight. These properties explain their large application not only in industry but also in the scientific and medical researches. In fact, in these areas, the use of many kinds of manufactured nanoparticles products is in development, such as metal oxide nanoparticles (cerium dioxide, cupric oxide, titanium dioxide, zinc oxide, etc.), metal nanoparticles (gold, silver, platinum, palladium, etc.), C60 fullerenes nanocrystals, carbon nanotubes (CNTs), and quantum dots. Initially, the nanomaterials were believed to be biologically inert, but a growing literature has highlighted the toxicity and potential risks of their use. Extrapolations from the field of toxicology of particulate matter (less than 10 nm) confirm that nanoparticles present a range of harmful effects [1, 2]. In most cases, enhanced generation of reactive oxygen species (ROS), leading to oxidative stress which in turn may trigger proinflammatory responses, is assumed to be responsible for nanomaterials toxicity, although nonoxidative stress-related mechanisms have also been recently reported (see the extensive and interesting reviews [3–10]). However, despite intensive investigations, the understanding of nanomaterials-induced cellular damage remains to be clarified. The literature in the field suggests correlations between different physicochemical properties and the biological and toxicological effects of cells and tissues exposure to nanomaterials. First of all, nanomaterials are characterized by high specific surface area that correlates with high interfacial chemical and physical reactivity that, in turn, translates to biological reactivity [11]. The addition of different types of nanoparticles to various primary cell cultures or transformed cell lines may result in cell death or other toxicological outcomes, depending on the size of the nanomaterial. Quantum dots were reported to localize to different cellular compartment in a size-dependent manner [12]. Silica nanoparticles (40–80 nm) can enter into the nucleus and localize to distinct subnuclear domains in the nucleoplasm, whereas thin and coarse ones located exclusively in the cytoplasm [13]. Gold nanocluster (1.4 nm) intercalates within the major groove of DNA and is a potent inducer of cell death in human cancer cells [14]. Growing evidence suggests that the state of nanoparticles aggregation cannot be ignored; in fact, the toxicity may depend on the size of the agglomerate and not on the original nanoparticle size itself [15, 16]. For example, in rats exposed by inhalation to 20 nm or 250 nm titanium dioxide (TiO2) particles, the half-times for alveolar clearance of polystyrene test particles were proportional to the TiO2 particle surface area per million of macrophages [17, 18]. Clearly, a surface impurity, resulting from air or water contaminants such as bacterial endotoxin, could contribute to the cellular responses induced by nanomaterials, in particular immunological responses [16]. The same consideration is true for residual materials (surfactants or transition metals) arising from the synthetic process [6, 19, 20]. Nevertheless, the adsorption ability and surface activity are also involved in cellular influences of nanomaterials. When dispersed in culture medium, some metal oxide nanoparticles and CNTs could adsorb proteins, often called “protein corona” such as serum albumin, or calcium, which could change the biological activity of nanomaterials. This adsorption could be particle size and time dependent. In these conditions, many nanoparticles form secondary particles, which are a complex of nanoparticles and medium components [21–26]. For example, adsorbed albumin on the CNT was involved in phagocytosis of the macrophage via scavenger receptor [27]. A surface-engineered functionalization also may be linked with the biological nanomaterials activity, although in this item that is a wanted effect. Moreover, examples of dose-dependent toxicity also are evaluated [6, 28, 29]. As pointed out in a recent review [6], the degree of recognition and internalization of nanomaterials likely influences their distribution and may determine also their toxic potential. It has been reported that the number of internalized quantum dots (the intracellular dose) correlates with the toxicity in human breast cancer cell line [30]. Furthermore, the toxicity and cell death fate appear to correlate with the type of crystal structures [16, 31]. Finally, the nanomaterials degradability should also be taken into account (Figure 1). Nondegradable nanomaterials can accumulate into the cells and/or organs and exert damage effect as well as their degradation products [32–34]. However, it is not yet clear which of these parameters mainly influences the nanomaterials toxicity or if all of these features act together [35]. It is important to note that in the literature conflicting results are present. These are likely caused by variations in type, composition, size, shape, surface charge, and modifications of nanoparticles employed; use of various in vivo and in vitro models (the cell death mode may be also cell type dependent); experimental procedures (different methods to evaluate cell death; nanomaterials dose, concentrations and efficiency of cellular uptake, and time of exposure). This paper aims to give a critical overview concerning the different cell death modalities induced by nanomaterials.
Deregulated cell death is a common element of several human diseases, including cancer, stroke, and neurodegeneration, and the modulation of this cellular response can be an optimal target for an effective therapeutic strategy. Many cytotoxic agents are potent anticancer therapeutics, whereas cytoprotective compounds may be used to elude unwanted cell death in the context of stroke, myocardial infarction or neurodegenerative disorders [36, 37]. The complex molecular mechanisms and signalling pathways that control cell death are increasingly becoming understood, and it is now clear that different cell death subroutines play a critical role in multiple diseases. In many instances, the modality by which cells die is crucial to the cell death achievement at the organism level. The Nomenclature Committee on Cell Death (NCCD) has recently formulated a novel systematic classification of cell death based on morphological characteristics, measurable biochemical features and functional considerations [38]. We will consider these definitions of cell death in order to summarize and organize the molecular mechanisms underlying the nanomaterials toxicity. We could not report all the studies, and we apologize for this; we will describe the most recently, accurate, and representative ones in term of the described molecular mechanisms.
2. Nanomaterials and Apoptosis
Apoptosis is a form of cellular suicide that can be classified into extrinsic and intrinsic apoptosis. Extrinsic apoptosis indicates the cell death, caspase dependent, stimulated by extracellular stress signals that are sensed and propagated by specific transmembrane receptors. Three major lethal signalling cascades have been reported: (i) death receptor signalling and activation of the caspase-8 (or -10) and then caspase-3 cascade; (ii) death receptor signalling and activation of the caspase-8 then BH3-interacting domain death agonist (BID), mitochondrial outer membrane permeabilization (MOMP), caspase-9 and caspase-3 pathways; and (iii) ligand deprivation-induced dependence receptor signalling followed by (direct or MOMP-dependent) activation of the caspase-9 and after caspase-3 cascade [38]. Intrinsic apoptosis can be triggered by a plethora of intracellular stress conditions, such as DNA damage, oxidative stress, and many others. It results from a bioenergetic and metabolic catastrophe coupled to multiple active executioner mechanisms. This process could be caspase-dependent or- independent and is mediated by MOMP associated with the generalized and irreversible dissipation of the mitochondrial transmembrane potential, release of mitochondrial intermembrane space proteins into the cytosol (and their possible relocalization to other subcellular compartments), and the respiratory chain inhibition [38]. Apoptosis plays a fundamental role in development and for maintenance of tissue homeostasis in the adult organism. In addition, impairment of apoptosis may contribute to tumour progression.
Nanomaterials are described as triggers of extrinsic and intrinsic apoptotic pathways; however, the oxidative stress paradigm of nanomaterials-induced cell death linked to intrinsic apoptotic network is by far the most accepted, in fact many in vitro studies have identified increased ROS generation as an initiating factor of toxicity in nanomaterials exposed cells [3, 6, 7, 10, 39]. Although it is well established that the mode of cell death depends on the severity of the cellular insult (which may, in turn, be linked to mitochondrial function and intracellular energy), it has been difficult to set up a comprehensive mechanism of nanomaterials cell death based on conflicting observations present in the literature. Furthermore, in most of the studies, the molecular mechanisms underlying cell death are not investigated. Finally, another problem is the nonhomogeneity of the studies, in terms of materials and experimental methods used, which makes it difficult to compare.
Sarkar and colleagues showed that the nano-copper induces intrinsic apoptotic cell death in mice kidney tissue (via the increase of ROS and reactive nitrogen species production, regulation of Bcl-2 family protein expression, release of cytochrome c from mitochondria to cytosol, and activation of caspase-3), but, in addition, they observed the activation of FAS, caspase-8, and tBID, suggesting also the involvement of extrinsic pathways [40]. The exposure to nano-copper dose-dependently caused oxidative stress and led to hepatic dysfunction in vivo. Nano-copper caused the reciprocal regulation of Bcl-2 family proteins, disruption of mitochondrial membrane potential, release of cytochrome c, formation of apoptosome, and activation of caspase-3. These results indicate that nano-copper induces hepatic dysfunction and cell death via the oxidative stress-dependent signalling cascades and mitochondrial event [41].
Metallic nickel nanoparticles induced apoptotic cell death through an FAS/caspase-8/BID mediated, cytochrome c-independent pathway in mouse epidermal cells [42]. Nickel oxide nanoparticles excited in dose-dependent manner the increase of ROS production, lipid peroxidation, and caspase-3 activation in human airway epithelial and breast cancer cells [43]. Moreover, nickel ferrite nanoparticles provoked apoptosis in human lung epithelial cells through ROS generation via upregulation of p53 and Bax as well as the activation of caspases cascade [44].
In vitro, silicon dioxide (SiO2) nanoparticles increased ROS and RNS (reactive nitrogen species) production that, in turn, can induce the intrinsic apoptotic machinery [45]. Furthermore, Wang and collaborators showed that p53 plays a key role in silica-induced apoptosis in vitro (mouse preneoplastic epidermal cells and fibroblasts) and in vivo (p53 wild-type and deficient mice) [46].
TiO2 nanoparticles, sized less than 100 nm, triggered apoptotic cell death through ROS-dependent upregulation of FAS and activation of Bax in normal human lung fibroblast and breast epithelial cell lines [47]. Moreover, it was also demonstrated that TiO2 nanoparticles induced apoptosis through the caspase-8/BID pathway in human bronchial epithelial cells and lymphocytes as well as in mouse preneoplastic epidermal cells [48, 49]. Some reports indicated that TiO2 induced also lipid peroxidation, p53-mediated damage response, and caspase activation [50, 51]. In contrast, there are also reports demonstrating that TiO2 nanoparticles did not induce oxidative stress on mouse macrophages [52] as well as did not shown cytotoxicity in human dermal fibroblasts and lung epithelial cells [31].
A number of studies have been published concerning the effects of CNTs on apoptosis. Multiwall carbon nanotubes (MWCNTs) induced an increase of ROS, cell cycle arrest, decrease in mitochondrial membrane potential, determining apoptosis in different in vitro models [53–56]. In contrast, another study reported that these nanotubes were nontoxic [57]. Accordingly, it has been observed that MWCNTs did not stimulate cell death in vitro after acute exposure and neither after the continuous presence of their low amounts for 6 months [58]. Instead, apoptotic macrophages have been observed in the airways of mice after inhalation of SWCNTs (single-walled carbon nanotubes) [6]. Accordingly, several studies in vivo suggest that the exposure to SWCNTs leads to the activation of specific apoptosis signalling pathways [59, 60]. For more details, recent interesting reviews focus on the nanomaterials toxicity in vivo studies [6, 34].
Nanoparticles are frequently detected in lysosomes upon internalization, and a variety of nanomaterials have been associated with lysosomal dysfunction [61]. It has been established that lysosomal destabilization triggers the mitochondrial pathway of apoptosis [62, 63]. Carbon nanotubes were shown to induce lysosomal membrane permeabilization and apoptotic cell death in murine macrophages and human fibroblasts [64, 65]. Carbon black nanoparticles elicited intrinsic apoptosis in human bronchial epithelial cells with activation of Bax and release of cytochrome c from mitochondria, whereas TiO2 nanoparticles induced apoptosis through lysosomal membrane destabilization and cathepsin B release, suggesting that the pathway of apoptosis differs depending on the nanomaterials chemical nature [66]. The lysosomal destabilization induced by TiO2 is also confirmed in mouse fibroblasts [67]. SiO2 and several cationic nanoparticles, such as cationic polystyrene nanospheres and cationic polyamidoamine (PAMAM) dendrimers, have also shown the same mode of action [68–70]. However, also the micromaterials are able to destabilize lysosomes, in fact silica microparticles have been demonstrated to induce apoptosis in mouse alveolar macrophages by this molecular mechanism [70]. A comparative study of nano- versus microscale gold particles demonstrated that nanoparticles present a higher potency in the induction of lysosomal membrane destabilization [71].
Chronic or unresolved endoplasmic reticulum (ER) stress can also cause apoptosis [72, 73]. Zhang and colleagues reported that the ER stress signalling is involved in silver nanoparticles-induced apoptosis in human Chang liver cells and Chinese hamster lung fibroblasts [74]. Using omic techniques and systems biology analysis, Tsai and collaborators demonstrated that upon ER stress, cellular responses, including ROS increase, mitochondrial cytochrome c release, and mitochondria damage, chronologically occurred in the gold nanoparticles-treated human leukemia cells. This treatment did not induce apoptosis in the normal human peripheral blood mononuclear cells [75]. It has been shown that poly(ethylene glycol)-phosphoethanolamine (PEG-PE), an FDA-approved nonionic diblock copolymer widely used in drug delivery systems, accumulated in the ER and induced ER stress and apoptosis only in cancer cells (human adenocarcinomia alveolar basal epithelial), whereas it did not have effect in normal cells (secondary human lung fibroblasts and embryonic kidney cells) [76].
The predisposition of some nanoparticles to target mitochondria, ER, or lysosomes and initiate cell death could be used as a new cancer chemotherapy principle.
Interestingly, nanoparticles (polystyrene nanoparticles of 20–40 nm with two different surface chemistries, carboxylic acid, and amines) may also induce apoptosis in individual cells (differentiated human colorectal adenocarcinoma) that then propagates to other neighbouring cells through a “bystander killing effect.” The authors of this study suggest that ingested nanoparticles represent a potential health risk due to their detrimental impact on the intestinal membrane by destroying their barrier protection capability over time [77].
Surely in this context, a common incentive to synchronize the studies and research efforts is needed. The understand why cancer cells and distinctive normal cells have different cell fates as a result of nanomaterials exposure, focusing on the underlying mechanisms, will allow a better prediction of the consequences of exposure to nanomaterials and a safer assessment of the risks (Figure 2).
3. Nanomaterials and Mitotic Catastrophe
Recently, Vitale and colleagues suggested a novel definition of mitotic catastrophe based on functional consideration [78]. They proposed to consider mitotic catastrophe not a “pure” cell death executioner pathway but as an oncosuppressive mechanism that is triggered by perturbations of the mitotic apparatus, is initiated during the M phase of the cell cycle, is paralleled by some degree of mitotic arrest, and induces cell death (apoptosis or necrosis) and senescence [78].
It has been reported that several nanomaterials, such as SiO2, TiO2, cobalt-chrome (CoCr) metal particles, and carbon nanotubes, interact with structural elements of the cell, with an apparent binding to the cytoskeleton and in particular the tubulins [79, 80]. In this setting, some evidence in vitro demonstrated that carbon nanotubes mimic or interfere with the cellular microtubule system, thereby disrupting the mitotic spindle apparatus and leading to aberrant cell division [81–83]. In particular, the perturbation of centrosomes and mitotic spindles dynamics caused by these nanoparticles results in monopolar, tripolar, and quadripolar divisions, that, in turn, could determinate aneuploidy [78], an event closely linked to the carcinogenesis. Tsaousi and collaborators found that alumina ceramic particles increase significantly in micronucleated binucleate cells [84], which is considered a morphological marker of mitotic catastrophe [78]. Interestingly, this increase was much greater after exposure of primary human fibroblasts to CoCr metal particles, suggesting that these nanoparticles are particularly efficient in affecting the mitotic machinery [84]. Apparently, the genotoxic effect of CoCr nanoparticles is size dependent. Indeed, CoCr nanoparticles induced more DNA damage than microsized ones in human fibroblasts (Figure 3). In fact, the mechanism of cell damage appears to be different after nano- or microparticles exposure. The enhanced oxidative DNA damage by the microparticles may result from a stronger ability of large particles to activate endogenous pathways of reactive oxygen species formation, for example, involving NADPH oxidases or mitochondrial activation. It also suggests that the observed genotoxic effect of the nanoparticles in the comet assay and the micronucleus assay (i.e., stronger aneugenic effect) is due to mechanisms other than oxidative DNA attack. A different mechanism of DNA damage by nanoparticles and microparticles is further suggested by measures of DNA damage from the comet and micronucleus assays. The comet assay revealed more damage in nanoparticle-exposed than in microparticle cells. In contrast, the micronucleus assay revealed slightly less centromere-negative micronuclei in nanoparticle exposed than in microparticle-exposed cells. This assay measures clastogenic, that is, double strand breakage events. Although some micronuclei in nanoparticle-exposed cells might not have been seen as a result of inhibition of cell division from greater cytotoxicity, these results point to a greater complexity of DNA damage caused by exposure to nanoparticles compared to microparticles [85]. A genotoxic effect has also described for silver nanoparticles that induced chromosomal aberrations, damage of metaphases, and aneuploidy in medaka (Oryzias latipes) cell line [86].
Further studies are needed to validate this dangerous potential effect of the nanomaterials. Obviously, close attention to safety issues will be required, also in the light of the potential interference between engineered nanomaterials and the environment.
4. Nanomaterials and Autophagy or “Autophagic Cell Death”
Autophagy is a highly conserved homeostatic process, involved in the recognition and turnover of damaged/aged proteins and organelles. During autophagy, parts of the cytoplasm are sequestered within characteristic double- or multi-membraned autophagic vacuoles (named autophagosomes) and are finally delivered to lysosomes for bulk degradation. This process is dynamically regulated by ATG (Autophagy-related gene) gene family and is finely controlled by several signalling pathways [87]. Autophagy constitutes a cytoprotective response activated by cells in the challenge to cope with stress. In this setting, pharmacological or genetic inhibition of autophagy accelerates cell death. On the basis of morphological features, the term “autophagic cell death” has widely been used to indicate instances of cell death that are accompanied by a massive cytoplasmic vacuolization [38]. The expression “autophagic cell death” is highly prone to misinterpretation and hence must be used with caution, but, discussion this problem is beyond the scope of this paper, and an excellent paper concerning this subject has been published [88]. In any case, “autophagic cell death” is used to imply that autophagy would execute the cell demise. In the literature, it has been reported that several classes of nanomaterials induce elevated levels of autophagic vacuoles in different animals and human cell culture as well as in vivo models (masterfully summarized in two recent reviews [10, 61]). Such nanomaterials include alumina, europium oxide, gadolinium oxide, gold, iron oxide, manganese, neodymium oxide, palladium, samarium oxide, silica, terbium oxide, titanium dioxide, ytterbium oxide, and yttrium oxide nanoparticles; nanoscale carbon black; fullerene and fullerene derivate; and protein-coated quantum dots. The induction of autophagy was evaluated using panoply of established methods, including the electron microscopy detection of autophagic vacuoles, the immunoblot detection of ATG expression level and/or LC3-I to LC3-II conversion (an established marker of autophagy activity) and/or cellular immunolabeling of punctate LC3-II in cytoplasmic vacuoles. These studies were performed in vivo but mainly in primary cells and/or cell lines from rat (alveolar macrophages, kidney, dopaminergic neuron, and glioma), mouse (macrophages and neuroblasts), porcine (kidney), and human (lung, oral, colon, breast, cervical and epithelial cancer cells as well as fibroblasts, peripheral blood mononuclear, and endothelial and mesenchymal stem cells). Nanomaterials may induce autophagy via an oxidative stress mechanism, such as accumulation of damaged proteins and subsequent endoplasmic reticulum or mitochondrial stress [39, 89–92] and altering gene/protein expression and/or regulation, and interfering with the kinase-mediated regulatory cascades [93–103]. The increase in autophagic vacuoles in response to nanomaterials may be an adaptive cellular response. There is evidence that autophagy can selectively compartmentalize nanomaterials. In fact, nanoparticles are commonly observed within the autophagosome compartment, suggesting that activation of autophagy is a targeted exertion to sequester and degrade these materials following entrance into the cytoplasm [104]. It is possible that the cells might perceive nanomaterials as an endosomal pathogen or an aggregation-prone protein (both commonly degraded by the autophagy machinery). Recent evidence supports ubiquitination of nanomaterials directly or indirectly via colocalization with ubiquitinated protein aggregates, suggesting that cells may indeed select nanomaterials for autophagy through a pathway similar to invading pathogens [13, 98, 105]. Additionally, ubiquitinated proteins accumulate concomitantly with nanomaterial-induced autophagic vacuoles [106].
It is important to underlie that nanoscale was a significant factor in eliciting the autophagic response. Autophagy was not induced by quantum dots that had a tendency to aggregate to microscale particles into the cells [107]. Nanoscale size dependence was also reported for neodymium oxide nanoparticle, with larger particles inducing less autophagy [108]. Apparently, modifications of the surface properties might be able to alter the autophagy-inducing activity of the nanomaterials. Cationic PAMAM dendrimers elicited autophagy more than anionic ones in vitro [94]. Carbon nanotubes with carboxylic acid group could induce autophagy, while those functionalized with poly-aminobenzene sulfonic acid and polyethylene glycol groups were not [100]. Recently, it has been published that a short synthetic peptide, RE-1, binds to lanthanide-based nanocrystals, forms a stable coating layer on the nanoparticles surface, and significantly abolishes their autophagy-inducing activity. Furthermore, the addition of an arginine-glycine-aspartic acid motif to RE-1 enhances autophagy induced by lanthanide-based nanocrystals [109].
It is also possible that nanomaterials cause a state of autophagic dysfunction, correlated with a blockade of autophagy flux, and this may be involved in their mechanism of toxicity [110, 111]. Nanoparticles could give rise to autophagy dysfunction by overloading or directly inhibiting lysosomal enzymes or disrupting cytoskeleton-mediated vesicle trafficking, resulting in diminished autophagosome-lysosome fusion [112]. Nanoparticles could also directly affect lysosomal stability by inducing lysosomal oxidative stress, alkalization, osmotic swelling, or causing detergent-like disruption of the lysosomal membrane (see the complete review of Stern and colleagues [61] about this subject). Disruption in autophagosome trafficking to the lysosome has been implicated in several human pathologies, including cancer development and progression as well as neurodegenerative diseases. As exposure to airborne pollution has been associated with Alzheimer and Parkinson-like pathologies, and nanoparticles are the primary particle number and surface area component of pollution-derived particulates, Stern and Johnson have recently postulated a relationship between nanoparticle-induced autophagy dysfunction and pollution-associated neurodegeneration [113].
Several studies have been suggested also that the nanomaterial-induced autophagy dysfunction is correlated with mitochondrial damage [102, 114–118].
In the majority of the studies, autophagosome accumulation induced by nanomaterials treatment was associated with cell death, unfortunately the possibility of autophagy inhibition was not often investigated (the block of autophagy flux and autophagy induction both can determinate autophagosome accumulation) [119], and the mechanism of nanomaterial-induced autophagy accumulation in many cases is unclear.
Interestingly, nanomaterials have been proposed also as tools to monitor autophagy [120, 121]. In conclusion, a growing body of the literature indicates that nanomaterials impact the autophagy pathways, then the possible autophagic response should be always taken into consideration in the development of novel nanomaterials systems (Figure 4). Moreover, further studies should be performed to clarify the molecular mechanisms underlying the interaction between nanomaterials and the autophagy machinery as well as to expand the knowledge of the implications and biological significance of this modulation.
5. Nanomaterials and Necrosis
Necrosis was, for a long time, considered as an accidental form of cell death, but in recent years several studies clarified that this process is regulated and may play a role in multiple physiological and pathological settings [122]. Several triggers can induce regulated necrosis, including alkylating DNA damage, excitotoxins, and the ligation of death receptors [38, 122]. Indeed, when caspases are genetically or pharmacologically inhibited, RIP1 (receptor-interacting protein kinase 1) and its homolog RIP3 are not degraded and engage in physical and functional interactions that ultimately activate the execution of necrotic cell death [38, 122]. It should be noted that RIP3-dependent and RIP1-independent cases of necrosis have been described, suggesting that there are several subprograms of regulated necrosis [38, 122–124]. In a genome-wide siRNA screen, Hitomi and colleagues elucidated the relationship between appotosis and necrosis pointing out that some components of the apoptotic pathway (e.g., the BH3-only protein Bmf) are also crucial in the necrotic machinery [125]. Moreover, recent studies provide evidence that apoptosis and necrosis are closely linked [126–128]. The term “necroptosis” has been used as a synonym of regulated necrosis, but it was originally introduced to indicate a specific case of necrosis, which is induced by death receptor ligation and can be inhibited by the RIP-1 targeting chemical necrostatin-1 [38, 122, 129].
In the literature, there are confused and inconsistent examples of necrosis induced by nanomaterials, because on one hand only the loss of cell viability is often evaluated without focalising into the cell death modalities and on the other hand, there are no single discriminative biochemical markers available yet. Moreover, it should not be underestimated that the induction of apoptosis in cell culture is inevitably followed by secondary necrosis, and this could lead to a misinterpretation of results. However, a recent study demonstrated that water-soluble germanium nanoparticles with allylamine-conjugated surfaces (4 nm) induce necrotic cell death that is not inhibited by necrostatin-1 in Chinese hamster ovary cells [130]. Although the mechanisms of ligand and surface chemistry, surface charge, and crystallinity-based toxicity are complex, studies are beginning to elucidate certain surface functional groups and properties that can effectively alter biological responses. In fact, the crystal structure, with the different forms, of nanomaterials can dictate its cytotoxic potential. Braydich-Stolle and coworkers identify that both size and crystal structure (rutile, anatase, and amorphous) of TiO2 nanoparticles affect the mechanism of cell death in mouse keratinocyte cell line [131]. They found that 100% anatase TiO2 nanoparticles induced necrosis in size-independent manner, whereas the rutile TiO2 nanoparticles elicited apoptosis. Pan and collaborators investigated the size-dependent cytotoxicity exhibited by gold nanoparticles (stabilized with triphenylphosphine derivatives) in several human cell lines. All cell types internalised gold nanoparticles and showed signs of stress. Smaller particles (<1.4 nm) were more toxic than their larger equivalents. However, 1.4 nm nanoparticles cause predominantly rapid cell death by necrosis, while closely related particles 1.2 nm in diameter affect predominantly apoptosis [132, 133]. Besides, it has been reported that small (10 nm) silver nanoparticles had a greater ability to induce apoptosis than other-sized ones (50 and 100 nm) in mouse osteoblastic cell line and induce necrosis in rat phaeochromocytoma cells [134]. The shape-dependent toxicity of polyaniline (PANI) nanomaterials with four different aspect ratios on human lung fibroblast cells was evaluated. The toxicity increased with decreasing aspect ratio of PANI nanomaterials; low aspect ratio PANI nanomaterials induced more necrosis than others [135]. Furthermore, the surface charge seems to be a major factor of how nanoparticles impact cellular processes. It has been demonstrated that charged gold nanoparticles induced cell death via apoptosis, whereas neutral nanoparticles caused necrosis [136]. Clearly, other parameters may influence the cell death modalities induced by nanomaterials, such as the dose or the time of exposure. Depending on the concentration, nano-C60 fullerene caused ROS-mediated necrosis (high dose), or ROS-independent autophagy (low dose) in rat and human glioma cell cultures [137]. The type of cell death induced by silver ions (Ag+) and silver nanoparticle coated with polyvinylpyrrolidone were also dependent on the dose and the exposure time, with Ag+ being the most toxic in a human monocytic cell line [138]. The silver nanoparticles concentrations required to elicit apoptosis were found to be much lower than the concentrations required for necrosis in human fibrosarcoma, skin, and testicular embryonal carcinoma cells [139, 140]. In conclusion, although the reports are often contradictory, the cell death appears roughly cell type, material composition, and concentration dependent. For instance, it has been reported that TiO2 (5–10 nm), SiO2 (30 nm), and MWCNTs (with different size: <8 nm, 20–30 nm, and >50 nm, but same length 0.5–2 μm) induce cell-specific responses resulting in variable toxicity and subsequent cell fate in mouse fibroblasts and macrophages as well as telomerase-immortalized human bronchiolar epithelial cells. Precisely, the macrophages were very susceptible to nanomaterial toxicity, while fibroblasts are more resistant at all the treatments, whereas only the exposure of SiO2 and MWCNT (<8 nm) induce apoptosis in human bronchiolar epithelial cells. In the experimental conditions of this study, the investigated nanomaterials did not trigger necrosis [65]. In the same mouse macrophage cell line, it has been demonstrated that MWCNT (10–25 nm) and SWCNTs (1.2–1.5 nm) induced necrosis in a concentration-dependent manner [141]. CNTs have been demonstrated to induce both necrosis and apoptosis in human fibroblasts [142]. In contrast, Cui and co-workers found that SWNTs upregulate apoptosis-associated genes in human embryo kidney cells [143], and Zhu and colleagues showed that MWCNTs induce apoptosis in mouse embryonic stem cells [144], while Pulskamp and collaborators assert that commercial CNTs do not induce necrosis or apoptosis in rat macrophages [145]. Recently, a multilevel approach, including different toxicity tests and gene-expression determinations, was used to evaluate the toxicity of two lanthanide-based luminescent nanoparticles, complexes with the chelating agent EDTA. The study revealed that these nanomaterials induced necrosis in human lymphoblasts and erythromyeloblastoid leukemia cell lines, while no toxicity was observed in human breast cancer cell line. Moreover, no in vivo effects have been observed. The comparative analysis of the nanomaterials and their separated components showed that the toxicity was mainly due to the presence of EDTA [146].
The knowledge advances concerning the molecular characterization of necrosis will make necessary more precise and accurate studies to confirm the ways in which nanomaterials might cause necrotic death.
6. Nanomaterials and Pyroptosis
Pyroptosis described the peculiar death of macrophages infected by Salmonella typhimurium [147]. Several other bacteria triggering this atypical cell death modality have been identified. Pyroptosis neither constitutes a macrophage-specific process nor a cell death subroutine that only results from bacterial infection. Pyroptotic cells can exhibit apoptotic and/or necrotic morphological features. The most distinctive biochemical feature of pyroptosis is the early caspase-1 activation associated with the generation of pyrogenic mediators, such as Interleukin-1β (IL-1β) [38].
Recently, it has been shown that the exposure of macrophages (both a mouse macrophage cell line and primary human alveolar macrophages) to carbon black nanoparticles resulted in inflammasome activation as defined by cleavage of caspase-1 to its active form and downstream IL-1β release. The carbon black nanoparticles-induced cell death was identified as pyroptosis through the inhibition of caspase-1 and pyroptosis by specific pharmacological inhibitors. The authors showed that, in this setting, TiO2 particles did not induce pyroptosis or significantly activate the inflammasome [148]. In contrast, it has been shown that nano-TiO2 and nano-SiO2, but not nano-ZnO (zinc oxide) and carbon nanotubes, induced inflammasome activation but not cell death in murine bone marrow-derived macrophages and human macrophages cell line. Although the caspase-1 cleavage and IL-1β release was induced, the inflammation caused by nanoparticles was largely caused by the biological effect of IL-1α [149]. This apparent discrepancy could be explained considering the different concentration and kind of nanomaterials used in these studies; moreover, it is possible that different macrophages perform differently in response to nanomaterials. Future studies should address this issue. However, the identification of pyroptosis as a cellular response to carbon nanoparticles exposure is novel and relates to health impacts of carbon-based particulates.
7. Conclusions and Perspectives
The continued expansion of the nanotechnology field requires a thorough understanding of the potential mechanisms of nanomaterial toxicity for proper safety assessment and identification of exposure biomarkers. With increasing research into nanomaterial safety, details on the biological effects of nanomaterials have begun to emerge. The nanomaterials intrinsic toxicity has been attributed to their physicochemical characteristics, that is, their smallness and the remarkably large surface area per unit mass and high surface reactivity. In fact, their type, composition and modifications, size, shape, and surface charge should be considered. However, the complex death paradigms may also be explained by activation of different death pathways in a context-dependent manner. In vitro experiments could be influenced by a cell type-specific response, and ones in vivo could be affected by the animal species and the model used or by pharmacokinetic parameters (administration, distribution, metabolism, etc.). Moreover, the dose, concentrations, and the time of exposure of a nanomaterial employed are essential. In effect, the efficiency of cellular uptake of nanomaterials and the resultant intracellular concentration may determine the cytotoxic potential. Elucidating the molecular mechanisms by which nanosized particles induce activation of cell death signalling pathways will be critical for the development of prevention strategies to minimize the cytotoxicity of nanomaterials. Unfortunately, in the literature, there are many conflicting data; the most plausible reason is certainly the discrepancy of nanomaterials and experimental models engaged. Although some authors have recently alerted colleagues on these issues [3, 5, 8, 9, 150–152], it has not yet been put in place a guideline, generally accepted by the scientific community in the field, to address these matters. In fact, harmonization of protocols for material characterization and for cytotoxicity testing of nanomaterials is needed. In addition, parallel profiling of several classes of nanomaterials, combined with detailed characterization of their physicochemical properties, could provide a model for safety assessment of novel nanomaterials [153]. During the past decade, owing to major technological advances in the field of combinatorial chemistry in addition to the sequencing of an ever increasing number of genomes, high-content chemical and genetic libraries have become available, raising the need for high-throughput screening (HTS) and high-content screening (HCS) approaches. In response to this demand, multiple conventional cell death detection methods have been adapted to HTS/HCS, and many novel HTS/HCS-amenable techniques have been developed [37, 154]. In the last years, several authors started to study the nanotoxicity with this tools and highlighted the potential of these approaches [9, 60, 75, 155–161]. An overall aim should identify HTS/HCS assays that can be used routinely to screen nanomaterials for interaction with the cell death modalities system. HTS/HCS may accelerated the analysis on a scale that commensurates with the rate of expansion of new nanomaterials but in any case is a first validation step, then it remains to confirm whether the same identified mechanisms in vitro are responsible for their in vivo toxicity. In conclusion, a multilevel-integrated uniform and consistent approach should contemplate for nanomaterial toxicity characterization.
In spite of the recent advances in our understanding of cell death mechanisms and associated signalling networks, much work remains to be done before we can fully elucidate the toxicological behaviour of the nanomaterials as well as understand their participation in the determination of cell fate. More and accurate results are needed for apoptosis, autophagy, and necrosis induction by nanomaterials; further studies are necessary to test if the novel strategic targets identified could be affected either directly or indirectly by nanomaterials. Moreover, no data are present in the literature concerning the nanomaterials exposure and other forms of cell death including anoikis, entosis, parthanatos, netosis, and cornification. For example, although numerous studies have been performed on keratinocytes, none of these has rated cornification, a cell death subroutine restricted to keratinocytes and functionally linked to the generation of the stratum corneum of the epidermis [38]. It will be of considerable interest to establish whether these various cell death modalities are associated with the intent of identifying a structure-activity relationship and delineating the mechanisms by which these interactions occur. In addition to the established paradigms of nanomaterials toxicity, the study of their interactions with the death signalling pathways could potentially have many important human pathological outcomes, including cancer, metabolic disorders, and neurodegenerative disorders.
AbbreviationsAg+:
Silver ions
ATG:
Autophagy-related gene
Bcl-2:
B-cell lymphoma 2
BH3:
Bcl-2 homology domain 3
BID:
BH3-interacting domain death agonist
Bmf:
Bcl-2-modifying factor
CNTs:
Carbon nanotubes
CoCr:
Cobalt-chrome
DNA:
Deoxyribonucleic acid
EDTA:
Ethylenediaminetetraacetic acid
ER:
Endoplasmic reticulum
FDA:
Food and Drug Administration
HCS:
High-content screening
HTS:
High-throughput screening
IL:
Interleukin
MOMP:
Mitochondrial outer membrane permeabilization
MWCNTs:
Multiwall carbon nanotubes
NADPH:
Nicotinamide adenine dinucleotide phosphate
NCCD:
Nomenclature Committee on Cell Death
PAMAM:
Cationic polyamidoamine
PANI:
Polyaniline
PEG-PE:
Poly(ethylene glycol)-phosphoethanolamine
RIP:
Receptor-interacting protein kinase
RNA:
Ribonucleic acid
RNS:
Reactive nitrogen species
ROS:
Reactive oxygen species
SiO2:
Silicon dioxide
siRNA:
Small interfering RNA
SWCNTs:
Single-walled carbon nanotubes
tBID:
Truncated BID
TiO2:
Titanium dioxide
ZnO:
Zinc oxide.
Conflict of Interests
The authors declare that they have no conflict of interests.
Acknowledgment
This work is supported by the Italian Ministry of the University and Scientific Research.
OberdörsterG.Nanotoxicology: in vitro-in vivo dosimetry2012120113GangwalS.BrownJ.WangA.HouckK.A.DixD.J.Informing selection of nanomaterial concentrations for ToxCast in vitro testing based on occupational exposure potential20111191115391546NelA.XiaT.MädlerL.LiN.Toxic potential of materials at the nanolevel200631157616226272-s2.0-3194445123210.1126/science.1114397XiaT.LiN.NelA. E.Potential health impact of nanoparticles2009301371502-s2.0-6554910324810.1146/annurev.publhealth.031308.100155PetersenE. J.NelsonB. C.Mechanisms and measurements of nanomaterial-induced oxidative damage to DNA201039826136502-s2.0-7795787561410.1007/s00216-010-3881-7ShvedovaA. A.KaganV. E.FadeelB.Close encounters of the small kind: adverse effects of man-made materials interfacing with the nano-cosmos of biological systems20105063882-s2.0-7194910261810.1146/annurev.pharmtox.010909.105819OrreniusS.NicoteraP.ZhivotovskyB.Cell death mechanisms and their implications in toxicology201111913192-s2.0-7865052741610.1093/toxsci/kfq268HorieM.KatoH.FujitaK.EndohS.IwahashiH.In vitro evaluation of cellular response induced by manufactured nanoparticles2012253605619ShvedovaA. A.PietroiustiA.FadeelB.KaganV. E.Mechanisms of carbon nanotube-induced toxicity: focus on oxidative stress20122612121133AndónF. T.FadeelB.Programmed cell death: molecular mechanisms and implications for safety assessment of nanomaterialsAccounts of Chemical Research. In pressJonesC. F.GraingerD. W.In vitro assessments of nanomaterial toxicity20096164384562-s2.0-6574908749110.1016/j.addr.2009.03.005NabievI.MitchellS.DaviesA.WilliamsY.KelleherD.MooreR.Gun'koY. K.ByrneS.RakovichY. P.DoneganJ. F.SukhanovaA.ConroyJ.CottellD.GaponikN.RogachA.VolkovY.Nonfunctionalized nanocrystals can exploit a cell's active transport machinery delivering them to specific nuclear and cytoplasmic compartments2007711345234612-s2.0-3674905520910.1021/nl0719832ChenM.Von MikeczA.Formation of nucleoplasmic protein aggregates impairs nuclear function in response to SiO2 nanoparticles2005305151622-s2.0-1504435736210.1016/j.yexcr.2004.12.021TsoliM.KuhnH.BrandauW.EscheH.SchmidG.Cellular uptake and toxicity of Au55 clusters200518-98418442-s2.0-3364675264210.1002/smll.200500104SchrandA. M.Braydich-StolleL. K.SchlagerJ. J.DaiL.HussainS. M.Can silver nanoparticles be useful as potential biological labels?200819232-s2.0-4494923606810.1088/0957-4484/19/23/235104235104HussainS. M.Braydich-StolleL. K.SchrandA. M.MurdockR. C.YuK. O.MattieD. M.SchlagerJ. J.Toxicity evaluation for safe use of nanomaterials: recent achievements and technical challenges20092116154915592-s2.0-6614915174310.1002/adma.200801395OberdorsterG.FerinJ.LehnertB. E.Correlation between particle size, in vivo particle persistence, and lung injury199410251731792-s2.0-0028104529MonteillerC.TranL.MacNeeW.FauxS.JonesA.MillerB.DonaldsonK.The pro-inflammatory effects of low-toxicity low-solubility particles, nanoparticles and fine particles, on epithelial cells in vitro: the role of surface area20076496096152-s2.0-3454836646610.1136/oem.2005.024802ConnorE. E.MwamukaJ.GoleA.MurphyC. J.WyattM. D.Gold nanoparticles are taken up by human cells but do not cause acute cytotoxicity2005133253272-s2.0-2544444809810.1002/smll.200400093KaganV. E.TyurinaY. Y.TyurinV. A.KonduruN. V.PotapovichA. I.OsipovA. N.KisinE. R.Schwegler-BerryD.MercerR.CastranovaV.ShvedovaA. A.Direct and indirect effects of single walled carbon nanotubes on RAW 264.7 macrophages: role of iron20061651881002-s2.0-3374497140010.1016/j.toxlet.2006.02.001CedervallT.LynchI.LindmanS.BerggårdT.ThulinE.NilssonH.DawsonK. A.LinseS.Understanding the nanoparticle-protein corona using methods to quntify exchange rates and affinities of proteins for nanoparticles20071047205020552-s2.0-3384778914210.1073/pnas.0608582104HorieM.NishioK.FujitaK.EndohS.MiyauchiA.SaitoY.IwahashiH.YamamotoK.MurayamaH.NakanoH.NanashimaN.NikiE.YoshidaY.Protein adsorption of ultrafine metal oxide and its influence on cytotoxicity toward cultured cells20092235435532-s2.0-6594910121810.1021/tx800289zEhrenbergM. S.FriedmanA. E.FinkelsteinJ. N.OberdörsterG.McGrathJ. L.The influence of protein adsorption on nanoparticle association with cultured endothelial cells20093046036102-s2.0-5644912242410.1016/j.biomaterials.2008.09.050HorieM.NishioK.KatoH.FujitaK.EndohS.NakamuraA.MiyauchiA.KinugasaS.YamamotoK.NikiE.YoshidaY.HagiharaY.IwahashiH.Cellular responses induced by cerium oxide nanoparticles: induction of intracellular calcium level and oxidative stress on culture cells20111504461471LundqvistM.StiglerJ.CedervallT.BerggårdT.FlanaganM. B.LynchI.EliaG.DawsonK.The evolution of the protein corona around nanoparticles: a test study20115975037509MonopoliM. P.WalczykD.CampbellA.EliaG.LynchI.Baldelli BombelliF.DawsonK. A.Physical-Chemical aspects of protein corona: relevance to in vitro and in vivo biological impacts of nanoparticles20111338252525342-s2.0-7995230251210.1021/ja107583hDuttaD.SundaramS. K.TeeguardenJ. G.RileyB. J.FifieldL. S.JacobsJ. M.AddlemanS. R.KaysenG. A.MoudgilB. M.WeberT. J.Adsorbed proteins influence the biological activity and molecular targeting of nanomaterials200710013033152-s2.0-3544899022610.1093/toxsci/kfm217LewinskiN.ColvinV.DrezekR.Cytotoxicity of nanopartides20084126492-s2.0-3884911181810.1002/smll.200700595SternS. T.McNeilS. E.Nanotechnology safety concerns revisited200810114212-s2.0-3694903946210.1093/toxsci/kfm169ChangE.ThekkekN.YuW. W.ColvinV. L.DrezekR.Evaluation of quantum dot cytotoxicity based on intracellular uptake2006212141214172-s2.0-3375124591710.1002/smll.200600218SayesC. M.WahiR.KurianP. A.LiuY.WestJ. L.AusmanK. D.WarheitD. B.ColvinV. L.Correlating nanoscale titania structure with toxicity: a cytotoxicity and inflammatory response study with human dermal fibroblasts and human lung epithelial cells20069211741852-s2.0-3374570084110.1093/toxsci/kfj197JonesG.BrooksP. M.Injectable gold compounds: an overview19963511115411582-s2.0-0029910578SchipperM. L.Nakayama-RatchfordN.DavisC. R.KamN. W. S.ChuP.LiuZ.SunX.DaiH.GambhirS. S.A pilot toxicology study of single-walled carbon nanotubes in a small sample of mice2008342162212-s2.0-4184912645410.1038/nnano.2008.68AillonK. L.XieY.El-GendyN.BerklandC. J.ForrestM. L.Effects of nanomaterial physicochemical properties on in vivo toxicity20096164574662-s2.0-6564915137510.1016/j.addr.2009.03.010BuzeaC.PachecoI. I.RobbieK.Nanomaterials and nanoparticles: sources and toxicity200724MR17MR71BrownJ. M.AttardiL. D.The role of apoptosis in cancer development and treatment response2005532312372-s2.0-1464440752510.1038/nrc1570KeppO.GalluzziL.LipinskiM.YuanJ.KroemerG.Cell death assays for drug discovery20111032212372-s2.0-7995212294410.1038/nrd3373GalluzziL.VitaleI.AbramsJ. M.Molecular definitions of cell death subroutines: recommendations of the Nomenclature Committee on cell death2012191107120LiN.XiaT.NelA. E.The role of oxidative stress in ambient particulate matter-induced lung diseases and its implications in the toxicity of engineered nanoparticles2008449168916992-s2.0-4154912939210.1016/j.freeradbiomed.2008.01.028SarkarA.DasJ.MannaP.SilP. C.Nano-copper induces oxidative stress and apoptosis in kidney via both extrinsic and intrinsic pathways20112902-3208217MannaP.GhoshM.GhoshJ.DasJ.SilP. C.Contribution of nano-copper particles to in vivo liver dysfunction and cellular damage: role of IêBá/NF-êB, MAPKs and mitochondrial signal201261121ZhaoJ.BowmanL.ZhangX.ShiX.JiangB.CastranovaV.DingM.Metallic nickel nano- and fine particles induce JB6 cell apoptosis through a caspase-8/AIF mediated cytochrome c-independent pathway20097, article 22-s2.0-6544913328810.1186/1477-3155-7-2SiddiquiM. A.AhamedM.AhmadJ.Majeed KhanM. A.MusarratJ.Al-KhedhairyA. A.AlrokayanS. A.Nickel oxide nanoparticles induce cytotoxicity, oxidative stress and apoptosis in cultured human cells that is abrogated by the dietary antioxidant curcumin2012503-4641647AhamedM.AkhtarM. J.SiddiquiM. A.AhmadJ.MusarratJ.Al-KhedhairyA. A.AlSalhiM. S.AlrokayanS. A.Oxidative stress mediated apoptosis induced by nickel ferrite nanoparticles in cultured A549 cells20112832-31011082-s2.0-7995490019410.1016/j.tox.2011.02.010FubiniB.HubbardA.Reactive oxygen species (ROS) and reactive nitrogen species (RNS) generation by silica in inflammation and fibrosis20033412150715162-s2.0-003835974010.1016/S0891-5849(03)00149-7WangL.BowmanL.LuY.RojanasakulY.MercerM. R.CastranovaY.DingM.Essential role of p53 in silica-induced apoptosis20052883L488L4962-s2.0-1364426922810.1152/ajplung.00123.2003YooK. C.YoonC. H.KwonD.Titanium dioxide induces apoptotic cell death through reactive oxygen species-mediated Fas upregulation and Bax activation2012712031214KangS. J.KimB. M.HongS. H.ChungH. W.Titanium dioxide nanoparticles induce apoptosis through the JNK/p38-caspase-8-Bid pathway in phytohemagglutinin-stimulated human lymphocytes200938646826872-s2.0-6765045763010.1016/j.bbrc.2009.06.097ShiY.WangF.HeJ.YadavS.WangH.Titanium dioxide nanoparticles cause apoptosis in BEAS-2B cells through the caspase 8/t-Bid-independent mitochondrial pathway2010196121272-s2.0-7795274152710.1016/j.toxlet.2010.03.014KangS. J.KimB. M.LeeY. J.ChungH. W.Titanium dioxide nanoparticles trigger p53-mediated damage response in peripheral blood lymphocytes20084953994052-s2.0-4584912831610.1002/em.20399ParkE. J.YiJ.ChungK. H.RyuD. Y.ChoiJ.ParkK.Oxidative stress and apoptosis induced by titanium dioxide nanoparticles in cultured BEAS-2B cells200818032222292-s2.0-4974913161210.1016/j.toxlet.2008.06.869XiaT.KovochichM.BrantJ.HotzeM.SempfJ.OberleyT.SioutasC.YehJ. I.WiesnerM. R.NelA. E.Comparison of the abilities of ambient and manufactured nanoparticles to induce cellular toxicity according to an oxidative stress paradigm200668179418072-s2.0-3374831079710.1021/nl061025kDingL.StilwellJ.ZhangT.ElboudwarejO.JiangH.SelegueJ. P.CookeP. A.GrayJ. W.ChenF. F.Molecular characterization of the cytotoxic mechanism of multiwall carbon nanotubes and nano-onions on human skin fibroblast2005512244824642-s2.0-3074443214110.1021/nl051748oBottiniM.BrucknerS.NikaK.BottiniN.BellucciS.MagriniA.BergamaschiA.MustelinT.Multi-walled carbon nanotubes induce T lymphocyte apoptosis200616021211262-s2.0-2764444361310.1016/j.toxlet.2005.06.020GrabinskiC.HussainS.LafdiK.Braydich-StolleL.SchlagerJ.Effect of particle dimension on biocompatibility of carbon nanomaterials20074514282828352-s2.0-3604899112910.1016/j.carbon.2007.08.039SrivastavaR. K.PantA. B.KashyapM. P.KumarV.LohaniM.JonasL.RahmanQ.Multi-walled carbon nanotubes induce oxidative stress and apoptosis in human lung cancer cell line-A5492011521952072-s2.0-7995283645410.3109/17435390.2010.503944ChłopekJ.CzajkowskaB.SzaraniecB.FrackowiakE.SzostakK.BéguinF.In vitro studies of carbon nanotubes biocompatibility2006446110611112-s2.0-3214445676610.1016/j.carbon.2005.11.022ThurnherrT.BrandenbergerC.FischerK.DienerL.ManserP.Maeder-AlthausX.KaiserJ. P.KrugH. F.Rothen-RutishauserB.WickP.A comparison of acute and long-term effects of industrial multiwalled carbon nanotubes on human lung and immune cells in vitro201120031761862-s2.0-7865108063210.1016/j.toxlet.2010.11.012WangL.LuanpitpongS.CastranovaV.TseW.LuY.PongrakhananonV.RojanasakulY.Carbon nanotubes induce malignant transformation and tumorigenesis of human lung epithelial cells2011117279628032-s2.0-7996026538410.1021/nl2011214TyurinaY. Y.KisinE. R.MurrayA.Global phospholipidomics analysis reveals selective pulmonary peroxidation profiles upon inhalation of single-walled carbon nanotubes20115973427353SternS. T.AdiseshaiahP. P.CristR. M.Autophagy and lysosomal dysfunction as emerging mechanisms of nanomaterial toxicity20129120ÈesenM. H.PeganK.SpesA.TurkB.Lysosomal pathways to cell death and their therapeutic applications20123181112451251RepnikU.StokaV.TurkV.TurkB.Lysosomes and lysosomal cathepsins in cell death2012182412233TaharaY.NakamuraM.YangM.ZhangM.IijimaS.YudasakaM.Lysosomal membrane destabilization induced by high accumulation of single-walled carbon nanohorns in murine macrophage RAW 264.7201233927622769SohaebuddinS. K.ThevenotP. T.BakerD.EatonJ. W.TangL.Nanomaterial cytotoxicity is composition, size, and cell type dependent201021722HussainS.ThomassenL. C. J.FerecatuI.BorotM. C.AndreauK.MartensJ. A.FleuryJ.Baeza-SquibanA.MaranoF.BolandS.Carbon black and titanium dioxide nanoparticles elicit distinct apoptotic pathways in bronchial epithelial cells20107, article 102-s2.0-7795080572610.1186/1743-8977-7-10JinC. Y.ZhuB. S.WangX. F.LuQ. H.Cytotoxicity of titanium dioxide nanoparticles in mouse fibroblast cells2008219187118772-s2.0-5354913170110.1021/tx800179fXiaT.KovochichM.LiongM.ZinkJ. I.NelA. E.Cationic polystyrene nanosphere toxicity depends on cell-specific endocytic and mitochondrial injury pathways20082185962-s2.0-4264909967010.1021/nn700256cThomasT. P.MajorosI.KotlyarA.MullenD.Banaszak HollM. M.BakerJ. R.Cationic poly(amidoamine) dendrimer induces lysosomal apoptotic pathway at therapeutically relevant concentrations20091012320732142-s2.0-7244921231010.1021/bm900683rThibodeauM. S.GiardinaC.KnechtD. A.HelbleJ.HubbardA. K.Silica-induced apoptosis in mouse alveolar macrophages is initiated by lysosomal enzyme activity200480134482-s2.0-324280819310.1093/toxsci/kfh121TedescoS.DoyleH.BlascoJ.RedmondG.SheehanD.Oxidative stress and toxicity of gold nanoparticles in Mytilus edulis201010021781862-s2.0-7804950868010.1016/j.aquatox.2010.03.001TabasI.RonD.Integrating the mechanisms of apoptosis induced by endoplasmic reticulum stress20111331841902-s2.0-7995226401110.1038/ncb0311-184GormanA. M.HealyS. J.JägerR.SamaliA.Stress management at the ER: regulators of ER stress-induced apoptosis20121343306316ZhangR.PiaoM. J.KimK. C.KimA. D.ChoiJ. Y.ChoiJ.HyunJ. W.Endoplasmic reticulum stress signaling is involved in silver nanoparticles-induced apoptosis2012441224232TsaiY. Y.HuangY. H.ChaoY. L.Identification of the nanogold particle-induced endoplasmic reticulum stress by omic techniques and systems biology analysis201151293549369WangJ.FangX.LiangW.Pegylated phospholipid micelles induce endoplasmic reticulum-dependent apoptosis of cancer cells but not normal cells20126650185030ThubagereA.ReinhardB. M.Nanoparticle-induced apoptosis ropagates through hydrogen-peroxide-mediated bystander killing: insights from a human intestinal epithelium in vitro model201047361136222-s2.0-7795554372010.1021/nn100389aVitaleI.GalluzziL.CastedoM.KroemerG.Mitotic catastrophe: a mechanism for avoiding genomic instability20111263853922-s2.0-7996095708510.1038/nrm3115PorterA. E.GassM.MullerK.SkepperJ. N.MidgleyP. A.WellandM.Direct imaging of single-walled carbon nanotubes in cells20072117137172-s2.0-3594897283210.1038/nnano.2007.347GonzalezL.DecordierI.Kirsch-VoldersM.Induction of chromosome malsegregation by nanomaterials2010386169116972-s2.0-7864975411610.1042/BST0381691SargentL. M.ShvedovaA. A.HubbsA. F.SalisburyJ. L.BenkovicS. A.KashonM. L.LowryD. T.MurrayA. R.KisinE. R.FriendS.McKinstryK. T.BattelliL.ReynoldsS. H.Induction of aneuploidy by single-walled carbon nanotubes20095087087172-s2.0-7034992109810.1002/em.20529SargentL. M.ReynoldsS. H.CastranovaV.Potential pulmonary effects of engineered carbon nanotubes: in vitro genotoxic effects2010443964082-s2.0-7795793150210.3109/17435390.2010.500444SargentL. M.HubbsA. F.YoungS. H.Single-walled carbon nanotube-induced mitotic disruption20127451-22837TsaousiA.JonesE.CaseC. P.The in vitro genotoxicity of orthopaedic ceramic (Al2O3) and metal (CoCr alloy) particles20106971-2192-s2.0-7794949140410.1016/j.mrgentox.2010.01.012PapageorgiouI.BrownC.SchinsR.SinghS.NewsonR.DavisS.FisherJ.InghamE.CaseC. P.The effect of nano- and micron-sized particles of cobalt-chromium alloy on human fibroblasts in vitro20072819294629582-s2.0-3414722385510.1016/j.biomaterials.2007.02.034WiseJ. P.GoodaleB. C.WiseS. S.CraigG. A.PonganA. F.WalterR. B.ThompsonW. D.NgA. K.AboueissaA. M.MitaniH.SpaldingM. J.MasonM. D.Silver nanospheres are cytotoxic and genotoxic to fish cells201097134412-s2.0-7754908485310.1016/j.aquatox.2009.11.016KlionskyD. J.The molecular machinery of autophagy and its role in physiology and disease20102176632-s2.0-7795617346610.1016/j.semcdb.2010.04.005KroemerG.LevineB.Autophagic cell death: the story of a misnomer2008912100410102-s2.0-5674917067710.1038/nrm2529ZhangQ.YangW.ManN.ZhengF.ShenY.SunK.LiY.WenL. P.Autophagy-mediated chemosensitization in cancer cells by fullerene C60 nanocrystal200958110711172-s2.0-7344913874510.4161/auto.5.8.9842LiJ. J.HartonoD.OngC. N.BayB. H.YungL. Y. L.Autophagy and oxidative stress associated with gold nanoparticles20103123599660032-s2.0-7795381175510.1016/j.biomaterials.2010.04.014Halamoda KenzaouiB.Chapuis BernasconiC.Guney-AyraS.Juillerat-JeanneretL.Induction of oxidative stress, lysosome activation and autophagy by nanoparticles in human brain-derived endothelial cells20124413813821MarkovicZ. M.RisticB. Z.ArsikinK. M.Graphene quantum dots as autophagy-inducing photodynamic agents2012332970847092SternS. T.ZolnikB. S.McLelandC. B.ClogstonJ.ZhengJ.McNeilS. E.Induction of autophagy in porcine kidney cells by quantum dots: a common cellular response to nanomaterials?200810611401522-s2.0-5434908457710.1093/toxsci/kfn137LiC.LiuH.SunY.WangH.GuoF.RaoS.DengJ.ZhangY.MiaoY.GuoC.MengJ.ChenX.LiL.LiD.XuH.WangH.LiB.JiangC.PAMAM nanoparticles promote acute lung injury by inducing autophagic cell death through the Akt-TSC2-mTOR signaling pathway20091137452-s2.0-7514912900710.1093/jmcb/mjp002YuL.LuY.ManN.YuS. H.WenL. P.Rare earth oxide nanocrystals induce autophagy in hela cells2009524278427872-s2.0-7384909546010.1002/smll.200901714ManN.YuL.YuS. H.WenL. P.Rare earth oxide nanocrystals as a new class of autophagy inducers2010623103112-s2.0-7795349829110.4161/auto.6.2.11138LeeC. M.HuangS. T.HuangS. H.LinH. W.TsaiH. P.WuJ. Y.LinC. M.ChenC. T.C60 fullerene-pentoxifylline dyad nanoparticles enhance autophagy to avoid cytotoxic effects caused by the β-amyloid peptide2011711071142-s2.0-7875170330910.1016/j.nano.2010.06.009LiH.LiY.JiaoJ.HuH. M.Alpha-alumina nanoparticles induce efficient autophagy-dependent cross-presentation and potent antitumour response2011610645650LiuH. L.ZhangY. L.YangN.ZhangY. X.LiuX. Q.LiC. G.ZhaoY.WangY. G.ZhangG. G.YangP.GuoF.SunY.JiangC. Y.A functionalized single-walled carbon nanotube-induced autophagic cell death in human lung cells through Akt-TSC2-mTOR signaling2011192, article e159YuJ. X.LiT. H.Distinct biological effects of different nanoparticles commonly used in cosmetics and medicine coatings20111911RealeM.VianaleG.LottiL. V.Effects of palladium nanoparticles on the cytokine release from peripheral blood mononuclear cells of palladium-sensitized women201153910541060KhanM. I.MohammadA.PatilG.NaqviS.A.ChauhanL. K.AhmadI.Induction of ROS, mitochondrial damage and autophagy in lung epithelial cancer cells by iron oxide nanoparticles201233514771488SunT.YanY.ZhaoY.GuoF.JiangC.Copper oxide nanoparticles induce autophagic cell death in a549 cells201278e43442YokoyamaT.TamJ.KurodaS.EGFR-targeted hybrid plasmonic magnetic nanoparticles synergistically induce autophagy and apoptosis in non-small cell lung cancer cells2011611e25507CalzolaiL.FranchiniF.GillilandD.RossiF.Protein-nanoparticle interaction: identification of the ubiquitin-gold nanoparticle interaction site2010108310131052-s2.0-7795556256510.1021/nl101746vYamawakiH.IwaiN.Cytotoxicity of water-soluble fullerene in vascular endothelial cells20062906C1495C15022-s2.0-3374478676810.1152/ajpcell.00481.2005SeleverstovO.ZabirnykO.ZscharnackM.BulavinaL.NowickiM.HeinrichJ. M.YezhelyevM.EmmrichF.O'ReganR.BaderA.Quantum dots for human mesenchymal stem cells labeling, a size-dependent autophagy activation2006612282628322-s2.0-3384637884410.1021/nl0619711ChenY.YangL.FengC.WenL. P.Nano neodymium oxide induces massive vacuolization and autophagic cell death in non-small cell lung cancer NCI-H460 cells2005337152602-s2.0-2584449371410.1016/j.bbrc.2005.09.018ZhangY.ZhengF.YangT.Tuning the autophagy-inducing activity of lanthanide-based nanocrystals through specific surface-coating peptides2012119817826WeiP.ZhangL.LuY.ManN.WenL.C60(Nd) nanoparticles enhance chemotherapeutic susceptibility of cancer cells by modulation of autophagy201021492-s2.0-7865010290410.1088/0957-4484/21/49/495101495101MaX.WuY.JinS.Gold nanoparticles induce autophagosome accumulation through size-dependent nanoparticle uptake and lysosome impairment201151186298639Johnson-LylesD. N.PeifleyK.LockettS.NeunB. W.HansenM.ClogstonJ.SternS. T.McNeilS. E.Fullerenol cytotoxicity in kidney cells is associated with cytoskeleton disruption, autophagic vacuole accumulation, and mitochondrial dysfunction201024832492582-s2.0-7795722747210.1016/j.taap.2010.08.008SternS. T.JohnsonD. N.Role for nanomaterial-autophagy interaction in neurodegenerative disease200848109711002-s2.0-58149084243MonickM. M.PowersL. S.WaltersK.LovanN.ZhangM.GerkeA.HansdottirS.HunninghakeG. W.Identification of an autophagy defect in smokers' alveolar macrophages20101859542554352-s2.0-7814947630210.4049/jimmunol.1001603Afeseh NgwaH.KanthasamyA.GuY.FangN.AnantharamV.KanthasamyA. G.Manganese nanoparticle activates mitochondrial dependent apoptotic signaling and autophagy in dopaminergic neuronal cells20112563227240HerdH. L.MaluginA.GhandehariH.Silica nanoconstruct cellular toleration threshold in vitro2011153140482-s2.0-7996010862110.1016/j.jconrel.2011.02.017WuY. N.YangL. X.ShiX. Y.LiI. C.BiazikJ. M.RatinacK. R.ChenD. H.ThordarsonP.ShiehD. B.BraetF.The selective growth inhibition of oral cancer by iron core-gold shell nanoparticles through mitochondria-mediated autophagy20113220456545732-s2.0-7995552337910.1016/j.biomaterials.2011.03.006EidiH.JoubertO.NémosC.Drug delivery by polymeric nanoparticles induces autophagy in macrophages20124221-2495503BarthS.GlickD.MacleodK. F.Autophagy: assays and artifacts201022121171242-s2.0-7795276689110.1002/path.2694SeleverstovO.PhangJ. M.ZabirnykO.Chapter 18 semiconductor nanocrystals in autophagy research. Methodology improvement at nanosized scale20094512772962-s2.0-5924909335010.1016/S0076-6879(08)03618-5ChoiK. M.NamH. Y.NaJ. H.A monitoring method for Atg4 activation in living cells using peptide-conjugated polymeric nanoparticles20117910521062VandenabeeleP.GalluzziL.Vanden BergheT.KroemerG.Molecular mechanisms of necroptosis: an ordered cellular explosion201011107007142-s2.0-7795710597710.1038/nrm2970ZhangD. W.ShaoJ.LinJ.ZhangN.LuB. J.LinS. C.DongM. Q.HanJ.RIP3, an energy metabolism regulator that switches TNF-induced cell death from apoptosis to necrosis200932559383323362-s2.0-6765081233210.1126/science.1172308UptonJ. W.KaiserW. J.MocarskiE. S.Virus inhibition of RIP3-dependent necrosis2010743023132-s2.0-7795459396510.1016/j.chom.2010.03.006HitomiJ.ChristoffersonD. E.NgA.YaoJ.DegterevA.XavierR. J.YuanJ.Identification of a molecular signaling network that regulates a cellular necrotic cell death pathway20081357131113232-s2.0-5764918139110.1016/j.cell.2008.10.044KaiserW. J.UptonJ. W.LongA. B.Livingston-RosanoffD.Daley-BauerL. P.HakemR.CasparyT.MocarskiE. S.RIP3 mediates the embryonic lethality of caspase-8-deficient mice201147173383683722-s2.0-7995281180410.1038/nature09857OberstA.DillonC. P.WeinlichR.McCormickL. L.FitzgeraldP.PopC.HakemR.SalvesenG. S.GreenD. R.Catalytic activity of the caspase-8-FLIP L complex inhibits RIPK3-dependent necrosis201147173383633672-s2.0-7995281002410.1038/nature09852ZhangH.ZhouX.McQuadeT.LiJ.ChanF. K. M.ZhangJ.Functional complementation between FADD and RIP1 in embryos and lymphocytes201147173383733762-s2.0-7995278050510.1038/nature09878DegterevA.HuangZ.BoyceM.LiY.JagtapP.MizushimaN.CunyG. D.MitchisonT. J.MoskowitzM. A.YuanJ.Chemical inhibitor of nonapoptotic cell death with therapeutic potential for ischemic brain injury2005121121192-s2.0-3364484069310.1038/nchembio711MaY. H.HuangC. P.TsaiJ. S.ShenM. Y.LiY. K.LinL. Y.Water-soluble germanium nanoparticles cause necrotic cell death and the damage can be attenuated by blocking the transduction of necrotic signaling pathway20112073258269Braydich-StolleL. K.SchaeublinN. M.MurdockR. C.JiangJ.BiswasP.SchlagerJ. J.HussainS. M.Crystal structure mediates mode of cell death in TiO2 nanotoxicity2009116136113742-s2.0-6814916871210.1007/s11051-008-9523-8PanY.NeussS.LeifertA.FischlerM.WenF.SimonU.SchmidG.BrandauW.Jahnen-DechentW.Size-dependent cytotoxicity of gold nanoparticles2007311194119492-s2.0-3604901587810.1002/smll.200700378PanY.LeifertA.RuauD.NeussS.BornemannJ.SchmidG.BrandauW.SimonU.Jahnen-DechentW.Gold nanoparticles of diameter 1.4 nm trigger necrosis by oxidative stress and mitochondrial damage2009518206720762-s2.0-7034947088810.1002/smll.200900466KimT. H.KimM.ParkH. S.ShinU. S.GongM. S.KimH. W.Size-dependent cellular toxicity of silver nanoparticles2012100410331043OhW. K.KimS.KwonO.JangJ.Shape-dependent cytotoxicity of polyaniline nanomaterials in human fibroblast cells201111542544260SchaeublinN. M.Braydich-StolleL. K.SchrandA. M.MillerJ. M.HutchisonJ.SchlagerJ. J.HussainS. M.Surface charge of gold nanoparticles mediates mechanism of toxicity2011324104202-s2.0-7995160266710.1039/c0nr00478bHarhajiL.IsakovicA.RaicevicN.MarkovicZ.Todorovic-MarkovicB.NikolicN.Vranjes-DjuricS.MarkovicI.TrajkovicV.Multiple mechanisms underlying the anticancer action of nanocrystalline fullerene20075681–389982-s2.0-3425081679410.1016/j.ejphar.2007.04.041FoldbjergR.OlesenP.HougaardM.DangD. A.HoffmannH. J.AutrupH.PVP-coated silver nanoparticles and silver ions induce reactive oxygen species, apoptosis and necrosis in THP-1 monocytes200919021561622-s2.0-6944908436810.1016/j.toxlet.2009.07.009AroraS.JainJ.RajwadeJ. M.PaknikarK. M.Cellular responses induced by silver nanoparticles: in vitro studies20081792931002-s2.0-4444915759110.1016/j.toxlet.2008.04.009AsareN.InstanesC.SandbergW. J.RefsnesM.SchwarzeP.KruszewskiM.BrunborgG.Cytotoxic and genotoxic effects of silver nanoparticles in testicular cells20122911–36572Di GiorgioM. L.BucchianicoS. D.RagnelliA. M.AimolaP.SantucciS.PomaA.Effects of single and multi walled carbon nanotubes on macrophages: cyto and genotoxicity and electron microscopy2011722120312-s2.0-7995602248610.1016/j.mrgentox.2011.02.008TianF.CuiD.SchwarzH.EstradaG. G.KobayashiH.Cytotoxicity of single-wall carbon nanotubes on human fibroblasts2006207120212122-s2.0-3374621467010.1016/j.tiv.2006.03.008CuiD.TianF.KongY.TitushikinI.GaoH.Effects of single-walled carbon nanotubes on the polymerase chain reaction20041511541572-s2.0-074226936610.1088/0957-4484/15/1/030ZhuL.ChangD. W.DaiL.HongY.DNA damage induced by multiwalled carbon nanotubes in mouse embryonic stem cells2007712359235972-s2.0-3804916392410.1021/nl071303vPulskampK.DiabatéS.KrugH. F.Carbon nanotubes show no sign of acute toxicity but induce intracellular reactive oxygen species in dependence on contaminants2007168158742-s2.0-3384541013910.1016/j.toxlet.2006.11.001GalluzziL.ChiarantiniL.PantucciE.Development of a multilevel approach for the evaluation of nanomaterials' toxicity201273393409BrennanM. A.CooksonB. T.Salmonella induces macrophage death by caspase-1-dependent necrosis200038131402-s2.0-003381533010.1046/j.1365-2958.2000.02103.xReisetterA. C.StebounovaL. V.BaltrusaitisJ.PowersL.GuptaA.GrassianV. H.MonickM. M.Induction of inflammasome-dependent pyroptosis by carbon black nanoparticles20112862421844218522-s2.0-7995873992310.1074/jbc.M111.238519YazdiA. S.GuardaG.RiteauN.DrexlerS. K.TardivelA.CouillinI.TschoppJ.Nanoparticles activate the NLR pyrin domain containing 3 (Nlrp3) inflammasome and cause pulmonary inflammation through release of IL-1α and IL-1β20101074519449194542-s2.0-7865061058010.1073/pnas.1008155107HillegassJ. M.ShuklaA.LathropS. A.MacPhersonM. B.FukagawaN. K.MossmanB. T.Assessing nanotoxicity in cells in vitro2010232192312-s2.0-7795365614910.1002/wnan.54SchrandA. M.RahmanM. F.HussainS. M.SchlagerJ. J.SmithD. A.SyedA. F.Metal-based nanoparticles and their toxicity assessment2010255445682-s2.0-7844929602110.1002/wnan.103DamoiseauxR.GeorgeS.LiM.PokhrelS.JiZ.FranceB.XiaT.SuarezE.RalloR.MädlerL.CohenY.HoekE. M. V.NelA.No time to lose—high throughput screening to assess nanomaterial safety201134134513602-s2.0-7995374088610.1039/c0nr00618aShawS. Y.WestlyE. C.PittetM. J.SubramanianA.SchreiberS. L.WeisslederR.Perturbational profiling of nanomaterial biologic activity200810521738773922-s2.0-4494913493510.1073/pnas.0802878105GalluzziL.AaronsonS. A.AbramsJ.AlnemriE. S.AndrewsD. W.BaehreckeE. H.BazanN. G.BlagosklonnyM. V.BlomgrenK.BornerC.BredesenD. E.BrennerC.CastedoM.CidlowskiJ. A.CiechanoverA.CohenG. M.De LaurenziV.De MariaR.DeshmukhM.DynlachtB. D.El-DeiryW. S.FlavellR. A.FuldaS.GarridoC.GolsteinP.GougeonM. L.GreenD. R.GronemeyerH.HajnóczkyG.HardwickJ. M.HengartnerM. O.IchijoH.JäätteläM.KeppO.KimchiA.KlionskyD. J.KnightR. A.KornbluthS.KumarS.LevineB.LiptonS. A.LugliE.MadeoF.MalorniW.MarineJ. C. W.MartinS. J.MedemaJ. P.MehlenP.MelinoG.MollU. M.MorselliE.NagataS.NicholsonD. W.NicoteraP.NuñezG.OrenM.PenningerJ.PervaizS.PeterM. E.PiacentiniM.PrehnJ. H. M.PuthalakathH.RabinovichG. A.RizzutoR.RodriguesC. M. P.RubinszteinD. C.RudelT.ScorranoL.SimonH. U.StellerH.TschoppJ.TsujimotoY.VandenabeeleP.VitaleI.VousdenK. H.YouleR. J.YuanJ.ZhivotovskyB.KroemerG.Guidelines for the use and interpretation of assays for monitoring cell death in higher eukaryotes2009168109311072-s2.0-6765075108010.1038/cdd.2009.44MossmanB. T.BignonJ.CornM.SeatonA.GeeJ. B. L.Asbestos: scientific developments and implications for public policy199024749402943012-s2.0-0025156969RobinsonB. W. S.LakeR. A.Advances in malignant mesothelioma200535315159116032-s2.0-2644445884510.1056/NEJMra050152ZhangT.StilwellJ. L.GerionD.DingL.ElboudwarejO.CookeP. A.GrayJ. W.AlivisatosA. P.ChenF. F.Cellular effect of high doses of silica-coated quantum dot profiled with high throughput gene expression analysis and high content cellomics measurements2006648008082-s2.0-3364639888610.1021/nl0603350ZollanvariA.CunninghamM. J.Braga-NetoU.DoughertyE. R.Analysis and modeling of time-course gene-expression profiles from nanomaterial-exposed primary human epidermal keratinocytes200910supplement 11S102-s2.0-70449408946TyurinaY. Y.TyurinV. A.KapralovaV. I.WasserloosK.MosherM.EpperlyM. W.GreenbergerJ. S.PittB. R.KaganV. E.Oxidative lipidomics of γ-radiation-induced lung injury: mass spectrometric characterization of cardiolipin and phosphatidylserine peroxidation201117556106212-s2.0-7995539508610.1667/RR2297.1TeeguardenJ. G.Webb-RobertsonB. J.WatersK. M.MurrayA. R.KisinE. R.VarnumS. M.JacobsJ. M.PoundsJ. G.ZangerR. C.ShvedovaA. A.Comparative proteomics and pulmonary toxicity of instilled single-walled carbon nanotubes, crocidolite asbestos, and ultrafine carbon black in mice201112011231352-s2.0-7995209431510.1093/toxsci/kfq363ZhangY.XuY.LiZ.Mechanistic toxicity evaluation of uncoated and PEGylated single-walled carbon nanotubes in neuronal PC12 cells20115970207033