Acute and subacute toxicity study of water-soluble polyalkylsulfonated C60 in rats

Lysosomal nanotoxicity: Impact of nanomedicines on lysosomal function

Although several nanomedicines got clinical approval over the past two decades, the clinical translation rate is relatively small so far. There are many post-surveillance withdrawals of nanomedicines caused by various safety issues. For successful clinical advancement of nanotechnology, it is of unmet need to realize cellular and molecular foundation of nanotoxicity. Current data suggest that lysosomal dysfunction caused by nanoparticles is emerging as the most common intracellular trigger of nanotoxicity. This review analyzes prospect mechanisms of lysosomal dysfunction-mediated toxicity induced by nanoparticles. We summarized and critically assessed adverse drug reactions of current clinically approved nanomedicines. Importantly, we show that physicochemical properties have great impact on nanoparticles interaction with cells, excretion route and kinetics, and subsequently on toxicity. We analyzed literature on adverse reactions of current nanomedicines and hypothesized that adverse reactions might be linked with lysosomal dysfunction caused by nanomedicines. Finally, from our analysis it becomes clear that it is unjustifiable to generalize safety and toxicity of nanoparticles, since different particles possess distinct toxicological properties. We propose that the biological mechanism of the disease progression and treatment should be central in the optimization of nanoparticle design.

Decabromodiphenyl ether-induced PRKACA hypermethylation contributed to glycolipid metabolism disorder via regulating PKA/AMPK pathway in rat and L-02 cells

BDE-209 is the most prevalent congener of polybrominated diphenyl ethers and has high bioaccumulation in humans and animals. BDE-209 has been reported to disrupt glycolipid metabolism, but the mechanisms are still unclear. In this study, we found that BDE-209 induced liver tissue injury and hepatotoxicity, increased the glucose and total cholesterol levels in the serum of rats, and increased glucose and triglyceride levels in L-02 cells. BDE-209 exposure changed the PKA, p-PKA, AMPK, p-AMPK, ACC, and FAS expression in rats' liver and L-02 cells. Moreover, BDE-209 induced PRKACA-1 hypermethylation in L-02 cells. AMPK activator (AICAR) inhibited the changes of p-AMPK, ACC, and FAS expression and elevation of glucose and triglyceride levels induced by BDE-209. DNA methylation inhibitor (5-Aza-CdR) reversed BDE-209 induced alters of PKA/AMPK/ACC/FAS signaling pathway. These results demonstrated that BDE-209 could disrupt the glycolipid metabolism by causing PRKACA-1 hypermethylation to regulate the PKA/AMPK signaling pathway in hepatocytes.

Effect of Long-Term Treatment with C60 Fullerenes on the Lifespan and Health Status of CBA/Ca Mice

Several studies claimed C₆₀ fullerenes as a prospective geroprotector drug due to their ability to capture free radicals effectively and caused a profound interest in C₆₀ in life extension communities. Multiple additives are already sold for human consumption despite a small body of evidence supporting the beneficial effects of fullerenes on the lifespan. To test the effect of C₆₀ fullerenes on lifespan and healthspan, we administered C₆₀ fullerenes dissolved in virgin olive oil orally to 10-12 months old CBA/Ca mice of both genders for 7 months and assessed their survival. To uncover C₆₀ and virgin olive effects, we established two control groups: mice treated with virgin olive oil (vehicle) and mice treated with drinking water. To measure healthspan, we conducted daily monitoring of health condition and lethality and monthly bodyweight measurements. We also assessed physical activity, glucose metabolism, and hematological parameters every 3 months. We did not observe health deterioration in the animals treated with C₆₀ compared with the control groups. Treatment of mice with C₆₀ fullerenes resulted in an increased lifespan of males and females compared with the olive oil-treated animals. The lifespan of C₆₀-treated mice was similar to the mice treated with water. These results suggest that the lifespan-extending effect in C₆₀-treated mice appears due to the protective effect of fullerenes in opposition to the negative effect of olive oil in CBA/Ca mice.

Toxicological Aspects of Carbon Nanotubes, Fullerenes and Graphenes

Nanomedicines exhibit unbelievable capability in overcoming the hurdles faced in biological applications. Carbon nanotubes (CNTs), graphene-family nanomaterials and fullerenes are a class of engineered nanoparticles that have emerged as a new option for possible use in drug/gene delivery for life-threatening diseases. Their adaptability to pharmaceutical applications has opened new vistas for biomedical applications. Successful applications of this family of engineered nanoparticles in various fields may not support their use in medicine due to inconsistent data on toxicity as well as the lack of a centralized toxicity database. Inconsistent toxicological studies and lack of mechanistic understanding have been the reasons for limited understanding of their toxicological aspects. These nanoparticles, when underivatized or pristine, are considered as safe, however less reactive. The derivatized forms or functionalization changes their chemistry significantly to modify their biological effects including toxicity. They can cause acute and long term injuries in tissues by penetration through the the blood-air barrier, blood-alveolus barrier, blood-brain barrier, and blood-placenta barrier. and by accumulating in the lung, liver, and spleen . The toxicological effects are manifested through inflammatory response, DNA damage, apoptosis, autophagy and necrosis. Other factors that largely influence the toxicity of carbon nanotubes, graphenes and fullerenes are the concentration, functionalization, dimensional and surface topographical factors. Thus, a better understanding of the toxicity profile of CNTs, graphene-family nanomaterials and fullerenes in humans, animals and the environment is of significant importance, to improve their biological safety, to facilitate their wide biological application and for the successful commercial application. The exploration of appropriate cell lines to investigate specific receptors and intracellular targets as well as chronic toxicity beyond the proof-of-concept is required.

Challenges in the development of nanoparticle-based imaging agents: Characterization and biology

Despite imaging agents being some of the earliest nanomedicines in clinical use, the vast majority of current research and translational activities in the nanomedicine field involves therapeutics, while imaging agents are severely underrepresented. The reasons for this lack of representation are several fold, including difficulties in synthesis and scale-up, biocompatibility issues, lack of suitable tissue/disease selective targeting ligands and receptors, and a high bar for regulatory approval. The recent focus on immunotherapies and personalized medicine, and development of nanoparticle constructs with better tissue distribution and selectivity, provide new opportunities for nanomedicine imaging agent development. This manuscript will provide an overview of trends in imaging nanomedicine characterization and biocompatibility, and new horizons for future development. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Diligent profiling of preclinical safety of the silk protein sericin

BACKGROUND

Sericin is a widely used protein in the pharmaceutical industry derived from the silkworm, Bombyx mori, and used for the treatment of various diseases and pathological conditions. It is the main ingredient of the Unani preparation khameera abresham. The study was conducted to evaluate the preclinical toxicity of the silk protein sericin in mice.

METHODS

In the acute toxicity study, sericin was administered once orally to different groups of animals at doses of 500, 1000, and 2000 mg/kg. Animals were observed for 14 days. In the sub-acute toxicity study, sericin was administered in mice for 4 weeks in the toxic group at doses of 500, 1000, and 2000 mg/kg, while in the recovery group it was administered for 4 weeks at doses of 500 and 2000 mg/kg followed by 2 weeks of distilled water administration.

RESULTS

In the acute toxicity study, the observed parameters showed no significant difference, and no mortality was reported. In the sub-acute toxicity study, there were no toxicological effects in any of the estimated parameters, while histopathological analysis showed inflammation in vital organs at the dose of 2000 mg/kg.

CONCLUSIONS

Results of our acute toxicity study suggest that sericin is safe at all administered doses, while the sub-acute study suggests that the NOAEL (no-observed-adverse-effect level) of sericin is below 2000 mg/kg, at which it can be considered safe.

Autophagy Modulated by Inorganic Nanomaterials

With the rapid development of nanotechnology, inorganic nanomaterials (NMs) have been widely applied in modern society. As human exposure to inorganic NMs is inevitable, comprehensive assessment of the safety of inorganic NMs is required. It is well known that autophagy plays dual roles in cell survival and cell death. Moreover, inorganic NMs have been proven to induce autophagy perturbation in cells. Therefore, an in-depth understanding of inorganic NMs-modulated autophagy is required for the safety assessment of inorganic NMs. This review presents an overview of a set of inorganic NMs, consisting of iron oxide NMs, silver NMs, gold NMs, carbon-based NMs, silica NMs, quantum dots, rare earth oxide NMs, zinc oxide NMs, alumina NMs, and titanium dioxide NMs, as well as how each modulates autophagy. This review emphasizes the potential mechanisms underlying NMs-induced autophagy perturbation, as well as the role of autophagy perturbation in cell fate determination. Furthermore, we also briefly review the potential roles of inorganic NMs-modulated autophagy in diagnosis and treatment of disease.

Necrotic, apoptotic and autophagic cell fates triggered by nanoparticles

Nanomaterials have gained a rapid increase in use in a variety of applications that pertain to many aspects of human life. The majority of these innovations are centered on medical applications and a range of industrial and environmental uses ranging from electronics to environmental remediation. Despite the advantages of NPs, the knowledge of their toxicological behavior and their interactions with the cellular machinery that determines cell fate is extremely limited. This review is an attempt to summarize and increase our understanding of the mechanistic basis of nanomaterial interactions with the cellular machinery that governs cell fate and activity. We review the mechanisms of NP-induced necrosis, apoptosis and autophagy and potential implications of these pathways in nanomaterial-induced outcomes. Abbreviations: Ag, silver; CdTe, cadmium telluride; CNTs, carbon nanotubes; EC, endothelial cell; GFP, green fluorescent protein; GO, graphene oxide; GSH, glutathione; HUVECs, human umbilical vein endothelial cells; NP, nanoparticle; PEI, polyethylenimine; PVP, polyvinylpyrrolidone; QD, quantum dot; ROS, reactive oxygen species; SiO2, silicon dioxide; SPIONs, superparamagnetic iron oxide nanoparticles; SWCNT, single-walled carbon nanotubes; TiO2, titanium dioxide; USPION, ultra-small super paramagnetic iron oxide; ZnO, zinc oxide.

Fullerenes as photosensitizers in photodynamic therapy: pros and cons

One class of carbon nanomaterials is the closed cages known as fullerenes. The first member to be discovered in 1985 was C60, called "buckminsterfullerene" as its cage structure resembled a geodesic dome. Due to their extended π-conjugation they absorb visible light, possess a high triplet yield and can generate reactive oxygen species upon illumination, suggesting a possible role of fullerenes in photodynamic therapy (PDT). Pristine C₆₀ is highly hydrophobic and prone to aggregation, necessitating functionalization to provide aqueous solubility and biocompatibility. The most common functional groups attached are anionic (carboxylic or sulfonic acids) or cationic (various quaternary ammonium groups). Depending on the functionalization, these fullerenes can be designed to be taken up into cancer cells, or to bind to microbial cells (Gram-positive, Gram-negative bacteria, fungi). Fullerenes can be excited with a wide range of wavelengths, UVA, blue, green or white light. We have reported a series of functionalized fullerenes (C₆₀, C₇₀, C₈₂) with attached polycationic chains and additional light-harvesting antennae that can be used in vitro and in animal models of localized infections. Advantages of fullerenes as photosensitizers are: (a) versatile functionalization; (b) light-harvesting antennae; (c) ability to undergo Type 1, 2, and 3 photochemistry; (d) electron transfer can lead to oxygen-independent photokilling; (e) antimicrobial activity can be potentiated by inorganic salts; (f) can self-assemble into supramolecular fullerosomes; (g) components of theranostic nanoparticles; (h) high resistance to photobleaching. Disadvantages include: (a) highly hydrophobic and prone to aggregation; (b) overall short wavelength absorption; (c) relatively high molecular weight; (d) paradoxically can be anti-oxidants; (e) lack of fluorescence emission for imaging.

Nanomedicine

Nanomedicine, an offshoot of nanotechnology, is considered as one of the most promising technologies of the 21st century. Due to their minute size, nanomedicines can easily target difficult-to-reach sites with improved solubility and bioavailability and reduced adverse effects. They also act as versatile delivery systems, carrying both chemotherapeutics and imaging agents to targeted sites. Hence, nanomedicine can be used to achieve the same therapeutic effect at smaller doses than their conventional counterparts and can offer impressive resolutions for various life-threatening diseases. Although certain issues have been raised about the potential toxicities of nanomaterials, it is anticipated that the advances in nanomedicine will furnish clarifications to many of modern medicine's unsolved problems. This chapter aims to provide a comprehensive and contemporary survey of various nanomedicine products along with the major risks and side effects associated with the nanoparticles.

Respiratory toxicity and immunotoxicity evaluations of microparticle and nanoparticle C60 fullerene aggregates in mice and rats following nose-only inhalation for 13 weeks

C60 fullerene (C60), or buckminsterfullerene, is a spherical arrangement of 60 carbon atoms, having a diameter of approximately 1 nm, and is produced naturally as a by-product of combustion. Due to its small size, C60 has attracted much attention for use in a variety of applications; however, insufficient information is available regarding its toxicological effects. The effects on respiratory toxicity and immunotoxicity of C60 aggregates (50 nm [nano-C60] and 1 μm [micro-C60] diameter) were examined in B6C3F1/N mice and Wistar Han rats after nose-only inhalation for 13 weeks. Exposure concentrations were selected to allow for data evaluations using both mass-based and particle surface area-based exposure metrics. Nano-C60 exposure levels selected were 0.5 and 2 mg/m³ (0.033 and 0.112 m²/m³), while micro-C60 exposures were 2, 15 and 30 mg/m³ (0.011, 0.084 and 0.167 m²/m³). There were no systemic effects on innate, cell-mediated, or humoral immune function. Pulmonary inflammatory responses (histiocytic infiltration, macrophage pigmentation, chronic inflammation) were concentration-dependent and corresponded to increases in monocyte chemoattractant protein (MCP)-1 (rats) and macrophage inflammatory protein (MIP)-1α (mice) in bronchoalveolar lavage (BAL) fluid. Lung overload may have contributed to the pulmonary inflammatory responses observed following nano-C60 exposure at 2 mg/m³ and micro-C60 exposure at 30 mg/m³. Phenotype shifts in cells recovered from the BAL were also observed in all C60-exposed rats, regardless of the level of exposure. Overall, more severe pulmonary effects were observed for nano-C60 than for micro-C60 for mass-based exposure comparisons. However, for surface-area-based exposures, more severe pulmonary effects were observed for micro-C60 than for nano-C60, highlighting the importance of dosimetry when evaluating toxicity between nano- and microparticles.

Recent achievements in colorectal cancer diagnostic and therapy by the use of nanoparticles

Colorectal cancer is a major public health issue, being the third most common cancer in men and the second in women. It is one of the leading causes of cancer deaths. Nanomedicine is an emerging field of interest, many of its aspects being linked to cancer research. Chemotherapy has a well-established role in colorectal cancer management, unfortunately being limited by inability to have a selective distribution, by multidrug resistance and adverse effects. Researches carried out in recent years about nanotechnologies aimed, among others, to resolve the issues mentioned above. Targeted and localized delivery of the chemotherapeutic drugs, using nanoparticles, with selective destruction of cancerous cells would minimize the toxicity on healthy tissues. Also, the use of nanomaterials as contrast agent could improve sensitivity and specificity of diagnosis. The purpose of this review is to highlight the recent achievements of cancer research by use of nanomaterials, in the idea of finding the ideal composite, capable to simultaneous diagnostic and treat cancer.

Antidiabetic, antioxidant, and TNF-α lowering properties of extract of the traditionally used plant Ixeris gracilis in alloxan-induced diabetic mice

CONTEXT

Ixeris gracilis DC. Stebbins (Asteraceae) is a plant considered to be medicinal by local communities of Meghalaya, India.

OBJECTIVE

To evaluate the antidiabetic potential, antioxidant activity, and effect of the 80% methanolic extract of the leaves of Ixeris gracilis on tumor necrosis factor-α (TNF-α) expression.

MATERIALS AND METHODS

Varying doses (250-1000 mg/kg body weight) were administered intraperitoneally to normoglycemic mice and their hypoglycemic properties noted for 24 h; the optimum dose observed was used to evaluate its antihyperglycemic activity and effect on glucose tolerance. In vitro antioxidant activity was analyzed by assessing the DPPH radicals scavenging ability of the extract and the total polyphenols, flavonoid, carbohydrate, and protein contents were determined. Diabetic mice were then subjected to daily intraperitoneal injections of the extract for 12 days after which the antioxidant enzyme activities in the tissues were assayed and serum TNF-α was evaluated by ELISA.

RESULTS

The extract displayed varying hypoglycemic activity. The dose of 250 mg/kg body weight exhibited potent antihyperglycemic activity and improved glucose tolerance. The extract was able to scavenge free radicals (IC50 57.544 µg/ml) and contained polyphenol (76.269 ± 0.204 mg GAE/g dry wt), flavonoid (70.070 ± 0.626 mg rutin equivalent/g dry wt), protein (4.368 ± 8.916 mg/g dry wt), and carbohydrate (558.189 ± 0.002 mg/g dry wt). TNF-α level and overall activity of glutathione peroxidase and superoxide dismutase in the liver, kidney, and brain of extract-treated diabetic mice were improved.

CONCLUSION

The study supports the inclusion of Ixeris gracilis in the list of plants with antidiabetic potential.

Application of fullerenes in nanomedicine: an update

Fullerenes are carbon spheres presently being pursued globally for a wide range of applications in nanomedicine. These molecules have unique electronic properties that make them attractive candidates for diagnostic, therapeutic and theranostic applications. Herein, the latest research is discussed on developing fullerene-based therapeutics as antioxidants for inflammatory diseases, their potential as antiviral/bacterial agents, utility as a drug delivery device and the promise of endohedral fullerenes as new MRI contrast agents. The recent discovery that certain fullerene derivatives can stabilize immune effector cells to prevent or inhibit the release of proinflammatory mediators makes them potential candidates for several diseases such as asthma, arthritis and multiple sclerosis. Gadolinium-containing endohedral fullerenes are being pursued as diagnostic MRI contrast agents for several diseases. Finally, a new class of fullerene-based theranostics has been developed, which combine therapeutic and diagnostic capabilities to specifically detect and kill cancer cells.

Inhibition of autophagy enhances the anticancer activity of silver nanoparticles

Silver nanoparticles (Ag NPs) are cytotoxic to cancer cells and possess excellent potential as an antitumor agent. A variety of nanoparticles have been shown to induce autophagy, a critical cellular degradation process, and the elevated autophagy in most of these situations promotes cell death. Whether Ag NPs can induce autophagy and how it might affect the anticancer activity of Ag NPs has not been reported. Here we show that Ag NPs induced autophagy in cancer cells by activating the PtdIns3K signaling pathway. The autophagy induced by Ag NPs was characterized by enhanced autophagosome formation, normal cargo degradation, and no disruption of lysosomal function. Consistent with these properties, the autophagy induced by Ag NPs promoted cell survival, as inhibition of autophagy by either chemical inhibitors or ATG5 siRNA enhanced Ag NPs-elicited cancer cell killing. We further demonstrated that wortmannin, a widely used inhibitor of autophagy, significantly enhanced the antitumor effect of Ag NPs in the B16 mouse melanoma cell model. Our results revealed a novel biological activity of Ag NPs in inducing cytoprotective autophagy, and inhibition of autophagy may be a useful strategy for improving the efficacy of Ag NPs in anticancer therapy.

Molecular modeling in structural nano-toxicology: interactions of nano-particles with nano-machinery of cells

Over the past two decades, nanotechnology has emerged as a key player in various disciplines of science and technology. Some of the most exciting applications are in the field of biomedicine - for theranostics (for combined diagnostic and therapeutic purposes) as well as for exploration of biological systems. A detailed understanding of the molecular interactions between nanoparticles and biological nano-machinery - macromolecules, membranes, and intracellular organelles - is crucial for obtaining adequate information on mechanisms of action of nanomaterials as well as a perspective on the long term effects of these materials and their possible toxicological outcomes. This review focuses on the use of structure-based computational molecular modeling as a tool to understand and to predict the interactions between nanomaterials and nano-biosystems. We review major approaches and provide examples of computational analysis of the structural principles behind such interactions. A rationale on how nanoparticles of different sizes, shape, structure and chemical properties can affect the organization and functions of nano-machinery of cells is also presented.

MULTIFUNCTIONAL FULLERENE- AND METALLOFULLERENE-BASED NANOBIOMATERIALS

Recent advances in nanotechnology have enabled the synthesis and characterization of nanomaterials suitable for applications in the field of biology and medicine. Due to their unique physico-chemical properties, carbon-based nanomaterials such as fullerenes, metallofullerenes, carbon nanotubes and graphene have been widely investigated as multifunctional materials for applications in tissue engineering, molecular imaging, therapeutics, drug delivery and biosensing. In this review, we focus on the multifunctional capabilities of fullerenes and metallofullerenes for diagnosis and therapy. Specifically, we review recent advances toward the development of fullerene- and metallofullerene-based magnetic resonance imaging (MRI) and X-ray imaging contrast agents, drug and gene delivery vehicles, and photodynamic therapy agents. We also discuss in vitro and in vivo toxicity, and biocompatibility issues associated with the use of fullerenes and metallofullerenes for biomedical applications.

Histopathology of fathead minnow (Pimephales promelas) exposed to hydroxylated fullerenes

Hydroxylated fullerenes are reported to be very strong antioxidants, acting to quench reactive oxygen species, thus having strong potential for important and widespread applications in innovative therapies for a variety of disease processes. However, their potential for toxicological side effects is still largely controversial and unknown. Effects of hydroxylated fullerenes C60(OH)24 on the fathead minnow (Pimephales promelas) were investigated microscopically after a 72-hour (acute) exposure by intraperitoneal injection of 20 ppm of hydroxylated fullerenes per gram of body mass. Cumulative, semi-quantitative histopathologic evaluation of brain, liver, anterior kidney, posterior kidney, skin, coelom, gills and the vestibuloauditory system revealed significant differences between control and hydroxylated fullerene-treated fish. Fullerene-treated fish had much higher cumulative histopathology scores. Histopathologic changes included loss of cellularity in the interstitium of the kidney, a primary site of haematopoiesis in fish, and loss of intracytoplasmic glycogen in liver. In the coelom, variable numbers of leukocytes, including many macrophages and fewer heterophils and rodlet cells, were admixed with the nanomaterial. These findings raise concern about in vivo administration of hydroxylated fullerenes in experimental drugs and procedures in human medicine, and should be investigated in more detail.

Application of a quantitative weight of evidence approach for ranking and prioritising occupational exposure scenarios for titanium dioxide and carbon nanomaterials

Substantial limitations and uncertainties hinder the exposure assessment of engineered nanomaterials (ENMs). The present deficit of reliable measurements and models will inevitably lead in the near term to qualitative and uncertain exposure estimations, which may fail to support adequate risk assessment and management. Therefore it is necessary to complement the current toolset with user-friendly methods for near-term nanosafety evaluation. This paper proposes an approach for relative exposure screening of ENMs. For the first time, an exposure model explicitly implements quantitative weight of evidence (WoE) methods and utilises expert judgement for filling data gaps in the available evidence-base. Application of the framework is illustrated for screening of exposure scenarios for nanoscale titanium dioxide, carbon nanotubes and fullerenes, but it is applicable to other nanomaterials as well. The results show that the WoE-based model overestimates exposure for scenarios where expert judgement was substantially used to fill data gaps, which suggests its conservative nature. In order to test how variations in input data influence the obtained results, probabilistic Monte Carlo sensitivity analysis was applied to demonstrate that the model performs in stable manner.

Sub-acute oral toxicity study with fullerene C60 in rats

To obtain initial information on the possible repeated-dose oral toxicity of fullerene C60, Crl:CD(SD) rats were administered fullerene C60 by gavage once daily at 0 (vehicle: corn oil), 1, 10, 100, or 1,000 mg/kg/day for 29 days, followed by a 14-day recovery period. No deaths occurred in any groups, and there were no changes from controls in detailed clinical observations, body weights, and food consumption in any treatment groups. Moreover, no treatment-related histopathological changes were found in any organs examined at the end of the administration period and at the end of the recovery period. Blackish feces and black contents of the stomach and large intestine were observed in males and females at 1,000 mg/kg/day in the treatment group. There were no changes from controls in the liver and spleen weights at the end of the administration period, but those weights in males in the 1,000 mg/kg/day group increased at the end of the recovery period. Using liquid chromatography-tandem mass spectrometry, fullerene C60 were not detected in the liver, spleen or kidney at the end of the administration period and also at the end of the recovery period. In conclusion, the present study revealed no toxicological effects of fullerene C60; however, the slight increases in liver and spleen weights after the 14-day recovery period may be because of the influence of fullerene C60 oral administration. In the future, it will be necessary to conduct a long-term examination because the effects of fullerene C60 cannot be ruled out.

Autophagy and lysosomal dysfunction as emerging mechanisms of nanomaterial toxicity

The study of the potential risks associated with the manufacture, use, and disposal of nanoscale materials, and their mechanisms of toxicity, is important for the continued advancement of nanotechnology. Currently, the most widely accepted paradigms of nanomaterial toxicity are oxidative stress and inflammation, but the underlying mechanisms are poorly defined. This review will highlight the significance of autophagy and lysosomal dysfunction as emerging mechanisms of nanomaterial toxicity. Most endocytic routes of nanomaterial cell uptake converge upon the lysosome, making the lysosomal compartment the most common intracellular site of nanoparticle sequestration and degradation. In addition to the endo-lysosomal pathway, recent evidence suggests that some nanomaterials can also induce autophagy. Among the many physiological functions, the lysosome, by way of the autophagy (macroautophagy) pathway, degrades intracellular pathogens, and damaged organelles and proteins. Thus, autophagy induction by nanoparticles may be an attempt to degrade what is perceived by the cell as foreign or aberrant. While the autophagy and endo-lysosomal pathways have the potential to influence the disposition of nanomaterials, there is also a growing body of literature suggesting that biopersistent nanomaterials can, in turn, negatively impact these pathways. Indeed, there is ample evidence that biopersistent nanomaterials can cause autophagy and lysosomal dysfunctions resulting in toxicological consequences.

Photodynamic therapy with fullerenes in vivo: reality or a dream?

Photodynamic therapy (PDT) employs the combination of nontoxic photosensitizers and visible light that is absorbed by the chromophore to produce long-lived triplet states that can carry out photochemistry in the presence of oxygen to kill cells. The closed carbon-cage structure found in fullerenes can act as a photosensitizer, especially when functionalized to impart water solubility. Although there are reports of the use of fullerenes to carry out light-mediated destruction of viruses, microorganisms and cancer cells in vitro, the use of fullerenes to mediate PDT of diseases such as cancer and infections in animal models is less well developed. It has recently been shown that fullerene PDT can be used to save the life of mice with wounds infected with pathogenic Gram-negative bacteria. Fullerene PDT has also been used to treat mouse models of various cancers including disseminated metastatic cancer in the peritoneal cavity. In vivo PDT with fullerenes represents a new application in nanomedicine.

Applications of functionalized fullerenes in tumor theranostics

Functionalized fullerenes with specific physicochemical properties have been developed for cancer diagnosis and therapy. Notably, metallofullerene is a new class of magnetic resonance imaging (MRI) contrast-enhancing agent, and may have promising applications for clinical diagnosis. Polyhydroxylated and carboxyl fullerenes have been applied to photoacoustic imaging. Moreover, in recent years, functionalized fullerenes have shown potential in tumor therapies, such as photodynamic therapy, photothermal treatment, radiotherapy and chemotherapeutics. Their antitumor effects may be associated with the modulation of oxidative stress, anti-angiogenesis, and immunostimulatory activity. While various types of novel nanoparticle agents have been exploited in tumor theranostics, their distribution, metabolism and toxicity in organisms have also been a source of concern among researchers. The present review summarizes the potential of fullerenes as tumor theranostics agents and their possible underlying mechanisms are discussed.

Magnetic nanoparticles: an update of application for drug delivery and possible toxic effects

Magnetic nanoparticles (MNPs) represent a subclass within the overall category of nanomaterials and are widely used in many applications, particularly in the biomedical sciences such as targeted delivery of drugs or genes, in magnetic resonance imaging, and in hyperthermia (treating tumors with heat). Although the potential benefits of MNPs are considerable, there is a distinct need to identify any potential toxicity associated with these MNPs. The potential of MNPs in drug delivery stems from the intrinsic properties of the magnetic core combined with their drug loading capability and the biomedical properties of MNPs generated by different surface coatings. These surface modifications alter the particokinetics and toxicity of MNPs by changing protein-MNP or cell-MNP interactions. This review contains current advances in MNPs for drug delivery and their possible organ toxicities associated with disturbance in body iron homeostasis. The importance of protein-MNP interactions and various safety considerations relating to MNP exposure are also addressed.

Fate and toxicity of metallic and metal-containing nanoparticles for biomedical applications

It is important to obtain a better understanding of the uptake, trafficking, pharmacokinetics, clearance, and role of nanomaterials in biological systems, so that their possible undesirable effects can be avoided. A number of metallic or metal-containing nanomaterials, such as gold nanoparticles and nanorods, quantum dots, iron oxides nanoparticles, and endohedral metallofullerenes, have already been or will soon become very promising for biomedical applications. This review presents a summary of currently available data on the fate and toxicity of these metallic or metal-containing nanoparticles based on animal studies. Several issues regarding the nanotoxicity assessment and future directions on the study of the fate of these nanoparticles are also proposed.

Functionalized carbon nanomaterials: exploring the interactions with Caco-2 cells for potential oral drug delivery

Although carbon nanomaterials (CNMs) have been increasingly studied for their biomedical applications, there is limited research on these novel materials for oral drug delivery. As such, this study aimed to explore the potential of CNMs in oral drug delivery, and the objectives were to evaluate CNM cytotoxicity and their abilities to modulate paracellular transport and the P-glycoprotein (P-gp) efflux pump. Three types of functionalized CNMs were studied, including polyhydroxy small-gap fullerenes (OH-fullerenes), carboxylic acid functionalized single-walled carbon nanotubes (f SWCNT-COOH) and poly(ethylene glycol) functionalized single-walled carbon nanotubes (f SWCNT-PEG), using the well-established Caco-2 cell monolayer to represent the intestinal epithelium. All three CNMs had minimum cytotoxicity on Caco-2 cells, as demonstrated through lactose dehydrogenase release and 3-(4,5-dimethyliazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Of the three CNMs, f SWCNT-COOH significantly reduced transepithelial electrical resistance and enhanced transport of Lucifer Yellow across the Caco-2 monolayer. Confocal fluorescence microscopy showed that f SWCNT-COOH treated cells had the highest perturbation in the distribution of ZO-1, a protein marker of tight junction, suggesting that f SWCNT-COOH could enhance paracellular permeability via disruption of tight junctions. This modulating effect of f SWCNT-COOH can be reversed over time. Furthermore, cellular accumulation of the P-gp substrate, rhodamine-123, was significantly increased in cells treated with f SWCNT-COOH, suggestive of P-gp inhibition. Of note, f SWCNT-PEG could increase rhodamine-123 accumulation without modifying the tight junction. Collectively, these results suggest that the functionalized CNMs could be useful as modulators for oral drug delivery, and the differential effects on the intestinal epithelium imparted by different types of CNMs would create unique opportunities for drug-specific oral delivery applications.

Evaluation of Maternal Toxicity in Rats Exposed to Multi-Wall Carbon Nanotubes during Pregnancy

OBJECTIVES

The present study investigated the potential adverse effects of multi-wall carbon nanotubes (MWCNTs) on pregnant dams and embryonic development following maternal exposure in rats.

METHODS

MWCNTs were orally administered to pregnant rats from gestational day (GD) 6 through 19 at dose levels of 0, 8, 40, 200, and 1000 mg/kg/day. During the test period, clinical signs, mortality, body weights, food consumption, serum biochemistry, oxidant-antioxidant status, gross findings, organ weights, and Caesarean section findings were examined.

RESULTS

All animals survived to the end of the study. A decrease in thymus weight was observed in the highest dose group. However, maternal body weight, food consumption, serum biochemical parameters, and oxidant-antioxidant balance in the kidneys were not affected by treatment with MWCNTs. No treatment-related differences in gestational index, embryo-fetal mortality, or fetal and placental weights were observed between treated and control groups.

CONCLUSIONS

The results show that 14-day repeated oral dosing of MWCNTs during pregnancy induces minimal maternal toxicity at 1000 mg/kg/day in rats. Under these experimental conditions, the no-observed-adverse-effect level of MWCNTs is considered to be 200 mg/kg/day for dams and 1000 mg/kg/day for embryonic development.

Toxicology of nanomaterials used in nanomedicine

With the development of nanotechnology, nanomaterials are being widely used in many industries as well as in medicine and pharmacology. Despite the many proposed advantages of nanomaterials, increasing concerns have been expressed on their potential adverse human health effects. In recent years, application of nanotechnology in medicine has been defined as nanomedicine. Techniques in nanomedicine make it possible to deliver therapeutic agents into targeted specific cells, cellular compartments, tissues, and organs by using nanoparticulate carriers. Because nanoparticles possess different physicochemical properties than their fine-sized analogues due to their extremely small size and large surface area, they need to be evaluated separately for toxicity and adverse health effects. In addition, in the field of nanomedicine, intravenous and subcutaneous injections of nanoparticulate carriers deliver exogenous nanoparticles directly into the human body without passing through the normal absorption process. These nanoparticulate carriers themselves may be responsible for toxicity and interaction with biological macromolecules within the human body. Second, insoluble nanoparticulate carriers may accumulate in human tissues or organs. Therefore, it is necessary to address the potential health and safety implications of nanomaterials used in nanomedicine. Toxicological studies for biosafety evaluation of these nanomaterials will be important for the continuous development of nanomedical science. This review summarizes the current knowledge on toxicology of nanomaterials, particularly on those used in nanomedicine.

Surface-charge-dependent cell localization and cytotoxicity of cerium oxide nanoparticles

Cerium oxide nanoparticles (nanoceria) have shown great potential as antioxidant and radioprotective agents for applications in cancer therapy. Recently, various polymer-coated nanoceria preparations have been developed to improve their aqueous solubility and allow for surface functionalization of these nanoparticles. However, the interaction of polymer-coated nanoceria with cells, their uptake mechanism, and subcellular localization are poorly understood. Herein, we engineered polymer-coated cerium oxide nanoparticles with different surface charges (positive, negative, and neutral) and studied their internalization and toxicity in normal and cancer cell lines. The results showed that nanoceria with a positive or neutral charge enters most of the cell lines studied, while nanoceria with a negative charge internalizes mostly in the cancer cell lines. Moreover, upon entry into the cells, nanoceria is localized to different cell compartments (e.g., cytoplasm and lysosomes) depending on the nanoparticle's surface charge. The internalization and subcellular localization of nanoceria plays a key role in the nanoparticles' cytotoxicity profile, exhibiting significant toxicity when they localize in the lysosomes of the cancer cells. In contrast, minimal toxicity is observed when they localize into the cytoplasm or do not enter the cells. Taken together, these results indicate that the differential surface-charge-dependent localization of nanoceria in normal and cancer cells plays a critical role in the nanoparticles' toxicity profile.

Dendro[C(60)]fullerene DF-1 provides radioprotection to radiosensitive mammalian cells

In this study, the ability of the C(60) fullerene derivative DF-1 to protect radiosensitive cells from the effects of high doses of gamma irradiation was examined. Earlier reports of DF-1's lack of toxicity in these cells were confirmed, and DF-1 was also observed to protect both human lymphocytes and rat intestinal crypt cells against radiation-induced cell death. We determined that DF-1 protected both cell types against radiation-induced DNA damage, as measured by inhibition of micronucleus formation. DF-1 also reduced the levels of reactive oxygen species in the crypt cells, a unique capability of fullerenes because of their enhanced reactivity toward electron-rich species. The ability of DF-1 to protect against the cytotoxic effects of radiation was comparable to that of amifostine, another ROS-scavenging radioprotector. Interestingly, localization of fluorescently labeled DF-1 in fibroblast was observed throughout the cell. Taken together, these results suggest that DF-1 provides powerful protection against several deleterious cellular consequences of irradiation in mammalian systems including oxidative stress, DNA damage, and cell death.

MWCNTs as reinforcing agent to the hap-gel nanocomposite for artificial bone grafting

The essence of this investigation is to explore MWCNTs as reinforcing agents to strengthen Hap-Gel nanocomposites for artificial bone grafting applications without significantly compromising their biocompatibility. Hap-Gelatin composites, reinforced with various proportions of MWCNTs, were synthesized to optimize the MWCNT content in the composites which yield commendable improvement in the strength. The morphological studies reveal that the MWCNTs act as templates for nucleation of Hap crystals. The biocompatibility of MWCNT reinforced Hap-Gelatin composites were evaluated in animal model through the histopathological investigation of tissues from skin, kidney, and liver. On histopathological examination, no noticeable alteration due to toxicity was found for lower concentration of MWCNTs. Mild reversible changes in the liver and tubular damage in kidney have been observed for higher concentration (4 wt % of MWCNTs). It can be inferred from the findings that MWCNTs, in proportions less than 4%, can successfully be used to reinforce the Hap-Gel nanocomposite to improve its mechanical properties. However, how safe would these CNT reinforced bone implants would be when used for prolonged period in actual physiological conditions needs to be investigated further.

The biological mechanisms and physicochemical characteristics responsible for driving fullerene toxicity

This review provides a comprehensive critical review of the available literature purporting to assess the toxicity of carbon fullerenes. This is required as prior to the widespread utilization and production of fullerenes, it is necessary to consider the implications of exposure for human health. Traditionally, fullerenes are formed from 60 carbon atoms, arranged in a spherical cage-like structure. However, manipulation of surface chemistry and molecular makeup has created a diverse population of fullerenes, which exhibit drastically different behaviors. The cellular processes that underlie observed fullerene toxicity will be discussed and include oxidative, genotoxic, and cytotoxic responses. The antioxidant/cytoprotective properties of fullerenes (and the attributes responsible for driving these phenomena) have been considered and encourage their utilization within the treatment of oxidant-mediated disease. A number of studies have focused on improving the water solubility of fullerenes in order to enable their exploitation within biological systems. Manipulating fullerene water solubility has included the use of surface modifications, solvents, extended stirring, and mechanical processes. However, the ability of these processes to also impact on fullerene toxicity requires assessment, especially when considering the use of solvents, which particularly appear to enhance fullerene toxicity. A number of the discussed investigations were not conducted to reveal if fullerene behavior was due to their nanoparticle dimensions but instead addressed the biocompatibility and toxicity of fullerenes. The hazards to human health, associated with fullerene exposure, are uncertain at this time, and further investigations are required to decipher such effects before an effective risk assessment can be conducted.

Effects of waterborne nano-iron on medaka (Oryzias latipes): antioxidant enzymatic activity, lipid peroxidation and histopathology

Toxicity tests were performed to investigate possible harmful effects on medaka exposed to nano-iron. Dose-dependent decreases of superoxide dismutase (SOD) and increases of malondialdehyde (MDA) were induced in the medaka embryo, suggesting that oxidative damage was induced by nano-iron. For adult medaka, the disturbance of antioxidative balance was observed during the early exposure period based on the monitoring of the hepatic and cerebral SOD and reduced glutathione (GSH). No terminal oxidative damage occurred during the whole exposure period, probably due to the high self-recovering capability of the adult fish. Some histopathological and morphological alterations (cell swelling, hyperplasia, and granulomas, etc.) were observed in gill and intestine tissues, which confirmed that deleterious effects occurred as a result of direct contact with nano-iron. It is suggested that further evaluation should be made concerning the risk assessment of waterborne nano-iron on aquatic life.

In vivo biology and toxicology of fullerenes and their derivatives

Fullerenes represent a group of nanoparticles discovered in 1985. They are spherical molecules consisting entirely of carbon atoms (C(x)) to which side chains can be added, furnishing compounds with widely different properties. Fullerenes interact with biological systems, for example, by enzyme inhibition, causing phototoxic reactions, being scavengers of reactive oxygen species and free radicals, in addition to being able to initiate free radical reactions. Absorption, distribution and excretion strongly depend on the properties of the side chains. The pristine C(60) has a very long biological half-life, whereas the most water-soluble derivatives are eliminated from the exposed animals within weeks. A long biological half-life raises concern about bioaccumulation and long-term effects. In general, the acute oral, dermal and airway toxicity is low. However, few relevant experimental studies of repeated dose toxicity, reproductive toxicity and carcinogenic effect are available. The data suggest that direct DNA damaging effects are low, but formation of reactive oxygen species may cause inflammation and genetic damage. Apparently, it is dose-dependent whether a beneficial or an adverse effect occurs.

Adverse effects of fullerenes on endothelial cells: fullerenol C60(OH)24 induced tissue factor and ICAM-I membrane expression and apoptosis in vitro

We studied the effects of a C₆₀ water suspension at 4 μg/mL (nC₆₀) and the water soluble fullerenol C₆₀(OH)₂₄ at final concentrations of 1^–100 μg/mL on human umbilical vein endothelial cells (HUVECs) in culture. We found that a 24 hr treatment of HUVECs with C₆₀(OH)₂₄ at 100 μg/mL significantly increased cell surface expression of ICAM-1(CD54) (67 ± 4% CD54⁺ cells vs. 19 ± 2 % CD54⁺ cells in control; p < 0.001). In addition, this treatment induced the expression of tissue factor (CD142) on HUVECs (54 ± 20% CD142⁺ cells vs 4 ± 2% CD142⁺ cells in control; p = 0.008) and increased exposure of phosphatidylserine (PS) (29 ± 2% PS⁺ cells vs. 12 ± 5% PS⁺ cells in control; p < 0.001). Analysis of cell cycle and DNA fragmentation (TUNEL) showed that both nC₆₀ and C₆₀(OH)₂₄ caused G1 arrest of HUVECs and C₆₀(OH)₂₄ induced significant apoptosis (21 ± 2% TUNEL⁺ cells at 100 μg/mL of C₆₀(OH)₂₄ vs. 4 ± 2% TUNEL⁺ cells in control; p < 0.001). We also demonstrated that both nC₆₀ and C₆₀(OH)₂₄ induced a rapid concentration dependent elevation of intracellular calcium [Ca²⁺]_i. This could be inhibited by EGTA, suggesting that the source of [Ca²⁺]_i in fullerene stimulated calcium flux is predominantly from the extracellular environment. In conclusion, fullerenol C₆₀(OH)₂₄ had both pro-inflammatory and pro-apoptotic effects on HUVECs, indicating possible adverse effects of fullerenes on the endothelium.

Toxicity of single-walled carbon nanohorns

We extensively investigated in vitro and in vivo the toxicities of as-grown single-walled carbon nanohorns (SWNHs), a tubular nanocarbon containing no metal impurity. The SWNHs were found to be a nonirritant and a nondermal sensitizer through skin primary and conjunctival irritation tests and skin sensitization test. Negative mutagenic and clastogenic potentials suggest that SWNHs are not carcinogenic. The acute peroral toxicity of SWNHs was found to be quite low--the lethal dosage for rats was more than 2000 mg/kg of body weight. Intratracheal instillation tests revealed that SWNHs rarely damaged rat lung tissue for a 90-day test period, although black pigmentation due to accumulated nanohorns was observed. While further toxicological assessments, including chronic (repeated dose), reproductive, and developmental toxicity studies, are still needed, yet the present results strongly suggest that as-grown SWNHs have low acute toxicities.

Fullerene nanomaterials inhibit the allergic response

Fullerenes are a class of novel carbon allotropes that may have practical applications in biotechnology and medicine. Human mast cells (MC) and peripheral blood basophils are critical cells involved in the initiation and propagation of several inflammatory conditions, mainly type I hypersensitivity. We report an unanticipated role of fullerenes as a negative regulator of allergic mediator release that suppresses Ag-driven type I hypersensitivity. Human MC and peripheral blood basophils exhibited a significant inhibition of IgE dependent mediator release when preincubated with C(60) fullerenes. Protein microarray demonstrated that inhibition of mediator release involves profound reductions in the activation of signaling molecules involved in mediator release and oxidative stress. Follow-up studies demonstrated that the tyrosine phosphorylation of Syk was dramatically inhibited in Ag-challenged cells first incubated with fullerenes. In addition, fullerene preincubation significantly inhibited IgE-induced elevation in cytoplasmic reactive oxygen species levels. Furthermore, fullerenes prevented the in vivo release of histamine and drop in core body temperature in vivo using a MC-dependent model of anaphylaxis. These findings identify a new biological function for fullerenes and may represent a novel way to control MC-dependent diseases including asthma, inflammatory arthritis, heart disease, and multiple sclerosis.

Nanotechnology safety concerns revisited

Nanotechnology is an emerging science involving manipulation of matter at the nanometer scale. Due to concerns over nanomaterial risks, there has been a dramatic increase in focused safety research. The present review provides a summary of these published findings, identifying areas of agreement and discordance with regard to: (1) the potential for nanomaterial exposure, (2) the relative hazard nanomaterials pose to humans and the environment, and (3) the present deficits in our understanding of risk. Special attention is paid to study design and methodologies, offering valuable insight into the complexities encountered with nanomaterial safety assessment. Recent data highlight the impact of surface characteristics on nanomaterial biocompatibility and point to the inadequacy of the current size-dependent mechanistic paradigms, with nanoscale materials lacking unique or characteristic toxicity profiles. The available data support the ability of the lung, gastrointestinal tract, and skin to act as a significant barrier to the systemic exposure of many nanomaterials. Furthermore, the acute systemic toxicity of many nanomaterials appear to be low. By contrast, the potential pulmonary toxicity of certain nanomaterials, such as carbon nanotubes, is significant, requiring a better understanding of exposure to further evaluate their risk. While these findings arrive at an overall picture of material-specific rather than nanogeneralized risk, any conclusions should clearly be tempered by the fact that nanomaterial safety data are limited. Until such time as the exposures, hazards, and environmental life cycle of nanomaterials have been more clearly defined, cautious development and implementation of nanotechnology is the most prudent course.