Effects of acute and subchronic exposure of topically applied fullerene extracts on the mouse skin

Dextran stabilized fullerene soot induced toxicity on alveolar epithelial cells (A549 cells)

Fullerene comprises the major allotrope of carbon holding several fruitful potentials to be applied in various industrial and biomedical scenarios. Scientists have acquired large number of data on fullerene research using its derivatives like C60, C70 etc. Nevertheless, a precise focus on fullerene soot nanopaticles and its toxic impacts in living tissue is still behind mainstay even if it represents the crude parent form of all other derivatives. Present study addresses an acute toxicity profiling of fullerene soot nanoparticles in alveolar epithelial cells (A549) as a paradigm of pulmonary exposure. Surface functionalization was given for fullerene soot nanoparticles using dextran polymer as a mean to establish a stable homogenous dispersion (denoted as dFSNPs hereafter). Following functionalization, dFSNPs were characterized for various parameters including size, surface charge, morphology and functional groups using DLS, Zeta potential analysis, TEM and FT-IR measurements respectively. Effective dextran functionalization was evident from the characteristic peaks in FTIR spectra. Cell viability assessed using MTT and NRU assays; both of which showed a dose dependent cytotoxic response. Thymidine incorporation also confirmed similar trend in viability rate. In accordance with literatures, DCFHDA assay confirmed free radical scavenging activity of fullerene nanoparticles. An altered cellular morphology was observed under fluorescent microscope. Sub-cellular functionalities including lysosomal integrity and mitochondrial stability were found to be compromised at highest tested concentration of dFSNPs (160 μg/ml) without any genotoxic impacts within nuclear premises. FACS analysis following Annexin-PI staining confirmed apoptotic cell death. Hence the overall study substantiated dose dependent toxicity of dFSNPs which is likely to occur during pulmonary exposure.

Comparative study of plant responses to carbon-based nanomaterials with different morphologies

The relationship between the morphology of carbon-based nanomaterials (CBNs) and the specific response of plants exposed to CBNs has not been studied systematically. Here, we prove that CBNs with different morphologies can activate cell growth, germination, and plant growth. A tobacco cell culture growth was found to increase by 22%-46% when CBNs such as helical multi-wall carbon nanotubes (MWCNTs), few-layered graphene, long MWCNTs, and short MWCNTs were added to the growth medium at a concentration of 50 μg ml(-1). The germination of exposed tomato seeds, as well as the growth of exposed tomato seedlings, were significantly enhanced by the addition of all tested CBNs. The presence of CBNs inside exposed seeds was confirmed by transmission electron microscopy and Raman spectroscopy. The effects of helical MWCNTs on gene expression in tomato seeds and seedlings were investigated by microarray technology and real time-PCR. Helical MWCNTs affected a number of genes involved in cellular and metabolic processes and response to stress factors. It was shown that the expression of the tomato water channel gene in tomato seeds exposed to helical MWCNTs was upregulated. These established findings demonstrate that CBNs with different morphologies can cause the same biological effects and share similar mechanisms in planta.

The applications of buckminsterfullerene C60 and derivatives in orthopaedic research

Abstract Buckminsterfullerene C60 and derivatives have been extensively explored in biomedical research due to their unique structure and unparalleled physicochemical properties. C60 is characterized as a "free radical sponge" with an anti-oxidant efficacy several hundred-fold higher than conventional anti-oxidants. Also, the C60 core has a strong electron-attracting ability and numerous functional compounds with widely different properties can be added to this fullerene cage. This review focused on the applications of C60 and derivatives in orthopaedic research, such as the treatment of cartilage degeneration, bone destruction, intervertebral disc degeneration (IVDD), vertebral bone marrow disorder, radiculopathy, etc., as well as their toxicity in vitro and in vivo. We suggest that C60 and derivatives, especially the C60 cores coupled with functional groups presenting new biological and pharmacological activities, are advantageous in orthopaedic research and will be promising in clinical performance for musculoskeletal disorders treatment; however, the pharmacokinetics and toxicology of these agents as local/systemic administration need to be carefully determined.

Growth and potential damage of human bone-derived cells on fresh and aged fullerene c60 films

Fullerenes are nanoparticles composed of carbon atoms arranged in a spherical hollow cage-like structure. Numerous studies have evaluated the therapeutic potential of fullerene derivates against oxidative stress-associated conditions, including the prevention or treatment of arthritis. On the other hand, fullerenes are not only able to quench, but also to generate harmful reactive oxygen species. The reactivity of fullerenes may change in time due to the oxidation and polymerization of fullerenes in an air atmosphere. In this study, we therefore tested the dependence between the age of fullerene films (from one week to one year) and the proliferation, viability and metabolic activity of human osteosarcoma cells (lines MG-63 and U-2 OS). We also monitored potential membrane and DNA damage and morphological changes of the cells. After seven days of cultivation, we did not observe any cytotoxic morphological changes, such as enlarged cells or cytosolic vacuole formation. Furthermore, there was no increased level of DNA damage. The increasing age of the fullerene films did not cause enhancement of cytotoxicity. On the contrary, it resulted in an improvement in the properties of these materials, which are more suitable for cell cultivation. Therefore, fullerene films could be considered as a promising material with potential use as a bioactive coating of cell carriers for bone tissue engineering.

Biosafety Evaluation of Nanoparticles in View of Genotoxicity and Carcinogenicity Studies: A Systematic Review

Nanoparticles (NPs) are used in various forms in consumer products including, cosmetics, food packaging, textiles and also in air and water cleaning, production of electro chromic windows, or smart windows and gas sensors. Many NPs have also been evaluated for potential use in biomedical applications as efficient delivery carriers for cancer diagnosis and therapy. Nowadays, NPs are being developed to create fascinating nanotechnology products. To develop NPs for broad applications, potential risks to human health and the environment should be evaluated and taken into consideration. Again, to translate these nanomaterials to the clinic and industrial domains, their biosafety needs to be verified, particularly in terms of genotoxic and carcinogenic effects. To evaluate evidenced-based practices for NPs safety, we performed a systematic review of the published English-language literature. We performed a systematic keyword search of PubMed for original research articles pertaining to reports on assessment of risks due to carcinogenic and mutagenic effects by different NPs. We identified 362 original articles available for analysis. The included studies were published between 1993 and 2012. The in vivo or in vitro genotoxicity studies were performed on only 18 out of 148 kinds of NPs in industry today. Likewise, the carcinogenicity investigations were performed on only 14 out of 148 NPs. The 10 types of the NPs including some titanium, aluminium, carbon black and silver molecules were found to have both mutagenic and carcinogenic potential. The important finding was also that there is a lack of systematic assessment of the DNA damaging and carcinogenic potential of NPs in spite of their extensive use in nanotechnological applications.

Health implications of engineered nanomaterials

With the development of nanotechnology, a growing number of people are expected to be exposed to its products, the engineered nanomaterials (ENMs). Some physico-chemical properties of ENMs, linked to their size in the nanoscale (1-100 nm), make them potentially more reactive, and therefore raise concern about possible adverse effects in humans. In this article, I discuss human diseases which may be predicted after exposure to ENMs, and how their pathogenetic mechanisms may be linked to exposure; in this regard, special emphasis has been given to the triad of oxidative stress/inflammation/genotoxicity and to the interaction of ENMs/proteins in different biological compartments. The analysis of possible adverse effects has been made on an organ-by-organ basis, starting from the skin, respiratory system and gastrointestinal tract. These sites are in fact not only those exposed to the highest amounts of ENMs, but are also the portals of entry to internal organs for possible systemic effects. Although the list and the relevance of possible human disorders linked to ENM exposure are at least as impressive as that of their direct or indirect beneficial effects for human health, we must be clear that ENM-linked diseases belong to the realm of possible risk (i.e. cannot be excluded, but are unlikely), whereas ENMs with proven beneficial effects are on the market. Therefore, the mandatory awareness about possible adverse effects of ENMs should in no way be interpreted as a motivation to disregard the great opportunity represented by nanotechnology.

DNA exposure to buckminsterfullerene (C60): toward DNA stability, reactivity, and replication

Buckminsterfullerene (C(60)) has received great research interest due to its extraordinary properties and increasing applications in manufacturing industry and biomedical technology. We recently reported C(60) could enter bacterial cells and bind to DNA molecules. This study was to further determine how the DNA-C(60) binding affected the thermal stability and enzymatic digestion of DNA molecules, and DNA mutations. Nano-C(60) aggregates and water-soluble fullerenols were synthesized and their impact on DNA biochemical and microbial activity was investigated. Our results revealed that water-soluble fullerenols could bind to lambda DNA and improve DNA stability remarkably against thermal degradation at 70-85 °C in a dose-dependent manner. DNase I and HindIII restriction endonuclease activities were inhibited after interacting with fullerenols at a high dose. Experimental results also showed the different influence of fullerenol and nano-C(60) on their antibacterial mechanisms, where fullerenols contributed considerable impact on cell damage and mutation rate. This preliminary study indicated that the application of fullerenols results in significant changes in the physical structures and biochemical functions of DNA molecules.

Biological safety of liposome-fullerene consisting of hydrogenated lecithin, glycine soja sterols, and fullerene-C60 upon photocytotoxicity and bacterial reverse mutagenicity

Various water-soluble derivatives of fullerene-C60 (C60) have been developed as detoxifiers for reactive oxygen species (ROS), whereas C60 incorporated in liposome (Lpsm) has not been reported yet. We prepared the liposome-fullerene (0.2% aqueous phase, Lpsm-Flln) which was composed of hydrogenated lecithin, glycine soja (soybean) sterols, and C60 in the weight ratio of 89.7:10:0.3, then examined the photocytotoxicity and bacterial reverse mutagenicity, as comparing with the Lpsm containing no C60. Photocytoxicity of Lpsm-Flln or Lpsm was examined using Balb/3T3 fibroblastic cells at graded doses of 0.49-1000 microg/mL under the condition of UVA- or sham-irradiation. The cells were irradiated with UVA (5 J/cm2, 320-400 nm, lambda max = 360 nm) at room temperature for 50 min. The resultant cell viability (% of control) did not decrease dose-dependently to 50% or less regardless of the UVA-irradiation. These results show that Lpsm-Flln or Lpsm does not possess photocytotoxicity to Balb/3T3 fibroblasts, and Lpsm-Flln may not exert a UVA-catalytic ROS-increasing action. A possibility for the reverse mutation by Lpsm-Flln or Lpsm was examined on four histidine-demanding strains of Salmonella typhimurium and a tryptophan-demanding strain of Escherichia coli. As for the dosages of Lpsm-Flln or Lpsm (313-5000 microg/plate), the dose-dependency of the number of reverse mutation colonies of each strain did not show a twice or more difference versus the negative control regardless of the metabolic activation, and, in contrast, marked differences for five positive controls (sodium azide, N-ethyl-N'-nitro-N-nitrosoguanidine, 2-nitrofluorene, 9-aminoacridine, and 2-aminoanthracene). The growth inhibition of bacterial strains and the deposition of Lpsm-Flln or Lpsm were not found. As a result, the bacterial reverse mutagenicity of Lpsm-Flln or Lpsm was judged to be negative under the conditions of this test. Thus, Lpsm-Flln and Lpsm may not give any significant biological toxic effects, such as photocytotoxicity and bacterial reverse mutagenicity.

Lung inflammation and genotoxicity following pulmonary exposure to nanoparticles in ApoE-/- mice

BACKGROUND

The toxic and inflammatory potential of 5 different types of nanoparticles were studied in a sensitive model for pulmonary effects in apolipoprotein E knockout mice (ApoE-/-). We studied the effects instillation or inhalation Printex 90 of carbon black (CB) and compared CB instillation in ApoE-/- and C57 mice. Three and 24 h after pulmonary exposure, inflammation was assessed by mRNA levels of cytokines in lung tissue, cell composition, genotoxicity, protein and lactate dehydrogenase activity in broncho-alveolar lavage (BAL) fluid.

RESULTS

Firstly, we found that intratracheal instillation of CB caused far more pulmonary toxicity in ApoE-/- mice than in C57 mice. Secondly, we showed that instillation of CB was more toxic than inhalation of a presumed similar dose with respect to inflammation in the lungs of ApoE-/- mice. Thirdly, we compared effects of instillation in ApoE-/- mice of three carbonaceous particles; CB, fullerenes C60 (C60) and single walled carbon nanotubes (SWCNT) as well as gold particles and quantum dots (QDs). Characterization of the instillation media revealed that all particles were delivered as agglomerates and aggregates. Significant increases in Il-6, Mip-2 and Mcp-1 mRNA were detected in lung tissue, 3 h and 24 h following instillation of SWCNT, CB and QDs. DNA damage in BAL cells, the fraction of neutrophils in BAL cells and protein in BAL fluid increased statistically significantly. Gold and C60 particles caused much weaker inflammatory responses.

CONCLUSION

Our data suggest that ApoE-/- model is sensitive for evaluating particle induced inflammation. Overall QDs had greatest effects followed by CB and SWCNT with C60 and gold being least inflammatory and DNA-damaging. However the gold was used at a much lower mass dose than the other particles. The strong effects of QDs were likely due to Cd release. The surface area of the instilled dose correlated well the inflammatory response for low toxicity particles.

Fullerene water suspension (nC60) exerts antibacterial effects via ROS-independent protein oxidation

Buckminsterfullerene (C60) can form water suspensions (nC60) that exert toxic effects. While reactive oxygen species (ROS) generation has been implicated as the mechanism for mammalian cytotoxicity, we propose that nC60 exerts ROS-independent oxidative stress in bacteria, with evidence of protein oxidation, changes in cell membrane potential, and interruption of cellular respiration. This mechanism requires direct contact between the nanoparticle and the bacterial cell and differs from previously reported nanomaterial antibacterial mechanisms that involve ROS generation (metal oxides) or leaching of toxic elements (nanosilver).

Genotoxicity, cytotoxicity, and reactive oxygen species induced by single-walled carbon nanotubes and C(60) fullerenes in the FE1-Mutatrade markMouse lung epithelial cells

Viability, cell cycle effects, genotoxicity, reactive oxygen species production, and mutagenicity of C(60) fullerenes (C(60)) and single-walled carbon nanotubes (SWCNT) were assessed in the FE1-Mutatrade markMouse lung epithelial cell line. None of these particles induced cell death within 24 hr at doses between 0 and 200 microg/ml or during long-term subculture exposure (576 hr) at 100 microg/ml, as determined by two different assays. However, cell proliferation was slower with SWCNT exposure and a larger fraction of the cells were in the G1 phase. Exposure to carbon black resulted in the greatest reactive oxygen species generation followed by SWCNT and C(60) in both cellular and cell-free particle suspensions. C(60) and SWCNT did not increase the level of strand breaks, but significantly increased the level of FPG sensitive sites/oxidized purines (22 and 56%, respectively) determined by the comet assay. The mutant frequency in the cII gene was unaffected by 576 hr of exposure to either 100 microg/ml C(60) or SWCNT when compared with control incubations, whereas we have previously reported that carbon black and diesel exhaust particles induce mutations using an identical exposure scenario. These results indicate that SWCNT and C(60) are less genotoxic in vitro than carbon black and diesel exhaust particles.

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.

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.

Charge-associated effects of fullerene derivatives on microbial structural integrity and central metabolism

The effects of four types of fullerene compounds (C60, C60-OH, C60-COOH, C60-NH2) were examined on two model microorganisms (Escherichia coli W3110 and Shewanella oneidensis MR-1). Positively charged C60-NH2 at concentrations as low as 10 mg/L inhibited growth and reduced substrate uptake for both microorganisms. Scanning electron microscopy (SEM) revealed damage to cellular structures. Neutrally charged C60 and C60-OH had mild negative effects on S. oneidensis MR-1, whereas the negatively charged C60-COOH did not affect either microorganism's growth. The effect of fullerene compounds on global metabolism was further investigated using [3-13C]L-lactate isotopic labeling, which tracks perturbations to metabolic reaction rates in bacteria by examining the change in the isotopic labeling pattern in the resulting metabolites (often amino acids).1-3 The 13C isotopomer analysis from all fullerene-exposed cultures revealed no significant differences in isotopomer distributions from unstressed cells. This result indicates that microbial central metabolism is robust to environmental stress inflicted by fullerene nanoparticles. In addition, although C60-NH2 compounds caused mechanical stress on the cell wall or membrane, both S. oneidensis MR-1 and E. coli W3110 can efficiently alleviate such stress by cell aggregation and precipitation of the toxic nanoparticles. The results presented here favor the hypothesis that fullerenes cause more membrane stress 4-6 than perturbation to energy metabolism.7.

Effects of fullerene guests on the stability of 1-palmitoyl-2-oleoylphosphatidylcholine liposomes

Membrane stability of extruded large unilamellar vesicles () formed by 1-palmitoyl-2-oleoylphosphatidylcholine () containing fullerene C or an amphiphilic fullerene derivative, 2-[2-(2-fulleropyrrolidin-1-ylethoxy)-ethoxy]-ethanol (), has been investigated by spectrofluorimetrically monitoring the spontaneous release of entrapped carboxyfluorescein (). Under controlled conditions of temperature, osmolarity and pH, these guests increase the stability of the liposomal membrane as shown by the decrease in the rate of outflux of . The stability conferred to the liposomes by C and has been compared with that conferred by the well-known stabilizing guest 1,2-dipalmitoyl--glycero-3-phosphoethanolamine--[methoxy-(polyethylene glycol)-2000] ammonium salt (). The addition of amphiphilic molecules, such as non-ionic surfactants, which intercalate into the membrane bilayer, and of sucrose or NaCl, which induce a hyposmotic stress, has been extensively investigated in order to get information on how to modulate the release of entrapped . This information could hopefully be useful in the formulation of new drug delivery systems as well as for getting a deeper understanding of the mechanisms of the formation/enclosure of channels through the membrane. The viscosity and the micropolarity of the membrane have been measured fluorimetrically by using pyrene as the probe. An interesting increase of the gel-liquid crystal phase transition temperature has been observed for POPC liposomes hosting C.

Pharmacological studies on fullerene (C60), a novel carbon allotrope, and its derivatives

Fullerene (C(60)), a condensed ring aromatic compound with extended pi systems, is a novel carbon allotrope. Because of its poor solubility in polar solvents, investigation of the biological and pharmacological properties of fullerene has been difficult. Recently, water-soluble fullerene derivatives have been synthesized, and we and others have found that they have potent and selective pharmacological effects on organs, cells, enzymes, and nucleic acids. In the presence of fullerene C(60) derivative (10(-5) M), endothelium-dependent relaxations induced by agonists in the vascular system were eliminated and acetylcholine-induced contractile response of smooth muscle was observed. Some investigators have reported free radical-scavenging activity and direct nitric oxide-quenching activity of fullerene derivatives. Knowledge of the chemical modifications, biological significance, and materials applications of functionalized fullerenes is growing rapidly; and these compounds are emerging as new tools in the field. The focus of this review is to introduce several pharmacological effects of fullerenes and to discuss the possible mechanisms of the pharmacological actions caused by previously synthesized fullerenes.

Cellular effect of high doses of silica-coated quantum dot profiled with high throughput gene expression analysis and high content cellomics measurements

Quantum dots (Qdots) are now used extensively for labeling in biomedical research, and this use is predicted to grow because of their many advantages over alternative labeling methods. Uncoated Qdots made of core/shell CdSe/ZnS are toxic to cells because of the release of Cd2+ ions into the cellular environment. This problem has been partially overcome by coating Qdots with polymers, poly(ethylene glycol) (PEG), or other inert molecules. The most promising coating to date, for reducing toxicity, appears to be PEG. When PEG-coated silanized Qdots (PEG-silane-Qdots) are used to treat cells, toxicity is not observed, even at dosages above 10-20 nM, a concentration inducing death when cells are treated with polymer or mercaptoacid coated Qdots. Because of the importance of Qdots in current and future biomedical and clinical applications, we believe it is essential to more completely understand and verify this negative global response from cells treated with PEG-silane-Qdots. Consequently, we examined the molecular and cellular response of cells treated with two different dosages of PEG-silane-Qdots. Human fibroblasts were exposed to 8 and 80 nM of these Qdots, and both phenotypic as well as whole genome expression measurements were made. PEG-silane-Qdots did not induce any statistically significant cell cycle changes and minimal apoptosis/necrosis in lung fibroblasts (IMR-90) as measured by high content image analysis, regardless of the treatment dosage. A slight increase in apoptosis/necrosis was observed in treated human skin fibroblasts (HSF-42) at both the low and the high dosages. We performed genome-wide expression array analysis of HSF-42 exposed to doses 8 and 80 nM to link the global cell response to a molecular and genetic phenotype. We used a gene array containing approximately 22,000 total probe sets, containing 18,400 probe sets from known genes. Only approximately 50 genes (approximately 0.2% of all the genes tested) exhibited a statistically significant change in expression level of greater than 2-fold. Genes activated in treated cells included those involved in carbohydrate binding, intracellular vesicle formation, and cellular response to stress. Conversely, PEG-silane-Qdots induce a down-regulation of genes involved in controlling the M-phase progression of mitosis, spindle formation, and cytokinesis. Promoter analysis of these results reveals that expression changes may be attributed to the down-regulation of FOXM and BHLB2 transcription factors. Remarkably, PEG-silane-Qdots, unlike carbon nanotubes, do not activate genes indicative of a strong immune and inflammatory response or heavy-metal-related toxicity. The experimental evidence shows that CdSe/ZnS Qdots, if appropriately protected, induce negligible toxicity to the model cell system studied here, even when exposed to high dosages. This study indicates that PEG-coated silanized Qdots pose minimal impact to cells and are a very promising alternative to uncoated Qdots.

Nanotechnology and Nanotoxicology

Nanotechnology is the manipulation of matter in dimensions <100 nm. At this size, matter can take on different chemical and physical properties, giving the products characteristics useful to industry, medicine and technology. Government funding and private investors provide billions of research dollars for the development of new materials and applications. The potential utility of these technologies is such that they are expected be a trillion-dollar industry within the next 10 years. However, the novel properties of nanoengineered materials lead to the potential for different toxicity compared with the bulk material. The field of nanotoxicology is still in its infancy, however, with very limited literature regarding potential health effects. Inhalational toxicity is to be expected, given the known effects of inhaled fine particulate matter. However, the degree to which most nanoparticles will aerosolise remains to be determined. It has been proposed that dermal exposure will be the most relevant route of exposure, but there is considerably less literature regarding dermal effects and absorption. Less defined still are the potential effects of nanoproducts on fetal development and the environment.

[60]fullerene is a powerful antioxidant in vivo with no acute or subacute toxicity

In the present work, we report the effects of C(60)-pretreatments on acute carbon tetrachloride intoxication in rats, a classical model for studying free-radical-mediated liver injury. Our results show that aqueous C(60) suspensions prepared without using any polar organic solvent not only have no acute or subacute toxicity in rodents but they also protect their livers in a dose-dependent manner against free-radical damage. To be sure, according to histopathological examinations and biological tests, pristine C(60) can be considered as a powerful liver-protective agent.

Molecular characterization of the cytotoxic mechanism of multiwall carbon nanotubes and nano-onions on human skin fibroblast

The increasing use of nanotechnology in consumer products and medical applications underlies the importance of understanding its potential toxic effects to people and the environment. Although both fullerene and carbon nanotubes have been demonstrated to accumulate to cytotoxic levels within organs of various animal models and cell types and carbon nanomaterials have been exploited for cancer therapies, the molecular and cellular mechanisms for cytotoxicity of this class of nanomaterial are not yet fully apparent. To address this question, we have performed whole genome expression array analysis and high content image analysis based phenotypic measurements on human skin fibroblast cell populations exposed to multiwall carbon nano-onions (MWCNOs) and multiwall carbon nanotubes (MWCNTs). Here we demonstrate that exposing cells to MWCNOs and MWCNTs at cytotoxic doses induces cell cycle arrest and increases apoptosis/necrosis. Expression array analysis indicates that multiple cellular pathways are perturbed after exposure to these nanomaterials at these doses, with material-specific toxigenomic profiles observed. Moreover, there are also distinct qualitative and quantitative differences in gene expression profiles, with each material at different dosage levels (6 and 0.6 microg/mL for MWCNO and 0.6 and 0.06 microg/mL for MWCNT). MWCNO and MWCNT exposure activates genes involved in cellular transport, metabolism, cell cycle regulation, and stress response. MWCNTs induce genes indicative of a strong immune and inflammatory response within skin fibroblasts, while MWCNO changes are concentrated in genes induced in response to external stimuli. Promoter analysis of the microarray results demonstrate that interferon and p38/ERK-MAPK cascades are critical pathway components in the induced signal transduction contributing to the more adverse effects observed upon exposure to MWCNTs as compared to MWCNOs.

Biodegradable polymers in chondrogenesis of human articular chondrocytes

The aim of this study was to evaluate the potential role of polyglycolic acid (PGA), poly(glycolic acid-epsilon-caprolactone) (PGCL), poly(L-lactic acid-glycolic acid) (PLGA), poly(L-lactic acid-epsilon-caprolactone, 75:25 (w/w)) [P(LA-CL)25], poly-epsilon-caprolactone (tetrabutoxy titanium) [PCL(Ti)], and fullerene C-60 dimalonic acid (DMA) in cartilage transplants. After 4 weeks of culture of human articular cartilage, the levels of cell proliferation and differentiation and the expression of cartilage-specific matrix genes were estimated. The relationship between cell differentiation and gap junction protein connexin 43 (Cx43) was also evaluated. All materials except PCL(Ti) retained cell proliferation activities similar to the controls. Cell differentiation levels from the highest to the lowest were in the following order: PGA >> PLGA > PGCL > Control = DMSO > P(LA-CL)25 = PCL(Ti) >> fullerene C-60 DMA. Expression of the collagen type II gene was selectively upregulated for PGA, PGCL, and PLGA and slightly increased for P(LA-CL)25 polymers but was downregulated for fullerene C-60 DMA. Aggrecan gene expression was strongest with PGA and was consistently expressed with other matrices, especially with PGCL and PLGA. However, the expression patterns of the connexin 43 gene were different from the former two genes. Multiple regression analysis revealed a high correlation between cartilage proteoglycans production and expression levels of these three genes.

C60 binds to and deforms nucleotides

Atomistic molecular dynamics simulations are performed for up to 20 ns to monitor the formation and the stability of complexes composed of single- or double-strand DNA molecules and C60 in aqueous solution. Despite the hydrophobic nature of C60, our results show that fullerenes strongly bind to nucleotides. The binding energies are in the range -27 to -42 kcal/mol; by contrast, the binding energy of two fullerenes in aqueous solution is only -7.5 kcal/mol. We observe the displacement of water molecules from the region between the nucleotides and the fullerenes and we attribute the large favorable interaction energies to hydrophobic interactions. The features of the DNA-C60 complexes depend on the nature of the nucleotides: C60 binds to double-strand DNA, either at the hydrophobic ends or at the minor groove of the nucleotide. C60 binds to single-strand DNA and deforms the nucleotides significantly. Unexpectedly, when the double-strand DNA is in the A-form, fullerenes penetrate into the double helix from the end, form stable hybrids, and frustrate the hydrogen bonds between end-group basepairs in the nucleotide. When the DNA molecule is damaged (specifically, a gap was created by removing a piece of the nucleotide from one helix), fullerenes can stably occupy the damaged site. We speculate that this strong association may negatively impact the self-repairing process of the double-strand DNA. Our results clearly indicate that the association between C60 and DNA is stronger and more favorable than that between two C60 molecules in water. Therefore, our simulation results suggest that C60 molecules have potentially negative impact on the structure, stability, and biological functions of DNA molecules.

Research Strategies for Safety Evaluation of Nanomaterials, Part II: Toxicological and Safety Evaluation of Nanomaterials, Current Challenges and Data Needs

This article summarizes a roundtable discussion held at the 2005 Society of Toxicology Annual Meeting in New Orleans, LA. The purpose of the roundtable was to review the current challenges and data needs for conducting toxicological and safety evaluations for nanomaterials, with the goals of presenting the current state-of-the science on the safety of nanomaterials and bringing together scientists representing government, academia, and industry to identify priorities for developing data to facilitate risk assessments for these materials. In this summary, the unique physicochemical properties associated with nanomaterials are reviewed in the context of the difficulties associated with measuring and characterizing them. In addition, the development of appropriate hazard data, the collection of accurate human and environmental exposure information, and the development of a better fundamental understanding of the modes of action for nanomaterials are discussed as factors that will impact the development of comprehensive toxicological and safety evaluations.

Functionalized fullerenes in water. The first 10 years of their chemistry, biology, and nanoscience

Fullerenes are entirely insoluble in water, but suitable functionalization makes the molecules soluble. Studies on water-soluble fullerene derivatives led to the discovery of the interaction of organofullerenes with DNA, proteins, and living cells, which was first reported in the summer of 1993. Subsequent studies have revealed interesting biological activity aspects of organofullerenes owing to their photochemistry, radical quenching, and hydrophobicity to form one- to three-dimensional supramolecular complexes. In these areas of research, synthetic organic chemistry has played an important role in the creation of tailor-made molecules.

Exposure to carbon nanotube material: assessment of nanotube cytotoxicity using human keratinocyte cells

Carbon nanotubes are new members of carbon allotropes similar to fullerenes and graphite. Because of their unique electrical, mechanical, and thermal properties, carbon nanotubes are important for novel applications in the electronics, aerospace, and computer industries. Exposure to graphite and carbon materials has been associated with increased incidence of skin diseases, such as carbon fiber dermatitis, hyperkeratosis, and naevi. We investigated adverse effects of single-wall carbon nanotubes (SWCNT) using a cell culture of immortalized human epidermal keratinocytes (HaCaT). After 18 h of exposure of HaCaT to SWCNT, oxidative stress and cellular toxicity were indicated by formation of free radicals, accumulation of peroxidative products, antioxidant depletion, and loss of cell viability. Exposure to SWCNT also resulted in ultrastructural and morphological changes in cultured skin cells. These data indicate that dermal exposure to unrefined SWCNT may lead to dermal toxicity due to accelerated oxidative stress in the skin of exposed workers.

Carboxyfullerenes protect human keratinocytes from ultraviolet-B-induced apoptosis

Carboxyfullerene, a water-soluble carboxylic acid derivative of a fullerene, which acts as a free-radical scavenger, was investigated as a protective agent against ultraviolet-light-induced damage in human keratinocytes. First, we demonstrate that carboxyfullerene is not cytotoxic for these cells. In addition, this compound significantly reduces the ultraviolet-B-induced inhibition of keratinocyte proliferation and protects keratinocytes from apoptosis caused by ultraviolet B irradiation in a time- and dose-dependent fashion. Furthermore, the percentage of cells with depolarized mitochondria is significantly lower in ultraviolet-B-irradiated keratinocytes pretreated with carboxyfullerene than in cells provided with diluent alone. Carboxyfullerene also protects human keratinocytes from apoptosis induced by exposure to deoxy-D-ribose, a sugar that causes cell death through a pathway involving oxidative stress. On the other hand, ultraviolet B downregulates bcl-2 levels in human keratinocytes, and carboxyfullerene fails to prevent this effect. These results suggest that carboxy- fullerene protects human keratinocytes from ultraviolet B damage possibly via a mechanism interfering with the generation of reactive oxygen species from depolarized mitochondria without the involvement of bcl-2.

Oxidative damage induced by the fullerene C60 on photosensitization in rat liver microsomes

We have examined the ability of a commonly used fullerene, C60, to induce oxidative damage on photosensitization using rat liver microsomes as model membranes. When C60 was incorporated into rat liver microsomes in the form of its cyclodextrin complex and exposed to UV or visible light, it induced significant oxidative damage in terms of (1) lipid peroxidation as assayed by thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides and conjugated dienes, and (2) damage to proteins as assessed by protein carbonyls and loss of the membrane-bound enzymes. The oxidative damage induced was both time- and concentration-dependent. C60 plus light-induced lipid peroxidation was significantly inhibited by the quenchers of singlet oxygen ((1)O2), beta-carotene and sodium azide, and deuteration of the buffer-enhanced peroxidation. These observations indicate that C60 is an efficient inducer of peroxidation and is predominantly due to (1)O2. Biological antioxidants such as glutathione, ascorbic acid and alpha-tocopherol significantly differ in their ability to inhibit peroxidation induced by C60. Our studies, hence, indicate that C60, on photosensitization, can induce significant lipid peroxidation and other forms of oxidative damage in biological membranes and that this phenomenon can be greatly modulated by endogenous antioxidants and scavengers of reactive oxygen species.

Pharmacokinetics of a water-soluble fullerene in rats

Fullerenes are the recently discovered third allotropic form of carbon. The biological activities of these compounds are being studied for various purposes. The bis(monosuccinimide) derivative of p p'-bis(2-amino-ethyl)-diphenyl-C60 (MSAD-C60) is a water-soluble fullerene derivative. MSAD-C60 has been shown to have antiviral activity against human immunodeficiency virus types 1 and 2 in vitro and to have virucidal and anti-human immunodeficiency virus protease activities. Moreover, MSAD-C60 has been shown to be well tolerated in mice after intraperitoneal administration. The purpose of the present study was to develop a high-performance liquid chromatographic analytical methodology for MSAD-C60 and to characterize the preclinical pharmacokinetics of the compound in rats. Following intravenous administration of the fullerene derivative at a dose of 15 mg/kg of body weight, the concentrations of MSAD-C60 in plasma declined either bi- or triexponentially. The mean terminal-phase half-life of MSAD-C60 was 6.8 +/- 1.1 h (mean +/- standard deviation). Binding studies indicated that the compound is greater than 99% bound to plasma proteins. The average total clearance of the compound was 0.19 +/- 0.06 liter/h/kg. Urine samples obtained 24 h after intravenous administration did not contain detectable levels of the compound, indicating the absence of a significant renal clearance mechanism. The steady-state volume of distribution of MSAD-C60 averaged 2.1 +/- 0.8 liters/kg, indicating that the compound distributes into tissues. At a dose of 15 mg/kg, MSAD-C60 appeared to be well tolerated. However, a dose of 25 mg/kg resulted in shortness of breath and violent movement of the rats, followed by death within 5 min of dosing. Further controlled toxicity studies are needed to fully evaluate the toxicity of the compound.

Novel harmful effects of [60]fullerene on mouse embryos in vitro and in vivo

[60]Fullerene (C60) was solubilized with poly(vinylpyrrolidone) (PVP) in water, and the aqueous solution was applied to a mouse midbrain cell differentiation system. On incubation of C60 with various concentrations of PVP, cell differentiation and proliferation were potently inhibited, although weaker than the vehicle controls. C60 was clearly distributed into the yolk sac and embryos by intraperitoneal administration to pregnant mice at 50 mg/kg and had a harmful effect on both conceptuses by microscopical evaluation. This in vivo and in vitro action on embryogenesis is a novel and seriously harmful activity of C60.

Biological applications of fullerenes

Thus far, development of applications of fullerenes in biology has been hampered by the poor water solubility of fullerenes. In spite of such concerns, fullerenes have proved useful for a wide variety of biological applications. As derivatized and underivatized fullerenes continue to become increasingly available, additional applications and further development of those discussed in this article will invariably follow.

Effects of acute and short-term repeated application of fullerene C60 on agonist-induced responses in various tissues of guinea pig and rat

1. Effects of fullerene C60 in trachea, right atria, ileum and stomach (fundus) of guinea pig and vas deferens and uterus of rat were studied pharmacologically. 2. C60 (4 microM) had no direct effect in all tissues. In guinea pig trachea and heart, relaxation and positive inotropic and chronotropic actions of isoprenaline and in isolated rat vas deferens and uterus the responses on norepinephrine and oxytocin were not affected by the short-term repeated application of C60 30 mg/kg i.p. for 4 wk. 3. The pD2 values (potencies) of acetylcholine in ileum and its longitudinal muscle from guinea pig after the short-term repeated application of C60 were significantly smaller than those obtained without the application. The value of 5-hydroxytryptamine in rat stomach (fundus) also tended to be smaller than obtained without the application. 4. Atropine inhibited competitively the contractions for acetylcholine in the longitudinal muscles prepared from C60-treated and non-treated guinea pigs, and the pA2 values for atropine were not significantly different with each other. 5. These results suggest that C60 has no direct effects or antagonistic properties toward drug receptors, but sub-chronic exposure of C60 decreased responsiveness. This may be due to a change in post-receptor processes.

In vivo biological behavior of a water-miscible fullerene: 14C labeling, absorption, distribution, excretion and acute toxicity

BACKGROUND

Water-soluble fullerenes have recently been shown to exhibit considerable in vitro biological activity including cytotoxicity, site-selective DNA cleavage and inhibition of HIV protease. To assess the potential of these compounds as drugs, studies on the in vivo behavior of fullerenes are needed. We therefore set out to synthesize a radiolabeled, water-soluble fullerene, in order to obtain data on the oral absorption, distribution and excretion of this class of compounds.

RESULTS

We synthesized a 14C-labeled water-soluble [60]fullerene using dipolar trimethylenemethane, which undergoes cycloaddition to [60]fullerene. When administered orally to rats, this compound was not efficiently absorbed and was excreted primarily in the feces. When injected intravenously, however, it was distributed rapidly to various tissues, and most of the material was retained in the body after one week. The compound was also able to penetrate the blood-brain barrier. Acute toxicity of the water-miscible fullerene was found to be quite low.

CONCLUSIONS

Although the water-soluble fullerenes (and possibly their simple metabolites) are not acutely toxic, they are retained in the body for long periods, raising concerns about chronic toxic effects. The fact that fullerenes distribute rapidly to many tissues suggests that they may eventually be useful to deliver highly polar drugs through membranes to a target tissue, however, and they may even have applications in the delivery of drugs to the brain. Recent advances in fullerene synthetic chemistry may also make it possible to control fullerene absorption/excretion profiles in the future.