Pharmacokinetics of a water-soluble fullerene in rats

Carbon-based nanostructures for cancer therapy and drug delivery applications

Synthesis, design, characterization, and application of carbon-based nanostructures (CBNSs) as drug carriers have attracted a great deal of interest over the past half of the century because of their promising chemical, thermal, physical, optical, mechanical, and electrical properties and their structural diversity. CBNSs are well-known in drug delivery applications due to their unique features such as easy cellular uptake, high drug loading ability, and thermal ablation. CBNSs, including carbon nanotubes, fullerenes, nanodiamond, graphene, and carbon quantum dots have been quite broadly examined for drug delivery systems. This review not only summarizes the most recent studies on developing carbon-based nanostructures for drug delivery (e.g. delivery carrier, cancer therapy and bioimaging), but also tries to deal with the challenges and opportunities resulting from the expansion in use of these materials in the realm of drug delivery. This class of nanomaterials requires advanced techniques for synthesis and surface modifications, yet a lot of critical questions such as their toxicity, biodistribution, pharmacokinetics, and fate of CBNSs in biological systems must be answered.

Evaluation of the C60 biodistribution in mice in a micellar ExtraOx form and in an oil solution

The article is devoted to the study of the pharmacokinetics of fullerene C₆₀ in oil and micellar forms, analysis of its content in blood, liver, lungs, kidneys, heart, brain, adrenal glands, thymus, testicles, and spleen. The highest accumulation of C₆₀ was found in the liver and adrenal glands. As a result of the studies carried out, it was shown that the bioavailability of C₆₀ in the micellar form is higher than that in an oil solution.

Rational design and latest advances of codelivery systems for cancer therapy

Current treatments have limited effectiveness in treating tumors. The combination of multiple drugs or treatment strategies is widely studied to improve therapeutic effect and reduce adverse effects of cancer therapy. The codelivery system is the key to realize combined therapies. It is necessary to design and construct different codelivery systems in accordance with the variable structures and properties of cargoes and vectors. This review presented the typical design considerations about codelivery vectors for cancer therapy and described the current state of codelivery systems from two aspects: different types of vectors and collaborative treatment strategies. The commonly used loading methods of cargoes into the vectors, including physical and chemical processes, are discussed in detail. Finally, we outline the challenges and perspectives about the improvement of codelivery systems.

Evaluation of the Biodistribution of Serinolamide-Derivatized C60 Fullerene

Carbon nanoparticles have consistently been of great interest in medicine. However, there are currently no clinical materials based on carbon nanoparticles, due to inconsistent biodistribution and excretion data. In this work, we have synthesized a novel C60 derivative with a metal chelating agent (1,4,7-Triazacyclononane-1,4,7-triacetic acid; NOTA) covalently bound to the C60 cage and radiolabeled with copper-64 (t1/2 = 12.7 h). Biodistribution of the material was assessed in vivo using positron emission tomography (PET). Bingel-Hirsch chemistry was employed to functionalize the fullerene cage with highly water-soluble serinolamide groups allowing this new C60 conjugate to clear quickly from mice almost exclusively through the kidneys. Comparing the present results to the larger context of reports of biocompatible fullerene derivatives, this work offers an important evaluation of the in vivo biodistribution, using experimental evidence to establish functionalization guidelines for future C60-based biomedical platforms.

Striking Effect of Polymer End-Group on C60 Nanoparticle Formation by High Shear Vibrational Milling with Alkyne-Functionalized Poly(2-oxazoline)s

Buckminsterfullerene (C₆₀) has a large potential for biomedical applications. However, the main challenge for the realization of its biomedical application potential is to overcome its extremely low water solubility. One approach is the coformulation with biocompatible water-soluble polymers, such as poly(2-oxazoline)s (PAOx), to form water-soluble C₆₀ nanoparticles (NPs). However, uniform and defined NPs have only been obtained via a thin film hydration method or using cyclodextrin-functionalized PAOx. Here, we report the mechanochemical preparation of defined and stable C₆₀:PAOx NPs by the introduction of a simple alkyne group as a polymer end-group. The presence of this alkyne bond is proven to be crucial in the mechanochemical synthesis of stable, defined sub-100 nm C₆₀:PAOx NPs, with high C₆₀ content up to 8.9 wt %.

Pharmacokinetics and Toxicology of the Neuroprotective e,e,e-Methanofullerene(60)-63-tris Malonic Acid [C3] in Mice and Primates

BACKGROUND AND OBJECTIVES

Fullerene-based compounds are a novel class of molecules being developed for a variety of biomedical applications, with nearly 1000 publications in this area in the last 4 years alone. One such compound, the e,e,e-methanofullerene(60)-63-tris malonic acid (designated C3), is a potent catalytic superoxide dismutase mimetic which has shown neuroprotective efficacy in a number of animal models of neurologic disease, including Parkinsonian Macaca fascicularis monkeys. The aim of this study was to characterize its toxicity and pharmacokinetics in mice and monkeys.

METHODS

To assess pharmacokinetics in mice, we synthesized and administered 14C-C3 to mice using various routes of delivery, including orally. To assess potential toxicity in primates, serial blood studies and electrocardiograms (ECGs) were obtained from monkeys treated with C3 (3 or 7 mg/kg/day) for 2  months.

RESULTS AND CONCLUSIONS

The plasma half-life of C3 was 8.2 ± 0.2 h, and there was wide tissue distribution, including uptake into brain. The compound was cleared by both hepatic and renal excretion. C3 was quite stable, with minimal metabolism of the compound even after 7 days of treatment. The LD50 in mice was 80 mg/kg for a single intraperitoneal injection, and was > 30 mg/kg/day for sustained administration; therapeutic doses are 1-5 mg/kg/day. For primates, no evidence of renal, hepatic, electrolyte, or hematologic abnormalities were noted, and serial ECGs demonstrated no alteration in cardiac electrical activity. Thus, doses of C3 that have therapeutic efficacy appear to be well tolerated after 2 years (mice) or 2 months (non-human primates) of treatment.

Mechanochemical Preparation of Stable Sub-100 nm γ-Cyclodextrin:Buckminsterfullerene (C60) Nanoparticles by Electrostatic or Steric Stabilization

Buckminster fullerene (C₆₀ )'s main hurdle to enter the field of biomedicine is its low bioavailability, which results from its extremely low water solubility. A well-known approach to increase the water solubility of C₆₀ is by complexation with γ-cyclodextrins. However, the formed complexes are not stable in time as they rapidly aggregate and eventually precipitate due to attractive intermolecular forces, a common problem in inclusion complexes of cyclodextrins. In this study we attempt to overcome the attractive intermolecular forces between the complexes by designing custom γ-cyclodextrin (γCD)-based supramolecular hosts for C₆₀ that inhibit the aggregation found in native γCD-C₆₀ complexes. The approach entails the introduction of either repulsive electrostatic forces or increased steric hindrance to prevent aggregation, thus enhancing the biomedical application potential of C₆₀ . These modifications have led to new sub-100 nm nanostructures that show long-term stability in solution.

The QSAR and docking calculations of fullerene derivatives as HIV-1 protease inhibitors

The inhibition of HIV-1 protease is considered as one of the most important targets for drug design and the deactivation of HIV-1. In the present work, the fullerene surface (C60) is modified by adding oxygen atoms as well as hydroxymethylcarbonyl (HMC) groups to form 6 investigated fullerene derivative compounds. These compounds have one, two, three, four or five O atoms+HMC groups at different positions on phenyl ring. The effect of the repeating of these groups on the ability of suggested compounds to inhibit the HIV protease is studied by calculating both Quantitative Structure Activity Relationship (QSAR) properties and docking simulation. Based on the QSAR descriptors, the solubility and the hydrophilicity of studied fullerene derivatives increased with increasing the number of oxygen atoms+HMC groups in the compound. While docking calculations indicate that, the compound with two oxygen atoms+HMC groups could interact and binds with HIV-1 protease active site. This is could be attributed to the active site residues of HIV-1 protease are hydrophobic except the two aspartic acids. So that, the increase in the hydrophilicity and polarity of the compound is preventing and/or decreasing the hydrophobic interaction between the compound and HIV-1 protease active site.

Fullerene-biomolecule conjugates and their biomedicinal applications

Fullerenes are among the strongest antioxidants and are characterized as “radical sponges.” The research on biomedicinal applications of fullerenes has achieved significant progress since the landmark publication by Friedman et al in 1993. Fullerene–biomolecule conjugates have become an important area of research during the past 2 decades. By a thorough literature search, we attempt to update the information about the synthesis of different types of fullerene–biomolecule conjugates, including fullerene-containing amino acids and peptides, oligonucleotides, sugars, and esters. Moreover, we also discuss in this review recently reported data on the biological and pharmaceutical utilities of these compounds and some other fullerene derivatives of biomedical importance. While within the fullerene–biomolecule conjugates, in which fullerene may act as both an antioxidant and a carrier, specific targeting biomolecules conjugated to fullerene will undoubtedly strengthen the delivery of functional fullerenes to sites of clinical interest.

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.

Beyond nC60: strategies for identification of transformation products of fullerene oxidation in aquatic and biological samples

Owing to their exceptional properties and versatility, fullerenes are in widespread use for numerous applications. Increased production and use of fullerenes will inevitably result in accelerated environmental release. However, study of the occurrence, fate, and transport of fullerenes in the environment is complicated because a variety of surface modifications can occur as a result of either intentional functionalization or natural processes. To gain a better understanding of the effect and risk of fullerenes on environmental health, it is necessary to acquire reliable data on the parent compounds and their congeners. Whereas currently established quantification methods generally focus on analysis of unmodified fullerenes, we discuss in this review the occurrence and analysis of oxidized fullerene congeners (i.e., their corresponding epoxides and polyhydroxylated derivatives) in the environment and in biological specimens. We present possible strategies for detection and quantification of parent nanomaterials and their various derivatives.

Lack of hydroxylated fullerene toxicity after intravenous administration to female Sprague-Dawley rats

Hydroxylated fullerenes (C₆₀OH(x)) or fullerols are water-soluble carbon nanoparticles that have been explored for potential therapeutic applications. This study assesses acute in vivo tolerance in 8-wk-old female Sprague-Dawley rats to intravenous (iv) administration of 10 mg/kg of well-characterized C₆₀(OH)₃₀. Complete histopathology and clinical chemistries are assessed at 8, 24, and 48 h after dosing. Minor histopathology changes are seen, primarily in one animal. No clinically significant chemistry changes were observed after treatment. These experiments suggest that this fullerol was well tolerated after iv administration to rats.

NEW PORPHYRIN ADDUCT OF FULLERENE-C60: A PROMISING NANOTOOL FOR MEDICINAL USE IN THE HEART MUSCLE HYPOXIA CASES

This is a first case ever reported on the fullerene-based low toxic nanocationite particles (porphyrin adducts of cyclohexl fullerene- C60) designed for targeted delivery of the paramagnetic magnesium stable isotope to the heart muscle providing a sharp clinical effect close to about 80% recovery of the tissue hypoxia symptoms in less than 24 h after a single injection (0.03–0.1 LD50). A whole principle of this therapy is novel:25Mg2+-magnetic isotope effect selectively stimulates the ATP over-production in the oxygen-depleted cell due to25Mg2+released by nanoparticles. Being membranotropic cationites, these "smart nanoparticles" release the over-activating paramagnetic cations only in response to the metabolic acidic shift. The resulting positive changes in the heart cell energy metabolism may help to prevent and/or treat the local myocardial hypoxic disorders and, hence, to protect the heart muscle from a serious damage in a vast variety of the hypoxia-caused clinical situations including both Doxorubicin and 1-methylnicotineamide cardiotoxic side effects. Both pharmacokinetics and pharmacodynamics of the drug proposed makes it suitable for safe and efficient administration in either single or multi-injection (acute or chronic) therapeutic schemes.

Carbon nanotubes and pleural damage: perspectives of nanosafety in the light of asbestos experience

Carbon nanotubes are molecular-scale one-dimensional manufactured materials which display several potential applications in engineering and materials science. Burgeoning evidence demonstrates that carbon nanotubes and asbestos share comparable physical properties. Therefore carbon nanotubes might display toxic effects and the extent of the toxicity is more specifically directed to lung and pleura. These effects are related to properties of carbon nanotubes, such as their structure, length, aspects ratio, surface area, degree of aggregation, extent of oxidation, bound functional group, method of manufacturing, concentration and dose. At the present there is no global agreement about the risk of carbon nanotubes on human health and in particular on their transformation capacity. Safety concerns regarding carbon nanotubes can be ameliorated. In this context, it is important to put the known hazards of carbon nanotubes into perspective. Here is presented an overview about toxicity issues in the application of carbon nanotubes to biological systems, taking into consideration the already known asbestos-induced mechanisms of biological damages.

Toxicogenomics to improve comprehension of the mechanisms underlying responses of in vitro and in vivo systems to nanomaterials: a review

Engineered nanomaterials are commonly defined as materials with at least one dimension of 100 nanometers or less. Such materials typically possess nanostructure-dependent properties (e.g., chemical, mechanical, electrical, optical, magnetic, biological), which make them desiderable for commercial or medical application. However, these same properties may potentially lead to nanostructure-dependent biological activity that differs from and is not directly predicted by the bulk properties of the constitutive chemicals and compounds. Nanoparticles and nanomaterials can be on the same scale of living cells components, including proteins, nucleic acids, lipids and cellular organelles. When considering nanoparticles it must be asked how man-made nanostructures can interact with or influence biological systems. Carbon nanotubes (CNTs) are an example of carbon-based nanomaterial, which has won a huge spreading in nanotechnology. The incorporation of CNTs in living systems has raised many concerns because of their hydrophobicity and tendency to aggregate and accumulate into cells, organs, and tissues with dangerous effects. Applications of toxicogenomics to both investigative and predictive toxicology will contribute to the in-depth investigation of molecular mechanisms or the mode of nanomaterials action that is achieved by using conventional toxicological approaches. Parallel toxicogenomic technologies will promote a valuable platform for the development of biomarkers, in order to predict possible nanomaterial's toxicity. The potential of characteristic gene expression profiles ("fingerprint") of exposure or toxicological response to nanoparticles will be discussed in the review to enhance comprehension of the molecular mechanism of in vivo and in vitro system exposed to nanomaterials.

Evaluation of extraction methods for quantification of aqueous fullerenes in urine

There is a growing concern about the human and environmental health effects of fullerenes (e.g., C(60)) due to their increasing application in research, medicine, and industry. Toxicological and pharmacokinetic research requires standard methods for extraction and detection of fullerenes from biological matrices such as urine. The present study validates the use of liquid-liquid extraction (LLE) and solid-phase extraction (SPE) methods in conjunction with liquid chromatography-mass spectrometry (LC-MS) for the quantitative determination of C(60) in human and synthetic urine as compared with ultrapure water. Glacial acetic acid, which is necessary to prevent emulsions during LLE, inhibited C(60) detection by LC-MS, but this could be mitigated with evaporation. Aqueous C(60) aggregates (nC(60)) were spiked at 180 μg/L into the components of a synthetic urine recipe to determine their individual impacts on extraction and detection. Urea, creatinine, and a complex protein (i.e., gelatin) were found to impair SPE, leading to a low recovery rate of 43 ± 4% for C(60) spiked into human urine. In contrast, C(60) was consistently recovered from synthetic matrices using LLE, and recovery in human urine was 80 ± 6%. These results suggest that LLE combined with LC-MS is suitable for studying the clearance of fullerenes from the body. LLE is a robust technique that holds promise for extracting C(60) from other complex biological matrices (e.g., blood, sweat, amniotic fluid) in toxicological studies, enabling a better understanding of the behavior of fullerenes in human and animal systems and facilitating a more comprehensive risk evaluation of fullerenes.

Strategies for quantifying C(60) fullerenes in environmental and biological samples and implications for studies in environmental health and ecotoxicology

Fullerenes are sphere-like molecules with unique physico-chemical properties, which render them of particular interest in biomedical research, consumer products and industrial applications. Human and environmental exposure to fullerenes is not a new phenomenon, due to a long history of hydrocarbon-combustion sources, and will only increase in the future, as incorporation of fullerenes into consumer products becomes more widespread for use as anti-aging, anti-bacterial or anti-apoptotic agents.An essential step in the determination of biological effects of fullerenes (and their surface-functionalized derivatives) is establishment of exposure-assessment techniques. However, in ecotoxicological studies, quantification of fullerenes is performed infrequently because robust, uniformly applicable analytical approaches have yet to be identified, due to the wide variety of sample types. Moreover, the unique physico-chemistry of fullerenes in aqueous matrices requires reassessment of conventional analytical approaches, especially in more complex biological matrices (e.g., urine, blood, plasma, milk, and tissue).Here, we present a review of current analytical approaches for the quantification of fullerenes and propose a consensus approach for determination of these nanomaterials in a variety of environmental and biological matrices.

Effects of aqueous stable fullerene nanocrystals (nC60) on Daphnia magna: evaluation of sub-lethal reproductive responses and accumulation

Concerns exist regarding the inadvertent release of engineered nanomaterials into natural systems, and the possible negative ecosystem response that may occur. Understanding sub-lethal effects may be particularly important to determining ecosystem responses as current levels of nanomaterial release are low compared to levels projected for the future. In this work, the sub-lethal effects and bioaccumulation of water stable, nanocrystalline fullerenes as C60, (termed nC60) were studied in Daphnia magna, a globally distributed, parthenogenetic zooplankton. Sub-lethal concentrations were first determined for both mature mother (LD50=0.4 mg L(-1)) and neonate (gestating) daphnids (0.2 mg L(-1)) in standard 48 h exposure tests. Subsequent experiments focused on the accumulation and effects (at temperatures of 18-28 degrees C) of nC60, during the D. magna reproductive cycle. The results demonstrate that upon sub-lethal exposure, the mortality rates of gestating daphnids increased with time and developmental stage. The maturation of daughter daphnids was negatively impacted. The mother daphnids were unable to reproduce again after exposure during pregnancy, and differential bioaccumulation occurred as a function of lipid content in the daphnia with the highest accumulation level of 7000 mg kg(-1) wet weight. Taken together, these results not only describe the accumulation and sub-lethal effects of nC60 on exposed daphnia, but also highlight the importance of sub-lethal exposure scenarios, which are critical to fully understanding the potential impact of fullerenes and other engineered nanoscale materials on natural systems.

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.

Manufactured nanoparticles: their uptake and effects on fish--a mechanistic analysis

There is an emerging literature reporting toxic effects of manufactured nanomaterials (NMs) and nanoparticles (NPs) in fish, but the mechanistic basis of both exposure and effect are poorly understood. This paper critically evaluates some of the founding assumptions in fish toxicology, and likely mechanisms of absorption, distribution, metabolism and excretion (ADME) of NPs in fish compared to other chemicals. Then, using a case study approach, the paper compares these assumptions for two different NPs; TiO2 and C60 fullerenes. Adsorption of NPs onto the gill surface will involve similar processes in the gill microenvironment and mucus layer to other substances, but the uptake mechanisms for NPs by epithelial cells are more likely to occur via vesicular processes (e.g., endocytosis) than uptake on membrane transporters or by diffusion through the cell membranes. Target organs may include the gills, gut, liver and sometimes the brain. Information on metabolism and excretion of NPs in fish is limited; but hepatic excretion into the bile seems a more likely mechanism, rather than mainly by renal or branchial excretion. TiO2 and C60 share some common chemical properties that appear to be associated with some similar toxic effects, but there are also differences, that highlight the notion that chemical reactivity can inform toxic effect of NPs in a fundamentally similar way to other chemicals. In this paper we identify many knowledge gaps including the lack of field observations on fish and other wildlife species for exposure and effects of manufactured NMs. Systematic studies of the abiotic factors that influence bioavailability, and investigation of the cell biology that informs on the mechanisms of metabolism and excretion of NMs, will greatly advance our understanding of the potential for adverse effects. There are also opportunities to apply existing tools and techniques to fundamental studies of fish toxicology with NPs, such as perfused organs and fish cell culture systems.

Cytotoxicity of aggregated fullerene C60 particles on CHO and MDCK cells

The cytotoxicity of fullerene C60 particles on two mammalian cell lines, i.e. the Chinese hamster ovary (CHO) cells and the Madin-Darby canine kidney (MDCK) cells, has been investigated. Although innate fullerene particles have a very low solubility in deionized (DI) water, these particles can be dissolved in the tetrahydrofuran (THF) solvent at a great value. Further, the dissolved fullerene particles in the THF solvent could be extracted into a DI water solution at a significantly increased solubility. The formation of fullerene particle aggregates is believed to be the cause of the increased solubility. Results presented here show that once the concentration of the fullerene aggregates reaches a certain level, the cells start to die. The lethal dosage LD50, which is defined as the lowest fullerene concentration that results in a 50% cell death within 24 h, has been determined. Furthermore, the percentage of cell mortality increased with increasing fullerene concentration and incubation time yielding a negative effect on cell viability. These results, illustrated by atomic force microscopy (AFM), dynamic light scattering (DLS) and other microscopic techniques, will help to better understand the side effects of fullerene particles in mammalian cells.

What do we (need to) know about the kinetic properties of nanoparticles in the body?

Nowadays the development and applications of nanotechnology are of major importance in both industrial and consumer areas. However, the knowledge on human exposure and possible toxicity of nanotechnology products is limited. To understand the mechanism of toxicity, thorough knowledge of the toxicokinetic properties of nanoparticles is warranted. There is a need for information on the absorption, distribution, metabolism and excretion (ADME) of nanoparticles and validated detection methods of these man-made nanoparticles. Determination of the ADME properties of nanoparticles requires specialised detection methods in different biological matrices (e.g. blood and organs). In this paper, the current knowledge on the kinetic properties of nanoparticles is reviewed. Moreover, knowledge gaps from a kinetic point of view (detection, dose, ADME processes) are identified.

Trace analysis of fullerenes in biological samples by simplified liquid–liquid extraction and high-performance liquid chromatography

Fullerene (C60) has several potential biomedical and industrial applications. While pure fullerene is not soluble in water, nanoparticles of the fullerene aggregates (nano-C60) can be prepared in water solutions. The concentration of nano-C(60) in biological media after systemic exposure could be very low and requires trace analytical methods to be developed for the toxicological and pharmacokinetic studies of the nanomaterial. A serious drop in extraction efficiency was observed when the concentration was under 0.5 microg/mL using traditional liquid-liquid extraction (LLE) protocols. The evaporation of the solvent extract to dryness was found to be the main reason for the efficiency drop and an improved evaporation method was proposed to overcome this problem. Optimal proportion of glacial acetic acid (GAA) was used to solublize the proteins and surfactants in the biological samples, so that the emulsion problem was eliminated during LLE. Magnesium perchlorate was used to destabilize the nano-C60 particles in the water solution and promoted the solvent extraction. A simplified LLE method was developed for high throughput while preserved the advantages of the traditional LLE. The developed method was used for trace analysis of fullerenes in protein containing media and tape-stripped skin samples. Under optimal experimental conditions, the detection limit was 0.34 ng/mL and the recovery was in the range of 94-100% (n=5) at a concentration of 10 ng/mL nano-C60 in the biological media.

Preclinical studies on safety of fullerene upon acute oral administration and evaluation for no mutagenesis

Fullerenes characterized as an antioxidant are believed to reduce various reactive chemical species, such as free radicals, and their characteristic features have been disclosed to furnish many useful medical technologies. Despite the numerous applications for the biological efficacy of fullerenes, less is known about the toxicity of fullerenes in mammals. Hence, the protocol was designed to determine the acute oral median lethal dose and evaluate the acute toxicity of fullerenes when administrated as a single dose to Sprague-Dawley rats. In an acute toxicity test, fullerenes were administered once orally to a single group of male and female at a dose level of 2000 mg/kg. No deaths were observed and the body weights in both sexes of 2000 mg/kg group increased in a similar pattern to the control group. Genotoxicity of fullerenes was also assessed in a bacterial reverse mutation assay (Ames test) and the chromosomal aberration test in cultured Chinese hamster lung (CHL/IU) cells. Although structural chromosomal aberrations were induced at up to 5000 microg/mL, there was no significant increase in the frequency of chromosomal aberrations at any dose level regardless of presence of S9. Fullerenes did not cause genetic damage in Salmonella typhimurium TA100, TA1535, TA98 and TA1537 and Escherichia coli WP2uvrA/pKM101. These results indicate that fullerenes are not of high toxicological significance.

Tissue biodistribution and blood clearance rates of intravenously administered carbon nanotube radiotracers

Carbon nanotubes (CNT) are intensively being developed for biomedical applications including drug and gene delivery. Although all possible clinical applications will require compatibility of CNT with the biological milieu, their in vivo capabilities and limitations have not yet been explored. In this work, water-soluble, single-walled CNT (SWNT) have been functionalized with the chelating molecule diethylentriaminepentaacetic (DTPA) and labeled with indium ((111)In) for imaging purposes. Intravenous (i.v.) administration of these functionalized SWNT (f-SWNT) followed by radioactivity tracing using gamma scintigraphy indicated that f-SWNT are not retained in any of the reticuloendothelial system organs (liver or spleen) and are rapidly cleared from systemic blood circulation through the renal excretion route. The observed rapid blood clearance and half-life (3 h) of f-SWNT has major implications for all potential clinical uses of CNT. Moreover, urine excretion studies using both f-SWNT and functionalized multiwalled CNT followed by electron microscopy analysis of urine samples revealed that both types of nanotubes were excreted as intact nanotubes. This work describes the pharmacokinetic parameters of i.v. administered functionalized CNT relevant for various therapeutic and diagnostic applications.

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.

Relative risk analysis of several manufactured nanomaterials: an insurance industry context

A relative risk assessment is presented for the industrial fabrication of several nanomaterials. The production processes for five nanomaterials were selected for this analysis, based on their current or near-term potential for large-scale production and commercialization: single-walled carbon nanotubes, bucky balls (C60), one variety of quantum dots, alumoxane nanoparticles, and nano-titanium dioxide. The assessment focused on the activities surrounding the fabrication of nanomaterials, exclusive of any impacts or risks with the nanomaterials themselves. A representative synthesis method was selected for each nanomaterial based on its potential for scaleup. A list of input materials, output materials, and waste streams for each step of fabrication was developed and entered into a database that included key process characteristics such as temperature and pressure. The physical-chemical properties and quantities of the inventoried materials were used to assess relative risk based on factors such as volatility, carcinogenicity, flammability, toxicity, and persistence. These factors were first used to qualitatively rank risk, then combined using an actuarial protocol developed by the insurance industry for the purpose of calculating insurance premiums for chemical manufacturers. This protocol ranks three categories of risk relative to a 100 point scale (where 100 represents maximum risk): incident risk, normal operations risk, and latent contamination risk. Results from this analysis determined that relative environmental risk from manufacturing each of these five materials was comparatively low in relation to other common industrial manufacturing processes.

Reaction of hydroxyfullerene with metal salts: a route to remediation and immobilization

Hydroxylated fullerene reacts rapidly and irreversibly (across a wide pH range) with Fe(NO3)3, Al(NO3)3, CaCl2, CoCl2, CuCl2, KMnO4, Ag(NO3), and ZnCl2 under ambient aqueous conditions to produce insoluble metal-hydroxyfullerene cross-linked polymers (M-fullerenol). Materials have been characterized by SEM, TEM, AFM, XPS, and UV-visible spectroscopy. Molecular mechanics calculations on the model systems, [Fe(C60O2)2] and [Fe(C60O2)3], show that both tetrahedral and octahedral coordination are possible. The rate of precipitation reaction is proportional to the concentration of both reagents. The interaction of hydroxyfullerenes with metals is an important issue with regard to waste treatment, fullerene exposure in the environment, and fullerene-based pharmaceutical agents.

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.

Detection of nanometer-sized particles in living cells using modern fluorescence fluctuation methods

Nanosized materials are increasingly used in medicine and biotechnology but originate also from various aerosol sources. A detailed understanding of their interaction with cells is a prerequisite for specific applications and appraisal of hazardous effects. Fluorescence fluctuation methods are applied to follow the time-course of the translocation and distribution of fluorescent 20 nm polystyrene nanoparticles with negative surface charges in HeLa cells under almost physiological conditions. The experimental results demonstrate that singular particles enter the cell without significant contribution by endocytotic mechanisms and are distributed within the cytoplasm. Subsequently aggregation is observed, which can be blocked by cytotoxins, like Genistein and Cytochalasin B, interfering with cellular uptake processes. The observed non-active uptake is due to non-specific interactions with the cell surface and could be responsible for distribution of nanometer-sized materials in tissue.

Synthesis and water solubility of adamantyl-OEG-fullerene hybrids

[reaction: see text] A series of new adamantyl-oligoethyleneglycol-fullerene hybrids was prepared via Bingel-Hirsch functionalization of the C60 fullerene with various adamantyl-oligoethyleneglycol malonates. As NMDA-targeted antioxidants, these compounds may have the potential to be developed as therapeutic agents for the treatment of neurological disorders.

The potential environmental impact of engineered nanomaterials

With the increased presence of nanomaterials in commercial products, a growing public debate is emerging on whether the environmental and social costs of nanotechnology outweigh its many benefits. To date, few studies have investigated the toxicological and environmental effects of direct and indirect exposure to nanomaterials and no clear guidelines exist to quantify these effects.

Preparation of (99m)Tc-C(60)(OH)(x) and its biodistribution studies

The biological behavior of fullerene derivatives shows their considerable potential for medical applications. In order to provide a C(60) derivative for biodistriburtion studies, the (99m)Tc-labeling of C(60)(OH)(x) was optimized. Gamma counting and single photon emission computed tomography (SPECT) were used to assess the biodistribution of the (99m)Tc-labeled compound in mice and rabbits. Biodistribution studies in mice and imaging of rabbits indicated that (99m)Tc-C(60)(OH)(x) was widely distributed in all tissues. A significant percentage of total activity was retained for 48 h, particularly in the kidneys, bone, spleen, and liver. All tissues displayed a slow clearance over 48 h, except for bone, which showed slightly increasing localization within 24 h.

In vitro action of carboxyfullerene

Fullerene compounds have avid reactivity with free radicals and are regarded as 'radical sponges'. The trimalonic acid derivative of fullerene is one of the water-soluble compounds that has been synthesized and found to be an effective antioxidant both in vivo and in vitro. Carboxyfullerene has been shown to be effective in the treatment of both Gram-positive and -negative infections, although its mode of action is poorly understood. We determined the MIC and minimal bactericidal concentration of carboxyfullerene for 20 isolates, including Staphylococcus spp., Streptococcus spp., Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Klebsiella pneumoniae. We further investigated the action of carboxyfullerene using transmission electron microscopy (TEM), anticarboxyfullerene antibody binding assay and a membrane perturbation assay. All Gram-positive species were inhibited by < or = 50 mg/L of carboxyfullerene, whereas Gram-negative species were not inhibited, even at 500 mg/L carboxyfullerene. Bactericidal activity was demonstrated only for Gram-positive species, particularly for Streptococcus pyogenes A-20, which was killed rapidly. Intercalation of carboxyfullerene into the cell wall of staphylococci and streptococci was demonstrated by TEM and anti-carboxyfullerene binding assay. Damage to the cell membrane in Gram-positive, but not Gram-negative, bacteria was confirmed by the membrane perturbation assay. These findings indicate that the action of carboxyfullerene on Gram-positive bacteria is achieved by insertion into the cell wall and destruction of membrane integrity.

Fullerene-based amino acids and peptides

Recent advances in the chemistry of fullerene have allowed the synthesis of many classes of novel fullerene derivatives. Among these classes, fullerene-based amino acids and peptides are particularly interesting, both for structural studies and biological applications. In this review, we will discuss our own achievements in this rapidly growing field. In particular, the application of fulleroproline (Fpr) amino acids and peptides to medicinal chemistry and material science will be highlighted.