Visible light-switched cytosol release of siRNA by amphiphilic fullerene derivative to enhance RNAi efficacy in vitro and in vivo

Cationic macromolecules are attractive for use as small interfering RNA (siRNA) carriers due to their performance in non-immunological reactions, customization during synthesis, and low costs compared to viral carriers. However, their low transfection efficiency substantially hinders their application in both clinical practices and academic research, which is mostly attributable to the low capacity of siRNA/cationic macromolecule complexes to escape lysosomes. To address this challenge, we designed an amphiphilic fullerene derivative (C₆₀-Dex-NH₂) for efficient and controllable siRNA delivery. To synthesize C₆₀-Dex-NH₂, terminally aminated dextran was conjugated to C₆₀. The conjugate was further cationized by covalently introducing ethylenediamine to the dextran. The physicochemical characteristics of C₆₀-Dex-NH₂ was examined with elemental analyses, gel permeation chromatography, solid-state nuclear magnetic resonance (¹³C, HPDEC), agarose gel electrophoresis, and dynamic light scattering. The cytotoxicity, cellular uptake, intracellular distribution, and in vitro RNA interference (RNAi) of siRNA/C₆₀-Dex-NH₂ complex was evaluated in the human breast cancer cell line MDA-MB-231. The RNAi efficiencies mediated by C₆₀-Dex-NH₂in vivo was evaluated in subcutaneous tumor-bearing mice. The results showed that C₆₀-Dex-NH₂ has a specific amphiphilic skeleton and could form micelle-like aggregate structures in water, which could prevent siRNA from destroying by reactive oxygen species (ROS). When exposed to visible light, C₆₀-Dex-NH₂ could trigger controllable ROS generation which could destroy the lysosome membrane, promote the lysosomal escape, and enhance the gene silencing efficiency of siRNA in vitro and in vivo. The gene silencing efficiency could reach a maximum of 53% in the MDA-MB-231-EGFP cells and 69% in the 4T1-GFP-Luc2 tumor-bearing mice.

STATEMENT OF SIGNIFICANCE

We designed a novel photosensitive amphiphilic carrier (C₆₀-Dex-NH₂) for efficient and controllable siRNA delivery, which can be used in gene therapy. We showed that C₆₀-Dex-NH₂ could destroy lysosome membrane via controllable generation of ROS when exposed to light, which can help siRNA to escape from lysosome before degradation. This can enhance the gene silencing efficiency significantly and provides a useful way to regulate RNAi efficiency by light. One advantage for C₆₀-Dex-NH₂ system is C₆₀ has broad absorbance spectrum and can be activated by weak visible light; Furthermore, C₆₀-Dex-NH₂ has a specific amphiphilic structure, which may prevent siRNA from degrading and allows C₆₀-Dex-NH₂ to embed into the lipid membrane of lysosome to improve the ROS induced lysosomal disturbance after internalization.

Synthesis and characterization of Fullerene modified ZnAlTi-LDO in photo-degradation of Bisphenol A under simulated visible light irradiation

In this study, ZnAlTi layered double hydroxide (ZnAlTi-LDH) combined with fullerene (C₆₀) was fabricated by the urea method, and calcined under vacuum atmosphere to obtain nanocomposites of C₆₀-modified ZnAlTi layered double oxide (ZnAlTi-LDO). The morphology, structure and composition of the nanocomposites were analyzed by Scanning Electron Microscopy, High-resolution transmission electron microscopy, X-ray diffraction patterns, Fourier transform infrared and specific surface area. The UV-vis diffuse reflectance spectra indicated that the incorporation of C₆₀ expanded the absorption of ZnAlTi-LDO to visible-light region. The photo-degradation experiment was conducted by using a series of C₆₀ modified ZnAlTi-LDO with different C₆₀ weight percentage to degrade Bisphenol A (BPA) under simulated visible light irradiation. In this experiment, the degradation rate of C₆₀ modified ZnAlTi-LDO in photo-degradation of BPA under simulated visible light irradiation was over 80%. The intermediates formed in the degradation of BPA process by using LDO/C₆₀-5% were 4-hydroxyphenyl-2-propanol, 4-isopropenylphenol and Phenol. Photogenerated holes, superoxide radical species, ·OH and singlet oxygen were considered to be responsible for the photodegradation process, among which superoxide radical species and ·OH played a predominant role in the photocatalytic reaction system. C₆₀ modified ZnAlTi-LDO catalysts for photocatalytic reduction shows great potential in degradation of organic pollutants and environmental remediation.

Effects of fullerene on lipid bilayers displaying different liquid ordering: a coarse-grained molecular dynamics study

BACKGROUND

The toxic effects and environmental impact of nanomaterials, and in particular of Fullerene particles, are matters of serious concern. It has been reported that fullerene molecules enter the cell membrane and occupy its hydrophobic region. Understanding the effects of carbon-based nanoparticles on biological membranes is therefore of critical importance to determine their exposure risks.

METHODS

We report on a systematic coarse-grained molecular dynamics study of the interaction of fullerene molecules with simple model cell membranes. We have analyzed bilayers consisting of lipid species with different degrees of unsaturation and a variety of cholesterol fractions. Addition of fullerene particles to phase-segregated ternary membranes is also investigated in the context of the lipid raft model for the organization of the cell membrane.

RESULTS

Fullerene addition to lipid membranes modifies their structural properties like thickness, area and internal ordering of the lipid species, as well as dynamical aspects such as molecular diffusion and cholesterol flip-flop. Interestingly, we show that phase-segregating ternary lipid membranes accumulate fullerene molecules preferentially in the liquid-disordered domains promoting phase-segregation and domain alignment across the membrane.

CONCLUSIONS

Lipid membrane internal ordering determines the behavior and distribution of fullerene particle, and this, in turn, determines the influence of fullerene on the membrane. Lipid membranes are good solvents of fullerene molecules, and in particular those with low internal ordering.

GENERAL SIGNIFICANCE

Preference of fullerene molecules to be dissolved in the more disordered hydrophobic regions of a lipid bilayer and the consequent alteration of its phase behavior may have important consequences on the activity of biological cell membranes and on the bioconcentration of fullerene in living organisms.

Electric-field-induced spin switch of endohedral dodecahedrane heterodimers H@C20Hn-C20Hn@M (M= Cu, Ag and Au, n = 15, 18, and 19): a theoretical study

We designed nine endohedral dodecahedrane heterodimers H@C₂₀H_n-C₂₀H_n@M (M = Cu, Ag, and Au, n = 15, 18, and 19) that may act as single-molecule spin switches, and we predicted theoretically that the ground states of the dimmers shift from low-spin states (S = 0) to the high-spin states (S = 1) under an external electric field applied parallel or perpendicular to the molecular symmetry axes, consisting well with the analyses of Stark effect. Molecular orbitals analyses provide an intuitive insight into the spin crossover behavior. This study expands the application of endohedral chemistry and provides new molecules for designing single-molecule spin switch.

Using Au@nano-C60 nanocomposite as an enhanced sensing platform in modeling a TNT aptasensor

Based on the unique characteristics of the combination of fullerene and gold nanoparticles, we successfully designed a new and facile nanocomposite (Au@nano-C60) to fabricate an aptasensor for the ultra-sensitive and selective detection of TNT. The gold nanoparticles decorated fullerene onto a glassy carbon electrode was prepared using an electrochemical method by the in situ generation of Au nanoparticles onto the surface of the glassy carbon electrode modified with activated fullerene. Successively, the NH₂-Apt as a receptor molecule of 2,4,6-Trinitrotoluen was covalently attached onto the modified electrode surface with the resultant nanocomposite. With the addition of the target onto the aptasensor surface and the formation of target/Apt complex, a linear response was obtained from 0.50 fM to 5 μM as well as a limit of detection down to 0.17 fM. The proposed aptasensor shows a wider linear response range and lower limit of detection for the specific detection of 2,4,6-Trinitrotoluen. This newly developed strategy will pave the way to partly meet the requirements in the field of homeland security and public safety.

TEMPO functionalized C60 fullerene deposited on gold surface for catalytic oxidation of selected alcohols

C₆₀TEMPO₁₀ catalytic system linked to a microspherical gold support through a covalent S-Au bond was developed. The C₆₀TEMPO₁₀@Au composite catalyst had a particle size of 0.5-0.8 μm and was covered with the fullerenes derivative of 2.3 nm diameter bearing ten nitroxyl groups; the organic film showed up to 50 nm thickness. The catalytic composite allowed for the oxidation under mild conditions of various primary and secondary alcohols to the corresponding aldehyde and ketone analogues with efficiencies as high as 79-98%, thus giving values typical for homogeneous catalysis, while retaining at the same time all the advantages of heterogeneous catalysis, e.g., easy separation by filtration from the reaction mixture. The catalytic activity of the resulting system was studied by means of high pressure liquid chromatography. A redox mechanism was proposed for the process. In the catalytic cycle of the oxidation process, the TEMPO moiety was continuously regenerated in situ with an applied primary oxidant, for example, O₂/Fe³⁺ system. The new intermediate composite components and the final catalyst were characterized by various spectroscopic methods and thermogravimetry. Graphical abstractᅟ.

The influence of cell and nanoparticle properties on heating and cell death in a radiofrequency field

The use of non-invasive radiofrequency (RF) energy to induce mild thermal and non-thermal effects in cancer tissue is under study as an adjuvant to chemo, radio or immuno therapy. This study examines cell specific sensitivities to RF exposure and the potential of nanoparticles to elevate heating rates or enhance biological effects. Increases in the heating rate of water in an RF field operating at 13.56MHz (0.004-0.028°C/s) were positively correlated with concentration of hybrid nanoparticles (1-10mg/ml) consisting of water soluble malonodiserinolamide [60]fullerene (C₆₀-ser) conjugated to the surface of mesoporous silica nanoparticles (SiO₂-C₆₀). The heating rate of highly conductive cell culture media (0.024°C/s) was similar to that of the highest concentration of nanoparticles in water, with no significant increase due to addition of nanoparticles at relevant doses (<100μg/ml). With respect to cell viability, anionic (SiO₂ and SiO₂-C₆₀) or neutral (C₆₀) nanoparticles did not influence RF-induced cell death, however, cationic nanoparticles (4-100μg/ml) caused dose-dependent increases in RF-induced cell death (24-42% compared to RF only). The effect of cell type, size and immortalization on sensitivity of cells to RF fields was examined in endothelial (HUVEC and HMVEC), fibroblast (primary dermal and L939) and cancer cells (HeLa and 4T1). While the state of cellular immortalization itself did not consistently influence the rate of RF-induced cell death compared to normal cell counter parts, cell size (ranging from 7 to 30μm) negatively correlated with cell sensitivity to RF (21-97% cell death following 6min irradiation). In summary, while nanoparticles do not alter the heating rate of biologically-relevant solutions, they can increase RF-induced cell death based on intrinsic cytotoxicity; and cells with smaller radii, and thereby greater surface membrane, are more susceptible to cell damage in an RF field than larger cells.

STATEMENT OF SIGNIFICANCE

The ability of nanoparticles to either direct heating or increase susceptibility of cancer cells to radiofrequency (RF) energy remains controversial, as is the impact of cell attributes on susceptibility of cells to RF-induced cell death. This manuscript examines the impact of nanoparticle charge, size, and cellular localization on RF-induced cell death and the influence of nanoparticles on the heating rates of water and biologically-relevant media. Susceptibility of immortalized or primary cells to RF energy and the impact of cell size are also examined. The ability to selectively modulate RF heating rates in specific biological locations or in specific cell populations would enhance the therapeutic potential of RF therapy.

Nanoparticle fullerol alleviates radiculopathy via NLRP3 inflammasome and neuropeptides

The present study aimed to evaluate the analgesic effect of the antioxidant nanoparticle fullerol in a mouse radiculopathy and a dorsal root ganglion (DRG) culture models. Intervertebral disk degeneration causes significant hyperalgesia and nerve inflammation. Pain sensitization and inflammatory reaction were counteracted by fullerol when disk material was bathed in 10 or 100μM of fullerol prior to implantation. Immunohistochemistry showed similar massive IBA1 positive macrophage infiltration surrounding implanted disk material among groups, but IL-1β and IL-6 expression was decreased in the fullerol treated group. In the DRG explant culture, after treatment with TNF-α, the expression of IL-1β, NLRP3, and caspase 1 was significantly increased but this was reversed by the addition of fullerol. In addition, fullerol also decreased the expression of substance P and CGRP in the cultured DRGs. Nanoparticle fullerol effectively counteracts pain sensitization and the inflammatory cascade caused by disk degeneration.

Photochemical reactivity of aqueous fullerene clusters: C60 versus C70

Over the past few years, there has been a strong interest in exploring the potential impact of fullerenes in the environment. Despite that both C₆₀ and C₇₀ have been detected in environmental matrices, the research on the impact of higher fullerenes, such as C_70, has been largely missing. This study evaluated and compared the phototransformation of aqueous C₆₀ and C₇₀ clusters (nC₆₀ and nC₇₀) and their ¹O₂ production under sunlight and lamp light irradiation (315nm, 360nm and 420nm). The nC₆₀ and nC₇₀ samples formed by direct mixing with water adopted a face-centered cubic (FCC) crystal structure. The apparent quantum yields (AQYs) of fullerene phototransformed were relatively constant over the examined wavelengths, while ¹O₂ production AQYs decreased with increased wavelengths. The long-term fate studies with outdoor sunlight indicated that both nC₆₀ and nC₇₀ lost considerable organic carbon contents (>80%) in water after ∼8 months of irradiation and that the intermediate photoproducts of nC₆₀ and nC₇₀ exhibited a progressively increased level of oxygen-containing functionalities. Overall, the study indicates that nC₇₀ can be photochemically removed under sunlight conditions and that the photoreactivity of nC₆₀ based on AQYs is greater than that of nC₇₀.

Noncovalent interaction assisted fullerene for the transportation of some brain anticancer drugs: A theoretical study

The treatment of brain cancer like glioblastoma multiforme often uses chemotherapeutic drugs like temozolomide, procarbazine, carmustine, and lomustine. Fullerene loaded with these drugs help to cross the blood brain barriers. The adsorptions of the four drug molecules on the surface of the fullerene are studied mostly by using density functional theory (DFT) based method at the M06-2X/6-31G(d) level of calculations. In all four cases, the estimated interactions are noncovalent type and the average adsorption energy lies in between -5 and -11kcal/mol in the gas phase. In the aqueous and protein environment such interactions are weakened further. The binding affinity is further assessed by performing MP2 based calculations to provide interaction energies with a reasonable accuracy. Stabilities and reactivities of the drug adsorbed fullerene complexes are determined from chemical reactivity descriptors. The attached drug molecules increase the polarity of the pristine C₆₀ thus facilitating the drug delivery within the biological systems. The semiconducting behavior of C₆₀ is retained in the C₆₀-drug composite systems. The computed DOS, IR, UV spectra, and molecular orbitals in the vicinity of Fermi level are analyzed to reveal the nature of the noncovalent interactions between C₆₀ and drug molecules. The Wiberg bond order values are used to estimate the strength of the adsorption of the drug molecule on C₆₀. In all four C₆₀-drug interactions, the chemical characteristics of the drug molecule are least perturbed by the C₆₀ moiety thereby suggesting it to be a good carrier for the delivery of these brain anticancer drug molecules to the target cells.

Spongy Nanostructures

Spongy structures are hollow-containing materials, encountered in natural or synthesized zeolites, spongy carbon, etc. The design and topological study of some hypothetical spongy nanostructures is presented in terms of map operations and genus calculation of their associated graphs, respectively. Among the discussed structures one remarks some novel spongy polyhedra that can evolve with 1-periodicity or radially, to provide multi-shell cages. Filling the space inside such complex nanostructures can be achieved by small fullerenes that self-arrange in aggregates with a well-defined geometry, of which energy trends to a minimal value. The way of space filling varies function of the dimension and shape of composing small fullerenes. An attempt of building and stability evaluating of several fullerene aggregates was made. The calculations were made at the HF, DFT and DFTB level of theory. The design of nanostructures was performed by our original software packages CVNET and Nano Studio.

Different effects of sonication pretreatment on carbon nanomaterials under low hydrogen peroxide concentrations

Dispersing carbon nanomaterials with the aid of sonication has become a widely used procedure for generating homogenous solutions. A systematic study was performed to evaluate the effects of a practical sample preparation procedure that involves mild sonication with/without low concentrations of hydrogen peroxide. Hydrogen peroxide is ubiquitously present in surface water and involved in advanced oxidation processes. Significant oxidation was observed for fullerene in the liquid phase, whereas an appreciable amount of hydrogen was covalently attached to the carbon cage of solid fullerene. Under the same conditions, only the removal of oxidized amorphous carbon was detected for carbon nanotubes. The presence of a low concentration of hydrogen peroxide during sonication exacerbated the effects. The changes in physicochemical properties were characterized quantitatively using X-ray photoelectron spectroscopy and elemental chemical analysis and qualitatively using matrix-assisted laser desorption ionization mass spectroscopy, ¹H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Our results highlight the effects that can occur during sample preparation step and the potential for misinterpreting the toxicity, reactivity and environmental fate of carbon nanomaterials.

Colloidal aggregation and structural assembly of aspect ratio variant goethite (α-FeOOH) with nC60 fullerene in environmental media

Environmental mobility of C₆₀ fullerene can be significantly affected in the presence of naturally abundant α-FeOOH. However, α-FeOOH vary significantly in sizes, shapes and associated properties that can greatly influence the fate and transport of C₆₀ fullerene in environmental media. Therefore, colloidal hetero-association between well crystallized low aspect (L_Asp) α-FeOOH and nC₆₀ fullerene may differ substantially to weakly crystallized high-aspect (H_Asp) counterpart. In contrast to L_Asp α-FeOOH, inherent crystal defects and surface charge generation in H_Asp α-FeOOH facilitated strong Coulombic attraction and aggregation with fullerene in acidic pH. However, L_Asp α-FeOOH demonstrated subtle entropic depletion mediated interaction with fullerene prevalent in hard rods. Humic acid (HA) encapsulation of H_Asp α-FeOOH substantially blocked fullerene attachment. Minute enhancement in colloidal stability was detected for HA-coated H_Asp α-FeOOH and fullerene mixture to HA-coated H_Asp α-FeOOH alone. To investigate the interfacial assembly of α-FeOOH with fullerene "in situ" differential interference contrast (DIC) microscopic investigations were employed. This study showed significantly different interface behavior of the binary mixtures of fullerene and H_Asp α-FeOOH NPs, and L_Asp particles. On air-water interface, bare H_Asp α-FeOOH displayed liquid crystalline packing. However, addition of fullerene to H_Asp α-FeOOH suspension at pH5 produced closed-loop polygonal and circular ring structures. Head-to-tail alignment of magnetic dipoles as well as fullerene hydrophobicity facilitated such assembly formation. "Ex situ" AFM investigation revealed further the presence of magnetically derived ring structure which asserts that the formed "in situ" ensembles were not transient, hence, may abate fullerene transport through environmental interfaces. Barring hydrophobicity assisted attachment of fullerene to L_Asp α-FeOOHs, the absence of any close-packed structures may unlikely abate fullerene transport as envisaged in case of H_Asp α-FeOOH. Thus, aspect ratio variation and associated material properties of naturally abundant α-FeOOH may significantly impact fullerene transport through environmental media.

Potential Suppressive Effects of Two C60 Fullerene Derivatives on Acquired Immunity

The therapeutic effects of fullerene derivatives on many models of inflammatory disease have been demonstrated. The anti-inflammatory mechanisms of these nanoparticles remain to be elucidated, though their beneficial roles in allergy and autoimmune diseases suggest their suppressive potential in acquired immunity. Here, we evaluated the effects of C₆₀ pyrrolidine tris-acid (C₆₀-P) and polyhydroxylated fullerene (C₆₀(OH)₃₆) on the acquired immune response in vitro and in vivo. In vitro, both C₆₀ derivatives had dose-dependent suppressive effects on T cell receptor-mediated activation of T cells and antibody production by B cells under anti-CD40/IL-4 stimulation, similar to the actions of the antioxidant N-acetylcysteine. In addition, C₆₀-P suppressed ovalbumin-specific antibody production and ovalbumin-specific T cell responses in vivo, although T cell-independent antibodies responses were not affected by C₆₀-P. Together, our data suggest that fullerene derivatives can suppress acquired immune responses that require T cells.

A bis-malonic acid fullerene derivative significantly suppressed IL-33-induced IL-6 expression by inhibiting NF-κB activation

IL-33 functions as a ligand for ST2L, which is mainly expressed in immune cells, including mast cells. IL-33 is a potent inducer of pro-inflammatory cytokines, such as IL-6, and has been implicated in the pathogenesis of allergic inflammatory diseases. Therefore, IL-33 has recently been attracting attention as a new target for the treatment of inflammatory diseases. In the present study, we demonstrated that a water-soluble bis-malonic acid fullerene derivative (C₆₀-dicyclopropane-1,1,1',1'-tetracarboxylic acid) markedly diminished the IL-33-induced expression of IL-6 in bone marrow-derived mast cells (BMMC). The bis-malonic acid fullerene derivative suppressed the canonical signaling steps required for NF-κB activation such as the degradation of IκBα and nuclear translocation of NF-κB by directly inhibiting the IL-33-induced IKK activation. Although p38 and JNK also contributed to IL-33-induced expression of IL-6, the bis-malonic acid fullerene derivative did not affect their activation. Furthermore, the bis-malonic acid fullerene derivative had no effect on the NF-κB activation pathway induced by TNFα and IL-1. These results suggest that the bis-malonic fullerene derivative has potential as a specific drug for the treatment of IL-33-induced inflammatory diseases by specifically inhibiting the NF-κB activation pathway.

Application of DNA aptamers as sensing layers for detection of carbofuran by electrogenerated chemiluminescence energy transfer

In this study, an electrogenerated chemiluminescence (ECL) sensing platform for carbofuran detection was constructed based on ECL energy transfer (ECRET) and carbon dot (C-dot)-tagged aptamers as the recognition element. Fullerene (C60)-loaded gold nanoparticles (C60-Au) were used as the energy donor, modified on a glassy carbon electrode. C-dot-tagged DNA aptamers were used as the receptor, and ECRET then occurred between C60-Au and C-dots. After accepting the energy, the C-dots acted as a signal indicator and showed decreased signal intensity in the presence of targets, which competitively bound to DNA aptamers and blocked energy transfer. Using this robust, straight-forward strategy, the sensor showed a linear ECL response to carbofuran at concentrations from 2.0 × 10^-11 mol L^-1 to 8.0 × 10^-9 mol L^-1. The detection limit of this assay was shown to be 8.8 × 10^-13 mol L^-1. Thus, the sensing approach described in this study could be adapted for use in the detection of various pesticide residue targets.

Novel fullerene derivatives as dual inhibitors of Hepatitis C virus NS5B polymerase and NS3/4A protease

We evaluated the Hepatitis C virus (HCV) NS5B polymerase and HCV NS3/4A protease inhibition activities of a new set of proline-type fullerene derivatives. All of the compounds had the potential to inhibit both the enzymes, indicating that the fullerene derivatives may be dual inhibitors against NS5B and NS3/4A and could be novel lead compounds for the treatment of HCV infections.

Protective effects of polyvinylpyrrolidone-wrapped fullerene against intermittent ultraviolet-A irradiation-induced cell injury in HaCaT cells

To identify compounds that suppress UV irradiation-induced oxidative stress in the skin, various types of antioxidants have been studied. Polyvinylpyrrolidone-entrapped fullerene (C60/PVP) is known as a powerful antioxidant that exerts a cytoprotective effect against UV irradiation-induced cell injury in human skin cells and skin models. However, the effects of the alternate attractive C60/PVP feature, persistent antioxidant ability, on cytoprotection have rarely been ascertained. In this study we therefore investigated the efficacies of C60/PVP using an intermittently repeated UVA irradiation model wherein human keratinocytes were repeatedly exposed to UVA five times every 1h and compared the cytoprotective effects with those provided by ascorbic acid-2-O-phosphate-disodium salt (APS) and α-tocopherol (α-Toc). Our results demonstrated that C60/PVP yielded prominent cytoprotective effects against intermittently repeated UVA irradiation-induced injuries in a dose-dependent manner and suppressed intracellular superoxide anion radical (O2(-)) generation both during and after the repeated UVA irradiation. Additionally, C60/PVP also repressed the intermittent UVA irradiation-induced apoptosis via suppression of chromatin condensation and caspase-3/7 activation. Furthermore, the observed cytoprotective effects were superior to the effects of the typical antioxidants APS and α-Toc. These data suggest that C60/PVP might function as a potent cosmetic antioxidant against the effects of repeated and prolonged UVA irradiation through its persistent antioxidative property.

Effect of fullerene on the dispersibility of nanostructured lipid particles and encapsulation in sterically stabilized emulsions

We report on the effect of fullerenes (C60) on the stability of nanostructured lipid emulsions. These (oil-in-water) emulsions are essentially aqueous dispersions of lipid particles exhibiting self-assembled nanostructures at their cores. The majority of previous studies on fullerenes were focused on planar and spherical lipid bilayer systems including pure lipids and liposomes. In this work, fullerenes were interacted with a lipid that forms nanostructured dispersions of non-lamellar self-assemblies. A range of parameters including the composition of emulsions and sonication parameters were examined to determine the influence of fullerenes on in-situ and pre-stabilized lipid emulsions. We found that fullerenes mutually stabilize very low concentrations of lipid molecules, while other concentration emulsions struggle to stay stable or even to form at first instance; we provide hypotheses to support these observations. Interestingly though, we were able to encapsulate varying amounts of fullerenes in sterically stabilized emulsions. This step has a significant positive impact, as we could effectively control an inherent aggregation tendency of fullerenes in aqueous environments. These novel hybrid nanomaterials may open a range of avenues for biotechnological and biomedical applications exploiting properties of both lipid and fullerene nanostructures.

Fullerene/photosensitizer nanovesicles as highly efficient and clearable phototheranostics with enhanced tumor accumulation for cancer therapy

A novel phototheranostic platform based on tri-malonate derivative of fullerene C70 (TFC70)/photosensitizer (Chlorin e6, Ce6) nanovesicles (FCNVs) has been developed for effective tumor imaging and treatment. The FCNVs were prepared from amphiphilic TFC70-oligo ethylene glycol -Ce6 molecules. The developed FCNVs possessed the following advantages: (i) high loading efficiency of Ce6 (up to ∼57 wt%); (ii) efficient absorption in near-infrared light region; (iii) enhanced cellular uptake efficiency of Ce6 in vitro and in vivo; (iv) good biocompatibility and total clearance out from the body. These unique properties suggest that the as-prepared FCNVs could be applied as an ideal theranostic agent for simultaneous imaging and photodynamic therapy of tumor. This finding may provide a good solution to highly efficient phototheranostic applications based on fullerene derivatives fabricated nanostructures.

Fullerenes and their derivatives as inhibitors of tumor necrosis factor-α with highly promoted affinities

Tumor necrosis factor-α (TNF-α) is a cell signalling protein involved in systemic inflammation in infectious and other malignant diseases. Physiologically, it plays an important role in regulating host defence, but its overexpression can lead to serious illnesses including cancer, autoimmune disease and inflammatory disease. Gadolinium-based metallofullerenols, e.g., Gd@C82(OH) x (x ≈ 22), are well known for their abundant biological activities with low toxicity experimentally and theoretically; however, their activity in direct TNF-α inhibition has not been explored. In this work, we investigated the inhibiting effects of four types of fullerene-based ligands: fullerenes, fullerenols, metallofullerenes, and metallofullerenols. We reported previously that fullerenes, metallofullerenes and their hydroxylated derivatives (fullerenols) can reside in the same pocket of the TNF-α dimer as that of SPD304-a known inhibitor of TNF-α [He et al. (2005) Science 310:1022, 18]. Ligand docking and binding free energy calculations suggest that, with a similar nonpolar interaction dominated binding pattern, the fullerene-based ligands, C60, C60(OH)12, Gd@C60, C82, C82(OH)12, Gd@C82, Gd@C82(OH)13 and Gd@C82(OH)21, have larger affinity than currently known inhibitors, and could be used to design novel inhibitors of TNF-α in the future. Graphical Abstract Fullerene-material/TNF-α.

Effect of subcellular distribution on nC₆₀ uptake and transfer efficiency from Scenedesmus obliquus to Daphnia magna

The potential uptake and trophic transfer ability of nanoparticles (NPs) in aquatic organisms have not been well understood yet. There has been an increasing awareness of the subcellular fate of NPs in organisms, but how the subcellular distribution of NPs subsequently affects the trophic transfer to predator remains to be answered. In the present study, the food chain from Scenedesmus obliquus to Daphnia magna was established to simulate the trophic transfer of fullerene aqueous suspension (nC60). The nC60 contaminated algae were separated into three fractions: cell wall (CW), cell organelle (CO), and cell membrane (CM) fractions, and we investigated the nC60 uptake amounts and trophic transfer efficiency to the predator through dietary exposure to algae or algal subcellular fractions. The nC60 distribution in CW fraction of S. obliquus was the highest, following by CO and CM fractions. nC60 uptake amounts in D. magna were found to be mainly relative to the NPs' distribution in CW fraction and daphnia uptake ability from CW fraction, whereas the nC60 trophic transfer efficiency (TE) were mainly in accordance with the transfer ability of NPs from the CO fraction. CW fed group possessed the highest uptake amount, followed by CO and CM fed groups, but the presence of humic acid (HA) significantly decreased the nC60 uptake from CW fed group. The CO fed groups acquired high TE values for nC60, while CM fed groups had low TE values. Moreover, even though CW fed group had a high TE value; it decreased significantly with the presence of HA. This study contributes to the understanding of fullerene NPs' dietary exposure to aquatic organisms, suggesting that NPs in different food forms are not necessarily equally trophically available to the predator.

Toxic and DNA damaging effects of a functionalized fullerene in human embryonic lung fibroblasts

Water-soluble fullerenes have been studied as potential nanovectors and therapeutic agents, but their possible toxicity is of concern. We have studied the effects of F-828, a soluble fullerene [C60] derivative, on diploid human embryonic lung fibroblasts (HELFs) in vitro. F-828 causes complex time-dependent changes in ROS levels. Inhibition of Nox4 activity by plumbagin blocks F-828-dependent ROS elevation. F-828 induces DNA breaks, as measured by the comet assay and γH2AX expression, and the activities of the transcription factors NF-kB and p53 increase. F-828 concentrations>25μM are cytotoxic; cell death occurs by necrosis. Expression levels of TGF-β, RHOA, RHOC, ROCK1, and SMAD2 increase following exposure to F-828. Our results raise the possibility that fullerene F-828 may induce pulmonary fibrosis in vivo.

Fullerene inhibits benzo(a)pyrene Efflux from Cyprinus carpio hepatocytes by affecting cell membrane fluidity and P-glycoprotein expression

P-Glycoprotein (P-gp) can protect cells by pumping out toxic compounds, and has been found widely expressed in fish tissues. Here, we illustrate the P-gp efflux ability for benzo(a)pyrene (BaP) in the hepatocytes of common carp (Cyprinus carpio) after exposing to fullerene aqueous suspension (nC60). The results revealed that nC60 increased the membrane fluidity by decreasing the ratio of saturated to unsaturated fatty acids, and increased the cholesterol contents. These findings, combined with 10-38% and 70-75% down-regulation of P-gp mRNA and protein respectively, suggested that nC60 caused inhibition on P-gp efflux transport system. Therefore, we further investigated the cellular efflux ability for BaP. Results showed unequivocally that nC60 is a potent P-gp inhibitor. The retaining BaP amounts after efflux were elevated by 1.7-2.8 fold during the 10 day exposure. Meanwhile, 5mg/L humic acid (one of the important fractions of natural organic matter, which is ubiquitous in aquatic environment) alleviated the nC60 damage to hepatocytes in terms of oxidative damage, cholesterol increment, and P-gp content reduction; and finally attenuated the suppressed P-gp efflux ability. Collectively, this study provides the first evidence of nC60 toxicity to P-gp functionality in fish and illustrates the possible mechanism of the suppressed P-gp efflux ability for BaP.

Target Plate Material Influence on Fullerene-C60 Laser Desorption/Ionization Efficiency

Systematic laser desorption/ionization (LDI) experiments of fullerene-C60 on a wide range of target plate materials were conducted to gain insight into the initial ion formation in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The positive and negative ion signal intensities of precursor, fragment, and cluster ions were monitored, varying both the laser fluence (0-3.53 Jcm(-2)) and the ion extraction delay time (0-950 ns). The resulting species-specific ion signal intensities are an indication for the ionization mechanisms that contribute to LDI and the time frames in which they operate, providing insight in the (MA)LDI primary ionization. An increasing electrical resistivity of the target plate material increases the fullerene-C60 precursor and fragment anion signal intensity. Inconel 625 and Ti90/Al6/V4, both highly electrically resistive, provide the highest anion signal intensities, exceeding the cation signal intensity by a factor ~1.4 for the latter. We present a mechanism based on transient electrical field strength reduction to explain this trend. Fullerene-C60 cluster anion formation is negligible, which could be due to the high extraction potential. Cluster cations, however, are readily formed, although for high laser fluences, the preferred channel is formation of precursor and fragment cations. Ion signal intensity depends greatly on the choice of substrate material, and careful substrate selection could, therefore, allow for more sensitive (MA)LDI measurements. Graphical Abstract ᅟ.

Aqueous stability and mobility of C₆₀ complexed by sodium dodecyl benzene sulfonate surfactant

Surfactant complexation may have significant effects on the environmental behavior of nano-particles. In order to understand the ecological exposure of nano-materials, it is important to determine the stability and mobility of surfactant-complexed nano-materials in aqueous systems. In this study, the aggregation and transport of C60 complexed by the surfactant sodium dodecyl benzene sulfonate (SDBS) were investigated. It was found that SDBS-complexed C60 had a ζ-potential of -49.5 mV under near-neutral pH conditions and remained stable during an aging period of 15 days. It had a critical coagulation concentration of 550 mmol/L for NaCl, which was higher than common natural colloids and many kinds of raw nano-materials, and was comparable to those of many kinds of surface-modified nano-materials. SDBS enhanced the stability of C60 colloid; however, at the same time, it also enhanced the colloidal particle aggregation rate. Much higher mobility was found for SDBS-complexed C60 than C60 colloid. Increase in ionic strength, Ca(2+) concentration or Al(3+) concentration decreased the mobility. In general, SDBS-complexed C60 had high stability and mobility.

Removal of aqueous nC60 fullerene from water by low pressure membrane filtration

The potential environmental and health risks of engineered nanoparticles such as buckminsterfullerene C60 in water require their removal during the production of drinking water. We present a study focusing on (i) the removal mechanism and (ii) the elucidation of the role of the membrane pore size during removal of nC60 fullerene nanoparticle suspensions in dead-end microfiltration and ultrafiltration mimicking separation in real industrial water treatment plants. Membranes were selected with pore sizes ranging from 18 nm to 500 nm to determine the significance of the nC60 to membrane pore size ratio and the adsorption affinity between nC60 and membrane material during filtration. Experiments were carried out with a dead-end bench-scale system operated at constant flux conditions including a hydraulic backwash cleaning procedure. nC60 nanoparticles can be efficiently removed by low pressure membrane technology with smaller and, unexpectedly, also by mostly similar or larger pores than the particle size, although the nC60 filtration behaviour appeared to be different. The nC60 size to membrane pore size ratio and the ratio of the cake-layer deposition resistance to the clean membrane resistance, both play an important role on the nC60 filtration behaviour and on the efficiency of the backwash procedure recovering the initial membrane filtration conditions. These results become specifically significant in the context of drinking water production, for which they provide relevant information for an accurate selection between membrane processes and operational parameters for the removal of nC60 in the drinking water treatment.

Fullerenol C60(OH)24 increases ion permeability of lipid membranes in a pH-dependent manner

Fullerenols are water-soluble analogs of fullerene exhibiting both antioxidant and prooxidant activities in vitro and in vivo. Here we report, for the first time, that fullerenol C60(OH)24 can induce ion permeability of a planar lipid bilayer membrane via the formation of ion pores or conductive defects with a preference for cations over anions. The fullerenol-mediated electrical current displayed non-linear concentration dependence and was reversibly enhanced by alkalinization. Calcium and magnesium ions decreased the fullerenol-induced potassium ion permeability. Voltage dependence of the current was sensitive to membrane composition, with the conductance being well pronounced in fully saturated diphytanoylphosphatidylcholine. Fullerenol did not induce carboxyfluorescein leakage from liposomes, suggesting a small size of fullerenol-induced pores. In contrast to ion permeability, the binding of C60(OH)24 to liposomes increased at acidic pH, as measured by fluorescence quenching of pyrene-labeled lipid. In line with this, the photodynamic action of fullerenol on the peptide gramicidin A also increased at low pH. It is hypothesized that aggregates of fullerenol may stabilize transient conductive lipid defects or pores formed under a variety of stress conditions.

The sphere-in-contact model of carbon materials

A sphere-in-contact model is presented that is used to build physical models of carbon materials such as graphite, graphene, carbon nanotubes and fullerene. Unlike other molecular models, these models have correct scale and proportions because the carbon atoms are represented by their atomic radius, in contrast to the more commonly used space-fill models, where carbon atoms are represented by their van der Waals radii. Based on a survey taken among 65 undergraduate chemistry students and 28 PhD/postdoctoral students with a background in molecular modeling, we found misconceptions arising from incorrect visualization of the size and location of the electron density located in carbon materials. Based on analysis of the survey and on a conceptual basis we show that the sphere-in-contact model provides an improved molecular representation of the electron density of carbon materials compared to other molecular models commonly used in science textbooks (i.e., wire-frame, ball-and-stick, space-fill). We therefore suggest that its use in chemistry textbooks along with the ball-and-stick model would significantly enhance the visualization of molecular structures according to their electron density.

Graphical Abstract

Object-oriented Persistent Homology

Persistent homology provides a new approach for the topological simplification of big data via measuring the life time of intrinsic topological features in a filtration process and has found its success in scientific and engineering applications. However, such a success is essentially limited to qualitative data classification and analysis. Indeed, persistent homology has rarely been employed for quantitative modeling and prediction. Additionally, the present persistent homology is a passive tool, rather than a proactive technique, for classification and analysis. In this work, we outline a general protocol to construct object-oriented persistent homology methods. By means of differential geometry theory of surfaces, we construct an objective functional, namely, a surface free energy defined on the data of interest. The minimization of the objective functional leads to a Laplace-Beltrami operator which generates a multiscale representation of the initial data and offers an objective oriented filtration process. The resulting differential geometry based object-oriented persistent homology is able to preserve desirable geometric features in the evolutionary filtration and enhances the corresponding topological persistence. The cubical complex based homology algorithm is employed in the present work to be compatible with the Cartesian representation of the Laplace-Beltrami flow. The proposed Laplace-Beltrami flow based persistent homology method is extensively validated. The consistence between Laplace-Beltrami flow based filtration and Euclidean distance based filtration is confirmed on the Vietoris-Rips complex for a large amount of numerical tests. The convergence and reliability of the present Laplace-Beltrami flow based cubical complex filtration approach are analyzed over various spatial and temporal mesh sizes. The Laplace-Beltrami flow based persistent homology approach is utilized to study the intrinsic topology of proteins and fullerene molecules. Based on a quantitative model which correlates the topological persistence of fullerene central cavity with the total curvature energy of the fullerene structure, the proposed method is used for the prediction of fullerene isomer stability. The efficiency and robustness of the present method are verified by more than 500 fullerene molecules. It is shown that the proposed persistent homology based quantitative model offers good predictions of total curvature energies for ten types of fullerene isomers. The present work offers the first example to design object-oriented persistent homology to enhance or preserve desirable features in the original data during the filtration process and then automatically detect or extract the corresponding topological traits from the data.

A proline-type fullerene derivative inhibits adipogenesis by preventing PPARγ activation

Obesity and its associated metabolic diseases represent some of the most rapidly expanding health issues worldwide, and, thus, the development of a novel chemical compound to suppress adipogenesis is strongly expected. We herein investigated the effects of water-soluble fullerene derivatives: a bis-malonic acid derivative and three types of proline-type fullerene derivatives, on adipogenesis using NIH-3T3 cells overexpressing PPARγ. One of the proline-type fullerene derivatives (P3) harboring three carboxy groups significantly inhibited lipid accumulation and the expression of adipocyte-specific genes, such as aP2, induced by the PPARγ agonist rosiglitazone. On the other hand, the bis-malonic acid derivative (M) and the 2 other proline-type fullerene derivatives (P1, P2), which have two carboxy groups, had no effect on PPARγ-mediated lipid accumulation or the expression of aP2. P3 fullerene also inhibited lipid accumulation induced by the combined stimulation with 3-isobutyl-1-methylxanthine (IBMX), dexamethasone, and insulin in 3T3-L1 preadipocytes. During the differentiation of 3T3-L1 cells into adipocytes, P3 fullerene did not affect the expression of C/EBPδ, C/EBPβ, or PPARγ, but markedly inhibited that of aP2 mRNA. These results suggest that P3 fullerene exhibits anti-obesity activity by preventing the activation of PPARγ.

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Fullerene derivative inhibits the rosiglitazone-induced adipogenesis.

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Fullerene derivative inhibits the rosiglitazone-induced expression of aP2 mRNA.

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Fullerene derivative inhibits adipogenesis of 3T3-L1 preadipocyte.

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Fullerene derivative inhibits the activation of PPARγ in 3T3-L1 preadipocyte.

Density functional theory (DFT) investigations on doped fullerene with heteroatom substitution

Structures and stabilities of dodecahedral fullerene C19X (X=Ni, Ti) and C20 have been investigated by quantum chemical calculations based on density functional theory. The geometrical structures, relative stabilities, dielectric constant of the doped cages were studied systematically and compared with those of the fullerene C20 cage. A series of dodecahedral functionalized derivatives have been studied at the B3LYP/6-31G level of density functional theory (DFT). The relative and formation energies of compounds, Mulliken charges, occupancy, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), the HOMO-LUMO band gap and chemical potential (μ) were calculated. The doping effect is discussed in terms of the change in the CC bond length and total dipole moment. The obtained result indicates that the CC bond length increases as a result of doping. The NBO analysis showed that there is a hyper conjugative interaction between the hetero atoms such as titanium and nickel lone-pair electron of doped fullerene with bonding and antibonding (σ(∗)) orbital of carbon atom of fullerene. The stability of the molecule, arising from charge delocalization, has been analyzed using Natural Bond Orbital (NBO) analysis. The nucleus - independent that more negative NICS values in doped fullerene than those of C20. The condensed Fukui Function and the newly introduced the atomic descriptors S (fk) to determine the local reactive sites of the molecular systems during electrophilic, nucleophilic and radical attacks have been calculated for the fullerene C20 compound.

The role of attached phase soil and sediment organic matter physicochemical properties on fullerene (nC60) attachment

Attached phase soil and sediment organic matter is ubiquitous in the subsurface environment, with a tendency to strongly sorb contaminants, and therefore it may play an important role in contaminant transport. In this study, the deposition of C60 nanoparticles onto attached phase Harpeth Humic Acid and Harpeth Fulvic Acid (HHA and HFA) is explored by using a quartz crystal microbalance with dissipation monitoring and systematically varying thermal energy. By comparing the C60 attachment onto HHA and HFA surfaces to that of bare silica and DLVO predictions, we find that the HHA and HFA layers hinder attachment at low temperatures, while HHA enhances attachment at higher temperatures. Based on thermal characterization of the HHA and HFA layers compared to the corresponding attachment trends, the attachment efficiency is strongly correlated with hydration of the layer. Possible mechanisms explaining this phenomenon include water-assisted disruption of polar SOM contacts and hydration-induced swelling of the AP-SOM matrix. Since humic substances typically dominate subsurface organic matter, these results may prove crucial to understanding the complex interactions of engineered nanomaterials in both the natural and engineered environment.

Trapping N5 rings and N3 chains on the outer surface of fullerene C60: a theoretical study

The capture of N3-chains and N5-rings on the outer surface of C60 was studied using density functional calculations. For the neutral N5-ring, it was found that a N5-ring trapped by a C60 cage becomes more stable than an isolated N5-ring radical, and a C60-N5 compound with a C-N bond at an exohedral position of C60 is more stable than an isomer with the N5-ring encapsulated in C60. Such stability arises from the reduction in molecular strain energy, and charge transfer from C60 to N5. Dynamics calculations indicate that capture of the N5-ring on the outer surface of C60 is a barrierless process. Furthermore, the trapping sites of more N5-rings on the C60 were determined using condensed Fukui functions, where the N5-rings prefer to be trapped on the surface to form addition products across 6,6-junctions. Based on the optimized geometries of C60-(N5) n (n = 2, 6, 10), their chemical stabilities were found to be comparable with that of C60 in terms of the gap between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals. Similar phenomena were found for an N3-chain wrapped on the surface of C60. However, the results of the average adsorption energies show that C60 can capture N5-rings more effectively than N3-chains.

Hybrids of cationic porphyrins with nanocarbons

In the review hybrids of cationic porphyrins (i.e. porphyrins functionalized by quaternary pyridinium groups) with nanocarbons such as fullerenes, carbon nanotubes and graphene are described. Selected examples of these species are characterized in regard of their properties and possible applications.

Antimicrobial activity of carbon-based nanoparticles

Due to the vast and inappropriate use of the antibiotics, microorganisms have begun to develop resistance to the commonly used antimicrobial agents. So therefore, development of the new and effective antimicrobial agents seems to be necessary. According to some recent reports, carbon-based nanomaterials such as fullerenes, carbon nanotubes (CNTs) (especially single-walled carbon nanotubes (SWCNTs)) and graphene oxide (GO) nanoparticles show potent antimicrobial properties. In present review, we have briefly summarized the antimicrobial activity of carbon-based nanoparticles together with their mechanism of action. Reviewed literature show that the size of carbon nanoparticles plays an important role in the inactivation of the microorganisms. As major mechanism, direct contact of microorganisms with carbon nanostructures seriously affects their cellular membrane integrity, metabolic processes and morphology. The antimicrobial activity of carbon-based nanostructures may interestingly be investigated in the near future owing to their high surface/volume ratio, large inner volume and other unique chemical and physical properties. In addition, application of functionalized carbon nanomaterials as carriers for the ordinary antibiotics possibly will decrease the associated resistance, enhance their bioavailability and provide their targeted delivery.

Effects of aqueous stable fullerene nanocrystal (nC60) on Scenedesmus obliquus: evaluation of the sub-lethal photosynthetic responses and inhibition mechanism

Understanding sub-lethal effects of nanomaterial 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 of water stable, nanocrystalline fullerenes as C60 (termed nC60) were studied on Scenedesmusobliquus, a globally distributed phytoplankton. Sub-lethal concentration for S. obliquus was firstly determined as 0.09mgL(-1) using the standard 72h exposure tests (OECD Guideline 201). Subsequent sub-lethal experiment of nC60 on the S. obliquus was carried out for 60d and focused on the photosynthesis processes. The results demonstrate that upon sub-lethal exposure, the photosynthetic products of polysaccharide, soluble protein and total lipid were decreased with exposure time. The photosynthetic pigments of chlorophyll a and chlorophyll b were negatively impacted. Further investigations indicate that the decrements in photosynthetic products and pigments were mainly due to the algal Mg(2+) decrement (by 40%) at the sub-lethal concentration (0.09mgL(-1)) of nC60. The decrement in Mg(2+) of S. obliquus was due to the inhibition of Mg(2+)-ATPase activity caused by nC60. Sum up, these results not only describe the sub-lethal effects but also provide the probably mechanism for sub-lethal effects of nC60 on exposed S. obliquus.

An efficient comparison of methods involving conventional, grinding and ultrasound conditions for the synthesis of fulleroisoxazolines

In this research, an efficient comparison between conventional, grinding and sonication methods for the synthesis of fulleroisoxazolines was investigated. Compared to the conventional methods, ultrasound procedure showed several advantages including mild reaction conditions, high yields, short reaction times and environmental friendliness.

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.

The influence of distribution of hydroxyl groups on vibrational spectra of fullerenol C60(OH)24 isomers: DFT study

The infrared and Raman spectra of C60(OH)24 molecule with uniform and non-uniform distribution of hydroxyl groups have been investigated using first principle DFT calculations at the B3LYP/6-31G(d,p) level of theory. The important features of the obtained geometries have been measured and compared to experimental results. The reference calculations of C60 molecule geometry and vibrational spectra have been made and compared to available experimental data. The striking differences of infrared spectra between C60(OH)24 molecule with uniform and non-uniform distribution of hydroxyl groups have been shown and discussed. The OH modes have been identified as the most sensitive to C60(OH)24 isomer configuration. The C-C stretching modes in the Raman spectra of the C60(OH)24 molecule have been found as a potential sensor of OH groups distribution over fullerene C60 surface.

Characterizing reactive oxygen generation and bacterial inactivation by a zerovalent iron-fullerene nano-composite device at neutral pH under UV-A illumination

A nano-composite device composed of nano-scale zerovalent iron (ZVI) and C60 fullerene aggregates (ZVI/nC60) was produced via a rapid nucleation method. The device was conceived to deliver reactive oxygen species (ROS) generated by photosensitization and/or electron transfer to targeted contaminants, including waterborne pathogens under neutral pH conditions. Certain variations of the nano-composite were fabricated differing in the amounts of (1) ZVI (0.1mM and 2mM) but not nC60 (2.5mg-C/L), and (2) nC60 (0-25mg-C/L) but not ZVI (0.1mM). The generation of ROS by the ZVI/nC60 nano-composites and ZVI nanoparticles was quantified using organic probe compounds. 0.1mM ZVI/2.5mg-C/L C60 generated 3.74-fold higher O2(-) concentration and also resulted in an additional 2-log inactivation of Pseudomonas aeruginosa when compared to 0.1mM ZVI (3-log inactivation). 2mM ZVI/2.5mg-C/L nC60 showed negligible improvement over 2mM ZVI in terms of O2(-) generation or inactivation. Further, incremental amounts of nC60 in the range of 0-25mg-C/L in 0.1mM ZVI/nC60 led to increased O2(-) concentration, independent of UV-A. This study demonstrates that ZVI/nC60 device delivers (1) enhanced O2(-) with nC60 as a mediator for electron transfer, and (2) (1)O2 (only under UV-A illumination) at neutral pH conditions.

Toxicity of fullerene and nanosilver nanomaterials against bacteria associated to the body surface of the estuarine worm Laeonereis acuta (Polychaeta, Nereididae)

This study analyzed the growth and biochemical responses of six bacterial colonies isolated from the mucus of the estuarine polychaeta Laeonereis acuta (Nereididae) after exposure to a water suspension of fullerene (nC60) and nanosilver (nAg) separately (0.01; 0.10; and 1.00 mg/L) and together (0.01; 0.10; and 1.00 mg/L of nanosilver and 1.00 mg/L of fullerene added to each nAg concentration). Exposures were performed in darkness during 24 h and then samples were taken from the worms and inoculated on agar during 24 h to analyze colonies growth. After this the material was analyzed biochemically. Colonies growth (tested by wet biomass weight) was inhibited at 0.01 and 0.10 mg/L of nAg and 0.01 and 0.10 mg/L nAg + constant 1.00 mg/L of nC60 (p < 0.05). Lipid peroxidation damage was significant from the control for the concentrations of 0.01 and 0.10 mg/L of nC60 and glutathione-S-transferase (GST) activity was significantly higher for the concentration of 1.00 mg/L mg/L nAg + constant 1.00 mg/L of nC60 (p < 0.05). Although nC60 did not induced growth inhibition, it triggered lipid peroxidation alone and increased GST activity together with nAg.60 Contrary to nC60, nanosilver inhibited bacterial growth, although the biochemical measurements indicate that this response is not due to reactive oxygen species generation.

Theoretical investigations on C60 -ionic liquid interactions and their impacts on C60 dispersion behavior

Increased use and production of carbon nanomaterials (e.g., fullerene C60 ) and ionic liquids (ILs) may result in their concomitant releases into the environment. Inevitably there will be interactions between carbon nanoparticles (CNPs) and ILs. However, experimental data on the interaction of CNPs with ILs are not readily available, and the mechanism behind the interactions is still elusive. To contribute to an understanding of the molecular interactions established between CNPs and ILs, theoretical investigations at multiple levels were performed to determine the interactions of C60 with 6 different imidazolium-based ILs. The results indicate that C60 mainly interacts with the IL molecules through the van der Waals, π-cation, and hydrophobic interactions. Mulliken population analysis suggests that charge transfer occurs from the IL to C60 during the C60 -IL interaction. The self-diffusion coefficient (D) of C60 in [C60  + IL] systems reaches the maximum in the case of moderate C60 -IL interaction (interaction energy, EINT ), implying that in this case a good dispersion of an agglomerate species of C60 is obtained. The D value of C60 in [C60  + IL +water] systems increases with an increase of the EINT , implying that the presence of ILs can play an important role in the aqueous dispersion of the C60 agglomerate.

A tumoral acidic pH-responsive drug delivery system based on a novel photosensitizer (fullerene) for in vitro and in vivo chemo-photodynamic therapy

Fullerene has shown great potential both in drug delivery and photodynamic therapy. Herein, we developed a doxorubicin (DOX)-loaded poly(ethyleneimine) (PEI) derivatized fullerene (C60-PEI-DOX) to facilitate combined chemotherapy and photodynamic therapy in one system, and DOX was covalently conjugated onto C60-PEI by the pH-sensitive hydrazone linkage. The release profiles of DOX from C60-PEI-DOX showed a strong dependence on the environmental pH value. The biodistributions of C60-PEI-DOX were investigated by injecting CdSe/ZnS (Qds) labeled conjugates (C60-PEI-DOX/Qds) into tumor-bearing mice. C60-PEI-DOX/Qds showed a higher tumor targeting efficiency compared with Qds alone. Compared with free DOX in an in vivo murine tumor model, C60-PEI-DOX afforded higher antitumor efficacy without obvious toxic effects to normal organs owing to its good tumor targeting efficacy and the 2.4-fold greater amount of DOX released in the tumor than in the normal tissues. C60-PEI-DOX also showed high antitumor efficacy during photodynamic therapy. The ability of C60-PEI-DOX nanoparticles to combine local specific chemotherapy with external photodynamic therapy significantly improved the therapeutic efficacy of the cancer treatment, the combined treatment demonstrating a synergistic effect. These results suggest that C60-PEI-DOX may be promising for high treatment efficacy with minimal side effects in future therapy.

PEGylated fullerene/iron oxide nanocomposites for photodynamic therapy, targeted drug delivery and MR imaging

Recently, fullerene and fullerene derivatives owning to their highly enriched physical and chemical properties have been widely explored for applications in many different fields including biomedicine. In this study, iron oxide nanoparticles (IONPs) were decorated onto the surface of fullerene (C60), and then PEGylation was performed to improve the solubility and biocompatibility of C60-IONP, obtaining a multi-functional C60-IONP-PEG nanocomposite with strong superparamagnetism and powerful photodynamic therapy capacity. Hematoporphyrin monomethyl ether (HMME), a new photodynamic anti-cancer drug, was conjugated to C60-IONP-PEG, forming a C60-IONP-PEG/HMME drug delivery system, which demonstrated an excellent magnetic targeting ability in cancer therapy. Compared with free HMME, remarkably enhanced photodynamic cancer cell killing effect using C60-IONP-PEG/HMME was realized not only in a cultured B16-F10 cells in vitro but also in an in vivo murine tumor model due to 23-fold higher HMME uptake of tumor and strong photodynamic activity of C60-IONP-PEG. Moreover, C60-IONP-PEG could be further used as a T2-contrast agent for in vivo magnetic resonance imaging. Our work showed C60-IONP-PEG/HMME had a great potential for cancer theranostic applications.

Studies on the toxicity of an aqueous suspension of C60 nanoparticles using a bacterium (gen. Bacillus) and an aquatic plant (Lemna gibba) as in vitro model systems

The increasing use of C60 nanoparticles and the diversity of their applications in industry and medicine has led to their production in a large scale. C60 release into wastewaters and the possible accumulation in the environment has raised concerns about their ecotoxicological impact. In the present study, an aqueous suspension of C60 nanoparticles was prepared and its potential toxicity studied in laboratory, using a bacterium (Bacillus stearothermophilus) and an aquatic plant (Lemna gibba) as model systems. C60 nanoparticles inhibited the growth of L. gibba, in contrast to that of the bacterium. Consistently, the ultrastructure and respiratory activity of bacterial cells were not affected by C60, but the contents of chlorophylls a and b and chloroplast oxygen production decreased considerably in L. gibba. Altogether, our results suggest that C60 aqueous dispersions must be viewed as an environmental pollutant, potentially endangering the equilibrium of aquatic ecosystems.

Profiling the molecular mechanism of fullerene cytotoxicity on tumor cells by RNA-seq

The interest on functionalized fullerenes in the field of nanomedicine has seen a significant increase in the past decade. However, the different methods employed to increase C60 solubility profoundly influence the physicochemical properties and the toxicological effects of these compounds, thus complicating the evaluation of their toxicity and potential therapeutic use. Here we report a whole-transcriptome RNA-seq analysis assessing the effect of two fullerenes (1 and 2) on gene expression in the human MCF7 cell line. Although these two compounds had previously been characterized by in vitro studies as having a cytotoxic and null effect respectively, to date the mechanisms at the basis of this different behavior and, more in general, at the basis of the effect of most fullerene derivatives in living cells are still completely unknown. Our data evidence that: (a) fullerene 2 caused a significant, time-dependent alteration of gene expression, whereas 1 only had a negligible effect; (b) the biological processes mostly influenced over the 48h experimental time course were transcription, protein synthesis, cell cycle progression and cell adhesion; (c) the gene expression signature of 2-treated cells was strikingly similar to those induced by selective inhibitors of mTOR signaling, thus suggesting an effect on this pathway for fullerene 2. Our work represents the first approach toward the application of RNA-seq to the study of the molecular mechanisms underlying the interaction of fullerenes with cellular systems and provides an objective view of the feasibility and the safety of these nanomaterials for a medical application.

In vitro evaluation of cellular influences induced by stable fullerene C₇₀ medium dispersion: induction of cellular oxidative stress

Fullerene is one of the nanocarbons that is expected to have applications to life science, such as nanomedicines. An understanding of the cellular influences of fullerene is essential for its application to life science. Although C₆₀ and C₇₀ are both known as major fullerenes, most previous reports about the cellular influences of fullerene are about C₆₀. Thus we evaluated the cellular influences caused by C₇₀. A stable and uniform C₇₀-medium dispersion was prepared. The dispersion was stable for the experimental period. Mitochondrial activity (MTT assay), colony forming ability (clonogenic assay), induction of oxidative stress (intracellular ROS and lipid peroxidation levels) and cellular uptake (TEM observation) in human keratinocyte HaCaT and lung carcinoma A549 cells exposed to C₇₀ were examined. C₇₀ did not influence mitochondrial activity. On the other hand, C₇₀ dispersion inhibited colony formation at the concentration of 25.2 μg mL(-1). Exposure to C₇₀ dispersion caused an increase in intracellular ROS and lipid peroxidation levels. The induction of intracellular ROS level was inhibited by pre-treatment of the cells by antioxidants. TEM observations of C₇₀ exposed cells showed cellular uptake of C₇₀. These results were similar to the cellular influences caused by C₆₀ which were reported by us previously. Although C₇₀ did not cause cell death, it caused the induction of intracellular oxidative stress.

Toxicological effects induced by the nanomaterials fullerene and nanosilver in the polychaeta Laeonereis acuta (Nereididae) and in the bacteria communities living at their surface

Fullerene (nC60) and nanosilver (nAg) are nanomaterials with bactericide properties. The increments in their use raise questions about their potential environmental impacts, including estuarine ones. The polychaete Laeonereis acuta (Nereididae) secretes mucus that is colonized by bacteria communities. We analyzed the antioxidant and oxidative damage responses of anterior, middle and posterior region of L. acuta and bacteria communities after nC60 or nAg exposure during 24 h. Molecular analysis showed a prevalence of Vibrio genera in the communities. Bacteria biomass was lowered in worms exposed to 1.0 mg/L of nAg. nC60 reduced total antioxidant capacity of bacteria from worms exposed to 0.1 mg/L. Worms anterior region presented lower antioxidant capacity after exposure to 1.0 mg nC60/L, and the same was observed in the posterior region of worms exposed to 1.0 mg nAg/L. Lipid peroxidation was reduced in the anterior region of worms exposed to nC60 and the opposite was observed in the posterior region.

Effects of aqueous stable fullerene nanocrystal (nC60) on copper (trace necessary nutrient metal): Enhanced toxicity and accumulation of copper in Daphnia magna

Our focus herein is to evaluate the potential interaction between nC60 and copper, a trace necessary metal, in light of the impact on toxicity. The non-observable effects concentration (NOEC) of nC60 was confirmed as 100μgL(-1) before. When Daphnia magna was exposed to the mixture of copper solution and nC60 suspension (100μgL(-1)), LC50 of 48h was lower than that when they were exposed to copper solution alone. This result clearly showed the decrease in NOEC of copper at the presence of nC60. Cu(2+)-ATPase activity was enhanced at the presence of nC60, indicating that copper transport involved with the uptake, distribution and depuration in body was increased. We further conducted experiments on accumulation of copper in D. magna. The observed equilibrium copper concentration in D. magna in the mixture of 100μgL(-1) nC60 and 1μgL(-1) copper solution reached 131μg (kg wet weight)(-1), which was more than twice that in copper solution only: 60μg (kg wet weight)(-1). This result demonstrated that the accumulation of copper in D. magna was significantly enhanced at the presence of even low nC60 concentration. Experiments also showed that copper was quickly adsorbed onto nC60. The absorption of copper onto D. magna was statistically correlated to the absorption of nC60 onto D. magna; this might be caused by nC60 facilitating the transfer of copper into D. magna. The absorption and desorption of copper to nC60 (pH=5.0) reached equilibrium quickly, which may be involved with the co-bioaccumulation and decrease in NOEC of Cu(2+) and nC60.