Using C60 fullerenes for photodynamic inactivation of mosquito iridescent viruses

This article describes the photodynamic inactivation of mosquito iridescent virus (MIV) Aedes flavescens in the presence of water-soluble C(60) fullerenes. It has been observed that the photodynamic inactivation of MIV for about 1 h reduces the infectious titre of the virus in large wax-moth larvae Galleria mellonella to 4.5 lg ID(50)/mL. The influence of the C(60) concentration on its anti-viral activity was tested in the concentration range from 1 to 0.001 mg/mL. It has been found that C(60) is able to inactivate the iridovirus even in low concentrations. Consequently, the findings of this work suggest that photoexcited C(60) fullerenes can be successfully used for the inactivation of iridoviruses in biological systems.     

Antiamyloid properties of fullerene C<Subscript>60</Subscript> derivatives

A comparative estimation of the ability of complexes of fullerene C₆₀ with polyvinylpyrrolidone and fullerene C₆₀ derivatives (the sodium salt of the polycarboxylic derivative of fullerene C₆₀, sodium fullerenolate), has been carried out. The fullerenes destroyed amyloid fibrils of the Aβ(1–42) peptide of the brain and the muscle X-protein. A study of the effect of fullerenes on muscle actin showed that complexes of fullerene C₆₀ with polyvinylpyrrolidone and sodium fullerenolate did not prevent the filament formation of actin, nor did they destroy its filaments in vitro. Conversely, sodium salt of the polycarboxylic derivative of fullerene C₆₀ destroyed actin filaments and prevented their formation. It was concluded that sodium fullerenolate and complexes of fullerene C₆₀ with polyvinylpyrrolidone are the most effective antiamyloid compounds among the fullerenes examined.     

Computational simulation study on the anion recognition properties of functionalized tetraphenyl porphyrins

Dedicated bond force constant and bulk modulus of C _n fullerenes (n = 20, 28, 36, 50, 60) are computed using density functional theory (DFT). DFT predicts bond force constants of 611, 648, 675, 686, and 691 N/m, for C₂₀, C₂₈, C₃₆, C₅₀, and C₆₀, respectively, indicating that the bond force constant increases for larger fullerenes. The bulk modulus predicted by DFT increases with decreased fullerene diameter, from 0.874 TPa for C₆₀ to 1.830 TPa for C₂₀. The bond force constants predicted by DFT are then used as an input for finite element analysis (FEA) of the fullerenes, considered as spatial frames in structural models where the bond stiffness is represented by the DFT-computed bond force constant. In agreement with DFT, FEA predicts that smaller fullerenes are stiffer, and underestimates the bulk modulus with respect to DFT. The difference between the FEA and DFT predictions of the bulk modulus decreases as the size of the fullerene increases, from 20.9 % difference for C₂₀ to only 4 % difference for C₆₀. Thus, it is concluded that knowing the appropriate bond force constant, FEA can be used as a plausible approximation to model the elastic behavior of small fullerenes.

     

Comparative Computational Study of Interaction of C60-Fullerene and Tris-Malonyl-C60-Fullerene Isomers with Lipid Bilayer: Relation to Their Antioxidant Effect

Oxidative stress induced by excessive production of reactive oxygen species (ROS) has been implicated in the etiology of many human diseases. It has been reported that fullerenes and some of their derivatives–carboxyfullerenes–exhibits a strong free radical scavenging capacity. The permeation of C₆₀-fullerene and its amphiphilic derivatives–C₃-tris-malonic-C₆₀-fullerene (C₃) and D₃-tris-malonyl-C₆₀-fullerene (D₃)–through a lipid bilayer mimicking the eukaryotic cell membrane was studied using molecular dynamics (MD) simulations. The free energy profiles along the normal to the bilayer composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) for C₆₀, C₃ and D₃ were calculated. We found that C₆₀ molecules alone or in clusters spontaneously translocate to the hydrophobic core of the membrane and stay inside the bilayer during the whole period of simulation time. The incorporation of cluster of fullerenes inside the bilayer changes properties of the bilayer and leads to its deformation. In simulations of the tris-malonic fullerenes we discovered that both isomers, C₃ and D₃, adsorb at the surface of the bilayer but only C₃ tends to be buried in the area of the lipid headgroups forming hydrophobic contacts with the lipid tails. We hypothesize that such position has implications for ROS scavenging mechanism in the specific cell compartments.     

Polymerization of miniature fullerenes in the cavity of nanotubes

The polymerization of four fullerenes C₂₈ in the cavity of closed single-walled carbon nanotube C₇₄₀ was investigated. It was shown that the formation of the oligomer of four C₂₈ fullerenes is observed at the pressure of 37.73 GPa, which is created by means of the charged fullerene C₆₀. Fullerene C₆₀ moves under the influence of an external electric field.     

Effect of fullerenes C<Subscript>60</Subscript> on X-protein amyloids

The inhibitory effect of hydrated fullerene C₆₀ and the sodium salt of the fullerene polycarboxylic derivative C₆₀Cl(C₆H₄CH₂COONa)₅ on the formation of amyloid fibrils by X-protein in vitro has been studied by electron microscopy. It is shown that these compounds not only destroy mature amyloid fibrils but also prevent the formation of new fibrils. This property of fullerenes, which are nanoparticles, can be used to develop a novel medical nanotechnology in the therapy for amyloidoses.     

Direct preparation of radioactive fullerenes as a tracer for applications

The C₆₀ and C₇₀ fullerenes were irradiated by high-energy γ-rays and charged particles. The irradiated samples were dissolved in CS₂ and/or toluene and filtered to remove insoluble by-products. Finally, radioactive fullerenes and products labeled with¹¹C or¹³N were isolated and detected in the liquid phase by radiochromatography. It was found that (1) not only¹¹C or¹³N radioactive monomer fullerenes but also their dimers (trimers and, possibly, tetramers) were produced by recoil implantation process following nuclear reaction and (2) the radioactive fullerene labeled with¹¹C yields has led to high yields.     

Antioxidant action of sugar-pendant C60 fullerenes

The action of C₆₀ fullerene and its derivatives as a radical-scavenging antioxidant has received much attention, but their reactivity toward free radicals and antioxidant capacity have not been well elucidated yet. In the present study, the reactivity of the two types of water-soluble, sugar-pendant C₆₀ fullerenes, C₆₀-1S and C₆₀-2S, toward peroxyl radical and their effect against human plasma lipid peroxidation were measured. The rate constants for the reaction of C₆₀-1S and C₆₀-2S with peroxyl radicals were obtained from their effect on the bleaching of β-carotene in lipid-SDS micelle system as 4.6 × 10³ and 8.0 × 10³ M^?1 s^?1 at 37 °C, respectively. They inhibited the free radical-induced lipid peroxidation in human plasma in a concentration-dependent manner. These results suggest that the sugar-pendant fullerenes C₆₀-1S and C₆₀-2S act as a radical-scavenging antioxidant with the activity similar to the phenolic antioxidants.     

Ab initio molecular dynamics simulation on the formation process of He@C60 synthesized by explosion

The applications of endohedral non-metallic fullerenes are limited by their low production rate. Recently, an explosive method developed in our group shows promise to prepare He@C₆₀ at fairly high yield, but the mechanism of He inserting into C₆₀ cage at explosive conditions was not clear. Here, ab initio molecular dynamics analysis has been used to simulate the collision between C₆₀ molecules at high-temperature and high-pressure induced by explosion. The results show that defects formed on the fullerene cage by collidsion can effectively decrease the reaction barrier for the insertion of He into C₆₀, and the self-healing capability of the defects was also observed.

Antioxidant Activity of Supramolecular Water-Soluble Fullerenes Evaluated by β-Carotene Bleaching Assay

We investigated the antioxidant activity of supramolecular water-soluble fullerenes, polyvinylpyrrolidone (PVP)-entrapped C₆₀, and γ-cyclodextrin (CD)-bicapped C₆₀, based on comparable β-carotene bleaching assay. Antioxidant activity against reactive oxygen species (ROS) generated by three different methods, (i) autoxidation of linoleic acid, (ii) hydrogen peroxide promoter, and (iii) photoirradiation, was evaluated as percent of inhibition relative to a control experiment in view of the bleaching rate constant (k _obs) as well as the persistent absorbancy of β-carotene. Water-soluble fullerenes exhibit significant inhibitory effects on the oxidative discoloration of β-carotene in any system.     

Chemistry of Convex versus Concave Carbon: The Reactive Exterior and the Inert Interior of C60

Do the chemical properties of the surface of a carbon sheet depend on its shape? This question addresses a criterion for chemical behaviour that has hardly been investigated previously. The current neglect of this question may be due to the fact that suitable model systems with easily distinguishable graphitic surfaces were essentially unknown until the discovery [1] and synthesis [2,3,4] of fullerenes, nanotubes and other related forms of carbon. In this study, we present the first systematic comparison of the chemical behaviour of the convex outer and the concave inner surfaces of C₆₀ by analysing the results of semiempirical and DFT calculations on exohedral and endohedral complexes with H- and F-atoms as well as with the methyl radical. We show that such extremely reactive species are trapped by the extraordinary inert inner surface of C₆₀ and do not undergo chemical reactions.     

Computing fullerene encapsulation of non-metallic molecules: N2@C60 and NH3@C60

Some endohedral fullerenes have been considered as possible candidate species for molecular memories. Recently, the encapsulation inside the fullerene cages has been extended from atoms to small molecules, for example the nitrogen molecule was placed inside the fullerene cage. The observed N₂@C₆₀ endohedral is computed in the paper together with NH₃@C₆₀, which was not yet observed. The computations are based on structural optimizations using density-functional theory (DFT) methods. In the optimized structures, the analytical harmonic vibrational analysis was carried out and the encapsulation energetics were evaluated using the second order Møller-Plesset (MP2) perturbation treatment. The lowest-energy structure has the N₂ unit oriented towards a pair of parallel pentagons so that the complex exhibits D _5d symmetry. At the MP2 level, the encapsulation of N₂ into C₆₀ brings a potential energy gain of ? 9.3 kcal/mol while that for NH₃ is ? 5.2 kcal/mol. The entropy term is also evaluated, yielding the standard Gibbs-energy change at room temperature for the encapsulation of N₂ and NH₃ of ? 2.6 and 1.5 kcal/mol, respectively. Some computed structural and vibrational characteristics are also reported. Emerging broader landscape of future applications of such encapsulates in nanoscience and nantechnology is discussed.     

Efficiency of the monofunctionalized C60 fullerenes as membrane targeting agents studied by all-atom molecular dynamics simulations

Abstract

Transmembrane translocation of C₆₀ fullerenes functionalized by the single amino-derivative in neutral and charged forms was studies by extensive all-atom molecular dynamics simulations. It is shown that these complexes exhibit very strong affinity to the membrane core, but their spontaneous translocation through the membrane is not possible at practical time scale. In contrast, free amino derivatives translocate through the membrane much easier than their complexes with fullerenes, but do not have pronounced affinity to the membrane interior. Our results suggest that monofunctionalized C₆₀ could be extremely efficient membrane targeting agents, which facilitate accumulation of the water-soluble compounds in the hydrophobic core of lipid bilayer.     

Understanding the Reduced Efficiencies of Organic Solar Cells Employing Fullerene Multiadducts as Acceptors

The use of fullerenes with two or more adducts as acceptors has been recently shown to enhance the performance of bulk‐heterojunction solar cells using poly(3‐hexylthiophene) (P3HT) as the donor. The enhancement is caused by a substantial increase in the open‐circuit voltage due to a rise in the fullerene lowest unoccupied molecular orbital (LUMO) level when going from monoadducts to multiadducts. While the increase in the open‐circuit voltage is obtained with many different polymers, most polymers other than P3HT show a substantially reduced photocurrent when blended with fullerene multiadducts like bis‐PCBM (bis adduct of Phenyl‐C₆₁‐butyric acid methyl ester) or the indene C₆₀ bis‐adduct ICBA. Here we investigate the reasons for this decrease in photocurrent. We find that it can be attributed partly to a loss in charge generation efficiency that may be related to the LUMO‐LUMO and HOMO‐HOMO (highest occupied molecular orbital) offsets at the donor‐acceptor heterojunction, and partly to reduced charge carrier collection efficiencies. We show that the P3HT exhibits efficient collection due to high hole and electron mobilities with mono‐ and multiadduct fullerenes. In contrast the less crystalline polymer Poly[[9‐(1‐octylnonyl)‐9H‐carbazole‐2,7‐diyl]‐2,5‐thiophenediyl‐2,1,3‐benzothiadiazole‐4,7‐diyl‐2,5‐thiophenediyl (PCDTBT) shows inefficient charge carrier collection, assigned to low hole mobility in the polymer and low electron mobility when blended with multiadduct fullerenes.     

The Antioxidative Effect of Fullerenes during the Peroxidation of Methyl Linoleate in Toluene

The antioxidative effect of fullerenes C₆₀ and C₇₀ was examined by measuring the inhibition of methyl linoleate (MeL) peroxidation in toluene initiated by 2,2′-azobis(2,4-dimethylvaleronitrile) (AMVN). The fullerenes retarded the formation of MeL hydroperoxides and lowered the rate of propagation. The reaction rates of fullerenes with AMVN-derived peroxyl radicals were much higher than that of MeL. These results indicate that fullerenes can act as retarders of lipid peroxidation, though their activity is low compared with that of α-tocopherol.     

Electrostatic binding of substituted metal phthalocyanines to enterobacterial cells: Its role in photodynamic inactivation

The effect of ionic substituents in zinc and aluminum phthalocyanine molecules and of membrane surface charge on the interaction of dyes with artificial membranes and enterobacterial cells, as well as on photosensitization efficiency was studied. It has been shown that increasing the number of positively charged substituents enhances the extent of phthalocyanine binding to Escherichia coli cells. This, along with the high quantum yield of singlet oxygen generation, determines efficient photodynamic inactivation of Gram-negative bacteria by zinc and aluminum octacationic phthalocyanines. The effect of Ca²⁺ and Mg²⁺ cations and pH on photodynamic inactivation of enterobacteria in the presence of octacationic zinc phthalocyanine has been studied. It has been shown that effects resulting in lowering negative charge on outer membrane protect bacteria against photoinactivation, which confirms the crucial role in this process of the electrostatic interaction of the photosensitizer with the cell wall. Electrostatic nature of binding is consistent with mainly electrostatic character of dye interactions with artificial membranes of different composition. Lower sensitivity of Proteus mirabilis to photodynamic inactivation, compared to that of E. coli and Salmonella enteritidis, due to low affinity of the cationic dye to the cells of this species, was found.     

Extraction and Antioxidant Activities of Magnolia kwangsiensis Figlar & Noot. Leaf Polyphenols

Microwave‐assisted extraction was employed to extract polyphenols from the leaf of Magnolia kwangsiensis Figlar & Noot . The yield of polyphenols was 2.44±0.02 % under the optimal conditions of RSM: acetone concentration of 70 %, ratio of solvent to material of 21 mL?g^?1 and extraction time of 16 min. The antioxidant activities were evaluated in terms of total antioxidant ability, reducing power, DPPH ^? and ^? OH scavenging activity. Results showed the polyphenols presented potential antioxidant activities, especially the stronger scavenging activity on ^? OH. In term of ^? OH scavenging activity, the IC₅₀ value of NKA‐9 purification was 0.335 mg mL^?1, equivalent to 35.23 % of V_C. The IC₅₀ values of crude extract and ethyl acetate extract were 0.580 and 0.828 mg mL^?1, equivalent to 60.99 % and 87.07 % of V_C. Results indicated that M. kwangsiensis leaf polyphenols present potential antioxidant activities that make it beneficial for human health by preventing or reducing oxidative damage.     

Anti-Influenza Activity of C60 Fullerene Derivatives

The H1N1 influenza A virus, which originated in swine, caused a global pandemic in 2009, and the highly pathogenic H5N1 avian influenza virus has also caused epidemics in Southeast Asia in recent years. Thus, the threat from influenza A remains a serious global health issue, and novel drugs that target these viruses are highly desirable. Influenza A RNA polymerase consists of the PA, PB1, and PB2 subunits, and the N-terminal domain of the PA subunit demonstrates endonuclease activity. Fullerene (C₆₀) is a unique carbon molecule that forms a sphere. To identify potential new anti-influenza compounds, we screened 12 fullerene derivatives using an in vitro PA endonuclease inhibition assay. We identified 8 fullerene derivatives that inhibited the endonuclease activity of the PA N-terminal domain or full-length PA protein in vitro. We also performed in silico docking simulation analysis of the C₆₀ fullerene and PA endonuclease, which suggested that fullerenes can bind to the active pocket of PA endonuclease. In a cell culture system, we found that several fullerene derivatives inhibit influenza A viral infection and the expression of influenza A nucleoprotein and nonstructural protein 1. These results indicate that fullerene derivatives are possible candidates for the development of novel anti-influenza drugs.     

The studies on the aromaticity of fullerenes and their holmium endohedral compounds

Density functional theory BLYP/DNP was employed to optimize a series of fullerenes and their holmium endohedral compounds, including C₂₀, Ho@C₂₀, Ho³⁺@C₂₀, C₆₀, Ho@C₆₀, Ho³⁺@C₆₀,C₇₀, Ho@C₇₀, Ho³⁺@C₇₀ C₇₈, Ho@C₇₈, Ho³⁺@C₇₈, C₈₂,Ho@C₈₂ and Ho³⁺@C₈₂. DFT semi core pseudospot approximation was taken into consideration in the calculations of the element holmium because of its particular electronic structure. Fullerenes and their holmium endohedral compounds’ aromaticity were studied in terms of structural criteria, energetic criteria, and reactivity criteria. The results indicate that the aromaticity of fullerenes was reduced when a holmium atom was introduced into the carbon cage, and the endohedral fullerenes’ reactive activity enhance; but the aromaticity of the carbon cage increased when a Ho³⁺ cation was encapsulated into a fullerene. Calculations of aromaticity and stability indicate that two paths can lead to the similar aim of preparing holmium endohedral fullerenes; that is, they can form from either a holmium atom or a holmium cation (Ho³⁺) reacting with fullerenes, respectively, and the latter is more favorable.