Chemiluminescence in the ozonation of C60 aqueous dispersions

Two types of chemiluminescence (CL) arising upon ozonation of crystalline, amorphous, and molecular aqueous dispersions of C₆₀ prepared in different ways were discovered and studied. The weak long-wavelength CL-1 (λ_max > 650 nm) is due to thermocatalytic decomposition of ozone on the surface of fullerene micro- and nanoparticles. The bright short-wavelength CL-2 (λ_max = 570 nm) is caused by generation of electronically excited states of the products of C₆₀ oxidation with ozone. CL-1 appears upon ozonation of aqueous dispersions of C₆₀ consisting of surface-hydrated crystalline micro- and nanoparticles by low concentrations of ozone. CL-2 is exhibited upon ozonation of nano-sized C₆₀ aqueous dispersions and colloid solutions, which contain C₆₀ molecules surrounded by a strong aqueous shell and their associates, by higher concentrations of ozone. Owing to shielding by the hydration shell, C₆₀ fullerene in aqueous dispersions is much less reactive towards ozone and forms oxidation products of different composition as compared with C₆₀ in organic solvents.     

Reactions of chlorofullerene C60Cl6 with N-substituted piperazines

It was shown for the first time that reactions of C₆₀ halides with aliphatic amines provide a facile route for the synthesis of aminofullerenes, valuable precursors for water-soluble cationic fullerene derivatives. Particularly, chlorofullerene C₆₀Cl₆ and N-substituted piperazines were investigated in this work. It was shown that substitution of chlorine atoms in C₆₀Cl₆ by amine groups is accompanied by partial elimination of addends from the fullerene cage that yields mixtures of di-, tetra- and, hexaaminofullerenes as the final products. Separation of these mixtures by column chromatography resulted in isolation of pure 1,4-diaminofullerenes; this procedure gives much higher and more reproducible yields of these compounds than direct oxidative photoaddition of secondary amines to C₆₀. ESI mass spectrometry and NMR spectroscopy data showed that hexaaminofullerene isomers are major components in inseparable mixtures of polyaddition products. Polyaminofullerenes were found to be readily soluble in aqueous acids; these solutions are unstable because of a facile substitution of protonated amine groups with hydroxyls. Nevertheless, the use of other amine substrates in the investigated reaction can potentially allow the preparation of more stable water-soluble cationic fullerene derivatives for biological studies.     

Luminescent techniques in investigation of the biological properties of fullerene-based hybrid nanostructures

It has been shown that amino acid derivatives of C₆₀ fullerene (ADFs) are effective quenchers of phosphorescence of the triplet probes eosin and erythrosine. The rate constants of erythrosine phosphorescence quenching by ADFs in aqueous solutions and model membranes have been determined. Using the triplet probe technique, the ability of ADFs to be transported across the lipid bilayer into the inner space of liposomes have been revealed. By monitoring a change in the fluorescence intensity of a luminescent hybrid structure based on C₆₀-proline and eosin, the distribution of the hybrid structure in animal organs was established. The stability of hybrid structures subjected to various chemical and biological impacts was studied by recording the fluorescence of a Gd@C₈₂-based hybrid structure.     

Insulin Surface Acoustic Wave Immunosensor Based on Immobilized C60/Anti‐Insulin Antibody

Immobilized fullerene C₆₀/anti‐insulin antibody was prepared and applied in shear horizontal surface acoustic wave (SH‐SAW) immunosensors to detect insulin in aqueous solutions. The immobilizations of anti‐insulin onto fullerene were studied through a C₆₀/PVC coated SH‐SAW sensor system in liquid. The partially irreversible frequency response for an anti‐insulin antibody was observed by the desorption study, which implied that fullerene could chemically react with anti‐insulin. C₆₀/anti‐insulin coating materials were successfully prepared and identified with an FTIR spectrometer. The C₆₀/anti‐insulin coated SH‐SAW immunosensors were developed and applied for detection of insulin in aqueous solutions. Within the range of normal human insulin concentration, the SH‐SAW immunosensors immobilized with C₆₀/anti‐insulin exhibited linear frequency responses to the concentration of insulin with a sensitivity of 130 Hz/pM. The SH‐SAW immunosensor immobilized with C₆₀/anti‐insulin showed a detection limit of 0.58 pM for insulin in aqueous solution. The interference of various common bio‐species in human blood, e.g. urea, ascorbic acid, tyrosine, and metal ions, to the SH‐SAW immunosensor immobilized with C₆₀/anti‐insulin for insulin was investigated. These common bio‐species interferences showed nearly no interference to the SAW immunosensors coated with C₆₀/anti‐insulin. The reproducibility of the SH‐SAW immunosensor immobilized with C₆₀/anti‐insulin for insulin was also investigated and is discussed.     

Solubilization of fullerene C60 in micellar solutions of different solubilizers

Fullerene (C₆₀), the third carbon allotrope, is a classical engineered material with the potential application in biomedicine. However, extremely high hydrophobicity of fullerene hampers its direct biomedical evaluation and application. In this work, we investigated the solubilization of fullerene using 9 different solubility enhancers: Tween 20, Tween 60, Tween 80, Triton X-100, PVP, polyoxyethylene (10) lauryl ether, n-dodecyl trimethylammonium chloride, myristyl trimethylammonium bromide and sodium dodecyl sulphate and evaluated its antioxidant activity in biorelevant media. The presence of C₆₀ entrapped in surfactant micelles was confirmed by UV/VIS spectrometry. The efficacy of each modifier was evaluated by chemometric analysis using experimental data for investigating the relationship between solubilization and particle size distribution. Hierarchical clustering and principal component analysis was applied and showed that non-ionic surfactants provide better solubilization efficacy (>85%). A correlation was established (r = 0.975) between the degree of solubilization and the surfactant structure. This correlation may be used for prediction of C₆₀ solubilization with non-tested solubility modifiers. Since the main potential biomedical applications of fullerene are based on its free radical quenching ability, we tested the antioxidant potential of fullerene micellar solutions. Lipid peroxidation tests showed that the micellar solutions of fullerene with Triton and polyoxyethylene lauryl ether kept high radical scavenging activity, comparable to that of aqueous suspension of fullerene and BHT. The results of this work provide a platform for further solubilization and testing of pristine fullerene and its hydrophobic derivatives in a biological benign environment.     

Adsorption modification of solid surfaces with aqueous solutions of fullerene C60 derivatives containing maleimide and dipeptide addends

The regularities of the adsorption modification of different solid surfaces with aqueous solutions of amino-acid derivatives of fullerene C₆₀ (ADF) that contain the maleimide and dipeptide addends were studied by the methods of wetting and Quartz Crystal Microbalance (QCM). It was found that, despite the absence of surface activity at the solution-air interface, ADFs are well adsorbed at the solution-solid interface. On high-energy surfaces with different charges in aqueous media, at neutral pH, the studied ADF act as ionic surfactants with polar groups charged opposite to the solid surface. The modification of polymers with AFD solutions results in the hydrophilization of their surfaces as in the case of classical low-molecular surfactants.     

双亲性C60衍生物水相聚集行为

富勒烯C₆₀几乎不溶于水中,从而阻碍了对富勒烯的进一步研究和潜在应用。双亲性C₆₀衍生物在水相中自组装形成聚集体,在水相具有一定的溶解度,其特殊的结构及性能引起了科学家的广泛关注。本文对双亲性C₆₀衍生物在水相中聚集行为的研究现状及研究进展进行了详细系统的介绍。本文第一部分主要阐述了双亲性C₆₀衍生物的结构,根据修饰到C₆₀表面的功能基类型对双亲性C₆₀衍生物进行了分类。第二部分主要阐述了双亲性C₆₀衍生物在水相的聚集行为以及pH值、溶剂极性、浓度、温度和抗衡离子等因素对聚集行为的影响。     

Star-shaped polymers with the fullerene C60 branching center

The anionic methods for the synthesis of homo- and heteroarm (hybrid) star-shaped polymers using fullerene C₆₀ aPre considered. The possibilities of fullerene C₆₀ as an agent of combination of living polymer chains and the procedures of transformation of polymer derivatives of C₆₀ (hexaadducts) into polyfunctional macroinitiators of anionic polymerization of vinyl monomers are shown. The methods for functionalization of polymer fullerene derivatives and their combinations into structures of complex controlled architecture are presented. The structural features and initiating properties of the living polymer fullerene derivatives and their role in the formation of heteroarm star-shaped macromolecules with the controlled number of branches and predetermined molecular weight characteristics of the arms are discussed. The hydrodynamic properties of the star-shaped fullerene-containing polymers are considered. The data on the small-angle neutron scattering study of self-organization of the stars in solutions are presented.     

Laser flash photolysis of fullerols of C60 and of C70 in aqueous solutions

Fullerols of C₆₀ and of C₇₀ [C₆₀(OH)_n, C₇₀(OH)_m], water-soluble fullerene derivatives, unlike some other fullerene derivatives (such as C₆₀ (C₄H₆O), C₆₀ (C₃H₇N) and C₆₀ [C(COOEt)₂]_x), do not result in excited triplet state but in ionization via monophotonic process in aqueous solutions with 248 nm laser. The quantum yields of formation of hydrated electron (Φ_e ⁻) are determined to be 0.08 and 0.11 for fullerols of C₆₀ and of C₇₀ respectively at room temperature (ca. 15°C) with KI solution used as reference. By laser flash photolysis and oxidation of sulfate radical anion SO₄ ⁻, the fullerol radical cation or neutral radical of C₆₀ is confirmed to be existent and the transient absorption spectra of fullerol radical cation of C₇₀ are observed for the first time. Project supported by the National Natural Science Foundation of China     

Antioxidant properties of water-soluble amino acid derivatives of fullerenes and their role in the inhibition of herpes virus infection

The antioxidant properties of water-soluble amino acid derivatives of fullerene C₆₀ (ADF) were studied. It was shown by the change in the concentration of malonic dialdehyde in rat brain mitochondria that the ADF are antioxidants. They were shown by the change in the luminol glow to possess antiradical activity, which is determined by the acceptor properties of the fullerene spheroid and is independent of the structure of the attached addends. Stereoselectivity of the antioxidant properties of the enantiomers of amino acid derivatives of fullerene C₆₀ was found. The L-isomers of ADF inhibit lipid peroxidation, whereas the D-isomers do not inhibit. A reliable correlation between the development of cytomegalovirus (CMV) infection and the process of lipid peroxidation in the cell culture was established. An efficient inhibitor of the CMV infection from the class of amino acid derivatives of fullerene with antioxidant activity was obtained.

     

Electrocatalysis of Some Biomacromolecules at C60 / DDAB Films

Electrochemically stable fullerene films made from cationic surfactant DDAB containing C₆₀ on a glassy carbon electrode were produced in an aqueous solution, and electrocatalysis of some biomacromolecules at C₆₀ / DDAB films was studied.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Structure formation of fullerene-containing propylene oxide oligomers in deuterium water

Structure formation of propylene oxide oligomers with terminal hydrophobic aliphatic fragment and of oligo(propylene oxides) additionally containing covalently bonded fullerene C₆₀ in deuterium water was studied by small-angle neutron scattering. Propylene oxide chains containing a long hydrophobic fragment undergo organization into spherical micelles, whereas the fullerene(C₆₀)-containing derivatives form rodlike structures (elongated “chains” of cross-linked micelles).     

Anion radicals of [60]fullerenes. An EPR study

Photochemically induced electron transfer in homogeneous systems (using triethylamine donor) and heterogeneous systems (using photoexcited TiO₂ suspension) was applied in in situ reduction of [60]fullerene. The anion radicals generated were characterized by means of EPR and VIS/near-IR spectroscopy. Narrow EPR lines were found. Radical A with g_A=2.0000 and peak-to-peak width, pp_A=0.09mT was observed as the primary product; followed by its consecutive product B with g_B=2.0006, pp_B=0.04mT, and in some cases product C with g_C=2.0009 and pp_c<0.1 mT. Radical A was assigned to [60]fullerene mono-anion, also characterized by a near-IR band at 1077 nm. B is presumably di-anion or a dimeric form of mono-anion. Identical results were also obtained using cathodic in situ reduction. Applying these generation techniques to [60]fullerene derivatives produced narrow EPR lines analogous to those described for pristine [60]fullerene. This was the case not only in organic solvents, but also in aqueous solutions. The results obtained present a contrast with the original ex situ EPR investigations describing [60]fullerene mono-anion with wide lines. According to the results presented here, the narrow and wide EPR lines do not represent contradictory phenomena, but are an integral part of the relatively complicated manifestations of various fullerene states and both will have to be seriously considered in the future.     

Comparative study of sorption properties of fullerene C60 and dibenzo-24-crown-8 by gas chromatography and solid-phase microextraction

Flat concentrators for flow solid-phase microextrcation, packed with carbon materials (C₆₀ and Carbochrom C), DB-24C-8 crown ether, and its composite with fullerene were prepared and tested. The possibility of using these units for concentrating organic compounds of different classes in the vapor-gas phase and aqueous solutions was studied.     

Synthesis of [60]fullerene-glycopyranosylaminopyrimidin-4-one conjugates

The synthesis of several C₆₀ derivatives containing a 6-(β-d-glycopyranosylamino)pyrimidin-4-one unit and a C₆₀-uridine conjugate is described. The fullerene derivatives bearing a 4-(β-d-glycopyranosylamino)pyrimidin-4-one moiety were synthesised by 1,3-dipolar cycloaddition reactions of C₆₀ with azomethine ylides generated in situ from the corresponding 5-formylpyrimidin-4-one derivatives and N-methylglycine. The synthesis of the C₆₀-uridine conjugate involved the selective protection of the 2′- and 3′-hydroxyl groups of uridine, esterification, cyclopropanation of C₆₀ and, finally, the deprotection of the hydroxyl groups. One of the fullerene-glycopyranosylaminopyrimidin-4-one conjugates was characterised by single-crystal X-ray crystallography. Differentiation between pairs of diastereoisomers, for several fullerene derivatives, was achieved through the study of their gas-phase fragmentations.     

Liquid‐Crystalline Mixed [5 : 1]Hexa‐adducts of [60]Fullerene. Preliminary Communication

A liquid‐crystalline mixed [5 : 1]hexa‐adduct of [60]fullerene was synthesized by addition of two different malonate derivatives onto C₆₀. The hexa‐adduct derivative 2 was prepared by a stepwise synthetic procedure (fullerene→mono‐adduct of C₆₀→hexa‐adduct of C₆₀). Cyanobiphenyl and octyloxybiphenyl derivatives were selected as mesogens. The malonate derivatives showed either a monotropic nematic phase or a monotropic smectic A phase, and the hexa‐adduct derivative gave rise to an enantiotropic smectic A phase.     

Specifics of light scattering in solutions of fullerene-containing polymers

The molecular mass and hydrodynamic dimensions of molecules of two fullerene-containing polymers which differ in the preparation procedure and the mode of fullerene C₆₀ binding were determined by means of static and dynamic light scattering and transport techniques (diffusion, sedimentation, gel permeation chromatography). It was established that the molecular masses of polymeric C₆₀ derivatives determined by means of static light scattering are substantially above those measured by means of the transport techniques. Using as an example a polystyrene specimen containing 6.2 wt % C₆₀ prepared according to the widespread technique of solvent evaporation from a mutual fullerene and polymer solution, it was shown that the multicomponent nature, the compositional inhomogeneity, and a lack of coincidence in the signs of refractive index increments for structurally different components of fullerene-containing polymers may cause anomalies in the intensity of light scattering by solutions of these compounds.     

Preparation of water‐soluble pullulans bearing pendant C60 and their aqueous solubility

Water‐soluble fullerene‐bearing pullulans were successfully prepared by the addition reaction of azide‐substituted pullulans with fullerene C₆₀ . The chemical structure of the products was characterized by IR, UV, and NMR spectroscopy. It was found that the saturation solubility of the C₆₀ moiety strongly depends on the degree of substitution (DS) of the sample, indicating that an optimum DS value of the C₆₀ moiety exists for its aqueous solubility.