Photo-Induced Cytotoxicity of Water-Soluble Fullerene

The reaction of C₆₀ with poly(ethylene glycol) having a terminal primary amino group or a mixture of ethylene diamine and poly(ethylene glycol) having terminal carboxyl groups resulted in formation of water-soluble C₆₀ conjugates. These conjugates showed strong cytotoxicity to L929 cells upon visible light irradiation as a result of superoxide production.     

Electron Spin Resonance and Infrared Spectroscopy Study of the Polyvinylpyrrolidone-C60 Composite

Abstract

Recently we have found from ESR spectra that the electron charge transfer take place in the polyvinylpyrrolidone-C₆₀ composite. In this paper the polystyrene-C₆₀, polyvinylchloride-C₆₀, poly(ethylene glycol)-C₆₀, and poly(ethylene oxide)-C₆₀ composites are prepared and probed by the ESR technique for comparison. They show no signal which might be referred to the electron transfer. Along with this, we continue ESR study of the polyvinylpyrrolidone-C₆₀ composite and also present IR spectra, which indicate the involvement of the carbonyl group of polyvinylpyrrolidone into the electron charge transfer process.     

Engineering of poly(ethylene glycol) chain-tethered surfaces to obtain high-performance bionanoparticles

Abstract

A poly(ethylene glycol)-b-poly[2-(N,N-dimethylamino)ethyl methacrylate] block copolymer possessing a reactive acetal group at the end of the poly(ethylene glycol) (PEG) chain, that is, acetal-PEG-b-PAMA, was synthesized by a proprietary polymerization technique. Gold nanoparticles (GNPs) were prepared using the thus-synthesized acetal-PEG-b-PAMA block copolymer. The PEG-b-PAMA not only acted as a reducing agent of aurate ions but also attached to the nanoparticle surface. The GNPs obtained had controlled sizes and narrow size distributions. They also showed high dispersion stability owing to the presence of PEG tethering chains on the surface. The same strategy should also be applicable to the fabrication of semiconductor quantum dots and inorganic porous nanoparticles. The preparation of nanoparticles in situ, i.e. in the presence of acetal-PEG-b-PAMA, gave the most densely packed polymer layer on the nanoparticle surface; this was not observed when coating preformed nanoparticles. PEG/polyamine block copolymer was more functional on the metal surface than PEG/polyamine graft copolymer, as confirmed by angle-dependent x-ray photoelectron spectroscopy. We successfully solubilized the C₆₀ fullerene into aqueous media using acetal-PEG-b-PAMA. A C₆₀/acetal-PEG-b-PAMA complex with a size below 5 nm was obtained by dialysis. The preparation and characterization of these materials are described in this review.     

Effect of C60 on the thermal stability of polyethylene glycol grafted to it

The thermal degradation of regular polymer networks, cross-linked by C₆₀ molecules along the end groups of polyethylene glycol, has been investigated by mass-spectrometric thermal analysis for the example of polyethylene glycol grafted to fullerene C₆₀. The character of the thermal degradation of the networks is substantially different from that of free polyethylene glycol and other polymer systems investigated earlier. The grafting to C₆₀ increases the thermal stability of polyethylene glycol. Pis’ma Zh. Tekh. Fiz. 23, 19–24 (September 26, 1997)     

[60]Fullerene as a Novel Photoinduced Antibiotic

Abstract

The antibacterial activity of [60]fullerene (C₆₀), dissolved with poly(vinylpyrrolidone) K30 (PVP), was studied. Under photo‐irradiation, C₆₀/PVP aqueous solutions showed antibacterial activity, whereas PVP solution alone or fullerene solutions in the absence of light showed no activity. These results reveal that C₆₀ is a potentially good device as a photoinduced antibacterial agent.     

Star‐like Fullerene Containing Poly(Vinylpyrrolydone) Derivatives: Chloroform Solution Properties

Abstract

Star‐like fullerene C₆₀ derivatives with different branch number, synthesized by the reaction of fullerene with poly(vinylpyrrolydone) (PVP) macromolecules bearing the terminal amino‐groups, were investigated in solution by the viscometry, dielectric, and electrooptical Kerr‐effect methods in comparison with the ordinary linear PVPs of the same molecular mass. It was shown that covalent linkage of branches to fullerene through amino‐groups leads to appearance of a polar and optically anisotropic nanoparticle (amine‐substituted C₆₀) in the center of the coil of star‐like polymers that radically changes dielectric and electrooptical properties of the initial polymer. Effect of fullerene on the dimension of polymer coil had been detected also.     

Gd@C82 metallofullerenes for neutron capture therapy—fullerene solubilization by poly(ethylene glycol)-block-poly(2-(N,N-diethylamino)ethyl methacrylate) and resultant efficacy in vitro

Abstract

Poly(ethylene glycol)-block-poly(2-(N,N-diethylamino)ethyl methacrylate) (PEG-b-PAMA) was found to solubilize fullerenes such as C₆₀, and this technique was applied to metallofullerenes. Gd@C₈₂ was easily dissolved in water in the presence of PEG-b-PAMA without any covalent derivatization, forming a transparent complex about 20–30 nm in diameter. Low cytotoxicity was confirmed in vitro. Neutron irradiation of cultured cells (colon-26 adenocarcinoma) with Gd@C₈₂-PEG-b-PAMA-complexed nanoparticles showed effective cytotoxicity, indicating the effective emission of gamma rays and internal conversion electrons produced from the neutron capture reaction of Gd. This result suggests a potentially valuable approach to gadolinium-based neutron capture therapy.     

Effective poly(ethylene glycol) methyl ether grafting technique onto Nylon 6 surface to achieve resistance against pathogenic bacteria <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> and <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis>

Our study is focused on an efficient reduction of amide functional groups to secondary amine on Nylon 6 surface with borane–tetrahydrofuran (BH₃–THF) complex, followed by N-alkylation with benzyl chloride (C₆H₅CH₂Cl) which has been successfully used as a model system for further grafting of the reduced Nylon 6 surface by poly(ethylene glycol) methyl ether tosylate (Me-PEG-OTs). The amine-activated surface has been obtained by treatment of reduced Nylon 6 with n-butyllithium or tert-butyllithium in THF. Modified Nylon 6 has been found to be antibacterial particularly due to the presence of hydrophilic poly(ethylene glycol) methyl ether (H₃C-PEG) chains. The surface modifications were successfully characterized by various techniques. Water contact angle and free surface energy analyses indicated a significant change in the surface morphology. It was further supported by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy. Finally, antibacterial tests were performed against two pathogenic bacterial strains Pseudomonas aeruginosa (CCM 3955) and Staphylococcus aureus (CCM 3953).     

Synthesis and characterization of hydrolytically degradable copolyester biomaterials based on glycolic acid,sebacic acid and ethylene glycol

Copolyesters of glycolic acid (G) combined with sebacic acid (S) and ethylene glycol were synthesized in different molar ratios (G: 0–100% and S: 100–0%) and their hydrolytic degradation was studied and correlated with their structures. Based on the FTIR spectra of the homopolyesters and copolyesters and the normalized peak intensity of the I₂₉₁₈, I₂₈₄₈ and I₁₀₈₇ for the corresponding wavenumbers, it is concluded that the I₂₉₁₈ and the I₂₈₄₈ are in accordance with the mean number degree of polymerization of ethylene sebacate units and the I₁₀₈₇ is in accordance with the mean number degree of polymerization of glycolate units. Based on the XRD diffractograms, poly(ethylene sebacate) and poly(glycolic acid) belong to the monoclinic and the orthorhombic crystal system, respectively and both have higher crystallinity than the copolyesters. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model and four-parameter model. Three regions can been distinguished for the hydrolytic degradation by decreasing the molar feed ratio of sebacic acid, which are correlated with the changes of crystallinity. Two copolyesters are proposed: first the copolyester with high amount of glycolate units (S10G90) having higher hydrolytic degradation than G100 and second the copolyester with equal amount of glycolate and ethylene sebacate units (S50G50), having lower hydrolytic degradation than G100. These hydrolytically degradable copolyesters are soluble in common organic solvents, opposite to poly(glycolic acid) and could have perspectives for biomedical applications.     

Facilely dispersible magnetic nanoparticles prepared by a surface-initiated atom transfer radical polymerization

Facilely dispersible magnetic nanoparticles (Fe₃O₄) prepared by a surface-initiated atom transfer radical polymerization (ATRP) of poly (ethylene glycol) methyl ether monomethacrylate (PEGMA) are reported. The initiator of 2-bromoisobutyrate (BIB) for ATRP was immobilized onto the surface of Fe₃O₄ nanoparticles by the reaction between 2-bromoisobutyryl bromide (BIBB) and the hydroxyl group on the nanoparticles. The results indicated that the poly(poly(ethylene glycol) monomethacrylate) (PPEGMA) was successfully grafted onto the surface of the magnetic nanoparticles. The core-shell nanoparticles with particle size of ≈ 20 nm in water (about 20 mg/mL) are facilely dispersible and can be easily captured by a magnet with magnetic field of 2000 G.     

Addition of “Living” Polymers onto C60.

Abstract

Various “living” polymers were grafted onto C₆₀ The number of arms of the so obtained “star” molecules can be controlled by stoechiometry and/or by varying the reactivity of the carbanion on the “living” chain against a double bond on the C₆₀. Even the oxanion of “living” polyethylenoxide is able to add onto the reactive double bonds on C₆₀. In some conditions, the carbanions present on these alkaline salts of grafted fullerenes becomes able to initiate anionic polymerization of vinyl monomers. Using “living” poly(phenylvinylsulfoxide) as a precursor polymer for PA, polyacetylene chains could be attached to the fullerene.     

Antitumor Effect of Poly(Ethylene Glycol)-Modified Fullerene

Water-insoluble fullerene (C60) was chemically modified with poly(ethylene glycol) (PEG) to solubilize it in water. The C60-PEG conjugates, upon injecting intravenously, were accumulated in the tumor to a greater extent than in the normal tissue and exhibited prolonged C60 retention at the tumor tissue. Conjugate injection followed by light irradiation significantly suppressed the volume increase of tumor. We conclude that the PEG-modified C60 has a high potentiality as a. drug of photodynamic tumor therapy.     

Synthesis and Complex Study of Water‐Soluble Polymer Derivatives of C60 Fullerene

Abstract

The water‐soluble composites with fullerene content up to 5 wt% based on poly‐(N‐vinylpyrrolydone) (PVP) were obtained. The higher fullerene content is achieved by means of introducing tetraphenylporphyrine (TPP) and KBr into composites. The synthesis includes the formation of C₆₀–TPP complex and its further interaction with polymer. The formation of C₆₀–TPP complex was confirmed by ¹³C NMR, SANS, and translational diffusion. The hydrodynamic and electrooptical studies of C₆₀–TPP–PVP complexes indicate the higher symmetry of the polymer coil in the complex as compared to PVP. The C₆₀–PVP–KBr composites were also obtained by the solid state interaction under vacuum, KBr promoting the destruction of fullerene aggregates.     

Synthesis and properties of <Emphasis Type="Italic">O</Emphasis>-carboxymethyl chitosan/methoxy poly(ethylene glycol) graft copolymers

O-carboxymethyl chitosan/methoxy poly(ethylene glycol) graft copolymers (OCMCS-g-MPEGs) with different degrees of substitution (DS) were synthesized by reductive N-alkylation of chitosan with poly(ethylene glycol) aldehyde. The properties of OCMCS-g-MPEGs, including the solubility, structure, hydrodynamic behaviors, isoelectric point (IEP) and interaction with water-soluble chitosan, were investigated. As a PEGylated polyampholyte, OCMCS-g-MPEGs can resolve in water over all pH range and the pH value at IEP (pH_IEP) decreases when DS increases. The hydrodynamic behaviors of OCMCS-g-MPEGs in deionized H₂O are markedly affected by DS and pH_IEP in the experiment concentration range. The particle size of the complexes of OCMCS-g-MPEGs with water-soluble chitosan is strongly affected by the concentration of water-soluble chitosan and the pH value.     

Polymer grafting onto magnetite nanoparticles by “click” reaction

In this article, we described click chemistry methodology for the incorporation of biocompatible polymer chains to Magnetite nanoparticles (NPs). We used a reduction co-precipitation method to obtain Fe₃O₄ particles in aqueous solution. As a next step, magnetic NPs surface were modified by a silanization reaction with (3-bromopropyl)trimethoxysilane in order to introduce bromine groups on the particles surface which were converted to azide groups by the reaction with sodium azide. Acetylene functionalized poly(ethylene glycol) (a-PEG) and poly(ε-caprolactone) (a-PCL) were synthesized and grafted onto the surface of azide functionalized NPs via “click” reaction to obtain magnetic NPs. Success of the different functionalization processes at different stages was studied using Fourier Transform infrared spectroscopy (FTIR). The morphologies of magnetic NPs were further investigated by transmission electron microscopy (TEM). The magnetization and superparamagnetic behavior of naked Fe₃O₄ NPs and coated NPs at room temperature was investigated by the measurement of hysteresis curves using a Vibrating Sample Magnetometer (VSM).     

There are no Fullerenes in the K-T Boundary Layer

Abstract

Careful re-examination of the Cretacous-Tertiary boundary layer material that was reported earlier to contain C₆₀, confirms that there is a peak in the HPLC of the extract having a retention time similar to that of C₆₀ (the basis of the earlier claim). However, mass spectrometric analysis shows this to be merely a mixture of hydrocarbons. No traces of either C₆₀ or C₇₀ are present under conditions capable of detecting as little as 50 pg (0.001 part per billion in the original material), this sensitivity being four times greater than that given in the earlier report. These findings are entirely consistent with the known high oxidative instability of fullerenes.     

CRYSTALLIZATION,MORPHOLOGY, AND DYNAMIC MECHANICAL BEHAVIOR OF SUPRAMOLECULAR [60]FULLERENE-CONTAINING POLY(ETHYLENE-co-ACRYLIC ACID)

ABSTRACT

A multifunctional [60]fullerene derivative AEAF was melt-mixed with poly(ethylene-co-acrylic acid) (PEAA20). The strong interaction between AEAF and PEAA20, as shown by x-ray photoelectron spectroscopy, enables AEAF to be well dispersed in the amorphous phase of PEAA20. WAXD revealed that the crystallinity of PEAA20 is reduced and the crystallites are deformed by the addition of AEAF. The storage modulus and dynamic glass transition temperature of the polymer increase upon the incorporation of AEAF. Unlike C₆₀ and a monofunctional C₆₀ derivative, AEAF is able to sustain its reinforcing effect in the glass-rubber transition region.     

MISCIBILITY OF POLY(VINYLIDENE FLUORIDE) WITH C60-CONTAINING POLY(ETHYL METHACRYLATE), POLY(METHYL ACRYLATE), OR POLY(ETHYL ACRYLATE)

C₆₀ was incorporated onto poly(ethyl methacrylate), poly(methyl acrylate) and poly(ethyl acrylate). The miscibility of poly(vinylidene fluoride) (PVDF) with the C₆₀-containing polymers was examined. PVDF is miscible with all the six C₆₀-containing polymer samples as shown by the optical clarity of the melt and the existence of a single glass transition temperature in each blend. The polymer-polymer interaction parameters of various blend systems were evaluated by the melting point depression method.     

Light Scattering Study of Aqueous Poly(Vinyl)pyrrolidone–Fullerene C70 Solutions

Abstract

It was shown by static and dynamic light scattering that poly(vinyl)pyrrolidone (PVP) molecules form large intermolecular complexes (clusters) with C₇₀ in aqueous solutions. The molecular weights and dimensions of PVP–C₇₀ clusters increase both with the increase of fullerene content and the molecular weight of the matrix PVP. However, two different diffusion coefficients were detected by dynamic light scattering. The slow mode was explained as diffusion of large PVP–C₇₀ clusters. The fast mode represents free PVP molecules in solution. Dimensions of clusters revealed in aqueous PVP–C₇₀ solutions are less than that for PVP–C₆₀ by factor of 2.5–3.     

Time-Resolved Mass Spectrometric Studies of Fullerenes and Endohedral Fullerenes

Abstract

The energetics and dynamics of C₂ evaporations from fullerene radical cations C_n ^?+ were studied with and without ion trapping techniques. Electron space charge trapping was applied in electron ionization experiments. RF trapping in a Paul type ion source was applied for Laser MPI. Appearance energies, kinetic energy releases and metastable fractions were determined. the experimental data were modeled by finite heat bath theory (FHBT) and by RRKM/QET. Evaporation (binding) energies as well as conventional and intrinsic kinetic shifts were deduced. Our results support the following conclusions: (a) C₆₀ sits on the leading edge of a magic shell, with C₅₈ only slightly less stable and C₆₂ considerably less stable than C₆₀; (b) Dissociative decay is able to compete with radiative decay of C₆₀ ^?+ only at internal energies in excess of 37.6 eV (T_b>2300 K); (c) a Ne endohedral atom has a slightly stabilizing effect on the C₆₀ ^?+ cage whereas La is strongly stabilizing the C₈₂ ^?+ cage; (d) C₂ loss is a true evaporation in the sense of having a loose transition state with no reverse activation energy; (e) the C₂ evaporations are statistical in nature and theories such RRKM/QET and FHBT are in excellent agreement with experimental observations.