Strongly optical absorptive nanofluids and rheology in bonded fullerene C60 via poly(vinyl pyrrolidone) molecules in water

This study was performed to illustrate how a model grafting between C₆₀ and poly (vinyl pyrrolidone) PVP of small flocculates results in maximum optical absorption and rheology in a nanofluid in correlation to microstructure while C₆₀-content was varied in an ideal optical host of 40.0 g/L PVP in water. Broad absorption band observed in the 250–450 nm region in the π → π* C(sp²) electron transition in PVP-grafted C₆₀ of small assemblies indicate a cross-linking between the PVP and C₆₀ molecules in a complex structure. Above a threshold value of 11.2 μM C₆₀, a deviation from a linear Beer-Lambert law could arise from a solubilization capacity limit of PVP to solubilize C₆₀ molecules in a charge transfer (CT) C₆₀:PVP complex. A nearly 4 times enhancement in the shear viscosity (η) of PVP solution by raising the C₆₀-content by a factor ～15 explicitly divulges that insertion of C₆₀ helps in expanding the anchoring between two moieties in a C₆₀:PVP CT complex. As the imposition of shear force breaks the soft C₆₀:PVP complex into small nanostructures, the η-value relaxes slowly to the base value on increasing the shear rate from 10 to 100 s^?1. Synthesis of C₆₀:PVP nanofluid exhibiting such characteristics are useful for drug delivery, lubrication, antibacterial activity, and many biological applications.     

Charge-transfer interaction between C60 fullerene and alkylnaphthalenes

A series of alkylnaphthalenes, namely 1,4-dimethylnaphthalene, 2,6-diethylnaphthalene, 2-ethylnaphthalene and pure naphthalene are not able to form Diels-Alder adducts with C₆₀ fullerene but produce a series of 1:1 charge-transfer complexes (CTC) where the aromatic compounds act as donor and C₆₀ as acceptor. The spectrophotometric analysis of these CTC has permitted to determine the equilibrium constants of the CTC formation at four different temperatures and the relative enthalpies and entropies of formation. The C₆₀-alkylnaphthalenes and C₆₀-naphthalene were identified as weakly bound CTC. Using the Mulliken theory of the CTC also the degree of charge transfer α was determined, confirming the results already suggested by the equilibrium constants, i.e., the weakly interaction between the donor and the acceptor considered.     

Preparation,characterization and in vitro and in vivo evaluation of a solid dispersion of Naringin

Naringin (NA) is one of typical flavanone glycosides widely distributed in nature and possesses several biological activities including antioxidant, anti-inflammatory, and antiapoptotic. The aim of this study was to develop solid dispersion (SD) and to improve the dissolution rate and oral bioavailability of NA. NA–SD was prepared by the traditional preparation methods using PEG6000, F68, or PVP K30 as carrier at different drug to carrier ratios. According to the results of solubility and in vitro dissolution test, the NA–PEG6000 (1:3) SD was considered as an optimal formulation to characterize by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry and powder X-ray diffraction. Furthermore, oral bioavailabilities of NA–PEG6000 (1:3) SD and NA–suspension with the same dosage were investigated in SD rats. The results confirmed the formation of SD and the pharmacokinetic parameters of NA–PEG6000 (1:3) SD (C_max?=?0.645?±?0.262?µg/ml, AUC_0–t?=?0.471?±?0.084?µg/ml?h) were higher than that of NA–suspension (C_max?=?0.328?±?0.183?µg/ml, AUC_0–t =?0.361?±?0.093?µg/ml?h). Based on the results, the SD is considered as a promising approach to enhance the dissolution rate and oral bioavailability of NA.     

Noncovalent complexes of Ih−C80 fullerene with phthalocyanines

The noncovalent interactions of I_h?C₈₀ fullerene with free-base and 3d transition M(II) phthalocyanines (where M = Mn, Fe, Co, Ni, Cu, Zn) were studied at the PBE-D/DNP level of density functional theory. The optimized complex geometries, formation energies and electronic parameters were analyzed and compared to those reported previously for similar dyads with C₆₀. In the complexes with I_h?C₈₀, the central metal atom (as well as one H atom of H₂Pc) is always coordinated to a C_6:6:6 atom of C₈₀ cage, exhibiting only one general interaction pattern. The shortest M^…C_C80 and N^…C_C80 distances are notably longer than in dyads with C_60, and the distortion of Pc macrocycle is less significant. In none of C₈₀-based dyads the formation of new coordination bonds by metal atoms was observed. The bonding strength for Pc–C₈₀ dyads varies approximately to the same degree of 20 kcal/mol as for their Pc–C₆₀ analogues, however negative formation energies for Pc–C₈₀ dyads are on average by 5–6 kcal/mol lower than for their C₆₀ analogues. While in closed-shell Pc–fullerene systems HOMO is usually found totally on Pc molecule, in the case of C₈₀-based dyads only a minor HOMO fraction can be detected for some dyads on Pc, with the major one always distributed over fullerene cage. As a result, the calculated HOMO-LUMO gap energies turn to be very low, around 0.1 eV. Analysis of spin density plots revealed that H₂Pc+C₈₀, NiPc+C₈₀ and ZnPc+C₈₀ dyads behave as closed-shell systems, like similar noncovalent complexes of Pcs with C₆₀.     

[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.     

A microemulsion of puerarin–phospholipid complex for improving bioavailability: preparation,in vitro and in vivo evaluations

Puerarin is a phytochemical with various pharmacological effects, but poor water solubility and low oral bioavailability limited usage of puerarin. The purpose of this study was to develop a new microemulsion (ME) based on phospholipid complex technique to improve the oral bioavailability of puerarin. Puerarin phospholipid complex (PPC) was prepared by a solvent evaporation method and was characterized by X-ray diffraction and infrared spectroscopy. Pseudo-ternary phase diagrams were constructed to investigate the effects of different oil on the emulsifying performance of the blank ME. Intestinal mucosal injury test was conducted to evaluate safety of PPC-ME, and no sign of damage on duodenum, jejunum and ileum of rats was observed using hematoxylin-eosin staining. In pharmacokinetic study of PPC-ME, a significantly greater C_max (1.33?µg/mL) was observed when compared to puerarin (C_max 0.55?µg/mL) or PPC (C_max 0.70?µg/mL); the relative oral bioavailability of PPC-ME was 3.16-fold higher than puerarin. In conclusion, the ME combined with the phospholipid complex technique was a promising strategy to enhance the oral bioavailability of puerarin.     

Garenoxacin pharmacokinetics in patients undergoing maintenance hemodialysis

Introduction: Studies on the pharmacokinetics of the antibiotic garenoxacin (GRNX) in patients with renal insufficiency are lacking. In this study, we attempted to ascertain the appropriate dose of GRNX in patients undergoing maintenance hemodialysis (MH) based on pharmacokinetic parameters and clinical outcomes. Methods: Six male patients with infections who were undergoing MH received 200 mg GRNX once daily. Blood samples were taken before and at 1, 2, 4, 6, 12, and 24 hours after GRNX administration. Plasma GRNX concentrations were measured using high‐performance liquid chromatography. Findings: The mean maximum plasma concentration (C_max) was 3.00 ± 1.12 µg/mL, time to maximum plasma concentration (T_max) was 3.0 ± 2.0 hours, and area under the curve for 24 hours (AUC_0–24) was 40.7 ± 16.7 µg·h/mL. The half‐life (T_1/2) of GRNX could not be calculated because plasma concentrations remained high 24 hours after administration. C_max was strongly associated with the GRNX dose per kilogram body weight (r = 0.85, P = 0.03). Clinically, fever resolved within 3 days of GRNX administration and C‐reactive protein levels returned to normal 14 days after administration. One patient experienced temporary increases in serum transaminase levels. Discussion: MH patients receiving 200 mg GRNX once daily for infection showed a reduced C_max but similar AUC_0–24 compared with healthy individuals. While this study evaluated the effect of GRNX treatment, further research is needed to assess the accumulation of GRNX and the impact of continuous administration on its pharmacokinetics, as well as to prevent the development of resistant mutants.     

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.     

Desorption of fullerene C60 from a mixture with a copolymer of trifluorochloroethylene and vinylidene fluoride

Thermal desorption mass spectrometry has been used to study the desorption of fullerene C₆₀ molecules from a mixture with a copolymer of trifluorochloroethylene and vinylidene fluoride. The temperature range of the C₆₀ yield from the copolymer mixture is substantially lower (approximately 100°C lower) than the temperature range for the sublimation of pure C₆₀ molecules. The temperature range of the C₆₀ yield from the copolymer mixture is the same as that for the desorption of HCl and HF formed as a result of copolymer cross linking reactions. The desorption of C₆₀ from the copolymer mixture is a two-stage process correlated with the stages of HCL and HF formation for which the temperatures at the maximum desorption rates differ. The results suggest that the copolymer cross-linking processes and the desorption of C₆₀ molecules are interrelated. Pis’ma Zh. Tekh. Fiz. 23, 20–26 (December 26, 1997)     

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.     

Three-ways crossover bioequivalence study of cephalexin in healthy Malay volunteers

Context: Although the general pharmacokinetics of cephalexin is quite established up-to-date, however, no population-based study on Cephalexin pharmacokinetics profile in Malay population has been reported yet in the literature.

Objective: The objective of this study was to investigate the pharmacokinetics and to compare the bioavailability of three cephalexin products, Ospexin® versus MPI Cephalexin® tablet and MPI Cephalexin® capsule, in healthy Malay ethnic male volunteers in Malaysia.

Material and method: A single dose, randomized, fasting, three-period, three-treatment, three-sequence crossover, open label bioequivalence study was conducted in 24 healthy Malay adult male volunteers, with 1 week washout period. The drug concentration in the sample was analyzed using high performance liquid chromatography.

Result: The mean (SD) pharmacokinetic parameter results of Ospexin® were C_max, 17.39 (4.15) μg/mL; AUC_0–6, 28.90 (5.70) µg/mL?*?h; AUC_0–∞, 30.07 (5.94) µg/mL?*?h; while, those of MPI Cephalexin® tablet were C_max, 18.29 (3.01) μg/mL; AUC_0–6, 30.02 (4.80) µg/mL?*?h; AUC0_0–∞, 31.33 (5.18) µg/mL?*?h and MPI Cephalexin® capsule were C_max, 18.25 (3.92) μg/mL; AUC_0–6, 30.04 (5.13) µg/mL?*?h; AUC_0–∞, 31.22 (5.29) µg/mL?*?h.

Conclusion: The 90% confidence intervals for the logarithmic transformed C_max, AUC_0–6 and AUC_0–∞, of Ospexin® versus MPI Cephalexin® tablet and Ospexin® versus MPI Cephalexin® capsule were between 0.80 and 1.25. Both C_max and AUC met the predetermined criteria for assuming bioequivalence. The pharmacokinetic profile of cephalexin in Malay population does not vary much from other world population.     

π‐Conjugated Polymer–Fullerene Covalent Hybrids via Ambient Conditions Diels–Alder Ligation

The established ability of graphitic carbon‐nanomaterials to undergo ambient condition Diels–Alder reactions with cyclopentadienyl (Cp) groups is herein employed to prepare fullerene‐polythiophene covalent hybrids with improved electron transfer and film forming characteristics. A novel precisely designed polythiophene (M _n 9.8 kD, ? 1.4) with 17 mol% of Cp‐groups bearing repeat unit is prepared via Grignard metathesis polymerization. The UV/Vis absorption and fluorescence (λ_ex 450 nm) characteristics of polythiophene with pendant Cp‐groups (λ_max 447 nm, λ_e‐max 576 nm) are comparable to the reference poly(3‐hexylthiophene) (λ_max 450 nm, λ_e‐max 576 nm). The novel polythiophene with pendant Cp‐groups is capable of producing solvent‐stable free‐standing polythiophene films, and non‐solvent assisted self‐assemblies resulting in solvent‐stable nanoporous‐microstructures. ¹H‐NMR spectroscopy reveals an efficient reaction of the pendant Cp‐groups with C₆₀. The UV/Vis spectroscopic analyses of solution and thin films of the covalent and physical hybrids disclose closer donor‐acceptor packing in the case of covalent hybrids. AFM images evidence that the covalent hybrids form smooth films with finer lamellar‐organization. The effect is particularly remarkable in the case of poorly soluble C₆₀. A significant enhancement in photo‐voltage is observed for all devices constituted of covalent hybrids, highlighting novel avenues to developing efficient electron donor‐acceptor combinations for light harvesting systems.     

Adsorption of amino acids by fullerenes and fullerene nanowhiskers

Abstract

We have investigated the adsorption of some amino acids and an oligopeptide by fullerene (C₆₀) and fullerene nanowhiskers (FNWs). C₆₀ and FNWs hardly adsorbed amino acids. Most of the amino acids used have a hydrophobic side chain. Ala and Val, with an alkyl chain, were not adsorbed by the C₆₀ or FNWs. Trp, Phe and Pro, with a cyclic structure, were not adsorbed by them either. The aromatic group of C₆₀ did not interact with the side chain. The carboxyl or amino group, with the frame structure of an amino acid, has a positive or negative charge in solution. It is likely that the C₆₀ and FNWs would not prefer the charged carboxyl or amino group. Tri-Ala was adsorbed slightly by the C₆₀ and FNWs. The carboxyl or amino group is not close to the center of the methyl group of Tri-Ala. One of the methyl groups in Tri-Ala would interact with the aromatic structure of the C₆₀ and FNWs. We compared our results with the theoretical interaction of 20 bio-amino acids with C₆₀. The theoretical simulations showed the bonding distance between C₆₀ and an amino acid and the dissociation energy. The dissociation energy was shown to increase in the order, Val < Phe < Pro < Asp < Ala < Trp < Tyr < Arg < Leu. However, the simulation was not consistent with our experimental results. The adsorption of albumin (a protein) by C₆₀ showed the effect on the side chains of Try and Trp. The structure of albumin was changed a little by C₆₀. In our study Try and Tyr were hardly adsorbed by C₆₀ and FNWs. These amino acids did not show a different adsorption behavior compared with other amino acids. The adsorptive behavior of mono-amino acids might be different from that of polypeptides.     

Surface potential measurement of organic photo-diode consisting of fullerene/copper phthalocyanine double layered device

We investigated the surface potential built across the electrode/fullerene (C₆₀) or copper phthalocyanine (CuPc) interface and C₆₀/CuPc interface as a function of the thickness of the semiconductor film in the dark condition and under illumination. The surface potential of C₆₀ on Au, Al and Mg changes negatively with the increment of film thickness and it saturates at − 0.25, − 1.0 and − 1.5 V within 20 nm. The Fermi level alignment at C₆₀/electrode interface is established within ∼ 20 nm from electrode, and very high electric field exists due to the displacement of negative electronic charges from electrode into C₆₀. On the other hand, the surface potential of CuPc on ITO changes to + 0.1 V, and the work functions of C₆₀ and CuPc were estimated as 5.0 eV and 4.7 eV. C₆₀ film also accepts electrons from CuPc at hetero-junction interface, and the Fermi-level alignment was again obtained at C₆₀/CuPc interface under illumination. The built-in potential of ca. 0.3 V formed at C₆₀/CuPc interface was considered as the origin of the reduction of open-circuit voltage in ITO/CuPc/C₆₀/Au device compared with the optimum value of 0.6 V. On the other hand, the very high electric field formed at C₆₀/Mg contact improved the photovoltaic properties.     

Optical spectroscopy on alkali-metal doped fullerene compounds

We report our optical investigations on the alkali-metal-doped C₆₀ over a broad energy spectral range, extending from the far-infrared up to the ultraviolet. The occurrence of superconductivity in A₃C₆₀ compounds has raised quite a bit of controversy with respect to arguments, favouring pairing mechanism based on electron-phonon interactions with low frequency intermolecular vibrations or with high frequency intramolecular modes. We discuss our experimental results within the standard Eliashberg electron-phonon theory of superconductivity, in order to single out the relevant phonon excitation for the pairing mechanism. The Eliashberg calculation strongly supports a pairing mechanism mediated by high-frequency intramolecular phonon modes, in accord with the implications of the weak coupling BCS limit. Moreover, we present the electrodynamic response of the quasi-one-dimensional A₁C₆₀ compounds. Our experimental findings demonstrate that Rb₁C₆₀ and Cs₁C₆₀ undergo a metal-insulator phase transition below about 50 K, while K₁C₆₀ remains, however, metallic at all temperatures. The possibility of a broken symmetry ground state due to the formation of a spin-density-wave (SDW) condensate for the Rb and Cs compound, as suggested by the magnetic properties, is discussed.     

Thermodesorption states of fullerene C60 in the polyimide-fullerene system

The data of thermodesorption mass spectrometry indicate that fullerene C₆₀ molecules are desorbed from a polyimide (PI) surface at temperatures below the PI decomposition onset temperature, while the desorption of C₆₀ from the bulk begins in the temperature region of the polymer decomposition. It is suggested that strong chemical bonds between C₆₀ and PI macromolecules are formed in the bulk in the stage of the polyamic acid preparation and are broken upon destruction of the polymer macromolecules. The character of C₆₀ thermodesorption from the PI surface depends on thickness of the surface film of fullerene C₆₀.     

Fragmentation of multiply ionized fullerene molecules

The dissociation of C₆₀ fullerene molecules has been studied by means of an analysis of the kinetic energies of charged fragments formed upon the capture of several electrons from C₆₀ by multiply charged Ar⁶⁺ ions. The kinetic energies of fragment ions of a multiply ionized C₆₀ molecule are distributed in accordance with the Coulomb explosion mechanism of dissociation.     

Adsorption of amino acids by fullerenes and fullerene nanowhiskers

We have investigated the adsorption of some amino acids and an oligopeptide by fullerene (C₆₀) and fullerene nanowhiskers (FNWs). C₆₀ and FNWs hardly adsorbed amino acids. Most of the amino acids used have a hydrophobic side chain. Ala and Val, with an alkyl chain, were not adsorbed by the C₆₀ or FNWs. Trp, Phe and Pro, with a cyclic structure, were not adsorbed by them either. The aromatic group of C₆₀ did not interact with the side chain. The carboxyl or amino group, with the frame structure of an amino acid, has a positive or negative charge in solution. It is likely that the C₆₀ and FNWs would not prefer the charged carboxyl or amino group. Tri-Ala was adsorbed slightly by the C₆₀ and FNWs. The carboxyl or amino group is not close to the center of the methyl group of Tri-Ala. One of the methyl groups in Tri-Ala would interact with the aromatic structure of the C₆₀ and FNWs. We compared our results with the theoretical interaction of 20 bio-amino acids with C₆₀. The theoretical simulations showed the bonding distance between C₆₀ and an amino acid and the dissociation energy. The dissociation energy was shown to increase in the order, Val < Phe < Pro < Asp < Ala < Trp < Tyr < Arg < Leu. However, the simulation was not consistent with our experimental results. The adsorption of albumin (a protein) by C₆₀ showed the effect on the side chains of Try and Trp. The structure of albumin was changed a little by C₆₀. In our study Try and Tyr were hardly adsorbed by C₆₀ and FNWs. These amino acids did not show a different adsorption behavior compared with other amino acids. The adsorptive behavior of mono-amino acids might be different from that of polypeptides.     

Applications of fullerene beams in analysis of thin layers

Molecular dynamics computer simulations have been employed to model ejection of particles from Ag{1 1 1} metal substrate and thin benzene overlayer bombarded by fullerene cluster projectiles. The sputtering yields are analyzed depending on the size (from C₂₀ up to C₅₄₀) and the kinetic energy (5-20 keV) of a projectile. It has been found that for clean metal substrate bombarded by 15 keV projectiles the maximum ejection is stimulated by the impact of the C₆₀ cluster. However, the size of the cluster projectile maximizing the yield depends on the kinetic energy of the cluster, shifting towards larger clusters as the impact energy increases. For a thin benzene overlayer, the yield increases monotonically with the size of the cluster within investigated range of fullerene projectiles and kinetic energies.     

Normal-state transport properties of fullerene superconductors

The normal-state transport properties of alkali-metal-doped fullerene crystals are explored. The Hall effect has been measured in K_xC₆₀ from room temperature toT _c . The electrical resistivity for K₃C₆₀ and Rb₃C₆₀ has been measured over a wide temperature range (20–650 K), and notable differences are observed for the materials at both low and high temperatures. The electrical resistivity of Rb₃C₆₀ has been measured in hydrostatic pressures up to 9 kbar. The resistivity is highly pressure sensitive. The transport results give an insight into the normal-state conduction mechanism and thus have consequences for the superconductivity mechanism.