Structural and thermal properties of polystyrene/CoAl-layered double hydroxide nanocomposites prepared via solvent blending: effect of LDH loading

Nanocomposites of polystyrene (PS) with modified CoAl-layered double hydroxide (CoAl–LDH) were prepared via simple solvent blending method and the effect of CoAl–LDH content on the structural and thermal properties was investigated. The structural and thermal properties of the nanocomposites were characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The nano-scale dispersion of the CoAl–LDH layers in the PS matrix is verified by the (0?0?3) XRD reflection of the modified CoAl–LDH. The XRD data show that the exfoliated PS/CoAl–LDH nanocomposites can be obtained by controlling the LDH loading of about 5?wt%. TEM analysis also confirms the formation of exfoliated PS nanocomposites with 3?wt% and 5?wt% LDH loading. The thermal degradation temperature of the PS nanocomposite containing 5?wt% CoAl–LDH is found to be 12°C higher than that of pure PS when 50% weight loss is selected as a point of comparison. The glass transition temperature (T _g) of PS nanocomposites is about 14°C higher than that of pure PS.     

In vitro comparative evaluation of monolayered multipolymeric films embedded with didanosine-loaded solid lipid nanoparticles: a potential buccal drug delivery system for ARV therapy

Drug delivery via the buccal route has emerged as a promising alternative to oral drug delivery. Didanosine (DDI) undergoes rapid degradation in the gastrointestinal tract, has a short half-life and low oral bioavailability, making DDI a suitable candidate for buccal delivery. Recent developments in buccal drug delivery show an increased interest toward nano-enabled delivery systems. The advantages of buccal drug delivery can be combined with that of nanoparticulate delivery systems to provide a superior delivery system. The aim of this study was to design and evaluate the preparation of novel nano-enabled films for buccal delivery of DDI. Solid lipid nanoparticles (SLNs) were prepared via hot homogenization followed by ultrasonication and were characterized before being incorporated into nano-enabled monolayered multipolymeric films (MMFs). Glyceryl tripalmitate with Poloxamer 188 was identified as most suitable for the preparation of DDI-loaded SLNs. SLNs with desired particle size (PS) (201?nm), polydispersity index (PDI) (0.168) and zeta potential (?18.8?mV) were incorporated into MMFs and characterized. Conventional and nano-enabled MMFs were prepared via solvent casting/evaporation using Eudragit RS100 and hydroxypropyl methylcellulose. Drug release from the nano-enabled films was found to be faster (56% versus 20% in first hour). Conventional MMFs exhibited higher mucoadhesion and mechanical strength than nano-enabled MMFs. SLNs did not adversely affect the steady state flux (71.63?±?13.54?µg/cm²?h versus 74.39?±?15.95?µg/cm²?h) thereby confirming the potential transbuccal delivery of DDI using nano-enabled MMFs. Nano-enabled buccal films for delivery of DDI can be successfully prepared, and these physico-mechanical studies serve as a platform for future formulation optimization work in this emerging field.     

SYNTHESES AND PHOTOPHYSICAL PROPERTIES OF FULLEROPYRROLIDINES CONTAINING PHOTOACTIVE UNITS

The syntheses and a systematic spectroscopic study of a series of fulleropyrrolidines containing polycyclic aromatic hydrocarbon are reported. The fulleropyrrolidines were characterized by UV, IR, ¹H-NMR, ¹³C-NMR and ESI-MS. According to the absorption spectra and the electrochemical data, no significant interaction was observed between the polycyclic aromatic rings and fullerene moiety in the ground state of fulleropyrrolidines. However, the fluorescence and nanosecond transient absorption spectra indicate that these fulleropyrrolidines have sensitized fluorescence of fullerene due to the intramolecular energy transfer, and that their excited triplet state production are considerably reduced, which in turn result in a lower optical limiting performance compared with that of C₆₀.     

Degradation of fullerene C60 by human myeloperoxidase and some reaction products

Abstract

The biodegradation of the fullerene molecule C₆₀ under the action of the human myeloperoxidase enzyme accompanied by a complete loss of the topology of the fullerene core. Analysis of this reaction mixture using UV and FTIR spectroscopy, chromatographic and mass spectrometry methods showed that the degradation proceeds without the formation of significant amounts of hydroxylated compounds. Among other intermediate compounds aromatic compounds were detected.     

Focused Light Study of Surface Plasmons on Ag and the Anomalous Skin Effect

Abstract

The optical response of thin Ag films has been studied using surface plasmon-polaritons excited via a novel focused light attenuated total reflection technique, which is described in detail. The results show that the anomalous skin effect is important in room temperature condensed polycrystalline Ag films at visible wavelengths, especially with the removal of defects on annealing the films. Incorporation of the ASE theory and surface scattering into the reflectivity model provides better agreement between theory and experiment.     

Nanoparticles as tool for enhanced ophthalmic delivery of vancomycin: a multidistrict-based microbiological study,solid lipid nanoparticles formulation and evaluation

Context: A microbiological multidistrict-based survey from different Egyptian governorates was conducted to determine the most prevalent causative agents of ocular infections in the Egyptian population. Antibiotic sensitivity testing was then performed to identify the most potent antimicrobial agent. Vancomycin (VCM) proved the highest activity against gram-positive Staphylococcus bacteria, which are the most commonly isolated causative agents of ocular infection. However, topically applied VCM suffers from poor ocular bioavailability because of its high molecular weight and hydrophilicity. Objective: The aim of the present study was to develop VCM-loaded solid lipid nanoparticles (SLNs) using water-in-oil-in-water (W/O/W) double emulsion, solvent evaporation technique to enhance ocular penetration and prolong ophthalmic residence of VCM. Method: Two consecutive full factorial designs (2⁴ followed by 3²) were adopted to study the effect of different formulation and process parameters on SLN formulation. The lipid type and structure, polyvinyl alcohol (PVA) molecular weight and concentration, sonication time, as well as lipid:drug ratio were studied as independent variables. The formulated SLN formulae were evaluated for encapsulation efficiency (EE%), particle size (PS), and zeta potential as dependent variables. Results: The statistically-optimized SLN formula (1:1 ratio of glyceryltripalmitate:VCM with 1% low molecular weight PVA and 1?min sonication time) had average PS of 277.25?nm, zeta potential of ?20.45, and 19.99% drug encapsulation. Scanning and transmission electron micrographs showed well-defined, spherical, homogenously distributed particles. Conclusion: The present study suggests that VCM incorporation into SLNs is successfully achievable; however, further studies with different nanoencapsulation materials and techniques would be valuable for improving VCM encapsulation.     

B3LYP/6-31G∗//SAM1 Calculations of C36 Fullerene and quasi-Fullerene Cages

Abstract

The recently isolated fullerene C₃₆ is computed by the SAM1 method with energetics refined at the B3LYP/6-31G? level. Twelve low-energy cages are considered in detail, exhibiting both fullerene (pentagons and hexagons) and quasi-fullerene (also squares and heptagons) pattern. In contrast to other fullerene systems, the SAM1 and B3LYP/6-31G? methods do produce somewhat different energetics. Consequently, the equilibrium isomeric composition at high temperatures is different, too. In the best affordable B3LYP/6-31G? approach the fullerene cage with the topological D _6d symmetry represents the most populated species at high temperatures. Hence, an agreement with the solid-state NMR experiment is achieved at the B3LYP/6-31G? theoretical level.     

Optical and Electrical Properties of Star-Like Fullerene-Containing Polymers

Abstract

Polystyrene and polyethyleneoxide films both containing fullerene, C₆₀, designated as FPS and FPEO were investigated by the ellipsometry, photoluminescence spectra and electrical dc conductivity methods. The FPS and FPEO films display complex refractive index of 1.7 ? 10.05 and 1.45 ? 10.0 respectively. The photoluminescence maximum attributed to C₆₀ shifted to higher photon energies proportionally to with the increase of the number of the polymer rays attached. The shift can be described by the linear relationship ΔE=004N, where ΔE is the shift in eV and N is the number of polymer rays attached. The magnitude of dc conductivity exhibited by the FPS films varied directl proportionally to molar concentration of C₆₀     

Electron structure of thin fullerene films deposited by various methods

The valence-band photoelectron spectra and the photoelectron energy loss spectra behind the C1s peak in the X-ray photoelectron spectra were studied in thin fullerene films deposited by various methods. The fine structure in the density of states near the valence band bottom observed for the fullerene films deposited by the method of pulsed supersonic molecular beam (SMB) with a helium carrier may be indicative of the presence of a long-range order. The spectra of π-plasmon losses in the films obtained by methods of thermal and SMB deposition exhibit a significant difference that can be related to a closer packing of C₆₀ molecules in the latter case.     

Thermal-Decomposition Spectra of Submicrometer Films of Polybutylmethacrylate–C<Subscript>60</Subscript> Fullerene Composite: Effects of Filler Concentration and UV Irradiation

Thermal-desorption mass spectra of optically thin films of polybutylmethacrylate–C₆₀ fullerene composite with various fullerene concentrations have been analyzed. The effects of UV radiation on the films under atmospheric conditions have been examined.     

Photocatalytic properties of porous TiO2/Ag thin films

In this study, nanocrystalline TiO₂/Ag composite thin films were prepared by a sol-gel spin-coating technique. By introducing polystyrene (PS) spheres into the precursor solution, porous TiO₂/Ag thin films were prepared after calcination at a temperature of 500 °C for 4 h. Three different sizes (50, 200, and 400 nm) of PS spheres were used to prepare porous TiO₂ films. The as-prepared TiO₂ and TiO₂/Ag thin films were characterized by X-ray diffractometry (XRD) and by scanning electron microscopy to reveal structural and morphological differences. In addition, the photocatalytic properties of these films were investigated by degrading methylene blue under UV irradiation.When PS spheres of different sizes were introduced after calcination, the as-prepared TiO₂ films exhibited different porous structures. XRD results showed that all TiO₂/Ag films exhibited a major anatase phase. The photodegradation of porous TiO₂ thin films prepared with 200 nm PS spheres and doped with 1 mol% Ag exhibited the best photocatalytic efficiency where ∼ 100% methylene blue was decomposed within 8 h under UV exposure.     

Fabrication of solid lipid nanoparticles of lurasidone HCl for oral delivery: optimization,in vitro characterization,cell line studies and in vivo efficacy in schizophrenia

Objective: The aim of the present investigation was to investigate the efficacy of solid lipid nanoparticles (SLNs) to enhance the absorption and bioavailability of lurasidone hydrochloride (LH) following oral administration.

Methods: The LH loaded SLNs (LH-SLNs) were prepared by high pressure homogenization (HPH) method, optimized using box Behnken design and evaluated for particle size (PS), entrapment efficiency (EE), morphology, FTIR, DSC, XRD, in vitro release, ex vivo permeation, transport studies across Caco-2 cell line and in vivo pharmacokinetic and pharmacodynamic studies.

Results: The LH-SLNs had PS of 139.8?±?5.5?nm, EE of 79.10?±?2.50% and zeta potential of ?30.8?±?3.5?mV. TEM images showed that LH-SLNs had a uniform size distribution and spherical shape. The in vitro release from LH-SLNs followed the Higuchi model. The ex vivo permeability study demonstrated enhanced drug permeation from LH-SLNs (>90%) through rat intestine as compared to LH-suspension. The SLNs were found to be taken up by energy dependent, endocytic mechanism which was mediated by clathrin/caveolae-mediated endocytosis across Caco-2 cell line. The pharmacokinetic results showed that oral bioavailability of LH was improved over 5.16-fold after incorporation into SLNs as compared to LH-suspension. The pharmacodynamic study proved the antipsychotic potential of LH-SLNs in the treatment of schizophrenia.

Conclusion: It was concluded that oral administration of LH-SLNs in rats improved the bioavailability of LH via lymphatic uptake along with improved therapeutic effect in MK-801 induced schizophrenia model in rats.     

Preparation and dielectric properties of fullerene-doped polyarylene ether nitrile film

In order to obtain polymer films with low dielectric constant (≤2.0) and enhanced mechanical strength, fullerene-doped polyarylene ether nitrile (PEN) film was designed and prepared according to the following step. At first, fullerene and PEN were dissolved in toluene and N-methyl pyrrolidone, respectively, and the solutions were mixed together. The films were prepared by solution casting/solvent evaporation method on glass sheet. The morphology and thermal analysis of the films were characterized by visual & SEM observation and DSC & TGA test, respectively. The mechanical properties and dielectric properties of the films were also measured. The results showed that the dispersion of fullerene was largely dependent on the evaporation methods of the solvents. The glass transition temperature (Tg) and thermal decomposition temperature (Td) of PEN films were improved with the addition of fullerene. The dielectric constant sharply decreased from 4.0 to about 2.0 with the addition of fullerene. At the same time, the mechanical properties were improved, which might be caused by the physical entanglement of PEN chains with fullerenes. The lowest ε value (1.75 at 1 MHz) and the highest tensile strength (142.2 Mpa) were simultaneously obtained in samples containing 3 wt% fullerenes, which indicated it’s the optimal content of fullerene.     

Design and evaluation of dental films of PEGylated rosin derivatives containing sparfloxacin for periodontitis

Objective: In this study, PEGylated rosin derivatives (PRDs) namely D1 and D2 were synthesized and evaluated for their application to produce sustained-release antibacterial films containing sparfloxacin for periodontitis.

Significance: PRDs are biodegradable and biocompatible, and therefore sustained-release dental implant of PRD-sparfloxacin can provide an effectual treatment for periodontitis.

Methods: Films were produced by solvent casting technique and characterized for morphology, swelling-index, in vitro degradation and drug release kinetics. The impact of type of PRD, concentration of PRDs, and addition of plasticizer (dibutyl phthalate) on various film properties was evaluated. The films were also subjected to stability study at 30?°C and 40?°C for 90?days.

Results: Both D1 and D2 produced smooth and non-porous films with sparfloxacin. The D1 films, due to lower amount of polyethylene glycol 400 in D1, exhibited lower swelling-index, slower degradation, and slower drug release compared to D2 films. An increase in PRDs concentration decreased swelling-index, prolonged degradation time, and decreased drug release rate of films; addition of plasticizer showed the similar effect. At pH 7.6, D1 and D2 films showed complete degradation at the end of 58 and 51?days, respectively. At the end of 21?days, D1 and D2 films released 41.85% and 61.53% sparfloxacin, respectively. The drug release from D1 films followed Higuchi square-root kinetics, while D2 films released drug by the zero order kinetics. The stability conditions did not significantly alter PRDs-film properties.

Conclusion: Results revealed that PRDs can be used successfully to produce sustained-release antibacterial films containing sparfloxacin for the treatment of periodontitis.     

Ultra-drawing of polystyrene by solid-state coextrusions: molecular weight dependence of properties and processing

Solid-state coextrusion within polyethylene at 130° C has been shown to produce ultra-drawn polystyrene (PS). Six molecular weights of atactic PS of narrow molecular weight range were ultra-drawn. A strong influence of molecular weight and extrusion draw radio (EDR) on the efficiency of coextrusion was observed. The highest EDR of 27 and orientation achieved exceed values so far reported in the literature for PS. Bi-refringence reached _n =–4.2×10^–2, corresponding to 44% orientation, and the efficiency of chain extension as measured by elastic recovery was almost 100 %. The results are consistent with an entanglement deformation model for PS which facilitates molecular extension and concomitant orientation. Draw deformation of markers placed on the PS films prior to co-extrusion indicate the process is an effective elongational flow. The glass transition temperature and molecular weight did not change following draw.     

CO-DEPOSITION OF FULLERENES AND SULFUR FROM DILUTED SOLUTION

ABSTRACT

A new method to synthesize fullerene and sulfur compounds has been developed. Using this method, C₆₀S₁₆ and C₇₀S₁₆ compounds were grown from dilute fullerene and sulfur toluene solution. Their atomic structures were analyzed by x-ray diffraction with the single crystal. The C₆₀S₁₆ crystal is C-centered monoclinic structure of a=2.0874?nm, b=2.1139?nm, c=1.05690?nm and β=111.93°, and the C₇₀S₁₆ has a primitive monoclinic, P2₁/c, with lattice parameters of a=1.5271?nm, b=1.49971?nm, c=2.18024?nm and β=109.791°. In this compound, the structure of fullerenes is maintained and sulfur atoms form S₈ rings placed around the fullerenes.     

Catalytic activity of hybrid platinum nanoparticle-[C60]fullerene nanowhisker composites for 4-nitrophenol reduction

Abstract

Composites comprising platinum nanoparticles loaded on [C₆₀]fullerene nanowhiskers were prepared by a liquid-liquid interfacial precipitation method. The synthesized platinum nanoparticle-[C₆₀]fullerene nanowhisker composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The catalytic activity of the platinum nanoparticle-[C₆₀]fullerene nanowhisker composites was confirmed for the reduction of 4-nitrophenol by UV–vis spectroscopy. The reduction of 4-nitrophenol catalyzed by the platinum nanoparticle-[C₆₀]fullerene nanowhisker composites followed the pseudo-first-order reaction rate law.     

Rare-Gas Implantation and Damage of Fullerene at High Fluence

Abstract

100 keV Ar⁺and Kr⁺ ions were implanted into fullerene films up to fluences which exceed the fullerene destruction threshold. The depth profiles of implanted atoms were measured using conventional RBS techniques. The depth profile parameters differ significantly from theoretical estimates and with increasing ion fluence the depth profiles move to the sample surface. This suggests a high degree of fullerene sputtering. In annealing experiments at temperatures up to 375 °C no significant changes of the depth profiles were observed.     

Comparative analysis of two methods for synthesis of fullerenes at different helium pressures

Abstract

The results of the effect of helium pressure in the chamber on the amount and composition of the produced fullerenes (C₆₀, C₇₀, etc.) synthesized in the arc plasma with graphite electrodes are presented. The findings obtained when the arc is powered by a direct (DC) and alternating (AC) currents of low frequency were compared in the same chamber with the electrodes located at the same angle to each other. These two methods are drastically different. The complete conversion of graphite into fullerene soot in AC occurs, but a part of the graphite is converted into a cathode deposit that does not contain fullerenes in DC, the relative amount of which increases when decreasing the helium pressure in the chamber. The highest fullerene content in fullerene soot of 10.2?wt.% is produced at a pressure of 127.5?kPa in AC arc, but in DC arc, the highest content of fullerenes in fullerene soot of 8.3?wt.% is produced at a pressure of 33.3?kPa.     

Surface glass transition temperatures of monodisperse polystyrene films by scanning force microscopy

Surface molecular motion of monodisperse polystyrene (PS) films was examined by scanning viscoelasticity microscopy (SVM) in conjunction with lateral force microscopy (LFM). The dynamic storage modulus, ?, and loss tangent, tan d , at a PS film surface with a smaller number-average molecular weight, M_n, than 40k were found to be smaller and larger than those for the bulk sample even at room temperature, meaning that the PS surface is in a glass–rubber transition state or a fully rubbery one at this temperature if the M_n, is small. In order to elucidate quantitatively how vigorous the molecular motion at the PS surface is, SVM and LFM measurements were made at various temperatures. The glass transition temperature, T_g, at the surface wasdiscerned to be markedly lower than its bulk T_g, and the discrepancy of T_g between surface and bulk becomes larger with the decreasing M_n. Such an intensive activation of thermal molecular motion at the PS surfaces can be explained in terms of an excess free volume in the vicinit of the film surfaceinduced by the preferential segregation of chain end groups.