Transdermal Delivery Systems for Ibuprofen and Ibuprofen Modified with Amino Acids Alkyl Esters Based on Bacterial Cellulose

The potential of bacterial cellulose as a carrier for the transport of ibuprofen (a typical example of non-steroidal anti-inflammatory drugs) through the skin was investigated. Ibuprofen and its amino acid ester salts-loaded BC membranes were prepared through a simple methodology and characterized in terms of structure and morphology. Two salts of amino acid isopropyl esters were used in the research, namely L-valine isopropyl ester ibuprofenate ([ValOiPr][IBU]) and L-leucine isopropyl ester ibuprofenate ([LeuOiPr][IBU]). [LeuOiPr][IBU] is a new compound; therefore, it has been fully characterized and its identity confirmed. For all membranes obtained the surface morphology, tensile mechanical properties, active compound dissolution assays, and permeation and skin accumulation studies of API (active pharmaceutical ingredient) were determined. The obtained membranes were very homogeneous. In vitro diffusion studies with Franz cells were conducted using pig epidermal membranes, and showed that the incorporation of ibuprofen in BC membranes provided lower permeation rates to those obtained with amino acids ester salts of ibuprofen. This release profile together with the ease of application and the simple preparation and assembly of the drug-loaded membranes indicates the enormous potentialities of using BC membranes for transdermal application of ibuprofen in the form of amino acid ester salts.     

Scaling of activation energy for macroscopic flow in poly(ethylene glycol) solutions: Entangled – Non-entangled crossover

We postulate an empirical scaling equation, which accurately describes flow of polymer solutions, complimenting the paradigm of length-scale-dependent viscosity. We investigated poly(ethylene glycol) aqueous solutions and observed an exponential dependence of viscosity on the hydrodynamic radius of a single coil R_h divided by the correlation length ξ. Properties of the system changed abruptly with the onset of chain entanglement at concentration corresponding to ξ = R_h. We propose a single equation valid for all the investigated systems, analyze the physical meaning of parameters appearing therein and discuss the impact of chain entanglement. Viscous flow is treated as an activated process, following the Eyring rate theory. We show that the difference of activation energy for flow between pure solvent and polymer solution, ΔE_a, is a function of concentration, whose derivative has a discontinuity at the crossover concentration. For dilute PEG solutions ΔE_a takes values of up to several kJ/mol and is proportional to the intrinsic viscosity. We successfully apply the scaling approach to the diffusive motion of a protein (aldolase) in solutions of 25 kg/mol PEO (concentrations of 2–20%), investigated by fluorescence correlation spectroscopy (FCS). A significant difference in the influence of crowding on translational and rotational motion of the protein is revealed.     

Nanofabricated atom optics: Atom chips

Abstract

Small tight trapping and guiding potentials can be created for neutral atoms moving microns above surfaces patterned with nanofabricated charged and current-carrying structures. Surfaces holding such structures form atom chips which, for coherent matter wave optics, may form the basis for a variety of novel applications and research tools, similar to integrated circuits in electronics. In this paper we describe the basic principles of atom chip experiments.     

Identification and Structural Aspects of G-Quadruplex-Forming Sequences from the Influenza A Virus Genome

Influenza A virus (IAV) causes seasonal epidemics and sporadic pandemics, therefore is an important research subject for scientists around the world. Despite the high variability of its genome, the structure of viral RNA (vRNA) possesses features that remain constant between strains and are biologically important for virus replication. Therefore, conserved structural motifs of vRNA can represent a novel therapeutic target. Here, we focused on the presence of G-rich sequences within the influenza A/California/07/2009(H1N1) genome and their ability to form RNA G-quadruplex structures (G4s). We identified 12 potential quadruplex-forming sequences (PQS) and determined their conservation among the IAV strains using bioinformatics tools. Then we examined the propensity of PQS to fold into G4s by various biophysical methods. Our results revealed that six PQS oligomers could form RNA G-quadruplexes. However, three of them were confirmed to adopt G4 structures by all utilized methods. Moreover, we showed that these PQS motifs are present within segments encoding polymerase complex proteins indicating their possible role in the virus biology.     

Changing Frames of Mobility through Radical Policy Interventions? The Stockholm Congestion Tax

The introduction of a congestion tax was a significant moment in the management of mobility in Stockholm. This paper critically examines this apparent consensus on confronting car based mobility, by analysing how mobility was framed at key stages in policy making, from the 1970s through to the trial in 2006 and subsequent implementation. Changing transport objectives are compared, and winners and losers are traced in relation to motility and environmental quality. The paper argues that a car-based automobility frame survives, even in the implementation of a radical policy of congestion taxation.     

6‐Pyridinium benzo[a]phenazine‐5‐oxide derivatives as visible photosensitisers for polymerisation

Several 6‐pyridinium benzo[a]phenazine‐5‐oxide derivatives have been synthesised and characterised by proton nuclear magnetic resonance spectroscopy and mass spectrometry. The spectroscopic and electrochemical properties of these dyes were examined. The dyes were used as reducible sensitisers for selected electron donors (phenylthioacetic acid, phenoxyacetic acid, N‐phenylglycine, and ethyl 4‐N,N‐dimethylaminobenzoate) and as oxidisable sensitisers for electron acceptors (onium and N‐alkoxypyridinium salts). These photoredox pairs were found to be effective visible‐wavelength photoinitiators for the free radical polymerisation of trimethylolpropane triacrylate under visible light. The cationic photopolymerisation of cyclohexene oxide by the studied dyes and the onium salt photoredox pairs was ineffective. The obtained results are discussed on the basis of both free energy change for electron transfer to or from the benzo[a]phenazine dyes and the photochemical properties of the dyes, particularly their photobleaching. The proposed mechanism of dye fading is supported by density functional theory calculations and spectroscopic characterisation of the radical cation of the dye.     

Mechanical Properties of a Lithium Disilicate Strengthened Lithium Aluminosilicate Glass‐Ceramic

A glass composition in the Li₂O–Al₂O₃–SiO₂ (LAS)‐ternary phase diagram is presented, which enables the crystallization of Li₂Si₂O₅ as well as LiAlSi₂O₆ upon a well‐defined heat treatment. Li₂Si₂O₅ is the minor crystalline phase in the glass‐ceramic and generates through the bulk strengthening of the LAS glass‐ceramic. A flexural strength as higher as 400 MPa is measured in the proposed glass‐ceramic formulation, thus outperforming conventional LAS‐glass‐ceramics. A combination of the presence of those two crystalline phases of very different mechanical properties and coefficient of thermal expansion as well as the microstructure are believed to contribute largely to the enhancement of the measured properties.     

Nanocrystal shape and the mechanism of exciton spin relaxation

The rate of exciton spin relaxation (flips) between the bright exciton states (F = +/-1) of CdSe nanocrystals is reported as a function of shape, for dots and nanorods. The spin relaxation is measured using an ultrafast transient grating method with a crossed linearly polarization sequence. It is found that the spin relaxation rate depends on the radius, not length, of the nanocrystals. That observation is explained by deriving an expression for the electronic coupling matrix element that mixes the bright exciton states.     

In situ observations of microscale damage evolution in unidirectional natural fibre composites

Synchrotron X-ray tomographic microscopy (XTM) has been used to observe in situ damage evolution in unidirectional flax fibre yarn/polypropylene composites loaded in uniaxial tension at stress levels between 20% and 95% of the ultimate failure stress. XTM allows for 3D visualization of the internal damage state at each stress level. The overall aim of the study is to gain a better understanding of the damage mechanisms in natural fibre composites. This is necessary if they are to be optimized to fulfil their promising potential. Three dominating damage mechanisms have been identified: (i) interface splitting cracks typically seen at the interfaces of bundles of unseparated fibres, (ii) matrix shear cracks, and (iii) fibre failures typically seen at fibre defects. Based on the findings in the present study, well separated fibres with a low number of defects are recommended for composite reinforcements.