Liquid Crystalline Microenvironments For Tissue Engineering

In this present work, gels with liquid crystalline (LC) phases were studied based on cellulose and collagen. The cellulose was further incorporated in a polymer matrix (polyvinyl alcohol) and in a biocompatible material (glycerol), in order to produce gels with LC phases. The LC phases and other properties of the gels were further investigated in order to determine relationships between structure/properties. Preliminary cellular studies were done to unravel the influence of the LC phase in cell proliferation and the changes in the LC phase due to the presence of the cells. Nanocrystalline cellulose (NCC) with different aspect ratio, were obtained by acid hydrolysis with sulfuric acid at different reaction times. Gelation of collagen type I was not achieved. The NCC/PVA gels did not presented LC patterns. NCC/glycerol gels with NCC concentration higher than 7% (w/w) showed, through polarized optical microscopy, a fingerprint texture characteristic of the chiral nematic ordering of the NCC. The pitch of LC phase, increase with the NCC length and no significant variations were observed in gels with higher NCC content. For cell culture studies the 7% (w/w) NCC concentration was selected and the pH of the gels was increased by incubation with culture medium and an increase in the pitch size was noticed. A negative zeta potential of the gels was observed even after pH increase. No chemically modifications were observed by ATR-FTIR after increasing the gels’ pH. Preliminary rheological studies gave a good indication of the materials’ viscoelastic properties and its thixotropic behaviour. Exploratory cellular tests showed low cell adhesion and cytotoxic tests led to conclude that 48 hours of incubation with culture medium is needed before any cellular studies. This study shown that the NCC/glycerol gel is a promising material to use in tissue engineering applications

Rheology and Shear-Induced Textures of Silver Nanowire Lyotropic Liquid Crystals

We report the rheological and microstructural shear response of a mixture of polyvinylpyrrolidone (PVP) coated silver nanowires and nanoparticle aggregates (Ag) dispersed in ethylene glycol (EG) or water (H2O). Biphasic and liquid crystalline dispersions exhibited rheological characteristics similar to those of lyotropic liquid crystalline polymers (LCPs). The viscosity versus concentration curve for Ag-EG dispersions showed a viscosity minimum at a silver concentration between 2.2 vol.% and 2.9 vol.%; this is indicative of the transition to an entirely liquid crystalline phase. The rheology results were consistent with optical microscopy observations that at 2.9 vol.% the sample was entirely birefringent; this is another indication of liquid crystalline phase formation. Shear had a significant effect on the microstructure of the dispersions and dried coatings. Depending on the shear rate, worm or shear banding Structures were observed

A preliminary approach to intelligent x-ray imaging for baggage inspection at airports

Identifying explosives in baggage at airports relies on being able to characterize the materials that make up an X-ray image. If a suspicion is generated during the imaging process (step 1), the image data could be enhanced by adapting the scanning parameters (step 2). This paper addresses the first part of this problem and uses textural signatures to recognize and characterize materials and hence enabling system control. Directional Gabor-type filtering was applied to a series of different X-ray images. Images were processed in such a way as to simulate a line scanning geometry. Based on our experiments with images of industrial standards and our own samples it was found that different materials could be characterized in terms of the frequency range and orientation of the filters. It was also found that the signal strength generated by the filters could be used as an indicator of visibility and optimum imaging conditions predicted

Modification of cell wall properties in lettuce improves shelf life

It is proposed that post-harvest longevity and appearance of salad crops is closely linked to pre-harvest leaf morphology (cell and leaf size) and biophysical structure (leaf strength). Transgenic lettuce plants (Lactuca sativa cv. Valeria) were produced in which the production of the cell wall-modifying enzyme xyloglucan endotransglucosylase/hydrolase (XTH) was down-regulated by antisense inhibition. Independently transformed lines were shown to have multiple members of the LsXTH gene family down-regulated in mature leaves of 6-week-old plants and during the course of shelf life. Consequently, xyloglucan endotransglucosylase (XET) enzyme activity and action were down-regulated in the cell walls of these leaves and it was established that leaf area and fresh weight were decreased while leaf strength was increased in the transgenic lines. Membrane permeability was reduced towards the end of shelf life in the transgenic lines relative to the controls and bacteria were evident inside the leaves of control plants only. Most importantly, an extended shelf-life of transgenic lines was observed relative to the non-transgenic control plants. These data illustrate the potential for engineering cell wall traits for improving quality and longevity of salad crops using either genetic modification directly, or by using markers associated with XTH genes to inform a commercial breeding programme

Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies

X-ray tomography is a well-established technique to characterize 3D structures in material sciences and biology; its magnetic analogue--magnetic X-ray tomography--is yet to be developed. Here we demonstrate the visualization and reconstruction of magnetic domain structures in a 3D curved magnetic thin films with tubular shape by means of full-field soft X-ray microscopies. The 3D arrangement of the magnetization is retrieved from a set of 2D projections by analysing the evolution of the magnetic contrast with varying projection angle. Using reconstruction algorithms to analyse the angular evolution of 2D projections provides quantitative information about domain patterns and magnetic coupling phenomena between windings of azimuthally and radially magnetized tubular objects. The present approach represents a first milestone towards visualizing magnetization textures of 3D curved thin films with virtually arbitrary shape

Iridoviruses of copepods: their identification, estuarine ecology and host histopathology

Zooplankton Invertebrate Iridescent viruses (ZoopIIVs: Iridoviridae) were discovered infecting copepods. Assays were developed for monitoring an infectious ZoopIIV; and the virus ultrastructure and host infection sites were described. The pioneering work has advanced research methods and our knowledge of infectious viruses in the zooplankton that provide critical ecosystem services globall

Quantitative three-dimensional characterization of critical sizes of non-spherical TiO2 nanoparticles by using atomic force microscopy

Since both size and shape of nanoparticles are challenging to be quantitatively measured, traceable 3D measurements are nowadays an issue. 3D nanometrology plays a crucial role to reduce the uncertainty of measurements, improve traceable calibration of samples and implement new approaches, models, and methodologies in the study of the nanomaterials. AFM measurement of nanoparticles with unusual shape represent a non-trivial challenge due to the convolution with the finite size of the tip. In this work, geometric approaches for the determination of critical sizes of TiO2 anatase bipyramids and nanosheets are described. An uncertainty budget is estimated for each nanoparticle size with the aim of assessing the different sources of error to obtain a more reliable and consistent result. The combined standard uncertainties are respectively less than 5% and 10% of the dimensions of bipyramids and nanosheets. Due to the stability and monomodal distribution of their critical sizes, bipyramids and nanosheets are suitable to apply as candidate reference materials at the nanoscale. Moreover, quantitative measurements of shape and texture descriptors are discussed in order to understand the quality of the synthetized batch