Model Systems for Evidencing the Mediator Role of Riboflavin in the UVA Cross-Linking Treatment of Keratoconus

Riboflavin under UVA radiation generates reactive oxygen species (ROS) that can induce various changes in biological systems. Under controlled conditions, these processes can be used in some treatments for ocular or dermal diseases. For instance, corneal cross-linking (CXL) treatment of keratoconus involves UVA irradiation combined with riboflavin aiming to induce the formation of new collagen fibrils in cornea. To reduce the damaging effect of ROS formed in the presence of riboflavin and UVA, the CXL treatment is performed with the addition of polysaccharides (dextran). Hyaluronic acid is a polysaccharide that can be found in the aqueous layer of the tear film. In many cases, keratoconus patients also present dry eye syndrome that can be reduced by the application of topical solutions containing hyaluronic acid. This study presents physico-chemical evidence on the effect of riboflavin on collagen fibril formation revealed by the following methods: differential scanning microcalorimetry, rheology, and STEM images. The collagen used was extracted from calf skin that contains type I collagen similar to that found in the eye. Spin trapping experiments on collagen/hyaluronic acid/riboflavin solutions evidenced the formation of ROS species by electron paramagnetic resonance measurements.     

Ma?analytische Bestimmung von Blei-Ion als unl?sliche Bleiverbindung unter Benutzung von Diphenylcarbazon als Indikator

Ohne Zusammenfassung     

Fluorescence lifetime imaging in biosciences: technologies and applications

The biosciences require the development of methods that allow a non-invasive and rapid investigation of biological systems. In this aspect, high-end imaging techniques allow intravital microscopy in real-time, providing information on a molecular basis. Far-field fluorescence imaging techniques are some of the most adequate methods for such investigations. However, there are great differences between the common fluorescence imaging techniques, i.e., wide-field, confocal one-photon and two-photon microscopy, as far as their applicability in diverse bioscientific research areas is concerned. In the first part of this work, we briefly compare these techniques. Standard methods used in the biosciences, i.e., steady-state techniques based on the analysis of the total fluorescence signal originating from the sample, can successfully be employed in the study of cell, tissue and organ morphology as well as in monitoring the macroscopic tissue function. However, they are mostly inadequate for the quantitative investigation of the cellular function at the molecular level. The intrinsic disadvantages of steady-state techniques are countered by using time-resolved techniques. Among these fluorescence lifetime imaging (FLIM) is currently the most common. Different FLIM principles as well as applications of particular relevance for the biosciences, especially for fast intravital studies are discussed in this work.      

Synthesis and Stereochemistry of Some New 1,3-Oxathiane Derivatives

Summary. The synthesis and stereochemistry of some new 2,5-substituted 1,3-oxathiane derivatives are reported. The anancomeric or flexible structure of the derivatives and some peculiar cases of prochirality are revealed by NMR investigations.     

Core–shell hybrid material for ZnO nanorods generation

The aim of our study consisted in obtaining ZnO nanorods using a photonic crystal (PC) structure as substrate. For obtaining of such structures, a PC presenting with electroconductive properties was chosen. Thus, the first step was represented by the synthesis of a copper nanoparticles shell composed by a maximum of seven layers of inorganic particle. This core–shell structure was subsequently used for the generation of ZnO nanorods by electrochemical deposition. The obtained materials were characterized by SEM, dynamic light scattering, UV–Vis, and X-ray powder diffraction analysis.     

Hybrid polymeric latexes containing magnetite

The work describes a study for preparing polystyrene (PSt) and polymethyl methacrylate (PMMA) latex, containing magnetite (Fe₃O₄), covalently bounded to the polymeric chains. The magnetite was functionalized with various alkoxysilanes containing double bonds: vinyltriethoxysilane (VTES), methacryloyl propyl trimethoxysilane (MPTS) and vinyldimethylethoxysilane (VMe₂TES). The ferrite-silane composite forms higher average size particles with MPTS than with VTES. Ferrite functionalized with VMe₂TES forms stable latexes with both PSt and PMMA polymers. PSt forms also stable latexes with ferrite functionalized with VTES but unstable with ferrite functionalized with MPTS.     

Occurrence of organochlorine pesticides and polychlorinated biphenyls in soils and sediments from Eastern Romania

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), such as DDT and analogues, hexachlorocyclohexane (HCH) isomers and hexachlorobenzene (HCB), were measured in surface soils and sediments from Eastern Romania. Thirty-nine soil samples from the forested zone, eight soil samples from a municipal waste-disposal site, and 10 sediment samples from the Bahlui River along the Iassy city were analysed using accelerated solvent extraction (ASE) and gas chromatography coupled to electron capture detection or mass spectrometry. The low mean concentrations of OCPs (11–31 and 22–84?ng?g^?1 for HCHs and DDTs, respectively) and PCBs (8–43?ng?g^?1) in soil samples from the forested zone suggest that contamination at most of these sites occurred predominantly through atmospheric transport from zones where these compounds were used and subsequently through atmospheric deposition. Contrarily, soil samples collected in the vicinity of a waste-disposal site near Iassy contained higher mean levels of PCBs (278?ng?g^?1, range 34–1132?ng?g^?1) than OCPs (6 and 101?ng?g^?1 of soil for HCHs and DDTs, respectively). The sediment samples collected along the Bahlui river throughout the Iassy city revealed higher mean levels of PCBs (59?ng?g^?1, range 24–158?ng?g^?1) compared with OCP levels (2 and 37?ng?g^?1 of soil for HCHs and DDTs, respectively). Furthermore, PCB profiles and concentrations in the sediment samples varied considerably along the river due to a wide variety of sources, such as different industries and waste sites. Although their sources are difficult to evaluate, the presence of POPs at most sites (especially at the waste-disposal site) may constitute a potential health hazard.     

Tail Conditional Expectation for the Multivariate Pareto Distribution of the Second Kind: Another Approach

In risk analysis, the Tail Conditional Expectation (TCE) describes the expected amount of risk that can be experienced given that the risk exceeds a threshold value. Thus, TCE provides an important measure of the right-tail risk. In this paper, we present TCE formulas for the multivariate Pareto distribution of the second kind. Because of the complex form of this distribution, the formulas for the n-variate case are expressed recursively, in terms of the (n ? 1)-variate case.     

Photostability enhancement by encapsulation of α-tocopherol into lipid-based nanoparticles loaded with a UV filter

The aim of this study was to develop some sunscreen formulations able to maintain their photoprotection when exposed to UV radiation. In this context, the influence of the antioxidant α-tocopherol on the photostability of lipid-based nanoparticles, namely solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs), encapsulated with a UVA filter, has been investigated. The nanoparticles co-encapsulated with both actives exhibited dimensions smaller than 200 nm and zeta potentials of –45 mV. The photoprotection of the creams based on lipid nanoparticles was evaluated in terms of two protection factors, SPF and erythemal UVA–PF. By exposing the creams to UV radiation, it was observed that tocopherol results in obtaining quite stable formulations, but it does not improve the overall photoprotection much. However, by adding the antioxidant to the formulation confers a double action: protection of the skin against reactive oxygen species and the photostabilization of the UVA filter into lipid nanoparticles.