•Alfa, beta unsaturated grafted-hyaluronan suitable for cross-linking was prepared.•Degree of acrylation up to 35% was reached by a methodology using mixed anhydrides.•Highly reproducible reactions ...produce highly pure derivatives (up to 200g/batch).•Cross-linked nanofiber mats (scaffolds) formed a hydrogel with porous honeycomb structure.
In this work, hyaluronan (HA) was grafted by a novel and an efficient mixed anhydrides methodology with (hetero)-aryl and aliphatic acrylic moieties suitable for cross-linking. A precise control of stoichiometry was achieved. Derivatives with degree of substitution (DS) below 20% did not show self-crosslinking. Due to mild reaction conditions, a negligible degradation of the polysaccharide was obtained. The influence of the feed components on the reaction efficiency and DS were studied up to 200g/batch. The structure of the modified HA was characterized by Infrared Spectroscopy, Nuclear Magnetic Resonance, SEC-MALS and chromatographic analyses. Enzymatic degradation of derivatives was performed and isolated dimers demonstrated to be non-cytotoxic. The feasibility of the grafted HA for electrospinning with subsequent photo-crosslinking to avoid nanofibers water dissolution was demonstrated. The biocompatibility of the material, its degradation products, and the formation of honeycomb porous structures also proved the potential of the material for future in vivo applications.
•The series of photocurable HYA was prepared under mild reaction conditions.•Photocurable HYA was processed to a microfibrous structure by a wet-spinning method.•Water solubility of HYA microfibres ...was reduced by the solid-state photocrosslinking.•The nature of a polymer structure had a great impact to a final crosslink ratio.•We examined changes in mechanical properties of the particular fibres.
Hyaluronan (HA) was chemically modified to a photocurable derivative by the acylation with a mixed anhydride of trans-cinnamic acid and characterized by UV, IR and 2D NMR spectroscopy. Photocurable HA was processed to a microfibrous structure by wet-spinning technology. Water solubility of otherwise water-soluble HA microfibres was reduced significantly by the solid-state photocrosslinking. We also investigated that the nature of polymer structure had a great impact to a final crosslink ratio. The analysis of the mechanical properties showed higher ultimate tensile strength and increased rigidity of the photocrosslinked fibres in comparison to the untreated ones. Moreover all tested materials are regarded as biocompatible according to the tests of cell viability, phototoxicity and enzymatic degradability, which make them suitable candidates for numerous biomedical applications.
Stress-induced fibroblast senescence is thought to contribute to skin aging. Ultraviolet light (UV) radiation is the most potent environmental risk factor in these processes. An Epilobium ...angustifolium (EA) extract was evaluated for its capacity to reverse the senescent response of normal human dermal fibroblasts (NHDF) in vitro and to exhibit skin photo-protection in vivo. The HPLC-UV-MS analysis of the EA preparation identified three major polyphenol groups: tannins (oenothein B), phenolic acids (gallic and chlorogenic acids) and flavonoids. EA extract increased the cell viability of senescent NHDF induced by serum deprivation. It diminished connective tissue growth factor and fibronectin gene expressions in senescent NHDF. Down-regulation of the UV-induced release of both matrix metalloproteinase-1 and -3 and the tissue inhibitor of matrix metalloproteinases-1 and -2, and also down-regulation of the gene expression of hyaluronidase 2 were observed in repeatedly UV-irradiated NHDF after EA extract treatment. Interestingly, EA extract diminished the down-regulation of sirtuin 1 dampened by UV-irradiation. The application of EA extract using a sub-irritating dose protected skin against UV-induced erythema formation in vivo. In summary, EA extract diminished stress-induced effects on NHDF, particularly on connective tissue growth factor, fibronectin and matrix metalloproteinases. These results collectively suggest that EA extract may possess anti-aging properties and that the EA polyphenols might account for these benefits.
•A new derivative of hyaluronic acid — α,β-unsaturated aldehyde.•Optimization of the reaction parameters — two possible strategies and possible reaction mechanisms were described and discussed.•In ...vitro test showed suitable biocompatibility of the new material.•pH-Responsive conjugation of α,β-unsaturated aldehyde with various amines — imine bond stabilized by adjacent CC double bond.•Efficient crosslink of α,β-unsaturated aldehyde with poly-amino linker under physiological conditions — formation of hydrogels.•Comparison of mechanical properties of hydrogels prepared from α,β-unsaturated HA-aldehyde with its saturated analogue.•A promising material for drug delivery (suitable pH-responsibility) and tissue engineering (improved mechanical properties).
Hyaluronic acid (HA) modified with an aldehyde group (HA-CHO or HA-aldehyde) has been extensively used for various biomedical applications. The main advantage of the aldehyde moieties is the ability to react with a wide range of amino compounds under physiological conditions. Reactions of aldehydes with primary amines in water are reversible and equilibrium is thoroughly shifted towards starting aldehyde and amine. This work presents an unique modification of HA: α,β-unsaturated aldehyde of HA (4,5-anhydro-6(GlcNAc)-oxo HA or ΔHA-CHO), which allows the primary amines to be attached to HA more effectively in comparison to the saturated HA-CHO. Higher hydrolytic stability is caused by the conjugation of imine with an adjacent CC double bond. Two strategies for the preparation of unsaturated HA-aldehyde were developed and chemical structures were studied in details. Cross-linked materials prepared from this precursor are biocompatible and suitable for applications in drug delivery and regenerative medicine.
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► Hyaluronan polyaldehyde was prepared by two simple methods. ► Maximum degree of substitutions were 15% or 50% depending on used method (TEMPO/NaOCl or Dess–Martin periodinane). ► ...Eight parameters of reaction process were studied and optimized. ► Prepared derivatives are biocompatible, nontoxic, and showed enormous potential in tissue engineering and pharmacy.
Native hyaluronan (HA) has been oxidized to polyaldehyde polymers with a degree of substitution (DS) of up to 50%. Two different procedures enabling the control of the degree of substitution were followed in this study. Selective oxidation of primary hydroxyl groups of N-acetyl-d-glucosamine of hyaluronan was performed either in an aqueous solution containing AcNH-TEMPO/NaBr/NaOCl or in an aprotic solvent containing Dess–Martin periodinane (DMP). It was found that a change of reaction parameters (reaction time and temperature, type of catalyst, oxidant-to-HA ratio, presence of nitrogen, buffer type, and concentration) had an influence on the degree of substitution and molecular weight. The derivatives were characterized by MS, NMR spectroscopy, and SEC-MALLS. Degradation of hyaluronic acid by the oxidant was observed and confirmed by SEC. The effect of oxidized derivatives of hyaluronan on cells was studied by means of NIH 3T3 fibroblast viability, which indicates that prepared hyaluronan polyaldehydes are biocompatible and suitable for medical applications and tissue engineering. The function of polyaldehyde as precursor for other modification was illustrated in the reaction with lysine.
Stable carbon and oxygen isotope values (δ13C, δ18O) of structural carbonate were determined in the bioapatite component of fossil teeth from the Czech Republic, Slovakia and Hungary. Oxygen isotope ...compositions of enamel and dentin samples provide new quantitative records of the Late Pleistocene climate in East Central Europe (ECE). These δ18O data were combined with records of oxygen isotope values of recent and paleogroundwaters to study the spatial patterns and temporal variations in the oxygen isotope composition of precipitation and the thermal climate over ECE. The new isotopic data suggest that surface air temperatures in the study region between 33 and 12 ka were 2–9 °C colder than present. Specimens of woolly mammoth, rhino and horse from the Late Pleistocene were primarily C3 grazers.
Skin exposure to ultraviolet (UV) light evokes a complex stress response in keratinocytes. Keratin filament organization provides structural stability and mechanical integrity of keratinocytes. ...Involucrin is a transglutaminase substrate protein contributing to the formation of insoluble cornified envelopes. However, a more complex role for keratins and involucrin has been proposed, including the regulation of cell stress response. The aim was to evaluate modulations of keratin 1, 10 and involucrin expression in HaCaT in the light of the complex response of these cells to UV-B radiation, including effects on c-Jun and matrix metalloproteinase 1 (MMP-1) gene expression and production of interleukin (IL) 6 and 8. A UV-B (300±5 nm) dose of 10 mJ/cm2 was selected since this dose resulted in a partial decrease in cell viability in contrast to higher UV-B doses, which induced complete cell death 48 h after treatment. The UV-B radiation induced significant expression of keratin 1 and 10 and decreased expression of involucrin. This was accompanied by increased expression of c-Jun and MMP-1 and IL-6 and IL-8 production. The data suggest that the expression of keratin 1, 10 and involucrin is modulated in HaCaT keratinocytes as a part of the complex stress response to UV radiation
Trenčianske Bohuslavice-Pod Tureckom is one of the most important Gravettian open-air sites in the Slovak Republic. It is situated in Western Slovakia, in the middle course of the Váh River, in the ...area with abundant Upper Palaeolithic settlement. Systematic archaeological research was conducted by Juraj Bárta in 1981–1986, when 478 m2 of the site was investigated. A small (2 m2) amount of revisory research conducted in 2008 had an interdisciplinary character, including detailed sedimentological, stable isotope, seasonality, fired clay pellets, lithic raw materials, pollen and malacofaunal analyses. Stable isotope analyses were used for the first time in Palaeolithic research in Slovakia. Three Gravettian occupational levels in superposition were discovered at depths of 25–35 cm (layer I – ∼27 ka), 55–75 cm (layer II – ∼28 ka) and of 85–125 cm (layer III – 29.5 ka). The results of most analyses were similar to those obtained from other Gravettian sites in the Middle Danube region. The analyses of sediment and malacofauna indicated cooling in the studied time intervals, Stable isotope analyses indicated the mosaic character of the Gravettian palaeoenvironment. Floral and faunal analyses agreed well with the dates of all three cultural layers, which represent rather colder stadial than warmer interstadial conditions.
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