We measured the density of vibrational states (DOS) and the specific heat of various glassy and crystalline polymorphs of SiO2. The typical (ambient) glass shows a well-known excess of specific heat ...relative to the typical crystal (α-quartz). This, however, holds when comparing a lower-density glass to a higher-density crystal. For glassy and crystalline polymorphs with matched densities, the DOS of the glass appears as the smoothed counterpart of the DOS of the corresponding crystal; it reveals the same number of the excess states relative to the Debye model, the same number of all states in the low-energy region, and it provides the same specific heat. This shows that glasses have higher specific heat than crystals not due to disorder, but because the typical glass has lower density than the typical crystal.
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•Hydrogels from glycol chitosan were obtained in physiological conditions.•PEG diglycidyl ether was used as the crosslinker.•A purification step is not required after synthesis.•The ...obtained GCS-PEG scaffolds have antibacterial activity.•The GCS-PEG scaffolds stimulate angiogenesis like the positive control VEGF.
We aimed at producing a hydrogel from a chitosan (CS) derivative soluble in physiological conditions to avoid any purification step thus allowing to use the materials also as an in-situ forming material. So, we crosslinked glycol chitosan (GCS) with poly(ethylene glycol) diglycidyl ether (PEGDE) in water at 37 °C. The scaffolds, referred as GCS-PEG, were specifically designed to be used as wound dressing materials as such (after crosslinking) or as in-situ forming materials.
Different amounts of PEGDE were tested. The obtained scaffolds showed macroscopic pores and a tailorable swelling in water by controlling the crosslinking degree. Moreover, GCS-PEG scaffolds displayed a significant antimicrobial activity against Staphylococcus aureus. In-vivo study using the chick embryo choriallantoic membrane resulted in a highly pronounced pro-angiogenic activity suggesting important tissue regeneration properties. Moreover, the employed materials are commercially available, no organic solvents are required and the scaling up is quite predictable.
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•Dopamine (DA) loaded liposomes were coated by Chitosan-glutathione conjugate (CS-GSH).•DA loaded in CS-GSH coated liposomes was protected towards DA autoxidation reaction.•DA was not ...detected on the vesicle surface by XPS studies.
The aim of this work is to evaluate the potential of non-coated-, chitosan-(CS)- or chitosan-glutathione conjugate- (CS-GSH)-coated liposomes to protect the neurotransmitter Dopamine (DA) from the autoxidation reaction in neutral/alkaline conditions. This may be of interest in the development of nanotechnology-based approaches to improve Parkinson’s disease treatment because decreased ROS production and reduced DA associated neurotoxicity are expected. For the mentioned purposes, DA-loaded vesicles were prepared by the Dried Reconstituted Vesicles (DRV) method, and were subsequently coated using solutions of polycations. As for the mean diameters of liposomes so prepared, the CS-GSH coated liposomes showed a significant decrease in size compared to the corresponding non-coated and CS-coated vesicles. The surface charge of DA-loaded non-coated liposomes was −10.8 mV, whereas the CS or CS-GSH coated vesicles showed a slightly positive ζ-potential. The capability of the herein studied vesicles to prevent DA autoxidation was evaluated by visual inspection, monitoring DA/lipid ratio as such and under stressed conditions.
The results suggest that liposome formulations partially protect the neurotransmitter from the autoxidation reaction. In particular, the CS-GSH coated liposomes were more stable than the corresponding CS-coated and non-coated ones against the oxidative damage and were found to deliver the neurotransmitter in a sustained manner. Probably, this is due to the localization of the neurotransmitter in the core of the vesicles as indicated by XPS which confirmed the absence of the neurotransmitter on the surface of these vesicles.
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This paper focuses on the synthesis of innovative functional materials prepared by the polymerization of high internal phase emulsions (HIPEs) for the bioconjugation of active molecules. By applying ...a computational method, this paper demonstrates how to produce materials with tailored features, such as pore dimensions (on the nano–micro scale), swelling in water and organic solvents and bulk densities. To this aim, starting from different emulsion compositions, ten materials are synthesised and fully characterized. Six different outputs ( i.e. swelling in water and THF, mass loss in water and THF, throat and void diameters) are modeled using D-optimal mixture experimental designs. A clear correlation between the applied synthetic conditions and the final properties of the materials is demonstrated. The responses allow the selection of a single material for the development of a bioreactor prototype. Thus, the selected material is loaded into a glass column and polymerized in situ . An in-column procedure is also used for the covalent binding of horseradish peroxidase (HRP) as a model enzyme. A standard substrate is selected to test the activity of the immobilized enzyme. To conclude, the experimental design models allow one to obtain different materials with different features that could find applications in the fields such as biocatalysis/biochromatography, drug delivery or diagnostics. To the best of our knowledge, for the first time, an acrylate based polyHIPE material is used for the binding of enzymes in the active form and successfully applied under flow conditions.
•ω−transamimase was immobilized on epoxy monolithic silica.•The activity of the IMER was studied by an integrated HPLC system.•Optimization of catalytic properties was carried out by a DoE ...approach.•The synthesis of chiral amines of pharmaceutical interest was investigated.
An integrated chromatographic system was developed to rapidly investigate the biocatalytic properties of ω-transaminases useful for the synthesis of chiral amines. ATA-117, an (R)-selective ω-transaminase was selected as a proof of concept. The enzyme was purified and covalently immobilized on an epoxy monolithic silica support to create an immobilized enzyme reactor (IMER). Reactor efficiency was evaluated in the conversion of a model substrate. The IMER was coupled through a switching valve to an achiral analytical column for separation and quantitation of the transamination products. The best conditions of the transaminase-catalyzed bioconversion were optimized by a design of experiments (DoE) approach. The production of (R)-1-(4-methoxyphenyl)propan-2-amine and (R)-1-methyl-3-phenylpropylamine, intermediates for the synthesis of the bronchodilator formoterol and the antihypertensive dilevalol respectively, was achieved in the presence of different amino donors. The enantiomeric excess (ee) was determined off-line by developing a derivatization procedure using Nα-(2,4-dinitro-5-fluorophenyl)-L-alaninamide reagent. The most satisfactory conversion yields were 60% for (R)-1-(4-methoxyphenyl)propan-2-amine and 29% for (R)-1-methyl-3-phenylpropylamine, using isopropylamine as amino donor. The enantiomeric excess of the reactions were 84%R and 99%R, respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Low-temperature specific heat and thermal conductivity measurements have been performed on cesium borate glasses as a function of cesium oxide content. We have found experimental evidence of a ...concurrent growth of specific heat and thermal conductivity with increasing Cs+ content. This finding shows the existence of an uncommon relationship between the peak in C p/T 3 and the plateau in thermal conductivity in glasses and represents the most intriguing result for these alkaline borate glasses. The role of local modes associated with heavy cations on the vibrational dynamics in oxide glasses has been considered. Furthermore, a possible correlation between low-temperature thermal properties and the structure on the nanometer length scale of these glasses is put forward.
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Some lipophilic fluoro-substituted N-benzoyl-2-aminobenzothiazole antibacterial agents have been evaluated for their activity in the presence of cyclodextrins (CDs) containing aqueous ...solutions where CDs are adopted as solubilizing excipients for improving the poor water solubility of these compounds. For such purpose both the natural β-CD and one of FDA/EMA approved CDs for parenteral use (i.e. HP-β-CD) have been employed. The solubility rank order observed was accounted for by thermal analysis (Differential Scanning Calorimetry) and FT–IR spectroscopy. The most promising compound was subjected to further NMR spectroscopic studies and molecular modelling simulations to verify the interactions between the guest molecule and the CD cavity. The assessment of the antibacterial activity of such compounds against selected Gram positive and Gram negative bacterial strains clearly showed that their antimicrobial effectiveness may, quite in all instances, be positively affected by complexation with β-CD and HP-β-CD. These results, which are in some ways in contrast with those already reported in the literature, are herein discussed on the basis of plausible mechanisms. Moreover, this investigation also reveals that the described methodology of complexing both lipophilic and hydrophilic antimicrobial agents with CDs may be an useful approach to enhance their effectiveness as well as a promising strategy to overcome even the microbial resistance problem.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Summary
Inulin (INU) is a polyfructose which have the unique features to not bind plasmatic proteins and to be totally filtered by the kidneys where it is neither secreted nor reabsorbed. These ...behaviors make it an ideal candidate to target and delivery drugs into the kidneys for the therapy of urinary tract affections. On the other side, Vitamin E (VITE) is a hydrophobic molecule with important antioxidant activities. Therefore, the chemical conjugation of INU and VITE, led to amphiphilic INVITE polymers able to self‐assemble in nanostructured micelle.
The obtained micelle have been drug loaded with the model hydrophobic drug curcumin (solubility ≈ 11 ng/ml), the drug release and micelles stability studies have been performed in‐vitro in simulated physiological fluids. Furthermore, biological studies on suitable cell lines have been carried out to assess the cytotoxicity of INVITE conjugates.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The internal friction and the sound velocity in a cesium borate glass (Cs
2O)
0.14(B
2O
3)
0.86 were measured at ultrasonic and hypersonic frequencies by Brillouin scattering measurements over the ...temperature range between 15 and 300
K. The analysis of the experimental results show that, in addition to thermally activated local motions of structural defects, the vibrational anharmonicity contributes substantially to the temperatures dependences of both the hypersonic loss and velocity. It has been also proved that above 150
K the vibrational anharmonicity appears to be governed by the Akhiezer mechanism of phonon viscosity.
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