Entwicklung von reagenzfrei kovalentes Quervernetzen der chitosan-gelatine Grundgerüste Development of reagent-free covalent crosslinking of chitosan-gelatin scaffolds

Please refer to the attached document. Thank you

One-pot domino synthesis of polyvicinalamine monomers

On a genere de l'imidazole par une reaction de type domino in situ entre le glyoxal, le formaldehyde et deux unites d'ammoniac aqueux. L'addition de bicarbonate aqueux et d'un anhydride carboxylique ou d'un dicarbonate de dialkyle conduit a la formation de la N,N'-diacyl- ou N,N'-dicarbalkoxy-2-hydroxyimidazoline correspondante. Il s'ensuit une reaction de clivage de cycle de Bamberger qui permet d'isoler facilement le cis-1,2-di(acetamido)ethene, le cis-1,2-di(propylamido)ethene, le cis-1,2-di(ethoxyamido)ethene, le cis-1,2-di(tert-butoxyamido)ethene ou le cis-1,2-di(benzamido)ethene sous la forme de solides. La facilite et la generalite offerte par cette approche monotope implique une voie efficace du point de vue des couts en vue de la synthese de routine de precurseurs d'amines oligo- et polyvicinales

Mesoscopic sponge-like topology engineered onto polypropylene promotes retention of bound protein:

The interaction between biopolymers and plastic surfaces defines an area of much interest. In this study, the oxidative activation, surface engineering and protein binding ability of polypropylene derivatives were examined. Figure 1 shows the superimposed carbonyl regions of an ATR-FTIR spectrum of polypropylene, whose surface was subjected to a timecourse oxidation. Oxidation yields increased gradually, affording a maximum signal after 18h. Three distinct carbonyl types were noted. On the basis of spectral data & established reaction chemistries, the oxidation products appeared to be limited to alcohol, ketone, carboxylic acid and potentially ester groups (Pavia et al., 1979). The SEM micrographs of figure 2 showed no significant changes of topology over the first 8h of reaction. In comparison, minor changes had developed by 10h, in the form of sparsely distributed mesoscale bulges. A brief period of dramatic change occurred thereafter, as evidenced by the sponge-like mesoscale topology at 12h. The transformation was noteworthy in that it reflected the release of material stresses, which had accumulated during reaction. When the brevity of this dramatic change was assessed against the continual accumulation of oxidation products, the underlying mechanism pointed to an oxidative phase separation (Hellan, 1984). Further oxidation (14h) did not alter the appearance. Several oxidized surfaces were treated with hydrolyzed aminopropyltriethoxysilane, yielding an aminated surface. Of these, some surfaces were reacted further with ninhydrin, yielding the corresponding aldehyde surface. Interactions between protein and each surface were assessed by the extent to which a trace-labeled fluorescent albumin derivative could be loaded and retained following several washings. A negative control surface, i.e., native polypropylene, did not retain fluorescence after the washings. In contrast, the oxidized, aminated and aldehyde-bearing surfaces retained substantial fluorescence. A related experiment was conducted using mesoscopically flat surfaces to ascertain if the sponge-like topology alone had promoted protein retention. This time, the protein-loaded aminated surfaces lost all fluorescence after the washings. In contrast, oxidized and aldehyde-pendant surfaces still retained fluorescence, presumably by forming imine bonds with protein. Thus, the contribution of a sponge-like topology proved sufficient, yet vital, to achieve retention in the absence of any covalent bonding. Zeolite-related work by Takahashi et al. (2001) gave a physical basis to rationalize protein retention along a sponge-like topology. In this model (Figure 3), surface structures are depicted to be on the order of protein size. Direct entry of protein to the base of a crevice (A) is portrayed as difficult. Instead, protein is envisaged to adsorb at the tips, where wettability is highest (B) and to migrate to the base (C). The better shape complementarity of the base is presumed to stabilize protein-surface interactions, imparting irreversibility to the process in comparison to a flat surface (i.e., scenarios D vs. E). The findings implied that the routine use of reaction-induced phase transformations could aid in the development of alternative mesoscale topologies with refined binding traits. Such chemical approaches should therefore complement established methods based on lithography, self-organization and solvent casting

One pot domino synthesis of polyvicinalamine monomers

On a genere de l'imidazole par une reaction de type domino in situ entre le glyoxal, le formaldehyde et deux unites d'ammoniac aqueux. L'addition de bicarbonate aqueux et d'un anhydride carboxylique ou d'un dicarbonate de dialkyle conduit a la formation de la N,N'-diacyl- ou N,N'-dicarbalkoxy-2-hydroxyimidazoline correspondante. Il s'ensuit une reaction de clivage de cycle de Bamberger qui permet d'isoler facilement le cis-1,2-di(acetamido)ethene, le cis-1,2-di(propylamido)ethene, le cis-1,2-di(ethoxyamido)ethene, le cis-1,2-di(tert-butoxyamido)ethene ou le cis-1,2-di(benzamido)ethene sous la forme de solides. La facilite et la generalite offerte par cette approche monotope implique une voie efficace du point de vue des couts en vue de la synthese de routine de precurseurs d'amines oligo- et polyvicinales

Storage of hydrogen in nanostructured carbon materials

Recent developments focusing on novel hydrogen storage media have helped to benchmark nanostructured carbon materials as one of the ongoing strategic research areas in science and technology. In particular, certain microporous carbon powders, carbon nanomaterials, and specifically carbon nanotubes stand to deliver unparalleled performance as the next generation of base materials for storing hydrogen. Accordingly, the main goal of this report is to overview the challenges, distinguishing traits, and apparent contradictions of carbon-based hydrogen storage technologies and to emphasize recently developed nanostructured carbon materials that show potential to store hydrogen by physisorption and/or chemisorption mechanisms. Specifically touched upon are newer material preparation methods as well as experimental and theoretical attempts to elucidate, improve or predict hydrogen storage capacities, sorption–desorption kinetics, microscopic uptake mechanisms and temperature–pressure–loading interrelations in nanostructured carbons, particularly microporous powders and carbon nanotubes

Bio-liquefaction/solubilization of low-rank Turkish lignites and characterization of the products

The effect of some white-rot fungi on the bio-liquefaction/solubilization of two low-rank Turkish coals and the chemical composition of the liquid products and the microbial mechanisms of coal conversion were investigated. Turkish Elbistan and Beypazari lignites were used in this study. The white-rot fungi received from various laboratories used in the bio-liquefaction/solubilization of the lignites were Pleurotus sajor-caju, Pleurotus sapidus, Pleurotus florida, Pleurotus ostreatus, Phanerochaete chrysosporium, and Coriolus versicolor. FT-IR spectra of raw and treated coal samples were measured, and bio-liquefied/solubilized coal samples were investigated by FT-IR and LC-MS techniques. The Coriolus versicolor fungus was determined to be most effective in bio-liquefying/solubilizing nitric acid-treated Elbistan lignite. In contrast, raw and nitric acid-treated Beypazari lignite seemed to be unaffected by the action of any kind of white-rot fungi. The liquid chromatogram of the water-soluble bio-liquefied/solubilized product contained four major peaks. Corresponding mass spectra of each peak indicated the presence of very complicated structures

Water soluble chitosan derivatives via the freeze concentration technique

Chitosan has been an attractive biopolymer for decades, but its processibility is lowered by its poor solubility, especially in physiological pH values. Freeze concentrated reactions of Chitosan with several organic acids including acrylic, citraconic, itaconic, and maleic acid revealed improved solubility and morphological properties. Solubility traits were assessed with a modified ninhydrin test. Chitosan derivatives were characterized by ATR-FTIR and morphological characteristics were determined by SEM. This study is a unique approach to chemically modify Chitosan to enhance water solubility

3D bioprinting of biomimetic aortic vascular constructs with self-supporting cells

Cardiovascular diseases are the leading cause of deaths throughout the world. Vascular diseases are mostly treated with autografts and blood vessel transplantations. However, traditional grafting methods have several problems including lack of suitable harvest sites, additional surgical costs for harvesting procedure, pain, infection, lack of donors and even no substitutes at all. Recently, tissue engineering and regenerative medicine approaches are used to regenerate damaged or diseased tissues. Most of the tissue engineering investigations have been based on the cell seeding into scaffolds by providing a suitable environment for cell attachment, proliferation and differentiation. Because of the challenges such as difficulties in seeding cells spatially, rejection and inflammation of biomaterials used, the recent tissue engineering studies focus on scaffold-free techniques. In this paper, the development of novel computer aided algorithms and methods are developed for 3D bioprinting of scaffold-free biomimetic macrovascular structures. Computer model mimicking a real human aorta is generated using imaging techniques and the proposed computational algorithms. An optimized three-dimensional bioprinting path planning are developed with the proposed self-supported model. Mouse embryonic fibroblast (MEF) cell aggregates and support structures (hydrogels) are 3D bioprinted layer-by-layer according to the proposed self-supported method to form an aortic tissue construct