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Sprayable elastic biopolymer hydrogels for wound healing
Waclawiková, Petra ; Nedomová, Eva (oponent) ; Vojtová, Lucy (vedoucí práce)
The main aim of the presented bachelor thesis is focused on the preparation and characterization of sprayable hydrogels from suitable non-toxic substances, in order to develop gels applicable in wound healing management. The theoretical part deals with general properties of hydrogels, methods of their crosslinking and presents selected natural and synthetic materials used for the preparation of hydrogels. It also contains a brief overview of already prepared sprayable hydrogels, which are not yet commercially used. The experimental part describes the selection and use of readily available non-toxic biomaterials and the measurement of the physico-chemical properties of the prepared gels. Gum Karaya, poly(vinyl alcohol) and sodium alginate were selected as the structural polymers together with different physical crosslinkers and additives. The polymers and additives were subjected to solubility test followed by mixing in certain ratios and crosslinked to form preferably transparent hydrogels. Subsequently their optical and rheological properties were valuated. The measurement of optical properties shows that probably gum Karaya affected increasing in both yellowness as well as transparency. By rheological measuring it was demonstrated, that the higher content of gum Karaya reduces the mechanical resistance of the prepared hydrogels. Hydrogel strength reflects both low and high amount of crosslinker where the optimal amount gave the best result. Therefore, the correct ratio of the used substances is the main parameter for obtaining the most effective hydrogel properties suitable for sprayable hydrogel dressings.
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Novel hydrogels based on polysaccharides for soft tissue regeneration: preparation and characterization
Nedomová, Eva ; Abdellatif, Abdelmohsan (oponent) ; Vojtová, Lucy (vedoucí práce)
Presented diploma thesis deals with preparation, crosslinking and physico-chemical characterization of natural polysaccharide-based hydrogels. The aim of the work was to evolve elastic thin films with potential application for moist wound healing. The theoretical part summarizes the state-of-art about regeneration of soft tissues and their substitutes (synthetic or nature). There are pointed out the basic information about natural polysaccharide gums (chemical structure, solubility, heat and pH stability etc.), its modification and chemical crosslinking. The experimental part is focused on the modification of natural gum Karaya in order to make transparent hydrogels with adjustable hydrolytical stability. Samples were analyzed by FTIR, TGA followed by evaluation of swelling properties and hydrolytical degradation. Based on the results, chemical modification helped to stabilize polysaccharide hydrogels in water up to 25 days which is useful mainly for moist wound healing (e.g. after burns) because of high values of water uptake (from 85 up to 96%).
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Chemical modifications of hydrogels from natural polysaccharide
Poštulková, Hana ; Žídek, Jan (oponent) ; Vojtová, Lucy (vedoucí práce)
Chemical structure, use and chemical and physical properties of natural polysaccharide gum karaya (Sterculia urens) were summarized in theoretical part of this work. The general goal of the diploma work was modification of original insoluble gum karaya under alkali condition to prepare water soluble sample for further applications. Insolubility of gum karaya is caused by presence of acetyl groups and multivalent ions in the structure of polysaccharide. Optimized conditions for modification process were investigated. Sodium, potassium or ammonium hydroxide, 1 minute to 24 hours of treatment and 0.1 - 3% solution of original gum karaya were used for optimizing the modification process. Original (OGK) and modified (MGK) samples were studied by FTIR to investigate chemical composition. Modified samples A2, B1-7, C1-8 and E1-2 were considered as fully deacetylated because of absence of band at 1725 cm-1 which represents acetyl group. Absence of acetyl groups after modification was also proved by 13C CP MAS NMR. Amorphous character of original gum karaya was determined by XRD. TGA was used to evaluate amount of moisture and thermal stability of original and modified samples. Thermal stability of OGK was higher (280 °C) than of modified samples. Thermal stability of MGK was affected by reaction parameters. Thermal changes in polysaccharide chains were studied by DSC but any significant differences between OGK and MGK were not observed. Mineral composition of original and modified samples was investigated by ICP OES and presence of calcium, potassium and magnesium ions in OGK was confirmed. Molecular weight of modified samples was evaluated by GPC and was approximately 8 million g·mol-1. Rheological measurement for determination of linear viscoelastic region was determined. Effect of NaCl on viscosity of original gum karaya was performed. Viscosity of OGK decreased with higher amount of NaCl. Lower viscosity of OGK is connected with exchange of Ca2+ for Na+ ions and release of the physically bonded structure resulting in higher solubility of OGK in water.
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