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Preparation and characterization of hydrogels with diffusion gradient
Tvrdoňová, Anna ; Pekař, Miloslav (referee) ; Smilek, Jiří (advisor)
The presented bachelor thesis deals with the preparation and further characterization of hydrogels with a diffusion gradient. The aim of the thesis is a literature research on the issue of hydrogels with a diffusion gradient, and a selection of a suitable method for its preparation. Moreover, conducted pilot experiments lead to the characterization of the properties of the prepared systems, especially with regard to proving the gradient structure of hydrogels. The performed evaluation was based on visual observation, determination of transport, and viscoelastic properties. In addition, a simple method consisting of weighing the prepared hydrogels was used. Hydrogels were compared depending on the choice of crosslinking agent, its concentration, and crosslinking time. Gradient hydrogels based on polysaccharide sodium alginate were prepared. The results suggest that by selecting the concentration of the crosslinking agent, as well as the crosslinking time, the final properties (viscoelastic and transport) of the hydrogels can be adjusted to the desired values. In the discussion of the results, we propose steps for a more comprehensive view of the issue and providing options for the following research.
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Corelation of transport and viscoelastic properties of hydrogels with diffusion gradient
Ščotková, Romana ; Sedláček, Petr (referee) ; Smilek, Jiří (advisor)
The aim of the presented bachelor thesis was to prepare hydrogels with diffusion gradient and to demonstrate the gradient structure of hydrogels in terms of viscoelastic and transport properties. With regard to potential biomedical applications, the cationic polysaccharide chitosan was selected for the preparation, especially for its antimicrobial and biocompatible properties. The resulting gradient hydrogels were subsequently characterized by oscillation tests to observe the differences using different concentrations and molecular weights of chitosan, crosslinking agent concentrations, dispersion environments for chitosan dissolution, and different gel crosslinking times. The samples were also subjected to drying experiments to confirm the gradient structure formed. The ability of the hydrogels to transport the active species was confirmed by visually evaluating the permeation of the anionic dye (bromothymol blue) during the gelation process. From the results obtained during the experimental part of the bachelor thesis it can be concluded that the viscoelastic properties of hydrogels can be modified by changing selected parameters during the preparation itself. It was also confirmed the assumption that with better mechanical properties of hydrogels there is a deterioration of transport properties. By controlled diffusion method, it was possible to prepare a hydrogel with a gradual gradient of crosslinking density, thus modifying the viscoelastic and transport properties.
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Preparation and characterization of polysaccharide hydrogel systems with gradient structure
Škutová, Patricie ; Krouská, Jitka (referee) ; Smilek, Jiří (advisor)
This bachelor thesis deals with the preparation of polysaccharide hydrogels with a diffusion gradient and their subsequent characterization in terms of viscoelastic properties, which are used to demonstrate the gradient structure. The main goal was to select a suitable method for the preparation of chitosan hydrogels with different molecular weights (168 kDa - 437 kDa). The biopolymer chitosan is a cationic polysaccharide that is suitable for use in biomedical applications due to its excellent biocompatible properties. First, concentration-uniform hydrogels without gradient structure were prepared, in which the influence of various parameters (chitosan molecular weight, chitosan concentration, sodium hydroxide concentration) was investigated. To prove the created gradient structure, the samples were subjected to the drying method (determination of the dispersion fraction) and determination of mechanical properties by oscillatory rheometry. Increased attention was paid to the search for a suitable preparation method for gradient chitosan hydrogels with higher molecular weight, which showed some problems with the already established method of preparation of hydrogels with gradient structure controlled by diffusion. From the results of the measurements obtained, it can be concluded that the viscoelastic properties of the hydrogels can be modified by changing the selected parameters and the method of preparation. By the controlled diffusion method, it was possible to prepare hydrogels with a gradual gradient of cross-linking density, which confirmed the assumption that the more cross-linked the layer, the higher the values of viscoelastic moduls and therefore the higher resistance to stress was confirmed.
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Corelation of transport and viscoelastic properties of hydrogels with diffusion gradient
Ščotková, Romana ; Sedláček, Petr (referee) ; Smilek, Jiří (advisor)
The aim of the presented bachelor thesis was to prepare hydrogels with diffusion gradient and to demonstrate the gradient structure of hydrogels in terms of viscoelastic and transport properties. With regard to potential biomedical applications, the cationic polysaccharide chitosan was selected for the preparation, especially for its antimicrobial and biocompatible properties. The resulting gradient hydrogels were subsequently characterized by oscillation tests to observe the differences using different concentrations and molecular weights of chitosan, crosslinking agent concentrations, dispersion environments for chitosan dissolution, and different gel crosslinking times. The samples were also subjected to drying experiments to confirm the gradient structure formed. The ability of the hydrogels to transport the active species was confirmed by visually evaluating the permeation of the anionic dye (bromothymol blue) during the gelation process. From the results obtained during the experimental part of the bachelor thesis it can be concluded that the viscoelastic properties of hydrogels can be modified by changing selected parameters during the preparation itself. It was also confirmed the assumption that with better mechanical properties of hydrogels there is a deterioration of transport properties. By controlled diffusion method, it was possible to prepare a hydrogel with a gradual gradient of crosslinking density, thus modifying the viscoelastic and transport properties.
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Preparation and characterization of hydrogels with diffusion gradient
Tvrdoňová, Anna ; Pekař, Miloslav (referee) ; Smilek, Jiří (advisor)
The presented bachelor thesis deals with the preparation and further characterization of hydrogels with a diffusion gradient. The aim of the thesis is a literature research on the issue of hydrogels with a diffusion gradient, and a selection of a suitable method for its preparation. Moreover, conducted pilot experiments lead to the characterization of the properties of the prepared systems, especially with regard to proving the gradient structure of hydrogels. The performed evaluation was based on visual observation, determination of transport, and viscoelastic properties. In addition, a simple method consisting of weighing the prepared hydrogels was used. Hydrogels were compared depending on the choice of crosslinking agent, its concentration, and crosslinking time. Gradient hydrogels based on polysaccharide sodium alginate were prepared. The results suggest that by selecting the concentration of the crosslinking agent, as well as the crosslinking time, the final properties (viscoelastic and transport) of the hydrogels can be adjusted to the desired values. In the discussion of the results, we propose steps for a more comprehensive view of the issue and providing options for the following research.
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