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Polysaccharide gels in medical applications
Svitačová, Denisa ; Kadlec, Martin (referee) ; Venerová, Tereza (advisor)
This bachelor thesis deals with the performance of hydrogels containing polysaccharides, their characterization and reproducibility of the preparation of these gels, which is described in the literature. Based on the research, suitable polysaccharides, namely guar and gellan gum, were selected. Subsequently, an article was selected, the procedure of which was reproduced. Calcium chloride was used as a crosslink agent in the mixture of guar gum and gellan solution. Problems appear in the reproducibility of the article which did not allow the exact repetition of the hydrogel preparation procedure described in the article. Based on the findings, an optimized range of mixtures with various other gelling agents was developed. The individual prepared materials were suitably characterized by rheological tests. Specifically, amplitude tests, the results of which proved the formation of a three-dimensional network in their structure, and thus the formation of hydrogels. Frequency tests were used to determine their mechanical properties.
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Transport Properties of Gellan Hydrogels
Sokolínský, Jan ; Sedláček, Petr (referee) ; Kalina, Michal (advisor)
This bachelor thesis deals with the characterization of mechanical and transport properties of gellan based hydrogel systems. As gellan gum is a biopolymer, hydrogels based on this biopolymer are suitable candidates for use in the pharmaceutical industry and medical applications. The characterization of mechanical properties was realized by rheological analysis and by drying scales, transport properties were characterized by diffusion experiments in combination with the detection using UV-VIS spectrometry. The result of this work is a comparation and commentary of the measured data, in order to provide an overview of the properties of physical gellan gum hydrogels. It was found out that by changing the concentration of the biopolymer and by a suitable selection of the dispersion medium, transport, and mechanical properties of the physical gellan gum hydrogels can be modified.
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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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Incorporation of glucose oxidase into hydrogel structures
Suchá, Klára ; Obruča, Stanislav (referee) ; Mravec, Filip (advisor)
This bachelor thesis deals with the incorporation of the enzyme glucose oxidase into hydrogel structures, while the activity of the enzyme after the incorporation into the hydrogel structure was monitored. Glucose oxidase was incorporated into the agarose hydrogel at various concentrations (1 and 2 wt. %). Glucose oxidase activity was determined using the resulting hydrogen peroxide, the concentration of which was measured by fluorescence spectroscopy using an Amplex Red fluorescence probe. The enzyme was found to be active even after incorporation into the hydrogel, but the concentrations of hydrogen peroxide formed were lower compared to the free enzyme. Furthermore, it was found that the enzyme reacts with agarose itself, but this reaction did not significantly affect the rheological properties of the hydrogel.
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Bioactive substances for face cream: Determination of stability of face cream incorporated with goat's milk
Dostálová, Tereza ; Sovová, Šárka (referee) ; Enev, Vojtěch (advisor)
The aim of this bachelor thesis is a stability trial of a skin cream incorporated with goat milk lyophilizates prepared in usual laboratory conditions. Firstly, the goat milk was denatured, to be further analysed via FTIR, elemental analysis and thermogravimetry. To compare the denaturation effect, measurements with native goat milk sample were performed as well. Next, an emulsion was prepared. First stability tests were performed using analytical centrifuge and the cream preparation procedure and component ratio was optimized. Stability trials were carried out at specified time intervals. Rheological properties – especially yield stress values and structure strength, determined by linear viscoelastic region and complex modulus – thermal endurance measured via differential scanning calorimetry and visual validation via optical microscopy and sample observation were tested and performed. Skin cream stability of sample stored at laboratory temperature was demonstrated, showing moderate sings of structure destabilisation. Product suitability for dry skin was proved by sensory analysis. The skin feeling was pleasant, and the cream moisturized the surface area, that it was applied to, according to evaluators. Visually, the emulsion appeared to maintain its properties during the experiment time range, it did not undergo a complete degradation of separation into two original phases, nor it was degraded, for example by mold.
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Hydrogels with incorporated vesicular systems
Kalendová, Lucie ; Pekař, Miloslav (referee) ; Venerová, Tereza (advisor)
This bachelor thesis deals with the incorporation of vesicular systems into polysaccharide – based hydrogels. The chosen vesicular systems were Ion Pair Amphiphile vesicles (IPA), which consist of cetrimethylammonium bromide, sodium dodecyl sulfate, dioctadecyldimethylammonium chloride and cholesterol. The work is divided into two parts. In the first part, interactions between IPA vesicles and sodium hyaluronan and interactions between IPA vesicles and sodium polystyrene sulfonate were studied. Even though interactions occured, it was not possible to prepare a hydrogel based on these interactions. The second part of this work deals with incorporation of IPA vesicles into an agarose – based gel when heated. Particles of two different concentrations (1 mmol·l1 and 2 mmol·l1) were used. The effect of the IPA particles on the properties of the gel was observed with rheological measurements. The results showed that the gel with incorporated particles has a longer linear viscoelastic region and that there were no interactions between the IPA particles and the gel. The particles only fill the gaps of the gel network. Different behaviour within the gels with different concentrations of IPA vesicles was not observed.
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Viscoelastic properties of hydrogels depending on relative humidity
Kouřilová, Ludmila ; Heger, Richard (referee) ; Smilek, Jiří (advisor)
This bachelor thesis is mainly aimed on the determination of the dependence of the viscoelastic properties of physically crosslinked hydrogels on the relative humidity controlled by humidity cell (as an accessory to a rotary rheometer), or the desiccator with the drying medium. The main objective was to optimise the methodology of the humidity cell for the rheological determination of the viscoelastic properties of hydrogel materials as a function of relative humidity and to verify experimental setup on the agarose hydrogel. The results showed that the agarose hydrogel gradually loses its dispersion medium after exposure to chosen relative humidity, resulting in a loss of contact between the upper rheometer sensor and the sample when measured with the standard measurement gap control setting, which is constant during the measurement. The setting of the control of normal force proved to be an appropriate solution, which has led to a gradual reduction in the height of the upper rheometer sensor in an attempt to keep the normal force at the desired level during the drying of the hydrogel. A humidity cell proves to be an appropriate method for determining the dependence of the viscoelastic properties of hydrogels on relative humidity. Unlike the use of a desiccator with drying medium, the drying of the hydrogel sample does not result in such rapid drying that it breaks the texture on its surface. Another advantage of a humidity cell is the ability to maintain the desired relative humidity value even if the gel begins to release dispersion medium into its surroundings, which was not possible with a desiccator with drying medium.
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Utilization of various methods of porosimetry in investigation of internal structure of biopolymer hydrogels
Zahrádka, Jan ; Pekař, Miloslav (referee) ; Sedláček, Petr (advisor)
The main aim of the thesis was to select, optimize and test suitable methods for studying inner structure of hydrogel materials. The study of the size of pores with potential use in fundamental and applied research of these materials is the central focus of the thesis. Firstly, a literature search was done in order to collect basic information about usefulness of the individual methods. On the basis of this literature search, the experimental part of the work was divided into several steps. First, selected methods of conventional porosimetry (mercury intrusion porosimetry, BET analysis and DSC thermoporometry) were applied on reference porous materials and the results obtained by the individual methods were compared. The methods optimized with the use of these reference materials were then utilized in the analysis of porosity of model hydrogels based on polyvinyl alcohol. Based on the results of this analysis, the usability and benefits of the individual methods were discussed with respect to the sample preparation, time and financial demands, and also from the viewpoint of compliance of the determined pore sizes with the range of sizes declared for the physical PVA gels.
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The effect of polymer microfibers on rheological and mechanical properties of calcium phosphate bone cements
Dzurov, Matej ; Montufar Jimenez, Edgar Benjamin (referee) ; Vojtová, Lucy (advisor)
Táto diplomová práca sa zaoberá mechanickými a reologickými vlastnosťami resorbovateľného polymér-fosforečnanového kompozitu na báze kostného cementu vystuženého mikrovláknami z PCL (poly(-kaprolaktón)) a Pluronic-om modifikovanými PCL vláknami. Teoretická časť popisuje štruktúru kostí, vývoj kostných cementov a štrukturálne prídavky (aditíva). V experimentálnej časti je rozoberaná syntéza a charakterizácia PLGA-PEG-PLGA termosenzitívneho kopolyméru a - modifikácie fosforečnanu vápenatého ako aj technika prípravy mikrovláken. Roztok kopolyméru bol použitý pre zlepšenie obmedzenej injektovateľnosti pasty s pomerom kvapalnej k práškovej fáze (L/P) 0,5 ml/g pre všetky vzorky. Dve rôzne techniky zamiešania pasty boli použité pre možnosť kontrolovania porozity pripraveného cementu. PCL a PCL-Pluronic vlákna využité ako výstuž boli testované v troch rôznych prídavkoch, a to 1, 3 a 5 hmotnostných percent vláken na celkovú hmotnosť pripravenej pasty. Pripravené pasty boli testované pomocou dynamickej reologickéj analýzy na reometri pri laboratórnej teplote (23 °C) a fyzologických podmienkach (37 °C) so zámerom stanoviť spracovateľnosť a tuhnutie pasty. Vzorkám na ostatok analýz bolo umožnené vytvrdzovanie pri fyziologických podmienkach po dobu 10 dní. Po vytvrdení boli testované mechanické parametre ako sú pevnosť v tlaku, Youngov modul pružnosti a pevnosť v ťahu v priemere vysušených a v niektorých prípadoch aj hydratovaných vzoriek. Porozita vzoriek bola stanovená pomocou Roentgénovej počítačovej mikro-tomografie. Rastrovacia elektrónová mikroskopia bola využitá na študovanie mikroštruktúry a zabudovanie vláken do keramickej matrice. Prítomnosť vláken bola semi-kvantitatívne stanovená pomocou Fourier transformovanej infračervenej spektroskopie. Difrakcia Roentgénového žiarenia poskytla údaje o fázovom prechode prášku a jeho mineralogickom zložení. Jednotlivé hodnoty, obdržané z jednotlivých analýz, boli medzi sebou porovnané a adekvátne diskutované. Výsledkom práce je potvrdenie mierneho zlepšenia pevnosti v tlaku vzoriek vystužených hydrofóbnymi PCL alebo amfifilnými PCL-Pluronic vláknami pričom, PCL-Pluronic vlákna poskytli lepšie výsledky. Preto bolo usúdené, že polymér-fosforečnanový kostný cement vystužený vláknami je nádejným kandidátom na uplatnenie v chirurgickej praxi.
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Structural and transport properties of hybrid hydrogels with application utilization
Zhurauliova, Darya ; Pekař, Miloslav (referee) ; Smilek, Jiří (advisor)
The presented diploma thesis deals with the preparation and subsequent characterization of structural and transport properties of hybrid hydrogels based on polyvinyl alcohol and sodium alginate concerning their application potential. The thesis aims to study the current state of the solved issue on the topic of characterization of structural and transport (release) properties of hybrid hydrogels about their use in various branches of human activity and also based on literature research to propose and optimize a suitable preparation procedure and to carry out a series of experiments for their characterization. With regard to the literature research, suitable polymers capable of gelation, such as polyvinyl alcohol (PVA) and natural polysaccharide – sodium alginate, were selected for the preparation of hydrogels. The preparation of this hybrid network involved the physical cross-linking of PVA by freezing and thawing and ionic cross-linking of sodium alginate with calcium ions. By combining these polymers, viscoelastic, swelling and transport properties were determined by using physicochemical methods. Rheological measurements were performed to study the mechanical properties - specifically oscillation and amplitude tests. The structural properties of hydrogels (or xerogels) were determined, by scanning electron microscopy. The transport (release) properties of gel systems were determined by diffusion experiments with the UV-VIS spectrometry detection method, in which an organic dye (methylene blue) was used as a model probe. Another aim of this diploma thesis is to modify the internal structure of hybrid hydrogels with suitable reagents, ie., lecithin. The presence of lecithin in the hybrid hydrogel three-dimensional network serves as a model of the phospholipid bilayer, forming the cell membrane or occurring in tissues, and thus has a significant effect on rheological and transport properties. Physicochemical methods also determined the mechanical, swelling and transport properties of hybrid hydrogels with the addition of lecithin. The conclusion of this work is a summary of measured data to provide a comprehensive overview of this issue. The results suggest that the presence of sodium alginate in the PVA structure reduces the mechanical properties, although the presence of lecithin increases the strength of the hybrid hydrogels. However, by comparing all measurement results, it is possible to determine that sodium alginate, resp. lecithin affects the properties and structure of the hydrogel, which makes it possible to correct the properties of hybrid gel systems according to the required applications.
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