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Hyaluronan hydrogels for medical applications
Janča, David ; Krouská, Jitka (referee) ; Venerová, Tereza (advisor)
This work studies properties of hydrogels prepared by the interaction of polyelectrolyte hyaluronate with cationic surfactant cetyltrimethylammonium bromide (CTAB) in a model physiological solution of 0,15 M NaCl. Effects of different pH and final pH of different samples of hydrogels were studied. Furthermore, stability of hydrogels was observed by fluorescence spectroscopy, where pyrene was used as a fluorescence probe, and isothermal microcalorimetry. It was found that low temperature disrupts gel integrity and it is not recommended to expose hydrogels to other than a neutral pH.
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Thermosensitive polymer gels
Pelánová, Markéta ; Smilek, Jiří (referee) ; Chamradová, Ivana (advisor)
The presented thesis on thermosensitive polymer gel is focused especially on a thermosensitive triblock copolymer, which is composed of hydrophobic polylactide, polyglycolid and hydrophilic polyethylene glycol (PLGA-PEG-PLGA). Thermosensitive copolymers are very attractive for their phase sol-gel transitions and gel-suspension transitions. The aqueous solution of this copolymer behaves like a sol at laboratory temperature and like a gel at body temperature. These systems are used as injectable carriers for targeted drug delivery with controlled release. However, the influence of the resulting polymer concentration and temperature on the thermosensitive hydrogel nanostructure was not yet fully studied. In the experimental part, the viscoelastic behavior of hydrogels was observed by dynamic rheological analysis at different polymer concentrations and temperature conditions. The average size and distribution of micelles of triblock copolymer in aqueous solution were measured using dynamic light scattering technique. Characterization of fibrous micelles was complemented by imaging technique, cryogenic transmission electron microscopy.
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Preparation and application of physical hyaluronan gel
Kovářová, Lenka ; Krouská, Jitka (referee) ; Venerová, Tereza (advisor)
Bachelor's work is concerning by research in physical hyaluronan gel area. Research is focusing on its preparation, especially by interaction of hyaluronan (HyA) solution with opposite charged surfactant in physiological solution (0,15 M NaCl). In the first part of work I found out influence of molecular weight, concentration of original hyaluronan solution and the ratio of binding sites on hyaluronan chain and surfactant on amount of solids in gel, expressed in percent. Finally we can say, that this value is not influenced by molecular weight of HyA neither relation of binding sides. On the other side, concentration of original HyA solution has significant influence on amount of solids in gel. There was also researched process of gel swelling, where was set amount of water (in percent) able to take dried gel back. Analogical conclusion has been reached like amount of solids in gel. In other part were researched influence of hyaluronan molecular weight and the ratio of binding sites on hyaluronan chain and surfactant on formation of excimers and spectrum change by fluorescence spectroscopy. Pyrene, 1,3-bis(pyren-1-yl)propane (P3P) and prodan were used as fluorescence probes. Excimer emission showed at P3P, while there was no growth of intensity at 470 nm for pyrene. It was found that molecular weight does not affect the value of the ratio of excimer and monomer probe P3P, or the ratio of the first and third peaks of pyrene. The ratio of binding sites HyA and surfactant influence only relation of excimer to monomer (P3P probe), while influence to relation 1:3 hasn't been noticed for pyrene. I have compared spectrum of developed gel for prodan probe, relevant solid and swelled gel by return. It also served for drying and swelling process visualisation.
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Fluorescence probes to study the properties of hydrogel systems
Máčala, Jakub ; Venerová, Tereza (referee) ; Mravec, Filip (advisor)
This bachelors thesis is focused on possibility of selected fluorescent probes for study of properties of hydrogel systems. Chosen probes are Prodan for polarity study, HPTS for measurement of pH of the probe environment and platinum complex [2,6-Bis(2-pyridyl)fenyl-C,N,N]chloroplatinum(II) for its unique fluorescence properties and potential of energy transfer studies in hydrogel systems. Spectral properties of fluorophores were defined in selected set of solvents with different polarity with steady state fluorescence spectroscopy method. Properties of HPTS probe were also tested in buffers with different pH. Subsequently, hydrogels based on hyaluronan-septonex and dextran-SDS with incorporated fluorescence probes were prepared. Steady state fluorescence measurement of fluorophores from hydrogel were made using fluorimeter optical fibres. It was found, that probes Prodan and HPTS are suitable for study of polarity and pH of hydrogels and probably they will be able to be used for study of hydrogel with other techniques, like fluorescence microscopy, however platinum complex is, due to the low fluorescence intensity and possible quenching by polar water environment, probably not suitable for other measurements.
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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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Hydrogels based on microemulsions and polyelectrolytes
Růžičková, Kristýna ; Kalina, Michal (referee) ; Mravec, Filip (advisor)
This bachelor thesis deals with preparation and characterization of microemulsion based phase separated hydrogels while using low molecular weight and high molecular weight hyaluronan. Microemulsions were prepared from canola oil, sunflower oil, lemon oil and tea tree oil. As a dye for studies of behaviour of hydrogels was used Oil red O which simulates hydrophobic drug. The main part of this thesis studies the release of this dye from hydrogels by using UV-VIS spectroscopy. The content of the dye in hydrogels was monitored after 24, 48 and 72 hours. Based on measured data we can state that hydrogel prepared from low molecular weight hyaluronan release bigger amount of the dye than hydrogel from high molecular weight hyaluronan. Based on measured data after 72 hours we can say that hydrogel from microemulsion with tea tree oil and hydrogel from microemulsion with lemon oil released bigger amount of the dye than hydrogel without microemulsion. Another advantage of these two hydrogels is increased thougness. Content of sunflower and canola oil indicated rather negative influence on behaviour of hydrogels.
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New Methods of Study of Reactivity and Transport Properties of Biocolloids
Smilek, Jiří ; Weidlich,, Tomáš (referee) ; Pabst, Willi (referee) ; Klučáková, Martina (advisor)
The main aim of doctoral thesis was the study on reactivity, transport and barrier properties of biocolloidal and synthetic polymeric substances by simple diffusion techniques. It was studied mainly the influence of basic physic-chemical parameters (temperature, concentration, pH and modification of material) on the reactivity and barrier ability of chosen compounds. Further substances were chosen as a model compounds: biocolloids (humic acids, alginate, chitosan, hyaluronate) and synthetic polymer (polystyrenesulfonate). Reactivity, barrier and transport properties of chosen substances were studied by interactions with oppositely charged basic organic dyes (methylene blue, rhodamine 6G, amido black 10B respectively) in hydrogels medium based on linear polysaccharide (agarose). The attention was also paid to basic physic-chemical characterisation (infrared spectroscopy, rheology, elemental analysis, thermogravimetry and scanning electron microscopy) of chosen materials and also hydrogels. Key part of the whole doctoral thesis was the optimization of selected diffusion techniques (diffusion cell technique and non-stationary diffusion in cuvettes) designated for the study on reactivity and barrier properties of wide range compounds (optimized method should be used as an universal method for simple and fast determination of reactivity of different compounds at given or changing conditions). The rate of reactivity, transport and barrier properties was determined based on fundamental diffusion parameters such as diffusion coefficients, break-through time so called lag time, interfacial concentration of chosen organic dye, apparent equilibrium constant, tortuosity factor, partition coefficient.
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Time-Resolved Fluorescence in Research of Hyaluronan-Colloidal Systems Interactions
Mondek, Jakub ; Táborský, Petr (referee) ; Peter, Kapusta (referee) ; Pekař, Miloslav (advisor)
The aim of the doctoral thesis was to study advanced fluorescence techniques and its use in colloids or hyaluronan-surfactant systems and hydrogels based on hyaluronan, respectively. Steady-state and time-resolved fluorescence were used to study excited state proton transfer fluroescen probes in hyaluronan-surfactant systems to asses the influence of hyaluronan hydration to its interactions with oppositely charged surfactants. Firstly, different excited state proton transfer fluorescence probes were discussed to choose the most suitable candidate for next research. The influence of hyaluronan on inner environment of micells was determined based on the sensitivity of excited state proton transfer of chosen fluorescence probe 1-naphtol and, based on above mentioned experiments, the structure of hyaluronan hydration shell was discussed. The next part of doctoral thesis was focused on fluorescence lifetime correlation spectroscopy and on the development of method of nanorheology. Measured correlation functions were transformed to mean square displacement with developed MATLAB script. Firstly, the fluorescence method was compared with well described methods such as videomicrorheology and dynamic light scattering to asses the reliability of fluorescence correlation spectroscopy in microrheology. Secondly, nanorheology method was developed and its use in passive nanorheology of hyaluronan hydrogels was discussed. Based on mentioned experiments, the fluorescence correlation spectroscopy microrheology and nanorheology methods were optimized to use the methods in hydrogel research.
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Upgrade of extruder head for 3D bioprinting of thermolabile hydrogels
Kedroň, Kryštof ; Harabiš, Vratislav (referee) ; Jaroš, Josef (advisor)
3D bioprinting is a perspective method of tissue engineering, capable of creating tissue structures with physiological function and spatial arrangement. The thesis deals with the use of this method for printing thermolabile hydrogels. The main goal of the thesis is to extend the print head for 3D printing of thermolabile hydrogels. The theoretical part is devoted to the description of 3D bioprinting, especially the important properties that each material must meet to be able to print, there is also a review of used hydrogels in bioprinting, focusing on thermolabile, print modalities, the possibility of cooling the printhead and a description of the ideal equipment for printing of thermolabile hydrogels. The practical part deals with the design and realization of the print head for 3D printing of thermolabile hydrogels, in the last part the achieved results are evaluated and discussed.
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Hydrogels with carbon fibers
Kučerová, Barbora ; Bouška,, Marek (referee) ; Pekař, Miloslav (advisor)
This diploma thesis is focused on the study of the behaviour of carbon fibers in the hydrogel, especially the viscoelastic modules od these gels ort he coefficient of color transmission through the gel. The main goals were to optimize the samples and measure their viscoelastic modules on a rheometer, in several different modes. This was followed by simulation of physiological conditions for selected samples and their measurement on the rheometer. There was also an experiment of continuous diffusion in cuvettes, in which the penetration of the dye through the gel with the addition of fibers and for comparison also without them. Last but not least diffusion pairs were prepared.
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