|
|
Hydrogels modified by amphiphilic structures
Heger, Richard ; Sedlařík, Vladimír (referee) ; Kráčalík, Milan (referee) ; Pekař, Miloslav (advisor)
The submitted dissertation deals with the influence of amphiphilic structures on hydrogel properties. Additions of various amphiphilic substances associated with the formation of highly ordered structures affect the mechanical, transport and structural properties of hydrogels. The main inspiration for this type of work was living tissue, more precisely the extracellular matrix, which is often mimicked by hydrocolloids, and its high orderliness is responsible for its unique properties. The knowledge obtained from this tissue was applied to the hydrogel systems studied in this work. Various cross-linked hydrogel matrices (physically cross-linked agarose and gelatin, ionically cross-linked alginate and chemically cross-linked mixture of polyvinyl alcohol and chitosan) were suitable representatives for this work. These hydrogel systems were modified by the addition of various amphiphilic substances. The human body’s own phospholipid, lecithin, or variously charged more classic surfactants (CTAB, SDS and Triton X-100). Experimentally, this work is divided into three areas, the study of mechanical properties using rheology, the description of transport properties via release and flow experiments using various model drugs (rhodamine 6G, eosin B, amido black 10B, methylene blue and riboflavin), and morphological characterization using SEM. The characterization of hydrogel systems was supported by other techniques used in this work, such as drying and swelling experiments or gas sorption.
|
|
|
New Areas of the Ultrasonic Application in Microelectronics Technology
Buršík, Martin ; Pietriková, Alena (referee) ; Králová,, Iva (referee) ; Szendiuch, Ivan (advisor)
Doctoral thesis deals with the deposition of special thixotropic materials for microelectronic technology. The aim of the work is the development of the new method optimizing the dosing process in order to achieve a print resolution of better than 100 microns. The work includes the development of a special dispensing head (UZD) using the influence of ultrasonic energy. These results demonstrate the possibility of a newly developed method that is able to print thixotropic materials with a resolution of 65 microns. Compared to other methods achieves these results with the commonly used materials for thick film technology with particle size up to 5 microns.
|
|
|
Study on relaxation properties of hydrogels using rheological techniques
Lorenc, Pavel ; Klučáková, Martina (referee) ; Smilek, Jiří (advisor)
Submitted bachelor’s thesis deals with the study of relaxation and time stress of viscoelastic substances (hydrogels) using selected rheological techniques, especially with regard to oscillation tests. Hydrogels with different types of crosslinking were prepared and their properties were compared during the measurement. Agarose hydrogels (physically), alginate hydrogels (physicochemically), polyvinyl alcohol hydrogels (chemically) and hyaluronic acid hydrogels (ionically). In this bachelor's thesis, methods for measuring the relaxation properties of these hydrogels using a rheometer were designed and subsequently applied. We examined the relaxation properties of hydrogels using time-dependent tests that examined changes in amplitude over time. We performed a test that had 3 intervals, in which we monitored the response of hydrogels to the changes by changing the amplitudes of deformation with time. The relaxation properties of these hydrogels were studied, which showed significant differences in the behavior of hydrogels in measurements.By these methods, it was found that the structure of hydrogels and concentrations have an influence on relaxation. From the measured results, it was shown that the best relaxing properties have chemically crosslinked polyvinyl alcohol hydrogel, the lowest ability to relax was shown by physico-chemically crosslinked alginate hydrogel.The results from the measured data were finally compared, assessed and commented on the differences between the individual hydrogels.
|
|
|
Viscosimetry of hyaluronan-amphiphile systems
Trojan, Martin ; Běťák, Jiří (referee) ; Chytil, Martin (advisor)
This bachelor thesis investigates the interaction between the polysaccharide sodium hyaluronate (HA) and some amphiphilic molecules. As amphiphilic molecules the aminoacids lysine and 6 – aminocaproic acids were chosen. The presence of the carboxylic group on HA and the aminogroup on the aminoacids suggests electrostatic interaction between these two compounds. This supposal offers the possibility to modificate HA and uses it as a new type of a carrier of bioactive compounds, for example medicals. The HA of two molecular weights (1.75MDa and 70kDa) were chosen for the study of the interactions with the aminoacids. Solutions of HA and stock solutions of the aminoacids were prepared for their mutual mixing in the various volume ratios. The solutions and the mixtures were measured in three types of environment: pure water, 0.15M solution of NaCl and in phosphate buffer (PBS) of pH 6. The interactions were investigated by means of reometry. Our results show, the presence of interactions between HA and the aminoacids mainly in the system consisting the 1.75 MDa HA and lysine in water. As a result of the interactions, a decrease in the viscosity of the mixtures comparing to the HA solutions was observed.
|
|
|
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.
|
|
|
Testing of binders of thermal insulations for specific applications on technical appliances
Maňák, Jan ; Kulísek, Karel (referee) ; Petránek, Vít (advisor)
This work focus on testing alcali-activated binders for thermal insulation which could be used for special industry devices. In the beginning of this work is presented example of thermal energy storage where these specific alcali-activated materials can be used. Ensuingly two construction with thermal energy storage tanks are mentioned. Most of the interest aims on ageing and rheological properties of alcali-activated binder. Some rheological methods are also discussed. In the end of this work is added practical experience.
|
|
|
Preparation, characterization of trimethylchitosan and verification of its interaction ability with regards to variable charged ionic compounds
Bayerová, Zuzana ; Pekař, Miloslav (referee) ; Smilek, Jiří (advisor)
The aim of this thesis is to study the interactions of trimethylchitosan with oppositely charged substances with regard to its potential biomedical use. A substantial step before the study of interactions was a successful synthesis of trimethylchitosan, which was subsequently confirmed by characterization of the final synthesis product using physico-chemical methods (infrared spectroscopy, elemental analysis, nuclear magnetic resonance). The result product was subjected to negatively charged interactions such as sodium dodecyl sulphate as a representative of the ionic surfactant, alginate as a natural polysaccharide representative and Chicago Blue as a representative of the anionic dye. The ability to interact with sodium dodecyl sulfate and alginate was demonstrated by the formation of hydrogels, which were subsequently characterized by mechanical viscosity tests using rheometric properties. The positive affinity of trimethylchitosan for organic dyes has been investigated in agarose-based support hydrogel matrices for changes in transport and barrier properties.
|
|
|
Characterization of hydrogels based on photocross-linked derivative of hyaluronan
Hekrlová, Veronika ; Smilek, Jiří (referee) ; Klučáková, Martina (advisor)
This bachelor thesis focuses on characterization of hydrogels based on photocross-linked Tyramine-modified hyaluronan (HA-Tyr). In the first part of the work, swelling of gels in saline and porcine plasma was examined, in which the hydrogels swell significantly less. The second part of the thesis is focused on rheology. First, dependence of the apparent viscosity of precursor solutions on shear rate was tested. The apparent viscosity increases with the concentration of derivative and Mw. This trend can also be observed when measuring viscoelastic properties (the elastic modulus) in oscillation mode (strain sweep test). The elastic modulus can also be affected by using a higher concentration of the photoinitiator riboflavin (RF), higher radiation intensity or by longer exposure times, although the material can be degraded. The work also includes an ATP bioluminescence method cytotoxicity test, which proved that the methods used are safe for in situ application.
|
|
|
Slit flow rheometer for magnetic and non-magnetic fluids
Železník, Tomáš ; Vimmr, Jan (referee) ; Roupec, Jakub (advisor)
In this thesis was designed, manufactured and tested the fourth evolution of a slit-flow rheometer with another necessary parts, eg. rheometer`s holder, drive frame and important jig tools. The rheometer is able to measure rheological properties of magnetic and non-magnetic fluids at very high shear rates, which commercial rheometers can not reach. It is designed for 200 bar pressure and maximum load 15 kN. The construction of the slit-flow rheometer with it`s holder and drive frame improves user friendliness, accelerates change of the fluid sample and expands research opportunities thanks to a big space for additional adjustments. It is possible to use different length of the slit and thanks to a changeable inserts it is possible to change parameters of the slit (roughness of the walls, wall material, thickness of the slit). A part of this thesis was focused on illation of necessary equations for planning calibration measurements. Aim of these measurements is to obtain minor pressure losses dependence on Reynolds number for specific slit.
|
|
|
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.
|
guest ::
