|
|
Studying the quality of hydrophobic domains in the phase separated hydrogels
Burešová, Natálie ; Pekař, Miloslav (referee) ; Mravec, Filip (advisor)
The thesis deals with the study of hydrophobic domains in phase separated hydrogels. Two types of polyelectrolytes (hyaluronan, dextran) and oppositely charged surfactants (carbethopendecinium bromide, sodium dodecylsulphate ) are used. Phase separated hydrogels are formed by electrostatic interactions. The target of the thesis is to study the polarity of environment in phase separated hydrogeles by fluorescence spectroscopy. Fluorescence measurements is performed by using pyrene, Nile red and laurdane as fluorescence probes. All probes are sensitive to the polarity of the environment. The results showed that probes can be expected in the polar environment of hydrogels.
|
|
|
Time-temperature superposition principle used for study of rheological properties of polymer materials
Kadlec, Martin ; Jarábková, Sabína (referee) ; Smilek, Jiří (advisor)
This bachelor thesis provides a study of the “time-temperature superposition” principle and its applicability to hydrogels. According to current research, honey was chosen due to its simple viscoelastic properties (Newtonian liquid) as a suitable material for optimalization procedure. The knowledge obtained during optimization was further applied to real hydrogel materials, namely the agarose gel was selected as an example of thermoreversible hydrogel, as well as the hyaluronan and dextran gels as examples of hydrogels formed by the interaction of the polyelectrolyte with the opposite charged surfactant. By using the “time-temperature superposition” principle, a considerable increase in the range of the observed oscillation frequencies was achieved for all chosen samples, which led to gain of information about storage and loss or complex modulus, which could not be achieved by classical oscillatory test. Although master curves were generated for all the samples examined, curves for storage and loss modulus could be created separately only for hydrogels formed by the interaction of the polyelectrolyte with the opposite charged surfactant. For this reason, this group of hydrogels appears to be more suitable materials for the application of the “time-temperature superposition” principle.
|
|
|
Use of microcalorimetry in the study of hydration of biopolymers
Bola, Tomáš ; Smilek, Jiří (referee) ; Krouská, Jitka (advisor)
This master thesis deals with the using of microcalorimetry in the study of hydration of biopolymers. Lactose has been selected together with the other biopolymers although it is not among biopolymers but disaccharides. Selected biopolymers are alginate, dextrane, chitosan and hyaluronan of two molecular weights. Lactose has been selected for these purposes mainly because it is a model example to determine whether or not the reaction to moisture between the other samples and the saturated salt solution occurs. The biopolymer hydration study, as opposed to the commonly used perfusion calorimetry method using the possibility of measuring with adjustable moisture has been used an isothermal microcalorimetry method where at two constant temperatures the reaction of the sample to the different moisture released by the saturated salt solution was monitored.
|
|
|
Diffusion of dyes in biopolymeric hydrogels
Vyroubal, David ; Mravec, Filip (referee) ; Klučáková, Martina (advisor)
This thesis is focused on diffusion of dyes in biopolymer-based hydrogels. These hydrogels are based on interaction between biopolymer-like electrolytes with oppositely charged surfactants. When polyelectrolytes interact with oppositely charged surfactants, micelle-like nano-containers can be formed. These nano-containers are able of binding hydrophobic compounds. In this study, combination of modified dextran (diethylaminoethyl dextran) with positive charge and oppositely charged sodium dodecylsulphate as surfactant was used for preparation of hydrogels. Next type of hydrogel was based on hyaluronan and positive charged surfactant Septonex (carbethoxypendecinium bromide). As a diffusion probes in hydrogels dyes Nile red and ATTO 488 were used. The diffusion of these dyes from aqeous solutions of NaCl or surfactants into hydrogels was monitored in time. Transport of dyes into structure of hydrogels was characterized by diffusion coefficients and structural parameters of hydrogels.
|
|
|
Comparative study of interaction between surfactant and hyaluronan and different polyelectrolytes.
Stiborský, Filip ; Pravda,, Martin (referee) ; Pekař, Miloslav (advisor)
In this diploma thesis, the interactions between polyelectrolyte and surfactant at low and also at high concentration were studied. There was used pyrene as fluorescent probe during the fluorescence spectroscopy measurement, a cationic surfactant cetyltrimethylammonium bromide and as a main polyelectolyte has been chosen sodium polystyrene sulfonate at 1 MDa molecular size. In the medium containing 0.15 M NaCl we could observed a creation of the complexes – precipitates in the surrounding of CMC concentration and behind of this concentration. In the mixtures containing sodium polystyrene sulfonate and hyaluronan together, there was stronger tend to keep aggregation properties of sodium polystyrene sulfonate during difference concentration ratios. Beyond CMC concentration, hyaluronan starts to influence the aggregation properties of the system as well.
|
|
|
The intrecations of dextran with surfactant SDS
Marčanová, Milada ; Kalina, Michal (referee) ; Hurčíková, Andrea (advisor)
Before the itself of characterization interactions of dextran with surfactant SDS, there were investigated properties of dextran solution in water and in sodium chloride. At first it was measured by densitometer, where their density and ultrasonic velocity was investigated, depending on concentration and temperature. The ultrasonic velocity was further measured by high resolution ultrasonic spectroscopy. Subsequently the interactions of dextran with surfactant SDS was examined to determine the critical aggregation and critical micelle concentration.
|
|
| |
|
|
Study of hydration of biocolloids
Hývnarová, Lucie ; Sedláček, Petr (referee) ; Klučáková, Martina (advisor)
The subject of this master’s thesis was to examine the hydration properties of selected biocolloids. Specifically, humic substances (fulvic and humic acids), hyaluronic acids in three molecular weights, dextran and chitosan were investigated. Hydration properties of selected biocolloid substances were studied by various methods. The influence of water content during the dissolution of substances and the different time for which water acted on biocolloids were studied. Differential scanning calorimetry DSC measurements resulted in enthalpies and crystallization and melting points. Heat fluxes resulted in the use of perfusion calorimetry. TGA thermogravimetric analysis was used to determine the moisture content of the bioolloids used, after measuring the perfusion calorimeter.
|
|
|
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.
|
|
|
Transport properties of dextran-based hydrogel systems
Vyroubal, David ; Kalina, Michal (referee) ; Klučáková, Martina (advisor)
This bachelor thesis is focused on study of transport properties of dextran-based hydrogel systems. The aim of this work is to determine their ability to absorb and release substances. Nile red was used as a probe to examine the transport properties of these systems. All hydrogels were prepared by the so-called wet way. At first stock solutions of dextran and surfactants were prepared and subsequently mixed to form a hydrogel. Nile red was dissolved in the surfactant stock solution and colored gels were formed upon mixing with dextran stock solution. Several types of gels were thus formed which differ in the concentration of the surfactant and nile red used. Supernatants were spectrophotometrically measured at various time intervals. For study of transport properties in multiple surroundings, the original supernatant was replaced after hydrogel preparation with a surfactant solution or physiological saline solution.
|
guest ::
