|
|
The Utilization of Light Scattering Techniques for the Study on Hydrogel Gelation
Candráková, Simona ; Smilek, Jiří (referee) ; Kalina, Michal (advisor)
This bachelor thesis focuses on the study of hydrogel gelation using light scattering methods. For these purposes two different biopolymers (agarose and sodium alginate), with different sol to gelation phase transition, were selected. In the case of agarose, the gelation is caused by temperature change. On the other side, the gelation of sodium alginate is initiated by addition of polyvalent cations. In the experimental part of the work, agarose gelation was studied by DLS, temperature gradients of agarose solutions (40 – 30 °C) were measured. During the measurement the particle size distributions in the solutions having different concentrations were monitored as well as the temperature influence on the diffusion coefficient. The DLS method provided the values of the gelling temperatures of the solutions at a concentration of 0,5 wt.% and 1,0 wt.%. Furthermore, the DLS microrheology method was used, where temperature dependences of viscoelastic characteristics of agarose solutions (40 – 30 °C) were also measured, from which the gelling temperatures of agarose solutions of 0,1 wt.% and 0,5 wt.% were evaluated. The classical rheology was also used in the work to compare the viscoelastic behaviour of the samples and to determine the gelation point of the agarose solutions. By this method were determined gelling temperatures for all studied concentration of agarose (0,1 wt.%, 0,5 wt.% and 1,0 wt.%). The DLS method was also used to monitor the interactions of sodium alginate with the addition of Ca2+ ions, these interactions were then also evaluated and discussed in the experimental part.
|
|
|
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.
|
|
|
Optimalization of techniques of microrheology for characterization of biopolymer hydrogels
Dušenková, Alica ; Smilek, Jiří (referee) ; Sedláček, Petr (advisor)
The main aim of the bachelor thesis is optimalization of microrheological techniques for characterization of biopolymer hydrogels. Hydrogels, based on thermoreversible biopolymer agarose, were selected for these experiments. The influence of incorporated poly(sodium 4-styrenesulfonate) on structure and viscoelastic properties of agarose hydrogels was investigated through diffusion coefficient and MSD curves. Microrheological properties were studied by fluorescence correlation spectroscopy, by using fluorescent beads, which were embedded in hydrogel systems.
|
|
|
Advanced microrheological techniques in the research of hydrogels
Kábrtová, Petra ; Smilek, Jiří (referee) ; Mravec, Filip (advisor)
This diploma thesis deals with the use of fluorescence correlation spectroscopy technique for microrheological characterization of hydrogel in a system of hyaluronate-cetyltrimethylammonium bromide. Fluorescently labelled particles were used for microrheological FCS analysis. To optimize the method the most appropriate size of particles was chosen on the basis of Newtonian glycerol solutions analysis. Among other things, the discussion was focused on the influence of refractive index change of analysed solutions on analysis results. After hyaluronate solutions analysis it was possible to assess the biopolymer concentration and molecular weight impact on the FCS microrheology results, which could then be compared with analysis results of model hydrogels of hyaluronate and CTAB. Finally, usability and limitations of FCS microrheology have been discussed.
|
|
|
Passive microrheology of colloidal systems based on biopolymers.
Bjalončíková, Petra ; Burgert, Ladislav (referee) ; Mravec, Filip (advisor)
Diploma thesis was aimed to deal with evaluation of microrheology method in the research of biopolymer-protein. Used biopolymer was sodium hyaluronate and proteins were trypsin and chymotrypsin. For measuring of microrheology were used particles with different radius (0,5 m and 1 m). It was found, that both substances have viscous charakter. Passive microrheology is suitable for measuring the viscoelastic properties of biopolymers.
|
|
|
Interaction between surfactants and hyaluronan with different molecular weight.
Vašíčková, Kamila ; Lehocký,, Marián (referee) ; Pekař, Miloslav (advisor)
The behavior of the system consisted by mixture of two different molecular weight hyaluronates and surfactant was investigated. Mixtures were 17 kDa hyaluronate with 1,46 MDa, 73 kDa with 1,46 MDa, 300 kDa with 1,46 MDa, 806 kDa with 1,46 MDa and 1800 kDa with 1,46 MDa. These compounds were always mixed in the weight ratios 70:30, 50:50 and 30:70. As the surfactant cetrimonium bromide and TWEEN 20 were used. Interactions were studied in aqueous solution with different ionic strength. Sudan red was used as hydrophobic dye. In all experimental series with cetrimonium bromide was observed phenomenon of discontinuous separated phases, described as pearls. Samples containing pearls were tested on stability, were dried and rehydrated back, as were also heated in solution. Subsequently, the particle size was measured in the remaining sample after pearls were filtrated. Mixtures of hyaluronate were characterized by measuring the viscosity using rheology microrheology. It was found that these compounds are heterogeneous and each sample point is not the same viscosity.
|
|
|
Microrheology in study of biopolmer colloids.
Hnyluchová, Zuzana ; Sedláček, Petr (referee) ; Mravec, Filip (advisor)
A new method for determining the viscoelastic properties of materials was introduced and investigated. Results of three groups of samples obtained using one particle microrheology method, DLS microrheology method and classical rheology method were compared to be sure of correctness of measurements. As a model system were chosen mixtures of glycerol of different viscosities. In case of samples containing glycerol, results were also compared with tabulated values. Hyaluronan of various molecular weights was used as a biopolymer and polystyrene particles were used for microrheology. It was confirmed, that viscosity values of biopolymer samples obtaining by each method are comparable.
|
|
|
Microrheological study hyaluronan solutions after exposure to low temperatures
Habánková, Eva ; Sedláček, Petr (referee) ; Mravec, Filip (advisor)
The aim of this bachelor thesis is to study the influence of a repeated freezing and thawing process to hyaluronan solutions. The thesis is meant to determine if repeatedly exposing hyaluronan solutions to low temperatures may change the arrangement of the polymer chains and develop weak interactions between these chains. In the thesis the applicability of the two microrheological methods was verified and these were single particle microrheology and dynamic light scattering. For microrheological measurements we used polystyrene particles with a diameter of 0,5 m. There was an effort to determine changes in the structure of hyaluronan solutions by changing the dependence of mean square displacement of particles on time and by changing viscosity of the hyaluronan solutions. Infrared spectroscopy was used as the accompanying method but it proved to be unsuitable for this purpose.
|
|
| |
|
|
Microrheology with Fluorescence Correlation Spectroscopy
Kábrtová, Petra ; Sedláček, Petr (referee) ; Mondek, Jakub (advisor)
A comparison of three passive microrheological techniques was made with the emphasis on FCS. Fluorescently labelled and unlabelled polystyrene particles were used to probe a microrheological response of glycerol solutions, Mili-Q water and sodium hyaluronate solutions. In addition, for FCS technique an approximated equation for calculation of MSD values was derived and verified. It was found that FCS outmatches current microrheological techniques of DLS and video-based particle tracking by its ability to gain a broader data range including the area in which, until now, it was impossible to describe a microrheological behaviour of samples reliably.
|
guest ::
