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Rheology as a powerful tool for the complex characterization of hydrogels
Kadlec, Martin ; Kráčalík, Milan (referee) ; Smilek, Jiří (advisor)
This diploma thesis investigates the suitability of relaxation tests as a part of complex characterization of hydrogel materials using classical rheology methods. With respect to the current research, creep and three interval thixotropy tests were taken into account. For them, general optimization was done aiming to find an ideal parameter settings. The optimization was performed using physically crosslinked agarose (AG) hydrogel and the tuned tests were also applied to two more samples: hyaluronan (HyA) and polyvinyl alcohol (PVAl) gel. These materials were selected due to their mutually different crosslinking principle. The experiments showed, the AG gel proved to have the best ability to recover after deformation of all studied samples. On the other hand, the HyA gel relaxed the worst. Although the final results of both tests were comparable, the regeneration process itself was different. Hence, the complex relaxation characteristics cannot be described using one of the performed tests alone and both the creep and three interval thixotropy tests have great importance in the scope of complex relaxation behaviour. The obtained results may lead to more precise description of deformation and relaxation, which are frequent phenomena occurring during treatment and application of hydrogel materials.
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Interactions of aminoclays with natural polyelectrolytes
Jančík Procházková, Anna ; Mravec, Filip (referee) ; Pekař, Miloslav (advisor)
This thesis deals with the preparation of products of interactions of aminoclay with natural polyelectrolytes. Sodium hyaluronate was chosen as the natural polyelectrolyte. The concentration and volume ratio of solutions of aminoclay and natural polyelectrolyte which led to the formation of any type of product were studied. The resulting coagulates were characterized by microscopy, FTIR spectroscopy and rheology. Furthermore the possibility of interactions with fluorescent probes was studied.
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Dynamic surface tension in study of hyaluronan-surfactant interactions
Herzog, Milan ; Žídek, Jan (referee) ; Pekař, Miloslav (advisor)
The main task was to characterize interactions between negatively charged biopolymer sodium hyaluronate and two cationic surfactants: cetyltrimethylammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB). Interactions between sodium hyaluronate and these surfactants are based on their different charge and can be detected by changes of surface tension. The influence of constant addition of sodium hyaluronate (MW = 90 and 1400 kDa) on interface tension values at increasing bubble lifetime was observed. For this purpose, the maximum bubble pressure method was choosen. The measurements were performed in water and in 0,15 mol•l-1 NaCl solution. The obtained results can be used as for description of dynamic properties of hyaluronate-surfactant systems as, e.g., in targeting drug delivery.
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Fluorescence study of hydrophilic domains of associating colloids
Londinová, Monika ; Knotková,, Kateřina (referee) ; Pekař, Miloslav (advisor)
The properties of the hyaluronan were investigated by using different fluorescence probes, because hyaluronan is a hopeful carrier of an active matter in medicine and cosmetics. Selected fluorescence probes were: cationic acridine orange, Nile Blue A, methylene blue, amphiphilic 4-Di-2-ASP and anionic fluorescein. Except from fluorescence and absorption spectra of the probes were observed electrostatic and hydrophobic interactions as well. The probes in solvents with different polarity (MeOH, EtOH, DMSO) showed the bathochromic shift in the emission maximum and quenching of the fluorescence with the increasing polarity of the solvents. The influence of the ionic strength on fluorescence properties of the probe acridine orange and 4-Di-2-ASP was investigated in aqueous solutions of chlorides. The formation of acridine orange dimer is inhibited with increasing ionic strength. CaCl2 increased the ionic strength the most, then prevented repulsion of carboxylate groups, so it means the expansion of hyaluronan cluster into the solution. However, the emission of the probe 4-Di-2-ASP was quenched with the addition of CaCl2 the most. The first additions of COO– groups cause the formation of dimers of AO shown as decreasing in extinction coefficient and fluorescence intensity. Next addition of the hyaluronan caused a depolymerization of formed dimers and the increase of the emission intensity. The repolymerization caused the decrease and then again the increase. In case of 4-Di-2-ASP was the pattern of the fluorescence (the intensity and the position of the emission) firstly the same, but at the concentration of 1 g dm-3 the emission intensity increased. The probes MB and F were used for spectroscopic studies of the interaction between methylene blue-fluorescein complex and anionic and cationic surfactants. The absorbance of separate MB and F changed only with the addition of surfactants with the opposite electric charge. Absorbance of the mixture MB-F changed with the addition of the CTAC surfactant, while the addition of SDS into the mixture caused only the change of MB absorption spectra.
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Microcalorimetric and Light Scattering Methods in the Study of Interactions in Biopolymer - Surfactant System
Šojdrová, Kamila ; Mravec, Filip (referee) ; Krouská, Jitka (advisor)
Biopolymer surfactant systems have been studied by using different physico chemical methods. As the biopolymer, it was chosen high (1400–1600 kDa), medium (250–450 kDa) and low (8–15 kDa) molecular weight sodium hyaluronate. Two cationic surfactants – cetyltrimethylammonium bromide (CTAB) and carbethopendecinium bromide (Septonex) were selected to provide polyelectrolyte complexes with oppositely charged hyaluronan. The critical aggregation concentration of the surfactant in the system was monitored by dynamic light scattering (Zetasizer Nano ZS). SEC-MALS method was used for the description of the conformation of sodium hyaluronate of different molecular weights and polyelectrolytes complexes hyaluronan surfactant after reaching the aggregation point. Isothermal titration calorimetry (ITC) was used to determine the critical aggregation concentration of the surfactant by monitoring the thermal changes accompanying the aggregation of the system. It was found out that the increasing molecular weight of hyaluronan in these systems decreases the critical aggregation concentrations and conversely.
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Diffusion properties of oppositely charged organic molecules in solutions of hydrophilic polyelectrolyte
Rýcová, Eva ; Márová, Ivana (referee) ; Mravec, Filip (advisor)
This work is focused on physical interactions of negatively charged polymers with small ionogenic fluorescent molecules. Trying to verify the presence of these interactions using fluorescence correlation spectroscopy (FCS) and provides a comprehensive view of the problem. The aim of this work is to observe the effect of concentration on the diffusion properties. P/D ratio, where P represents number of polymer binding sites and D number of dye binding sites, was chosen for this issue. Hyaluronate, sodium chondroitin sulfate and sodium polystyrene sulfonace were used as polymers and Acridine Orange, and Rhodamine 6G were chosen as fluorescent probes. The reason why this experiment uses these probes, was the assumption, that the positive charge occuring on the fluorescent probe will lead to the electrostatic interaction with the negatively charged polymer. As a result, the bond between acridine orange and polyelectrolyte was not clearly demonstrated, but the interaction with Rhodamine 6G have been proved.
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The influence of alcohols on the flow properties of sodium hyaluronate
Habartová, Lucie ; Pekař, Miloslav (referee) ; Smilek, Jiří (advisor)
This bachelor’s thesis examines the influence of alcohol presence on the conformation of sodium hyaluronate aqueous solutions primarily about the use of flow methods utilizing. Two molecule masses of sodium hyaluronan were studied, namely 1500-1750 kDa further referred to as high-molecular sodium hyaluronan and 500-750 kDa referred to as low-molecular. The flow and viscosity properties of high-molecular sodium hyaluronate have been studied in the presence of methanol, ethanol, isopropyl alcohol and terc-butanol in the concentration range 0-80 wt. %. Low-molecular sodium hyaluronate, and above all its flow and viscosity properties, were measured in the presence of ethanol and isopropyl alcohol in the concentration range 0-80 wt. %. Based on measured data, viscosities were assessed at infinitesimal stresses consistent with zero-rate viscosity. The high-molecular sodium hyaluronate ranged up to 327 mPas in terc-butanol solution. Viscosity values increased with the increasing length of the alcohol chain. The low-molecular sodium hyaluronate reached a maximum of 39 mPas in an isopropyl alcohol solution. The viscosity curves of low-molecular sodium hyaluronate were close to that of the Newtonian liquid.
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Diffusion of organic molecules in the hydrogel environment
Holubová, Anna ; Sedláček, Petr (referee) ; Mravec, Filip (advisor)
This diploma thesis deals with study of hydrogels formed by phase separation of hyaluronan with oppositely charged surfactants cetyltrimethylammonium bromide (CTAB) and Septonex. It follows the bachelor thesis and extends the knowledge about the detailed characterisation of the inner environment of the hydrogel by determining the diffusion behaviour of the fluorescent probes Atto 488 and Nile Red using fluorescence correlation spectroscopy (FCS) technique and its modified version dual-focus fluorescence correlation spectroscopy (2f-FCS). Compared results showed that both methods show similar values and probes specifically interact with CTAB but Atto 488 shows only weak interaction with Septonex compared to Nile Red. Additionally, these interactions were not affected by the molecular weight of hyaluronan. In conclusion, it was recommended to measure this type of hydrogel in a small depth of gel using a conventional method.
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The influence of alcohols on the flow properties of sodium hyaluronate
Habartová, Lucie ; Pekař, Miloslav (referee) ; Smilek, Jiří (advisor)
This bachelor’s thesis examines the influence of alcohol presence on the conformation of sodium hyaluronate aqueous solutions primarily about the use of flow methods utilizing. Two molecule masses of sodium hyaluronan were studied, namely 1500-1750 kDa further referred to as high-molecular sodium hyaluronan and 500-750 kDa referred to as low-molecular. The flow and viscosity properties of high-molecular sodium hyaluronate have been studied in the presence of methanol, ethanol, isopropyl alcohol and terc-butanol in the concentration range 0-80 wt. %. Low-molecular sodium hyaluronate, and above all its flow and viscosity properties, were measured in the presence of ethanol and isopropyl alcohol in the concentration range 0-80 wt. %. Based on measured data, viscosities were assessed at infinitesimal stresses consistent with zero-rate viscosity. The high-molecular sodium hyaluronate ranged up to 327 mPas in terc-butanol solution. Viscosity values increased with the increasing length of the alcohol chain. The low-molecular sodium hyaluronate reached a maximum of 39 mPas in an isopropyl alcohol solution. The viscosity curves of low-molecular sodium hyaluronate were close to that of the Newtonian liquid.
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Rheology as a powerful tool for the complex characterization of hydrogels
Kadlec, Martin ; Kráčalík, Milan (referee) ; Smilek, Jiří (advisor)
This diploma thesis investigates the suitability of relaxation tests as a part of complex characterization of hydrogel materials using classical rheology methods. With respect to the current research, creep and three interval thixotropy tests were taken into account. For them, general optimization was done aiming to find an ideal parameter settings. The optimization was performed using physically crosslinked agarose (AG) hydrogel and the tuned tests were also applied to two more samples: hyaluronan (HyA) and polyvinyl alcohol (PVAl) gel. These materials were selected due to their mutually different crosslinking principle. The experiments showed, the AG gel proved to have the best ability to recover after deformation of all studied samples. On the other hand, the HyA gel relaxed the worst. Although the final results of both tests were comparable, the regeneration process itself was different. Hence, the complex relaxation characteristics cannot be described using one of the performed tests alone and both the creep and three interval thixotropy tests have great importance in the scope of complex relaxation behaviour. The obtained results may lead to more precise description of deformation and relaxation, which are frequent phenomena occurring during treatment and application of hydrogel materials.
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