|
|
Study of interaction of charged catanionic vesicles with oppositely charged polyelectrolytes
Havlíková, Martina ; Lehocký, Marián (referee) ; Táborský, Petr (referee) ; Mravec, Filip (advisor)
The presented dissertation is focused on positively charged catanionic vesicles and their interactions with oppositely charged hyaluronan. The catanionic vesicles were composed of ion pair amphiphile of hexadecyltrimethylammonium-dodecyl sulfate (HTMA-DS), a positively charged double-chain surfactant that electrostatically stabilized the vesicles and cholesterol. Cholesterol may strongly affect the physico-chemical properties of the vesicles, therefore it was necessary to determine its optimal amount in the membrane. Especially, the size and stability of vesicles were studied by dynamic and electrophoretic light scattering, membrane microviscosity by fluorescence anisotropy and hydration of the outer part of the membrane by generalized polarization. It was found that vesicles show ideal properties at a cholesterol content about 40 mol.%. These catanionic vesicles interacted with hyaluronan regardless of its molecular weight. Visible aggregates were observed around their isoelectric point, but they disintegrated with increasing polymer concentration. However, this decay was different for different hyaluronan molecular weights. An increase in ionic strength, or more precisely concentration of sodium chloride above 25 mM had a destabilizing effect on both uncoated and hyaluronan coated vesicles. It was also interesting that increasing the ionic strength affected the microviscosity of the membrane, which became more fluid, but there were no significant changes in the hydration of its outer part. The presented work is also focused on the preparation and characterization of a new type of catanionic vesicles, where the cationic surfactants HTMAB was replaced by Septonex. The same methods were chosen for their characterization as in the case of the HTMA-DS vesicles. This exchange of surfactants had a major effect on the resulting properties of the vesicles, which are stable even at very low cholesterol content. In accordance with long-term stability, a suitable concentration of cholesterol was chosen from 15 mol.% and higher.
|
|
|
Stability of vesicular complexes against changes in their concentration
Velichová, Veronika ; Marková, Kateřina (referee) ; Mravec, Filip (advisor)
This bachelor thesis is focused on the stability of vesicular systems that consist of ion pair amphiphile. These catanionic vesicles were prepared from single-chained surfactants CTAB cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulphate), which were stabilized by adding double-chained surfactant DODAC (dimethyldioctadecylammonium chloride) with 43 mol.% cholesterol. The aim of the thesis was to verify the stability of vesicular systems against changes in their concentration. For the measurement, a concentration series was prepared by diluting vesicles with deionized water. The stability was evaluated by dynamic (DLS) and electrophoretic (ELS) light scattering measurements at weekly intervals for four weeks. By DLS method were determined the average values of the size of vesicles and their changes during the measurement, the method ELS provided the information about changes of charge with different concentration in time. Samples with a higher concentration, i.e. no dilution till tenfold dilution of the vesicle solution, were marked as stable, higher values of average sizes and lower values of zeta potential were measured at solution with lower concentrations, according to which such diluted vesicles can be described as unstable. There were also visual observations made, but no visible aggregation in the solutions was observed. Furthermore, the aggregation behavior of the vesicles was observed by fluorescence spectroscopy using pyrene as fluorescent probe.
|
|
|
Microcalorimetric study of interactions between hyaluronan and catanionic vesicular systems
Mach, Jakub ; Pekař, Miloslav (referee) ; Krouská, Jitka (advisor)
Properties of surfactants in water, interactions between oppositely charged surfactants and interactions in system containing didecyldimethylammonium chloride (DDAC), hyaluronan and ion pair amphiphile (IPA) have been studied using isothermal titration calorimetry. For the study of properties of surfactants in water and their mutual interactions, two cationic surfactants have been chosen, namely cetyl trimethylammonium bromide (CTAB) and carbethopendecinium bromide (Septonex), and an anionic surfactant sodium dodecyl sulfate (SDS). For hyaluronan, a molecular weight of 250 450 has been chosen. Critical micelle concentration of the chosen surfactants and enthalpy of the investigated interactions have been determined using the TAM III calorimeter. To prove the interactions in system containing hyaluronan, DDAC and IPA and to determine enthalpy the Microcal PEAQ-ITC calorimeter has been used.
|
|
|
Catanionic vesicular systems
Repová, Romana ; Krouská, Jitka (referee) ; Mravec, Filip (advisor)
This bachelor thesis deals with catanionic vesicles. The aim of the study was to prepare and characterize these systems. The catanionic vesicles are composed of cationic (CTAB, CTAC, TTAB, DTAB) and anionic surfactants (SDS). The physical stability of the vesicles was enhanced with the addition of cationic surfactant DODAC.The catanionic vesicles were characterized by the measurement of the dynamic light scattering, zeta potencial and fluorescence correlation spectroscopy. The size and stability of the system were determined using dynamic light scattering. Difussion coefficient of the system was analyzed using fluorescence correlation spectroscopy.
|
|
|
Solubilization of water-insoluble vitamins into vesicular systems based on ionic amphiphilic pairs
Kolomá, Nikola ; Mravcová, Ludmila (referee) ; Mravec, Filip (advisor)
This thesis deals with the characterization and preparation of catanionic vesicular systems and their interaction with water-insoluble vitamins. Catanionic vesicles systems was prepared from two differently charged sufractants CTAB and SDS in formation ion pair amphiphile. Stability of vesicles was secured by adding cholesterol with positively charged surfactant DODAC. Were selected vitamin A and vitamin E for solubilization into these vesicles. The next part of this work was focused on determining the efficiency of incorporation these vitamins into the HTMA-DS vesicular system. The characterization of these systems was improved by measurement on a UV-VIS spectrometer, DLS and by HPLC with UV-VIS detector. During measurement by UV-VIS and HPLC the efficiency of solubilization of vitamin A and vitamin E into vesicles was determinated. In both cases higher efficiency was determinated for vesicles with incorporated vitamin A. Higher efficiency for both vitamins was determinated by HPLC. The reason is probably the higher sensitivity of the metod, work in labs with dark glass and preparing individuals samples into vials, which were inserted into the device for individual dosing by injector. The work serves primary evaluation results in view of the vesicular system for use in pharmaceutical application like carrier non-polar vitamins.
|
|
|
Study of microviscosity of membrane systems based on ionic amphiphilic pairs
Moslerová, Lenka ; Venerová, Tereza (referee) ; Mravec, Filip (advisor)
In this master ‘s thesis, catanionic vesicles formed by the pseudo-double-chain complex CTA – DS were investigated from the point of view of microviscosity. Samplesand of cationic vesicles contained 23, 43 and 53 mol. % of cholesterol and the double-chain surfactant DODAC. Cationic vesicles were prepared for visual observation, their stability was determined by DLS and the prepared system was further investigated. Microviscosity was determined from fluorescence anisotropy. To study the outer part of the membrane, laurdan fluorescent probes were used whereas diphenylhexatriene was used for the inner part of the membrane. This method has been proven to be suitable because it reflects the conditions of the membrane. Moreover, a 1,3-bispyrenylpropane probe forming intramolecular excimers was used to study the microviscosity in the vesicle bilayer. The dicyanovinyljulolidine (DCVJ) probe was applied in the case of the molecular rotor technique. It has been shown that in the case of the DCVJ probe, the molecular rotor technique is practically unusable, due to the fact that the probe has a low quantum yield at low temperatures. Also, the excimer formation of P3P probes does not lead to the expected results. The cationic vesicles do not seem to support this formation, as they are too closely related. This type of probe can be used for the selected system with some restrictions.
|
|
|
Solubilization in catanionic surfactant systems
Konečná, Anna ; Krouská, Jitka (referee) ; Mravec, Filip (advisor)
This bachelor thesis deals with the solubilization of hydrophobic dyes in systems of positively charged catanionic vesicles. The aim of the work was to determine their solubilization capacity. Vesicular systems were prepared from oppositely charged surfactants CTAB and SDS. To increase the stability of the vesicles, cholesterol and the positively charged double-chain surfactant DODAC were added to their structure. DODAC also gave the system a positive charge. To determine the solubilization capacity, the dyes 1-Naphthol, Sudan Red G and Oil Red O were used. For sample preparation two methods were used, spontaneous and direct solubilization. The measurement was performed after 1, 2, 3 and 7 days from the preparation of the samples by UV-VIS spectrophotometry. The solubilization capacity was determined from the measured absorbance by calculation from the calibration curves. The results indicate that direct solubilization is slightly more effective than spontaneous solubilization. Of the selected dyes, 1-Naphthol is the substance with the smallest molecule, and therefore it seems to be 100% solubilized in the vesicle system.
|
|
|
Study of the hydration shell of vesicular systems based on ionic amphiphilic pairs
Rašticová, Barbora ; Szabová, Jana (referee) ; Mravec, Filip (advisor)
This bachelor thesis deals with the study of hydration shell of positively charged vesicular systems. The aim of the work was to monitor the hydration shell and to find out the amount of water molecules in the environment at different conditions of the membrane. Furthermore, a comparison of two selected fluorescent probes were studied. Positively charged vesicular systems composed of two types of surfactants were used, namely negatively charged SDS and positively charged CTAB. The two-chain positively charged surfactant was also added, resulting a positively charged vesicular systems. Three different concentrations of cholesterol were selected for the study and added to the system, namely 20, 40 and 60 mol. %. The study was performed by measuring the fluorescent emission as a function of temperature. The temperature range was from 10 to 80 °C. As a fluorescent probe Laurdan and Prodan were selected. For evaluation the method of generalized polarization was used. Due to its structure, Laurdan is mainly found in the membrane environment, so the method of two-wavelength generalized polarization, which includes fluorescence contributions only from the membrane, was sufficient for its evaluation. Compared to Laurdan, Prodan has a shorter hydrocarbon chain, so its distribution is not only in the membrane but also in the aqueous environment. Therefore, the method of three-wavelength generalized polarization, which also includes the contribution of fluorescence from the aqueous environment was used. The results showed that the behaviour of both probes is very similar. In all systems, the values of generalized polarization decreased with increasing temperature. Thus, at low temperatures, the membrane is in a solid ordered phase. With increasing temperature, it transforms into a liquid disordered phase. Thus, with increasing temperature, the number of water molecules increases. As the cholesterol concentration increased, the phase transition interval increased. The results also showed that the values of Prodan’s three wavelength generalized polarization are always higher than the values of Laurdan’s two wavelength generalized polarization.
|
|
|
Influence of dispersion parameters on formation of vesicular systems
Vajcíková, Katarína ; Smilek, Jiří (referee) ; Mravec, Filip (advisor)
The work describes a method for the preparation of catanionic vesicular systems using the method of ultrasonic dispersion in order to find the most suitable parameters for the preparation of a system with long–term physical stability. The parameters compared were the amplitude of the ultrasonic wave, the energy used for dispersion, and the volume of deionized water used to prepare a system consisting of the negatively charged surfactant sodium dodecyl sulfate and the positively charged surfactant hexadecyltrimethylammonium bromide. To increase stability and provide a positive charge, the surfactant dimethyldioctadecylammonium chloride was used and cholesterol was also added to increase stability. The individual systems were compared over time because of their size, zeta potential and turbidity of the solution. Particle size and polydispersity coefficient were measurement by the dynamic light scattering method. The zeta potential was determined by electrophoretic light scattering, and the turbidity was monitored by UV-VIS spectrophotometry based on the measurement of turbidity. The results present the most suitable parameters of ultrasonic dispersion using Bandelin SONOPULS UW 3200. The use of these parameters shows the emergence of systems with long–term physical stability, which means that they can be used for other applications.
|
|
|
Effect of changing ionic strength on the properties of catanionic vesicles from HTMA-DS
Filipová, Lenka ; Klučáková, Martina (referee) ; Mravec, Filip (advisor)
This diploma thesis is focused on evaluating the influence of ionic strength on catanionic vesicules made of ion pair amphiphile (IPA) in the form of HTMA-DS (hexadecyltrimethylammonium-dodecyl sulphate). Catanionic vesicles were stabilized by the addition of cationic surfactant dioctadecyldimethylammonium chloride (DODAC) and cholesterol. The ionic strength was attained by adding CaCl2 and Na2SO4 salts in the concentrations 0–300 mM. The changes influenced by ionic strength were studied by dynamic and electrophoretic light scattering (DLS and ELS), fluorescence anisotropy, generalized polarization (GP), pH measurement, and visual observation. During this experiment, the temperature was set both constant and altering in time. The measurement was performed shortly after adding salts to the catanionic vesicles and in-time measurement was performed as well. This thesis follows a bachelor thesis, where the influence of NaCl on the same type of catanionic vesicles in the same range of ionic strength was studied. The CaCl2 and Na2SO4 influences were then compared to the NaCl according to Hofmeister series. By the DLS and ELS method it was found that the size of vesicles with added CaCl2 and Na2SO4 was decreasing at first and then increasing whereas the -potential was exponentially decreasing with increasing ionic strength. The vesicle size, when the ionic strength was applied, was increasing in time while -potential was almost constant in time. The addition of both salts caused slight dehydration of the external part of the membrane which was examined by the fluorescent probe Laurdan (6-dodecanoyl-2-dimethylamino-naphthalene) and generalized polarization. By fluorescence anisotropy with the probe DPH (1,6-diphenyl-1,3,5-hexatriene), it was detected that both salts caused an increase of the fluidity of an inner part of a membrane. By both of the fluorescent techniques, it was confirmed that the increase in temperature caused a phase transition of the membrane from the solid ordered through the liquid ordered phase to the liquid disordered phase. The pH values also did not show any change with the addition of salts. When comparing the salts’ influence (CaCl2 and Na2SO4 versus NaCl) on catanionic vesicles it was found that in most cases NaCl influenced the observed properties the most. The addition of NaCl caused the largest increase in vesicle size, highest -potential values, initial dehydration of the external part of the membrane, and increased fluidity of the inner part of the membrane at I > 15 mM. These results are in agreement with the Hofmeister series. Based on the visual observation, the samples with ionic strength of more than 150 mM for CaCl2 and 75 mM for Na2SO4 were said to be unstable. This fact is in agreement with the result of ELS. The rest of the samples did not show any visual changes in time (28 days). Additionally, the influence of PBS buffer on catanionic vesicles at the same ionic strength values was studied. PBS buffer simulates the ionic environment of living organisms. Its' influence was characterized by the same methods under the same conditions as mentioned above. The effect of PBS on catanionic vesicles displayed almost the same behaviour in the observed properties. During this experiment, it was also found that the PBS influence on the studied properties was more significant than the influence of CaCl2, Na2SO4, and NaCl salts. Influence of PBS was most similar to the effect of NaCl on catanionic vesicles.
|
guest ::
