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Preparation and characterization of triple-IPA for the formation of vesicular systems
Novotná, Ludmila ; Pekař, Miloslav (referee) ; Mravec, Filip (advisor)
This thesis deals with the preparation and characterization of vesicular systems consisting of triple-IPA (ion pair amphiphile with three hydrophobic chains). For the preparation of tripleIPA were used double-chain cationic surfactants dimethyldimyristylammonium bromide (DMSAB), dimethyldipalmitylammonium bromide (DPAB), dimethyldioctadecylammonium bromide (DODAB) and dimethyldioctadecylammonium chloride (DODAC) and the singlechain anionic surfactant sodium dodecyl sulfate (SDS). Among the cationic surfactants, DMSAB and DPAB were selected to be studied more thoroughly. Triple-IPAs were prepared by mixing solutions of oppositely charged surfactants in equimolar ratio, and the resulting triple-IPA precipitate was filtered and dried. From the obtained powder, vesicular systems were prepared by rehydration and sonication. Cholesterol and cationic surfactants, from which the triple-IPAs were prepared, were used to stabilize the cationic vesicles. The properties of the vesicular systems were evaluated by dynamic and electrophoretic light scattering measurements and turbidimetry. The dispersion solutions with the addition of cholesterol were less turbid; therefore, it can be assumed that they supported the formation of cationic vesicles. The optimum cholesterol content is 20 mol. %. At this concentration, the effect of cholesterol on vesicle membrane reorganization becomes apparent and the cationic system remains monodisperse. A positive zeta potential in the stable region was determined for all prepared solutions, which was further increased by the addition of a positive surfactant. The most suitable cationic surfactant for the preparation of triple-IPA is DPAB, which is easy to work with, produces the most monodisperse systems and has the lowest measurement uncertainties.
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Influence of ionic strength on the properties of ionic amphiphilic pairs
Filipová, Lenka ; Smilek, Jiří (referee) ; Mravec, Filip (advisor)
The Bachelor thesis studies catanionic vesicle systems consisting of ion pair amphiphile (IPA) and their properties in the presence of ionic strength. Ion pair amphiphile was prepared from single-chained surfactants: cationic surfactant HTMAB (hexadecyltrimethylammonium bromide) and anionic surfactant SDS (sodium lauryl sulfate). Cationic double-chained surfactant DDAC (dimethyldioctadecylammonium chloride) was added in order to stabilize the vesicle system and make it positively charged. Cholesterol was also added to further stabilize the vesicle system. The system is considered to be relatively stable when consisting of 90 % IPA and 10 % DDAC with 43 mol.% cholesterol in a membrane. The stability of the system can be disrupted by external factors such as ionic strength. The Ionic strength was induced by NaCl solutions of varying concentrations (0.0, 0.5, 1.0, 2.0, 50.0, 100.0, 150.0 and 300.0 mM). The change of properties of a vesicle system, which was induced by ionic strength, was analyzed by electrophoretic and dynamic light scattering, fluorescence anisotropy, and generalized polarization. –potential was obtained by electrophoretic light scattering analysis which determines the stability of the system. Dynamic light scattering measurement resulted in the determination of the size of vesicles. The fluidity of vesicles’ membranes was examined by fluorescence anisotropy with DPH (1,6-diphenyl-1,3,5-hexatriene) as a probe. The hydration shell of vesicles was observed by generalized polarization with Laurdan (2-(dimethylamino)-6-dodecanoylnaphthalene) as a probe. As a result, it was found out that low ionic strength (0.5 to 2.0 mM) causes a decrease in the size of vesicles and high ionic strength (50.0 to 300.0 mM) causes vesicles to grow in size. –potential showed a consistent trend for the whole concentration series – its value rapidly decreasing with increasing ionic strength. The samples with the concentrations of salt 50.0 to 300.0 mM were considered unstable according to the –potential data. Fluorescence anisotropy decreases with increasing temperature and increasing ionic strength. The value of generalized polarization decreases with increasing temperature; hence there is more solvation of a vesicle membrane. The highest value of generalized polarization was measured when the concentration of sodium chloride was relatively high (from 50.0 to 300.0 mM), as a result of which the membrane was less hydrated and therefore, more organized.
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Preparation and characterization of triple-IPA for the formation of vesicular systems
Novotná, Ludmila ; Pekař, Miloslav (referee) ; Mravec, Filip (advisor)
This thesis deals with the preparation and characterization of vesicular systems consisting of triple-IPA (ion pair amphiphile with three hydrophobic chains). For the preparation of tripleIPA were used double-chain cationic surfactants dimethyldimyristylammonium bromide (DMSAB), dimethyldipalmitylammonium bromide (DPAB), dimethyldioctadecylammonium bromide (DODAB) and dimethyldioctadecylammonium chloride (DODAC) and the singlechain anionic surfactant sodium dodecyl sulfate (SDS). Among the cationic surfactants, DMSAB and DPAB were selected to be studied more thoroughly. Triple-IPAs were prepared by mixing solutions of oppositely charged surfactants in equimolar ratio, and the resulting triple-IPA precipitate was filtered and dried. From the obtained powder, vesicular systems were prepared by rehydration and sonication. Cholesterol and cationic surfactants, from which the triple-IPAs were prepared, were used to stabilize the cationic vesicles. The properties of the vesicular systems were evaluated by dynamic and electrophoretic light scattering measurements and turbidimetry. The dispersion solutions with the addition of cholesterol were less turbid; therefore, it can be assumed that they supported the formation of cationic vesicles. The optimum cholesterol content is 20 mol. %. At this concentration, the effect of cholesterol on vesicle membrane reorganization becomes apparent and the cationic system remains monodisperse. A positive zeta potential in the stable region was determined for all prepared solutions, which was further increased by the addition of a positive surfactant. The most suitable cationic surfactant for the preparation of triple-IPA is DPAB, which is easy to work with, produces the most monodisperse systems and has the lowest measurement uncertainties.
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Study of membrane properties of catanionic vesicles from new SEPT-DS amphiphilic ion pairs
Vajcíková, Katarína ; Krouská, Jitka (referee) ; Mravec, Filip (advisor)
This work describes the possibility of determining the membrane properties of vesicular systems formed by ion pair amphiphile (IPAs), which were prepared by mixing positively and negatively charged surfactants, namely the positively charged surfactant carbethopendecinium bromide (Septonex) and negatively charged surfactant sodium dodecyl sulphate with the addition of dioctadecyldimethylammonium chloride and cholesterol for stability enhancement. Such systems are potential drug carriers and hence their careful characterization is very important for further research. In this work, the possibilities of studying the membrane properties of such systems using spectrometric methods, namely fluorescence anisotropy and generalized polarization, by which the fluidity and solvation of the bilayer membrane were detected as a function of the amount of added cholesterol and the change in temperature, are described. The size and stability of the prepared vesicular systems formed from the new amphiphilic pairs were investigated by dynamic and electrophoretic light scattering, and finally, the phase transition temperature was detected using differential scanning calorimetry method.
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Influence of ionic strength on the properties of ionic amphiphilic pairs
Filipová, Lenka ; Smilek, Jiří (referee) ; Mravec, Filip (advisor)
The Bachelor thesis studies catanionic vesicle systems consisting of ion pair amphiphile (IPA) and their properties in the presence of ionic strength. Ion pair amphiphile was prepared from single-chained surfactants: cationic surfactant HTMAB (hexadecyltrimethylammonium bromide) and anionic surfactant SDS (sodium lauryl sulfate). Cationic double-chained surfactant DDAC (dimethyldioctadecylammonium chloride) was added in order to stabilize the vesicle system and make it positively charged. Cholesterol was also added to further stabilize the vesicle system. The system is considered to be relatively stable when consisting of 90 % IPA and 10 % DDAC with 43 mol.% cholesterol in a membrane. The stability of the system can be disrupted by external factors such as ionic strength. The Ionic strength was induced by NaCl solutions of varying concentrations (0.0, 0.5, 1.0, 2.0, 50.0, 100.0, 150.0 and 300.0 mM). The change of properties of a vesicle system, which was induced by ionic strength, was analyzed by electrophoretic and dynamic light scattering, fluorescence anisotropy, and generalized polarization. –potential was obtained by electrophoretic light scattering analysis which determines the stability of the system. Dynamic light scattering measurement resulted in the determination of the size of vesicles. The fluidity of vesicles’ membranes was examined by fluorescence anisotropy with DPH (1,6-diphenyl-1,3,5-hexatriene) as a probe. The hydration shell of vesicles was observed by generalized polarization with Laurdan (2-(dimethylamino)-6-dodecanoylnaphthalene) as a probe. As a result, it was found out that low ionic strength (0.5 to 2.0 mM) causes a decrease in the size of vesicles and high ionic strength (50.0 to 300.0 mM) causes vesicles to grow in size. –potential showed a consistent trend for the whole concentration series – its value rapidly decreasing with increasing ionic strength. The samples with the concentrations of salt 50.0 to 300.0 mM were considered unstable according to the –potential data. Fluorescence anisotropy decreases with increasing temperature and increasing ionic strength. The value of generalized polarization decreases with increasing temperature; hence there is more solvation of a vesicle membrane. The highest value of generalized polarization was measured when the concentration of sodium chloride was relatively high (from 50.0 to 300.0 mM), as a result of which the membrane was less hydrated and therefore, more organized.
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