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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.
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