Catanionic vesicles and their complexes with hyaluronan – A way how to tailor physicochemical properties via ionic strength

Abstract

This article offers a comprehensive description of how a change in ionic strength influences the physicochemical properties of dilute solutions of catanionic vesicular systems. Catanionic vesicles are formed from HTMA-DS (hexadecyltrimethylammonium-dodecyl sulphate) ion pair amphiphiles, which were doped by cholesterol and positively charged double-chained surfactant. Due to this positive charge, they can interact with oppositely charged polymers, such as hyaluronan, to form hyaluronan-coated vesicles. Vesicle kinetic stability can be affected by changes in the ionic strength of the environment, which are represented by the addition of sodium chloride. In our study, with the increasing addition of salt, the ζ-potential, as the main parameter of kinetic stability, decreased to zero both for coated and uncoated vesicles. Furthermore, the size of vesicles increased above a concentration of 15 mM NaCl. The membrane rigidity represented by fluorescence anisotropy, of uncoated vesicles decreased rapidly, and slight dehydration of their outer part was observed, which was confirmed by high resolution ultrasonic spectroscopy. Hyaluronan-coated vesicles formed visible aggregates with gradual additions of salt, which were subsequently disintegrated, the degree of disintegration varying for different polymer concentrations. The viscosity of the whole system also decreased significantly with increasing salt concentration.