Study of cholesterol’s effect on the properties of catanionic vesicular systems: comparison of light-scattering results with ultrasonic and fluorescence spectroscopy

Abstract

This work is focused on the study of properties associated with the effect of cholesterol levels on the stability of vesicular systems based on the ion pair amphiphile hexadecyltrimethylammonium-dodecylsulphate (HTMA-DS) at laboratory temperature. The HTMA-DS catanionic system was doped with dioctadecyldimethylammonium chloride in a 9:1 molar ratio and cholesterol in the amount of 0, 3, 13, 23, 33, 43, 53, 63, and 73mol.% was added. In this system, the size distributions were studied using the dynamic light-scattering technique and the zeta potential was determined. These standard techniques were supplemented by ultrasonic and fluorescence spectroscopy techniques. Due to low stability and high opalescence of samples, spectral techniques were used only for the samples with cholesterol content above 23mol.%. The results from High-Resolution Ultrasonic Spectroscopy and from Fluorescence Spectroscopy are in agreement. They equally point to a change in the amount of hydration water in the membrane, the largest amount of which is present in the samples with 43 and 53mol.% cholesterol. Using the light-scattering technique, the short-term stability of prepared vesicular systems was also observed over the first 36 days. Obtained results confirmed that the most stable systems are those containing 43 or 53mol.% of cholesterol.