Effect of beta-sitosterol on the characteristics of vesicular gels containing chlorhexidine

Previous studies confirm that beta-sitosterol is very effective in altering the molecular packing of soybean lecithin bilayers even more than the cholesterol. The primary aim of the present study was to evaluate the influence of the beta-sitosterol portion in the lipid bilayer on the physical-chemical characteristics of the prepared gel systems, and its influence on the consequent drug release from the liposomes obtained from vesicular phospholipid gels (VPG-s) by redispersion. VPG-s were prepared of different molar ratios of lecithin:sterol components (10:90-35:65 mol%). The mixture was hydrated with the aqueous solution of chlorhexidin digluconate in order to achieve 30% (w/w) final concentration of the lipid mixtures and 4% (w/w) concentration of the drug in each homogenized VPG sample. To characterize the obtained VPG systems optical microscopic examinations using polarized light, differential scanning calorimetry (DSC), photon correlation spectroscopy (PCS), and dynamic surface tension measurements were carried out. Vertical type diffusion cell was applied to determine the amount of released chlorhexidine digluconate. As a result of the surface tension-decreasing effect of beta-sitosterol, the membrane deformability and the dispersity of the system increased. The increased dispersity and fluidity significantly increased the extent of released chlorhexidine from the vesicles.