The effects of polyoxyethylene cetyl ethers, cholesterol, fatty alcohol on the stability of egg lecithin liposomes were investigated, observing the droplet size, light absorbance of vacant liposomes and carboxyfluorescein release from entrapped liposomes.
The particle size and absorbance of liposome alone increased along the time duration, indicating that droplets unstable in nature coalesced to decrease Gibbs free energy. In surfactant systems, the size and absorbance of liposomes decreased depending on the lecithin surfactant ratio because of the formation of mixed layer or the solubilization of lecithin molecule in bilayer.
Carboxyfluorescein encapsuled in pure liposome was released more rapidly by surfactants, but the release of carboxyfluorscein entrapped by liposomes with cholesterol or fatty alcohol were significantly delayed. Especially liposomes incorporated with mixture of cholesterol and cetyl alcohol slowly released the entrapped carboxyfluorescein through the membrane because of the density of bilayer and the flexibility of membrane modified by the constituents and their concentrations.