INTERACTIONS BETWEEN LIPOSOMES AND CHITOSAN .2. EFFECT OF SELECTED PARAMETERS ON AGGREGATION AND LEAKAGE

The interaction between liposomes and chitosan has been described in a n earlier paper. In the present work, the production of liposome-chito san complexes (Chitosomes) was further studied using factorial designs . The parameters studied were the stirring rate, rate of addition of l iposomes to polymer, ionic strength, chitosan quality, lipid/polymer r atio and pH. Particle size, polydispersity and charge were the measure d parameters. Cryo-electron microscopy was used for further study of o ne of the combinations. It was found that the ionic strength, chitosan quality, lipid/polymer ratio and pH had a significant effect on the r esulting aggregate size. The leakage of quinine from Chitosomes was co mpared to the leakage from liposomes using a fractional dialysis metho d. The leakage rates were similar, but the Chitosomes produced a highe r initial release and showed less scattering of the data. Measurements of zeta potential indicated adsorption of quinine to the liposomal me mbrane. Chitosomes could be stored in a refrigerator for at least 6 mo nths without significant change in particle size. (C) 1997 Elsevier Sc ience B.V.