Interactions between liposomes and chitosan .2. Effect of selected parameters on aggregation and leakage

The interaction between liposomes and chitosan has been described in an earlier paper. In the present work, the production of liposome-chitosan complexes (Chitosomes) was further studied using factorial designs. The parameters studied were the stirring rate, rate of addition of liposomes to polymer, ionic strength, chitosan quality, lipid/polymer ratio and pH. Particle size, polydispersity and charge were the measured parameters. Cryo-electron microscopy was used for further study of one of the combinations. It was found that the ionic strength, chitosan quality, lipid/polymer ratio and pH had a significant effect on the resulting aggregate size. The leakage of quinine from Chitosomes was compared to the leakage from liposomes using a fractional dialysis method. The leakage rates were similar, but the Chitosomes produced a higher initial release and showed less scattering of the data. Measurements of zeta potential indicated adsorption of quinine to the liposomal membrane. Chitosomes could be stored in a refrigerator for at least 6 months without significant change in particle size. (C) 1997 Elsevier Science B.V.