Preparation of Asymmetric Charged Large Unilamellar Vesicles Containing Both Cationic and Anionic Lipids

Abstract

Liposomes have important applications for drug delivery. Whether asymmetric large unilamellar vesicles (asymmetric LUVs) with different charges on different leaflets can be efficiently prepared and have practical applications have advantages for efficient drug encapsulation and efficiency has not been explored. To examine this we have developed methods to prepare asymmetric LUV with opposite charges on the inner and outer leaflet. We investigated liposomes mixtures containing one of three different kinds of negative charged lipids, POPG, POPS and POPA, one of two different kinds of positive charged lipids, POePC and DOTAP, and a zwitterionic lipid, POPC. Using the cyclodextrin (CD) assisted exchange methods developed by our group, we have prepared asymmetric LUVs with about 25 % of POPS or POPA in the outer or inner leaflet (monolayer) and about 25 % of POePC or DOTAP on the opposite leaflet, with about 75 % of lipids in each leaflets being POPC. Exchange with POPG was somewhat less efficient. To investigate asymmetry of the LUVs a TMA-DPH binding assay was developed. Future studies will investigate drug entrapment ability and the efficiency of drug delivery using these liposomes.