[Effects of liposomes formulation and preparation method on the stability of acyclovir palmitate liposomes]

To study the effects of various liposomes formulations and preparation methods on the stability of acyclovir palmitate (ACV-C16) liposomes on storage at 4 degrees C and 25 degrees C over a 6 months period.

The mean particle size, Zeta potential, pH and leaking ratio of ACV-C16 liposomes were the parameters chosen to indicate the stability of liposomes. All of the parameters were compared among various lipid compositions [egg lecithin/cholesterol/hosphatidylserine (PC/CH/PS), egg lecithin/cholesterol/stearylamine (PC/CH/SA), egg lecithin/cholesterol/cholesteryl sulphate (PC/CH/CS), bovine brain ceramides/cholesterol/palmitic acid/cholesteryl sulphate (CM/CH/PA/CS)], different preparation methods (film dispersing, reverse phase evaporation, dehydration/rehydration), charges (positive, negative), as well as among multilamellar vesicles liposomes (MLV), large unilamellar vesicles liposomes (LUV) and dehydration/rehydration vesicles liposomes (DRV).

An analysis of various parameters led to the conclusion that the stability of liposomes followed the order of PC/CH/CS > CM/CH/PA/CS > PC/CH/PS > PC/CH/SA at the same storage conditions; the positively charged system showed the most unstable delivery system of liposomes as compared to the other three systems. As far as stability was concerned, LUV liposomes proved to be superior to MLV liposomes and DRV liposomes, and the modified reverse phase evaporation method of Szoka provided the best preparation method. The stability in systems was enhanced when systems were stored at 4 degrees C as compared to storage at 25 degrees C.

The stability of liposomes was significantly interrelated with lipid composition of various liposomes, preparation method and different storage conditions.