Evaluation of liposomal formulations containing the antimalarial agent, arteether

Different liposomal formulations containing arteether have been prepared, using the phospholipids, dimyristoyl phosphatidylcholine (DMPC), dipalmitoyl phosphatidylcholine (DPPC), egg phosphatidylcholine (EPC) or dibenhenoyl phosphatidylcholine (DBPC), alone or in mixtures. The effect of presence of arteether on the liposomal physico-chemical characteristics has been investigated. Arteether was found to change the thermotropic behavior of the liposomal phospholipids that contain a saturated acyl chain such as DMPC and DPPC. On the other hand, arteether did not significantly change the thermotropic behavior of EPC liposomes that contain unsaturated phospholipids. The type of the phospholipid as well as the incorporation of cholesterol in the liposomal bilayer was found to alter the trapping efficiency, liposomal particle size and drug release rate from the liposomes. The trapping of arteether in liposomal vesicles was increased by increasing the acyl chain length of the phospholipid and by addition of cholesterol. EPC liposomes exhibited relatively low trapping efficiency, due to high drug adsorption. Interestingly, liposomal particle size showed a decrease with the increase of acyl chain length in the presence of large molecules of arteether. Incorporation of cholesterol in the liposomal bilayer did not alter the liposomal particle size although it gave lower particle size and distribution. The release of arteether from the liposomal system was characterized by a fast phase for 2 days, followed by a slower phase. The fast phase was the highest with EPC liposomes, indicating the release of the adsorbed drug. Generally, the increase of the acyl chain length as well as the addition of cholesterol caused a decrease in the arteether release rate.