Evaluation of liposomal erythropoietin prepared with reverse-phase evaporation vesicle method by subcutaneous...

We encapsulated erythropoietin (Epo) in dipalmitoylphosphatidylcholine (DPPC) liposomes with soybean-derived sterols (SS-liposomes) and its glucoside (SG-liposomes) by reverse-phase evaporation vesicle method, and evaluated them by subcutaneous administration in rats. With 4 min of sonication, the damage to Epo activity was observed mainly in the non-encapsulated Epo in the liposomes. This study indicated that the bilayer of liposomes had the ability to protect the Epo activity, by reducing the aggregation that was caused by interaction between Epo molecules. The SG-liposomes had a higher retention of the Epo activity the SS-liposomes. 25.3% or 33.6% of activity was retained by SS-liposomes under the conditions of 4 min or 1 min of sonication, while 53.3% or 58.3% of the activity was retained by SG-liposomes under the same conditions. Shorter sonication was available to minimize the loss of the Epo activity. Epo in SG-liposomes appeared to increase the activity.