Effect of different preparation methods on physicochemical properties of salidroside liposomes.

Salidroside liposomes were prepared by using five different methods: thin film evaporation, sonication, reverse phase evaporation, melting, and freezing-thawing. The effect of different preparation methods and salidroside loading capacity on the formation of liposomes and their physicochemical properties were evaluated by means of encapsulating efficiency, particle size, morphology, and zeta potential. Results showed that the encapsulating efficiency of liposomes was highest when prepared by freezing-thawing, followed by thin film evaporation, then reverse phase evaporation and the lowest with melting and sonication. Loading capacity of salidroside had a significant effect on encapsulating efficiency, average diameter, and zeta potential of liposomes. Liposomal systems prepared by sonication, melting, and reverse phase evaporation displayed better dispersivity. Determination of leakage of salidroside from different liposomal systems revealed that the melting method had the lowest leakage of 10% and 15%, at 4 and 30 degrees C after 1 month of storage, respectively. In all cases, a straight-line leakage behavior of salidroside was found. This revealed that the leakage of salidroside was a diffusion process from the membrane of liposomes. Furthermore, the storage stability of different liposomal systems showed that salidroside liposomes prepared by melting had a better physicochemical stability. Instability in the systems was exacerbated when temperature increased. Salidroside liposomes showed the slower increase in particle size than liposomes without salidroside. This could indicate that salidroside played an important role in preventing the aggregation and fusion of liposomes.