Abstract: To improve the encapsulation efficiency and minimize particle agglomeration of liposomes, rapid expansion from supercritical to surfactant solution(RESSS) was applied to self-assembly of liposomes entrapping hinesol in supercritical carbon dioxide(SC-CO₂) medium. In the process, the solution of liposomal materials and hinesol dissolved in the mixture of SC-CO₂/ethanol was sprayed into a surfactant solution. The surfactant provided stabilization for liposomes by preventing bubbles overflowing and liposomes agglomeration during the spraying process. The encapsulating performance and particle size distribution of liposomes could be controlled by changing expansion processing conditions. When the solution was sprayed into a 5.0% Poloxamer l88 solution at a flow rate of 2 L/min, the entrapment efficiency and average particle size of liposomes were found to be 88.26% and 124 nm, respectively, which came to the standards of Chinese pharmacopoeia. The results show RESSS process provides an innovative method for formation of liposomes incorporating valid compositions extracted from the Chinese traditional medicines in SC-CO₂ medium.

Key words: Liposome, Hinesol, Supercritical carbon dioxide, Rapid expansion, Surfactant