Preparation of liposomes by reverse-phase evaporation using alternative organic solvents

The organic solvents employed in liposome preparation, such as chlorinated solvents, diethyl ether or methanol, although usually removed by evaporation, may remain as traces in the final formulation representing a possible risk for human health and influencing the stability of the vesicles. In order to tentatively solve the above mentioned disadvantage, in the present paper we describe the possible use of different organic solvents, namely ethanol, ethyl acetate and two mixtures of ethanol/ethyl acetate, for the production of liposomes by reverse phase evaporation technique. After preparation, liposomes were extruded through polycarbonate filters and then characterized by dimensions and encapsulation efficacy. As model drugs retinyl acetate and sodium cromoglycate have been used. The association and the encapsulation yield for both hydrophobic and hydrophylic model drugs were found in all the liposome preparations satisfactory. In particular, the use of more polar organic solvents (with respect to diethyl ether) appear to enhance the encapsulation of the hydrophilic drug cromoglycate. In conclusion, the use alternative organic solvents to diethyl ether can be efficiently proposed with the aim to reduce the toxic problems associated with the presence of residual traces of organic solvents in the final liposome formulation.