Modified and derived ethanol injection toward liposomes: development of the process

Abstract

A modified and derived ethanol injection (MDEI) process was developed to produce liposomes. The aim of the present study was to more efficiently control the vesicle diameter than with the conventional ethanol injection method. A hot ethanolic solution of lipids (60°C) was injected into a hot aqueous buffer (70°C). Then, ethanol was removed by rotary evaporation under reduced pressure. The size of the liposomes could be controlled by the ratio of ethanol to hydroalcoholic solution before evaporation. The concentration of lipids, the charge of lipids, and the type of aqueous phase had little effect on the vesicle diameter when the process involved a ratio of 33% (v/v) ethanol. In addition, it was possible to obtain lipid concentrations 10- to 30-fold higher that the conventional ethanol injection method. The encapsulation of a hydrophilic compound was feasible with this MDEI process. The observation by cryogenic transmission electron microscopy revealed that these liposomes were predominantly unilamellar at a ratio as high as 33 or 50% (v/v) ethanol. Thus, the results showed that MDEI is an appropriate alternative for the manufacture of liposomes with respect to the ethanol injection process.

Keywords::

• Ethanol injection
• vesicle diameter
• cryo-TEM

Acknowledgments

The authors thank Corinne Crucifix for assistance with cryo-TEM experiment realization, Gabrielle Heinimann and Ahinsa Jheelan for technical assistance and advice, and also Dr. Salman El Habib for proofreading the manuscript for this article.

Declaration of interest

The authors gratefully acknowledge financial support from Université de Strasbourg, Centre National de la Recherche Scientifique (CNRS).