Preparation of liposomes: A comparative study between the double solvent displacement and the conventional ethanol injection From laboratory scale to large scale

Here, we propose a new method for lipid vesicles preparation: double solvent displacement. Influence of various parameters on colloidal properties was studied to assess scale-up performances in comparison with ethanol injection. Lipid vesicles were prepared by double solvent displacement (DSD). The first one was performed in non-aqueous media, only with an ethanol phase containing phospholipids dispersed in PEG400. The second one consisted of a dispersion of the previous mixture in an aqueous phase containing glycerin. Our results showed that double solvent displacement could be able to produce large amount of small and homogeneous lipid vesicles. With such method, we could use higher phospholipids concentrations without significantly affecting vesicle colloidal properties compared to ethanol injection. Indeed, for concentrations higher than 12.5 mg/ml, we observed a continuous size increase (from 129 54 nm to 318 220 nm) associated with a higher heterogeneity of the population whereas results remained stable for the DSD technique (size between 123 57 nm and 141 67 nm, respectively). DSD technique allowed preserving colloidal properties over a large range of solvent/non solvent (S/NS) ratios. Scale-up studies showed more pronounced impact with ethanol injection technique for which colloidal properties were more altered. Indeed, size decreased significantly by 11.8% compared to DSD for which the increase was just about 3.5%. The latter appeared to be more easily scalable than ethanol injection. The simplicity and the rapidity of this new technique enable us to produce liposomes with good proficiency of the process offering high yield while keeping economically attractive. (C) 2017 Elsevier B.V. All rights reserved.