Chemistry and Physics of Lipids 140 (2006) 88–97 Study and formation of vesicle systems with low polydispersity index by ultrasound method J. Pereira-Lachataignerais a,∗ , R. Pons a , P. Panizza b , L. Courbin b , J. Rouch b , O. L ´ opez a a Departamento de Tecnolog´ ıa de Tensioactivos, Instituto de Investigaciones Qu´ ımicas y Ambientales de Barcelona (I.I.Q.A.B.)-Consejo Superior de Investigaciones Cient´ ıficas (C.S.I.C.), Calle Jorge Girona 18-26, 08034 Barcelona, Spain b Centre de Physique Mol´ eculaire Optique et Hertzienne (CPMOH), Universit´ e de Bordeaux I, Centre National de la Recherche Scientifique (CNRS), 351, Cours de la Liberation, 33400 Talence, France Received 25 February 2005; received in revised form 25 January 2006; accepted 25 January 2006 Available online 21 February 2006 Abstract The formation of liposomes with low polydispersity index by application of ultrasounds was investigated considering method- ology specifications such as sonication time and sonication power. Phosphatidylcholine (PC) liposomes were formed by the evaporation–hydration method. The vesicles were sonicated using several sonication conditions. The liposomes were then charac- terized by dynamic light scattering (DLS) and freeze-fracture electron microscopy (FFEM). Correlation functions from DLS were treated by cumulants method and GENDIST to obtain the mean radius and polydispersity index. These calculations allowed to fix an optimal sonication time (3000 s) and a useful interval of ultrasound power between 39 and 91 W. DLS and FFEM results confirmed that vesicle size, lamellarity and the polydispersity index decreased with the increase of sonication power. Thus, we propose a systematic method to form liposomes in which the physical characteristics of the vesicles may be controlled as a function of sonication time and power. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Liposome; Ultrasound; Freeze-fracture electron microscopy; Dynamic light scattering 1. Introduction Liposomes or lipid bilayer vesicles have been the subject of numerous studies because of their impor- tance as models for more complex biological mem- branes, their potential use as microencapsulators for drug Abbreviations: DLS, dynamic light scattering; FFEM, freeze- fracture electron microscopy; PC, phosphatidylcholine; PI, polydis- persity index ∗ Corresponding author. Tel.: +34 93 400 61 00x301; fax: +34 93 204 59 04. E-mail address: jplten@iiqab.csic.es (J. Pereira-Lachataignerais). delivery and their applications in cosmetics (Sackmann, 1995; Gregoriadis, 1995; Teschke and de Souza, 2002). Depending on the preparation methods, these self- assembled macromolecular aggregates can exist as uni- or multilamellar lipid bilayer systems (Baszkin and Norde, 2000). Some of these methods are based on the removal of surfactant from phospholipid–surfactant mixed micelles by dialysis (Classen and Spooner, 1995) or by dilution (New, 1990). However, the complete removal of surfactant from the resulting vesicles is diffi- cult and dependent on the type of surfactant (Ollivon et al., 2000). This problem is eliminated by use of methods that do not involve the lipid–surfactant mixture. Thus, 0009-3084/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.chemphyslip.2006.01.008