3.2. Physicochemical Characteristics of PEGylated Archaeosomes and PEGylated Liposomes As described in the experimental part, formulations have

been prepared using the classical lipid film hydration method followed by vesicle size reduction under sonication. The mean particle size and zeta potential of archaeosomes and liposomes were measured by dynamic light scattering. Particle mean diameters and polydispersity index are gathered in Table 1 and show that both liposomes and archaeosomes Inhibitors,research,lifescience,medical are similar in size, lower than 100nm, with a quite narrow dispersity (around 0.30). In the same way, the mean surface potential of archaeosomes and liposomes were comparable with slightly negative values. These results are in good agreement with several reports [21, 22] that pointed out the impact of the PEG chains on liposomal size decrease and on zeta potential Inhibitors,research,lifescience,medical values close to neutrality. Most importantly, these studies revealed that the atypical structure of the tetraether did not modify the main characteristics of the resulting PEG-grafted vesicle structures (shape, size). Table 1 Size (cumulant results), polydispersity Inhibitors,research,lifescience,medical (Ip), and zeta potential of prepared formulations. (ND = nondetermined). Cryo-TEM

was employed to investigate the morphology of the then vesicles composed of PEGylated lipids. The images in Figure 2 show that PEG-bearing archaeosomes were dispersed and spherical as for classical PEGylated liposomes. The presence of an external dark circle evidenced the lipid layer surrounding the internal aqueous volume of the vesicles. It is noteworthy Inhibitors,research,lifescience,medical that no phase segregation has been evidenced meaning that the prepared formulations are quite homogenous. The sizes of the vesicles were under 100nm and the diameter was comprised between 20 to 100nm, which was in relatively good agreement with data obtained by DLS. Indeed, DLS measurements gave average diameters (cumulant results) lower than 100 nm with objects having diameters ranging from around 20nm to around 200nm. Figure 2 Cryo-TEM photos of (a) Egg-PC/PEG45-Tetraether (90:10wt%) archaeosomes and (b) Egg-PC/PEG45-DSPE (90:10wt%) liposomes. Inhibitors,research,lifescience,medical Bar

is 50nm. Besides these characteristics, it is of great interest to determine the lipid composition after formulation. For that purpose, we have used an innovative method based on quantitative thin layer chromatography, named high performance Dacomitinib thin-layer chromatography (HPTLC). The HPTLC is a qualitative and quantitative analytical method allowing obtaining reproducible and reliable results [23]. This method is used, since several years, for analysis and quantification of lipids extracted from various sources [23–29]. More recently, the use of HPTLC has been developed for the determination of lipid compositions of liposomes [30–34] and for peptide analysis in liposomes [35]. We have, therefore, studied possibilities to use HPTLC for the determination of lipid compositions of the studied liposomes and archaeosomes.