Hydrophobic behaviour of liposomal formulations associated to plasmid DNA

NADIA S. CHIARAMONI; LETICIA C. BACCARINI; MARÍA C. TAIRA; SILVIA DEL V. ALONSO

Rosario, Sante Fe, Argentina

Congreso; XXXV Reunión Anual de la Sociedad Argentina de Biofísica; 2006

Biophysics of lipids and biomembranes Study of the hydrophobicity of liposome formulation used for DNA association. Chiaramoni, N.S., Baccarini, L.C., Taira, M.C., and Alonso, S. del V. Laboratory of Biomembranes, Department of Science and Technology, National University of Quilmes. Roque Saenz Peña 352, Bernal. B1876AEO. Buenos Aires. Argentina. e-mail: nschiara@unq.edu.ar The  aim of this is work is to study hydrophobicity of liposome formulation used as DNA vehicles in order to see changes in the surface with the increase of the temperature. In this work we analyzed three liposome formulations: 1)       Cationic Liposomes: 64% of egg yolk phosphocholine (EPC), 32% of 1,2-Dioleoyl-sn-Glycero-3-Phosphoethanolamine (DOPE) and 4% of 1,2-Dioleoyl-3-Trimethylammonium-Propane (DOTAP). DOTAP provide the positive charge to the formulation. (1) 2)       Zwitterionic liposomes: 40 % of EPC, 40 % of 1,2-Dimyristoyl-sn-Glycero-3-Phosphoethanolamine (DMPE) and 20 % of Cholesterol (Chol). 3)       Polymeric Liposomes: 40 % of 1,2-bis(10,12-tricosadiynoyl)-sn-Glycero-3-Phosphocholine (DC8,9PC), 40 % of DMPE and 20 % of Chol. This formulation has also treated with uv light in order to produce iintercatenary double bonds between triple bonds of the DC8,9PC and increase the stability of the vesicle. (2) Hydrophobicity was measured as function of the temperature, using merocyanine 540 as a probe. This dye can particionate between aqueous phase an hydrophobic lipid side chains (3). Non-charged liposomes shown a transition temperature of 48ºC. This is due to the transition of DMPE (50ºC). Cationic liposomes didn´t shown any transition and the incorporation of the probe into the membrane as a function of the temperature was linear. Polymeric liposomes shown a transition in 38ºC. This is due to the non polymerized DC8,9PC transition temperature. Of the three analyzed formulations, cationic liposomes shown the higher hydrophobicity and the higher MC540 incorporation into de membrane. Same assays are going to be performed in the three liposome formulations with plasmid DNA associated. References: (1): Perrie, Y., Frederik, P.M., and Gregoriadis, G. Vaccine, 2001, 19, 3301-3310. (2): Alonso-Romanowski, S, Chiaramoni, N.S., Lioy, V., Gargini, R.A., Viera, L.I., and Taira, M.C. Chem. Phys. Lipids, 2003, 122, 191-203. (3): Disalvo, A., Arroyo, J., and Bernik, D.L. Methods Enzymol, 2003, 367, 213-233.