Liposome/Surface charges: Their interaction with serum proteins and influence on citotoxicity

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

Montevideo, Uruguay

Congreso; 6th International Conference of Biological Physics, 5th Southern Cone Biophysical Congress, 34th Annual Meeting of the Argentinean Biophysical Society, ICBP 2007; 2007

Liposomes/Surface Charges: “Their interaction with serum proteins and influence on cytotoxicity”. Baccarini, L.C., Chiaramoni, N.S., Taira, M.C., and Alonso, S. del V. Laboratory of Biomembranes, Department of Science and Technology  Universidad Nacional de Quilmes. Roque Saenz Peña 352, Bernal. B1876BXD. Buenos Aires. Argentina. e-mail: leticiabaccarini@hotmail.com  Citotoxicity of different liposomal formulations have been studied as possible DNA delivery system. Studies were performed with and without fetal bovine serum. We analyzed three different formulations: cationic (EPC:DOPE:DOTAP 16:8:1 molar-ratio); non-charged (EPC:DMPE:Chol 2:2:1 molar-ratio) and polymeric (DC8,9PC:DMPE:Chol 2:2:1 molar-ratio).  Data show that polymeric and non-charged liposomes were more citotoxic with serum. This trend was not followed by cationic liposomes. Interactions between serum proteins and these liposomal formulations were analyzed. Serum protein concentration was determined with Branford’s method. Then different ratios of liposomes were mixed with a constant concentration of serum proteins (1:1 and 1:10 protein:liposome ratio). The protein-liposome association was centrifuged and separated. SDS-PAGE was used to analyze these interactions: proteins were separated on 12 and 7.5% of polyacrylamide. Serum proteins establish a better interaction with non-charged and polymeric liposomes.  Cationic liposomes showed weak interactions with serum protein, this could be anticipated because citotoxicity with and without serum was not significantly different. On the other hand, polymeric liposomes exhibited major interactions as compared with non-charged. Both of them presented a high citotoxicity. In fact, this can be explained by two hypotheses: liposomes captured proteins or formation of macromolecular complexes with differential hydrophobicity. To elucidate which hypothesis is the most relevant membrane –water interface of the liposome systems were studied to gain insight if a correlation could be made between hydrophobic modifications and serum protein binding. Cationic liposomes were the most hydrophobic ones followed by non-charged and polymeric. Correlation “Higher the hydrophobic factor (HF) value, augmented surface defects and lower serum protein interaction”. Reference Alonso-Romanowski, S., Chiaramoni, N.S., Lioy, V.S., Gargini, R.A., Viera, L.I., and Taira, M.C. (2003). Characterization of diacetylenic liposomes as carriers for oral vaccines. Chem. Phys. of Lipids. 122:191-203. Farhat Afrin, Ravindran Rajesh, Khairul Anam, Meenakshisundram Gopinath, Seati Pal, and Nahid Ali.(2002). Characterization of Leishmania donovani antigens encapsulated in liposomes that induce protective immunity in BALB/c mice. Infection and Inmunity.  70: 6697-6706. Lelkes, P.I., Miller, I.R. (1980). Perturbations of membrane structure by optical probe: Location an structural sensitivity of Merocyanine 540 bound to phospholipids membranes.. J. Membr. Biol. 52: 1-15.