Liposomes stabilized with s-layer proteins from lactobacilli

HOLLMANN, AXEL; DELFEDERICO, L; DE ANTONI, GRACIELA; SEMORILE, LILIANA; DISALVO, ANIBAL

ROSARIO, ARGENTINA

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

One of the commonly observed outer surface components of cell envelopes of prokaryotic organisms, archaea and bacteria, are crystalline arrays of proteinaceous subunits, known as surface layers. S-layers are composed of single protein or glycoprotein species and represent the simplest biological membrane developed during evolution Isolated S-layer subunits of numerous organisms are able to assemble “in vitro”, either in suspension, at liquid surface interfaces, on lipid films including liposomes and on solid supports [1]. Liposome stability towards different stress factors has been significantly enhanced when they were coated with S-layer proteins from Geobacillus stearothermophilus [2, 3]. However, the possibility to prepare lipid particles using S-layers proteins from microorganisms with beneficial effects for human health, as lactobacilli members, has not been reported yet. The stability of liposomes coated with S-layer proteins from Lactobacillus brevis and Lactobacillus kefir was analysed in this study, as a previous stage to the development of a vaccine vehicle for oral administration. The interactions of the different S-layer proteins with positively charged liposomes prepared with soybean lecithin or dipalmitoylphosphatidylcholine were studied by means of the variation of the Z potential at different protein-lipid ratios, showing that both proteins were able to attach in a greater extent to the surface of soybean lecithin liposomes. The capacity of these particles to retain carboxyfluorescein or calcein by exposure to bile salts, pancreatic extract, pH change and after a thermal shock showed that both S-layer proteins increased the stability of the liposomes in the same magnitude. The ability of S-layer proteins to avoid liposome fusion was studied using rhodamine in the membrane. It was observed that fusion of liposomes coated with S-layer proteins was lower than in the control without the protein.   The development of drug targeting and delivery systems based on liposomes coated with functional S-layer isolated from beneficial bacteria such as lactobacilli, appears in the light of the present results as a possibility to enhance their efficiency and stability