Autoorganización en sistemas biomoleculares: efecto de la concentración iónica en la distribución de tamaños de liposomas preparados con aceite de soya.

Abstract

Unilamellar liposomes were prepared with the lipid component of soy-bean oil (food grade soybean lecithin), in saline buffer solutions (PBS) of pH 7 and ionic concentrations of sodium chloride NaCl of: 0 mM , 50 mM , 100 mM , 150 mM y 200 mM . For this, the method of hydration of a lipid film and its subsequent sonification was used. The concentration of liposomes was evaluated with the absorbance at 232 nm. Then, their size distribution (hydrodynamic diameters) and zeta potential (ζ) were characterized with the method of nanoparticle tracking analysis (Nanotracking); this method analyzes a number of paths traced by light that scatter electrons through successive video images. Was observed that these distributions are independent of the ion concentration, thus demonstratin stability in the range studied; in agreement with results from the literature. Likewise, it was found that the diameters of the liposomes have mean values around 120 nm and ζ potentials around −40 mV associated with positive charges of the liposomal surface. These results were analyzed within the framework of the DLVO theory and the model of the electrical double layer. With this, it was possible to explain that the polarity of the zeta potentials obtained is due to the fact that the anions in the medium are adsorbed by the liposomes due to the presence of the choline group (C5H14NO^+) on the surface of the phosphatidylcholines; the latter are the constituent molecules with the highest composition in soybean lecithin and that make up the liposomes of interest.