Interaction of liposomes/nitrogen compounds and influence on lipid/solution distribution

A. LIS FEMIA; M. C. TAIRA; M. GRASSELLI; S. DEL V. ALONSO

Rosario

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

Sociedad Argentina de Biofísica

Lipidic vesicles are very well known as drug carriers. Here, we describe the interaction of three nitrogen compounds: nitric oxide (KNO2), sodium nitroprusside (SNP) and arsanilic acid. The last two have pharmaceutical properties and the first is use as comparative purposes (1). Lipidic systems have no effect on immune system and are assimilable to celular membranes. We analyzed the interaction and/or encapsulation efficiency as a function of the hydrofobic structure: NO2 SNP Arsanilic acid. In general the studies involved: -1) Liposomes: of egg yolk (EPC) or soy (SPC) phosphocholine, and cholesterol were prepared as in reference (2). -2) Encapsutaled sodium nitroprusside and nitric oxide concentrations were between 0.20 mM and 40.00 mM, maintaining constant lipid concentration at 1 mM. -3) Encapsulated arsanilic acid solutions were prepared between 0.16 mM and 40.00mM maintaining constant lipid concentration at 1mM. - 4) Merocyanine (MC540) was used at a concentration of 4,3 x 10-7 mM and the relation dye/lipid was: 120. Hydrophobicity was measured using MC 540, the dye partitionates between aqueous phase and hydrophobic lipid side chains (3). We measured the absorption spectra of merocyanine in each solution. KNO2 showed no modification of MC540 spectra at any concentration. Instead of nitroprusside and arsanilic acid, modified the maxima and absorbance of merocyanine spectra in water. We found that concentration of those two compounds have a constant relationship at which the efficiency is maxima and that the efficiency depends on the pH used. These results were corroborated by an independent binding method: isothermal calorimetry (ITC).