CHARACTERIZATION OF THE ADSORPTION PROCESS OF LINOLEIC ACID ON OVALBUMIN NANOPARTICLES

OSVALDO E. SPONTON; ADRIÁN A. PEREZ; FLAVIA F. VISENTINI; CARLOS R. CARRARA; LILIANA G. SANTIAGO

Santa Fe

Simposio; XI Simposio Argentino de Polímeros - SAP 2015; 2015

Some protein nanostructures have been proposed for the development of delivery systems for vehiculization of bioactive compounds. In this sense, it has been demonstrated that heat-induced nanoparticles of ovalbumin (OVAn) are able to bind lipophilic bioactive compounds, such as linoleic acid (LA, a model polyunsaturated fatty acid). The study of the interaction between LA and OVAn could be important to define conditions for the development of delivery systems. Hence, the aim of this work was to study the stoichiometric, kinetic and thermodynamic aspects of LA-OVAn complexes formation. For this reason, turbidity measurements were carried out taking into account that LA in aqueous solution is arranged in supramolecular self assemblies (vesicles) which confer turbidity to solution. Hence, turbidity measurements (absorption at 400 nm) of LA solution, with OVAn addition, were carried out as a function of time, at different temperatures (20-40°C) and LA/OVAn ratios (21.5-172). An adsorption model (pseudo-second-order kinetic) was proposed to analyze the results. A very fast decay of turbidity was registered when OVAn was added to LA solution, suggesting a rapid adsorption process. This process took place in a time scale lower than 1 hour. On the other hand, a LA-OVAn stoichiometry of 48.1 ± 1.6 LA mol/OVAn mol (OVAn was taken on the basis of monomeric form) at 20ºC was obtained. Thermodynamic parameters (ΔG0, ΔH0, ΔS0) were also determined. For all temperatures, ΔG0 values were negative and lower than -10 kJ/mol; suggesting the spontaneous nature of the adsorption process by means of a physical mechanism. Moreover, both ΔH0 and ΔS0 were positive, which would indicate that LA molecules adsorb to OVAn through hydrophobic interactions. In equation ΔG0 = -T ΔS0 + ΔH0 it was found that the -T ΔS0 term was higher than ΔH0 indicating an entropically-driven adsorption process.