Study of protein-polysaccharide interactions in aqueous solutionfor designing biopolymer self-assembled particles

FIORAMONTI, S. A.; PEREZ, A. A.; ARINGOLI, E. E.; RUBIOLO, A. C.; SANTIAGO, L. G.

Buenos Aires

Jornada; VI Jornadas Internacionales de Proteínas y Coloides Alimentarios - JIPCA VI; 2011

Universidad de Buenos Aires y Universidad de La Plata

The study and manipulation of electrostatic interactions between oppositely charged biopolymers, has gained great interest in science as a strategy for designing nano-and micro-self-assembled structures with specific properties. These self-assembled biopolymer particles could be used to develop delivery systems and to encapsulate and / or protect bioactive substances (vitamins, carotenoids, peptides, fatty acids w-3) susceptible to degradation. However, their development would involve the understanding of physicochemical phenomena underlying the formation of these structures, through the study of both macromolecular interactions and variables that modulate these interactions. This work provides some insights on the design and characterization of soluble biopolymer particles produced by self-assembly of an anionic polysaccharide (sodium alginate, SA) and a whey protein isolate (WPI). First, we chose an experimental design to study the effect of concentration (2, 4 and 6%) and temperature (55, 70 and 85 °C) on structural characteristics of the WPI, by applying spectroscopic techniques UV-Vis and fluorescence, both intrinsic and extrinsic. Secondly, from aqueous solutions of 6% w/w heat-treated WPI at different temperatures, WPI/SA systems were obtained by mixing biopolymers at different WPI: SA ratios (2:1, 4:1 and 6:1) and transmittance measurements (850 nm) as a function of pH (6.0-3.0) were made. The dynamic behavior of biopolymers in WPI/SA systems could be discussed in terms of the transition pHs, pHc and pHf, corresponding to the formation of WPI-SA soluble complexes and the beginning of the associative phase separation, respectively. Finally, with these pH values, phase diagrams were built for each system and conditions for designing biopolymer particles were selected (85 °C and pH 4) considering that:  (i) heat-treated WPI at the highest temperature (85 °C) induced the formation of soluble protein aggregates with a higher exposure of hydrophobic patches on their surface, and (ii) the formation of WPI-SA soluble complexes was observed at pH 4 for all WPI/SA systems The resultant self-assembled particles were characterized by the same set of spectroscopic techniques. It was found that  higher WPI:SA ratios produce soluble biopolymer self-assembled particles where hydrophobic patches of protein  would be more occluded ensuring the protection and possible transport of lipophilic bioactive agents attached inside