Polystyrene nanoparticles to mimic a complex matrix: functional and structural features of a hypoglycaemic lupin protein

In vitro simulation of in vivo conditions is usually achieved by reproducing the typical molecular crowding occurring in a food system or in a cell. Proteins and peptides often exert their function when inserted in high-order macromolecular structure such as protein complexes or membranes, or, in food systems, when associated to disperse phases. Stable adhesion of proteins to hydrophobic or hydrophilic structures, such as nanoparticles or nanoemulsions, could be considered a model to mimic these complex systems. In this study we explore the effects of adhesion to polystyrene nanoparticles (NPs) on the functional bioactivity of gamma-conglutin (Cg), a lupin seed protein able to reduce glycemia, and to elicit allergenic reponses. The molecular features at the basis of such activities are still not completely elucidated. The nature of the reversible interaction between Cg and NPs was characterized in terms of: i) amount of protein bound, ii) stability of the interaction, iii) protein structural modification. The biological effects of the protein absorbed to NPs has been studied by using transfected Caco-2 cells transformed to express markers evidencing triggering of immune response.