UNRAVELLING THE STRUCTURAL MODIFICATION OF BETA-LACTOGLOBULIN AFTER ADSORBTION ON POLYSTYRENE NANOPARTICLES

The overall structural changes ensuing from the non-covalent adsorption of bovine beta-lactoglobulin (BLG) on the surface of polystyrene nanoparticles were investigated by using different techniques including spectroscopic approaches, by assessing the reactivity of specific residues, and by limited proteolysis/mass spectrometry. Also, the immunoreactivity of adsorbed and free BLG was compared. Changes made evident by experimental measurements were also computationally highlighted. All these approaches indicated substantial rearrangements of the protein structure in the adsorbed state, in spite of the reported structural rigidity of BLG. The marked changes in many of the protein properties found in this work are somewhat surprising, as no denaturing “forces” where applied on the polystyrene/protein system used here at physiological pH values, and when considering that BLG is reportedly resistant to denaturation over a broad range of experimental conditions. Some of the effects demonstrated in this study [including alteration of proteolytic patterns, altered immunoreactivity, and distortion of structural regions relevant to the physiological function(s) of the protein (e.g., ligand binding or recognition events)] can be of diagnostic relevance and of physiological relevance also for other proteins, also in view of the proposed use of hydrophobic nanostructured materials for diagnostic purposes and for controlled delivery of therapeutic agents.