Interaction of graphene oxide with albumins: Effect of size, pH, and temperature

Understanding the interaction between graphene oxide (GO) and the biomolecules is fundamentally essential, especially for disease- and drug-related peptides and proteins. In this study, the interaction between GO and albumins (bovine serum albumin, human serum albumin, and bovine alpha-lactalbumin) has been performed by fluorescence and UV-Vis spectroscopic techniques. The fluorescence quenching mechanism between GO and aromatic acids residues with intrinsic fluorescence was determined as mainly static quenching in combination with dynamic quenching. The optimal conditions for the most effective affinity between albumins and GO have been estimated at neutral pH and room temperature. The strong impact of the size of graphene oxide on the interaction between proteins and graphene oxide has been confirmed, as well. The interaction between GO and albumins has been examined as electrostatic and hydrophobic. The electrostatic interaction was confirmed by pH effect, while the hydrophobic interaction was proved by the presence of Poloxamer188. The CD spectra of albumins exhibit decreasing helicity in the secondary structure of albumins upon the addition of GO. However, no significant changes in position and shape of characteristic negative bands have been noted. Mentioned changes indicate the successful interaction between GO and proteins, the predominantly alpha-helical structure of albumins has been preserved. (C) 2016 Elsevier Inc. All rights reserved.