Interactions between proteins and carbon-based nanoparticles: Exploring the origin of nanotoxicity at the molecular level

The widespread application of nanomaterials has spurred an interest in the study of interactions between nanoparticles and proteins due to the biosafety concerns of these nanomaterials. In this review, a summary is presented of some of the recent studies on this important subject, especially on the interactions of proteins with carbon nanotubes (CNTs) and metallofullerenols. Two potential molecular mechanisms have been proposed for CNTs' inhibition of protein functions. The driving forces of CNTs' adsorption onto proteins are found to be mainly hydrophobic interactions and the so-called π-π stacking between CNTs' carbon rings and proteins' aromatic residues. However, there is also recent evidence showing that endohedral metallofullerenol Gd@C ₈₂(OH)₂₂ can be used to inhibit tumor growth, thus acting as a potential nanomedicine. These recent findings have provided a better understanding of nanotoxicity at the molecular level and also suggested therapeutic potential by using nanoparticles' cytotoxicity against cancer cells. Two potential molecular mechanisms have been proposed for carbon nanotubes' inhibition of protein functions, one by disruption of the protein active sites, and the other by competitive binding with incoming ligands. The driving force is revealed to be dominated by the π-π stacking interaction.