Effect of the Ligand Binding Strength on the Morphology of Functionalized Gold Nanoparticles

Functionalized gold nanoparticles are investigated by density functional theory calculations in the context of cancer radiotherapy. Several typical experimental shapes, including nanostars, nanospheres, and nanorods, are modeled by optimizing Au clusters covered by organic monolayers composed of hydrated short-chain polyethylene glycol (PEG) ligands. The PEGylation stabilizes significantly the stellation of decahedral Au₅₄ by deforming significantly its geometry at the spikes. The higher stability of the PEG molecules adsorbed on this stellated nanocluster with respect to the more spherical icosahedral Au₅₅ and truncated octahedral Au₇₉ leads to a larger energy cost to desorb them and thus a weaker propensity for the starred nanoparticle to exchange ligands with the cell membrane, in agreement with experiments. These results open interesting possibilities for advancing our understanding of the cellular uptake of gold nanoparticles.