The influence of ligand organization on the rate of uptake of gold nanoparticles by colorectal cancer cells

We have explored the uptake of different hydrophilic mono- and dual-ligand gold nanoparticles in colorectal cancer cells in vitro and find that the rate of uptake is dependent on the structural organization of the ligands on the surface of the particles rather than their charge or chemical properties. Gold nanoparticles with 50%PEG-NH2/50% glucose are taken up eighteen fold faster than nanoparticles carrying only PEG-NH2 or glucose. Glutathione-coated gold particles are by far the most efficiently internalized; however, glucose-glutathione dual-ligand nanoparticles are taken up at a thirty fold reduced rate. We found furthermore that the rates are influenced by the cell density and concentration of glucose in the growth medium. Rather than being internalized through a conventional receptor-mediated mechanism the particles appear to be taken up by the cells via an energy-independent diffusion across the cell membrane through pre-existing pores or openings in the lipid bi-layer created by ligands on the gold nanoparticles.