Unmodified single nanoparticles undergo a motion-pattern transition on the plasma membrane before cellular uptake

Abstract

Exposure of biological cells to unmodified nanoparticles (uNPs) of unknown origin is becoming a critical issue for nanotoxicity research. An important problem is to study the non-specific interaction between uNPs and the plasma membrane, the early stage of endocytosis. Here, we monitored the motion of single unmodified gold nanorods (uAuNRs) on live cell membrane with plasmonic imaging in real time. We observed that after landing onto the cell surface, the uAuNR experienced an initial-adsorption stage, where it was doing “touch-and-bounce” motion in a local region, followed by a membrane-diffusion stage, where the uAuNR was doing large-range “hop-diffusion” motion. With the motion-pattern transition of uAuNRs, the driving force of the interaction between uAuNRs and cell membrane changes from electrostatic interaction to ligand-receptor interaction. The protein corona of uAuNRs changes by recruiting protein ligands from the membrane environment, which causes the transition and makes uNPs cytofriendly. The physical picture discovered here provides new insights into non-specific cellular uptake and cytotoxicity of NPs.