Introduction
Nano-sized materials are used in nanomedicine to deliver drugs more efficiently to their site of action. In order to improve their efficacy, a better understanding of how cells interact with nano-sized materials is required. Our research is focused on characterizing the molecular details of the early interactions of nano-sized materials at the cell membrane, and the subsequent mechanisms of uptake and intracellular trafficking. To this end, we combine classic transport studies with inhibitors and RNA interference to genetic screening and proteomic-based methods to characterize the mechanisms by which nanoparticles are internalized by cells. Additional efforts are focused on developing advanced in vitro models more closely resembling the in vivo environment for our studies, including endothelial cell barriers and precision cut tissue slices from different organs.
We show that the molecules adsorbing on the nanoparticle surface once applied in serum (forming the nanoparticle corona) can interact with specific cell receptors and can affect the mechanism cells use for their internalization. Thus, using liposomes of different composition, the corona can be tuned to modulate uptake efficiency and uptake kinetics. By correlating corona composition and cell uptake efficiency, corona proteins promoting or reducing uptake can be discovered. Alternatively, we used reversible biotinylation of cell membrane proteins in live cells to directly identify nanoparticle receptors. We found that even when interacting with specific receptors, nanoparticles can be internalized by cells via different mechanisms than what it is usually observed for their endogenous ligands. For instance, nanoparticles interacting with the LDL receptor (LDLR) via their corona are internalized by cells via a mechanism that is not clathrin-mediated.9 Instead, we found that nanoparticle uptake is mediated by specialized curvature-sensing proteins, which may trigger alternative uptake mechanisms. Using nanoparticle of different properties, we show how their involvement varies depending on nanoparticle curvature and nanoparticle rigidity.
Our findings highlight the importance of understanding how cells interact with and process nano-sized materials in order to improve nanomedicine design.