Effects of the presence or absence of a protein corona on silica nanoparticle uptake and impact on cells.

Nanoparticles enter cells through active processes, thanks to their capability of interacting with the cellular machinery. The protein layer (corona) that forms on their surface once nanoparticles are in contact with biological fluids, such as the cell serum, mediates the interactions with cells in situ. As a consequence of this, here we show that the same nanomaterial can lead to very different biological outcomes, when exposed to cells in the presence or absence of a preformed corona. In particular, silica nanoparticles exposed to cells in the absence of serum have a stronger adhesion to the cell membrane and higher internalization efficiency, in comparison to what is observed in medium containing serum, when a preformed corona is present on their surface. The different exposure conditions not only affect the uptake levels but also result in differences in the intracellular nanoparticle location and impact on cells. Interestingly, we also show that after only one hour of exposure, a corona of very different nature forms on the nanoparticles exposed to cells in the absence of serum. Evidence suggests that these different outcomes can all be connected to the different adhesion and surface properties in the two conditions.