Fig. 1.

Schematic displaying endocytosis of anionic (left) and cationic (right) nanoparticles and their resulting cytosolic formations. Cationic nanoparticles show stronger absorption capabilities than their anionic cousins, and, once endocytosed, they act as sponges that pump protons and signal cytotoxic cascades. The lower left transmission electron microscopy (TEM) images show aggregated anionic particles (bottom left) in HeLa cells compared to dispersed cationic particles with heightened uptake (bottom right). Reproduced from ref. 13 with permission from The Royal Society of Chemistry