Endosomal Escape

Cell-penetrating peptides (CPPs) can enter cells through two main routes, direct plasma membrane translocation and endosomal escape. Endosomal escape is the process by which a CPP is endocytosed and subsequently escapes the endosome to reach the cytosolic space of a cell. This chapter will highlight the mechanisms used by CPPs to escape endosomes, the different CPP properties that enhance endosomal membrane permeation, the effects that endosomal escape can have on cells, and the methods that can be used experimentally to monitor and quantify the release of CPPs and payloads from endosomes.