Cell-Penetrating Peptides

In this introductory chapter, we first define cell-penetrating peptides (CPPs), give short overview of CPP history and discuss several aspects of CPP classification. Next section is devoted to the mechanism of CPP penetration into the cells, where direct and endocytic internalization of CPP is explained. Kinetics of internalization is discussed more extensively, since this topic is not discussed in other chapters of this book. At the end of this section some features of the thermodynamics of CPP interaction with the membrane is also presented. Finally, we present different cargoes that can be transferred into the cells by CPPs and briefly discuss the effect of cargo on the rate and efficiency of penetration into the cells.