Cell-penetrating peptides: from cell cultures to in vivo applications

The field of gene therapy is starting to move towards clinical applications but is currently limited by the lack of efficient delivery systems. Cell-penetrating peptides provide a means of cellular delivery for gene therapy applications as well as delivery of traditional drugs. Using cell-penetrating peptides a range of different cargoes have been successfully delivered into a number of cell types, in vitro as well as in vivo. In this review we discuss uptake mechanisms of different cell-penetrating peptides, with or without cargo. The transition from in vitro to in vivo applications and strategies to increase the bioavailability of cell-penetrating peptides are also discussed.