Cell-penetrating peptides (CPPs) have been previously shown to be
powerful transport vector tools for the delivery of a large variety of cargoes
through the cell membrane, as well as other physiological membranes. And since
they’re relatively cell-, receptor- and energy-independent, CPPs have unique
advantages in facilitating drugs entry into cells. This paper briefly reviews the
discovery, mechanism and classification of CPPs, and especially focuses on the
specific limitations of CPPs and their potential applications for tumor-targeted delivery of biologically active molecules,
imaging agents and carriers.