The Cell-Type Specificity and Endosomal Escape of Cell-Penetrating Peptides

Cell-penetrating peptides (CPPs) have become a great potential non-invasive carrier candidate for the delivery of various cell-impermeable therapeutic cargoes such as proteins, polypeptides and nucleic acid. However, the lack of tissue specificity and entrapment in the endocytic vesicles is the primary limitation to the application of these peptides in cargo delivery. Emphasis should be placed on developing novel methods to overcome these barriers. In this review, several current strategies to promote tissue specificity and endosomal escape of CPPs will be described, as well as the comparison of different approaches in efficacy and security. Finally, this review will be attributed to new ideas to improve the tissue specificity and cytosolic availability of CPP-cargoes.