The delivery of biologically active (therapeutic) peptides and proteins into cells.

Biologically active peptides and proteins have a great potential to act as targeted drug therapies in the treatment of a variety of diseases, including cancer. However, their use in vivo is limited by their low stability and cell permeability. Thus, it is necessary to develop efficient and safe peptide/protein delivery systems that can overcome these problems and increase a therapy's bioavailability. The search for promising vectors has led to the use of compounds called cell-penetrating peptides or protein transduction domains. The cell-penetrating peptides, as effective transporter, are utilized to enhance uptake of various biologically active peptide/protein cargos upon fusion or attachment to its sequences. Cell-penetrating peptides have been the subject of investigation of many researchers, however this review only focuses on the arginine-rich and amphipathic carriers and their potential therapeutic use.