Development of cell-penetrating peptides as vectors for drug delivery

Biomacromolecules play an important role in the treatment of many diseases, but as a result of cell membrane serving as the natural barriers, only the small molecular compounds whose molecular weights are smaller than 600 Da can get through cell membrane and enter the cell.  In recent years, some short peptides (the length less than 30 amino acids) are found to have the cell-penetrating function, called cell-penetrating peptides (CPPs).  They are able to effectively translocate segments of protein, polypeptides, nucleic acid into the cells of many mammal animals with many methods.  They have high transduction efficiency and will not lead to cell damage.  So, the discovery of CPPs has a very good applicable prospect in such research fields as cell-biology, gene-therapy, drug transduction in vivo, evaluation of clinical medicine and medical immunology.  This    paper reviews the types and characteristics of CPPs, internalization mechanisms, applications, and their existing problems.