Peptide Targeting Methods

This chapter summarizes the latest advances in the identification and application of peptides in biomedical and clinical sciences, focusing on the recent progress in the development of peptide-mediated methods for drug delivery and molecular imaging technologies in cancer. Targeting peptides are most often identified from three major sources: (i) natural ligands or their analogs from plants and animals, (ii) chemically synthesized products, and (iii) phage display peptide libraries. Peptide–drug conjugates can target specific cells to improve the efficiency of delivery for existing drugs, reducing side effects and improving therapeutic efficacy. Unlike integrin-targeting peptides, cell-penetrating peptides (CPPs) facilitate the delivery of payloads by enhancing cell penetration properties. CPPs are capable of passing through the cell membrane into the cytoplasm either by direct translocation or by endocytosis. The major obstacles in the use of CPPs are nonspecific cellular uptake and ease of proteolysis.