Comparison of four different peptides to enhance accumulation of liposomes into the brain

The cell penetrating peptide TAT, which appears to enter cells with alacrity, can pass through the BBB efficiently. It has been indentified to enhance the brain delivery of the liposome. However, little was known about its mechanism. TAT contains a basic region consisting of six arginine and two lysine residues. These eight basic amino acids seem to be the key to its highly efficient membrane translocation and brain delivery. In this study, four selected peptides are synthesized. (1) TAT peptide with terminal Cysteine (Cys-AYGRKKRRQRRR). (2) TAT peptide with disordered sequence (Cys-RKARYRGRKRQR). (3) Glycine and glutamic acid substituted TAT peptide (Cys-AYGGQQGGQGGG). (4) R8 (Cys-RRRRRRRR). Liposomes were chosen as the delivery vehicle. The peptide was covalently bonded with the liposome. We compare four peptides for their brain targeting potential, and investigate their ability to target liposomes to the brain in vitro and in vivo. The cellular uptake of these four liposomes by brain capillary endothel...