Tandem Peptide Based on Structural Modification of Poly-Arginine for Enhancing Tumor Targeting Efficiency and Therapeutic Effect.

The nonselectivity of cell penetrating peptides had greatly limited the application in systemic administration. By conjugating a dGR motif to the C-terminal of octa-arginine, the formed tandem peptide R8-dGR had been proved to specifically recognize both integrin αvβ3 and neuropilin-1 receptors. However, the positive charge of poly-arginine would still inevitably lead to rapid clearance in the circulation system. Therefore, in this study, we tried to reduce the positive charge of poly-arginine by decreasing the number of arginine, to thus achieve improved tumor targeting efficiency. We had designed several different Rx-dGR peptides (x = 4, 6, and 8) modified liposomes and investigated their tumor targeting and penetrating properties both in vitro and in vivo. Among all the liposomes, R6-dGR modified liposomes exhibited a long circulation time similar to that of PEGylated liposomes while they retained strong penetrating ability into both tumor cells and tumor tissues, and thus had displayed the most superior tumor targeting efficiency. Then, paclitaxel and indocyanine green coloaded liposomes were prepared, and R6-dGR modified coloaded liposomes also exhibited enhanced antitumor effect on C6 xenograft tumor bearing mice. Therefore, we suggest R6-dGR as a potential tumor targeting ligand with both strong penetrating ability and improved pharmacokinetic behavior, which could be further used for efficient antitumor therapy.