Chapter 5 - RIPL peptide as a novel cell-penetrating and homing peptide: design, characterization, and application to liposomal nanocarriers for hepsin-specific intracellular drug delivery

Abstract

For targeted intracellular drug delivery, the RIPL peptide (IPLVVPLRRRRRRRRC; 16mer; 2.1 kDa) was introduced as a novel cell-penetrating and homing peptide for hepsin (Hpn)-expressing cancer cells. RIPL peptides were conjugated to maleimide-derivatized liposomal vesicles to develop RIPL peptide-conjugated liposomes (RIPL-Lipo). The specificity of intracellular uptake of RIPL peptide and RIPL-Lipo was assessed by measuring the mean fluorescence intensity after treatment with a fluorescent marker (FITC-dextran) in the following cell lines: LNCaP, MCF-7, and SK-OV-3 as Hpn(+) and HaCaT, DU145, and PC3 as Hpn(−). Cellular uptake behavior was visualized by confocal laser scanning microscopy, revealing time-dependent cytosolic internalization of RIPL-Lipo systems. The cytotoxicities of RIPL peptide and RIPL-Lipo were low (cell viability > 90%) at the concentration examined. In this chapter, along with a brief introduction of cell-penetrating and homing peptides, important aspects in the design of specific peptides and targetable liposomal nanocarriers will be discussed, focusing on Hpn-specific intracellular drug delivery.