Disulfide crosslinked stearoyl carrier peptides containing arginine and histidine enhance siRNA uptake and gene silencing

The siRNA has been expected to apply for several diseases such as cancer since siRNA specifically silences the disease-associated genes. However, effective gene carriers should be developed to overcome the low siRNA stability in vivo, form stable complexes and facilitate intracellular uptake of siRNA. In this study, to develop a safe and efficient siRNA carrier, stearoyl (STR) peptides with Cys (C), Arg (R), and His (H) residues that can form disulfide cross linkages via Cys (C) were synthesized, and their suitability as siRNA carriers was evaluated. The particle size of STR-CH2R4H2C/siRNA complexes was about 100 nm. The cellular uptake ability after transfection with FAM-siRNA with STR-CH2R4H2C, CH2R4H2C, or STR-GH2R4H2G was significantly higher than that with FAM-siRNA only. STR-CH2R4H2C showed the highest cellular uptake ability when compared with CH2R4H2C and STR-GH2R4H2G. STR-CH2R4H2C did not induce substantial cytotoxicity. The intratumor injection of STR-CH2R4H2C/vascular endothelial growth factor (VEGF) siRNA (siVEGF) complexes achieved a high anti-tumor effect in tumor bearing mice. These results suggest STR-CH2R4H2C has potential of effective siRNA carrier possible to exercise silencing effect in vitro and in vivo.