The role of disulfide-bridge on the activities of H-shape gemini-like cationic lipid based siRNA delivery

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In our previous study, a H-shape gemini-like cationic lipid (ssGLCL, formerly named as CLD), composed of two hydrophilic lysine heads and two hydrophobic oleyl alcohol tails with a bridge of the redox-active disulfide-bond, had been synthesized and used as a nanocarrier for delivering small interfering RNAs (siRNAs) into cells. In order to further elucidate the role of disulfide (−S−S−) bridge on the activity of ssGLCL based siRNA delivery, a comparable ccGLCL bridged with a non-reducible carbon–carbon bond was synthesized and used as control in this study. Both two H-shape GLCL molecules could individually self-assemble into cationic nanoparticles in water phase and complex with negatively-charged siRNA into nanoplexes with particle size of ˜ 200 nm and zeta potential of ˜ + 30 mV, and exhibit effective siRNA delivery both in vitro and in vivo. Investigation of internalization pathway displayed that both ssGLCL/siRNA and ccGLCL/siRNA nanoplexes were predominantly internalized into MCF-7 cells by the clathrin-mediated endocytosis pattern. Although a lower cellular uptake of siRNA was found in the human breast cancer MCF-7 cells, the ssGLCL/siRNA nanoplexes could exhibit similar or even stronger down-regulation effects on the targeted EGFR mRNA and protein in MCF-7 cells when compared to the ccGLCL/siRNA nanoplexes. Furthermore, mechanistic study showed that the enhanced down-regulation effects of ssGLCL/siRNA nanoplexes on targeted mRNA and protein were probably attributed to the increased release of siRNA from lysosomes to cytoplasm following the cleavage of redox-active disulfide-bridge in ssGLCL. Therefore, we believed that the redox-active H-shape ssGLCL could be a potential nanocarrier towards improving siRNA delivery.

Graphical abstract

The GLCL/siRNA nanoplexes were prepared with electrostatic interaction. After cell internalization, the ssGLCLs were split into two single chain lipid units with the cleavage of disulfide-bridge by abundant reductive glutathione (GSH) in cells, then the resulted monomeric lipid unit exhibited higher membrane fusion and facilitated release of siRNA from lysosomes into cytoplasm, thus the enhanced gene silencing effects on targeted mRNA were obtained.

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