Environment-Responsive Lipid/siRNA Nanoparticles for Cancer Therapy.

RNA interference (RNAi) is a promising technology to regulate oncogenes for treating cancer. The primary limitation of siRNA for clinical application is the safe and efficacious delivery of therapeutic siRNA into target cells. Lipid-based delivery systems are developed to protect siRNA during the delivery process and to facilitate intracellular uptake. There is a significant progress in lipid nanoparticle systems that utilize cationic and protonatable amino lipid systems to deliver siRNA to tumors. Among these lipids, environment-responsive lipids are a class of novel lipid delivery systems that are capable of responding to the environment changes during the delivery process and demonstrate great promise for clinical translation for siRNA therapeutics. Protonatable or ionizable amino lipids and switchable lipids as well as pH-sensitive multifunctional amino lipids are the presentative environment-responsive lipids for siRNA delivery. These lipids are able to respond to environmental changes during the delivery process to facilitate efficient cytosolic siRNA delivery. Environment-responsive lipid/siRNA nanoparticles (ERLNP) are developed with the lipids and are tested for efficient delivery of therapeutic siRNA into the cytoplasm of cancer cells to silence target genes for cancer treatment in preclinical development. This review summarizes the recent developments in environment-response lipids and nanoparticles for siRNA delivery in cancer therapy.