Development of Lipid-Based Drug Delivery Systems for Gene Therapy: Physicochemical Characterization of Charged Lipid Interactions

Abstract

Small interfering RNA (siRNA) can silence genes via the RNA interference mechanism, and can be used in gene therapies. Unfortunately, due to interactions with proteins, RNase and immune system cells, exogenous RNA is rapidly degraded and/or cleared from the bloodstream. Furthermore, because siRNA is a large, negatively charged molecule, it does not readily diffuse across cell membranes. Nanoparticle drug delivery systems containing siRNA complexed with cationic lipid are currently being developed to overcome these challenges. In general, nanoparticles enter cells via endocytosis. The proposed siRNA delivery mechanism is as follows. The endosomal membrane contains anionic lipids that combine with cationic lipids in the carrier, resulting in dissociation of siRNA and the formation of non-bilayer structures that disrupt the endosomal membrane causing siRNA to be released into the cytoplasm. To investigate the key element of this process, the formation of non-bilayer phases, NMR measurements on a potent cationic carrier lipid XTC2 and an endosomal lipid LBPA were performed, as well as computer simulations on analogous systems. These results are important to understanding delivery mechanisms and rational design of siRNA-containing nanoparticles that have enhanced gene silencing potency.