1037. Formulating and Testing of Targeted siRNA for Applications In Vivo

Abstract

The use of RNAi to manipulate gene expression has become an invaluable tool in the elucidation of gene function. Although RNAi may have therapeutic potential, its successful application is limited by instability and poor delivery of synthetic small interfering RNAs (siRNAs) or vector-expressed short-hairpin RNAs (shRNAs) in mammalian systems. A comparative evaluation of the efficiency of siRNA versus plasmid-expressed indicated that siRNAs are more potent inhibitors of gene expression than shRNA however, the duration of silencing by siRNAs is shorter than for shRNAs. An evaluation of PEI versus Cys-Trp-Lys17-Cys to delivery siRNAs in vitro showed no difference in the efficiency of knockdown, suggesting that the transfection agent used does not affect siRNA potency. In an effort to improve in vivo stability and liver targetingefficiency, siRNA was formulated with glutaraldehyde-crosslinked glycopeptide PEG-peptide to form stabilized colloids. These formulations showed improved liver targeting efficiency and metabolic stability in mice. The results provide evidence of improved formulation strategies for siRNA utilizing cross-linked peptide gene delivery systems that may improve potency and duration of action in vivo.