Rationally designed siRNA delivery materials that are enabled by lipid-modified aminoglycosides are demonstrated. Leading materials identified are able to self-assemble with siRNA into well-defined nanoparticles and induce efficient gene knockdown both in vitro and in vivo. Histology studies and liver function tests reveal that no apparent toxicity is caused by these nanoparticles at doses over two orders of magnitude.Damon Runyon Cancer Research Foundation (DFS-#2050-10)Alnylam Pharmaceuticals (Firm)National Institutes of Health (U.S.) (grant EB000244)National Institutes of Health (U.S.) (grant 1-RO1-CA132091-03