Controlling gene expression through RNAi typically involves the use of double-stranded RNA molecules that are between 20–25 base pairs long. Dubbed “small interfering” or “silencing” RNA (siRNA), these oligonucleotides interfere with native gene expression by binding to complementary strands of messenger RNA (mRNA) to form complexes that are then degraded by the cell’s natural machinery before protein translation can occur. While the exact mechanism of siRNA-mediated gene suppression is complex, siRNAs can potentially be used to selectively disrupt the expression of any gene within a given genome. Recently, RNAi-based approaches have been gaining traction as promising modalities to inhibit viral infection and cancer proliferation in humans. However, while targeted gene suppression by siRNA has shown promising clinical results for certain applications, consistent delivery of siRNA to specific targets in vivo has remained a difficult challenge.