In Vitro Potency of Chemically Modified siRNAs Against TNF-alpha The execution of succesful RNAi experiments depends upon multiple factors: 1. Design and identification of effective and specific siRNA sites 2. Enhancement of pharmacocinetic properties 3. Delivery of siRNA. Therefore we have designed, prepared and functionality tested a variety of chemical modifications. These have been tested in HeLa cells to ascertain wether they influence RNAi inducing activity. We have chosen tumor necrosis factor (TNF-alpha) as a target.