RNA interference in mammalian cells by siRNAs modified with morpholino nucleoside analogues

siRNAs modified with morpholino nucleoside analogues were synthesized and their biological properties were examined in details. The gene silence abilities of modified siRNAs were correlated to the positions of the modi. cations, some of which appeared to be more potent than the native siRNA. The 30-end modification improved the stability of siRNAs in serum significantly. Furthermore, the dose-response and time-course experiments demonstrated that the siRNAs with 30-end modification have potent gene silence activity at lower concentration and prolonged action time. These favorable properties make the morpholino modified siRNA a potentially useful tool in therapeutic applications. (C) 2009 Elsevier Ltd. All rights reserved.