RNA interference refers to sequence-specific messenger RNA degradation initiated by introduction of short RNA duplexes. Since this event results in target-specific gene silencing, siRNAs are expected to serve as potential therapeutic agents to silence disease-causing genes. However, a substantial barrier to the therapeutic application is the delivery of siRNA duplexes into cells. Cyanocobalamin is one of the essential vitamins needed for the division of all cells. Cancer cells especially require abnormally high amounts of cobalamins due to rapid cell division. As a result, the cobalamin...