Molecular engineering of dendrimer nanovectors for siRNA delivery and gene silencing

Small interfering RNA (siRNA) therapeutics hold great promise to treat a variety of diseases, as long as they can be delivered safely and effectively into cells. Dendrimers are appealing vectors for siRNA delivery by virtue of their well-defined molecular architecture and multivalent cooperativity. However, the clinical translation of RNA therapeutics mediated by dendrimer delivery is hampered by the lack of dendrimers that are of high quality to meet good manufacturing practice standard. In this context, we have developed small amphiphilic dendrimers that self-assemble into supramolecular structures, which mimic high-generation dendrimers synthesized with covalent construction, yet are easy to produce in large amount and superior quality. Indeed, the concept of supramolecular dendrimers has proved to be very promising, and has opened up a new avenue for dendrimer-mediated siRNA delivery. A series of self-assembling supramolecular dendrimers have consequently been established, some of them out-performing the currently available nonviral vectors in delivering siRNA to various cell types in vitro and in vivo, including human primary cells and stem cells. This short review presents a brief introduction to RNAi therapeutics, the obstacles to their delivery and the advantages of dendrimer delivery vectors as well as our bio-inspired structurally flexible dendrimers for siRNA delivery. We then highlight our efforts in creating selfassembling amphiphilic dendrimers to construct supramolecular dendrimer nanosystems for effective siRNA delivery as well as the related structural alterations to enhance delivery efficiency. The advent of self-assembling supramolecular dendrimer nanovectors holds great promise and heralds a new era of dendrimer-mediated delivery of RNA therapeutics in biomedical applications.