Synthesis and development of new polymers for optimized delivery of nucleic acids

Nucleic acids exhibit great potential in numerous applications including in medicine and agriculture. Gene therapies, employing DNA encoding therapeutic proteins, are in development for diseases ranging from cystic fibrosis to cardiovascular disease to cancer. Similarly, interfering and antisense RNAs can be used to shut down expression of target genes associated with disease as well as being investigated as agents for pest and disease vector control. In all of these applications, however, a limiting barrier to their commercialization is the lack of safe, efficient, and inexpensive methods for delivery of nucleic acids into cells. The overall goal of this project is to investigate the effects of polymer-mediated nucleic acid (NA) condensation on gene delivery activity and mechanisms.

Nucleic acids typically require a carrier material that binds and protects the NA, allows endocytosis by target cells, mediates escape from endocytic vesicles into the cytosol, and ultimately releases the nucleic acids in the cytoplasm (interfering dsRNA/siRNA) or the nucleus (DNA) (Figure 3). A variety of cationic lipids and polymers have been investigated as NA delivery vectors including off-the-shelf synthetic polymers, biomaterials, and numerous materials designed specifically for NA delivery. Polycation-NA and dendrimer-NA complexes (polyplexes/dendriplexes, respectively) represent a particularly attractive approach due to their low immunogenicity and ease of chemical modification. To date, however, all NA delivery polymers are hindered by insufficient delivery activity, cytotoxicity, or cost. As an example, polyethylenimine (PEI) exhibits high transfection efficiency in cell culture and is often considered the “gold-standard” for in vitro gene delivery. Its application in vivo is hindered, however, by cytotoxicity. Design of more efficient materials requires understanding of polymer-DNA interactions, the formation of polymer/NA complexes, and how their structures relate to intracellular trafficking mechanisms and gene delivery efficiency.

Figure reprinted from Pack et al. (2015) Nat. Rev. Drug Discov. showing the barriers to successful NA delivery