(70b) Novel Graft Copolymers Enhance Cationic Lipid Mediated Delivery of Oligonucleotides

Antisense oligodeoxynucleotides (ODNs) represent a useful tool in experimental biology and hold therapeutic promise for the treatment of major disease classes such as cancer, autoimmune, and cardiovascular. The successful delivery of ODNs to the intracellular site of action requires the passage of many barriers, such as interaction with extracellular serum proteins, efficient uptake by endocytosis, and escape from endosomes before lysosomal degradation [Sundaram and Roth].

The system that we have used to deliver ODNs utilizes a cationic liposome, dioleoyl-3-trimethylammonium-propane (DOTAP), with the incorporation of a pH-sensitive polymer, poly (propylacrylic acid), PPAA. Previously, we found efficient antisense delivery mediated by the ternary DOTAP/PPAA/ODN system under serum-free media conditions [Lee and Roth]. However, the effectiveness of this system is greatly reduced by the presence of serum for some cell types. We decided to improve the performance of our current system by modifying the backbone of PPAA by grafting hydrophilic polymer poly (ethylene oxide), PEO, or an analogue, (poly (oxyalkylene amines)), Jeffamine.

We found that, in the presence of serum-containing media conditions, the addition of graft copolymer PPAA-g-Jeffamine to the DOTAP/ODN system enhances ODN delivery and gene silencing effect, while the addition of PPAA-g-PEO hinders ODN delivery. Interestingly, we also observe cell type related differences in the ability of parent polymer PPAA and graft copolymer PPAA-g-Jeffamine to mediate an antisense effect. Therefore, we are investigating the mechanisms of endocytosis by which these various DOTAP based delivery systems are taken up by cells and how this influences antisense activity. In summary, our work 1) introduces a novel excipient for ODN delivery and, 2) aims to understand the influence of carrier chemistry and cell specific characteristics on efficiency of ODN delivery and antisense activity.