(642d) Design of Biodegradable Layer-By-Layer Films Capable of Localized, Efficient, and Sequential Gene Delivery

Layer-by-layer (LbL) films containing cationic polyelectrolyte and anionic bioactive molecules such as DNA are promising biomaterials for controlled and localized gene delivery for a number of biomedical applications such as cancer DNA vaccine delivery and tissue engineering. The LbL technique allows a wide variety of biological molecules including DNA, RNA, protein, and peptides to be incorporated into surface coating with exact amount and spatial distribution. Additionally, the release time and dosage are controllable by the LbL film-based gene delivery vehicle. Although nonviral gene delivery vectors generally show lower cytotoxicity than their viral counterpart, their low transfection efficiency prevents their clinical translation. In order to improve the transfection efficiency, we synthesized a novel bioreducible poly(amido amine) (PAA). We incorporated a highly transfecting monomer, 5-amino-1-pentanol (APOL) into the PAA molecular structure. We also modified this new type PAA with different amount of disulfide bond. The disulfide bond here can be reduced in target cell thus enabling DNA release from the polymer/DNA complex. The buffering capacity of the new APOL-containing PAA in the relevant intracellular pH range was higher than poly(ethyleneimine) (PEI) as well as the PAA without APOL. The high transfection efficiency of the APOL-PAA was confirmed by in vitro experiments using HEK 293, NIH 3T3, and MC 3T3 cells. We chose the highest transfecting APOL-PAA and applied it into our LbL film design. We observed increased transfection in the APOL-PAA containing LbL films. We also modified the LbL interior structure by incorporating non-biodegradable PEI as a barrier layer to achieve sequential disassembly and sustained DNA release. Moreover, by using two different DNA plasmids embedded in different layers of the LbL film, the two types of DNA were shown to be released at different times. Our study contributes new molecular and LbL film designs for improved DNA delivery based on the LbL film technique.