(256i) Interfacial Engineering of Biodegradable Polyelectrolyte Multilayer Thin Films for Sequential and Sustained DNA Delivery

Polyelectrolyte multilayer (PEM) thin films containing anionic bioactive molecules such as DNA and synthetic polycations as carriers are promising biomaterials for localized nucleic acid delivery. Layer-by-layer (LbL) techniques of assembling PEMs have been widely applied for biomedical coatings due to their ability to encapsulate a wide range of biomolecules and their ability to deposit on various biomedical substrates such as Ti. Our research focuses on the synthesis and interfacial engineering of a novel bioreducible LbL film platform in order to achieve high efficiency and sustained DNA release in cellular microenvironments. Poly(amido amine) (PAA) containing the disulfide bond as gene delivery vector has been extensively investigated in our previous work. The disulfide bond in the polymer structure is predominantly reduced in target cells and cell nuclei due to the endogenous redox gradient in cellular microenvironments. Currently, we incorporated a highly transfecting monomer, 5-amino-1-pentanol (APOL), into the PAA molecular structure in order to further improve the transfection efficiency. In order to avoid bulk DNA release, we periodically inserted nonbioreducible polycations such as poly(ethyleneimine) (PEI) into the film as a barrier layer to slow down the film degradation rate. In order to understand the relationship between film assembly and film disassembly, we characterized the film structure using in situ atomic force microscopy, fluorescence spectroscopy, and dynamic light scattering. We tested DNA release from the film in vitro using HEK 293, MC 3T3, and NIH 3T3 cells. We found that film transfection can last more than one week. In addition, we incorporated two types of DNA plasmids into the LbL film at different layers.. This design is intended to demonstrate the dual stage release pattern of the LbL film, which is desirable for DNA vaccine delivery and tissue engineering applications. Our study contributes to the understanding of basic relationships among films assembly and disassembly, polycation molecular structure, and interfacial LbL film structure for improved use of LbL films as gene delivery vehicles.