Layer-by-layer DNA films incorporating highly transfecting bioreducible poly(amido amine) and polyethylenimine for sequential gene delivery

Background: The layer-by-layer (LbL) assembly method offers a molecular level control of the amount and spatial distribution of bioactive molecules. However, successful clinical translation of LbL film technology will most certainly require a better understanding and control of not only the film assembly process, but also film disassembly kinetics in physiologic conditions. Purpose: This work focuses on the understanding and control of degradation properties of LbL films for localized gene delivery. Methods: Bioreducible poly(amido amine) s (PAAs) containing cystaminebisacrylamide (CBA), methylenebisacrylamide, and 5-amino-1-pentanol (APOL) were synthesized by Michael addition polymerization for the construction of bioreducible LbL films capable of sequential gene delivery. Results: The synthesized PAAs were screened for desirable buffering capacity, cell transfection, and cytotoxicity characteristics together with 25 kDa branched polyethylenimine (PEI) and crosslinked 800 Da PEI. By screening the various polycations we were able to identify a copolymer of CBA and APOL for the subsequent construction of the LbL films. By incorporating a highly transfecting polycation and a nondiffusing polycation we were able to improve the overall transfection of HEK293 and MC3T3 cells from the bioreducible LbL films. We also demonstrated the dual-stage release and transfection of two different DNAs from the LbL films. Conclusion: The results indicate that LbL films consisting of bioreducible PAAs and nondiffusing polyelectrolytes have excellent degradation properties for the development of LbL coating technology for localized gene delivery applications.