Physicochemical and Biological Characterization of Degradable Polyelectrolyte Multilayers For Surface-Mediated DNA Delivery

The work described in this thesis focuses on the evaluation of synthetic organic materials to either (i) mediate the delivery of DNA from thin polymer films on surfaces or (ii) create functional coatings on surfaces with potential biomedical applications related to drug delivery and cell adhesion. In both cases, layer-by-layer fabrication was used to assemble films on surfaces through the iterative immersion of substrates in alternating solutions of complementary functionality (e.g. alternating solutions of polycations and polyanions or alternating solutions of organic materials possessing nucleophilic or electrophilic functional groups in order to create polyelectrolyte and covalent multilayers, respectively). The DNA-related studies build upon previous work demonstrating that films fabricated using a hydrolytically degradable cationic polymer can release DNA over a period of one to two days and promote transgene expression both in vitro and in vivo. Chapter 2 reports the synthesis of a fluorescently end-labeled degradable cationic polymer and its application to characterize the erosion of polyelectrolyte multilayers fabricated using a model polyanion. Chapter 3 used this fluorescently labeled cationic polymer to provide more direct insight into fundamental interactions between the polymer and DNA during release from films and during trafficking by cells in vitro. The results of this chapter suggest that the polymer components of these films can play a role in promoting cellular uptake and trafficking of DNA. Chapter 4 characterized the application of this DNA-containing film system to deliver DNA encoding a potential therapeutic protein to investigate the extent to which this method of delivery could be used to reduce intimal hyperplasia in arterial tissue of rats after balloon-mediated injury. The results of this study provide guidance for the development of degradable polyelectrolyte multilayered thin films for the surface-mediated delivery of DNA. Chapter 5 demonstrated layer-by-layer fabrication of covalent films using a branched polyamine and small molecule pentacrylate to yield films possessing hydrolytically degradable ester bonds. These films were subsequently functionalized using unreacted acrylate groups to control film hydrophobicity and cell adhesion and provided a platform for the release of covalently attached molecules upon incubation in aqueous media.