Multilayered films fabricated from plasmid DNA and a side-chain functionalized poly(beta-amino ester): surface-type erosion and sequential release of multiple plasmid constructs from surfaces

Hydrolytically degradable polyamines can be used to fabricate multilayered polyelectrolyte films that erode and release DNA in aqueous environments. Past studies have investigated films fabricated from poly(beta-amino ester) 1 and the influence of polymer backbone structure on film erosion and the release of anionic polyelectrolytes. This investigation sought to characterize the influence of polymer side-chain structure on the stability of multilayered films in physiologically relevant media. Here, we report on the fabrication and characterization of multilayered films approximately 150 nm thick assembled from plasmid DNA and side-chain functionalized polymer 2. We observed large differences in the behavior of films fabricated from polymer 2 as compared to films fabricated from polymer 1. Whereas films fabricated from polymer 1 erode and release DNA over approximately 2 days when incubated in phosphate-buffered saline, films fabricated from polymer 2 erode and release DNA over approximately 2 weeks. In addition, whereas films fabricated from polymer 1 undergo complex nanometer-scale physical transformations in aqueous media, characterization of the surfaces of films fabricated from polymer 2 by atomic force microscopy (AFM) demonstrates that the surfaces of these materials remain smooth and uniform during erosion. The apparent surface-type erosion of these materials permits the fabrication of ultrathin films with architectures that provide control over the timing and the order in which two different DNA constructs are released from surfaces. For example, the order in which two different DNA constructs are released from films and expressed by cells can be controlled to measurable extents by the relative order in which they are deposited during fabrication. These results suggest approaches to the localized and sequential release of multiple different DNA constructs to cells or tissues from the surfaces of tissue engineering scaffolds or implantable devices coated with multilayered films.