Design of Multilayered Films for the Localized Delivery of DNA to Cells

The design of thin films and coatings that sustain the release of DNA from the surfaces of biomedical devices could have a great impact on localized gene therapy. Here, we describe the design of multilayered polyelectrolyte assemblies that can sustain the release of functional DNA by using a new synthetic and hydrolytically degradable polyamine. Multilayered films were fabricated from alternating layers of this degradable polymer and plasmid DNA encoding for enhanced green fluorescent protein (EGFP) through layer-by-layer assembly. The thickness of the films was measured by ellipsometry and it was found that films up to 150 nm could be fabricated. The release of DNA was studied by incubating the films in phosphate buffered saline (PBS) solutions at 37°C and pH 7.2. Results from UV-vis spectrophotometry and agarose gel electrophoresis demonstrated that DNA was released slowly from these films for up to 15 days. Moreover, cell transfection experiments demonstrated that the DNA released was transcriptionally active and that COS-7 cells were able to express the EGFP. Characterization of film surfaces was conducted by atomic force microscopy and the results demonstrated that the films stayed smooth during erosion. This result is consistent with the view that the film undergoes "top-down" erosion. The materials and design techniques presented here represent an attractive framework for the localized delivery of DNA from the surfaces of biomedical devices.