Controlled release of plasmid DNA

Very large molecular weight reporter plasmids (pCMV-beta gal, pSV-beta gal) and lower molecular weight (herring sperm) DNA were encapsulated in polyethylene vinyl co-acetate (EVAc). In vitro release studies were performed to determine release rates and duration of delivery. The swelling behavior and morphological changes of these formulations were studied to elucidate the potential mechanism of DNA release. The bioactivity of the released plasmid DNA was assessed through analysis of conformation using agarose gel electrophoresis and in vitro transfection of C2C12 myoblasts using liposome (Lipofectin(TM)) complexation. Extraction of plasmid DNA from the delivery systems indicated that the fabrication conditions did not degrade the DNA. Depending on initial DNA loading, detectable levels were released for 1-6 months. Pore formation was accompanied by swelling which varied according to DNA loading as well as the type of DNA (herring sperm, plasmid). Conformational analysis of released plasmid DNA showed DNA was released without degradation and retained the ability to transfect cells in vitro. The results demonstrate that controlled release systems can be fabricated for the release of very large molecular weight plasmid DNA which may provide an alternative approach to plasmid-based gene transfer.