Characterization of DNA release from composites of oligo(poly(ethylene glycol) fumarate) and cationized gelatin microspheres in vitro

This research investigates the release of plasmid DNA from novel hydrogel composites of oligo(poly(ethylene glycol) fumarate) (OPF) and cationized gelatin microspheres (CGMS), as well as the swelling and degradation of these materials in vitro. The release of total DNA and of double-stranded DNA was measured fluorescently, and the swelling properties and polymer mass loss of the hydrogels were assessed. Further, the structural integrity of the released DNA was determined through electrophoresis. It was found that plasmid DNA can be released in a sustained fashion over the course of up to 49-140 days in vitro from hydrogels of OPF synthesized from poly(ethylene glycol) of nominal molecular weights of 10 kDa and 3 kDa, respectively, with the release kinetics depending upon the material composition and the method of DNA loading. Released DNA was predominately double-stranded DNA (dsDNA) in structure and of the open-circular conformation. The results suggest that DNA release from hydrogel composites of OPF and CGMS is dominated by the degradation of the OPF component of the gels. Electrophoresis results indicate that the released DNA retains suitable conformation for potential bioactivity over the course of at least 63 days of release. Thus, these studies demonstrate the potential of composites of OPF and CGMS in controlled gene delivery applications.