(109c) A Photo-Degradable Gene Delivery System for Enhanced Gene Transcription

Polymer-based gene carriers, though promising as safer alternatives to viral gene carriers, have yet been limited in large part due to their poor transfection performance. Future design and development of better polycation gene carriers will be greatly facilitated by an improved understanding of the relationship between the polycation chemistry and performance mechanism. In particular, there exists a significant gap in our understanding of how the size and compactness of polycation carriers influence their delivery performances in overcoming the most important cellular-level transport barrier, i.e., nuclear entry. In order to study this problem, we developed a photo-degradable polymer DNA carrier that is degradable upon exposure to mild UV irradiation; this carrier allows us to control the precise location of the disintegration of the PEI/DNA polyplex particles within the intracellular environment. By using this photolytic DNA carrier, we found that the exact (timing and) location of the photo degradation (i.e., cytosol, nucleus or no degradation) significantly influence the nuclear localization and the gene transfection efficiencies of the polymer/DNA complexes; the degradation of the carrier molecules impacts not only the size characteristics of the associated polyplexes which directly influence their nuclear import properties, but also the capabilities of the polyplexes to protect (against endonucleases) and release (for polymerase transcription) DNA which both impact the final gene expression levels.