(93b) Biodegradable Hydrogels with Concentrated pDNA/PEI Polyplexes for Tissue Engineering and Regeneration

Lei, Y. - Presenter, University of California, Los Angeles

Scaffold-mediated non-viral gene delivery is promising for tissue engineering and regeneration due to its advantages of sustained & localized delivery with controlled rates. Our previous work showed plasmid DNA (pDNA)/poly(ethyleneimine) (PEI) polyplexes could be encapsulated into matrix metalloproteinase degradable poly(ethylene glycol) (PEG) hydrogels. Cells migrating in the gels were transfected multiple times, resulting in sustained transgene expression. However, only a limited amount of pDNA/PEI could be loaded because of severe aggregation at high polyplex concentrations, which limited the application of these hydrogels in vivo. To address this problem, we developed a process to make PEG hydrogels with concentrated pDNA/PEI polyplexes which remain active after encapsulation. Here, we report the application of this process to load high concentrations of pDNA/PEI polyplexes into hyaluronic acid (HA) and fibrin hydrogels, which are widely used in tissue engineering and regeneration, but are not compatible with the positively charged pDNA/PEI polyplexes as their negative charge induces severe polyplex aggregation. Through confocal microscopy, the encapsulated polyplexes were observed to be distributed in the hydrogel without aggregation. Up to 500μg pDNA condensed with PEI could be encapsulated into a 100μl hydrogel. The bioactivity of the encapsulated pDNA/PEI was tested with the Chicken Chorioallantoic Membrane (CAM) assay. Hydrogels with pVEGF/PEI polyplexes induced extensive radial blood vessel growth around the hydrogel and promoted the formation of random immature vessels within the gel area. The encapsulated pBeta-galactosidase (βGal)/PEI polyplexes were successfully transferred to the CAM and expressed as well. The gene transfer rate was observed to be proportional to the gel degradation rate. In summary, the process was successfully used to load concentrated pDNA/PEI polyplexes into HA and fibrin hydrogels.