Non-viral vector delivery from PEG-hyaluronic acid hydrogels

Hydrogels have been widely used in tissue engineering as a support for tissue formation or to deliver non-viral gene therapy vectors locally. Hydrogels that combine these functionalities can provide a fundamental tool to promote specific cellular processes leading to tissue formation. This report investigates controlled release of gene therapy vectors from hydrogels as a function of the physical properties for both the hydrogel and the vector. Hydrogels were formed by photocrosslinking acryl-modified hyaluronic acid (HA) with a 4-arm poly(ethylene glycol) (PEG) acryl. The polymer content, and relative composition of HA and PEG modulated the swelling ratio, water content, and degradation, which can influence transport of the vector through the hydrogel. All hydrogels had a water content of 94% or higher, though the water content and swelling ratio increased with a decrease in the PEG:HA ratio. Plasmids were stably incorporated into the hydrogel, with a majority of the release occurring during the initial 2 days. For incubation in buffer, the cumulative release increased with a decreasing PEG or increasing HA content, with approximately 20% to 80% released during the first week depending on the hydrogel composition. Hydrogels incubated in hyaluronidase, an enzyme that degrades HA, significantly increased plasmid release for hydrogels containing 4% PEG and 4% HA-Acryl. The encapsulation of plasmid complexed with polyethylenimine had less than 14% of the complexes released from the hydrogel both in the presence and absence of hyaluronidase. The limited release of the complexes likely results from the complex size and interactions between the vector and hydrogel. These studies demonstrate the dependence of non-viral vector release on the physical properties of the hydrogel and the vector, suggesting vector and hydrogel designs for maximizing localized delivery of non-viral vectors.