No abstract

Gene delivery using injectable hydrogels can serve as a potential method for regulated tissue regeneration in wound healing. Our microporous annealed particle (MAP) hydrogel has been shown to promote cellular infiltration in both skin and brain wounds, while reducing inflammation. Although the scaffold itself can promote healing, likely other signals will be required to promote healing of hard to treat wounds. Gene delivery is one approach to introduce desired bioactive signals. In this study, we investigated how the properties of MAP hydrogels influence non-viral gene delivery of polyethylenimine (PEI) condensed plasmid to cells seeded within the MAP gel. From past studies, we found that gene transfer to cells seeded in tissue culture plastic differed from gene transfer to cells seeded inside hydrogel scaffolds. Since MAP scaffolds are generated from hydrogel microparticles that are approximately 100μm in diameter, they display local characteristics that can be viewed as two dimensional or three dimensional to cells. Thus, we sought to study if gene transfer inside MAP scaffolds differed to gene transfer to cells seeded in tissue culture plastic. We sought to understand the roles of endocytosis pathway, actin and microtubule dynamics, RhoGTPases, and YAP/TAZ on transfection of human fibroblasts.

Nucleic acid delivery has applications ranging from tissue engineering to vaccine development to infectious disease. Cationic polymer condensed nucleic acids are used with surface‐coated porous scaffolds and are able to promote long‐term gene expression. However, due to surface loading of the scaffold, there is a limit to the amount of nucleic acid that can be loaded, resulting in decreasing expression rate over time. In addition, surface‐coated scaffolds are generally non‐injectable. Here, it is demonstrated that cationic polymer condensed nucleic acids can be effectively loaded into injectable granular hydrogel scaffolds by stabilizing the condensed nucleic acid into a lyophilized powder, loading the powder into a bulk hydrogel, and then fragmenting the loaded hydrogel. The resulting hydrogel microparticles contain non‐aggregated nucleic acid particles, can be annealed post‐injection to result in an injectable microporous hydrogel, and can effectively deliver nucleic acids to embedded cells with a constant expression rate. Due to the nature of granular hydrogels, it is demonstrated that mixtures of loaded and unloaded particles and spatially resolved gene expression can be easily achieved. The ability to express genes long term from an injectable porous hydrogel will further open the applications of nucleic acid delivery.