ENGINEERING CELL INSTRUCTUVE MATERIALS
Hydrogels for non-viral gene delivery to promote tissue repair
Our laboratory has worked extensively to achieve efficient local non-viral gene transfer by incorporating plasmid DNA into hydrogel biomaterials that are later implanted at diseased tissue sites. We have design methods to incorporate non-viral vectors into hydrogel biomaterials without aggregation at high concentration (a common problem) and used these scaffolds for in vitro and in vivo gene delivery to promote tissue repair. In addition, we have determined that mechanical properties, ECM interactions, and polyplex properties can modulate non-viral gene transfer from hydrogel biomaterials and that the biological mechanism of gene transfer to cells when they are seeded inside a biomaterial is different to the mechanism when cells are seeded on standard tissue culture plastic.
Our current projects focus on developing injectable DNA loaded scaffolds that would be more versatile than our current DNA loaded hydrogel implants. In addition, we are investigating novel ways in which cell-material interactions can be used to enhance and guide tissue repair.
The delivery of genes has advantages over the delivery of proteins to promote tissue repair. Some of these advantages are:
1. Plasmid DNA production is significantly less complex than protein production. Thus, gene delivery can circumvent the limitations of protein expression of human proteins in microorganisms, and also can effectively deliver proteins that are either not soluble (e.g. receptors or other membrane bound proteins) or that are too large to be expressed and folded propertly.
2. Gene delivery has more oportunities for targeting desired cell populations. Both protein and gene delivery vehicles can be modified with targeting ligands to increase their uptake by desired cell populations. However, these ligands are not always completely specific. Thus, when proteins are delivered they can activate any cell they come in contact with; however, genes can be regulated at the transcription level also using tissue specific or cell specific promoters, giving genes an additional opportunity for targeting.
3. Once an effective gene delivery strategy is identified it can be used for any gene sequence (any protein). This is not so for protein delivery. A delivery strategy for one protein does not necessarily works for other proteins. This is because proteins have different thertiary and quaternary structures.
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