Target Cell Controlled and Spatially Arranged Gene Delivery from Fibrin Hydrogels

Biomaterial-mediated gene transfer has several advantages including close proximity of vectors and target cells, low cytotoxicity, and preservation of the gene delivery vehicle. Herein, we used fibrin to immobilize DNA/lipofectamine polyplexes and facilitate gene transfer in two different settings: entrapment of DNA in fibrin gels followed by addition of target cells or co-localization of DNA with cells inside the fibrin matrix. We found that co-localization of DNA with target cells yielded the highest transfection efficiency. The optimum level of gene transfer was observed at intermediate DNA concentrations (2-5 μg). Interestingly, the effect of fibrinogen concentration on transfection efficiency was strongly dependent on the mode of gene transfer. When cells were added to DNA-containing fibrin gels, transfection decreased significantly as the fibrinogen concentration increased. By contrast, cells co-localized with polyplexes were affected by fibrinogen to a lesser extent. Fibrinolytic inhibitors such as e-aminocaproic acid or aprotinin reduced gene transfer, indicating that fibrin degradation is necessary for cells to find the polyplexes and initiate gene transfer. In addition, fibrin-mediated gene delivery significantly decreased the cytotoxic effect of polyplexes. Finally, immobilized DNA polyplexes did not diffuse out of the matrix resulting in precisely localized gene transfer on defined micropatterns. Our study suggested that fibrin gels can be used to contain DNA vectors to achieve localized gene delivery in vivo as well as for design of gene arrays for high throughput gene delivery in vitro.