(442d) Direct Delivery of Non-Viral Vectors of Bone Morphogenic Proteins From Polyelectrolyte Multilayer Thin Films

The transfection of osteoprogenitor cells in or near the bone fracture site by genes coding for bone morphogenic proteins (BMP) accelerates the fracture healing process. Improvements of the efficacy of non-viral gene transfer methods for the direct delivery of these beneficial BMP genes at fracture repair sites will herald the application of gene transfer technology to this vast clinical condition. We have utilized polyelectrolyte mutilayer (PEM) thin films composed of plasmid DNA vectors encoding human BMP cDNAs and hydrolytically degradable poly (â-amino) ester to directly transfect MC3T3-E1 mouse preosteoblast cells grown on the surface of PEM thin films. MC3T3-E1 cells were able to form stable attachments to the PEM thin films, uptake the plasmid DNA vectors encoding BMP genes, and express the transgene encoded in the plasmid DNA vectors. The transfection efficiency was significantly higher for MC3T3-E1 cells growing in direct contact with the PEM thin film than for those cells growing at distal sites in the monolayer cultures. Local transfection efficiency were improved by increasing the plasmid DNA load within the PEM via increasing the number of deposited layers and also by inclusion of natural polycations (protamine and poly-L-arginine which are known to enhance DNA condensation) within the architecture of the PEM thin films. These results suggest that non-viral gene transfer of BMP genes from PEM thin films may potentially enhance the differentiation of stem cells and increase bone formation at in vivo fracture healing sites.