@article {217136,
	title = {Long-term in vivo gene expression via delivery of PEI-DNA condensates from porous polymer scaffolds},
	journal = {Hum Gene Ther},
	volume = {16},
	number = {5},
	year = {2005},
	month = {2005 May},
	pages = {609-17},
	abstract = {Nonviral delivery vectors are attractive for gene therapy approaches in tissue engineering, but suffer from low transfection efficiency and short-term gene expression. We hypothesized that the sustained delivery of poly(ethylenimine) (PEI)-condensed DNA from three-dimensional biodegradable scaffolds that encourage cell infiltration could greatly enhance gene expression. To test this hypothesis, a PEI-condensed plasmid encoding beta-galactosidase was incorporated into porous poly(lactide-co-glycolide) (PLG) scaffolds, using a gas foaming process. Four conditions were examined: condensed DNA and uncondensed DNA encapsulated into PLG scaffolds, blank scaffolds, and bolus delivery of condensed DNA in combination with implantation of PLG scaffolds. Implantation of scaffolds incorporating condensed beta-galactosidase plasmid into the subcutaneous tissue of rats resulted in a high level of gene expression for the entire 15-week duration of the experiment, as exemplified by extensive positive staining for beta-galactosidase gene expression observed on the exterior surface and throughout the cross-sections of the explanted scaffolds. No positive staining could be observed for the control conditions either on the exterior surface or in the cross-section at 8- and 15-week time points. In addition, a high percentage (55-60\%) of cells within scaffolds incorporating condensed DNA at 15 weeks demonstrated expression of the DNA, confirming the sustained uptake and expression of the encapsulated plasmid DNA. Quantitative analysis of beta-galactosidase gene expression revealed that expression levels in scaffolds incorporating condensed DNA were one order of magnitude higher than those of other conditions at the 2- week time point and nearly two orders of magnitude higher than those of the control conditions at the 8- and 15-week time points. This study demonstrated that the sustained delivery of PEI-condensed plasmid DNA from PLG scaffolds led to an in vivo long-term and high level of gene expression, and this system may find application in areas such as bone tissue engineering.},
	keywords = {Animals, beta-Galactosidase, DNA, Feasibility Studies, Freeze Drying, Gene Expression, Genetic Therapy, Genetic Vectors, Kinetics, Lactic Acid, Male, Plasmids, Polyethyleneimine, Polyglycolic Acid, Polymers, Porosity, Rats, Rats, Inbred Lew, Tissue Engineering, Transfection},
	issn = {1043-0342},
	doi = {10.1089/hum.2005.16.609},
	author = {Huang, Yen-Chen and Riddle, Kathryn and Rice, Kevin G and Mooney, David J}
}
