Optimization of PEI/VEGF DNA polyplexes for potenital delivery from tissue engineering scaffolds

Non-viral vector formation by DNA complexation with cationic condensing agents is a self-assembly process driven primarily by electrostatic interactions and counterion release. DNA complexation kinetics influence three physical parameters that have a direct effect on gene delivery and expression efficiency: DNA complex geometric size, surface charge and density. We demonstrate the utility of time resolved multiangle laser light scattering (TR-MALLS) for probing polyethylenimine (PEI) based polyplex formation kinetics with plasmid DNA. Our studies utilize plasmid DNA coding for VEGF, which may be used to enhance blood vessel in-growth into cell seeded polymeric scaffolds used in tissue engineering applications. We determined PEI/DNA complex size and density in real time and monitored vector stability in various liquid formulations. Parameters such as PEI molecular weight, N/P ratio and solution pH and ionic strength were investigated systematically. The ability to accurately measure polyplex size and density may lead to improvements in the design and control of non-viral gene delivery vectors and facilitate the determination of optimal formulations.