223. In Vitro Gene Transfer from a DNA-PEI Loaded Polylactide-Glycolide Porous Sponge

Abstract

Polylactic-co-glycolic acid (PLGA) matrices are common in tissue engineering applications and can be used as implantable gene delivery devices. Using a gas foaming process, we have previously reported the formulation of highly porous, bioerodable PLGA sponges that incorporate PEI-DNA in a bulk loading process 1. The in vitro gene transfer efficiency was analyzed as a function of PEI-DNA dose, cell seeding number, expression time, and charge ratio (1). In the present study we have determined if the gene expression efficiency can be improved by surface loading of PEI-DNA onto preformed PLGA sponges. PEI-DNA condensates were loaded onto PLGA sponges while monitoring the adsorption kinetics as a function of charge ratio, dose, and PLGA to porogen ratio. Surface loading of PEI-DNA onto PLGA sponges was found to be slow (several days), to yield lower load levels of DNA relative to bulk loading and occurred at an optimal PEI-DNA charge ratio of 4. Surface loaded PEI-DNA remained bound to PLGA sponges despite prolonged incubation in complex media. In vitro gene transfer experiments revealed that surface bound PLGA sponges were transfection competent; however, the levels of gene expression was significantly less than optimized, bulk loaded PLGA sponges. We conclude that bulk loaded PEI-DNA PLGA sponges have several advantages over surface loaded sponges. These results should help in the further design of these implantable gene delivery systems. (Supported by grant NIH DE 13004)