SIZE, DIFFUSIBILITY AND TRANSFECTION PERFORMANCE OF LINEAR PEI DNA COMPLEXES IN THE MOUSE CENTRAL-NERVOUS-SYSTEM/

Currently in vivo gene delivery by synthetic vectors ix limited diffus ibility of complexes in extracellular fluids and matrices. Here we sho w that certain formulations of plasmid DNA with linear polyethylenimin e (22 kDa PEI, ExGene 500) can produce complexes that are sufficiently small and stable in physiological fluids so as to provide high diffus ibility. When plasmid DNA was formulated with 22 kDa PEI in 5% glucose , it produced a homogeneous population of complexes with mean diameter s ranging from 30 So 100 nm according to the amount oi PEI used, in co ntrast, formulation in physiological saline produced complexes an orde r oi magnitude greater (greater than or equal to 1 mu m). Intraventric ular injection of complexes formulated in glucose showed the complexes to be highly diffusible in the cerebrospinal fluid of newborn and adu lt mice, diffusing from a single site of injection throughout the enti re brain ventricular spaces. Transfection efficiency was followed by h istochemistry of beta-galactosidase activity and double immunocytochem istry was used to identify the cells transfected. Transgene expression was found in both neurons and glia adjacent to ventricular spaces. Th us, this method of formulation is promising for in vivo work and may w ell be adaptable to other vectors and physiological models.