Highly PEGylated DNA Nanoparticles Provide Uniform and Widespread Gene Transfer in the Brain.

Gene delivery to the central nervous system (CNS) has potential as a means for treating numerous debilitating neurological diseases. Non-viral gene vector platforms are tailorable and can overcome key limitations intrinsic to virus-mediated delivery; however, lack of clinical efficacy with non-viral systems to date may be attributed to limited gene vector dispersion and transfection in vivo. We show that the brain extracellular matrix strongly limits penetration of polymer-based gene vector nanoparticles through the brain parenchyma, even when they are very small (<60 nm) and coated with a polyethylene glycol (PEG) corona of typical density. Following convection enhanced delivery (CED), these “conventional gene vectors” were confined to the injection site, presumably by adhesive interactions with the brain extracellular matrix, and did not provide gene expression beyond the point of administration. In contrast, we found that incorporating highly PEGylated polymers allowed production of compacted (~43 nm) and colloidally stable DNA nanoparticles that avoided adhesive trapping within the brain parenchyma. When administered by CED into the rat striatum, highly PEGylated DNA nanoparticles distributed throughout and provided broad transgene expression without vector-induced toxicity. The use of these “brain-penetrating gene vectors”, in conjunction with CED, offers an avenue to improve gene therapy for CNS diseases.