Nanoparticle-based delivery of gene therapeutics to the blood-brain barrier

In vivo gene therapy has been held back by a lack of gene delivery systems suitable for systemic application. Among the currently developed non-viral gene delivery systems, the cationic polymer polyethylenimine (PEI) provides a promising approach. Despite high in vitro gene transfer efficiency, however, the use of PEI for systemic application is limited due to rapid blood clearance and accumulation by reticulo-endothelial system (RES) sites upon intravenous administration of PEI/DNA complexes. Therefore, it is important to improve the unfavorable in vivo behavior of PEI/DNA complexes. In this study, we prepared a new delivery system with prolonged circulation time for systemic delivery of PEI/DNA complexes. The system is based on pre-condensation of DNA with PEI followed by encapsulation of the PEI/DNA complexes into PEG-stabilized liposomes. PEI/DNA complexes were prepared with a linear PEI with MW 2.7 kDa and 20-mer double stranded oligodeoxynucleotides (dsODN) designed as decoy for nuclear factor NFκ-B. NFκ-B decoys are promising drugs for the treatment of inflammatory and immune diseases. The PEI/dsODN complexes were then entrapped into PEG-stabilized liposomes by rehydration of phospholipid film followed by membrane extrusion. The encapsulated PEI/dsODN complexes were characterized with respect to encapsulation efficiency, size distribution, surface charge, stability in serum, binding to targeting antibody, and evaluated for in vitro and in vivo behavior. Encapsulation efficiency proved to be more than 95%. The system showed a virus-like structure with ~ 130 nm diameter and neutral surface charge. The system was stable in the presence of serum. For targeting to transferrin receptors, which are highly expressed on brain endothelial cells, the encapsulated PEL/dsODN complexes were coupled to the monoclonal antibody 8D3. The targeted system was taken up by brain-derived endothelial cells in culture and effectively inhibited the NFκ-B mediated transcription pathway. The system also showed significantly decreased clearance and prolonged circulation time as compared to the naked PEI/DNA complex after intravenous administration. This targeted delivery system provides a promising tool for treatment of neuroinflammatory disease affecting the BBB. It also offers the potential for systemic delivery of other gene therapeutics.