Sustained delivery and expression of DNA encapsulated in polymeric nanoparticles

Sustained release polymeric gene delivery systems offer increased resistanc e to nuclease degradation, increased amounts of plasmid DNA (pDNA) uptake, and the possibility of control in dosing and sustained duration of pDNA adm inistration. Furthermore, such a system lacks the inherent problems associa ted with viral vectors. Biodegradable and biocompatible poly(DL-lactide-co- glycolide) polymer was used to enacapsulate pDNA (alkaline phosphatase, AP, a reporter gene) in submicron size particles. Gene expression mediated by the nanoparticles (NP) was evaluated in vitro and in vivo in comparison to cationic-liposome delivery. Nano size range (600 nm) pDNA-loaded in poly(DL -lactide-co-glycolide) polymer particles with high encapsulation efficiency (70%) were formulated, exhibiting sustained release of pDNA of over a mont h. The entrapped plasmid maintained its structural and functional integrity . In vitro transfection by pDNA-NP resulted in significantly higher express ion levels in comparison to naked pDNA. Furthermore, AP levels increased wh en the transfection time was extended, indicating sustained activity of pDN A. However, gene expression was significantly lower in comparison with stan dard liposomal transfection. Seven days after i.m. injections in rats, nake d pDNA and pDNA-NP were found to be significantly more potent (1-2 orders o f magnitude) than liposomal pDNA. Plasmid DNA-NP treatment exhibited increa sed AP expression after 7 and 28 days indicating sustained activity of the NP.