Preparation and characterization of liposome-encapsulated plasmid DNA for gene delivery

The success of common nonviral gene delivery vehicles, lipoplexes and polyplexes, is limited by the toxicity and instability of these charged molecules. Stealth liposomes could provide a stable, safe alternative to cationic DNA complexes for effective gene delivery. DNA encapsulations in three stealth liposomal formulations prepared by thin film, reverse phase evaporation, and asymmetric liposome formation were compared, and the thin film method was found to produce the highest yields of encapsulated DNA. A DNA quantification method appropriate for DNA encapsulated within liposomes was also developed and verified for accuracy. The effect of initial lipid and DNA concentrations on the encapsulation yield and fraction of DNA-filled liposomes was evaluated. Higher encapsulation yields were achieved by higher lipid contents, while a higher fraction of DNA-filled liposomes was produced by either lower lipid content or higher DNA concentration. Control of these parameters allows for the design of gene delivery nanoparticles with high DNA encapsulation yields or higher fraction of DNA-filled liposomes.