DNA nanoparticles and development of DNA delivery vehicles for gene therapy

DNA transport through the cell membrane is an essential requirement for gene therapy, which utilizes oligonucleotides and plasmid DNA. However, membrane transport of DNA is an inefficient process, and the mechanism(s) by which this process occurs is not clear. Although viral vectors are effective in gene therapy, the immune response elicited by viral proteins poses a major problem. Therefore, several laboratories are involved in the development of nonviral DNA delivery vehicles. These vehicles include polyamines, polycationic lipids, and neutral polymers, capable of condensing DNA to nanoparticles with radii of 20-100 nm. Although the structural and energetic forces involved in DNA condensation have been studied by physical biochemists for the past 25 years, this area has experienced a resurgence of interest in recent years because of the influx of biotechnologists involved in developing gene therapy protocols to combat a variety of human diseases. Despite an intense effort to study the mechanism(s) of DNA condensation using a variety of microscopic, light scattering, fluorescence, and calorimetric techniques, the precise details of the energetics of DNA nanciparticle formation and their packing assembly are not known at present. Future studies aimed at defining the mechanism(s) of DNA compaction and structural features of DNA nanoparticles might aid in the development of novel gene delivery vehicles.