Nonviral gene therapy has significant clinical potential, yet itstherapeutic utility has been hindered by low transfection efficiency due to acombination of extracellular and intracellular barriers. Recent developments informulation and delivery methodology have allowed a number of advances towardhigh efficiency gene delivery to various cell types and organs. In particular, theextracellular and intracellular pharmacokinetics of plasmid DNA trafficking are better understood in a number of cell systems. Using cationic lipid or polymers (often with receptortargeting), more than 10 5 plasmids can be delivered to a single cell. Endosomolytic agents promote endosomedisruption, and include weak bases, proton-sponge polymers, fusogenic peptides, viral particles, andphotosensitizing compounds. Both classical and nonclassical nuclear localization signal (NLS) peptides havealso been tested for enhancement of the probability of nuclear import events, a major rate-limiting step inDNA delivery to nondividing cell s. For example, the M9 sequence from heterogeneous nuclearribonucleoprotein A1 (hnRNP A1) protein, a non-classical NLS, has been found to increase gene expressionlevel by more than 10 to 150-fold in a variety of cell types. This review will concentrate on the currentunderstandings of the basic mechanisms of nonviral gene delivery and new approaches in the field.
Keywords: Nonviral Gene Therapy, Plasmid DNA, Pharmacokinetics, Endosomolytic agents, Endosome disruption, Photosensitizing compounds, Nonclassical nuclear localization signal, Fusogenic peptides, Proton-sponge polymers, M9 sequence