Non-viral gene delivery: from the needle to the nucleus.

Despite nearly two decades of research, the successful application of systemically delivered non-viral gene therapies to treat human disease is still limited by poor transfection efficiency. The major barriers in the circulation and in the cell that limit transfection efficiency have been identified and the field has entered a phase of design and testing of more sophisticated carrier systems that attempt to circumvent these barriers. These studies are increasingly conducted in vivo using rapid quantitative measures of gene transfer efficiency as a guide. Although there has been steady progress in developing DNA nanoparticles that navigate the circulation, enter the target cell and escape lysosomal targeting, the final goal of efficiently traversing the nuclear membrane remains the most significant challenge. The ultimate goal is to develop elegant delivery systems that work in concert to deliver DNA from the needle to the nucleus.