Liposomes: conquering the nuclear barrier.

The field of non-viral vector gene therapy has become increasingly successful due to the production of improved liposomes, polymers and other formulations. These novel vectors have increased the amount of DNA delivered to cells both in vitro and in vivo, and in turn, have increased gene expression. However, DNA transport to the nucleus still remains one of the largest problems in obtaining efficient, high levels of gene expression. This review addresses the reasons why the nucleus is a major barrier to transfected DNA and introduces the cytoplasmic expression system as a possible alternative to nuclear expression.