Lipoplex-mediated delivery of nucleic acids: factors affecting in vivo transfection

For the past 15 years cationic liposomes have routinely been utilised for the delivery of nucleic acids such as plasmids and oligodeoxynucleotides to cells in culture and in vivo. These reagents are commercially available or are formulated inhouse. However, particularly in cultured cells, toxicity remains a significant problem, and this is confirmed by several in vivo findings. In addition, these complexes exhibit an immunostimulation effect, a phenomenon that may either be harmful or beneficial. Furthermore, lipoplexes have been recently found to have a certain degree of selectivity for dividing vascular endothelial cells. The development of cationic lipids that are safe to use especially in vivo and possess enhanced transfection capabilities is an ongoing process. More research is needed to understand the basic biology behind lipofection, first at the cellular level, then at the multicellular (whole organism) level.