Cellular delivery of antisense oligonucleotides.

Antisense oligonucleotides can be successfully employed to inhibit specifically gene expression. However, many oligonucleotide classes are polyanions and cannot passively transit the cell membrane. Thus, the use of naked oligonucleotides for antisense purposes poses some rather stringent challenges, and it is not a trivial task to appropriately interpret the data derived from experiments in which they have been used. Multiple methods have been developed to improve intracellular, and in particular, intranuclear oligonucleotide delivery, and in doing so, to maximize the performance of the antisense technologies that are currently available. This review discusses the use of cationic lipids, protein and peptide delivery agents, and several novel chemical and viral methods that have recently been explored as delivery vehicles, focussing not only on their strengths, but also on their limitations.