Cellular uptake and intracellular fate of antisense oligonucleotides.

Antisense oligonucleotides and short interfering RNAs are routinely used for gene function analysis and are being developed for clinical applications. The mechanism underlying internalization of free oligonucleotides into cells is poorly understood and inefficient in most cases. Antisense oligonucleotide delivery into ex vivo cells is routinely improved by the addition of cationic lipids. New chemical modifications and vectors allowing improved cellular delivery in vivo are being developed.