Cell membranes as barriers for the use of antisense therapeutic agents

Antisense oligonucleotides are promising therapeutical agents for numerous diseases resulting from overexpression of genes, expression of mutant genes and viral infections. As most oligonucleotides are polyanions they can not readily pass cellular membranes in adequate amounts to show activity. Therefore, different types of carrier systems and modifications have been developed to enhance absorption and distribution at the level of tissues and cells. The current state of delivery systems will be reviewed with a major part devoted to the commonly used cationic lipids.