Effective incorporation of 2'-o-methyl-oligoribonuclectides into liposomes and enhanced cell association through modification with thiocholesterol

Abstract

Cholesterol was linked to 2'-O-methyI-oligoriboin)uclleotides (2'-OMe-RNA) via a disulfide bond by reacting the 3'-(pyridyldithio)-moditfied 2'-OMe-RNA with thiochoIesteroD on dichloromethane-metfaoTioll solution. This ligation reaction was made possible by a novel strategy on which the highly charged oligonucleotide was rendered soluble in nonaqueous solvent through conversion to a lipophilic amidinium salt. The biodegradable lipophilic modification of 2'-OMe-RNA resulted in a large increase in incorporation of such oligonucleotides into liposomes prepared by reverse-phase evaporation. Furthermore, association of these modified oligonucleotides with celltured TIB 73 cells was 100-fold higher than that seen with unmodified 2'-OMe-RNA in serum-free medium and about 10 to 30-fold higher on the presence of 10% calf serum. During incubation with cells, release of the internalized oligonucleotide from the thiocholesteryD moiety can be demonstrated. © 1992 Oxford University Press.