Antisense
oligodeoxynucleotides (asODN) are novel therapeutic agents designed to alter
RNA metabolism, ultimately resulting in decreased production of disease-associated gene products. To investigate internalisation of liposomally delivered asODN in NG108-15 cells, a hybrid cell line of mouse
neuroblastoma and rat
glioma, and assure that uptake of marker corresponds to that of antisense, we compared the cellular uptake of fluorescently labelled marker (
fluorescein isothiocyanate (
FITC)-dextran) and
antisense oligonucleotide (
FITC-asODN), entrapped either in conventional soy
phosphatidylcholine (SPC)
liposomes or pH-sensitive
liposomes (composed of
dioleoylphosphatidylethanolamine and
cholesteryl hemisuccinate in a molar ratio of 3 : 2). Both SPC and pH-sensitive
liposomes were prepared by a modified freeze-thawing method. Entrapment efficiencies (about 20% of the original material) did not depend on the
liposome compositions and fluorescent material used. Fluorescence activated cell sorting (FACS) analysis was used to quantify the association of fluorescent material with the NG108-15 cells, whereas confocal microscopy gave insight on the location of cell associated-fluorescence. Conventional
liposomes failed to deliver fluorescent material into the cells, but in contrast, pH-sensitive
liposomes significantly improved the uptake of both
FITC-dextran and
FITC-asODN, with the uptake of liposomal
FITC-dextran being greater than the uptake of liposomal
FITC-asODN. These results suggest that pH-sensitive
liposomes can be applied as a carrier system in the delivery of genetic material into the cells.