We sought to exploit glycosylated poly-L-lysine (pLK) to increase the uptake and biological antisense activity of a phosphorothioate oligonucleotide (pt-odn) [pt-odn complementary to the 3' noncoding region of intercellular adhesion molecule-1 (ICAM-1) (odn(ICAM-1))] complementary to the 3'-noncoding region of ICAM-1 in A549 cells. Dose-dependent inhibition of ICAM-1 expression was obtained (IC50 = 500 nM) through treatment of cells with odn(ICAM-1) complexed with pLK carrying fucose residues in the presence of 100 microM chloroquine. Alteration in the charge ratio between fucosylated pLK and pt-odn had a significant effect on the efficacy of inhibition (optimal conditions, charge ratio = 1.1). This effect was also dependent on the number of fucose moieties per pLK. Free pt-odn or pt-odn complexed with nonglycosylated pLK gave no inhibition at concentrations of < or = 2 microM. Two control pt-odn (one was targeted against an unrelated gene not present in these cells, gag(HIV), and the other had a randomized sequence) gave no inhibition of ICAM-1 expression in the presence or absence of pLK carrying fucose residues at concentrations of < or = 2 microM. When complexed with pLK carrying 100 fucose residues, the amount of cell-associated pt-odn was increased by 15-fold compared with the free pt-odn. Nongycosylated pLK also increased the amount of cell-associated pt-odn by >10 fold but did not alter the biological activity. These results demonstrate clearly the potential of glycosylated pLK as a pt-odn transporter.