Syntheses of Novel Galactosyl Ligands for Liposomes and the Influence of the Spacer on Accumulation in the Rat Liver

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We modified the surface of liposomes with galactosyl ligands. At first we determined whether or not the galactosyl moiety was exposed on the liposomes. We then investigated the effect of the ligands on the hepatic accumulation of liposomes in rats. We introduced an oligoethylene glycol moiety as a spacer. Among the various ligands tested, those with a tri-or tetraethylene glycol moiety as a spacer caused the greatest accumulation of liposomes in the liver. Liposomes bearing ligands with a tri-or tetraethylene glycol moiety as a spacer, were aggregated by Ricinus communis agglutinin. On the other hand, those modified with ligands with a mono- or diethylene glycol spacer did not clearly agglutinate. These results show the importance of a spacer between the homing device and the ligand anchor.