Hepatic accumulation of glutamic acid branched neogalactosyllipid modified liposomes.

We synthesized branched type galactosyllipid derivatives for liposome modification for the targeting of asialoglycoprotein receptors on the surface of liver cells. Galactose was coupled to the alpha- and gamma-carboxyl groups of glutamic acid via a triethyleneglycol spacer, then this glutamic moiety was bound to the lipid anchor. Ricinus communis agglutinin (RCA120) induced the agglutination of liposomes modified with mono-, bi- and tri-antennary neogalactosyllipid. With the bi- or tri-antennary derivatives, agglutination was observed at fewer galactosyl residues on the liposomes. We examined the effect of the branching structure in vivo. The difference in accumulation of liposomes between non-branched type neogalactosyllipid and branched type neogalactosyllipid was not large. Liver accumulation of liposomes depended on the galactosyl residues. The number of galactosyl residues was more effective for accumulation in the liver than for branching. We studied the effect of asialofetuin preinjection on the hepatic accumulation of neogalactosyllipid modified liposomes. Hepatic accumulation of liposomes was inhibited by preinjection of asialofetuin. The effect of preinjection was almost equal among the ligands. These results show that the saccharide density on the liposome surface seemed to be a more important factor than the branching structure of the ligand for liver targeting.