Effects of blood on the uptake of charged liposomes by perfused rat liver: Cationic glucosamine-modified liposomes interact with erythrocyte and escape phagocytosis by macrophages

The uptake of liposomes by rat liver was investigated by perfusion. Positively and negatively charged liposomes were taken up to a greater extent than neutral liposomes in Hanks' buffer. However, the uptake of cationic glucosamine-modified (PGlcN) liposomes was suppressed when blood was added to the perfusate, while the uptake of negatively charged phosphatidylserine (PS) and neutral liposomes was enhanced, probably due to the action of opsonins. The uptake of cationic PGlcN-liposomes by the liver was suppressed when red blood cells were added to the perfusate, while uptake was little affected in the presence of serum. These results revealed that rat erythrocytes play an important role in the capacity of cationic liposomes to avoid uptake by the reticuloendothelial system (RES). Cationic PGlcN-liposomes bound to rat erythrocytes weakly; however, the zeta potential of erythrocytes increased in the presence of cationic PGlcN-liposomes and showed homogeneous distribution. Cationic PGlcN-liposomes may surround the erythrocytes with an ionic atmosphere. Cationic PGlcN-liposomes would interact with erythrocytes through electrostatic interaction and could thus escape phagocytosis by macrophages. (C) 1997 Elsevier Science B.V.