Glucuronate-modified liposomes with prolonged circulation time.

For the purpose of obtaining liposomes with long circulation time in blood, we synthesized 1-O-palmityl-D-glucuronic acid (PGlcUA) and incorporated it into the liposomal membranes. The clearance of the PGlcUA-liposomes composed of dipalmitoylphosphatidylcholine (DPPC), cholesterol, and PGlcUA (40:40:20 as a molar ratio) from blood and their tissue distribution were compared with those of dipalmitoylphosphatidylglycerol (DPPG)-liposomes (DPPC/cholesterol/DPPG = 40:40:20). When [3H]inulin-loaded PGlcUA-liposomes and DPPG-liposomes were intravenously injected into rats, the half-life of the PGlcUA-liposomes in the blood appeared to be 1.7-fold longer than that of DPPG-liposomes. Radioactivities present in plasma and various tissues were measured 22 h after administration of these liposomes, and radioactivity remaining in the plasma was 2.5-fold greater when PGlcUA-liposomes were injected. The distribution pattern of [3H]inulin in PGlcUA-liposomes was similar to that in DPPG-liposomes. The radioactivity recovered in urine was 25% lower in rats treated with PGlcUA-liposomes than in those treated with DPPG-liposomes. Since both PGlcUA- and DPPG-liposomes exhibited similar size distribution and zeta-potential, glucuronic acid, rather than negative charge, on the liposomal surface appears to endow liposomes with a longer circulation time in the bloodstream.