THE EFFECT OF POLOXAMER-407 ON LIPOSOME STABILITY AND TARGETING TO BONE-MARROW - COMPARISON WITH POLYSTYRENE MICROSPHERES

In accordance with our previous studies in the rabbit (Illum, L. and Davis, S.S., Life Sci., 40 (1987) 1553-1560), coating of model polystyrene microspheres (70 nm in size) with poloxamer-407 was found to prevent their hepatic sequestration and to redirect a significant proportion of intravenously injected particles to the bone marrow in rats. In contrast, preincubation of a stable and 'solid' small unilamellar liposome preparation (DSPC/Chol/DCP in a molar ratio of 7:7:1) with poloxamer-407 provided no evidence of poloxamer penetration or adsorption onto the vesicles, as determined by photon correlation spectroscopy and laser doppler anemometry. Further, no significant difference on biodistribution of poloxamer-preincubated liposomes was observed in comparison to control vesicles following intravenous administration into rats.