Drug-Carrier and Stability Properties of the Long-Lived Lipid Vesicles. Cryptosomes,in Vitro and in Vivo

Abstract

Lipid vesicles composed of phosphatidylcholine and suitable polyoxyethylene-derivat-ives of phosphatidylethanolamine (cryptosomes) remain in circulation 8–10 times longer than standard liposomes after an i.v. administration in mice. In contrast to previous belief, this longevity is not destroyed by the net charges on the lipid vesicle surface and is not a direct consequence of the high surface hydrophilicity; also bilayer fluidity is not an obstacle for the attainment of long circulation times. All these three factors, however, can affect the effectiveness of the drug encapsulation into lipid vesicles and the stability of the resulting carrier suspensions. Terminal head-group modifications, moreover, can affect the final carrier and drug distribution after vesicle applications in vivo and lead to accumulation in certain body subsites, such as the gut.