In vivo behavior of polymerized lipid vesicles.

We have investigated the blood clearance kinetics and tissue distribution of large multilamellar liposomes (MLVs) and small unilamellar liposomes (SUVs) composed of the photopolymerizable lipid bis[12-(methacryloyloxy)dodecanoyl]-L-alpha-phosphatidylcholine. Polymerized MLVs or SUVs are cleared from the bloodstream more rapidly than nonpolymerized vesicles with similar size profiles. Both polymerized and nonpolymerized vesicles primarily accumulate in liver and spleen. However, the polymerized vesicles display an enhanced biostability as revealed by an elevated level of radioactive lipid marker remaining in the tissues.