DESTRUCTION AND RECONSTITUTION OF POLYPHOSPHOLIPID VESICLES WITH SIZEMEMORY

s(2,4-octadecadienoyl)-sn-glycero-3-phosphocholine (DODPC), constructi ng the bilayer membrane of a vesicle, was polymerized by UV irradiatio n. The freeze-dried vesicles were completely dissolved in chloroform t o obtain cross-linked phospholipid polymer (polyDODPC). The polyDODPC consisted of high molecular weight components and oligomers. The polyD ODPC was dispersed by sonication, and two size distributions of the re constituted vesicles were confirmed, larger vesicles from high molecul ar weight polyDODPC and smaller vesicles from oligomers. When the poly DODPC vesicles of various sizes and unimodal size distribution were re constituted by an extrusion method, the vesicles of the same size as t he vesicles at polymerization showed excellent stability compared with the other sizes. Interestingly, the original size of the polyDODPC ve sicles could be completely restored by a cholate dialysis method. It w as also clarified that vesicles larger than the original size were rec onstituted from the higher molecular weight component, and the smaller vesicles were from the oligomers. Furthermore, a linear phospholipid polymer obtained from -(2,4-octadecadienoyl)-sn-glycero-3-phosphocholi ne could not restore the original size. Those results indicate that th e original size of the vesicles can be restored completely by all poly DODPCs having the original composition of large and small molecular we ights and cross-linked structure.