Effect of vesicle size on the photoinduced destabilization of two-component vesicles of dioleoylphosphatidylethanolamine and polymerizable 1,2-bis(10-(sorbyloxy)decanoyl);-sn-glycero-3-phosphatidylcholine.

The polymerization of two-component vesicles consisting of the nonpolymerizable lipid dioleolylphosphatidylethanolamine (DOPE) and polymerizable 1,2-bis(10-(sorbyloxy)decanoyl) -sn-glycero-3-phosphatidylcholine (SorbPC) resulted in phase separation of the lipids into polymeric and monomeric domains. Since the nonpolymerizable phosphatidylethanolamine can assume a nonlamellar phase, the polymerization induced phase separation led to vesicle destabilization with concomitant release of aqueous contents. Oligolamellar vesicles of SorbPC/DOPE (1:3) having an average diameter of 275 +/$-$ 65 nm showed 25-30% leakage of the fluorophore calcein while unilamellar vesicles of the same lipid concentration and an average diameter of 125 +/$-$ 15 nm did not show leakage of dye during photopolymerization. The photoinduced destabilization required three processes: (a) lateral phase separation of the membrane's components driven by the photopolymerization; (b) the ability of the nonpolymerizable lipid to assume a nonlamellar phase as enriched domains are formed; and (c) bilayer contact between lamellae. These results are discussed in terms of a model for membrane destabilization that requires intralamellar interaction