Influence of encapsulated enzyme on the surface properties of freeze-dried liposomes in trehalose

The interfacial properties of liposomes in which a soluble protease from Mucor meihie was encapsulated and subjected to freeze-drying procedure in the presence of trehalose, have been studied. Enzyme encapsulation in liposomes subjected to freeze-drying produces changes in the membrane interfacial properties as a consequence of penetration of some of the protein hydrophobic portion into the lipid bilayer. This membrane perturbation can be explained when considering that the presence of trehalose during the freeze-drying process brings about membrane hydrophobic defects where the protein can be accommodated without inducing any additional disorder. These interfacial changes in the membrane were detected by a decreased partition of Merocyanine 540, loss in the lytic effect of lysoderivatives and an increase in ANS binding sites in comparison to freeze-dried liposomes in the absence of protease. This information can be useful to modify the enzyme release of liposomes in a controlled way as a function of the interacting molecules present in the outside environment. (C) 2000 Elsevier Science B.V. All rights reserved.