Immobilization and characterization of giant unilamellar vesicles (GUVs) within porous silica glasses

Immobilization of cells or artificial liposomes has interesting applications in protein biology, membrane biophysics, biomedicine, biosensor technology and new materials development. In this work for the first time we have entrapped giant unilamellar vesicles (GUVs) in silica glasses prepared by the sol-gel process. Results show that GUVs are successfully confined in the porous matrix retaining their structural integrity for at least fifteen days, allowing single-vesicle studies to be performed. Using different fluorescence microscopy approaches, we have studied the effect of the encapsulation on membrane properties, such as their size and shape, hydration degree, domain coexistence and lipid lateral mobility. Results reveal that these properties are altered to a more or less degree after immobilization, but most of vesicles are affected in a similar fashion and no different populations are distinguished. Such effects are attributed to the increase in lateral packing induced by changes in the hydrostatic and/or osmotic pressure occurring during the sol-gel process, as well as to the establishment of interactions between the polar head of the phospholipids and the negatively charged silica surface of the porous matrix.