EFFECT OF GRAFTED PEG-2000 ON THE SIZE AND PERMEABILITY OF VESICLES

The permeability of PEG-derivatized vesicles produced by the extrusion technique (VETs) to encapsulated D-glucose has been studied. Vesicles were prepared from mixtures of dipalmitoylphosphatidylcholine (DPPC), phosphatidylinositol (PI) and dipalmitoylphosphatidylethanolamine wit h covalently attached poly(ethylene glycol) of molecular weight 2000 ( DPPE-PEG2000). The occurrence of an irreversible temperature-induced s ize transition of the PEG-derivatized VETs was detected close to the t emperature of the main phase transition of the predominant phospholipi d component by photon correlation spectroscopy. The permeability of th e vesicles towards radioactive D-glucose was studied by a method simil ar to the one proposed by Johnson and Bangham at 25, 37 and 50 degrees C for VETs with DPPE-PEG content from 0 to 9 mol%. A complex effect o f the PEG-coverage was found with a maximum leakage in the range of th e transition of the polymer from the mushroom to the brush conformatio n.