For the study of permeation enhancers, CF-containing liposomes were prepared and purified as described above. For permeation enhancement by ethanol, 60 μl of purified liposomes with encapsulated CF was mixed with 1140 μl of PBS in a measuring cuvette. The samples were maintained at 30 °C. At approximately 5-minutes intervals, 40 μl of ethanol was added to the measuring cuvette from the top and the fluorescence intensity was measured by fluorescence spectrophotometry as described above. For permeation enhancement by oleic acid, the procedure was very similar to ethanol, only the volumes were different (50 μl oleic acid, 1090 μl PBS) and only one addition at the start of the experiment was done. The temperature was also 30 °C.