Abstract
Effect Of Cholesterol On Size Distribution Of Freeze-Thaw Extruded Liposomes
The effect of cholesterol on vesicle size during freezing and thawing process of extruded egg phosphatidylcholine liposomes were studied by varying the length and number of freeze-thaw cycles. Laser diffraction particle size analysis showed that the volume median diameter of freezethawed egg phosphatidylcholine multilamellar vesicles was increased when cholesterol was included in the bilayers. Using a freeze-thaw cycle of 3 min freezing in liquid nitrogen at -196o followed by 3 min thawing at 50° resulted in an anomalously large particle size for egg phosphatidycholine/cholesterol formulations. When egg phosphatidylcholinelcholesterol multilamellar vesicles were repeatedly freeze-thawed, the maximum size was achieved after five freeze-thaw cycles.
