Synthesis of Liposome Reinforced with Cholesterol and Application to Transmission Electron Microscopy Observation

Liposome was synthesized by using mixture of dipalmitoylphosphatidylcholine and cholesterol in the ultrapure water or physiological saline. Phase transformation temperature and vibrational mode of dipalmitoylphosphatidylcholine molecule were detected by using transmission Fourier-transform infrared spectroscopy for aqueous solution, which we developed. The liposomes were fixed on an amorphous carbon mesh for ultra-high resolution transmission electron microscopy observation and stained with platinum thymidine blue. As-prepared liposomes reinforced with cholesterol were spherical in shape with size larger than 100 nm in diameter and still stable in the vacuum. Under the strong electron irradiation condition, the solution enclosed in the liposomes became unstable and then collapsed. On the other hand, the liposome synthesized in the physiological saline sometimes contains crystallized salt. As a result, the liposome shows proper strength to hold wet material in itself in a vacuum and can be used for the transmission electron microscopy observation.