C-5-51

Construction of Giant Vesicle Containing Microspheres
at High Volume Fraction and Its Transformation

12Yuno Natsume 1

Taro Toyota 2

natsumey@fc.jwu.ac.jp

cttoyota@mail.ecc.u-tokyo.ac.jp

Faculty of Science, Japan Women’s University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo
112-8681, Japan
Department of Basic Science, Graduate School of Arts and Sciences, The Universityof Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan

Keywords: Giant Vesicle, Microspheres, Phospholipid, Fluorescence microscopy
Giant vesicles (GVs), which are closed lipid bilayer compartments with cellular size, have muchdrawn attention as a container of cell model. In the cytoplasm, biological macromolecules occupy
a sizeable fraction of the total volume of the media (typically 20–30 vol%), and the effects of this“crowded” state are important for their functions. 1 Crowding significantly influences two
physicochemical features of the macromolecules: (i) thermodynamics stabilization to increases thefree volume of the macromolecules, and (ii) changes in the mobility of the macromolecules. For
the purpose of quantitatively understanding these features, GVs containing microspheres serve as
valuable experimental model systems. 2
Here our purpose is the preparation of GV containing microspheres at a variety of volume
fractions and the clarification of the crowding effect for the GV transformation. Because thewater-in-oil emulsion centrifugation method 4 is fast and easy for encapsulation of soft matterparticles inside of GVs, we utilized it herein to encapsulate 1-m microspheres with volume
fractions in the range of 0–45 vol%. 5 GVs containing polymers or colloidal particles exhibit aunique transformation from an oblate (or prolate) spheroid to linked spheres after external stimuli
such as osmolality change or electrical stimulation. 3,6 These findings are thought to be typicalexamples of the crowding effect for GVs concerning about the thermodynamics of the membranebending energy and the entropic action of encapsulated particles. Here we found that GVs
encapsulating 1-m microspheres with a specific volume fraction transform from sphere topolygonal structure transiently after osmolality change. The fluorescence microscopy observation
on GV membrane proved that this transient state associated with the tubular membrane protrusion
apart from the GV. As far as we know, the polygonal structure of GVs is a characteristic shape only
if GV contains polymerizable proteins such as actin or microtubules. 7 Although the mechanism of
the transient polygonal structure of the GV is still veiled, the current finding can provide us a clue
to clarify the crowding effect for the GV in a non-equilibrium state.
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[3] Natsume, Y., Pravaz, O., Yoshida, H., and Imai, M., Soft Matter, 6: 5359-5366, 2010.
[4] Pautot, S., Frisken, B. J., and Weitz, D.A., Langmuir, 19: 2870-2879, 2003.
[5] Natsume, Y., and Toyota, T., Chemistry Letters, 42: 295-297, 2013.
[6] Terasawa, H., Nishimura, K., Suzuki, H., Matsuura, T., and Yomo, T., Proceedings of theNational Academy of Sciences of the U. S. A., 109: 5942-5947, 2012.
[7] Miyata, H., and Hotani, H., Proceedings of the National Academy of Sciences of the U. S. A.,
89: 11547-11551, 1992.