Generation of Giant Unilamellar Liposomes Containing
Biomacromolecules at Physiological Intracellular Concentrations using
Hypertonic Conditions
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Abstract
Artificial cells, particularly cell-sized
liposomes, serve as tools
to improve our understanding of the physiological conditions of living
cells. However, such artificial cells typically contain a more dilute
solution of biomacromolecules than that found in living cells (300
mg mL<sup>β1</sup>). Here, we reconstituted the intracellular
biomacromolecular conditions in liposomes using hyperosmotic pressure.
Liposomes encapsulating 80 mg mL<sup>β1</sup> of macromolecules
of BSA or a protein mixture extracted from <i>Escherichia coli</i> were immersed in hypertonic
sucrose. The concentration of macromolecules in BSA-containing liposomes
was increased in proportion to the initial osmotic pressure ratio
between internal and external media. On the other hand, the concentration
of the protein mixture in liposomes could be saturated to reach the
physiological concentration of macromolecules in cells. Furthermore,
membrane transformation after the hypertonic treatment differed between
BSA- and protein mixture-containing liposomes. These results strongly
suggested that the crowded environment in cells is different from
that found in typical single-component systems