2.2.1. Preparation of Giant Unilamellar Vesicles

Electroformation method is applied to produce giant unilamellar vesicles (GUVs) for measurements of membrane electrical capacitance. The electroformation cell consists of two indium tin oxide (ITO)-coated glass plates, serving as electrodes, which are separated by a PDMS spacer [25]. A small amount (~50 µg) of POPC or SOPC with lipid concentration of 1 g/L in chloroform-methanol solvent (9:1 volume parts) is uniformly spread on the ITO-coated side of each glass plate. After the complete evaporation of the organic solvents achieved under vacuum, the electroformation chamber is filled with 1 mmol/L NaCl aqueous solution, which is sugar-free (control) or contains up to 300 mmol/L of glucose, fructose or sucrose. AC electric field with 10 Hz frequency and peak-to-peak voltage amplitude successively increased to 4 V is applied to the chamber. A high yield of quasispherical unilamellar vesicles with diameters of dozens of micrometers is obtained in several (~3) hours. The conductivities of the aqueous solutions are measured with Cyberscan PC510 (Eutech Instruments, Singapore). Prior to electrodeformation measurements of GUVs, we add 0.1 mmol/L of sodium chloride to the suspension in order to increase the conductivity of the external solution in accordance with the requirements of the GUV electrodeformation method (see Section 2.2.5).
