Preparation of giant vesicles by external AC electric fields. Kinetics and applications

We suggest a method for preparation of large (∼ 15 ÷ 70 μm in diameter), unilamellar, fluctuating, isolated vesicles, allowing us to perform routine measurements of membrane bending elasticity modulus k c by image analysis of thermal fluctuations. The method is based on the effects of AC electric fields on the lipid swelling and liposome formation. We have observed a monotonous decrease of k c for egg phosphatidylcholine (EPC) vesicles from (0.66 ± 0.06) · 10−19 J for 1 day to (0.45 ± 0.05) · 10−19 J for 13 days after vesicle formation. The lipid mixture Chol/PC 37:63 mol/mol led to k c = (1.06 ± 0.15) · 10−19 J, and PE/PC 25:75 mol/mol — to (0.72 ± 0.06) · 10−19 J. — The mechanism of vesicle formation is discussed. It proved that the basic phenomenon is sequences of lateral fusions of smaller vesicles induced by the applied AC electric field.