Lipid swelling and liposome formation on solid surfaces in external electric fields

Abstract

External electric fields can induce or prevent lipid swelling and liposome formation on solid surfaces. These effects depend on the type of the lipid and the surface, the medium parameters (temperature, osmolarity, ionic strength), the dried lipid layer thickness, the type and parameters of the electric field (direct current (DC) or alternating current (AC), amplitude, frequency, current), the place of the lipid (on the electrode surface itself or on another surface) and the time of exposure. This paper reviews experimental results and theoretical estimates for these effects and presents new data and estimates for the effects of lipid charge and frequency of the field. The basic conclusion is that the electric fields can affect lipid swelling and liposome formation by at least four mechnisms: (1) direct electrostatic interaction, (2) redistribution of the double layer counter-ions, (3) membrane surface and line tension changes and (4) electroosmotic effects.