Electrical Field-Induced Membrane Fusion

In the following, a physical fusion method is described based on the electrical breakdown of membranes. No attempt is made to explain this procedure in full detail (for an extensive review see 61)), but rather a qualitative picture is given in order to provide a general understanding of the process. 

Essentially, this method is based on subjecting cell membranes to a short external electric field pulse of an intensity comparable to the electric field strength of the membrane 77). Under these conditions the membrane breaks down locally and becomes permeable. This process is reversible, i.e. the membrane reconstitutes its original properties in time intervals which can be experimentally controlled. 

How can cells be brought into the proper aligment required for electrically induced fusion When cells are placed in an inhomogeneous electric field, as demonstrated in Fig. 49, they start to migrate in the direction of larger field strength. This is caused 

Electric field-induced fusion has been applied to a vast variety of cells including human erythrocytes and liposomes made from asolectin and egg phosphatidylcholine. To what extent this method can be utilized for fusing polymerizable vesicles will be demonstrated in the following. 

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The electrofusion technique is a significant new tool for research and production of controlled systems in the life sciences. The study of electric-field-induced membrane and cell phenomena on a molecular level will contribute to fundamental understanding both of cell-to-cell fusion and of membrane structure and function. 

U. Zimmermatm and J. Vienken, Electric Field-Induced Cell-To-Cell Fusion, Journal of Membrane Biology, vol. 67, no. 3, pp. 165-182, 1982. 

If two cells adhere to each other during the field pulse, electrical breakdown occurs in the contact zone between the two cells. If the membrane contact is close enough (1-2 nm), lipid molecules are able to diffuse from one membrane into the other forming bridges between both membranes. After turning off the field pulse, the fusion of the two cells into one sphere is energetically favoured. Thus, close contact of membranes has to be achieved before fusion can be induced by an electrical field pulse. 

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