Electrotransfection with Intracellular Buffer

Introduction of foreign molecules, such as DNA, RNA, or proteins, into living cells is a powerful means to test the biological functions of these molecules. One of the techniques by which foreign molecules can be introduced into living cells is electroporation (for reviews, see refs. 1 ,2 ). Compared to other techniques for the introduction of molecules into living cells, electroporation does not seem to cause prolonged alterations in the biological structure and function of the target cells. Nevertheless, the pores that are induced by the electroporation technique (3 –5 ) can be visualized by rapid-freezing electron microscopy techniques (6 ) and allow a direct contact between the cytoplasm of the cells and the electroporation medium. The components of the electroporation medium can, therefore, penetrate into the cell interior as long as the pores exist (7 ). In this perspective, it is obvious that cells are exquisitely sensitive to the composition of the electroporation medium (8 –10 ) and that an electroporation medium that resembles the composition of the cytoplasm would probably enhance the viability of the cells after electroporation.