ELECTROINJECTION

Electric field-mediated injection (electroinjection) of substances into living cells is superior to osmotically mediated incorporation in a variety of ways. It is not restricted to a few cell types because the phenomenon of reversible breakdown can be universally applied to all living cell membranes. Electro-injection can be readily controlled and the process can be observed microscopically. in addition, the precise control afforded by widely available electroinjection devices provides a high degree of reproducibility. However, controversy remains with respect to the reversibility of electrically mediated cell membrane breakdown. as is the case for electrofusion, controlled membrane breakdown is the fundamental step in the incorporation of normally membrane-impermeable substances into living cells. Reversibility of the membrane breakdown requires that membrane and the cytosol perturbations caused by the application of electrical field pulses be sufficiently small to permit resealing without irreversibly damaging the cell. Postbreakdown resealing of the membrane occurs principally by the tendency of the lipid bilayer to regain its integrity, a rapid process. © 1993