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Rapid Loading of Molecules into Animal Cells using a Radio-Frequency Electric Field.

The introduction of isolated genes or recombinant DNA into cultured cells is a key procedure in cell and molecular biological research. At present there are many methods for gene transfer. All of these methods have certain shortcomings. Most of them are strongly cell-type dependent (i.e., they can work only on certain cells), and the transfer efficiency is frequently unsatisfactorily low. Furthermore, these methods often produce undesirable biological or chemical side-effects. Recently, a new physical method has been developed (1). The cell membrane can be temporarily permeabilized by exposing the cell to a pulse of high intensity electric field (2). This process is attributed to the creation of resealable pores in the cell membrane and is thus called “electroporation.” The electroporation method offers more advantages than most other methods. First, it is simple to use and is time efficient. It can also be used to inject a single cell or millions of cells. Second, because it is a physical method, electroporation is less dependent on cell type. Third, it has fewer harmful biological and chemical side effects. In the last several years, the electroporation method has been successfully used to introduce cloned genes into a wide variety of cells, including mammalian cell lines, isolated cells, plant cells, bacteria, and yeast (3, 4). In addition to gene transfer, electroporation has the potential for use as a micro-injection method to introduce molecules other than DNA, such as second messengers, kinases, and kinase inhibitors, drugs, and antibodies into a large number of cells. We are currently working to improve this technology. Our approach is to experiment with different wave forms and pulse protocols and to test their effects on cell survival rate and transfection efficiency. Our earlier results had suggested that, by