Patent Application
20150157856
This invention relates to apparatuses for transporting materials through cell walls, and specifically to apparatuses that do not use metallic electrodes to accomplish the above.
The phenomenon of electroporation of cell walls is well known. Since the 1980s, many efforts have been made to increase the transfection efficiency of poration while reducing cell death.
It has been found that there is a lower pulse energy threshold below which electroporation does not occur, and an upper threshold above which cell wall permeability becomes irreversible, resulting in cell death. There is an even higher energy threshold above which the porated cells are destroyed by overheating.
The lower threshold for an effective transmembrane potential is thought to be ca. 1.0 V, as reported by Walters et al. in U.S. Pat. No. 6,010,613 and by Weaver, in “Emerging Electromagnetic Medicine”, O'Connor et al., Editors. Other investigators report thresholds that are higher by at least an order of magnitude. The inconsistent numbers can be explained by examining the methods that have been used to arrive at the reported results. The electric field strength is usually calculated from the equation E=V/d, where V is the voltage imposed on the electrodes, and d is the distance between them. For this equation to yield accurate results for the majority of the cells between the electodes, the voltage drop between the electrodes must be uniform. That presupposes that the inter-electrode impedance is uniform. In practice, polarization at the tissue-to-electrode interfaces makes the impedance non-uniform. The impedance is highest near the electrodes, where the greatest voltage drop occurs. Mid-way between the electrodes, the voltage across the cells is much lower. Thus, when the voltage is adjusted to an appropriate level between the electrodes, it is high enough to destroy the cells near the electrodes. Conversely, when the voltage is adjusted to be appropriate near the electrode, it is below the poration threshold between the electrodes. The use of electrode voltage as a guiding parameter for developing electroporation protocols is therefore not ideal.
Westersten et al. in U.S. Pat. No. 7,664,545 disclose an apparatus that uses current, rather than the inter-electrode voltage as a basis for developing porating protocols. An increase in poration efficiency of ca. 400% was observed, compared to the conventional methods. The current pulses were delivered from a constant-current source, which made the current intensity independent of the inter-electrode impedance. Nevertheless, histological examination of the porated tissue revealed, that further improvements of the poration apparatus is desirable.
An improved poration apparatus with a high degree of poration efficiency and minimal cell damage is needed for gene therapy, for delivering chemotherapeutic agents to localized areas, for genetic engineering involving both animal and plant species and for general genetic research. It is the object of this invention to provide such an apparatus.
It is an object of the present invention to provide an apparatus for electroporation that yields maximal poration efficiency while minimizing cell damage.
It is another object of the invention to provide poration electrodes that are non-invasive.
It is yet another objective of the invention to provide an apparatus that optimizes the poration parameters by measuring the change in inter-electrode impedance which occurs when the poration threshold has been exceeded.
It is a further objective of the invention to eliminate metallic electrodes which cause electrolysis, resulting in cell death.
The salient feature that distinguishes the present invention from prior art is that the ionic flux required to cause poration is generated in a circuit that does not include metallic electrodes. A non-metallic conduit containing an ionic fluid, an NaCl solution, e.g., forms the secondary winding of a transformer and the ions are accelerated to the requisite flux by adjusting the voltage imposed on the metallic primary winding of the transformer.
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The above description of the preferred embodiment is not to be construed as a limitation as to the manner in which the invention may be implemented. Likewise, the application of the invention should not be limited to any one field.
The electrode system without metallic electrodes may be useful in other applications such stimulation of tissues, heart defibrillation and passive exercise equipment. I claim:
