ID: 2179

  • Title:
    An Electrotransfer instrument that uses impedance feedback at elevated temperatures to improve the delivery process in vivo

    Jaroszeski, Mark J. - Department of Medical Engineering and Center for Molecular Delivery,  University of South Florida,   Corresponding Author
    Otten, Alex - Department of Electrical Engineering and Center for Molecular Delivery, University of South Florida
    Hoff, Andrew -  Department of Electrical Engineering and Center for Molecular Delivery, University of South Florida
    Heller, Richard - Department of Medical Engineering and Center for Molecular Delivery,  University of South Florida

    Background and Objectives of the Study: Pulsed electric fields have broad potential for molecular delivery applications relative to gene therapy, protein therapies, vaccination, and chemotherapy. With respect to gene delivery, the potential has not yet been fully realized even though there is a significant growing body of literature that demonstrates feasibility. One reason is that expression levels are not generally as high as needed, and reproducibility is often an issue. These problems persist in spite of the countless studies that have examined different electrode configurations as well as results from wide ranges of electrical parameters such as pulse width, voltage, number of pulses, and period. This has hindered translation into the clinic. Recently, localized moderate heating (to ~43C) during the delivery of plasmid DNA using pulses electric fields has been shown to increase expression of a delivered foreign gene. Furthermore, tissue impedance measured during electrical treatment has been used in a feedback manner to adjust electrical treatment in real-time to customize the electroporation process during delivery. This resulted in increased expression too. This study focused combining the use of these two parameters to improve further improve the process.

    Methods Used: A custom device that could be used to locally heat the target tissue, apply electric pulses, and use impedance feedback to guide pulsation did not exist. Therefore, one was designed, constructed, and tested. The developed system included an electrode array that contained up to 16 individually addressable electrodes, a heat source, and a thermal camera to monitor tissue temperature. The camera and heat source were integrated into a handle that contained the electrodes. Infrared, microwaves, and warm air were investigated as mechanisms to heat tissue. Warm air proved to be as efficient as the other two methods with respect to heating times and was much simpler to implement and integrate into a handle that contained electrodes. Images from the camera were used in a control algorithm to heat tissue safely and to maintain temperature during treatment. A similar control algorithm was used to acquire impedance measurements from the tissue before pulsation and periodically between pulse application an impedance analysis chip (AD5933, Analog Devices). Electric pulses were created by electronically switching the output of a commercial power supply (Magna-Power, Flemington, NJ, USA) A laptop was used to automate the entire process.

    Results Obtained: The final computer-controlled device was able to heat tissue 5 mm below the skin surface to 43C in under a minute; this temperature was found to be optimal in preliminary studies. The impedance measurement part of the system produced accurate results in the 200 Ohm to 100 kOhm range using resistors and could detect changes in impedance due to electropulsation in tissues. DNA delivery experiments conducted in Guinea pig skin showed increase delivery when compared to animals that were treated with heat and electroporation, or electroporation alone. Similar results were obtained when DNA encoding IL-12 was delivered to murine B16 tumors in the flanks of mice in that heat and impedance combined with electroporation resulted in increased survival and tumor regression.

    Conclusions: Impedance-guided elecropulsation of tissues at elevated temperatures has a positive effect on gene electrotransfer based upon the data obtained thus far. These results were used to inform the design of a commercial instrument for the delivery of chemotherapeutics for the veterinary market. The device is currently being tested by several oncology practices in the USA. Preliminary data indicates success.

    gene electrotransfer, electroporation, impedance, tissue heating


    Topic 1:
    5. Exposure devices and methods

    Topic 2:
    8. Cell and tissue stimulation, wound healing

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