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Low-Temperature Plasma Needle for Biomedical TreatmentsMichael A. Wilson,1 Timothy R. Brubaker,2 Andrea M. Mastro,3 Michael M. Micci,4 Sven G. Biln,5 and Sean D. Knecht61Department of Electrical Engineering; 2Department of Electrical Engineering; 3Department of Biochemistry and Molecular Biology; 4Department of Aerospace Engineering; 5Department of Electrical Engineering; 6Applied Research LaboratoryConclusions and Further InvestigationAbstract

ResultsExperimental DesignThe hypothesis is that the reactive oxygen species generated in the plasma plume are responsible for the destructive effects due to increased oxidative stress on the cells. The generation of reactive oxygen species in the plasma plume and the subsequent oxidative stress on the cells is the proposed method of action. Further experimentation is planned to quantify the concentration of reactive chemical species and evaluate this hypothesis. We will determine why pure helium exposure results in cell destruction. Different gases will be used in future experiments as well as longer exposure times. Larger diameter wells and a greater volume of PBS will also be used. An overview of the design methodology of a low-temperature plasma needle and preliminary results investigating its efficacy in treating metastatic human breast cancer epithelial cells is reported. Low-temperature plasma is created by flowing gas past a high-voltage surface. This process produces ions and generates an electrically conductive state of matter (plasma) at room temperature. High-energy collisions of electrons with neutral particles create reactive chemical species such as NO, O3, H2O2 and others which have biomedical applications.

Current cancer treatment options, such as surgery and chemotherapy, may not be sufficient to treat metastatic cancer. Initial experiments have been conducted in which a line of cultured metastatic human breast cancer epithelial cells (MDA-MB-231) are exposed to the low-temperature plasma needle. The plasma needle is lowered into cell culture dishes and the cells are exposed to plasma at different dosages. Cell detachment was observed for plasma and helium-exposed cultures with a greater effect observed for plasma-exposed cultures. This is attributed to reactive chemical species generation in the plasma plume. Experiments are continuing to optimize the treatment conditions and further this research.

Images of metastatic breast cancer culture MDA-MB-231 post treatment. Images are equivalent in scale. Each culture was exposed to 3-minute dosages. (a) Helium-exposed culture, (b) Plasma-exposed culture, (c) Helium-exposed culture, (d) Plasma-exposed culture. The voids in cell culture are larger for plasma-exposed culture.AcknowledgmentsThe authors wish to thank D. Sosnoski, for helping prepare the cell cultures. The BC line (MDA-MB-231, ATCC-HTB 26 presumptive equivalent) was initially provided by Dr. D. Welch, University of Alabama at Birmingham. Contacts:Michael A. WilsonTimothy R. BrubakerAndrea M. Mastro Michael M. MicciSven G. BilnSean D. Knechtmaw5595@psu.edutrb5084@psu.edua36@psu.edux0c@engr.psu.edusbilen@psu.edusdk149@psu.edu

This image shows the full LTP setup. Helium is introduced to the system using a mass flow meter. The voltage and ground inputs are connected from the power supply and threaded through the tube to their respective input locations. The interface between the LTP syringe interacting with a saline sample.

Syringe withinPEEKPlasma DischargeGround wire wrapped around syringeThe 22-gauge needle is 2 long and serves as the high voltage electrode.The grounding electrode is placed approximately 1/8 from the tip of the syringe.The syringe is sheathed with PEEK (polyether ether ketone).PEEK has a high dielectric strength used as a barrier to prevent arc production.The diameter of the device with the PEEK is equivalent to a 16-gauge needle.Helium flows axially through the syringe.Gas is controlled by the mass flow controller calibrated at 70F, and 14.7psia. The flow rate can be controlled over the range of 16775 mL/min.An Agilent 33220A Function Generator generates a 5-kHz, 2-Vpp sine wave.This wave is amplified 1000 to 2 kV by a Trek 10-40 amplifier. Increasing the voltage or mass flow rate increases the length and visible intensity of the plasma plume.

Schematic of the LTP syringe. The HV power supply is connected to the syringe which is encased within the dielectric barrier (PEEK). The gas flows through the back and out of the tip of the syringe as plasma. (a)(b)(c)(d)