Treatment of gastric cancer cells with non-thermal atmospheric plasma generated in water
📝 Abstract
Non-thermal atmospheric plasma (NTAP) can be applied to living tissues and cells as a novel technology for cancer therapy. Even though studies report on the successful use of NTAP to directly irradiate cancer cells, this technology can cause cell death only in the upper 3-5 cell layers. We report on a NTAP argon solution generated in DI water for treating human gastric cancer cells (NCl-N87). Our findings showed that the plasma generated in DI water during a 30-minute treatment had the strongest affect in inducing apoptosis in cultured human gastric cancer cells. This result can be attributed to presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) produced in water during treatment. Furthermore, the data showed that elevated levels of RNS may play an even more significant role than ROS in the rate of apoptosis in gastric cancer cells.
💡 Analysis
Non-thermal atmospheric plasma (NTAP) can be applied to living tissues and cells as a novel technology for cancer therapy. Even though studies report on the successful use of NTAP to directly irradiate cancer cells, this technology can cause cell death only in the upper 3-5 cell layers. We report on a NTAP argon solution generated in DI water for treating human gastric cancer cells (NCl-N87). Our findings showed that the plasma generated in DI water during a 30-minute treatment had the strongest affect in inducing apoptosis in cultured human gastric cancer cells. This result can be attributed to presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) produced in water during treatment. Furthermore, the data showed that elevated levels of RNS may play an even more significant role than ROS in the rate of apoptosis in gastric cancer cells.
📄 Content
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Treatment of gastric cancer cells with non-thermal atmospheric plasma generated in water
Zhitong Chena), Li Lin, Xiaoqian Cheng, Eda Gjika, Michael Keidarb) Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
a)Electronic mail: zhitongchen@gwu.edu b)Electronic mail: keidar@gwu.edu
Non-thermal atmospheric plasma (NTAP) can be applied to living tissues and cells as a novel technology for cancer therapy. We report on a NTAP argon solution generated in deionized water (DI) water for treating human gastric cancer cells (NCI-N87). Our findings show that the plasma generated in DI water with 30-minute duration has the strongest effect in inducing apoptosis in pre-cultured human gastric cancer cells. This result can be attributed to presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) produced in water during treatment. Furthermore, the data show that elevated levels of RNS may play more significant role than ROS in the rate of gastric cancer cells death.
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I. INTRODUCTION Gastric cancer is one of the most aggressive types of carcinomas and it is known as the second most common cause of death1,2. Worldwide, the number of newly diagnosed cases is predicted to reach 930,000 per year3. Although gastric cancer is usually managed by chemotherapy or surgery, its 5-year survival rate is approximately 15%4. Therefore, efforts to improve survival rates of patients with gastric cancer are one of the main challenges in current research. Non-thermal atmospheric plasma (NTAP) can be applied to living cells and tissues due to selective cell death without influencing the heathy tissue5-11. The unique properties of NTAP have enabled recent biomedical applications including wood healing12, sterilization13, blood coagulation14, tooth bleaching15, skin regeneration16 and cancer therapy17-20. NTAP is known for the generation of charged particles, electronically excited atoms, (Reactive Oxygen Species) ROS, (Reactive Nitrogen Species) RNS, etc21,22. ROS and RNS, combined or independently, are known to promote cell proliferation as well as cell death. Additionally, extreme amounts of reactive species may lead to the damage of DNA, proteins, lipids, senescence and induce apoptosis23,24. Recent studies showed that indirect NTAP therapy can significantly affect cancer cells25-27. However, there are almost no studies that report on using NTAP to treat gastric cancer cells, let alone NTAP generated in DI water. This paper presents the effects of NTAP generated in DI water on the gastric cancer cells. NTAP device and its characterization are described, as well as the response of cancer cells to the plasma solution therapy. The voltage and current of NTAP generated in DI water were measured with a Tektronix TDS 2024B Oscilloscope. The spectra of NTAP generated in DI water were characterized by UV-visible-NIR Optical Emission Spectroscopy. The plasma density was 3
monitored by Rayleigh Microwave Scattering system (RMS). The temperature of plasma solution was measured with FLIR Systems Thermal Imaging. The concentrations of ROS and RNS in DI water were determined by using a Fluorimetric Hydrogen Peroxide Assay Kit (Sigma-Aldrich, MO), and the Griess Reagent System (Promega, WI), respectively. The cell viability of the human gastric cancer cell line (NCI-N87) was monitored with the Cell Counting Kit 8 assay (Dojindo Molecular Technologies, MD). II. EXPERIMENTAL A. UV-Visible Spectrum Analysis UV-visible-NIR was investigated on plasma discharged in water with wavelength between 200 and 850 nm. The spectrometer and the detection probe were purchased from Stellar Net Inc. In order to measure the radius of the plasma in DI water, a transparent glass plate was used to replace part of the container. The optical probe was placed at a distance of 3.5 cm in front of plasma jet nozzle. Integration time of the collecting data was set to 100 ms. B. Quantification of ROS and RNS Fluorimetric Hydrogen Peroxide Assay Kit (Sigma-Aldrich) was used for measuring the amount of H2O2. A detailed protocol can be found on Sigma-Aldrich website. Briefly, we added 50 μl of standard curves samples, controls, and experimental samples to the 96-well flat-bottom black plates, and then added 50 μl of Master Mix to each well. The plates were incubated for 30 min at room temperature protected from light and measured emission of fluorescence by Synergy H1 Hybrid Multi-Mode Microplate Reader at Ex/Em: 540/590 nm. RNS level was determined by Griess Reagent System (Promega Corporation) according to the instructions provided by the 4
manufacturer. Absorbance was measured at 540 nm by Synergy H1 Hybrid Multi-Mode Microplate Reader. C. Cell lines The human gastric cancer cell line (NCI-N87) was bought from American Type Culture Collection (ATCC). ATCC is the premier global biological materials resource and standard
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