Abstract
AbstractA large gap pin‐to‐plate, atmospheric‐pressure plasma reactor is demonstrated as means of in vitro study of plasma species interactions with cell cultures. By employing optical emission and optical absorption spectroscopy, we report that the pin‐to‐pate plasma array had an optimal discharge frequency for cell death of 1000 Hz in ambient air for the target cancer cell line, human glioblastoma multiform (U‐251MG). The detected plasma chemistry contained reactive oxygen and nitrogen species including OH, N2, N2+ and O3. We show that by varying the plasma discharge frequency, the plasma chemistry can be tailored to contain up to 8.85 times higher levels of reactive oxygen species (ROS) as well as a factor increase of up to 2.86 for levels of reactive nitrogen species (RNS). At higher frequencies, ROS are more dominant than RNS, which allows for a more dynamic and controlled environment for sample study without modifying the inducer gas conditions. When used for treatment of culture media and cell cultures, variation of the plasma discharge frequency over the range 1000–2500 Hz demonstrated a clear dependence of the responses, with the highest cytotoxic responses observed for 1000 Hz. We propose that the reactor offers a means of studying plasma–cell interactions and possible cofactors such as pro‐drugs and nanoparticles for a large volume of samples and conditions due to the use of well plates.
Highlights
Studies of non-thermal plasma (NTP) have shown that they can be utilised for a wide range of applications, including; food preservation, wound sterilisation, enhanced crop growth, pollution abatement, volatile organic compound (VOC) removal, polymer functionalisation, and water purification.[1,2,3,4,5] Such a broad variability of applications is due to the large range of gas chemistries that can be generated using NTP systems
The effects observed can be explained by the interaction of the electric field and the impact it has on electron excitation and, plasma ignition
The optical diagnostics of the large gap atmospheric plasma discharge demonstrated that the discharge frequency plays a vital role in the formation of reactive species
Summary
Studies of non-thermal plasma (NTP) have shown that they can be utilised for a wide range of applications, including; food preservation, wound sterilisation, enhanced crop growth, pollution abatement, volatile organic compound (VOC) removal, polymer functionalisation, and water purification.[1,2,3,4,5] Such a broad variability of applications is due to the large range of gas chemistries that can be generated using NTP systems. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) can be generated to interact with target samples. Examples of ROS include O, O2*, O3, OH, and NO, examples of RNS being N, N2*, N2+, and NxOy. Examples of ROS include O, O2*, O3, OH, and NO, examples of RNS being N, N2*, N2+, and NxOy These reactive species can interact with synthetic and/or biological samples and, when the plasma conditions are appropriately tailored, can cause alterations within cells that can lead to cancer cell death.[6] The plasma chemistry can be altered by introducing different gases into the system environment at varying percentages and ratios. Adding a small percentage of CO2 into a system that is running predominantly on ambient air can lead to higher levels of O3 formation, which can be further optimised with the introduction of other secondary gases such as Ar.[7,8,9] Introducing inert gases such as Ar and He gives rise to the production of inert excited species that can bombard and interact with sample surfaces and give rise to more binding sites or can aid in the formation of other reactive species, such as OH and N2*, through synergistic energy transfers.[10]
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