Previous research in cold atmospheric plasma (CAP) and cancer cell interaction has repeatedly proven that the cold plasma induced cell death. It is postulated that the reactive oxygen species (ROS) and reactive nitrogen species (RNS) play a major role in the CAP cancer therapy. In this paper, we seek to determine a mechanism of CAP therapy on glioblastoma cells (U87) through an understanding of the composition of the plasma, including treatment time, voltage, flow-rate and plasma-gas composition. In order to determine the threshold of plasma treatment on U87, normal human astrocytes (E6/E7) were used as the comparison cell line. Our data showed that the 30 sec plasma treatment caused 3-fold cell death in the U87 cells compared to the E6/E7 cells. All the other compositions of cold plasma were performed based on this result: plasma treatment time was maintained at 30 s per well while other plasma characteristics such as voltage, flow rate of source gas, and composition of source gas were changed one at a time to vary the intensity of the reactive species composition in the plasma jet, which may finally have various effect on cells reflected by cell viability. We defined a term “plasma dosage” to summarize the relationship of all the characteristics and cell viability.

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Gold nanoparticles (AuNPs) have been investigated as a promising reagent for cancer therapy in various fields. In the meantime, cold atmospheric plasma has shown exquisite selectivity towards cancer cells. In this paper, we demonstrate that there is a synergy between gold nanoparticles and cold atmospheric plasma in cancer therapy. Specifically, the concentration of AuNPs plays an important role on plasma therapy. At an optimal concentration, gold nanoparticles can significantly induce glioblastoma (U87) cell death up to a 30% overall increase compared to the control group with the same plasma dosage but no AuNPs applied. The reactive oxygen species (ROS) intensity of the corresponding conditions has a reversed trend compared to cell viability. This matches with the theory that intracellular ROS accumulation results in oxidative stress, which further changes the intracellular pathways, causing damage to the proteins, lipids and DNA. Our results show that this synergy has great potential in improving the efficiency of cancer therapy and reducing harm to normal cells.

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