Cancer cell death by cold atmospheric plasma gets a boost with nitrogen supplements

Cold atmospheric plasma (CAP) is a promising new tool in medicine with potential applications in dentistry, cosmetology, dermatology and, most notably, cancer therapy. New research by Xu et al. finds that adding nitrate and nitrite to a CAP jet used to treat cancer cells can substantially increase cell death without diminishing the jet’s efficiency.

CAP, which is generated at room temperature and pressure, has induced cell death in a multitude of tumor types. Previous studies found CAP generates reactive oxygen and nitrogen species — such as hydroxyl radical, hydrogen peroxide, ozone, nitric oxide, and peroxynitrite anion — which damage DNA and cause cell death. The authors suspected that by adding more nitrogen supplies, they could increase the reactive species created, making a more toxic environment for the cancer cells.

The group exposed myeloma and leukemia cells to a helium plasma jet, following up six hours after the treatment to identify cell death and measure the reactive species. While neither nitrate nor nitrite alone enhanced cell death, when added to the plasma jet prior to treatment they both increased the toxic effect. The additional nitrogen substrates increased the peroxynitrite anion levels, which were ultimately responsible for the cell deaths.

This new method to enhance cell death has the benefit of keeping the plasma jet discharge parameters constant. While increasing jet voltage or frequency can similarly increase cell death, it also results in increased current, which is dangerous in clinical settings. Likewise, increasing oxygen or water vapor in the jet to raise reactive species would only decrease the plasma’s intensity.

Source: “NO₂^- and NO₃^- enhance cold atmospheric plasma induced cancer cell death by generation of ONOO^-,” by Dehui Xu, Qingjie Cui, Yujing Xu, Zhijie Liu, Zeyu Chen, Wenjie Xia, Hao Zhang, Dingxin Liu, Hailan Chen, and Michael G. Kong, AIP Advances (2018). The article can be accessed at https://doi.org/10.1063/1.5046353 .