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Effects of aged PAM on cancer cells

The study of the effects of low temperature plasma (LTP) on cancer cells, in vitro and in vivo, is today one of the most active research areas of plasma medicine. Here, we study the interaction of LTP with cancer cells which were grown overnight and then seeded into MEM (minimal essential medium) growth culture treated by the plasma pencil at different exposure times. Plasma activated media (PAM) proved to be very effective in killing cancer cells. In our study we used “aged” PAM for different lengths of time to determine how long the treated media can be stored and still maintain its potency against cancerous cells. We found that fresh PAM (not aged) is most potent, but PAM produced by 4 minutes exposure to LTP and aged for up to 8 hours was still able to induce cell killing. Cell viability was determined immediately after treatment and at various times (hours/days) post plasma exposure, by Trypan Blue exclusion assay. The pH of the medium was monitored by a pH meter at various exposure times. Our measurements showed that buffered PAM maintained a stable pH value and therefore acidification of the media was not an issue. We hypothesize that it was the long lived solvated oxygen reactive species and nitrogen reactive species and their reaction by-products in the media that are responsible for the observed effects.