Hydrogen Peroxide and Beyond-the Potential of High-voltage Plasma-activated Liquids Against Cancerous Cells

Background:
The use of plasma-activated liquids such as PBS, medium or simply plasma-activated
water (PAW) has been receiving increasing attention for applications in cancer treatments. Amongst the reactive
species contained in these solutions, hydrogen peroxide appears to play a pivotal role in causing cytotoxic effects.
H2O2 concentrations can be correlated with reduced cell viability and growth and used as an indicator of
the potential efficacy of a plasma-activated liquid.


Objective:
To investigate the cytotoxic mediators generated in water specific to high-voltage DBD-ACP.


Method:
Using a high-voltage dielectric barrier atmospheric cold plasma (DBD-ACP) system, we examined
PAW-mediated cytotoxic effects on different mammalian cell lines employing a set-up where short-lived reactive
species can be discounted and activated liquids with long-term stability are generated.


Results:
The PAW potency could be modulated using voltage level, treatment time and post-treatment storage
time and target-related characteristics such as surface to volume ratio. All of these parameters effected cell viability
in a hydrogen peroxide concentration correlated manner. The susceptibility of two cancer cell lines to
PAW was similar to that observed for two non-cancer cell lines and the toxicity of plasma-activated water exceeded
that of the corresponding hydrogen peroxide concentrations.


Conclusion:
In cytotoxic plasma activated water an essential role for H2O2 has been demonstrated multi-fold,
yet further contributing factors are apparent and remain to be identified.