Formation of reactive chlorine species in Cl− solutions treated by plasma-supplied O atoms and some implications for biological inactivation functions

Abstract

Plasma activated saline solution (PAS) has attracted increased attention in recent years due to wide range of promising applications including sterilization, water treatment, wound healing, and cancer treatment. As we know, reactive oxygen and nitrogen species (RONS) play an important role in plasma applications and its production and action mechanisms have been intensively studied. However, less attention has been paid to the role of reactive chlorine species (RCS). Therefore, researching the mechanism underlying the RCS formation in O-treated saline is necessary to regulate the RCS dose for improving plasma applications. In this work, the concentration of free chlorine (Cl2, HClO, ClO−) are focused to investigate the effect of the addition of Cl− and O2. Results show that the presence of chlorine in solutions, oxygen radicals in plasma jet and the pH of the solution are important factors in the further chemical reactions to RCS. The production of RCS and RONS can be selectively regulated by controlling the three conditions described above. Furthermore, some implications for biological inactivation functions are performed by the A549 lung carcinoma cells to verify the anticancer effects induced by PAS. Schematic of plausible mechanisms of the aqueous chemical processes in solutions are speculated by experimental results. These results provide new insight into the mechanism of chemical activity of PAS, which in turn promotes its more effective biomedical effects.