Proteins are carriers of biological functions and the effects of atmospheric-pressurenon-thermal plasmas on proteins are important to applications such as sterilizationand plasma-induced apoptosis of cancer cells. Herein, we report our detailedinvestigation of the effects of helium-oxygen non-thermal dielectric barrierdischarge (DBD) plasmas on the inactivation of lactate dehydrogenase (LDH) enzymesolutions. Circular dichroism (CD) and dynamic light scattering (DLS) indicate thatthe loss of activity stems from plasma-induced modification of the secondarymolecular structure as well as polymerization of the peptide chains. Raising thetreatment intensity leads to a reduced alpha-helix content, increase in thepercentage of the beta-sheet regions and random sequence, as well as graduallydecreasing LDH activity. However, the structure of the LDH plasma-treated for 300seconds exhibits a recovery trend after storage for 24 h and itsactivity also increases slightly. By comparing direct and indirect plasmatreatments, plasma-induced LDH inactivation can be attributed to reactive species(RS) in the plasma, especially ones with a long lifetime including hydrogenperoxide, ozone and nitrate ion which play the major role in the alteration of themacromolecular structure and molecular diameter in lieu of heat, UV radiation, andcharged particles.

Cold atmospheric plasma (CAP) has been widely used in biomedicine during the last two decades. While direct plasma treatment has been reported to promote wound healing, its application can be uneven and inconvenient. In this study, we first activated water with a portable dielectric barrier discharge plasma device and evaluated the inactivation effect of plasma-activated water (PAW) on several kinds of bacteria that commonly infect wounds. The results show that PAW can effectively inactivate these bacteria. Then, we activated tap water and examined the efficacy of PAW on wound healing in a mouse model of full-thickness skin wounds. We found that wound healing in mice treated with PAW was significantly faster compared with the control group. Histological analysis of the skin tissue of mice wounds showed a significant reduction in the number of inflammatory cells in the PAW treatment group. To identify the possible mechanism by which PAW promotes wound healing, we analyzed changes in the profiles of wound bacteria after PAW treatment. The results show that PAW can significantly reduce the abundance of wound bacteria in the treatment group. The results of biochemical blood tests and histological analysis of major internal organs in the mice show that PAW had no obvious side effects. Taken together, these results indicate that PAW may be a new and effective method for promoting wound healing without side effects.