Bacteria sterilization application by using plasma activated physiological saline

Abstract

The plasma activated water has great application prospects in the fields of environmental protection, biomedicine, food safety, et al., due to its unique chemical activity. In this work, the plasma activated physiological saline is successfully generated by using hollow fiber-based cold microplasma jet array running in physiological saline solution. This design can lead to an obvious increase in the contact area between microplasmas and treated physiological saline solution, thus improving the chemical reaction efficiency of short-lived species. The influences of working gases such as He, N2, O2 and air on the sterilization efficiency of E. Coli by using this plasma activated physiological saline are investigated as a function of discharge time. As the discharge time increases from 10 to 180 s, the sterilization efficiency of the plasma activated physiological saline significantly increases. It is found that the bactericidal efficiency of the air discharge activated physiological saline is highest. For a discharge time of 120 s, the sterilization efficiency of E. Coli in this plasma activated physiological saline can reach as high as 99.999%. The pH value of this air discharge activated physiological saline is achieved by using acidity meter and as the discharge time increases from 10 to 60 s, the pH value decreases from 7.3 to 3.1 and the physiological solution becomes acidic. This may be due to the NOX produced in the plasma reacting with water and producing nitric and nitrate acids. The reactive oxygen species generated in the plasma activated physiological saline are supposed to be O3 and H2O2. The concentrations of O3 and H2O2 are identified by using UV-visible absorption spectra and chemical deposition methods. The strong absorption peak of O3 in UV-visible absorption spectrum is at a wavelength of 253.7 nm. The concentration of O3 is calculated by using Beer-Lambert Law. As the discharge time increases, the concentration of O3 in the plasma activated physiological saline obviously increases. For a discharge time of 60 s, the concentration of O3 is 43.1210-3 mol/L and nearly saturated. The concentration of H2O2 is obtained by the total amount of reactive oxygen species, which is calculated by using the chemical deposition method, deducting the O3 content. As the discharge time increases from 10 to 180 s, the concentration of H2O2 increases from 1.510-3 to 4.710-3 mol/L. The analyses of experimental data from various methods indicate that air discharge activated physiological saline containing a variety of long-lived reactive oxygen species, such as H2O2 and O3, is very effective in killing E. Coli cells in the acidic saline solution. The air discharge activated physiological saline can provide a means to store the advanced oxidation species induced by the discharge for sterilization applications.