Plasma disinfection via the reduced-pH method using an ex vivo porcine contaminated skin model

Abstract

Abstract Plasma disinfection has been developed as a medical application using low temperature atmospheric pressure plasma. We identified an enhancement effect of the bactericidal activity of plasma treatment against a bacterial suspension by the acidification of the solution (the reduced-pH method). The key efficacy factor of the reduced-pH method was shown to be hydroperoxy radicals (HOO•). However, in the case of medical application, the efficacy of plasma disinfection on living body should be evaluated, because it have complicated surface structure and rich organic matter which can inhibit disinfection. Here, we demonstrated the efficacy of the reduced-pH method on the skin surface by using a porcine skin model. The bactericidal activity of plasma treatment at pH 3.7 and 6.6 was 3.7 and 0.8 log reduction, respectively. The enhancement effect of bactericidal activity was confirmed to be 4.6 on the skin at the tested pH conditions. The method for providing pH control on the skin surface was very simple, involving spreading of the pH buffer solution on the skin. The reduced-pH method may therefore serve as an essential technique for plasma disinfection on the human body, as one of the most important concerns for such treatment is to ensure low levels of thermal damage by the plasma jet. The reduced-pH method thus enables enhancement of the bactericidal activity of plasma treatment without increasing the plasma power.