Microbicidal Activity of Artificially Generated Hydroxyl Radicals

The hydroxyl radical, one of the reactive oxygen species, has one unpaired electron in the structure, so that it tends to deprive other substances of an electron which is so-called oxidation. It is known that hydroxyl radicals produced by immunological response kill invading microorganisms by the oxidation. Besides the immune system, it has been demonstrated that hydroxyl radicals play an important role in the bactericidal action of antibiotics. In this context, we have conducted a research to develop disinfection techniques utilizing artificially generated hydroxyl radicals. We adopted photolysis of H2O2, sonolysis of water and the other photo-chemical reaction as generators of hydroxyl radicals. A series of studies demonstrated that the microbicidal activity of hydroxyl radicals was sufficient to kill bacteria in an experimental biofilm as well as planktonic bacteria and fungi within a short-treatment time. In addition, the safety aspect is confirmed by an in vivo study and a literature review. Thus, it is suggested that disinfection treatment utilizing artificially generated hydroxyl radicals can be applicable to medical/dental therapy as novel disinfection treatments.