Hypochlorous acid produced at the counter electrode inhibits catalase and increases bactericidal activity of a hydrogen peroxide generating electrochemical bandage.

ABSTRACT

Previously, an electrochemical bandage (e-bandage) that uses a three-electrode system to produce hydrogen peroxide (H2O2) electrochemically on its working electrode was developed as a potential strategy for treating biofilms; it showed activity in reducing biofilms in an agar biofilm model. Xanthan gum-based hydrogel, including NaCl, was used as the electrolyte. While H2O2 generated at the working electrode in the vicinity of a biofilm is a main mechanism of activity, the role of the counter electrode was not explored. The goal of this research was to characterize electrochemical reactions occurring on the counter electrode of the e-bandage. Counter electrode potential varied between 1.2 and 1.5 VAg/AgCl; ∼125 µM hypochlorous acid (HOCl) was generated within 24 h in the e-bandage system. When HOCl was not produced on the counter electrode (achieved by removing NaCl from the hydrogel), reduction of Acinetobacter baumannii BAA-1605 biofilm was 1.08 ± 0.38 log10 CFU/cm2 after 24 h treatment, whereas when HOCl was produced, reduction was 3.87 ± 1.44 log10 CFU/cm2. HOCl inhibited catalase activity, abrogating H2O2 decomposition. In addition to H2O2 generation, the previously described H2O2-generating e-bandage generates HOCl on the counter electrode, enhancing its biocidal activity.