An Integrated HOCl-Producing E-Scaffold Is Active against Monomicrobial and Polymicrobial Biofilms

Oxidizing agents like hypochlorous acid (HOCl) have antimicrobial activity. We developed an integrated electrochemical scaffold, or e-scaffold, that delivers a continuous low dose of HOCl aimed at targeting microbial biofilms without exceeding concentrations toxic to humans as a prototype of a device being developed to treat wound infections in humans. In this work, we tested the device against 33 isolates of bacteria (including isolates with acquired antibiotic resistance) grown as in vitro biofilms alongside 12 combinations of dual-species in vitro biofilms. Biofilms were grown on the bottoms of 12-well plates for 24 h. An integrated e-scaffold was placed atop each biofilm and polarized at 1.5 V for 1, 2, or 4 h. HOCl was produced electrochemically by oxidizing chloride ions (Cl^-) in solution to chlorine (Cl₂); dissolved Cl₂ spontaneously dissociates in water to produce HOCl. The cumulative concentration of HOCl produced at the working electrode in each well was estimated to be 7.89, 13.46, and 29.50 mM after 1, 2, and 4 h of polarization, respectively. Four hours of polarization caused an average reduction of 6.13 log₁₀ CFU/cm² (±1.99 log₁₀ CFU/cm²) of viable cell counts of monospecies biofilms and 5.53 log₁₀ CFU/cm² (±2.31 log₁₀ CFU/cm²) for the 12 dual-species biofilms studied. The described integrated e-scaffold reduces viable bacterial cell counts in biofilms formed by an array of antibiotic-susceptible and -resistant bacteria alone and in combination.