Activity of a hypochlorous acid-producing electrochemical bandage as assessed with a porcine explant biofilm model.

The activity of a hypochlorous acid-producing electrochemical bandage (e-bandage) in preventing methicillin-resistant Staphylococcus aureus infection (MRSA) infection and removing biofilms formed by MRSA was assessed using a porcine explant biofilm model. e-Bandages inhibited S. aureus infection (p = 0.029) after 12 h (h) of exposure and reduced 3-day biofilm viable cell counts after 6, 12, and 24 h exposures (p = 0.029). Needle-type microelectrodes were used to assess HOCl concentrations in explant tissue as a result of e-bandage treatment; toxicity associated with e-bandage treatment was evaluated. HOCl concentrations in infected and uninfected explant tissue varied between 30 and 80 µM, decreasing with increasing distance from the e-bandage. Eukaryotic cell viability was reduced by an average of 71% and 65% in fresh and day 3-old explants, respectively, when compared to explants exposed to nonpolarized e-bandages. HOCl e-bandages are a promising technology that can be further developed as an antibiotic-free treatment for wound biofilm infections.

Efficacy and toxicity of hydrogen peroxide producing electrochemical bandages in a porcine explant biofilm model.

AIMS: Effects of H2 O2 producing electrochemical-bandages (e-bandages) on methicillin-resistant Staphylococcus aureus colonization and biofilm removal were assessed using a porcine explant biofilm model. Transport of H2 O2 produced from the e-bandage into explant tissue and associated potential toxicity were evaluated. METHODS AND RESULTS: Viable prokaryotic cells from infected explants were quantified after 48 h treatment with e-bandages in three ex vivo S. aureus infection models: (1) reducing colonization, (2) removing young biofilms and (3) removing mature biofilms. H2 O2 concentration-depth profiles in explants/biofilms were measured using microelectrodes. Reductions in eukaryotic cell viability of polarized and nonpolarized noninfected explants were compared. e-Bandages effectively reduced S. aureus colonization (p = 0.029) and reduced the viable prokaryotic cell concentrations of young biofilms (p = 0.029) with limited effects on mature biofilms (p > 0.1). H2 O2 penetrated biofilms and explants and reduced eukaryotic cell viability by 32-44% compared to nonpolarized explants. CONCLUSIONS: H2 O2 producing e-bandages were most active when used to reduce colonization and remove young biofilms rather than to remove mature biofilms. SIGNIFICANCE AND IMPACT OF STUDY: The described e-bandages reduced S. aureus colonization and young S. aureus biofilms in a porcine explant wound model, supporting their further development as an antibiotic-free alternative for managing biofilm infections.

Hydrogen peroxide-producing electrochemical bandage controlled by a wearable potentiostat for treatment of wound infections.

Chronic wound infections caused by biofilm-forming microorganisms represent a major burden to healthcare systems. Treatment of chronic wound infections using conventional antibiotics is often ineffective due to the presence of bacteria with acquired antibiotic resistance and biofilm-associated antibiotic tolerance. We previously developed an electrochemical scaffold that generates hydrogen peroxide (H2 O2 ) at low concentrations in the vicinity of biofilms. The goal of this study was to transition our electrochemical scaffold into an H2 O2 -generating electrochemical bandage (e-bandage) that can be used in vivo. The developed e-bandage uses a xanthan gum-based hydrogel to maintain electrolytic conductivity between e-bandage electrodes and biofilms. The e-bandage is controlled using a lightweight, battery-powered wearable potentiostat suitable for use in animal experiments. We show that e-bandage treatment reduced colony-forming units of Acinetobacter buamannii biofilms (treatment vs. control) in 12 h (7.32 ± 1.70 vs. 9.73 ± 0.09 log10 [CFU/cm2 ]) and 24 h (4.10 ± 12.64 vs. 9.78 ± 0.08 log10 [CFU/cm2 ]) treatments, with 48 h treatment reducing viable cells below the limit of detection of quantitative and broth cultures. The developed H2 O2 -generating e-bandage was effective against in vitro A. baumannii biofilms and should be further evaluated and developed as a potential alternative to topical antibiotic treatment of wound infections.

Anti-Biofilm Activity of a Tunable Hypochlorous Acid-Generating Electrochemical Bandage Controlled By a Wearable Potentiostat.

Chronic wound biofilm infections represent a major clinical challenge which results in a substantial burden to patients and healthcare systems. Treatment with topical antibiotics is oftentimes ineffective as a result of antibiotic-resistant microorganisms and biofilm-specific antibiotic tolerance. Use of biocides such as hypochlorous acid (HOCl) has gained increasing attention due to the lack of known resistance mechanisms. We designed an HOCl-generating electrochemical bandage (e-bandage) that delivers HOCl continuously at low concentrations targeting infected wound beds in a similar manner to adhesive antimicrobial wound dressings. We developed a battery-operated wearable potentiostat that controls the e-bandage electrodes at potentials suitable for HOCl generation. We demonstrated that e-bandage treatment was tunable by changing the applied potential. HOCl generation on electrode surfaces was verified using microelectrodes. The developed e-bandage showed time-dependent responses against in vitro Acinetobacter baumannii and Staphylococcus aureus biofilms, reducing viable cells to non-detectable levels within 6 and 12 hours of treatment, respectively. The developed e-bandage should be further evaluated as an alternative to topical antibiotics to treat wound biofilm infections.

Rapid differentiation of antibiotic-susceptible and -resistant bacteria through mediated extracellular electron transfer.

Conventional methods for testing antibiotic susceptibility rely on bacterial growth on agar plates (diffusion assays) or in liquid culture (microdilution assays). These time-consuming assays use population growth as a proxy for cellular respiration. Herein we propose to use mediated extracellular electron transfer as a rapid and direct method to classify antibiotic-susceptible and -resistant bacteria. We tested antibiotics with diverse mechanisms of action (ciprofloxacin, imipenem, oxacillin, or tobramycin) with four important nosocomial pathogens (Acinetobacter baumannii, Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae) by adding the bacterial culture to a custom-designed electrochemical cell with a glassy-carbon electrode and growth media supplemented with a soluble electron transfer mediator, phenazine methosulfate (PMS). During cell respiration, liberated electrons reduce PMS, which is then oxidized on the electrode surface, and current is recorded. Using this novel approach, we were able to consistently classify strains as antibiotic-resistant or -susceptible in <90 min for methodology development and <150 min for blinded tests.

Electrochemical precipitation of neptunium with a micro electrochemical quartz crystal microbalance.

Microliter volumes are used in electrochemical detection and preconcentration of radionuclides to reduce the dose received by researchers and equipment. Unfortunately, there is a lack of analysis of radionuclides with coupled electrochemical techniques and microliter volume reactors. The goals of this work are 1) to develop a miniaturized micro-electrochemical quartz crystal microbalance (µeQCM) reactor for use in small volume (50-200 µL) electrogravimetric experiments and 2) to use this reactor to characterize the preconcentration of neptunium on carbon electrodes via electroprecipitation. We successfully deposited neptunium in the new µeQCM reactor and verified its operation. We found that preconcentration of neptunium on carbon coated electrodes was possible by chronoamperometry at -1.6 VAg/AgCl. The mass shift of the resulting precipitate was indicative of the amount of neptunium on the electrode, although the correlation between the mass increase and activity of the preconcentrated material was not linear. Neptunium precipitate reduced electron transfer to the solution as evidenced by the increase in charge transfer resistance compared to bare electrodes.