Motivation of Electroceutical Bandages for Treatment of Chronically Infected Wounds
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Series/Report no.:2016 Edward F. Hayes Graduate Research Forum. 30th
In the United States, 6.5 million patients are affected by chronic wounds, sometimes complicated by infection. If the bacteria form a biofilm at the wound site, treatment of the infection becomes significantly more difficult. Biofilm bacteria are 500 to 5,000 times more resistant to antibiotic medications than the non-biofilm bacteria. Previous studies have shown that electric current enhances the activity of various antibiotics against biofilm-forming bacterial strains such as Pseudomonas aeruginosa and Staphylococcus epidermidis. This behavior has been referred to as the electro-bactericidal effect. A large parametric investigation with various substrates, conductive patterns, and designs has led to a novel electroceutical bandage comprised of a silver-based ink on silk fabric, connected to a 6 V DC battery source and switch circuit for easy operation. Currently, characterizing the electroceutical bandage includes in vitro tests using the bacterial strain Pseudomonas aeruginosa to test the efficacy of biofilm inhibition. The results have shown that our dressing successfully and repeatedly prevents the bacteria from forming a biofilm, as well as excludes bacteria from the anode of the bandage. It is noteworthy that use of an isolated electrode system i.e., electric field applied to the bacteria without direct flow of current through the bacterial layers, did not yield inhibition of the biofilm formation. Therefore, mechanistically, one may expect oxidation reactions at the anode to be important. This hypothesis is the subject of further on-going experiments. Further in vitro tests studying the effects of the bandage on already established biofilms have been initiated as well. It is important to study both scenarios because this electroceutical bandage should prevent infection from developing at the wound site, as well as help treat existing infections. Severe biofilm infection can lead to amputation to prevent spread of infection. If more reliable and successful means of treating biofilm infections can be implemented, complications of chronic wounds will be reduced. We have shown that engineered bandages with direct electric current flow between the wound-bandage interface inhibit bacterial growth at and around the anode. Due to this result, the conductive pattern design has been optimized to maximize this effect by increasing the surface area of the anode with respect to the available space on an average dressing of 5 cm x 5 cm. Currently, our measurements show a power density of 0.75 mW/cm2, well below the FDA limit of 0.25 W/cm2 for thermal burns therefore implying likely safe use of the dressing. We hypothesize that the direct electric current is disrupting quorum sensing, or communication between the bacteria, effectively isolating them from each other due to oxidative stress at the anode. We believe this isolation prevents bacteria from forming a biofilm. The future experiments will focus on developing a more comprehensive understanding of the mechanisms behind biofilm inhibition in presence of low-magnitude direct currents.
Poster Division: Engineering, Math, and Physical Sciences: 2nd Place (The Ohio State University Edward F. Hayes Graduate Research Forum)
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