Mild Electric Current Disrupts Bacterial Biofilms

A novel wound-healing technology uses an electrochemical scaffold (e-scaffold) and enhanced antibiotic susceptibility to eradicate biofilms and persister cells.

Researchers at Washington State University (Spokane, WA, USA) used an e-scaffold made out of conductive carbon fabric and a mild electrical current to produce a low, constant concentration of hydrogen peroxide (H2O2, an effective disinfectant) at the e-scaffold surface. The H2O2 disrupts the biofilm matrix and damages the bacteria cell walls and DNA, which allows better antibiotic penetration and efficacy against subpopulations of persister cells that survive treatment and are able to grow and multiply, resulting in chronic infections.

The researchers found that the e-scaffold enhanced tobramycin susceptibility in P. aeruginosa biofilms, which reached a maximum susceptibility at 40 µg/ml tobramycin, leading to complete elimination. In addition, the e-scaffold eradicated persister cells in the biofilms, leaving no viable cells. The researchers also observed that the e-scaffold induced intracellular formation of hydroxyl free radicals and improved membrane permeability in biofilm cells, which possibly enhanced the antibiotic susceptibility and eradication of persister cells. The study was published on November 23, 2016, in npj Biofilms and Microbiomes.

“Similar to the way that penicillin was discovered by accident, the research to develop the e-scaffold actually came out of a failed attempt to improve fuel cells,” said lead author Professor Haluk Beyenal, PhD, of the WSU School of Chemical Engineering and Bioengineering. “As engineers, we are always trying to find solutions to a problem, so we decided to use bad cathodes to control biofilm growth, and it worked. Our inspiration came from the fundamental work to understand its mechanism.”

Biofilms protect bacterial communities in part because the extracellular polymeric substances (EPS) that form the biofilm matrix serve as a diffusion barrier that limits antibiotic penetration and immobilizes antibiotics. The diffusive barrier also results in nutrient gradients, causing decreased growth and metabolic inactivity in parts of the biofilm community, which allows persister cells to arise. Increased persister cell formation is particularly observed in Gram-negative bacterial biofilms, as their cell membranes are composed of lipopolysaccharides that further limit antibiotic penetration.

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