Magnetic Fields Turn Up the Heat on Bacterial Biofilms
A short exposure to an alternating magnetic field might someday replace multiple surgeries and weeks of intravenous (IV) antibiotics as treatment for stubborn infections on prosthetic joints, new research suggests.
In a study published in Scientific Reports, researchers at UT Southwestern Medical Center have shown that high-frequency alternating magnetic fields – the same principle used in induction cook tops – can be used to destroy bacteria that are encased in biofilm growing on a metal surface. Technology developed by Rajiv Chopra, PhD, and David Greenberg, MD, uses this method to heat the surface of prosthetic metal joints and destroy bacterial biofilms.
When a metal is in the presence of alternating magnetic fields (AMFs), electrical currents are produced on the metal, generating heat. Rapidly switching the direction of the magnetic fields back and forth (ie, high frequency) allows the electrical currents to flow only along the outer edge of the metal, which is where the biofilm is found.
“That was the light bulb in the conversation,” Dr. Chopra said. “You have a pathogen that can’t be treated with conventional drugs. You have a physical effect – heating on the surface of a metal – that’s often a complication for imaging technologies such as MRI. We’ve taken 2 things that are problems and, by putting them together, we’ve turned up a solution.”
Dr. Greenberg noted that biofilm-related infections are one of the most serious complications of knee and hip replacements, often requiring multiple surgeries. “We were looking for better ways to target and treat biofilms,” he said. “Our idea was to put a coil around the joint and run a current through it to create alternating magnetic fields. Human tissue isn’t conductive but metal is, so only the implant would heat up.”
Using prosthetic joint models, the researchers showed that heating the metal surface via AMFs destroyed biofilm and killed bacteria. They tested several species of bacteria that create biofilm on artificial joints, and the process worked with each type.
Mouse-model safety tests indicated that high-power, short-duration doses of AMF minimize heat damage to adjoining tissue. High power achieves a target temperature on the surface of the metal device quickly, before there is much time for heat to accumulate in surrounding tissues.
Chopra R, Shaikh S, Chatzinoff Y, et al. Employing high-frequency alternating magnetic fields for the non-invasive treatment of prosthetic joint infections. Sci Rep. 2017 Aug 8;7(1):7520. doi: 10.1038/s41598-017-07321-6.