Silver ions prove effective in preventing, killing MRSA while forming bone

Video reproduced with permission from KOMU-TV. Original airdate: March 5, 2017.

Methicillin resistant Staphylococcus aureus, or MRSA, infections are a critical problem in the medical world, including the area of regenerative medicine. This form of antibiotic-resistant staph infection can cause serious complications after typical invasive procedures and can be easily spread through skin-to-skin contact. MRSA is one of the foremost causes of osteomyelitis, a disease that inflames and destroys bone as well as surrounding soft tissue.

But University of Missouri College of Engineering Dean and Bioengineering Professor Elizabeth Loboa and a team of colleagues — Mahsa Mohiti-Asli and Casey Molina of the Joint Department of Biomedical Engineering at the University of North Carolina and North Carolina State University, Diteepeng Thamonwan of Silpakorn University in Thailand and Behnam Pourdeyhimi of NCSU — recently discovered a way to slow and, in some cases, prevent the spread of MRSA while also regenerating new bone.

Bone scaffolds seeded with MRSA.

This microscopic image shows the scaffolds after the MRSA bacteria was introduced. Photo by Mahsa Mohiti-Asli/North Carolina State University.

Loboa and her colleagues discovered that by seeding the proper amount of silver into a biodegradable scaffold alongside bone-forming stem cells, they could still rapidly form bone while either inhibiting MRSA growth or killing the infection outright.

“The silver ions go in and completely disrupt the MRSA cell machinery, and they can inhibit growth and kill the bacteria,” Loboa said. “It’s a fine line. If you overuse too much of the silver, it’s bad for the mammalian cells. We want to make sure we don’t hurt our host cells but kill the bacterial cells.”

The threads of the bone-creating scaffold were coated with a silver ion-containing solution before testing. Silver has proven effective in undoing bacteria mechanically, making it harder for bacteria to develop immunity.

“Bacteria are fantastic evolutionary entities,” Loboa said. “They have a very quick evolutionary response to stress in their environment, so in order for them to survive, they had to evolve to combat these antibiotics.”

Their findings, “Evaluation of Silver Ion-Releasing Scaffolds in a 3-D Coculture system of MRSA and Human Adipose-Derived Stem Cells for Their Potential Use in Treatment or Prevention of Osteomyelitis” recently was published in the journal Tissue Engineering, Part A. The study was the first of its kind to develop a 3-D coculture system to evaluate antimicrobial scaffolds — using both human adipose-derived stem cells (adult stem cells isolated from fat) and MRSA cells at the same time.

Slowing the spread of MRSA has a personal motivation for Loboa. Her daughter contracted the bacteria several years ago while attending a summer camp, and she saw firsthand how painful and debilitating the infection can be.

“MRSA’s really scary. My daughter came home with it, and it is horrible. … It’s such a painful, painful sight,” Loboa said. “And you have to be incredibly careful, because you don’t want to get it on you or spread it to anyone else. You have to bandage it very carefully.”

This discovery opens the door to even more applications, including use in treating other bone infections, engineering bone in already infected sites and coating for bone implants to prevent infection. It is a key first step in the fight against surgically related bone infections.

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