Common Ingredient in Sunscreen May Be An Effective Antibacterial Coating For Medical Devices

Zinc oxide – an ingredient commonly found in sunscreens – may be effective at preventing microbial growth on medical device implants including pacemakers and artificial hips. Research conducted at the University of Michigan suggests that a coating of zinc oxide nanopyramids on medical device implants disrupted the growth of methicillin-resistant Staphylococcus aureus (MRSA), and reduced the biofilm by 95 percent.

It’s estimated that approximately 1 million medical devices become infected with MRSA and other hard-to-treat pathogens every year. “It is extremely difficult to treat these infections,” said J. Scott VanEpps, a clinical lecturer and research fellow in the University of Michigan Medical School’s department of emergency medicine, and a researcher working on the project.

According to VanEpps, traditional treatment for medical implant infections typically involved a long course of antibiotics, which can themselves lead to further antibiotic resistance. If the infection is not managed correctly, the implant may need to be replaced resulting in expensive surgery.

For doctors, the ideal treatment for these infections would be to prevent them from occurring in the first place. One way of achieving this would be to coat the devices with a film that would prevent bacterial growth.

The new research – published in the journal Nanomedicine – shows that a coating of nanoparticles of zinc oxide, could prevent bacterial growth on the implant, and subsequent infections. The nanoparticles are shaped like a pyramid – with a hexagonal base – which is an effective shape at preventing the bacterial enzyme beta-galactosidase from reducing lactose to glucose and galactose – the main sugar fuel source for the bacteria.

The nanoparticles inhibit the action of beta-galactosidase by interfering with the enzyme’s ability to twist, creating a groove for the lactose to fit into. According to Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Chemical Engineering, whose group made the nanoparticles, “Although more studies need to be carried out, we believe that zinc oxide nanopyramids interfere with this twisting motion.”

The researchers believe that the point of the nanopyramids inserts itself into the catalytic groove of the enzyme, completely preventing it from catalyzing lactose into the simple sugars. Without the ability to break down lactose, the bacteria are unable to survive.

They tested the efficacy of the nanopyramids on four bacterial species: two staphylococcal strains (including MRSA), E. coli, and a bacterial strain that causes pneumonia. After 24 hours of growth, the number of live staphylococcal cells recovered from the nanopyramid-coated growth surface was 95 percent less than those from an uncoated surface.

VanEpps and his team found that while the MRSA bacteria were susceptible to the coating, the pneumonia and E. coli species were more resistant. “While the coating was unable to completely eradicate all staphylococcal cells, this dramatic reduction could likely enable antibiotic treatments to succeed or simply allow the human immune system to take over without the need for antibiotics,” said VanEpps.

The researchers stress that more research on the zinc oxide coating must be completed before it can ever be used to prevent medical implant infections in humans. In particular, they must determine how the nanopyramids would affect human cells and whether they could be effective at preventing growth of other microbial species.

“The strong antibacterial activity against MRSA and other pathogens is an exciting finding,” said Kotov. “We want to better understand the mechanisms of the antibacterial function to fine tune its inhibitory activity and to identify the structural similarities among enzymes that pyramidal nanoparticles can inhibit.”

Sources:

• Sunscreen ingredient may prevent medical implant infections – http://www.medicalnewstoday.com/releases/302448.php
• McGuffie, M., Hong, J., Glynos, E., Green, P., Kotov, N., Younger, J., VanEpps, J. (2015). Zinc Oxide Nanoparticle Suspensions and Layer-By-Layer Coatings Inhibit Staphylococcal Growth. Nanomedicine.