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New approach to activating oxygen may be used to treat cutaneous infections

An updated approach using light-activated oxygen to terminate methicillin-resistant Staphylococcus aureus (MRSA) bacteria has been shown to be efficacious. The method may be a new alternative to antibiotics in treating wounds to eliminate infection and assist in healing. These findings will be presented at the 256th National Meeting & Exposition of the American Chemical Society (ACS) in Boston on Tuesday, Aug. 21 at 3 p.m. Eastern time. The presentation will be broadcast live on the ACS YouTube channel.

“Instead of resorting to antibiotics, which no longer work against some bacteria like MRSA, we use photosensitizers, mostly dye molecules, that become excited when illuminated with light,” said study author Peng Zhang, PhD, associate professor of Chemistry and Materials Science at the University of Cincinnati, in a press release. “Then, the photosensitizers convert oxygen into reactive oxygen species that attack the bacteria.”

Dr. Zhang and his colleagues designed a new, water-dispersible, hybrid photosensitizer—one that features noble metal nanoparticles decorated with amphiphilic polymers to entrap the molecular photosensitizers. The new photosensitizer was much more effective at killing a variety of bacteria than corresponding formulations that did not contain the metal particles. The metal has a plasmonic enhancement effect that promotes the generation of more reactive oxygen species, while also concentrating the photosensitizers in one place for a more localized hit to the bacterial cells.

Bacteria with nanoparticle photosensitizers grow before illumination (left),

but are killed after illumination (right) as oxygen is activated.

Photo by Dr. Peng Zhang.

“If you want to attack a castle, and you just let all these people attack individually, it is not very effective. Instead, if you have the same number of people grouped together attacking the castle at one point, it is possible to cause more damage,” said Dr. Zhang.

A design of the hybrid photosensitizers has been patented by Dr. Zhang and his team. It can be formulated into a spray or gel form. Once the spray is developed, medical professionals can put it on any surface and then illuminate it with blue or red light to clean away MRSA and other bacteria that may be present.

The nanoparticles also show potential in destroying skin cancer cells as they perform effectively with the illumination of red light, which has a long wavelength that penetrates deep below the skin.

In the past, other scientists have attempted to use similar versions of photocatalysts to kill bacteria. Their designs were unable to destroy enough microorganisms to effectively reduce infections because photosensitizers in a molecular form are usually not concentrated enough to do significant damage. In addition, many of them were hydrophobic, making it difficult to disperse them in aqueous media where microorganisms typically exist.

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