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Approach paves way for new generation of antimicrobial materials

iStock photo: Sterilizing solution wash

Researchers in the College have successfully incorporated “photosensitizers” into a range of polymers, giving those materials the ability to render bacteria and viruses inactive using only ambient oxygen and visible-wavelength light. The new approach opens the door to a range of new products aimed at reducing the transmission of drug-resistant pathogens.

“The transmission of antibiotic-resistant pathogens, including so-called ‘superbugs,’ poses a significant threat to public health, with millions of medical cases occurring each year in the United States alone,” said Dr. Reza Ghiladi, associate professor of chemistry at NC State and co-corresponding author of a paper on the research. “Many of these infections are caused by surface-transmitted pathogens.

“Our goal with this work was to develop materials that are self-sterilizing, nontoxic and resilient enough for practical use. And we’ve been successful.”

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“A lot of work has been done to develop photosensitizer molecules that use the energy from visible light to convert oxygen in the air into biocidal ‘singlet’ oxygen, which effectively punches holes in viruses and bacteria,” said Dr. Richard Spontak, Distinguished Professor in the Department of Chemical and Biomolecular Engineering (CBE) and co-corresponding author of the paper. “There is no resistance to this mode of action.

“However, the bulk of previous work in this area has been done using substrates — such as cellulose — that are not practical for daily use in places like hospitals. Our work here moves well beyond that.”

The new approach involves incorporating photosensitizers into hydrophobic, semi-crystalline elastomers, which are waterproof and mechanically resilient — while also allowing oxygen to access the photosensitizers. What’s more, the distribution of photosensitizers in the material means that it will retain its antimicrobial properties even if the surface of the material is scratched or worn away.

“This paper focuses on one class of polymers, but it is a fundamental proof of concept that demonstrates the ability to put these photosensitizers into a range of robust ‘soft’ materials without sacrificing functionality,” said Spontak, who is also a professor in the Department of Materials Science and Engineering. “This is the tip of the iceberg.”

In lab testing, the researchers found that a photosensitizer-embedded polymer inactivated at least 99.89 percent of five bacterial strains — and 99.95 percent of two viruses — when exposed to light for 60 minutes.

First author of the paper is Bharadwaja Peddinti, a Ph.D. student in CBE. The paper was co-authored by Dr. Frank Scholle, associate professor of biological sciences at NC State.

Return to contents or download the Spring/Summer 2019 NC State Engineering magazine (PDF, 13.7MB).

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