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Cullen College Engineers Discover Innovative Method to Destroy Bacteria

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By: 

Ashley Schwartz

Researchers at the Cullen College of Engineering have discovered an innovative method for destroying bacteria in a matter of seconds by using light to heat highly porous gold nanodisks. A research paper describing the method was featured on the cover of the April issue of Optical Materials Express.

The paper, titled “Photothermal inactivation of heat-resistant bacteria on nanoporous gold disk arrays,” was authored by Cullen College professors Wei-Chuan Shih and Debora Rodrigues, post-doctoral fellows Greggy Santos and Felipe Ibañez de Santi Ferrara, and doctoral student Fusheng Zhao.

In 2013, Shih, an associate professor of electrical and computer engineering, laid the foundation for this research with his discovery that porous gold nanoparticles can reach high temperatures through light absorption. The porosity of the disk-like nanoparticles he studied increased heating efficiency while maintaining stability.

Shih said that once he recognized the novelty of this discovery, he started designing additional experiments to research potential applications for the efficient heating process.

“It was important that [my colleagues and I] developed a method of heating that was fast and didn’t require a large amount of power in order for it to be effective in real world applications,” Shih said.

To explore the potential application for sterilization, Shih enlisted the help of Rodrigues, an assistant professor of civil and environmental engineering. Rodrigues provided bacterial samples of E. coli and performed cell viability tests. Working in Shih’s lab, Santos and Ibañez de Santi Ferrara exposed nanodisks covered with E. coli bacteria to infrared light to study the effect of rapid temperature elevation on the bacteria. When the infrared light raised the surface temperature of the nanodisks to 390 degrees Fahrenheit, all of the E. coli cells were destroyed within seconds.

“Current methods of sterilization involve boiling water or using hot steam, which can take several minutes to hours,” Shih said. “What we show with this research is that in just five to 25 seconds, the bacteria is dead and the disinfection is complete.”

This new method of sterilization could revolutionize how we treat and avoid infections, said Shih. For example, hospitals could use the nanodisks as a catheter coating to improve sterilization and reduce the number of infections contracted through catheters. Currently, the majority of patients who undergo long-term catherization may experience complications due to bacterial growth and contamination.

Shih said there is also potential for this method to be incorporated into future cancer treatments. Cancer cells are more fragile than E. coli bacteria and require a change of just two degrees Celsius to kill the cell. Shih said he envisions scientists using a “targeting” method to locate and attack a tumor within a patient’s body. In theory, a nanoparticle coated with an antibody would bind to the tumor cell surface and, once bound, scientists could attack the cancer cells by shining a light on the nanoparticle to increase its temperature.

“The research [in Optical Materials Express] discusses the application of this method to catheters, but the possibilities of future healthcare applications are exciting to us,” Shih said.

Since publication, this work has been featured by Forbes and the Optical Society of America

Optical Materials Express emphasizes advances in novel optical materials, exploring their properties, modeling, synthesis and fabrication approaches, as well as how such materials contribute to novel optical behavior and how they enable new or improved optical devices.

This issue of Optical Materials Express can be found here.

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