TAGS: Smart Coatings
Researchers at Texas A&M University have created a coating that can be applied to food-contact surfaces, like conveyor belts, rollers and collection buckets to prevent cross-contamination between fresh produce. In addition to being germicidal, the researchers have designed their coating to be extremely water-repellent. They said without water, bacteria cannot stick or multiply on surfaces, thereby drastically curbing contamination from one produce item to another.
Dual-function Coating to Reduce Bacterial Spread
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In our study, we show that our new dual-function coating — one that can both repel and kill bacteria — can greatly mitigate bacterial spread, averting cross-contamination,” said Dr. Mustafa Akbulut, associate professor in the Artie McFerrin Department of Chemical Engineering.
Contaminated produce items can spread the pathogens either directly, by touching other food items, or indirectly, via food-contact surfaces. Currently, there are several ways to prevent indirect transmission ranging from antimicrobial surface coatings to antifouling polymer surfaces that act like springs to push bacteria away. However, the researchers said for a variety of reasons, these approaches, although efficient at first, can lose their effects over time.
Surface Coating with Hydrophobic Nature
To overcome the obstacles posed by the current technologies, Akbulut and his team proceeded to create an antimicrobial surface coating that is also extremely hydrophobic. They noted the coating’s water-repelling property can help food-contact surfaces retain their germicidal action much longer.
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Most bacteria can only survive in an aqueous environment,” said Akbulut. “
If surfaces are superhydrophobic, then water, and along with it most of the bacteria will be repelled away. With fewer bacteria around, less germicides are used up, increasing the overall lifetime of the coating.”
Creation Process of Dual-function Coating
To make their dual-function coating, Akbulut and his team started with an aluminum sheet, a metal commonly used in the food industry for contact surfaces. Onto the surface of the metal, they chemically attached a thin layer of a compound called silica using high heat. Then, with this layer as a substrate, they added a mixture of silica and a naturally occurring germicidal protein found in tears and egg white called lysozyme.
Together, the silica-aluminum layer bound to the silica-lysozyme layer made a coating that had a rough texture when viewed at microscopic scales. The researchers noted that this submicroscopic roughness, or the tiny bumps and crevices on the coating, is key to super hydrophobicity.
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In general, if you increase roughness, the hydrophobicity of a material increases, but there is a limit,” said Shuhao Liu, a graduate student in the College of Engineering and the primary author of the study.
“If the coating is too rough, bacteria can once again hide behind crevices and contaminate. So, we tweaked the proportion of silica and lysozyme so that the roughness yielded the best possible hydrophobicity without compromising the coating’s overall function.”
Testing Against Disease-causing Bacteria
When their superhydrophobic, lysozyme-infused coating was fine-tuned and ready, the researchers tested if it was effective at curbing the growth of two strains of disease-causing bacteria, Salmonella typhimurium and Listeria innocua. Upon examination, they found that the number of bacteria on these surfaces was 99.99% lesser than that on bare surfaces.
Source: Texas A&M University