Shark skin inspires new antibacterial material
To limit hospital- and clinic-related infections, institutions have been using new materials, such as one commercially available that mimics shark skin, to inhibit microbes’ ability to stick to high-touch areas such as bed rails and door knobs. But given time, bacteria will accumulate, making this method insufficient, say researchers led by polymer scientist James Watkins at the University of Massachusetts Amherst.
Now in a report available early online today in the American Chemical Society journal ACS Applied Materials & Interfaces, Watkins and chemical engineer Jessica Schiffman, with a team of their graduate students, say they have designed an easily applied coating infused with photocatalytic antimicrobial titanium dioxide (TiO2) nanoparticles that decreases microbial attachment and deactivates those bacteria already attached to surfaces.
As they explain, when TiO2 nanoparticles are exposed to ultraviolet (UV) light, chemical reactions with water and hydroxide molecules form reactive hydroxyl radicals and superoxide ions that rupture the outer membranes of bacteria on contact and lead to cell death. Further, TiO2 nanoparticles are low-cost, widely available and can be incorporated into transparent coatings, unlike more commonly known antimicrobials such as silver and copper. “These advantages make TiO2 an attractive candidate for use in high-touch antimicrobial surface coatings,” they point out.
First author and polymer science doctoral candidate Feyza Dundar Arisoy and colleagues used roll-to-roll advanced manufacturing capabilities in Watkins’ laboratory at UMass Amherst’s Institute for Applied Life Sciences to print their own shark skin-mimicking surfaces of polymer and ceramic composites impregnated with TiO2 nanoparticles.
They report that in their experiments, shark skin surface without nanoparticles reduced the attachment of E. coli by 70 percent compared to smooth films. But shark skin surfaces with TiO2 nanoparticles exposed to UV light for one hour killed over 95 percent of E. coli and 80 percent of harmful Staphylococcus aureus.
The researchers add that surface properties of their nanoimprinted lithography materials can be tuned for different applications and environments, from soft and pliable polymers to extremely hard and wear-resistant ceramics, and their fabrication method can be scaled up for mass production of high-performance coatings that repel and inactivate bacteria.
Arisoy and colleagues note, “To the best of our knowledge, this work represents the first reported use of antibacterial nanoparticles in shark-skin patterns. The combination of passive and active strategies on a single surface is the most promising material design strategy to control bacterial fouling.”
This work was supported by the National Institutes of Health, National Science Foundation and U.S. Army Laboratories.