Silk is a natural fiber spun by moths and has been used for thousands of years to make strong, fine fabrics and surgical sutures to close wounds.

More recently, scientists have broken down the fiber into its basic protein component, silk fibroin, and reconstituted it into gels, films, sponges, and other forms that react and color from implantable orthopedic screws. I learned to create everything from changing textile inks. to body chemistry.

Krishna Kumar, Robinson Professor of Chemistry at Tufts University, said, “The reason silk is such a unique material is that not only can it take on many different shapes and forms, but silk fibroin can be chemically modified.” By doing so, you can easily change its characteristics.

“If you want to use silk fibroin to make orthopedic screws that are absorbed by the body at different rates, you change the chemistry,” he said. If you want to make a blood sensor that detects , you change the chemistry.In this study, we modified silk fibroin to repel water, a material that is more or less water-repellent.”

The progress was reported in a magazine ChemBioChem.

To turn silk into a water-repellent material, it was necessary to coat the surface of silk fibroin with short chemical chains containing carbon and fluorine called perfluorocarbons. These chains are very stable and do not react with other chemicals or interact with proteins or other biological chemicals in the body.

The natural surface of silk proteins acts like a magnet for water, with the negatively and positively charged branches of silk attracting water, whereas perfluorocarbon-covered silk proteins are susceptible to water grabbing. Very few.

Perfluorocarbons also resist attractive forces caused by other forces that normally attract molecules. By varying the number and length of the perfluorocarbon chains of the silk protein, its “stickiness” can be tuned. Assistant Professor of Chemistry Luke Davis established the level of fluorine required for a silk surface to be non-sticky.

Because chemical synthesis takes place under mild conditions, the manufacturing process can be safer for both workers and the environment, unlike the production of other non-sticky substances.

Tufts researchers measured non-stickiness by observing how water beaded onto the surface of the material, like water rolling off a waxed car. In fact, non-stick silk, which is molded into bars using the highest level of perfluorocarbon, curls water into even more rounded drops than Teflon.

Not only water rolls off the Teflon-coated silk, but all water-based substances such as various foods, blood, cells and tissues. Although not tested in this study, perfluorinated materials are known to repel oils.

“Modifying medical devices to prevent harmful interactions with water and other biologics may maintain their strength and integrity for as long as needed,” said a graduate student in Kumar’s lab and co-author of the paper. Author Julia Fountain explains. “Because silk is already relatively inert to the immune system, modulating its ability to fight off cells and other substances could make silk even more useful.”

The benefits of a highly non-stick surface extend far beyond medical applications. Although there are concerns about chemicals being absorbed into the body from commercially available non-stick coatings, silk-based non-stick surfaces may offer an alternative option whose relative safety can be considered.

You can also imagine a car windshield that allows rainwater to roll off without the use of wipers, a coating on metal that helps prevent rust, or a coating that makes fabric easier to clean.

“Success in modifying silk to repel water has been demonstrated by chemically modifying silk for other functions, such as changing color, conducting electrical charges, and the ability to persist and degrade in biological environments. We will build on our success in qualifying,” said David Kaplan, Stern. Family professor at Tufts Institute of Technology. “As a protein, silk lends itself to modular chemistry, the ability to ‘plug’ different functional components into a natural scaffold. ”