Green Tea, Chocolate, and Wine Inspire Anti-Bacterial Coating

CC BY 2.0. Dominic Lockyer

Do you know that haze of purple left in your wine glasses when you wake up the morning after a party? Or that tea stain you cannot quite completely clean out of your favorite mug?

Did you know that polyphenols cause those annoying discolorations? Yes, the same polyphenols credited for the health benefits of wine, tea, and chocolate. Polyphenols are amazing compounds that can scavenge free radicals, absorb ultraviolet radiation, complex metal ions, and kill bacteria. On top of that, they are sticky -- which you could have guessed from the rings wine and tea leave on glass and porcelain.

Teacup stain

Toshiyuki IMAI/CC BY 2.0
Those stains inspired scientists from Northwestern University who have proven that cheap and easily available polyphenols can be used to create coatings with antibacterial properties. Due to the incredible stickiness of polyphenols, even the famous non-stick surface Teflon cannot resist the adherent coating. According to Phillip B. Messersmith, who led the research:

We discovered a way to apply coatings onto a variety of surfaces that takes advantage of the sticky properties of the polyphenol compounds. It’s a very simple dip-coating process, and the antibacterial and antioxidant properties are preserved in the coating.

This could be good news, both to reduce the potential hazards of antibacterial chemicals coatings and as an inexpensive, effective way to protect surfaces in many applications. For example, a hip replacement could be dipped and coated with a layer of polyphenols so thin it will not disturb the functionality of the device but will suppress infections and extend the lifespan of the implant. Or these coatings could potentially substitute in cases where other antifouling coatings cause chemical concerns.

Tea stain

Nic McPhee/CC BY-SA 2.0

The full article on the research, Colorless Multifunctional Coatings Inspired by Polyphenols Found in Tea, Chocolate, and Wine, published in Angewandte Chemie, can be viewed online without subscription.