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University Of Pittsburgh Researchers Develop Co-Polymer That Acts Like A Super Sunscreen To Prolong Life Of Antioxidants

PITTSBURGH, January 10, 2005 — University of Pittsburgh researchers have developed a way that could prolong the effectiveness of antioxidants that are commonly used in products to protect against the harmful effects caused by sun and air exposure. Reporting in the Jan. 10 print issue of Biomacromolecules, a journal of the American Chemical Society, they describe a chemically formulated co-polymer that in laboratory studies was able to withstand significantly longer periods of intense ultraviolet light than other formulations.

Antioxidants are added to many types of products, from sunscreens and cosmetics to exterior paints and industrial and consumer plastics, in order to stave off oxidation – a process whereby UV radiation or oxygen in air or water produces a chemical reaction to the surface of an object. Oxidation causes skin to burn or wrinkle, iron to rust and plastics to turn yellow or crack. Yet even the addition of antioxidants cannot provide complete protection. Eventually, the antioxidants themselves become vulnerable to oxidation caused by UV light, hence the need to reapply sunscreen, repaint homes and replace sun-damaged materials.

“We wanted to identify a way to stabilize antioxidants against the deleterious effects of photo-oxidation caused by the sun. This has been a major obstacle that has limited the effectiveness of antioxidants to protect materials against oxidation,” said Bhalchandra S. Lele, Ph.D., research associate at the University of Pittsburgh’s McGowan Institute for Regenerative Medicine and the department of bioengineering at the University of Pittsburgh School of Engineering.

Dr. Lele and principal author Alan J. Russell, Ph.D., professor of surgery at the University of Pittsburgh School of Medicine and director of the university’s McGowan Institute, developed a co-polymer that acts as a super sunscreen of sorts, whereby one chemical sacrificially takes the hit of UV rays to allow its partner, the antioxidant, to work longer. Specifically, the co-polymer consists of benzotriazole, a chemical that absorbs UV light, and an antioxidant called Trolox, a water-soluble derivative of vitamin E that has been shown to protect against the harmful effects of UV radiation.

“We have not simply combined these two compounds to create this unique co-polymer. In fact, when mixed, the end product is no more effective than each of the individual compounds. Rather, for these two chemical structures to be synergistically effective we found that the key components must reside in the same molecule,” explained Dr. Russell.

As a single chain molecule – with the two components side by side – benzotriazole preferentially receives the UV, thereby protecting the Trolox from exposure, in much the same way that a tall building takes the bright sun while casting a cool shadow on a house next door.

Dr. Russell began working on the creation of a co-polymer that was both protective of and protected against photo-oxidation as part of his lab’s primary focus to develop materials that can be used as coatings on buildings or vehicles that simultaneously detect and decontaminate chemical and biological agents. With funding from the U.S. Department of Defense Multidisciplinary University Research Initiative program administered by the Army Research Office, Dr. Russell has been seeking ways to couple the power of biological detection with light-activated decontamination. The only way to use both simultaneously was to invent a way to protect the biological component that is capable of detection and decontamination (nature’s catalyst) from the sun and other oxidants.

In their current study, the researchers created the laboratory equivalent of an extreme outside environment, subjecting an enzyme to eight hours of UV light roughly seven times the intensity of a blazing summer sun. Under these harsh conditions, an enzyme called chymotrypsin quickly lost its ability to function. The researchers then coated the enzyme with mixtures of UV-absorbing molecules and antioxidants. Only when the UV-absorbing and antioxidant molecules were placed in the same polymer chain could the enzyme survive for long periods.

“This surprising result implied that the UV-absorber could protect the antioxidant in the co-polymer. More detailed studies showed this to be true even without the enzyme, and as such, we found a unique way to stabilize antioxidants from their own oxidation. Now we can modify our decontaminating coatings so that they are less vulnerable to oxidative reactions from sun, and there very well could be additional applications in which protection of antioxidants is important,” said Dr. Russell.

The University of Pittsburgh has applied for a U.S. patent for the process involved in using a UV-absorber to stabilize an antioxidant.

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