• Dec 16

One day, your sunscreen may be made from DNA

Wearing sunscreen can help you avoid sunburn and protect your skin cells from damage. But you need to reapply sunscreen after spending some time in the sun. A new finding could lead to another type of sunscreen that avoids that hassle. In fact, the longer you wore it, the better it would protect you from the sun’s harmful rays. The material behind this potential new sunblock: DNA.

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DNA is short for deoxyribonucleic acid. It’s the genetic blueprint inside cells that instructs them about what to do — and when. “DNA molecules can get damaged when exposed to sunlight,” notes Guy German. He’s a biomedical engineer at Binghamton University in New York. Instead of letting the sun damage the skin’s DNA, his group asked itself: Why not shield that DNA with some other type?

“Really cool science,” German says, often “starts with a simple conversation.” In this case, that discussion took place over coffee with a biochemist. This was Mark Lyles at the University of Rhode Island in Kingston. German had been thinking about how to use DNA as an ingredient in cosmetics. Lyles had lots of ideas.

One of them was to work with thin layers, or films, of DNA. Other people had already looked into using DNA films in electronics or in biological sensors, for instance. But no one had studied how such films might interact with light. That would be important to know when making products for skin. After all, people go out in the sun.

German’s team ordered some DNA from a company that supplies materials to labs. Those companies can provide DNA from various species. What they got just happened to be DNA from the sperm cells of male salmon, German explains.

His group mixed this DNA with water and some ethanol. That’s a type of alcohol sometimes used as a solvent (as it was here). The researchers then spread the mix onto a surface to dry. As the liquid evaporated, the DNA molecules arranged themselves into a thin film. They did this in much the way that drying paint leaves a film of colored pigment on a wall.

Next, the team shone light on the DNA films.

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They tested two broad spectra of the ultraviolet (UV) rays given off by the sun — UVA and UVB. You can’t see either type of this light because their wavelengths are too short for the human eye to detect. Still, UVA and UVB can damage DNA. And when that damage occurs in skin cells, it can lead to cancer.

The film made from the fishy DNA absorbed much of the UVA and UVB light, the team showed. That absorption would keep this light from reaching any skin cells that might have been below.

At first, “the films can block up to 90 percent of UVB wavelengths and up to 20 percent of UVA wavelengths,” German reports. But the longer that UV light shines on the films, the more UV light they can now block. In other words, the DNA shield seems to strengthen with use.

So far, the highest exposures tested are equal to the UV light that would come from about 25 straight days in the summer sun, German explains.

These researchers have some ideas about why their new sunscreen improves with use. One possibility: UV light creates more connections among the film’s DNA molecules. Another possibility: Sunlight changes the film’s individual DNA molecules in ways that let them absorb more light. It will take more work to find the answers.

German’s group is now looking into turning the DNA film into a product that could be sold as a sunscreen. They are also testing the film to see how water-resistant it would be. This would show how easily it could wash off in water or sweat — and need to be reapplied.

See-through bandages

The DNA film also might help create a new kind of wound covering. With such a “bandage,” German notes, “you could look straight through and see how the wound is healing.”

His group has started testing the DNA films on samples of human skin. They seem to attract moisture from the air. That could be good for skin, German says, because moisture helps skin grow new cells. It keeps existing skin healthy too.

Clara Piccirillo is a materials chemist in Italy at the Institute of Nanotechnology in Lecce. She, too, works on sunscreens, although not as part of German’s group. She finds it “fascinating” that exposure to UV light makes the new sunscreen absorb even better. She suspects such a sunblock would likely also be nontoxic, or at least generally safe for skin.

However, to protect skin the DNA has to be in the form of a film, Piccirillo notes. That’s different from many sunblock products today, whose active ingredients come mixed into lotions. Some of the materials in a lotion might stop DNA from forming the necessary film. That’s why she suspects lotions will not be the route to making useful DNA films.

Turning the DNA films into wound coverings appears more promising, she says. “The film can be applied on the wound and it will protect it from UV light.” And that light, she warns, “can be very dangerous for the healing skin.”

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