Materials

Ancient Bacteria's Natural Sun-Blocking Molecules Could Work as Sunscreen

Cyanobacteria relies on the sun for energy and as a result, has developed unique ways to protect itself from harmful radiation.

With sunscreens, you're damned if you do and damned if you don't. Apply some to your skin and the synthetic compounds inside could irritate it or mimic estrogen, which can disrupt the body's normal hormonal cycle, or, if the sunscreen contains nanoparticles, it could be toxic to your cells or toxic to the environment. Don't apply it and the sun's ultraviolet radiation could damage your cells and even cause cancer.

But a natural product made from microorganisms called cyanobacteria could represent a better alternative. In the latest issue of the European Journal of Phycology, scientists from the University of Isfahan in Iran, and Swansea University in the UK, compared synthetic sunscreen substances to the natural ones produced by these tiny organisms and make the case that cyanobacteria could produce sustainable and safer sunscreens and moisturizers.

"A study in the UK revealed that over the course of a year, 23 percent of women and 13.8 percent of men experience some kind of adverse reactions to personal care products," the researchers write.

Cyanobacteria have been around for eons and exist everywhere, on both land and sea. They're probably best known as the blue-green scum that can grow on the surface of ponds. Although they are not algae, these single-celled organisms do rely on sunlight to drive photosynthesis for the fuel they need to survive - and it's this ability, to thrive on sunlight, that has scientists interested in using the organisms for sunscreen.

As cyanobacteria absorb sunlight, they produce molecules called mycosporine and scytonemins as well as mycosporine-like amino acids (MMAs) that shield against long-wave and short-wave ultraviolet radiation.

The idea is cultivate cyanobacteria in giant bioreactors under ideal conditions, harvest the molecules and put them into a liquid or gel that could be smoothed on the skin.

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The scientists also looked at how cyanobacteria survive in extreme conditions, such as the acid pools in Yellowstone National Park or in the extreme heat of Death Valley as well as the extreme cold of Antarctica. So-called extremophilic cyanobacteria produce MMAs that boost a cell's ability to tolerate water loss, heat and excess salt.

They also produce a protective sheath made, essentially, of large chains of sugar molecules, also called polysaccharides.

"External polysaccharide layers act as water/moisture absorbers and are potent candidates to be used as moisturizers in skin products," the researchers write.

The MMAs also stabilize highly reactive free radicals, which can damage DNA and other cellular structures.

The researchers say that lotions derived from cyanobacteria appear to be much more effective at retaining moisture in the skin than those made from conventional substances, such as urea, glycerin and propylene glycol.

Growing cyanobacteria won't add agricultural stress to the environment, either. They can be cultivated in tubes in a closed system and require mainly sunlight. The challenge is scaling up these biotech factories to meet demand.

Caption: Photosynthetic microorganisms thrive in this photobioreactor at Swansea University's Center for Sustainable Aquatic Research.

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