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How Shark Skin May Help Save Lives

Could a fearsome underwater creature hold the key to preventing deadly infections in humans? Yes. Shark skin has been found to repel bacterial growth.
Could a fearsome underwater creature hold the key to preventing deadly infections in humans? That question - which will be explored this week in the PBS "Nova" series, "Making Stuff" - is examined by our friend David Pogue of The New York Times:

If you're a news correspondent, there are a lot worse places to do your reporting than the Bahamas.

But I'm not here to play, much. I'm here to investigate a 400-million-year-old material that's about to change modern medicine.

To see this amazing material, I have to go underwater.

Scuba guide Christina Zenato conducts underwater nature hikes with an unforgettable feature - touching s shark.

"Yes, just nice, gentle strokes," she advises.

"Hey, I'm not just an American tourist here - I know how to touch a shark," Pogue says bravely.

Zenato says she's had people who bit her sharks. Oh no! That gives "man-eating shark" a whole new meaning.

Zenato has developed an astounding rapport with these reef sharks. She lures them to her spot with fish guts, then, by rubbing a female shark's nose in just the right way, she puts her into a sort of trance called tonic immobility.

And then, you can touch.

In those memorable 10 minutes, I learned two things about shark skin: First, it's spotless. No algae, no barnacles - nothing grows on a shark.

Second, it's smooth as rubber going toward the tail, but rough as sandpaper going the other way.

So is there some evolutionary purpose to that?

"Yes, absolutely," Zenato said. "What the shark skin has, it's what they're called dermal denticles. By trapping the water underneath of this little dermal denticles, it basically creates, like, a cushion where the shark can glide through the water much easier."

Hmmm. Special scales that let you go faster through water? Who might be interested in that technology?

In 2000, Speedo introduced a line of full-body bathing suits called FastSkin with simulated denticles all over it. In the 2008 Olympics, Michael Phelps wore a refined version of that suit, which Speedo claimed gave swimmers a speed advantage - and triggered a swimwear arms race.

The Olympics committee finally banned these high-tech suits.

But at the University of Florida, it's not the anti-turbulence qualities of shark skin that caught the attention of biomedical engineer Tony Brennan. He was more interested in the fact that nothing grows on a shark's skin - like barnacles and bacteria.

He was trying to help the Navy solve a huge, expensive problem: "Ships moving through the ocean tend to pick up marine organisms," Dr. Brennan said. "And when they get onto the side of the ship, it makes it more difficult for the ship to move through the water."

Dr. Brennan noticed that whales and manatees also collect gunk on their skin, but not sharks.

When he studied shark denticles under the electron microscope, he discovered why.

"I said, "Wow!, That shark pattern, I'd never seen it before,'" he said. And he believes that has something to do with no bacterial growth.

Brennan wondered if he could re-create the shark skin surface on plastic sheets.

"Sharks' denticles are set up like a diamond pattern," he said, showing Pogue a clear plastic sheet he called a Sharklet, which also had a diamond pattern. Its microscopic pattern of ridges mimics the denticles of shark skin.

And when you stick it on ships, sure enough - NOTHING GROWS.

But if there's a material that even bacteria won't stick to, there's an even bigger customer waiting for it: The healthcare industry.

Dr. Shravanthi Reddy, director of research for Sharklet, said the medical community has for a long time been focused on killing as much existing bacteria s possible.

"Now, the interesting thing about bacteria is that you can't kill them all," Dr. Reddy said. "You can kill 99 percent of them, but that 1 percent that you leave alive is the strongest 1 percent."

Already, there's one bacteria type, called MRSA, that is EXTREMELY resistant to almost all antibiotics. It kills more Americans than AIDS.

"We can't keep fighting that same traditional war; we kind of have to shift our thinking," said Dr. Reddy.

In other words, it might be better just to chase them away?

"Yeah, kind of convince them, 'Hey, you don't want to settle here,'" Dr. Reddy said.

In one test, she's going to see if Sharklet can repel bacteria the way shark skin repels algae and barnacles.

Two pieces of plastic - one smooth, one patterned with Sharklet - are subjected to bacteria and incubated for 24 hours.

The electron microscope reveals the astounding results. The plain plastic is covered with a bacteria film - "Just these big clumps of bacteria all piled up on one another," Dr. Reddy said.

And on the Sharklet surface? "You might see one or two cells, but you don't see that big clumping the way you see it on the smooth surface," said Dr. Reddy. "What's really interesting is that there are no chemical differences between the surfaces. It's the same material. No differences, other than the physical shape."

This material could be an answer to the enormous problem of secondary infections in hospitals, using it in places and objects that are constantly touched - bedside tables, door panels. "Those wristbands, have you ever seen anyone clean those wristbands?" said Dr. Reddy. "Never, right? And they're on the patient the whole time they're in the hospital."

We think of sharks as the ultimate predators. But if Sharklet really works, we may soon owe them our lives.

For more info:
•  "Nova: Making Stuff" (PBS)