Fizzy bubbles carry drugs deep into wounds

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Alka-Seltzer’s frothy fizz may hold the secret to stopping blood loss. 

Jets of rushing bubbles can carry blood-clotting drugs deep into a wound and seal it shut, scientists report October 2 in Science Advances.

The work is the first to show bubble-powered devices doing something useful inside the body, says organic chemist Jan van Hest of Radboud University in Nijmegen, the Netherlands. “What they’ve done is really clever because it has a biomedically relevant application — it can stop blood flow,” he says.

The bubble-propelled drugs could come in handy in a car accident, in postpartum hemorrhaging or even on the battlefield, says study coauthor Christian Kastrup of the University of British Colombia in Vancouver.

For small injuries, blood can clot, turning into a gel that glues damaged tissue together. But blood can’t plug large wounds on its own, Kastrup says. “You have to come up with ways to get in there and help the blood clot.”

One way is to treat wounds with drugs. But it’s not easy to deliver drugs deep into a wound, upstream against flowing blood.

Scientists have devised all sorts of ideas for high-tech drug-delivery gizmos that could travel throughout the body. Some rely on particles guided by magnetic fields; others are propelled by ultrasonic waves. Ideally these microscopic drug packets would propel themselves, says Penn State chemist Ayusman Sen.

Kastrup and colleagues found a way to do just that. They created a kind of chemical powder keg loaded with blood-clotting drugs. When the keg touches a wound, it triggers tiny explosions. These explosions release bubbles of carbon dioxide gas that blast the drugs in all directions — including into damaged tissues.

“It’s the ‘plop, plop, fizz, fizz’ mechanism,” Kastrup says. And it seems to do the trick in injured mice and pigs.

Kastrup and colleagues snipped off the tips of nine mice’s tails and sprinkled on a powdered blend of calcium carbonate (the active ingredient in some antacids), an organic acid and a blood-clotting drug called thrombin. Seven of nine mice stopped bleeding within 10 minutes. When the team repeated the experiment using only the blood-clotting drug to treat the wound (and no propulsive bubbles), only three of nine mice stopped bleeding.

Next, the researchers tested the powder’s power against an even graver injury. They surgically punched a hole about the size of a pencil eraser in the femoral arteries of pigs. With no treatment, the pigs bled out and died within three hours. But all of the pigs treated with the self-propelled drug survived. 

“In an emergency, it would be nice to have this powder in a first aid kit,” van Hest says. “Even if you’re not an expert medic, you could put the powder on a wound to make it stop bleeding.”

Sen agrees that the particles are a nice way to deliver drugs, but says they’d be even more effective if they all zeroed in on the wound. “The particles are going every which way,” he says. “In the future, you need something that’s better directed.”