Can a hi-tech plaster stop fatal blood clots that cause strokes and heart attacks? A new patch ‘turbocharges’ the body’s blood-thinning molecules, making its defences more effective

• Millions are already taking tablets containing heparin to reduce the risk of clots
• The new patch automatically injects the same drug through miniature needles
• This prevents patients from taking too much, which can cause fatal bleeding

Ahigh-tech skin patch could prevent deadly blood clots that cause strokes and heart attacks.

The patch detects when a clot is in danger of developing and automatically releases a blood thinner into the bloodstream in time to stop it.

It does this through micro-needles in the patch which gently pierce tiny blood vessels — called capillaries — just beneath the skin.

As blood passes by, the needles — each one not much thicker than a human hair — monitor levels of thrombin, a clotting agent which increases in the blood when it is becoming dangerously thick and prone to clotting.

If thrombin levels are abnormally high, tiny amounts of a drug called heparin are released to thin the blood and reduce the clotting risk.

Heparin works by ‘turbocharging’ the body’s own blood-thinning molecule, called antithrombin III, making it up to 2,000 times more effective.

Millions of people in Britain already take heparin tablets daily to reduce the risk of clots, or thrombosis.

Some are prescribed it because they have atrial fibrillation, an irregular heartbeat which can make blood pool inside the heart, increasing the chances of a clot breaking away and travelling to the brain — causing a stroke.

Others take the drug because they have already had a stroke and are at high risk of another.

Patients who have had major surgery — such as hip or knee replacement — are also put on short courses of heparin tablets or injections as immobility puts them at high risk of a clot because blood pools in their legs.

But those on drugs such as heparin need frequent blood tests to ensure they are getting exactly the right dose.

Too much medicine can cause potentially fatal bleeding, because blood is too thin to clot. Too little means they can still be in danger of a potentially lethal clot.

The postage stamp-sized patch, developed at North Carolina State University, keeps a round-the-clock check on thrombin levels and so does away with the need for repeated blood tests.

On one side it is covered in more than 100 miniature plastic needles. These are covered in a coating containing liquid heparin and a special chemical containing amino acids that binds the drug to the surface of the needles.

When thrombin levels are elavated, a chemical reaction takes place within the amino acid coating — and releases heparin into the blood. So far, the disposable patch, which can be changed daily, has only been tested on mice.

Scientists injected them with large amounts of thrombin — enough to cause a fatal blood clot — after giving them a patch or a heparin jab.

The results, published last month in the journal Advanced Materials, showed all the mice with the patch survived but 80 per cent of those on a heparin injection died from the results of a clot.

Researchers said early results suggest the patch is faster and more effective than injecting the drug, or taking it orally. The team now plan to run studies testing the patch on patients.

Professor Martin Cowie, a professor of cardiology at Imperial College London, says the smart patch could improve anticoagulation for patients at risk of clots.

‘The concept of a self-regulating patch that tailors the release of a drug as needed into the body is very innovative. It’s well worth pursuing,’ he adds.

Professor Jeremy Pearson, an associate medical director at the British Heart Foundation, believes that the patch is ‘an ingenious approach’.

‘It may have advantages over current treatment which requires repeated injections of heparin,’ he says. ‘The initial results in mice show promise. It will be interesting to see whether these can be reproduced in human studies.’