Clot-busting skin patch keeps the blood flowing with microneedles

An illustration showing how the microneedles dissolve in the presence of thrombin to release their clot-busting payloads(Credit: Yuqi Zhang)

According to the Centers for Disease Control and Prevention, every year 60,000-100,000 people die in the US alone from blood clots formed from conditions known as deep vein thrombosis or pulmonary embolisms, with 10 to 30 percent of them dying within the first month of diagnosis. Clots form when proteins in plasma and platelets thicken causing a mass. They can sometimes appear spontaneously, but are often the result of injuries or surgeries. Now, a new patch developed by researchers in North Carolina could help battle these life-threateners in a novel way.

The square patch has a series microneedles hanging from its underside. Each needle consists of the peptide hyaluronic acid (HA) and the drug Heparin. HA is a substance found in the human body, particularly in the eyes and joints, and is often applied as a cream to the skin as a moisturizer or for healing wounds. Heparin is a blood thinner, or anticoagulant, used to prevent blood clots.

The needles are designed in a such a way that when a blood-clot-causing enzyme called thrombin is elevated in the blood, they break down and release Heparin into the body.

"The more thrombin there is in the bloodstream, the more Heparin is needed to reduce clotting," says Yuqi Zhang, co-lead author of a paper about the research. "So we created a disposable patch in which the more thrombin there is in the bloodstream, the more Heparin is released."

To test out their invention, the researchers – from North Carolina State University and the University of North Carolina at Chapel Hill – injected mice with either a shot of Heparin or the new patch. Six hours after that, they were injected with clot-causing thrombin. Fifteen minutes after that, 80 percent of the mice that got the shot were dead, while all of those who were given the patch were still alive.

"We will further enhance the loading amount of drug in the patch," said Jicheng Yu, the other co-lead author of the paper. "The amount of Heparin in a patch can be tailored to a patient's specific needs and replaced daily, or less often, as needed."

The research team is now looking for funding to continue with pre-clinical trials of the patch.

Their work has been detailed in a paper published November 25 in the journal Advanced Materials.

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