Smart Patch Delivers Anticoagulants in Response to Blood Thrombin Levels

Patients with thrombosis – a condition which makes a person more prone to blood clots – must regularly monitor their blood and administer anticoagulant drugs, when needed. Now, researchers at North Carolina State University (NC State) and the University of North Carolina (UNC) at Chapel Hill, have developed a smart sensing patch which can automatically release blood thinners – such as heparin – in response to rising blood clotting factor levels.

Blood clots in the body can cause dangerous health conditions such as heart attack, stroke or a pulmonary embolism. While heparin is an effective blood thinner, the dosing must be optimized to prevent patients from spontaneous hemorrhaging.

“Our goal was to generate a patch that can monitor a patient’s blood and release additional drugs when necessary; effectively, a self-regulating system,” said Zhen Gu, associate professor in the joint biomedical engineering program at NC State and UNC, and co-corresponding author on a paper describing the work. The research was published in the journal, Advanced Material.

The patch consists of polymer microneedles impregnated with hyaluronic acid (HA) and heparin. The smart patch is sensitive to levels of thrombin, which activates the clotting response in the blood. When the polymer patch senses elevated thrombin levels in the blood, the enzyme signals the release of heparin into the bloodstream.

“The more thrombin there is in the bloodstream, the more heparin is needed to reduce clotting,” said Yuqi Zhang, a Ph.D. student in Gu’s lab and one of the lead authors on the publication. “So we created a disposable patch in which the more thrombin there is in the blood stream, the more heparin is released.”

So far, the patch has only been tested in a mouse model where the animals were injected with a fatal dose of thrombin. To compare the patch’s effectiveness with a heparin shot, the mice were assigned to one of three groups: heparin injection, heparin smart patch or no treatment. Only those mice who received no treatment died as a result of blood clotting in the lungs after the thrombin injection.

The surviving mice were then re-injected with another dose of thrombin six hours after receiving treatment. At 15 minutes post-thrombin injection, 80 percent of the mice that received a heparin shot alone had died, while all of the mice with the heparin patch were stable.

“We’re excited about the possibility of using a closed-loop, self-regulating smart patch to help treat a condition that affects thousands of people every year, while hopefully also driving down treatment costs,” said Gu. “This paper represents a good first step, and we’re now looking for funding to perform additional preclinical testing.”