When a clot blocks a blood vessel in the heart, a heart attack is the unfortunate result. Frequently, surgery is required in order to remove that clot. Thanks to an experimental new drug-delivery system, however, that approach may become increasingly unnecessary.

Developed by scientists from North Carolina State University and the University of North Carolina at Chapel Hill, the system incorporates porous hydrogel nanospheres.

Measuring about 250 nanometers in diameter, each sphere contains a drug/protein known as Y-27632 at its core, which is surrounded by a layer of another drug called tPA (tissue plasminogen activator). On the outside of each sphere is a coating of proteins that bind specifically to fibrin, a protein which is a key component of blood clots.

When injected into a vein, the nanospheres flow freely through the patient's bloodstream until encountering a clot, which they stick to. The tPA then proceeds to leak out, breaking down the fibrin and thus dissolving the clot.

This is followed by the release of the Y-27632, which helps protect the surrounding tissue from reperfusion injury – this condition occurs when fresh blood is suddenly reintroduced to tissues that had previously been deprived of it (such as by a clot), and it can cause scarring and stiffening of cardiac tissue.

In in vitro lab tests, the tPA/Y-27632 combo was found to dissolve blood clots within a matter of minutes. Additionally, when the nanospheres were tested on rats that had suffered heart attacks, they were highly effective at reducing scarring and preserving heart function. It's also noteworthy that the spheres weren't found in other parts of the animals' bodies, where the drugs carried by them could cause adverse reactions.

"Our approach would allow health-care providers to begin treating heart attacks before a patient reaches a surgical suite, hopefully improving patient outcomes," says assistant professor Ashley Brown, corresponding author of a paper on the research. "And because we are able to target the blockage, we are able to use powerful drugs that may pose threats to other parts of the body; the targeting reduces the risk of unintended harms."

The paper was recently published in the journal ACS Nano. Trials on larger animals are now being planned.