How nano roughness could smooth out clotting risks

When doctors and medical technicians place a device in the human body, any number of things can go wrong. Ensuring the materials used in those devices interact appropriately and safely with human tissue is a key component to positive long-term health outcomes. 

Ketul Popat, chair of the George Mason University Department of Bioengineering and a medical materials expert, has a grant from the National Institutes of Health for approximately $200,000 to address an unintended consequence of device implementation—blood clots.

As many as 6% of the more-than one million Americans who have a stent or heart valve implanted each year face a risk of thrombosis, a potentially deadly condition occurring when a clot blocks a blood vessel. For Popat and his collaborators, it’s not just about what the material is made of, but the nature of the very surface of the material. 

But Popat said, “Sometimes we just put materials in the body because they work, knowing they are going to fail in several years and we’ll replace them. So it becomes really important to design the surface of the material of an implant so that when it is in contact with tissue, it is not a mismatch to the structural features of the tissue.” 

Our blood’s ability to clot is generally a welcomed response, preventing excessive bleeding following an injury and helping to start and speed the healing process. Of course, this characteristic can also be problematic, resulting in clots that can lead to strokes, heart attacks, and other dangers.

Popat believes a way to decrease clotting that may occur because of the devices is with surface manipulation, tricking the blood cells, in a sense. “Rough surfaces have different clotting properties than smooth surfaces. Now if we can create rough surfaces that are systematic and repeatable, the cells in the blood will sense these nano features and perform their function differently than if they move past a flat surface.” Popat says he and colleagues believe the nano rough surfaces work well at reducing blood clots because blood cells are used to it–surfaces of the blood vessels they flow through have a similar nanostructure. 

In addition to manipulating the surface material, the researchers are coating them with a substance tanfloc, a condensed tannin that is typically used for water purification. Previous studies show that the combination of these techniques–rough nanosurfaces covered in tanfloc–reduces the likelihood of blood clots. 

The unpredictability of clotting makes this research particularly important, especially in a world where approximately 20 million people die every year due to cardiovascular disease.   

“Some people get a stent, and they are fine for the rest of their lives, and some people get a stent and in the first few years they experience blood clotting. It’s very patient-specific, and unfortunately you just don’t know until you put it in,” Popat said. 

Popat said the goal goes beyond simply preventing the clots. “Eventually, we want the cells around the stent to grow on top of the stent and over it. We don’t just want to control clotting, but we also want the stent to truly integrate with, and become part of, the body.”