Could Nanotechnology Innovation Reduce Blood Clotting and Infections From Implants?

McMaster researchers develop surface coating that repels bacteria, viruses, and living cells.

Researchers at McMaster University have developed a nanotechnology surface coating that repels bacteria, viruses, and living cells, an innovation that could hold promise to reduce the risk of infection or blood clotting from implants, such as grafts, replacement heart valves, and artificial joints. While the engineered surface repels everything, it can be modified to permit beneficial exceptions, enabling implants to bond to the body, for example.

The research was reported in the October 24 issue of the journal, ACS Nano.

To understand the challenges related to making successful implants, researchers collaborated with Jeffrey Weitz, MD, professor of medicine, biochemistry and biomedical sciences at McMaster University, and executive director of the Thrombosis and Atherosclerosis Research Institute.

'Enormous' Implications
 

The implications could be "enormous," says Weitz. "We've made so many advances in these devices, but clotting on these devices is still a huge problem. One of the last frontiers is how to improve hemocompatibility—compatibility of the device with the blood in which it is sitting. The materials are getting better, but despite advances in material science, we still have a problem."

Coating the surface of these device and making them slippery to prevent clotting is the first step, Weitz says. The next step is to "add something that then attracts the endothelial cells so that they get the same lining that normal blood vessels have."

Weitz also sees opportunities to use the coating on central venous catheters, as well as the grafts he uses to treat peripheral artery disease. "It really does have the potential to save limbs in someone who has peripheral artery disease. This could be a huge advance."

The next phase of research to develop clinical applications is underway. Weitz says it may be five years before a clinically viable solution is available.

“It was a huge achievement to have completely repellent surfaces, but to maximize the benefits of such surfaces, we needed to create a selective door that would allow beneficial elements to bond with those surfaces,” explained Tohid DIdar, PhD, assistant professor of McMaster’s Department of Mechanical Engineering and School of Biomedical Engineering, in a news release.

Didar is the senior author of the ACS Nano journal article, which indicated "…this straightforward and simple method creates biofunctional, nonsticky surfaces that can be used to optimize the performance of devices such as biomedical implants, extracorporeal circuits, and biosensors."

Applied to a synthetic heart valve, the repellent coating could prevent blood cells from sticking and forming clots.

“A coating that repels blood cells could potentially eliminate the need for medicines such as warfarin that are used after implants to cut the risk of clots,” said co-author Sara M. Imani, a McMaster biomedical engineering doctoral student, in the news release.

Repels and Attracts
 

A completely repellent coating, however, would also prevent the body from integrating the new valve into the tissue of the heart itself. By designing the surface to permit adhesion only with heart tissue cells, the researchers make it possible for the body to integrate the new valve naturally, avoiding the complications of rejection. The same would be true for other implants, they say, such as artificial joints and stents used to open blood vessels.

"The research adds significant utility to completely repellent surfaces that have existed since 2011," according to the release. "Those surface coatings are useful for waterproofing phones and windshields, and repelling bacteria from food-preparation areas, for example, but have offered limited utility in medical applications where specific beneficial binding is required."

The novel surfaces created through the latest research promote targeted binding of desired species, while simultaneously preventing nonspecific adhesion, according to the study.

Researchers speculate the new nanotechnology also may have additional medical applications. Outside the body, selectively designed repellent surfaces could make diagnostic tests much more accurate by allowing only the particular target of a test—a virus, bacterium or cancer cell, for example—to stick to the biosensor that is looking for it, a critical advantage given the challenges of testing in complex fluids, such as blood and urine.