UAB-developed smooth vascular grafts and stent linings show promise for less clogging

Vinoy Thomas
Dr. Vinoy Thomas is looking for industry partners to further commercially manufacture the vascular graft.

A small caliber vascular dialysis graft with smoother surfaces that was developed at The University of Alabama at Birmingham (UAB) using gaseous plasma, and UAB’s development of a process for creating smoother linings in metallic stents, promise less clogs and better medical results for vascular dialysis graft patients and those requiring vascular stents.

UAB’s gaseous plasma modification process allows blood and other fluids to flow better with markedly less chance of clotting in Phase 1 testing of the hemodialysis/dialysis graft.

“We are currently looking for partners from industry to further commercially manufacture it,” says developer Dr. Vinoy Thomas, associate professor and director of graduate programs for Materials Science & Engineering at UAB’s Department of Mechanical and Materials Engineering.

“I hope this research one day helps the Alabama people and impacts the state’s economy,” he says.

grant support

The research is supported by funds from the $20 million National Science Foundation (NSF)-funded Future Technologies & enabling Plasma Processes (FTPP) grant, as well as funds from the Alabama Department of Economic and Community Affairs and the Alabama Department of Commerce.

FTPP is an Alabama coalition of nine universities and a research corporation that is managed at The University of Alabama in Huntsville (UAH). It aims to transition plasma research into medical, agricultural, manufacturing, space science, space weather prediction and other applications, establishing Alabama as a Southeastern regional hub for plasma science expertise and creating thousands of high-paying technical careers in the state and region.

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UAB scientists are currently in Phase 2 of the graft’s development, Dr. Thomas says.

“There is an unmet need for a small caliber artificial vascular graft, both as a bypass graft and for use as an access graft for hemodialysis,” he says.

The graft has been in development since 2008, when the project received a Phase 1 National Institutes of Health Small Business Technology Transfer grant to develop a hybrid nano matrix graft with gradient functionalities for bypass applications.

At that time, a seamless tubular geometry was developed for the graft using enabling nano spinning technology, but in longer lengths it tended to kink.

“Later, we combined additive manufacturing and nano-spinning to fabricate a kink resistant graft,” Dr. Thomas says. Fabrication of the graft and in vitro evaluation of its mechanical properties and surface coating methods were achieved with the help of NSF funding.

Dialysis graft development has involved characterization work by physicist Dr. Paul Baker of UAB’s Department of Physics and animal implantation work by Dr. Timmy Lee, UAB professor of medicine in the Department of Medicine and Division of Nephrology.

plasma modification

“Plasma, the fourth state of matter, is useful to modify our graft for better biological performance,” says Dr. Thomas. “The plasma we use is called low temperature nonequilibrium plasma, which can create organic and inorganic functionalities without affecting the bulk mechanical and structural properties.”

Plasma modification of the graft materials improved the blood compatibility and cellular performance needed to have a clot-resistant graft during in vitro studies. The results were published as an article in Journal of Materials Chemistry.

“Now, with funding from the Alabama Department of Commerce, we study the in vivo performance of the access graft in a pig model to evaluate its efficacy,” Dr. Thomas says.

The graft is stable and kink-resistant, and it has nanofeatures while mimicking the shape, structure and mechanics of a natural blood vessel.

In separate research, Dr. Thomas’ team has developed what they call a flexi-coat technology that can fuse the plasma polymerized lining onto metallic stents to improve blood compatibility.

“We are further continuing our developmental studies in that aspect with a second funding from the Alabama Department of Commerce,” he says.

The graft project benefited since inception from advice and suggestions by Dr. Yogesh Vohra, professor and university scholar in UAB’s Department of Physics, Dr. Thomas says.

staff and resources

NSF EPSCoR Track 1 programs have funded three doctoral students and one postdoctoral researcher for the projects so far. Former students who worked on the project for their doctoral dissertations include Dr. Bernabe Tucker, a materials science major and currently the senior scientist at Evonik, and Dr. Kiran Adhikari, a physics major and currently an engineer at Intel.

The FTPP grant enabled collaboration with experts in plasma physics and plasma diagnostics, as well as applied scientists and engineers, to broaden research perspectives.

“Sharing of the resources and facilities was made possible by the FTPP grant,” says Dr. Thomas.

Funds to understand the physics, characteristics and use of low temperature plasma came through an earlier $20 million NSF grant called Connecting the Plasma Universe to Plasma Technology in Alabama (CPU2AL). The current FTPP grant has funded work to shed light on the use of cold plasma technology for modification of grafts.

“We have gone a lot further in not only functionalizing the surface but also synthesizing anchored nanoparticles of interest – like gold and silver, etc. – for 3D printed polymer surfaces, too,” Dr. Thomas says. “We call it the Plasma Electroless Reduction process and have published an article about it in ACS Applied Materials and Interfaces.”

Others on Dr. Thomas’ team who have been involved in plasma and materials research include Dr. Vineeth Vijayan, who was a postdoctoral researcher and is now employed as assistant professor at Alabama State University; Dr. Gerardo Hernandez Moreno, who was a doctoral student and is now employed at Southern Research as a project manager; Rakesh Pemmada, a current graduate student with FTPP funding; Chandrima Karthik, Renjith Pillai, Kim Jones, James Hammon and John Bradford, all of whom are current graduate students on the team; and several undergraduate and K-12 students.