Research Team Invents Small-Diameter Artificial Arteries
A patient needs a small-diameter bypass graft to replace a diseased blood vessel because of the progression of diabetes or the result of smoking.
Due to these chronic health issues, the patient’s veins can no longer be used for such a procedure. While large artificial arteries (10 to 15 millimeters in diameter) have been in use for about 50 years for replacing large blood vessels, development of a small-diameter artificial artery (less than 5 millimeters) has been unsuccessful due to rapid failure when implanted.
Martin Bide, a textile chemist at the University of Rhode Island, Matthew Phaneuf, president of BioSurfaces, Ashland, Mass., and Philip J. Brown of the School of Materials Science and Engineering at Clemson University, have developed a new way to synthesize such grafts from material made of polyester and collagen. A Phase I Small Business Innovative Research Grant (SBIR) from the National Heart, Lung and Blood Institute from the National Institutes of Health funded the research.
The trio said in its research summary that more than 500,000 peripheral bypass and coronary artery bypass grafts are implanted in the United States annually, so the potential annual market for a synthetic bypass graft could exceed $1.5 billion. Up until the team’s work, very little had changed with the technology related to artificial arteries since the mid-1950s, according to Phaneuf.
The polyester and collagen are electrospun into a mesh of ultra-fine fibers. Electrospinning uses electrostatic forces to distort a droplet of polymer solution into a fine filament to be deposited onto a surface. The process allows production of novel synthetic fibers of unusually small diameter and good mechanical properties. Other potential applications include wound dressing materials, artificial organs, and protective clothing. The researchers say the collagen allows the attachment of bioactive proteins that will promote healing and reduce clot formation.
Currently, no clinically available small (5 millimeter in diameter and smaller) vascular grafts can emulate the biological and physical properties of normal arteries. Implanted grafts of currently available materials fail because of clotting and stiffness as related to normal blood vessels. “A small vessel prosthesis (artery graft) that better emulates normal arterial walls would greatly improve the treatment of both peripheral vascular disease and coronary artery disease,” the researchers state in a summary of their research. “This is one of the applications it suits perfectly since conventional fiber extrusion technology is incapable of making such a material i.e., one that can combine proteins and synthetic materials together to form a composite small- scale device with all the right kind of properties,” Brown said.
The technology developed by Phaneuf, Brown and Bide is called “a nanofibrous biocomposite prosthetic vascular graft.” “The first choice for such a procedure is a patient’s own veins,” Bide said, “but when those veins have been damaged as a result of chronic illness, such as diabetes or those conditions related to smoking, then surgeons need an alternative.” “We employ the electrospinning process to create nanofibers with very large surface area for their weight,” Phaneuf said.
Bide said the collagen will be eliminated as the body’s own cells take up spaces in the artery or graft, thus reducing the potential for rejection. “We know through our early research that we can link proteins to the grafts and add anti-clotting treatments, as well as growth factors and other bioactive agents,” Bide said.
The next step for the three researchers, after successful completion of the Phase II SBIR studies, is to find a private company interested in licensing the product to allow for further research and eventual production for the market. “As a scientist, you always want to see an invention fully developed so that it can be used to help people,” Phaneuf said.