News Release

Study finds fiber found in blood clots
possesses extraordinary properties

CHAPEL HILL - A joint research project by pathologists, biochemists, and physicists at the University of North Carolina at Chapel Hill and Wake Forest University has found that the major protein in blood clots is remarkably strong and elastic.

Using novel tools developed by the physicists, Dr. Susan Lord, professor of pathology and laboratory medicine in the UNC School of Medicine, and Louise Jawerth, who was an undergraduate majoring in physics in UNC's College of Arts and Sciences at the time the work was performed, were able to stretch fibrin fibers farther than any other protein fibers. The fibers also proved to be very elastic; after stretching, they would bounce back to their original length.

These findings may have medical implications because they provide clues about the properties that determine whether a blood clot will withstand the flow of blood around it or break apart, which can lead to heart attack or stroke.

The study also pinpoints fibrin as a material that is lightweight and flexible but also strong.

The study is published in the Aug. 4 edition of the journal Science.

In addition to Lord and Jawerth, now a doctoral candidate in physics at Harvard University, Carolina authors of the study are Dr. Richard Superfine, professor of physics in the College of Arts and Sciences; and Dr. Mike Falvo, research assistant professor in the Curriculum in Applied and Materials Sciences, also in the College. Wake Forest authors are Dr. Martin Guthold, assistant professor of physics; Wenhua Liu and Eric Sparks, both graduate students in the physics department; and Roy Hantgan, associate professor of biochemistry.

Lord said it is surprising that the fibrin fibers can be stretched so far before they break, especially because they are made up of thousands of molecules. "What is it that's happening to the protein molecules - the individual units of the fibers - that allow them to stretch so much? There's no easy answer to that," she said.

Blood clots are made up of thousands of fibrin fibers bonded to blood cells called platelets. "We believe now that the fibers are probably the strongest and most elastic part of the clot, and that if the clot is going to fall apart, what would break would not be the fiber but rather the junctions between the fibers and the cells," Lord said.

Superfine pointed out fibrin's potential as a model material. "Nature uses proteins as building blocks for assembling this fiber, and that might tell us how we can use proteins to assemble materials that may have interesting mechanical properties," he said.

Further exploring fibrin's ability to stretch may help scientists design materials that could be used in, for instance, bulletproof vests. To explain, Superfine compared the properties of fibrin to that of a spider web.

"A fly comes in and hits the spider web, and the web absorbs the energy of the fly," he said. "The military is interested in materials like that because if a bullet comes at a soldier, you want a material to stop the bullet, so it needs to absorb a lot of energy. It might be that the fibrin fiber can help us design materials that can absorb a lot of energy."

The physicists combined atomic force microscopy with fluorescence microscopy to develop a technique to allow Lord, Jawerth and Guthold to view the fibers as they stretched them. With atomic force microscopy alone, they could view a fiber before and after they stretched it to the breaking point, but not during the stretching process.

The technology was developed by Superfine and colleagues at the Center for Computer Integrated Systems for Microscopy and Manipulation (CISMM), part of the Nanoscale Science Research Group. CISMM is funded at UNC by the National Institutes of Health and the National Institute of Biomedical Imaging and Bioengineering.

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Note: Lord can be reached at (919) 966-3548 or stl@med.unc.edu. Superfine can be reached at (919) 962-1185 or rsuper@physics.unc.edu.
School of Medicine contact: Les Lang, (919) 843-9687 or llang@med.unc.edu
College of Arts and Sciences contact: Dee Reid, (919) (919) 843-6339 or deereid@unc.edu
News Services contact: Clinton Colmenares, (919) 843-1991, clinton_colmenares@unc.edu