ScienceDaily (Apr. 21, 2010) — A new study shows that when it comes to networks of protein fibers, individual fibers play a substantial role in effectively strengthening an entire network of fibers. The research, published by Cell Press in the April 20th issue of the Biophysical Journal, describes a mechanism that explains how individual fibrin fibers subjected to significant strain can respond by stiffening to resist stretch and helping to equitably distribute the strain load across the network.
"We know that network strength is determined in part by the maximum strain individual fibers can withstand, so it is of particular interest to determine how the high strain and failure characteristics of single fibrin fibers affect the overall strength of the network," says senior study author Dr. Michael R. Falvo from the Department of Physics and Astronomy at the University of North Carolina at Chapel Hill. "Further, determining how strain is shared among the constituent fiber segments in a network under imposed stress is crucial to understanding failure modes of networks and their strength."
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Volume 98, Issue 8, 21 April 2010, Pages 1632-1640
doi:10.1016/j.bpj.2009.12.4312 | How to Cite or Link Using DOI
Copyright © 2010 Biophysical Society Published by Elsevier Inc.
Nathan E. Hudson†, John R. Houser†, E. Timothy O'Brien III†, Russell M. Taylor II†, §, ¶, Richard Superfine†, Susan T. Lord‡ and Michael R. Falvo†, ,
† Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
‡ Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
§ Department of Computer Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
¶ Curriculum in Applied Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
Received 9 September 2009;
accepted 8 December 2009.
Editor: Denis Wirtz..
Available online 18 April 2010.
Abstract
As the structural backbone of blood clots, fibrin networks carry out the mechanical task of stemming blood flow at sites of vascular injury. These networks exhibit a rich set of remarkable mechanical properties, but a detailed picture relating the microscopic mechanics of the individual fibers to the overall network properties has not been fully developed. In particular, how the high strain and failure characteristics of single fibers affect the overall strength of the network is not known. Using a combined fluorescence/atomic force microscope nanomanipulation system, we stretched 2-D fibrin networks to the point of failure, while recording the strain of individual fibers. Our results were compared to a pair of model networks: one composed of linearly responding elements and a second of nonlinear, strain-stiffening elements. We find that strain-stiffening of the individual fibers is necessary to explain the pattern of strain propagation throughout the network that we observe in our experiments. Fiber strain-stiffening acts to distribute strain more equitably within the network, reduce strain maxima, and increase network strength. Along with its physiological implications, a detailed understanding of this strengthening mechanism may lead to new design strategies for engineered polymeric materials.
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