title: The mechanical properties of single fibrin fibers.
abstract: BACKGROUND
  Blood clots perform the mechanical task of stemming the flow of blood.
  
  
  OBJECTIVE
  To advance understanding and realistic modeling of blood clot behavior we determined the mechanical properties of the major structural component of blood clots, fibrin fibers.
  
  
  METHODS
  We used a combined atomic force microscopy (AFM)/fluorescence microscopy technique to determine key mechanical properties of single crosslinked and uncrosslinked fibrin fibers.
  
  
  CONCLUSIONS
  Overall, full crosslinking renders fibers less extensible, stiffer, and less elastic than their uncrosslinked counterparts. All fibers showed stress relaxation behavior (time-dependent weakening) with a fast and a slow relaxation time, 2 and 52 s. In detail, crosslinked and uncrosslinked fibrin fibers can be stretched to 2.5 and 3.3 times their original length before rupturing. Crosslinking increased the stiffness of fibers by a factor of 2, as the total elastic modulus, E(0), increased from 3.9 to 8.0 MPa and the relaxed, elastic modulus, E(infinity), increased from 1.9 to 4.0 MPa upon crosslinking. Moreover, fibers stiffened with increasing strain (strain hardening), as E(0) increased by a factor of 1.9 (crosslinked) and 3.0 (uncrosslinked) at strains epsilon > 110%. At low strains, the portion of dissipated energy per stretch cycle was small (< 10%) for uncrosslinked fibers, but significant (approximately 40%) for crosslinked fibers. At strains > 100%, all fiber types dissipated about 70% of the input energy. We propose a molecular model to explain our data. Our single fiber data can now also be used to construct a realistic, mechanical model of a fibrin network.
authors.affiliation: Department of Physics, Wake Forest University, Winston-Salem, NC 27109, USA.
authors.forename: W
authors.initials: W
authors.lastname: Liu
authors.forename: C R
authors.initials: CR
authors.lastname: Carlisle
authors.forename: E A
authors.initials: EA
authors.lastname: Sparks
authors.forename: M
authors.initials: M
authors.lastname: Guthold
mesh_terms: D001696:Biomechanical Phenomena; D005337:Fibrin / Q000502:physiology*; D006801:Humans; D018625:Microscopy, Atomic Force; D008856:Microscopy, Fluorescence
chemical_list: D005337:Fibrin