Fibrin fibers have extraordinary extensibility and elasticity

Abstract

Blood clots perform an essential mechanical task, yet the mechanical behavior of fibrin fibers, which form the structural framework of a clot, is largely unknown. By using combined atomic force-fluorescence microscopy, we determined the elastic limit and extensibility of individual fibers. Fibrin fibers can be strained 180% (2.8-fold extension) without sustaining permanent lengthening, and they can be strained up to 525% (average 330%) before rupturing. This is the largest extensibility observed for protein fibers. The data imply that fibrin monomers must be able to undergo sizeable, reversible structural changes and that deformations in clots can be accommodated by individual fiber stretching.

Fig. 1

(A to D) Extensibility. A fiber suspended between two ridges (brighter horizontal bands) is stretched with the AFM tip (white dot) until rupture. The AFM cantilever appears as a dark, 35-μm-wide rectangle. The lower and upper segments of the fiber break at 183% strain and 278% strain, respectively. (E to H) Elastic deformation. A fiber was strained 80%, from which it snapped back to its original length. (I to K) Permanent deformation. The same fiber was strained to 230% (J), suffering some permanent lengthening (K). (L) Representative clot used for fiber manipulations.