Fibrin Fiber Formation and Mechanics

February 10, 2017

Christine Helms, Department of Physics, University of Richmond

Fibrin fibers are a major constituent of blood clots.  They perform the mechanical task of stemming the flow of blood. The structure and strength of fibrin fibers relates to the medical outcome of an individual.  Therefore, we measure the structure of fibrin clots and strength of individual fibrin fibers to understand better the mechanism(s) leading to poor clinical outcomes.   Previous research showed that environmental factors, such as pH and ion concentration, affect clot structure and fiber diameter.  Recently we added to that body of work by showing that high concentrations of nitric oxide also affect clot structure through the oxidation of important proteins. Conditions with altered clot structure often have an altered rate of fiber formation, altered fiber diameter and altered clinical responses, as well. This leads to the question, what is the mechanism responsible for the change?  If we could understand the individual fibers, we may understand why changes to the clot are associated with heart attack and stroke.  Therefore, we measured the modulus of an individual fibrin fiber using the atomic force microscope. Fibrin fibers have interesting mechanical properties from a materials standpoint because they form a regular structure but are extremely extensible.  In addition, we found that the modulus of fibrin fibers is dependent on the diameter of the fiber, suggesting irregular density inside the individual fibers.   In this talk, I will discuss the role of fibrin in health and try to convince you that the mechanism responsible for altered clot structure and stiffness is packing of the monomers inside the individual fibers.  I will do this through the presentation of our recent data on the modulus of fibrin fibers.