The Mechanical Properties of Modified Fibrin Fibers: Blocking the B-b Knob-Pocket Interaction

Abstract

Fibrin clot formation has been studied to determine the mechanical properties of fibrin fibers modified by blocking the B-b knob-pocket interaction. Synthetic B-knob peptides AHRPYAAC or AHRPYAAC-Peg have been added to a fibrinogen solution to allow for binding to the b-pockets prior to clot formation. After fibrin clot formation, a combined atomic force microscopic (AFM)/optical microscopic technique was used to study the properties of individual fibrin fibers in buffer. Mechanical testing of fibers was done using the AFM to laterally stretch individual fibers suspended over 13.5μm wide groves in a transparent substrate. The optical microscope, located below the sample, was used to monitor the stretching process. We found that the density and lateral aggregation of fibers was hindered by blocking the b-pockets with the synthetic B-knobs. Fibrin fibers modified with the synthetic peptide AHRPYAAC-Peg were found to stretch to 2.27 times their original length before rupturing compared to unmodified fibrin fibers which were found to stretch to 2.47 times their original length. From these results it is expected that synthetic B-knob concentration impacts the mechanical properties of modified fibrin fibers. The binding constants for AHRPYAAC were found to be 30.3 μM and 80.1 μM while the binding constants for AHRPYAAC-Peg were found to be 1.75 mM and 57.2 μM.