Simulating fibrin clot mechanics using finite element methods

Blood clots inside blood vessels impede blood flow and can lead to blockage. Injection of thrombolytic agents affects the body systemically and may lead to hemorrhage. Risk is reduced with sonothrombolysis—high-amplitude pulsed ultrasound that drives micron-sized bubbles into violent oscillations, destroying the fibrin mesh of a clot. To gain insight into the 3D structure and mechanical behavior of fibrin clots, we fabricated a clot from purified fibrinogen, imaged it using a confocal microscope and 3D printed a plastic model of the image. Coordinates of fibrin connection points were entered into ANSYS, the clot finite-element-simulated for nodal displacements, and the bulk Young's modulus of the clot calculated. Simulations suggested that the elastic moduli in the three orthogonal directions were Ex = 113.5 Pa, Ey = 109.1 Pa, and Ez = 16.17 Pa. The close agreement between Ex and Ey supported the assumption of isotropy in a fibrin clot. The deviation of Ez from Ex and Ey could be attributed to the presence of the glass coverslip affecting the clot structure. Overall, results showed that confocal microscopy and simulations in ANSYS are useful in modeling clot structure and mechanics. Our next step is to simulate bubble activity inside the virtual clot.