Biomechanical study of the elastic and viscoelastic behavior of extracellular matrix

Extracellular matrix (ECM) in blood vessels plays a significant role in modifying the mechanical behavior of these dynamic soft tissues. They have extremely complex hierarchical three-dimensional structure and there exists a tremendous interdependence of ECM compositional, structural, and mechanical properties. Many cardiovascular disease conditions involve significant biological remodeling of ECM. The overall research goal of this dissertation is to advance the current understanding of ECM mechanics from a fundamental mechanics perspective coupled with critical biophysical input. Our recent work on aortic elastin mechanics and decellularized ECM will be presented.;Elastin fibers are one of the major ECM components that endow blood vessels critical mechanical properties such as flexibility and elasticity. They are essential to accommodate deformations encountered during physiological function of arteries, which undergo repeated cycles of extension and recoil. Elastin is remarkably long lived, and it can suffer from cumulative effects of exposure to chemical damage. End products or side chain modifications from elastin --- lipid interactions and glycation compromise the mechanical properties of elastin by altering elastin's mobility. The mechanical properties of elastin are closely related to its microstructure and the external mechanical and immediate biochemical environment.;The elastic and viscoelastic properties of elastin under biaxial tensile loading were studied. The orthotropic hyperelasticity of elastin was well captured by a statistical mechanics based microstructural constitutive model. A quasi-linear viscoelasticity model was incorporated into the constitutive model at the fiber level to simulate its tissue level time-dependent behavior. The structural and functional changes of elastin due to in vitro elastin -- lipid interactions and glycation were studied by mechanical testing and microspectroscopy.;This study innovatively integrates rigorous experimental techniques and constitutive modeling to explore the macroscopic elastic and viscoelastic behaviors of aortic elastin, and correlate these behaviors to its fiber-level viscoelasticity, molecular structure, and biochemical environments. The coupled experimental and modeling approach establishes a solid foundation to investigate the mechanisms of changes in elastin mechanics and its role in the functionality of vasculature. The statistical mechanics based microstructural model has the potential to advance the development of predictive models on elastin degradation and disease progression.