A Nonlinear Constitutive Model to Predict the Stress Strain Behavior of Small Intestinal Submucosa

Porcine small intestinal submucosa (SIS) is a bioactive resorbable extracellular matrix material (ECM) comprised mostly of collagen type I and containing the growth factors TGF-β and FGF-2. Current applications of this material consist of using SIS as a nonload-bearing device. However with its unique regenerative properties and nonlinear mechanical response, this material is a great choice for tendon or ligament replacement or repair. The development of this material to be used in a load-bearing application requires full understanding of its mechanical properties. A scaffold comprised of 20-layers of SIS sandwiched together was tested in a uniaxial tensile test. This test resulted in a nonlinearly elastic stress-strain response with a distinct toe-region, linear region, and strain to failure. To fully model this response, a nonlinear constitutive material model was developed using an exponential strain energy density function. As the ultimate tensile strength of this scaffold is lower than that of most tendons and ligaments, a polydiaxanone (PDS) mesh was incorporated into the 20-layer scaffold, which showed an increase in applied load with a decrease in ultimate tensile strength. In conclusion, a nonlinear constitutive model was developed to predict the nonlinear stress-strain response of a 20-layer multilaminate SIS scaffold which can serve as a building block to future development of a load-bearing bioresorbable scaffold.