Fiber Kinematics of Small Intestinal Submucosa Subjected to Biaxial Stretch

Small intestinal submucosa (SIS) of the porcine has been used extensively over the past decade for repair of a variety of connective tissues, and is now being considered for functional tissue engineering applications. Thus, it is important to consider the kinematics of its fibers. The current study investigated the fiber kinematics of SIS in response to multiple stretch patterns using a modified version of a biaxial stretching device integrated with a small angle light scattering (SALS) apparatus (Billiar and Sacks 1997). Each sample was loaded to equibiaxial strain of 10% by stretching in each of the following stretch patterns: 1) first in the preferred fiber direction, then in the cross-preferred direction, 2) first in the cross-preferred direction, then in the preferred direction, and 3) simultaneously in both directions equally. The collagen fiber distributions for the equibiaxial strain states were found to be relatively insensitive to the stretch pattern. Further, an affine transformation calculation based on Lanir (1979) and Billiar and Sacks (1997) was used to predict the strip biaxial and equibiaxial collagen fiber distributions and it was found that while the tissue generally followed the trends expected for an affine material, the intensity levels were not predictive.