Mechanical evaluation and design of a multilayered collagenous repair biomaterial

One method of fabricating implantable biomaterials is to utilize biological ly derived, chemically modified tissues to form constructs that are both bi ocompatible and remodelable. Rigorous mechanical characterization is a nece ssary component in material evaluation to ensure that the constructs will w ithstand in vivo loading. In this study we performed an in-depth biaxial me chanical and quantitative structural analysis of GraftPatch (GP), a biomate rial constructed by assembling chemically treated layers of porcine small i ntestinal submucosa (SIS). The mechanical behavior of GP was compared to bo th native SIS and to glutaraldehyde-treated bovine pericardium (GLBP) as a reference biomaterial. Under biaxial loading, GP was found to be stiffer th an native SIS and mechanically anisotropic, with the preferred fiber direct ion demonstrating greater stiffness. Quantitative structural analysis using small-angle light scattering indicated a uniform fiber structure similar t o GLBP and SIS. To enable test-protocol-independent quantitative comparison s, the biaxial mechanical data were fit to an orthotropic constitutive mode l, which indicated a similar degree of mechanical anisotropy between the th ree groups. We also demonstrate how the constitutive model can be used to d esign layered biocomposite materials that can undergo large deformations. ( C) 2000 John Wiley & Sons, Inc.