A novel small animal model for biocompatibility assessment of polymeric materials for use in prosthetic heart valves.

A composite polymeric material, poly(styrene-block-isobutylene-block-styrene) (SIBS) with an embedded reinforcement polyethylene terephthalate (PET) fabric, is undergoing investigation for potential use in a novel heart valve. The purpose of this study was to develop and implement a small animal model to assess the biocompatibility of composite samples in a cardiovascular tissue and blood-contacting environment. Composite samples were manufactured using dip coating and solvent casting with two coating thicknesses (25 and 50 microm). A novel rat abdominal aorta model was developed to test the dip-coated samples in a similar pulsatile flow condition to its intended use, and both dip-coated and solvent-cast samples were tested using a rat subcutaneous model. Tissue response, defined by degree of cellular infiltration and encapsulation, was minimized when a smooth coating of SIBS shielded the PET fabric from exposure to blood and tissue, and the degree of tissue response was directly correlated with the degree of surface roughness. Surface modification using phospholipid further reduces the tissue response. We have demonstrated the applicability of using a novel rat abdominal aorta model for biocompatibility assessment of polymeric materials that will be used in cardiovascular implants. For the purpose of this study, our results indicate that solvent casting with a 25-microm SIBS coating thickness will provide optimal biocompatibility for the SIBS valve.