In vivo and in vitro characterization of poly(styrene‐b‐isobutylene‐b‐styrene) copolymer stent coatings for biostability, vascular compatibility and mechanical integrity

Abstract The TAXUS® Express ²™Paclitaxel Eluting Coronary Stent System employs a coating consisting of the thermoplastic elastomer, poly(styrene‐b‐isobutylene‐b‐styrene; SIBS), selected for its drug‐eluting characteristics, vascular compatibility, mechanical properties, and biostability. This study was conducted to evaluate the impact of different SIBS (17−51 mole % styrene) compositions on mechanical properties, chemical stability, and vascular compatibility. Mechanical property (stress−strain measurements) and stability studies were conducted on polymer films with five different styrene contents (17, 24, 32, 39, and 51 mole %). The ultimate tensile strength did not change significantly with composition, but the elongation at break decreased with increased styrene content. A pulsatile fatigue test further confirmed the mechanical stability of SIBS up to 39 mole % styrene. The vascular compatibility of five different SIBS compositions was assessed using SIBS‐only coated stents, in the coronary and carotid arteries in a porcine model study. The stability of the vessel wall, rate/degree of endothelialization, inflammation, and thrombus at timepoints from 30 to 180 days were evaluated. The results confirm vascular compatibility over the range of 17−51 mole % styrene. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2010