POLYURETHANE-COATED, SELF-EXPANDABLE BILIARY STENT - AN EXPERIMENTAL-STUDY

Rationale and Objectives. We describe a self-expanding metallic biliar y Gianturco-Rosch stent coated with polymeric material. The coating na s designed to prevent the growth of neoplastic and reactive tissue wit hin the biliary ducts. Methods. The stents were coated with a solvent- casting technique. which consists of dissolving polyurethane (polyethe r urethane or polycarbonate urethane) pellets in a solvent (dimethylac etamide). dipping the stent in the solution, and completely evaporatin g the solvent, In vitro mechanical characterization of the stent a-as performed to determine the adhesion of the coating to the metallic cag e, the best introducer caliber for implantation of the device, and the relationship between the stent's diameter and radial stress. Results. Reports in the literature on the biostability of polycarbonate uretha ne compared with polyether urethane prompted us to use the former mate rial to coal the stents. The solvent technique gives a smooth internal surface of the stent wall, leaving in relief the coated structure of the stent on the external surface. The functional tests demonstrated t hat the coating did not compromise the original characteristics of the stent in terms of self-expandability, axial flexibility? and increase d radial rigidity of the device, Conclusion. Functional tests verified coating stability and device handling,which are the first steps towar d in vivo experimentation.